Abstract:
A process for the preparation of vinyl, alkynyl or aryl aldehydes or vinyl, alkynyl or aryl ketones by reaction of vinyl-, alkynyl- or aryl- methanols with the aid of a mediator and an oxidant, wherein the mediator is selected from the group of the aliphatic, cycloaliphatic, heterocyclic or aromatic NO or NOH containing compounds.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a process for the preparation of aldehydes and ketones. 
     2. The Prior Art 
     Aldehydes and ketones are widely used in organic chemistry. For example, they are important precursors in the synthesis of heterocycles, perfumes and dyestuffs. 
     A variety of processes are known for the preparation of aldehydes and ketones. For example, the formyl and the acyl group are successfully introduced directly into aromatic systems via electrophilic substitution reactions, which, however, are limited by the substitution rules. Aromatic ketones can also be synthesized via organometallic reactions. A disadvantage includes the necessity of using an anhydrous reaction medium. Another disadvantage is the use of toxic chemicals such as phosphorus oxychloride, carbon monoxide, zinc cyanide, mercury organyls and cadmium organyls. 
     Aldehydes and ketones are frequently prepared via oxidation reactions starting from the corresponding alcohols. An overview is given in the literature reviewed in Houben-Weyl-Muller, Vol. 7/2a, p. 699 et seq. and Vol. E3, p. 265 et seq., 1983. They are most frequently carried out in nonaqueous medium and often require expensive and/or toxic reagents which are unsuitable for larger-scale syntheses because they are difficult to handle. Aromatic aldehydes and ketones can be prepared from hydroxyalkyl aromatics using stable nitroxide radicals, for example TEMPO, and an oxidant (A. E. J. de Nooy, A. C. Besemer and H. V. Bekkum, Synthesis 1996, 1153). The oxidizing agent here is an oxoammonium ion, which is formed by adding an oxidant. A disadvantage of this method is, on the one hand, the high price of reagents required. A further disadvantage is that a nonaqueous medium is required since otherwise the aldehyde formed oxidizes further to give the carboxylic acid. The formation of aromatic aldehydes from the corresponding hydroxymethyl-aromatics in the presence of the enzyme laccase and ABTS (2,2&#39;-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) was observed by Potthast (Potthast et al., J. Molec. Catal. A: Chemical 1996, 108, and Synth. Commun. 1996, 26, 315). The high price of ABTS, however, excludes applicability of the method on an industrial scale. A further disadvantage is the low selectivity in the presence of methyl and hydroxymethyl groups. 
     There is therefore a demand for an inexpensive and selective process which satisfies the ever increasing demands in industry and which allows even sensitive aldehydes and ketones to be synthesized on a large scale. 
     SUMMARY OF THE INVENTION 
     The invention relates to a process for the preparation of vinyl, alkynyl, aryl or heteroaryl aldehydes or vinyl, alkynyl, aryl or heteroaryl ketones from vinyl-, alkynyl-, aryl- or heteroarylmethanols with the aid of a mediator and an oxidant, wherein the mediator is selected from the group of the aliphatic, cycloaliphatic, heterocyclic or aromatic NO, NOH or ##STR1## containing compounds. 
     The vinyl, alkynyl, aryl or heteroaryl aldehydes or vinyl, alkynyl, aryl or heteroaryl ketones are preferably compounds of the formula 1, and the vinyl-, alkynyl-, aryl- or heteroarylmethanols are preferably compounds of the formula 2 ##STR2## where Y 1  and Y 2  can be identical or different and are radicals having up to 20 C atoms and up to 6 rings and at least one of the radicals Y 1  or Y 2  is vinyl, alkynyl, aryl or heteroaryl, and Y 1  and Y 2  may also be part of a ring or of a ring system. 
     Y 1  is preferably an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, it being possible for the aromatic or heteroaromatic radical Y 1  to be mono- to hexasubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear, branched or cyclic C 1  -C 12  -alkyl radical, it being possible for adjacent alkyl groups to form a 5-, 6- or 7-membered ring via a methylene group, or a linear or branched C 1  -C 12  -oxyalkyl or thioalkyl radical, it being possible for adjacent substituents to form a 5-, 6- or 7-membered ring via a methylene group, a H 2  N- or a linear or branched C 1  -C 12  -N-alkylamino, a linear or branched C 1  -C 12  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH--, or a linear, branched or cyclic C 1  -C 12  -OCO--, C 1  -C 12  -COO--, C 1  -C 12  -CO--, C 1  -C 12  -NHCO--, C 1  -C 12  -NHCONH--, (C 1  -C 12 ) 2  NCO--, C 1  -C 12  -CONH--, or a linear or branched C 1  -C 12  -OSO 2  --, C 1  -C 12  -NH--SO 2  --, or (C 1  -C 12 ) 2  N--SO 2  -- group, or a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH-phenyl-O--CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group whose phenyl radicals can be mono- to pentasubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear, branched or cyclic C 1  -C 12  -alkyl radical, it being possible for adjacent alkyl groups to form a 5-, 6- or 7-membered ring via a methylene group, or of a linear or branched C 1  -C 12  -oxyalkyl or thioalkyl radical, it being possible for adjacent substituents to form a 5-, 6- or 7-membered ring via a methylene group, a H 2  N-- or a linear or branched C 1  -C 12  -N-alkylamino, a linear or branched C 1  -C 12  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH--, or a linear, branched or cyclic C 1  C 12  -OCO--, C 1  -C 12  -COO--, C 1  -C 12  -CO--, C 1  -C 12  -NHCO--, C 1  -C 12  -NHCONH--, (C 1  -C 12 ) 2  NCO--, C 1  -C 12  -CONH--, or of a linear or branched C 1  -C 12  -OSO 2  --, C 1  -C 12  -NH--SO 2  -- or (C 1  -C 12 ) 2  N--SO 2  -- group, or of a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH--, phenyl-O--CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group or an optionally mono- to trisubstituted vinyl radical, or optionally substituted ethynyl radical, in which the substituents can be identical or different and can be hydrogen, linear, branched or cyclic C 1  -C 12  -alkyl radical where one or more methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 12  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, or in which the vinyl group forms part of a ring or ring system. 
     Y 2  is preferably hydrogen, linear, branched or cyclic C 1  -C 12  -alkyl radical here one or more methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 12  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or anthraquinonyl radical, or an optionally mono- to trisubstituted vinyl radical, or optionally substituted ethynyl radical, in which the substituents can be identical or different and can be hydrogen, linear, branched or cyclic C 1  -C 12  -alkyl radical where one or more methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 12  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O. S or N atoms, or an anthraquinonyl radical, or in which the vinyl group forms part of a ring or ring system. 
     Equally preferred are compounds in which the radicals Y 1  and Y 2  are linked via a methylene group or an ether group or via an amino group which is optionally substituted by a linear, branched or cyclic C 1  -C 12  -alkyl radical. 
     Especially preferably, Y 1  is a 5-, 6- or 7-membered aromatic or heteroaromatic ring which can be fused to one or two further aromatic rings and where one to four C atoms can be replaced by O, S or N atoms, or an anthraquinonyl radical, it being possible for Y 1  to be mono- to tetrasubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear, branched or cyclic C 1  -C 6  -alkyl radical, it being possible for adjacent alkyl groups to form a 5- or 6-membered ring via a methylene group, or a linear or branched C 1  -C 6  -oxyalkyl or -thioalkyl radical, it being possible for adjacent substituents to form a 5- or 6-membered ring via a methylene group, of a H 2  N--, or a linear or branched C 1  -C 6  -N-alkylamino, a linear or branched C 1  -C 3  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH-- radical, or a linear, branched or cyclic C 1  -C 6  -OCO--, C 1  -C 6  -COO--, C 1  -C 6  -CO--C 1-C   6  -NHCO--, C 1  -C 6  -NHCONH--, (C 1  -C 6 ) 2  NCO--, C 1  -C 6  -CONH--, or of a linear or branched C 1  -C 6  -OSO 2  --, C 1  -C 6  -NH-SO 2  -- or (C 1  -C 3 ) 2  N--SO 2  -- group, or of a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH--, phenyl-O-CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group, it being possible for the phenyl radicals to be mono- to trisubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear, branched or cyclic C 1  -C 6  -alkyl radical, it being possible for adjacent alkyl groups to form a 5- or 6-membered ring via a methylene group, or a linear or branched C 1  -C 6  -oxyalkyl or -thioalkyl radical, it being possible for adjacent substituents to form a 5- or 6-membered ring via a methylene group, of a H 2  N--, or a linear or branched C 1  -C 6  -N-alkylamino, a linear or branched C 1  -C 3  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH-- radical, or a linear, branched or cyclic C 1  -C 6  -OCO--, C 1  -C 6  -COO--, C 1  -C 6  -CO--, C 1  -C 6  -NHCO--, C 1  -C 6  -NHCONH--, (C 1  -C 6 ) 2  NCO--, C 1  -C 6  -CONH--, or of a linear or branched C 1  -C 6  -OSO 2  --, C 1  -C 6  -NH--SO 2  -- or (C 1  -C 3 ) 2  N--SO 2  -- group, or of a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH--, phenyl-O--CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group, or is an optionally mono- to trisubstituted vinyl radical, or an optionally substituted ethynyl radical, it being possible for the substituents to be identical or different and to have the meaning of hydrogen, a linear, branched, or cyclic C 1  - 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical. 
     Especially preferably, Y 2  is hydrogen, linear, branched or cyclic C 1  -C 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 atoms whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, or an optionally mono- to trisubstituted vinyl radical, or an optionally substituted ethynyl radical, it being possible for the substituents to be identical or different and to have the meaning of hydrogen, a linear, branched, or cyclic C 1  -C 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms whose ring members can be replaced by O, S or N atoms. 
     Equally especially preferred are compounds where the radicals Y 1  and Y 2  are linked via a methylene group or an ether group or via an amino group which is optionally substituted by a linear, branched or cyclic C 1  -C 6  -alkyl radical. 
     Very especially preferably, Y 1  is phenyl, naphthyl, anthryl, phenanthryl, azulenyl, anthraquinonyl, furyl, pyrrolyl, thienyl, benzofuranyl, isobenzofuranyl, benzothiyl, isobenzothienyl, indolyl, isoindolyl, indolizinyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, indazolyl, carbazolyl, benzotriazolyl, purinyl, pyridyl, pyridazinyl, pyrimidyl, pyrazinyl, quinolinyl, isoquinolinyl quinoxalinyl, quinazolinyl, cinnolinyl, phenanthridinyl, acridinyl, 1,10-phenanthrolinyl, phenazinyl, phenothiazinyl, phenoxazinyl radical, it being possible for Y 1  to be mono- to trisubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear C 1  -C 6  -alkyl radical, it being possible for adjacent alkyl groups to form a 5- or 6-membered ring via a methylene group, or of a linear C 1  -C 6  -oxyalkyl radical, it being possible for adjacent substituents to form a 5- or 6-membered ring via a methylene group, a H 2  N--, or a linear C 1  -C 6  -N-alkylamino, a linear C 1  -C 3  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH-- radical, or a linear C 1  -C 4  -OCO--, C 1  -C 4  -COO--, C 1  -C 4  -CO--, C 1  -C 4  -NHCO--, (C 1  -C 4 ) 2  NCO--, C 1  -C 4  -CONH--, C 1  -C 4  -NHCONH--, or C 1  -C 4  -OSO 2  --, C 1  -C 4  -NH--SO 2  -- or (C 1  -C 3 ) 2  N--SO 2  -- group, or of a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH--, phenyl-O--CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group, it being possible for the phenyl radicals to be mono- to trisubstituted, it being possible for the substituents to be identical or different and to have the meaning of OH, a linear C 1  -C 6  alkyl radical, it being possible for adjacent alkyl groups to form a 5- or 6-membered ring via a methylene group, or of a linear C 1  -C 6  -oxyalkyl radical, it being possible for adjacent substituents to form a 5- or 6-membered ring via a methylene group, a H 2  N--, or a linear C 1  -C 6  -N-alkylamino, a linear C 1  -C 3  -N,N-dialkylamino group, NC--, O 2  N--, halogen, HOOC--, HO 3  S--, OHC--, H 2  N--COO--, H 2  N--CO--, H 2  N--CO--NH--, or a linear C 1  -C 4  -OCO--, C 1  -C 4  -COO--, C 1  -C 4  -CO--, C 1  -C 4  -NHCO--, (C 1  -C 4 ) 2  NCO--, C 1  -C 4  -CONH--, C 1  -C 4  -NHCONH--, or C 1  -C 4  -OSO 2  --, C 1  -C 4  -NH--SO 2  -- or (C 1  -C 3 ) 2  N--SO 2  -- group, or of a phenyl, diphenylmethyl, phenyl-CH═CH--, phenyl-N═N--, phenyl-N═CH--, phenyl-CH═N--, phenoxy, phenyl-NH,phenyl-O--CO--, phenyl-CO--, phenyl-NHCO--, phenyl-CONH--, phenyl-NHCONH--, phenyl-OSO 2  -- or phenyl-NH--SO 2  -- group or Y 1  is an optionally mono- to trisubstituted vinyl radical, or optionally substituted ethynyl radical, in which the substituents can be identical or different and have the meaning of hydrogen, linear C 1  -C 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, or in which the vinyl group forms part of a 5- or 6-membered ring or of a ring system, and Y 2  is hydrogen, a linear C 1  -C 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, or an optionally mono- to trisubstituted vinyl radical, or optionally substituted ethynyl radical, in which the substituents can be identical or different and have the meaning of hydrogen, linear C 1  -C 6  -alkyl radical where one or two methylene groups can be replaced individually by --CHOH, --CO, O--, S--, NH-- or by a linear or branched C 1  -C 6  -N-alkylamine radical, or an aromatic or heteroaromatic ring or ring system having up to 6 rings and up to 20 C atoms, whose ring members can be replaced by O, S or N atoms, or an anthraquinonyl radical, or in which the vinyl group forms part of a 5- or 6-membered ring or of a ring system. 
     The mediator used is preferably at least one compound selected from the group of the aliphatic, cycloaliphatic, heterocyclic or aromatic compounds which contains at least one N-hydroxyl, oxime, nitroso, nitroxide or N-oxide function. 
     Examples of such compounds are the compounds of the formula I, II, III or IV, mentioned below, the compounds of the formulae II, III and IV being preferred and the compounds of the formulae III and IV being especially preferred. 
     Compounds of the general formula I are: ##STR3## where X is one of the following groups: (--N═N--), (--N═CR 4  --) p , (--CR 4  ═N--) p , (--CR 5  ═CR 6 ) p  ##STR4## and p equals 1 or 2, it being possible for the radicals R 1  to R 6  to be identical or different and independently of one another to represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and the salts and esters thereof, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, sulfono, esters and salts thereof, sulfamoyl, carbamoyl, phospho, phosphono, phosphonooxy and their salts and esters, and it furthermore being possible for the amino, carbamoyl and sulfamoyl groups of the radicals R 1  to R 6  to be unsubstituted or to be mono- or disubstituted by hydroxyl, C 1  -C 3  -alkyl or C 1  -C 3  -alkoxy, and it being possible for the radicals R 2  and R 3  to form a joint group --A--, where --A-- represents one of the following groups: 
     (--CR 7  ═CR 8  --CR 9  ═CR 10  --) or (--CR 10  ═CR 9  --CR 8  ═CR 7  --). 
     The radicals R 7  to R 10  can be identical or different and independently of one another can represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and the salts and esters thereof, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl sulfono, esters and salts thereof, sulfamoyl, carbamoyl, phospho, phosphono, phosphonooxy and their salts and esters, and it furthermore being possible for the amino, carbamoyl and sulfamoyl groups of the radicals R 7  to R 10  to be unsubstituted or to be mono- or disubstituted by hydroxyl, C 1  -C 3  -alkyl or C 1  -C 3  -alkoxy, and it being possible for the C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl or aryl groups of the radicals R 7  to R 10  to be unsubstituted or furthermore to be mono- or polysubstituted by the radical R 11 , and it being possible for the radical R 11  to represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl, and their esters and salts, and it being possible for the carbamoyl, sulfamoyl and amino groups of the radical R 11  to be unsubstituted or furthermore to be mono- or disubstituted by the radical R 12 , and it being possible for the radical R 12  to represent one of the following groups: hydrogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl or aryl. 
     Examples of the abovementioned compounds are: 
     1-hydroxy-1,2,3-triazole-4,5-dicarboxylic acid 
     1-phenyl-1H-1,2,3-triazole-3-oxide 
     5-chloro-1-phenyl-1H-1,2,3-triazole-3-oxide 
     5-methyl-1-phenyl-1H-1,2,3-triazole-3-oxide 
     4-(2,2-dimethylpropanoyl)-1-hydroxy-1H-1,2,3-triazole 
     4-hydroxy-2-phenyl-2H-1,2,3-triazole-1-oxide 
     2,4,5-triphenyl-2H-1,2,3-triazole-1-oxide 
     1-benzyl-1H-1,2,3-triazole-3-oxide 
     1-benzyl-4-chloro-1H-1,2,3-triazole-3-oxide 
     1-benzyl-4-bromo-1H-1,2,3-triazole-3-oxide 
     1-benzyl-4-methoxy-1H-1,2,3-triazole-3-oxide 
     Compounds of the general formula II are: ##STR5## where X is one of the following groups: (--N═N--), (--N═CR--) p , (--CR 4  ═N--) p , (--CR 5  ═CR 6 ) p  ##STR6## and p equals 1 or 2. 
     The radicals R 1  and R 4  to R 10  can be identical or different and independently of one another can represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and the salts and esters thereof, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl, sulfono, esters and salts thereof, sulfamoyl, carbamoyl, phospho, phosphono, phosphonooxy and their salts and esters, and it furthermore being possible for the amino, carbamoyl and sulfamoyl groups of the radicals R 1  and R 4  to R 10  to be unsubstituted or to be mono- or disubstituted by hydroxyl, C 1  -C 3  -alkyl or C 1  -C 3  -alkoxy, and it being possible for the C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl and aryl-C 1  -C 6  -alkyl groups of the radicals R 1  and R 4  to R 10  to be unsubstituted or furthermore to be mono- or polysubstituted by the radical R 12 , and it being possible for the radical R 12  to represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl, sulfono, sulfeno, sulfino and their esters and salts, and it being possible for the carbamoyl, sulfamoyl and amino groups of the radical R 12  to be unsubstituted or furthermore to be mono- or disubstituted by the radical R 13 , and it being possible for the radical R 13  to represent one of the following groups: hydrogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl. 
     Examples of the abovementioned compounds are: 
     1-hydroxybenzimidazoles 
     1-hydroxybenzimidazole-2-carboxylic acid 
     1-hydroxybenzimidazole 
     2-methyl-1-hydroxybenzimidazole 
     2-phenyl-1-hydroxybenzimidazole 
     1-hydroxyindoles 
     2-phenyl-1-hydroxyindole 
     Substances of the general formula III are: ##STR7## where X is one of the following groups: (--N═N--), (--N═CR 4  --) m , (--CR 4  ═N--) m , (--CR 5  ═CR 6  --) m  ##STR8## and m equals 1 or 2. 
     What has been said above for the radicals R 7  to R 10  and R 4  to R 6  also applies here. 
     R 14  can be: hydrogen, C 1  -C 10  -alkyl or C 1  -C 10  -alkyl-carbonyl whose C 1  -C 10  -alkyl and C 1  -C 10  -alkylcarbonyl can be unsubstituted or mono- or polysubstituted by a radical R 15 , it being possible for R 15  to represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and salts and esters thereof, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, sulfono, their esters and salts, sulfamoyl, carbamoyl, phospho, phosphono, phosphonooxy and their salts and esters, it being possible for the amino, carbamoyl and sulfamoyl groups of the radical R 15  furthermore to be unsubstituted or mono- or disubstituted by hydroxyl, C 1  -C 3  -alkyl or C 1  -C 3  -alkoxy. 
     Particularly preferred among the substances of the formula III are derivatives of 1-hydroxybenzotriazole and of the tautomeric benzotriazole 1-oxide, and their esters and salts (compounds of the formula IV) ##STR9## 
     The radicals R 7  to R 10  can be identical or different and independently of one another represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and salts and esters thereof, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, sulfono, esters and salts thereof, sulfamoyl, carbamoyl, phospho, phosphono, phosphonooxy and their salts and esters, it furthermore being possible for the amino, carbamoyl and sulfamoyl groups of the radicals R 7  to R 10  to be unsubstituted or to be mono- or disubstituted by hydroxyl, C 1  -C 3  -alkyl or C 1  -C 3  -alkoxy and it being possible for the C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl and aryl groups of the radicals R 7  to R 10  to be unsubstituted or furthermore mono- or polysubstituted by the radical R 16 , and it being possible for the radical R 16  to represent one of the following groups: hydrogen, halogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl, sulfono, sulfeno, sulfino and also their esters and salts, and it being possible for the carbamoyl, sulfamoyl and amino groups of the radical R 16  to be unsubstituted or furthermore mono- or disubstituted by the radical R 17 , and it being possible for the radical R 17  to represent one of the following groups: hydrogen, hydroxyl, formyl, carboxyl and their salts and esters, amino, nitro, C 1  -C 12  -alkyl, C 1  -C 6  -alkyloxy, carbonyl-C 1  -C 6  -alkyl, phenyl, aryl. 
     Examples of the abovementioned compounds are: 
     1H-hydroxybenzotriazoles 
     1-hydroxybenzotriazole 
     1-hydroxybenzotriazole, sodium salt. 
     1-hydroxybenzotriazole, potassium salt 
     1-hydroxybenzotriazole, lithium salt 
     1-hydroxybenzotriazole, ammonium salt 
     1-hydroxybenzotriazole, calcium salt 
     1-hydroxybenzotriazole, magnesium salt 
     1-hydroxybenzotriazole-6-sulfonic acid 
     1-hydroxybenzotriazole-6-sulfonic acid, monosodium salt 
     1-hydroxybenzotriazole-6-carboxylic acid 
     1-hydroxybenzotriazole-6-N-phenylcarboxamide 
     5-ethoxy-6-nitro-1-hydroxybenzotriazole 
     4-ethyl-7-methyl-6-nitro-1-hydroxybenzotriazole 
     2,3-bis(4-ethoxyphenyl)-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     2,3-bis(2-bromo-4-methylphenyl)-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     2,3-bis(4-bromophenyl)-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     2,3-bis(4-carboxyphenyl)-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     4,6-bis(trifluoromethyl)-1-hydroxybenzotriazole 
     5-bromo-1-hydroxybenzotriazole 
     6-bromo-1-hydroxybenzotriazole 
     4-bromo-7-methyl-1-hydroxybenzotriazole 
     5-bromo-7-methyl-6-nitro-1-hydroxybenzotriazole 
     4-bromo-6-nitro-1-hydroxybenzotriazole 
     6-bromo-4-nitro-1-hydroxybenzotriazole 
     4-chloro-1-hydroxybenzotriazole 
     5-chloro-1-hydroxybenzotriazole 
     6-chloro-1-hydroxybenzotriazole 
     6-chloro-5-isopropyl-1-hydroxybenzotriazole 
     5-chloro-6-methyl-1-hydroxybenzotriazole 
     6-chloro-5-methyl-1-hydroxybenzotriazole 
     4-chloro-7-methyl-6-nitro-1-hydroxybenzotriazole 
     4-chloro-5-methyl-1-hydroxybenzotriazole 
     5-chloro-4-methyl-1-hydroxybenzotriazole 
     4-chloro-6-nitro-1-hydroxybenzotriazole 
     6-chloro-4-nitro-1-hydroxybenzotriazole 
     7-chloro-1-hydroxybenzotriazole 
     6-diacetylamino-1-hydroxybenzotriazole 
     2,3-dibenzyl-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     4,6-dibrono-1-hydroxybenzotriazole 
     4,6-dichloro-1-hydroxybenzotriazole 
     5,6-dichloro-1-hydroxybenzotriazole 
     4,5-dichloro-1-hydroxybenzotriazole 
     4,7-dichloro-1-hydroxybenzotriazole 
     5,7-dichloro-6-nitro-1-hydroxybenzotriazole 
     5,6-dimethoxy-1-hydroxybenzotriazole 
     2,3-di-[2]naphthyl-4,6-dinitro-2,3-dihydro-1-hydroxybenzotriazole 
     4,6-dinitro-1-hydroxybenzotriazole 
     4,6-dinitro-2,3-diphenyl-2,3-dihydro-1-hydroxybenzotriazole 
     4,6-dinitro-2,3-di-p-tolyl-2,3-dihydro-1-hydroxybenzotriazole 
     5-hydrazino-7-methyl-4-nitro-1-hydroxybenzotriazole 
     5,6-dimethyl-1-hydroxybenzotriazole 
     4-methyl-1-hydroxybenzotriazole 
     5-methyl-1-hydroxybenzotriazole 
     6-methyl-1-hydroxybenzotriazole 
     5-(1-methylethyl)-1-hydroxybenzotriazole 
     4-methyl-6-nitro-1-hydroxybenzotriazole 
     6-methyl-4-nitro-1-hydroxybenzotriazole 
     5-methoxy-1-hydroxybenzotriazole 
     6-methoxy-1-hydroxybenzotriazole 
     7-methyl-6-nitro-1-hydroxybenzotriazole 
     4-nitro-1-hydroxybenzotriazole 
     6-nitro-1-hydroxybenzotriazole 
     6-nitro-4-phenyl-1-hydroxybenzotriazole 
     5-phenylmethyl-1-hydroxybenzotriazole 
     4-trifluoromethyl-1-hydroxybenzotriazole 
     5-trifluoromethyl-1-hydroxybenzotriazole 
     6-trifluoromethyl-1-hydroxybenzotriazole 
     4,5,6,7-tetrachloro-1-hydroxybenzotriazole 
     4,5,6,7-tetrafluoro-1-hydroxybenzotriazole 
     6-tetrafluoroethyl-1-hydroxybenzotriazole 
     4,5,6-trichloro-1-hydroxybenzotriazole 
     4,6,7-trichloro-1-hydroxybenzotriazole 
     6-sulfamido-1-hydroxybenzotriazole 
     6-N,N-diethylsulfamido-1-hydroxybenzotriazole 
     6-N-methylsulfamido-1-hydroxybenzotriazole 
     6-(1H-1,2,4-triazol-1-ylmethyl)-1-hydroxybenzotriazole 
     6-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl)-1-hydroxybenzotriazole 
     6-(phenyl-1H-1,2,4-triazol-1-ylmethyl)-1-hydroxybenzotriazole 
     6-[(5-methyl-1H-imidazo-1-yl)phenylmethyl]-1-hydroxybenzotriazole 
     6-[(4-methyl-1H-imidazo-1-yl)phenylmethyl]-1-hydroxybenzotriazole 
     6-[(2-methyl-1H-imidazo-1-yl)phenylmethyl]-1-hydroxybenzotriazole 
     6-(1H-imidazol-1-ylphenylmethyl)-1-hydroxybenzotriazole 
     5-(1H-imidazol-1-ylphenylmethyl)-1-hydroxybenzotriazole 
     6-[1-(1H-imidazol-1-yl)ethyl]-1-hydroxybenzotriazole monohydrochloride 
     3H-benzotriazole 1-oxides 
     3H-benzotriazole 1-oxide 
     6-acetyl-3H-benzotriazole 1-oxide 
     5-ethoxy-6-nitro-3H-benzotriazole 1-oxide 
     4-ethyl-7-methyl-6-nitro-3H-benzotriazole 1-oxide 
     6-amino-3,5-dimethyl-3H-benzotriazole 1-oxide 
     6-amino-3-methyl-3H-benzotriazole 1-oxide 
     5-bromo-3H-benzotriazole 1-oxide 
     6-bromo-3H-benzotriazole 1-oxide 
     4-bromo-7-methyl-3H-benzotriazole 1-oxide 
     5-bromo-4-chloro-6-nitro-3H-benzotriazole 1-oxide 
     4-bromo-6-nitro-3H-benzotriazole 1-oxide 
     6-bromo-4-nitro-3H-benzotriazole 1-oxide 
     5-chloro-3H-benzotriazole 1-oxide 
     6-chloro-3H-benzotriazole 1-oxide 
     4-chloro-6-nitro-3H-benzotriazole 1-oxide 
     4,6-dibromo-3H-benzotriazole 1-oxide 
     4,6-dibromo-3-methyl-3H-benzotriazole 1-oxide 
     4,6-dichloro-3H-benzotriazole 1-oxide 
     4,7-dichloro-3H-benzotriazole 1-oxide 
     5,6-dichloro-3H-benzotriazole 1-oxide 
     3,4,6-dichloro-3-methyl-3H-benzotriazole 1-oxide 
     5,7-dichloro-6-nitro-3H-benzotriazole 1-oxide 
     3,6-dimethyl-6-nitro-3H-benzotriazole 1-oxide 
     3,5-dimethyl-6-nitro-3H-benzotriazole 1-oxide 
     3-methyl-3H-benzotriazole 1-oxide 
     5-methyl -3H-benzotriazole 1-oxide 
     6-methyl-3H-benzotriazole 1-oxide 
     6-methyl-4nitro3H-benzotriazole 1-oxide 
     7-methyl-6-nitro-3H-benzotriazole 1-oxide 
     5-chloro-6-nitro-3H-benzotriazole 1-oxide 
     2H-benzotriazole 1-oxides 
     2-(4-acetoxyphenyl)-2H-benzotriazole 1-oxide 
     6-acetylamino-2-phenyl-2H-benzotriazole 1-oxide 
     2-(4-ethylphenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(3-aminophenyl)-2H-benzotriazole 1-oxide 
     2-(4-aminophenyl)-2H-benzotriazole 1-oxide 
     6-amino-2-phenyl-2H-benzotriazole 1-oxide 
     5-bromo-4-chloro-6-nitro-2-phenyl-2H-benzotriazole 1-oxide 
     2-(4-bromophenyl)-2H-benzotriazole 1-oxide 
     5-bromo-2-phenyl-2H-benzotriazole 1-oxide 
     6-bromo-2-phenyl-2H-benzotriazole 1-oxide 
     2-(4-bromophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(4-bromophenyl)-6-nitro-2H-benzotriazole 1-oxide 
     5-chloro-2-(2-chlorophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(3-chlorophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(2-chorophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(3-chlorophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(2,4-dibromophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(2,5-diethylphenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-(4-nitrophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-6-nitro-2-phenyl-2H-benzotriazole 1-oxide 
     2-[4-(4-chloro-3-nitrophenylazo)-3-nitrophenyl]-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(3-chloro-4-nitrophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(4-chloro-3-nitrophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     4-chloro-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     5-chloro-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-chloro-4-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     2-(2-chlorophenyl)-2H-benzotriazole 1-oxide 
     2-(3-chlorophenyl)-2H-benzotriazole 1-oxide 
     2-(4-chlorophenyl)-2H-benzotriazole 1-oxide 
     5-chloro-2-phenyl-2H-benzotriazole 1-oxide 
     2-[4-(4-chlorophenylazo)-3-nitrophenyl]-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(2-chlorophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(3-chlorophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(4-chlorophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-{4-[N&#39;-(3-chlorophenyl)hydrazino]-3-nitrophenyl}-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-{4-[N&#39;-(4-chlorophenyl)hydrazino]-3-nitrophenyl}-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(2-chlorophenyl)-6-methyl-2H-benzotriazole 1-oxide 
     2-(3-chlorophenyl)-6-methyl-2H-benzotriazole 1-oxide 
     2-(4-chlorophenyl)-6-methyl-2H-benzotriazole 1-oxide 
     2-(3-chlorophenyl)-6-nitro-2H-benzotriazole 1-oxide 
     2-(4-chlorophenyl)-6-nitro-2H-benzotriazole 1-oxide 
     2-(4-chlorophenyl)-6-picrylazo-2H-benzotriazole 1-oxide 
     5-chloro-2-(2,4,5-trimethylphenyl)-2H-benzotriazole 1-oxide 
     4,5-dibromo-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     4,5-dichloro-6-nitro-2-phenyl-2H-benzotriazole 1-oxide 
     4,5-dichloro-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     4,7-dichloro-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     4,7-dimethyl-6-nitro-2-phenyl-2H-benzotriazole 1-oxide 
     2-(2,4-dimethylphenyl)-4,6-dinitro-benzotriazole 1-oxide 
     2-(2,5-dimethylphenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(2,4-dimethylphenyl)-6-nitro-2H-benzotriazole 1-oxide 
     2-(2,5-dimethylphenyl)-6-nitro-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-[3-nitro-4-(N&#39;-phenylhydrazino)phenyl]-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-[4-nitro-4-(N&#39;-phenylhydrazino)phenyl]-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-phenyl-2H-benzotriazole 1-oxide 
     2-(2,4-dinitrophenyl)-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-(2,4-dinitrophenyl)-6-nitro-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-o-tolyl-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     4,6-dinitro-2-(2,4,5-trimethylphenyl)-2H-benzotriazole 1-oxide 
     2-(4-methoxyphenyl)-2H-benzotriazole 1-oxide 
     2-(4-methoxyphenyl)-6-methyl-2H-benzotriazole 1-oxide 
     5-methyl-6-nitro-2-m-tolyl-2H-benzotriazole 1-oxide 
     5-methyl-6-nitro-2-o-tolyl-2H-benzotriazole 1-oxide 
     5-methyl-6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-methyl-4-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-methyl-2-phenyl-2H-benzotriazole 1-oxide 
     4-methyl-2-m-tolyl-2H-benzotriazole 1-oxide 
     4-methyl-2-o -tolyl-2H-benzotriazole 1-oxide 
     4-methyl-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-methyl-2-m-tolyl-2H-benzotriazole 1-oxide 
     6-methyl-2-o-tolyl-2H-benzotriazole 1-oxide 
     6-methyl-2-p-tolyl-2H-benzotriazole 1-oxide 
     2-[1]naphthyl-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-[2]naphthyl-4,6-dinitro-2H-benzotriazole 1-oxide 
     2-[1]naphthyl-6-nitro-2H-benzotriazole 1-oxide 
     2-[2]naphthyl-6-nitro-2H-benzotriazole 1-oxide 
     2-(3-nitrophenyl)-2H-benzotriazole 1-oxide 
     6-nitro-2-phenyl-2H-benzotriazole 1-oxide 
     4-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-nitro-2-o-tolyl-2H-benzotriazole 1-oxide 
     6-nitro-2-p-tolyl-2H-benzotriazole 1-oxide 
     6-nitro-2-(2,4,5-trimethylphenyl)-2H-benzotriazole 1-oxide 
     2-phenyl-2H-benzotriazole 1-oxide 
     2-o-tolyl-2H-benzotriazole 1-oxide 
     2-p-tolyl-2H-benzotriazole 1-oxide 
     The mediator can preferably furthermore be selected among the group consisting of cyclic N-hydroxy compounds having at least one optionally substituted five or six-membered ring which contains the structure mentioned in formula V ##STR10## and their salts, ethers or esters, where B and D are identical or different and are O, S or NR 18 , 
     R 18  being hydrogen, hydroxyl, formyl, carbamoyl, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phospho, phosphono, phosphonooxy radical, ester or salt of the phosphonooxy radical, it being possible for carbamoyl, sulfamoyl, amino and phenyl radicals to be unsubstituted or mono- or polysubstituted by a radical R 19  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl and carbonyl C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 19 , R 19  being identical or different and being a hydroxyl, formyl or carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono or ester or salt of the sulfono radical, sulfamoyl, nitro, amino, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical. 
     The mediator is preferably selected from the group of the compounds of the general formula VI, VII, VIII or IX, ##STR11## where B and D have the meanings which have already been mentioned and the radicals R 20  -R 35  are identical or different and are a halogen radical, carboxyl radical, salt or ester of a carboxyl radical or have the meanings mentioned for R 18 , where R 26  and R 27 , or R 28  and R 29 , respectively, must not simultaneously be a hydroxyl or amino radical, and where, if appropriate, in each case two of the substituents R 20  -R 23 , R 24  -R 25 , R 26  -R 29 , R 30  -R 35  can be linked to give a ring --E--, --E-- having one of the following meanings: 
     (--CH═CH)-- n , where n=1 to 3, --CH═CH--CH═N-- or ##STR12## and where, if appropriate, the radicals R 26  -R 29  can also be linked to each other by one or more bridging elements --F--, --F-- being identical or different and having one of the following meanings: --O--, --S, --CH 2  --, --CR 36  ═CR 37  ; R 36  and R 37  being identical or different and having the meaning of R 20 . 
     Especially preferred as mediators are compounds of the general formulae VI, VII, VIII or IX, where B and D are O or S. 
     Examples of such compounds are N-hydroxyphthalimide and optionally substituted N-hydroxyphthalimide derivatives, N-hydroxymaleimide and optionally substituted N-hydroxymaleimide derivatives, N-hydroxynaphthalimide and optionally substituted N-hydroxynaphthalimide derivatives, N-hydroxysuccinimide and optionally substituted N-hydroxysuccinimide derivatives, preferably those where the radicals R 26  -R 29  are linked in the form of polycycles. 
     Examples of compounds of the formula VI which are suitable as mediator are: 
     N-hydroxyphthalimide, 
     3-amino-N-hydroxyphthalimide, 
     4-amino-N-hydroxyphthalimide, 
     N-hydroxybenzene-1,2,4-tricarboximide, 
     N,N&#39;-dihydroxypyromellitic diimide, 
     N,N&#39;-dihydroxybenzophenone-3,3&#39;,4,4&#39;-tetracarboxylic diimide. 
     Examples of compounds of the formula VII which are suitable as mediator are: 
     N-hydroxymaleimide, 
     N-hydroxy-pyridine-2,3-dicarboximide. 
     Examples of compounds of the formula VIII which are suitable as mediator are: 
     N-hydroxysuccinimide, 
     N-hydroxytartarimide, 
     N-hydroxy-5-norbornene-2,3-dicarboximide, 
     exo-N-hydroxy-7-oxabicyclo[2.2.1]-hept-5-ene-2,3-dicarboximide, 
     N-hydroxy-cis-cyclohexane-1,2-dicarboximide, 
     N-hydroxy-cis-4-cyclohexene-1,2-dicarboximide. 
     An example of the compound of the formula IX which is suitable as mediator is: 
     N-hydroxynaphthalimide-sodium salt. 
     An example of a compound with a six-membered ring containing the structure mentioned in formula V and suitable as mediator is: 
     N-hydroxyglutarimide. 
     The compounds which have been mentioned by way of example are also suitable as mediator in the form of their salts or esters. 
     Also suitable as mediator are compounds selected from the group of the N-aryl-N-hydroxyamides. 
     Among these, compounds which are preferably employed as mediators are those of the general formula X, XI or XII ##STR13## and their salts, ethers or esters, where G is a monovalent homo- or heteroaromatic mono- or binuclear radical and 
     L is a divalent homo- or heteroaroinatic mono- or binuclear radical, and it being possible for these aromatics to be substituted by one or more identical or different radicals R 38  selected from the group consisting of halogen, hydroxyl, formyl, cyano, carbamoyl, carboxyl radical, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phosphor phosphono or phosphonooxy radical, ester or salt of the phosphonooxy radical, and it being possible for carbamoyl, sulfamoyl, amino and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 39  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 39 , 
     R 39  being identical or different and being hydroxyl, formyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, nitroso, amino, phenyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical and it being possible for in each case two radicals R 38  or R 39  to be linked, in pairs, via a bridge [--CR 40  R 41  --] m  where m equals 0, 1, 2, 3 or 4 and 
     R 40  and R 41  are identical or different and are a carboxyl radical, ester or salt of the carboxyl radical, phenyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical and it being possible for one or more nonadjacent groups [--CR 40  R 41  --] to be replaced by oxygen, sulfur or by an imino radical which is optionally substituted by C 1  to C 5  -alkyl radical and it being possible for two adjacent groups [--CR 40  R 41  --] to be replaced by a group [--CR 40  ═CR 41  --] and I is a monovalent acid radical, present in amide form, of acids selected from the group consisting of carboxylic acid having up to 20 C atoms, carbonic acid, monoester of carbonic acid or of carbamic acid, sulfonic acid, phosphonic acid, phosphoric acid, monoester of phosphoric acid, diester of phosphoric acid and K is a divalent acid radical, present in amide form, of acids selected from the group consisting of mono- and dicarboxylic acids having up to 20 C atoms, carbonic acid, sulfonic acid, phosphonic acid, phosphoric acid or monoester of phosphoric acid. 
     Especially preferred as mediators are compounds of the general formula XIII, XIV, XV, XVI or XVII: ##STR14## and their salts, ethers or esters, where Ar 1  is a monovalent homo- or heteroaromatic mononuclear aryl radical and Ar 2  is a divalent homo- or heteroaromatic mononuclear aryl radical, each of which can be substituted by one or more identical or different radicals R 44  selected from the group consisting of hydroxyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, nitro, nitroso, amino, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl or carbonyl-C 1  -C 6  -alkyl radical, it being possible for amino radicals to be unsubstituted or mono- or polysubstituted by a radical R 45  and it being possible for the C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl and carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 45 , R 45  being identical or different and being hydroxyl, carboxyl radical, ester or salt of the carboxyl radical, sulfono, nitro, amino, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical and it being possible for in each case two radicals R 44  to be linked, in pairs, via a bridge [--CR 40  R 41  --] m  where m equals 0, 1, 2, 3 or 4 and R 40  and R 41  have the meanings which have already been mentioned and one or more nonadjacent groups [--CR 40  R 41  --] can be replaced by oxygen, sulfur or by an imino radical which is optionally substituted by a C 1  - to C 5  -alkyl radical, and two adjacent groups [--CR 40  R 41  --] can be replaced by a group [--CR 40  ═CR 41  --], 
     R 42  is identical or different monovalent radicals selected from the group consisting of hydrogen, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 10  -carbonyl radical, it being possible for phenyl radicals to be unsubstituted or mono- or polysubstituted by a radical R 46  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 46 , 
     R 46  being identical or different and being hydroxyl, formyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, nitroso, amino, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical and 
     R 43  being divalent radicals selected from the group consisting of ortho-, meta-, para-phenylene, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkylene or C 1  -C 5  -alkylenedioxy radical, it being possible for the phenylene radicals to be unsubstituted or mono- or polysubstituted by a radical R 46   
     and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl or C 1  -C 5  -alkoxy radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 46 , p being 0 or 1 and q being an integer from 1 to 3. 
     Preferably, Ar 1  is a phenyl radical and Ar 2  an ortho-phenylene radical, it being possible for Ar 1  to be substituted by up to five and for Ar 2  to be substituted by up to four identical or different radicals selected from the group consisting of C 1  -C 3  -alkyl, C 1  -C 3  -alkylcarbonyl, carboxyl radical, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, hydroxyl, cyano, nitro, nitroso and amino radical, it being possible for amino radicals to be substituted by two different radicals selected from the group consisting of hydroxyl and C 1  -C 3  -alkylcarbonyl. 
     Preferably, R 42  is a monovalent radical selected from the group consisting of hydrogen, phenyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy radical, it being possible for the C 1  -C 12  -alkyl radicals and the C 1  -C 5  -alkoxy radicals to be saturated or unsaturated, branched or unbranched. 
     Preferably, R 43  is divalent radicals selected from the group consisting of ortho- or para-phenylene, C 1  -C 12  -alkylene, C 1  -C 5  -alkylenedioxy radical, it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl and C 1  -C 5  -alkoxy radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 46 . 
     R 46  is preferably carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, phenyl or C 1  -C 3  -alkoxy radical. 
     Examples of compounds which can be employed as mediators are N-hydroxyacetanilide, N-hydroxypivaloylanilide, N-hydroxyacrylanilide, N-hydroxybenzoylanilide, N-hydroxymethylsulfonylanilide, N-hydroxy-N-phenylmethyl carbamate, N-hydroxy-3-oxo-butyrylanilide, N-hydroxy-4-cyanoacetanilide, N-hydroxy-4-methoxyacetanilide, N-hydroxyphenacetin, N-hydroxy-2,3-dimethylacetanilide, N-hydroxy-2-methylacetanilide, N-hydroxy-4-methylacetanilide, 1-hydroxy-3,4-dihydroquinolin-(1H)-2-one, N,N&#39;-dihydroxy-N,N&#39;-diacetyl-1,3-phenylenediamine, N,N&#39;-dihydroxysuccinanilide, N,N&#39;-dihydroxymaleianilide, N,N&#39;-dihydroxyoxalanilide, N,N&#39;-dihydroxyphosphoranilide, N-acetoxyacetanilide, N-hydroxymethyloxalylanilide, N-hydroxymaleianilide. 
     Mediators which are preferably used are N-hydroxyacetanilide, N-hydroxyformanilide, N-hydroxy-N-phenylmethylcarbamate, N-hydroxy-2-methylacetanilide, N-hydroxy-4-methylacetanilide, 1-hydroxy-3,4-dihydroquinolin-(1H)-2-one and N-acetoxyacetanilide. 
     The mediator can furthermore be selected from the group of the N-alkyl-N-hydroxy-amides. 
     Mediators which are preferably employed are compounds of the general formula (XVIII) or (XIX) ##STR15## and their salts, ethers or esters, where M is identical or different and is a monovalent linear or branched or cyclic or polycyclic saturated or unsaturated alkyl radical having 1-24 C atoms, and 
     it being possible for this alkyl radical to be substituted by one or more radicals R 48 , which are identical or different and are selected from the group consisting of hydroxyl, mercapto, formyl, carbamoyl, carboxyl, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, hydroxylamino, phenyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, phospho, phosphono, phosphonooxy radical, ester or salt of the phosphonooxy radical, and 
     it being possible for carbamoyl, sulfamoyl, amino, hydroxylamino, mercapto and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 48 , and it being possible for the C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 48 , R 48  being identical or different and being hydroxyl, formyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, nitroso, amino, phenyl, benzoyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical, and it being possible for methylene groups which are not in the α-position to be replaced by oxygen, sulfur or by an optionally mono-substituted imino radical, and where N is a monovalent acid radical, present in amide form, of acids selected from the group consisting of aliphatic or mono- or binuclear aromatic or mono- or binuclear heteroaromatic carboxylic acids having up to 20 C atoms, carbonic acid, monoester of carbonic acid or of carbamic acid, sulfonic acid, phosphonic acid, phosphoric acid, monoester of phosphoric acid, diester of phosphoric acid, and T is a divalent acid radical, present in amide form, of acids selected from the group consisting of aliphatic, mono- or binuclear aromatic or mono- or binuclear heteroaromatic dicarboxylic acids having up to 20 C atoms, carbonic acid, sulfonic acid, phosphonic acid, phosphoric acid, monoester of phosphoric acid, and it being possible for alkyl radicals of the aliphatic acids N and T, present in amide form, to be linear or branched and/or to be saturated or unsaturated in the cycle and/or polycycle and to contain 0-24 carbon atoms and to be unsubstituted or to be mono- or polysubstituted by the radical R 47  and 
     it being possible for aryl and heteroaryl radicals of the aromatic or heteroaromatic acids N and T, present in amide form, to be substituted by one or more radicals R 49  which are identical or different and are selected from the group consisting of hydroxyl, mercapto, formyl, cyano, carbamoyl, carboxyl, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, phospho, phosphono, phosphonooxy radical, ester or salt of the phosphonooxy radical and 
     it being possible for carbamoyl, sulfamoyl, amino, mercapto and phenyl radicals to be unsubstituted or mono- or polysubstituted by the radical R 48  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl-C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by the radical R 48 . 
     Especially preferred as mediators are compounds of the general formula (XX, XXI, XXII or XXIII): ##STR16## and their salts, ethers or esters, where Alk 1  is identical or different and is a monovalent linear or branched or cyclic or polycyclic saturated or unsaturated alkyl radical having 1-10 C atoms, 
     it being possible for this alkyl radical to be substituted by one or more radicals R 50  which are identical or different and are selected from the group consisting of hydroxyl, formyl, carbamoyl, carboxyl, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, hydroxylamino, phenyl, C 1  -C 5  -alkoxy or C 1  -C 5  -carbonyl radicals and 
     it being possible for carbamoyl, sulfamoyl, amino, hydroxylamino and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 51  and it being possible for the C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 51 , 
     R 51  being identical or different and being hydroxyl, formyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, amino, phenyl, benzoyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical and 
     it being possible for methylene groups which are not in the α-position to be replaced by oxygen, sulfur or by an optionally monosubstituted imino radical and R 53  being identical or different monovalent radicals selected from the group consisting of hydrogen, phenyl, pyridyl, furyl, pyrrolyl, thienyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 10  -alkoxy or C 1  -C 10  -carbonyl radical, 
     it being possible for phenyl, pyridyl, furyl, pyrrolyl and thienyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 7  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 53  and R 53  is identical or different and is hydroxyl, formyl, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, amino, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical and R 54  is divalent radicals selected from the group consisting of phenylene, pyridylene, thienylene, furylene, pyrrolylene, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkylene or C 1  -C 5  -alkylenedioxy radical, it being possible for phenylene, pyridylene, thienylene, furylene and pyrrolylene to be unsubstituted or to be mono- or polysubstituted by a radical R 53  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl and C 1  -C 5  -alkoxy radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 53 , p being 0 or 1. 
     Very especially preferred as mediators are compounds of the general formulae (XX-XXIII), where Alk 1  is identical or different and is a monovalent linear or branched or cyclic saturated or unsaturated alkyl radical having 1-10 C atoms, 
     it being possible for this alkyl radical to be substituted by one or more radicals R 50  which are identical or different and are selected from the group consisting of hydroxyl, carbamoyl, carboxyl, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, amino, phenyl, C 1  -C 5  -alkoxy or C 1  -C 5  -carbonyl radicals and 
     it being possible for carbamoyl, sulfamoyl, amino and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 51  and it being possible for the C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 51 , R 51  being identical or different and being hydroxyl, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, amino, phenyl, benzoyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy or C 1  -C 5  -alkylcarbonyl radical and R 52  being identical or different monovalent radicals selected from the group consisting of hydrogen, phenyl, furyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 10  -alkoxy or C 1  -C 10  -carbonyl radical, 
     it being possible for phenyl and furyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 53  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy and C 1  -C 10  -carbonyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 53 , R 53  being identical or different and being a carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical and R 54  is a divalent radical selected from the group consisting of phenylene, furylene, C 1  -C 12  -alkylene and C 1  -C 5  -alkylenedioxy radical, it being possible for phenylene and furanylene to be unsubstituted or to be mono- or or polysubstituted by a radical R 53  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl and C 1  -C 5  -alkoxy radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 53 , p being 0 or 1. 
     Examples of compounds which can be employed as mediators are N-hydroxy-N-methylbenzamide, N-hydroxy-N-methylbenzenesulfonamide, N-hydroxy-N-methyl-p-toluenesulfonamide, N-hydroxy-N-methylfuran-2-carboxamide, N-hydroxy-N-methylthiophene-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylphthalamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylisophthalamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylbenzene-1,3-disulfonamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylfuran-3,4-dicarboxamide, N-hydroxy-N-tert-butylbenzamide, N-hydroxy-N-tert-butylbenzenesulfonamide, N-hydroxy-N-tert-butyl-p-toluenesulfonamide, N-hydroxy-N-tert-butylfuran-2-carboxamide, N-hydroxy-N-tert-butylthiophene-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylphthalamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylisophthalamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylbenzene-1,3-disulfonamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylfuran-3,4-dicarboxamide, N-hydroxy-N-cyclohexylbenzamide, N-hydroxy-N-cyclohexylbenzenesulfonamide, N-hydroxy-N-cyclohexyl-p-toluenesulfonamide, N-hydroxy-N-cyclohexylfuran-2-carboxamide, N-hydroxy-N-cyclohexylthiophene-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-dicyclohexylphthalamide, N,N&#39;-dihydroxy-N,N&#39;-dicyclohexylisophthalamide, N,N&#39;-dihydroxy-N,N&#39;-dicyclohexylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-dicyclohexylbenzene-1,3-disulfonamide, N,N&#39;-dihydroxy-N,N&#39;-dicyclohexylfuran-3,4-dicarboxamide, N-hydroxy-N-isopropylbenzamide, N-hydroxy-N-isopropylbenzenesulfonamide, N-hydroxy-N-isopropyl-p-toluenesulfonamide, N-hydroxy-N-isopropylfuran-2-carboxamide, N-hydroxy-N-isopropylthiophene-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylphthalamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylisophthalamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylbenzene-1,3-disulfonamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylfuran-3,4-dicarboxamide, N-hydroxy-N-methylacetamide, N-hydroxy-N-tert-butylacetamide, N-hydroxy-N-isopropylacetamide, N-hydroxy-N-cyclohexylacetamide, N-hydroxy-N-methylpivalamide, N-hydroxy-N-isopropyl-pivalamide, N-hydroxy-N-methylacrylamide, N-hydroxy-N-tert-butylacrylamide, N-hydroxy-N-isopropylacrylamide, N-hydroxy-N-cyclohexylacrylamide, N-hydroxy-N-methylmethanesulfonamide, N-hydroxy-N-isopropylmethane-sulfonamide, N-hydroxy-N-isopropylmethylcarbamate, N-hydroxy-N-methyl-3-oxobutyramide, N,N&#39;-dihydroxy-N,N&#39;-dibenzoylethylenediamine, N,N&#39;-dihydroxy-N,N&#39;-dimethylsuccinamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylmaleamide, N-hydroxy-N-tert-butylmaleamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butyloxalamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylphosphoramide. 
     Compounds which are preferably selected as mediators are from the group consisting of N-hydroxy-N-methylbenzamide, N-hydroxy-N-methylbenzenesulfonamide, N-hydroxy-N-methyl-p-toluenesulfonamide, N-hydroxy-N-methylfuran-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylphthalamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-dimethylbenzene-1,3-disulfonamide, N-hydroxy-N-tert-butylbenzamide, N-hydroxy-N-tert-butylbenzenesulfonamide, N-hydroxy-N-tert-butyl-p-toluenesulfonamide, N-hydroxy-N-tert-butylfuran-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylterephthalamide, N-hydroxy-N-isopropylbenzamide, N-hydroxy-N-isopropyl-p-toluenesulfonamide, N-hydroxy-N-isopropylfuran-2-carboxamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylterephthalamide, N,N&#39;-dihydroxy-N,N&#39;-diisopropylbenzene-1,3-disulfonamide, N-hydroxy-N-methylacetamide, N-hydroxy-N-tert-butylacetamide, N-hydroxy-N-isopropylacetamide, N-hydroxy-N-cyclohexylacetamide, N-hydroxy-N-methylpivalamide, N-hydroxy-N-tert-butylacrylamide, N-hydroxy-N-isopropylacrylamide, N-hydroxy-N-methyl-3-oxobutyramide, N,N&#39;-dihydroxy-N,N&#39;-dibenzoylethylenediamine, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butylmaleamide, N-hydroxy-N-tert-butylmaleamide, N,N&#39;-dihydroxy-N,N&#39;-di-tert-butyloxalamide. 
     The mediator can furthermore be selected from the group of the oximes of the general formula XXIV or XXV ##STR17## and their salts, ethers or esters, where U is identical or different and is O, S or NR 55 , R 55  being hydrogen, hydroxyl, formyl, carbamoyl, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phospho, phosphono or phosphonooxy radical, ester or salt of the phosphonooxy radical, it being possible for carbamoyl, sulfamoyl, amino and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 56  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl and carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 56 , 
     R 56  being identical or different and being hydroxyl, formyl, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, ester or salt of the sulfono radical, sulfamoyl, nitro, amino, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical and the radicals R 57  and R 58  being identical or different and being halogen, carboxyl radical, ester or salt of the carboxyl radical, or having the meanings mentioned for R 55 , or being linked to a ring [--CR 61  R 62  ] n  where n equals 2, 3 or 4 and R 59  and R 60  having the meanings mentioned for R 55  and R 61  and R 62  being identical or different and being halogen, carboxyl radical, ester or salt of the carboxyl radical, or having the meanings mentioned for R 55 . 
     Especially preferred as mediators are compounds of the general formula XXIV where U is O or S and the remaining radicals have the meanings mentioned above. An example of such a compound is dimethyl 2-hydroxyiminomalonate. 
     Furthermore especially preferred as mediators are isonitroso derivatives of cyclic ureides of the general formula XXV. Examples of such compounds are 1-methylvioluric acid, 1,3-dimethylvioluric acid, thiovioluric acid, alloxane 4,5-dioxime. 
     Particularly preferred as mediator is alloxane 5-oxime hydrate (violuric acid) and/or its esters, ethers or salts. 
     The mediator can furthermore be selected from the group of the vicinally nitroso-substituted aromatic alcohols of the general formula XXVI or XXVII ##STR18## and their salts, ethers or esters, where R 63 , R 64 , R 65  and R 66  are identical or different and are hydrogen, halogen, hydroxyl, formyl, carbamoyl, carboxyl radical, ester or salt of the carboxyl radical, sulfono radical, ester or salt of the sulfono radical, sulfamoyl, nitro, nitroso, cyano, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phospho, phosphono or phosphonooxy radical, ester or salt of the phosphonooxy radical, 
     it being possible for carbamoyl, sulfamoyl, amino and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 67  and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl and carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 67 , R 67  being identical or different and being hydroxyl, formyl, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, nitroso, amino, phenyl, C 1  -C 5  -alkyl or C 1  -C 5  -alkoxy radical, or 
     it being possible for the radicals R 63  -R 66 , in pairs, to be linked to give a ring [CR 68  R 69  --] m  where m is an integer and denotes a value of 1 to 4, or linked to give a ring [CR 70  ═CR 71  --] n , where n is an integer and denotes a value of 1 to 3, and R 68 , R 69 , R 70  and R 71  being identical or different and having the meanings mentioned for R 63  to R 66 . 
     Aromatic alcohols are preferably to be understood as meaning phenols or higher-condensed phenol derivatives. 
     Preferred as mediators are compounds of the general formula XXVI or XXVII whose synthesis can be based on the nitrosization of substituted phenols. Examples of such compounds are 2-nitrosophenol, 3-methyl-6-nitrosophenol, 2-methyl-6-nitrosophenol, 4-methyl-6-nitrosophenol, 3-ethyl-6-nitrosophenol, 2-ethyl-6-nitrosophenol, 4-ethyl-6-nitrosophenol, 4-isopropyl-6-nitrosophenol, 4-tert-butyl-6-nitrosophenol, 2-phenyl-6-nitrosophenol, 2-benzyl-6-nitrosophenol, 4-benzyl-6-nitrosophenol, 2-hydroxy-3-nitrosobenzyl alcohol, 2-hydroxy-3-nitrosobenzoic acid, 4-hydroxy-3-nitrosobenzoic acid, 2-methoxy-6-nitrosophenol, 3,4-dimethyl-6-nitrosophenol, 2,4-dimethyl-6-nitrosophenol, 3,5-dimethyl-6-nitrosophenol, 2,5-dimethyl-6-nitrosophenol, 2-nitrosoresorcin, 4-nitrosoresorcin, 2-nitrosoorcin, 2-nitrosophloroglucine and 4-nitrosopyrogallol, 4-nitroso-3-hydroxyaniline, 4-nitro-2-nitrosophenol. 
     Furthermore preferred as mediators are o-nitroso derivatives of higher-condensed aromatic alcohols. Examples of such compounds are 2-nitroso-1-naphthol, 1-methyl-3-nitroso-2-naphthol and 9-hydroxy-10-nitrosophenanthrene. 
     The mediator can furthermore be selected from the group consisting of hydroxypyridines, aminopyridines, hydroxyquinolines, aminoquinolines, hydroxyisoquinolines, aminoisoquinolines, with the nitroso or mercapto substituents which are in the ortho- or para-positions relative to the hydroxyl or amino groups, tautomers of the compounds mentioned, and their salts, ethers and esters. 
     Preferred as mediators are compounds of the general formula (XXVIII), (XXIX) or (XXX) ##STR19## and tautomers, salts, ethers or esters of the compounds mentioned, where, in formulae XXVIII, XXIX and XX, two radicals R 72  which are in the ortho- or para-position relative to each other are the hydroxyl and nitroso radical or hydroxyl and mercapto radical or nitroso radical and amino radical 
     and the remaining radicals R 72  are identical or different are are selected from the group consisting of hydrogen, halogen, hydroxyl, mercapto, formyl, cyano, carbamoyl, carboxyl radical, ester and salt of the carboxyl radical, sulfono radical, ester and salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phospho, phosphono and phosphonooxy radical, ester and salt of the phosphonooxy radical, and 
     it being possible for carbamoyl, sulfamoyl, amino, mercapto and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 73 , 
     and it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 12  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 10  -carbonyl and carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 73 , R 73  being identical or different and being hydroxyl, formyl, cyano, carboxyl radical, ester or salt of the carboxyl radical, carbamoyl, sulfono, sulfamoyl, nitro, nitroso, amino, phenyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy radical or C 1  -C 5  -alkylcarbonyl radical and 
     it being possible for in each case two radicals R 72  or two radicals R 73  or R 72  and R 73 , in pairs, to be linked via a bridge [--CR 74  R 75  --] m  where m equals 1, 2, 3 or 4 and 
     R 3  and R 4  are identical or different and are a carboxyl radical, ester or salt of the carboxyl radical, phenyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy radical or C 1  -C 5  -alkylcarbonyl radical and 
     it being possible for one or more nonadjacent groups [--CR 74  R 75  --] to be replaced by oxygen, sulfur or by an imino radical which is optionally substituted by C 1  -C 5  -alkyl, and it being possible for two adjacent groups [--CR 74  R 75  --] to be replaced by a group [--CR 74  ═R 75  --]. 
     Especially preferred as mediators are compounds of the general formula (XXVIII) or (XXIX) and their tautomers, salts, ethers or esters, where, in formulae (XXVIII) and (XXIX) especially preferred meanings of two radicals R 72  in the ortho-position relative to each other are the hydroxyl and nitroso radical or hydroxyl and mercapto radical or nitroso radical and amino radical and the remaining radicals R 72  are identical or different and are selected from the group consisting of hydrogen, hydroxyl, mercapto, formyl, carbamoyl, carboxyl radical, ester and salt of the carboxyl radical, sulfono radical, ester and salt of the sulfono radical, sulfamoyl, nitro, nitroso, amino, phenyl, aryl-C 1  -C 5  -alkyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 5  -carbonyl, carbonyl-C 1  -C 6  -alkyl, phospho, phosphono and phosphonooxy radical, ester and salt of the phosphonooxy radical, 
     it being possible for carbamoyl, sulfamoyl, amino, mercapto and phenyl radicals to be unsubstituted or to be mono- or polysubstituted by a radical R 73  and 
     it being possible for the aryl-C 1  -C 5  -alkyl, C 1  -C 5  -alkyl, C 1  -C 5  -alkoxy, C 1  -C 5  -carbonyl and carbonyl-C 1  -C 6  -alkyl radicals to be saturated or unsaturated, branched or unbranched and to be mono- or polysubstituted by a radical R 73 , R 73  having the meanings which have already been mentioned and 
     it being possible for in each case two radicals R 73 , in pairs, to be linked via a bridge [--CR 74  R 75  --] m  where m equals 2, 3 or 4 and R 74  and R 75  having the meanings which have already been mentioned and 
     it being possible for one or more nonadjacent groups [--CR 74  R 75  --] to be replaced by oxygen or by an imino radical which is optionally substituted by C 1  -C 5  -alkyl. 
     Examples of compounds which can be employed as mediators are 2,6-dihydroxy-3-nitrosopyridine, 2,3-dihydroxy-4-nitrosopyridine, 2,6-dihydroxy-3-nitrosopyridine-4-carboxylic acid, 2,4-dihydroxy-3-nitrosopyridine, 3-hydroxy-2-mercaptopyridine, 2-hydroxy-3-mercaptopyridine, 2,6-diamino-3-nitrosopyridine, 2,6-diamino-3-nitrosopyridine-4-carboxylic acid, 2-hydroxy-3-nitrosopyridine, 3-hydroxy-2-nitrosopyridine, 2-mercapto-3-nitrosopyridine, 3-mercapto-2-nitrosopyridine, 2-amino-3-nitrosopyridine, 3-amino-2-nitrosopyridine, 2,4-dihydroxy-3-nitrosoquinoline, 8-hydroxy-5-nitrosoquinoline, 2,3-dihydroxy-4-nitrosoquinoline, 3-hydroxy-4-nitrosoisoquinoline, 4-hydroxy-3-nitrosoisoquinoline, 8-hydroxy-5-nitrosoisoquinoline and tautomers of these compounds. 
     Preferred as mediators are 2,6-dihydroxy-3-nitrosopyridine, 2,6-diamino-3-nitrosopyridine, 2,6-dihydroxy-3-nitrosopyridine-4-carboxylic acid, 2,4-dihydroxy-3-nitrosopyridine, 2-hydroxy-3-mercaptopyridine, 2-mercapto-3-pyridinol, 2,4-dihydroxy-3-nitrosoquinoline, 8-hydroxy-5-nitrosoquinoline, 2,3-dihydroxy-4-nitrosoquinoline and tautomers of these compounds. 
     Very especially preferred mediators are N-hydroxyphthalimide, 1-hydroxy-1H-benzotriazole, violuric acid, N-hydroxyacetanilide, nitrosonaphthol, nitrosopyridinol and their derivatives which have been given above. 
     Most preferred are 3-amino-N-hydroxyphthalimide, 4-amino-N-hydroxyphthalimide, N-hydroxyphthalimide, 3-hydroxy-N-hydroxyphthalimide, 3-methoxy-N-hydroxyphthalimide, 3,4-dimethoxy-N-hydroxyphthalimide, 4,5-dimethoxy-N-hydroxyphthalimide, 3,6-dihydroxy-N-hydroxyphthalimide, 3,6-dimethoxy-N-hydroxyphthalimide, 3-methyl-N-hydroxyphthalimide, 4-methyl-N-hydroxyphthalimide, 3,4-dimethyl-N-hydroxyphthalimide, 3,5-dimethyl-N-hydroxyphthalimide 3,6-dimethyl-N-hydroxyphthalimide, 3-isopropyl-6-methyl-N-hydroxyphthalimide, 3-nitro-N-hydroxyphthalimide, 4-nitro-N-hydroxyphthalimide, 1-hydroxy-1H-benzotriazole, violuric acid and N-hydroxyacetanilide, 3-nitrosoquinoline-2,4-diol, 2,4-dihydroxy-3-nitrosopyridine, 2,6-dihydroxy-3-nitrosopyridine, 2,4-dinitroso-1,3-dihydroxybenzene, 2-nitroso-1-naphthol-4-sulfonic acid and 1-nitroso-2-naphthol-3,6-disulfonic acid. 
     The oxidation is preferably carried out in the presence of 0.01 to 10 equivalents, preferably 0.05 to 1 equivalent, especially preferably 0.1 to 0.5 equivalent of one or more of the mediators described, preferably with one or two mediators, especially preferably with one mediator in water. 
     If appropriate, this is done with addition of 1 to 90 percent by weight, preferably 5 to 30 percent by weight, of a solvent which is at least partially miscible with water. It is preferred to add 1 to 3 organic solvents which are miscible with water as cosolvents. Examples of organic solvents which are miscible with water are ethanol, methanol, isopropanol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, acetone, acetonitrile, acetamide, tetrahydrofuran, dioxane, DMSO, DMF, sulfolane, methyl acetate, ethyl acetate, formic acid, acetic acid or propionic acid, or any mixtures of these. 
     The pH of the solution is preferably 2 to 8, especially preferably 4 to 5. 
     The reactions are preferably carried out at temperatures between 5 and 70° C., especially preferably 35-50° C. 
     The reaction times are preferably 2 to 100 hours, preferably 5 to 50 hours. 
     Oxidants which are preferably employed are air, oxygen, hydrogen peroxide, organic peroxides, peracids, perborates or persulfates, in each case in combination with enzymes. 
     Other oxidants are, for example, metal oxides or anodes of electrolysis cells. 
     The term enzyme for the purposes of the invention also includes enzymatically active proteins or peptides or prosthetic groups of enzymes. Enzymes which can preferably be employed in the multi-component system according to the invention are oxidoreductases of classes 1.1.1 to 1.97 in accordance with the International Enzyme Nomenclature, Committee of the International Union of Biochemistry and Molecular Biology (Enzyme Nomenclature, Academic Press, Inc., 1992, pp. 24-154). 
     Enzymes of the classes mentioned below are preferably employed: 
     Enzymes of class 1.1, which embrace all dehydrogenases which act on primary, secondary alcohols and semiacetals and which have, as acceptors NAD +  or NADP +  (subclass 1.1.1), cytochromes (1.1.2), oxygen (O 2 ) (1.1.3), disulfides (1.1.4), quinones (1.1.5) or which have other acceptors (1.1.99). 
     Especially preferred among this class are the enzymes of class 1.1.5 with quinones as the acceptors and the enzymes of class 1.1.3 with oxygen as the acceptor. 
     Particularly preferred among this class is cellobiose: quinone-1-oxidoreductase (1.1.5.1). 
     Furthermore preferred are enzymes of class 1.2. This enzyme class (1.1.5.1) embraces those enzymes which oxidize aldehydes to the corresponding acids or oxo groups. The acceptors can be NAD + , NADP +  (1.2.1), cytochromes (1.2.-2), oxygen (1.2.3), sulfides (1.2.4), iron-sulfur-proteins (1.2.5) or other acceptors (1.2.99). 
     Especially preferred here are the enzymes of group (1.2.3) with oxygen as the acceptor. 
     Furthermore preferred are enzymes of class 1.3. 
     In this class there are compiled enzymes which act on CH--CH groups of the donor. 
     The corresponding acceptors are NAD + , NADP +  (1.3.1), cytochromes (1.3.2), oxygen (1.3.3), quinones or related compounds (1.3.5), iron-sulfur-proteins (1.3.7) or other acceptors (1.3.99). 
     Especially preferred is bilirubin oxidase (1.3.3.5). 
     Again, the enzymes of class (1.3.3) with oxygen as the acceptor and (1.3.5) with quinones etc. as the acceptor are especially preferred here. 
     Furthermore preferred are enzymes of class 1.4, which act on CH--NH 2  groups of the donor. 
     The corresponding acceptors are NAD + , NADP +  (1.4.1), cytochromes (1.4.2), oxygen (1.4.3), disulfides (1.4.4), iron-sulfur-proteins (1.4.7) or other acceptors (1.4.99). 
     Here too, especially preferred are enzymes of class 1.4.3 with oxygen as the acceptor. 
     Furthermore preferred are enzymes of class 1.5, which act on CH--NH groups of the donor. The corresponding acceptors are NAD + , NADP +  (1.5.1), oxygen (1.5.3), disulfides (1.5.4), quinones (1.5.5) or other acceptors (1.5.99). 
     Again, especially preferred here are enzymes with oxygen (O 2 ) (1.5.3) and with quinones (1.5.5) as the acceptors. 
     Furthermore preferred are enzymes of class 1.6, which act on NADH or NADPH. 
     Here, the acceptors are NADP +  (1.6.1), hem proteins (1.6.2), disulfides (1.6.4), quinones (1.6.5), NO 2  groups (1.6.6) and a flavine (1.6.8) or some other acceptors (1.6.99). 
     Especially preferred here are enzymes of class 1.6.5 with quinones as the acceptors. 
     Furthermore preferred are enzymes of class 1.7, which act on other NO 2  compounds as donors and which have cytochromes (1.7.2), oxygen (O 2 ) (1.7.3), iron-sulfur-proteins (1.7.7) or others (1.7.99) as the acceptors. 
     Especially preferred here is class 1.7.3 with oxygen as the acceptor. 
     Furthermore preferred are enzymes of class 1.8, which act on sulfur groups as donors and which have NAD + , NADP +  (1.8.1), cytochromes (1.8.2), oxygen (O 2 ) (1.8.3), disulfides (1.8.4), quinones (1.8.5), iron-sulfur-proteins (1.8.7) or others (1.8.99) as the acceptors. 
     Especially preferred is class 1.8.3 with oxygen (O 2 ) and (1.8.5) with quinones as the acceptors. 
     Furthermore preferred are enzymes of class 1.9, which act on hem groups as donors and which have oxygen (O 2 ) (1.9.3), NO 2  compounds (1.9.6) and others (1.9.99) as the acceptors. 
     Especially preferred here is group 1.9.3 with oxygen (O 2 ) as the acceptor (cytochrome oxidases). 
     Furthermore preferred are enzymes of class 1.12, which act on hydrogen as the donor. 
     The acceptors are NAD +  or NADP +  (1.12.1) or others (1.12.99). 
     Furthermore preferred are enzymes of class 1.13 and 1.14 (oxygenases). 
     Furthermore preferred enzymes are those of class 1.15, which act on superoxide free radicals as the acceptors. 
     Especially preferred here is superoxide dismutase (1.15.1.1). 
     Furthermore preferred are enzymes of class 1.16. NAD +  or NADP +  (1.16.1) or oxygen (O 2 ) (1.16.3) act as the acceptors. 
     Especially preferred here are enzymes of class 1.16.3.1 (ferroxidase, e.g. ceruloplasmin). 
     Furthermore preferred enzymes are those which belong to group 1.17 (acts on CH 2  groups, which are oxidized to --CHOH--), 1.18 (acts on reduced ferredoxin as donor), 1.19 (acts on reduced flavodoxin as donor) and 1.97 (other oxidoreductases). 
     Furthermore especially preferred are the enzymes of group 1.11., which act on a peroxide as the acceptor. This single subclass (1.11.1) contains the peroxidases. 
     Especially preferred here are cytochrome c peroxidases (1.11.1.5), catalase (1.11.1.6), peroxidase (1.11.1.7), iodide peroxidase (1.11.1.8), glutathione peroxidase (1.11.1.9), chloride peroxidase (1.11.1.10), L-ascorbate peroxidase (1.11.1.11), phospholipid hydroperoxide glutathione peroxidase (1.11.1.12), manganese peroxidase (1.12.1.13) and diarylpropane peroxidase (ligninase, lignin peroxidase) (1.11.1.14). 
     Very especially preferred are enzymes of class 1.10, which act on biphenols and related compounds. They catalyze the oxidation of biphenols and ascorbates. NAD + , NADP +  (1.10.1), cytochromes (1.10.2), oxygen (1.10.3) or others (1.10.99) act as the acceptors. 
     Among these, in turn, especially preferred enzymes are those of class 1.10.3 with oxygen (O 2 ) as the acceptor. 
     Preferred among the enzymes of this class are the enzymes catechol oxidase (tyrosinase) (1.10.3.1), L-ascorbate oxidase (1.10.3.3), o-aminophenol oxidase (1.10.3.4) and laccase (benzenediol: oxygen oxidoreductase) (1.10.3.2), the laccases (benzenediol: oxygen oxidoreductase) (1.10.3.2) being particularly preferred. 
     The abovementioned enzymes are commercially available or can be obtained by standard processes. Organisms which are suitable for producing the enzymes are, for example, plants, animal cells, bacteria and fungi. In principle, naturally occurring and genetically altered organisms may be enzyme producers. Equally, parts of single- or many-celled organisms are conceivable as enzyme producers, above all cell cultures. 
     Examples of organisms which are used for the particularly preferred enzymes, such as those from group 1.11.1, but mainly 1.10.3, and in particular for the production of laccases are fungi that cause white rot such as Pleurotus, Phlebia and Trametes. 
     Preferred amongst the metal oxides employed as oxidants are those with a solubility of less than 1 g/l in the reaction medium. 
     The following are preferred: bismuth(III) oxide, iridium(III) oxide, cerium(IV) oxide, cobalt(II) oxide, cobalt(III) oxide, iron(III) oxide, manganese(IV) oxide, tin(IV) oxide, niobium(V) oxide, antimony(V) oxide, indium(III) oxide, mercury(II) oxide, lead(IV) oxide, silver(I) oxide, copper(II) oxide, palladium(II) oxide. 
     The following are especially preferred: lead(IV) oxide, manganese(IV) oxide, silver(I) oxide, copper(II) oxide, palladium(II) oxide. 
     The electrodes of the electrolysis cells used for oxidation can be identical or different. They are preferably composed of carbon, iron, lead, lead dioxide, copper, nickel, zinc, cadmium, mercury, tantalum, titanium, silver, platinum, platinized platinum, palladium, rhodium or gold, or alloys of the abovementioned compounds. 
     Especially preferred are various types of stainless steel, or tantalum, titanium, rhodium, platinum or gold. 
     The electrodes are very especially preferably composed of stainless steel, amongst which, in turn, types of stainless steel of Group 1.4xxx (in accordance with DIN 17850) are preferred. 
     If appropriate, the electrodes can have been coated with other substances by vapor deposition, sputtering, galvanizing or other similar processes. 
     The electrode surface can have been enlarged by suitable processes, for example by grinding, polishing, sand-blasting, corroding or eroding. 
     The process according to the invention allows aromatic and heteroaromatic aldehydes and ketones to be prepared from the corresponding hydroxyalkylaromatics or -heteroaromatics under mild reaction conditions. The reaction is preferably carried out in water, if appropriate with addition of a cosolvent as solubilizer, and is therefore especially inexpensive. The reaction solution is worked up in a simple manner, for example by extraction. The mediators used can be employed catalytically. Aromatics which are substituted by electron donors react especially fast. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying examples. It should be understood, however, that this is designed for the purpose of illustration only and not as a definition of the limits of the invention. 
     EXAMPLE 1 
     22 ml of a dipotassium hydrogen phosphate/citric acid buffer solution of pH 4.5 (prepared by titrating a 0.2 M potassium dihydrogen phosphate solution with a 0.1 M citric acid solution and diluting to 1/4) were treated at 45° C. with 269 mg (1.60 mmol) of 3,4-dimethoxybenzyl alcohol in 1 ml of ethanol. 32.1 mg (0.180 mmol) of 3-amino-N-hydroxyphthalimide were added with stirring. After approx. 10 minutes, the mixture was treated with 5 ml of an aqueous solution of 2 mg/ml laccase from Trametes versicolor (specific activity approx. 18 IU/mg, defined with ABTS as substrate). After a reaction time of 22 hours, the reaction solution was extracted with chloroform and examined by NMR spectroscopy. Yield 92% of 3,4-dimethoxybenzaldehyde. 
     EXAMPLE 2 
     An oxidation was carried out analogously to Example 1 with 31.9 mg (0.180 mmol) of 4-methyl-N-hydroxyphthalimide as mediator. HPLC analysis revealed a yield of 30% of 3,4-dimethoxybenzaldehyde. 
     EXAMPLE 3 
     An oxidation was carried out analogously to Example 1 with 29.3 mg (0.180 mmol) of N-hydroxyphthalimide as mediator. HPLC analysis revealed a yield of 27% of 3,4-dimethoxybenzaldehyde. 
     EXAMPLE 4 
     An oxidation was carried out analogously to Example 1 with 34.4 mg (0.180 mmol) of 3,4-dimethyl-N-hydroxythalimide phthalimides mediator. HPLC analysis revealed a yield of 32% of 3,4-dimethoxybenzaldehyde. 
     EXAMPLE 5 
     An oxidation was carried out analogously to Example 1 with 27.2 mg (0.180 mmol) of N-hydroxyacetanilide as mediator. Yield 51% of 3,4-dimethoxybenzaldehyde. 
     EXAMPLE 6 
     173 mg (1.60 mmol) of benzyl alcohol were reacted with 32.1 mg (0.180 mmol) of 3-amino-N-hydroxyphthalimide as mediator as described in Example 1. HPLC analysis after a reaction time of 22 hours revealed 22% of benzaldehyde. 
     EXAMPLE 7 
     245 mg (1.60 mmol) of 4-nitrobenzyl alcohol were reacted with 32.1 mg (0.180 mmol) of 3-amino-N-hydroxy-phthalimide as mediator as described in Example 1. HPLC analysis after a reaction time of 22 hours revealed 41% of 4-nitrobenzaldehyde. 
     EXAMPLE 8 
     196 mg (1.60 mmol) of 4-methylbenzyl alcohol were reacted with 32.1 mg (0.180 mmol) of 3-amino-N-hydroxyphthalimide as mediator as described in Example 1. HPLC analysis after a reaction time of 22 hours revealed 36% of 4-methylbenzaldehyde. 
     EXAMPLE 9 
     196 mg (1.60 mmol) of 1-phenylethanol were reacted with 32.1 mg (0.180 mmol) of 3-amino-N-hydroxyphthalimide as mediator as described in Example 1. HPLC analysis after a reaction time of 22 hours revealed 25% of acetophenone. 
     EXAMPLE 10 
     173 mg (1.60 mmol) of benzyl alcohol were reacted with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole as mediator as described in Example 1. HPLC analysis after a reaction time of 4 hours revealed 12% of benzaldehyde. 
     EXAMPLE 11 
     245 mg (1.60 mmol) of 4-nitrobenzyl alcohol were reacted with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole as mediator as described in Example 1. HPLC analysis after a reaction time of 4 hours revealed 10% of 4-nitrobenzaldehyde. 
     EXAMPLE 12 
     196 mg (1.60 mmol) of 4-methylbenzyl alcohol were reacted with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole as mediator as described in Example 1. HPLC analysis after a reaction time of 4 hours revealed 19% of 4-methylbenzaldehyde. 
     EXAMPLE 13 
     196 mg (1.60 mmol) of 1-phenyl ethanol were reacted with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole as mediator as described in Example 1. HPLC analysis after a reaction time of 4 hours revealed 12% of acetophenone. 
     EXAMPLE 14 
     0.40 mmol of a benzyl alcohol (see Table 1) and 0.045 mmol of mediator (VIO: violuric acid, HBT: 1-hydroxy-1H-benzotriazole, NHA: N-hydroxyacetanilide) were reacted analogously to Example 1 in 22 ml of buffer solution in the presence of 2.5 ml of an aqueous solution of 1 mg/ml laccase. After a reaction time of 24 hours, the samples were analyzed by HPLC. See Table 1 for results. 
     
                       TABLE 1______________________________________Formation of benzaldehydes after 24 hours.                 Mediators             without   HBT    NHA  Starting materials [%] [%] [%]______________________________________5-Nitrobenzyl alcohol             0         7      2  Benzyl alcohol 1 22 7  1-Phenylethanol 0.5 10 3  2-Methylbenzyl alcohol 0 26 9  4-Methylbenzyl alcohol 0 26 4  3,4-Dimethoxybenzyl alcohol 0.5 83 13  2,4,6-Trimlethylbenzyl alcohol 1 5 4______________________________________ 
    
     EXAMPLE 15 
     239 mg (1.0 mmol) of lead(IV) oxide were treated with 0.40 mmol of the benzyl alcohol in question, 0.05 mmol of the mediator and 25 ml of the buffer solution (see Example 1). The vigorously stirred reaction mixture was heated at 45° C. in a sealed flask. Samples were taken after 4 and 24 hours. After the lead oxide had been removed by filtration (sterile filter), the product distribution was determined by HPLC analysis. Results in Table 2. 
     
                       TABLE 2______________________________________Oxidation of benzyl alcohols with lead (IV) oxide  and various mediators (VIO: violuric acid, HBT: 1-hydroxy-  1H-benzotriazole)                               Aldehyde/  Substrate Mediator Alcohol ketone______________________________________3,4-Dimethoxybenzyl alcohol          VIO        96      4  3,4-Dimethoxybenzyl alcohol HBT 50 50  4-Nitrobenzyl alcohol VIO 95 5  4-Nitrobenzyl alcohol HBT 98 2  2-Methylbenzyl alcohol VIO 93 7  2-Methylbenzyl alcohol HBT 95 5  1-Phenylethane-1,2-diol VIO 96 4  1-Phenylethane-1,2-diol HBT 96 4______________________________________ 
    
     EXAMPLE 16 
     0.6 mmol of the benzyl alcohols were dissolved in 40 ml of acetate buffer (pH 4.5) and subjected to electrolysis for 4 hours at room temperature in a twin-chamber system with steel electrodes at a voltage of 40 V and a current of approx. 50 mA. The amount of mediator was in each case 0.15 mmol. After 4 hours, the reaction mixture was analyzed by HPLC. Results in Table 3. 
     
                       TABLE 3______________________________________Oxidation of benzyl alcohols by electrochemical  activation of mediators (VIO: violuric acid, HBT: 1-hydroxy-  1H-benzotriazole, NHA: N-hydroxyacetanilide)                               Aldehyde/  Substrate Mediator Alcohol ketone______________________________________3,4-Dimethoxybenzyl alcohol          VIO        95      5  3,4-Dimethoxybenzyl alcohol HBT 88 12  3,4-Dimethoxybenzyl alcohol NHA 96 4  4-Nitrobenzyl alcohol VIO 93 7  4-Nitrobenzyl alcohol HBT 98 2  4-Nitrobenzyl alcohol NHA 100 0  2-Methylbenzyl alcohol VIO 88 12  2-Methylbenzyl alcohol HBT 97 3  2-Methylbenzyl alcohol NHA 100 0  4-Methylbenzyl alcohol VIO 89 11  4-Methylbenzyl alcohol HBT 96 4  4-Methylbenzyl alcohol NHA 99 1  Benzyl alcohol VIO 91 9  Benzyl alcohol HBT 96 4  Benzyl alcohol NHA 97 3  1-Phenylethanol VIO 94 6  1-Phenylethanol HBT 98 2  1-Phenylethanol NHA 99 1  2,4,6-Trimethylbenzyl alcohol VIO 98.5 1.5  2,4,6-Trimethylbenzyl alcohol HBT 99 1  2,4,6-Trimethylbenzyl alcohol NHA 100 0______________________________________ 
    
     EXAMPLE 17 
     213 mg (1.59 mmol) of 3-phenyl-2-propen-1-ol in 1.1 ml of ethanol were treated at 45° C. with stirring into 22 ml of buffer solution (see Example 1) with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole. After approx. 10 minutes, 5 ml of an aqueous solution of 2 mg/ml laccase from Trametes versicolor (specific activity approx. 18 IU/mg, defined with ABTS as the substrate) were added. After 3 hours in contact with the air, 48% of 3-phenyl-2-propenal were formed (GC analysis), and a further 24.3 mg of HOBT and 5 ml of laccase solution were added. GC analysis after 6 hours revealed complete conversion into 3-phenyl-2-propenal. 
     EXAMPLE 18 
     137 mg (1.59 mmol) of 3-methyl-2-buten-1-ol in 1.1 ml of ethanol were treated at 45° C. with stirring into 22 ml of buffer solution (see Example 1) with 24.3 mg (0.180 mmol) of 1-hydroxy-1H-benzotriazole. After approx. 10 minutes, 5 ml of an aqueous solution of 2 mg/ml laccase from Trametes versicolor (specific activity approx. 18 IU/mg, defined with ABTS as the substrate). After 3 hours in contact with the air, 52% of 3-methyl-2-butenal were formed, in addition to 24% of unreacted 3-methyl-2-butenal (GC analysis), and a further 24.3 mg of HOBT and 5 ml of laccase solution were then added. GC and NMR analysis after a total of 14 hours revealed complete conversion. 
     While several embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.