bluuebunny/crossref_metadata_2025 huggingface dataset:
The meta photocycloaddition of alkyl‐ and alkoxy‐substituted arenes to cyclopentene
Authors: de Vaal P. , Osselton E.M. , Krijnen E.S. , Lodder G. , Cornelisse J.
Published: September 2010

The meta photocycloaddition of alkyl‐ and alkoxy‐substituted arenes to cyclopentene has been investigated and the relative reactivity of each substituted arene towards the various modes of addition determined. The results are discussed and are shown to be compatible with a polar mechanism.
Quelques aspects de la chimie des dioxa‐ et dithia‐germoles
Authors: Lavayssière H. , Dousse G. , Satgé Et J.
Published: September 2010

Dithia‐ and dioxa‐germoles: R2Ge‐X‐CR′=CR′‐X (X = S, O), have been prepared from diorganodihalogermanes and R′(NaS)C=C(SNa)R′, 1,2‐benzenedithiol, α‐hydroxy ketones, R “(KO)C=C(OK)R” or dioxastannole and by cleavage of Ge‐N bonds of diorganobis(diethylamino)germanes by benzoin. The synthesis of spirobidithiagermoles is also reported.

The thermal stability of dithiagermoles has been studied. Decomposition occurs mostly by a [3 + 2] ring opening with formation of germathiones.

In the presence of tertiary amines, dioxagermoles lead to germylenes and α‐diketones through a [4 + 1] ring opening.

The chemical reactivity of dithia‐ and dioxa‐germoles has been studied. Exchange reactions with dihalogenated covalent compounds occur readily leading to carbon, phosphorus and sulfur dithiole and dioxole analogs. From dichlorogermylene new stable functional cyclic germylenes are obtained and characterized.
Tetrahedral intermediates formed during the nucleophilic addition‐elimination reaction of carbonyl‐containing compounds in the gas phase. Part I
Authors: van der Wel H. , Nibbering N. M. M.
Published: September 2010

The possibly reversible addition‐elimination reaction between CH3 18O−, CD3O−, 18O− • and D18O− and various carbonyl‐containing substrates has been studied in the gas phase using Fourier‐Transform Ion‐Cyclotron‐Resonance (FT‐ICR) Mass Spectrometry.

Reversible addition‐elimination is observed for the following nucleophile/substrate systems: CH318O− (CD3O−)/RCO2CH3 (R = CH3O, C6H5, t‐C4H9), 18O− • (H18O−)/CO2 and HO−/R′CH18O (R′ = C6H5, t‐C4H9).

The results obtained are discussed in relation to the formation of tetrahedral intermediates.
Directing photoinduced charge‐separation in linked donor‐acceptor systems by molecular engineering of the bridging group
Authors: Kroon J. , Verhoeven J. W. , Oliver A. M. , Paddon‐Row M. N.
Published: September 2010

Two bichromophoric systems (3 and 4) are studied that contain an electron donor (D) and an electron acceptor (A) moiety interconnected by a fully rigid, saturated hydrocarbon‐bridge. In both the shortest through‐bond pathway from D to A has a length of 8 sigma‐bonds, but whereas this path has an all‐trans configuration in 3, two cis elements have been introduced in 4. Photoinduced, intramolecular electron transfer from D to A occurs more than an order of magnitude faster across the stretched all‐trans bridge in 3 than across the bent bridge in 4 notwithstanding the smaller spatial distance in the latter.
Friedel‐Crafts alkylation of pyrene in carbon disulfide; 1H NMR spectroscopy of pyrene derivatives
Authors: Rodenburg L. , de Block R. , Erkelens C. , Lugtenburg J. , Cornelisse J.
Published: September 2010

Friedel‐Crafts alkylation of pyrene with 2,5‐dichloro‐2,5‐dimethylhexane and 2,4‐dichloro‐2,4‐dimethylpentane in carbon disulfide yields 7,7,10,10‐tetramethyl‐7,8,9,10‐tetrahydrobenzo[a]pyrene and 7J,9,9‐tetramethyl‐8,9‐dihydro‐7H‐cyclopenta[a]pyrene, respectively, both in 99% yield. Alkylation with 1,4‐dichlorobutane, followed by aromatization, yields benzo[a]pyrene in a facile two‐step synthesis in 8% yield. A mechanism is proposed which rationalizes the fact that only one ring of pyrene undergoes substitution. The 1H‐1H NMR coupling constants of the pyrene derivatives are discussed.
Organometallic complexes with chiral cyclometallated ligands. The synthesis of cycloplatinated complexes containing the (S) or (R)‐2‐NMe2C6H4CH(SiR3) (R = Me, Ph) monoanion. X‐Ray crystal and molecular structure of [PtCl[CH(SiMe3)C6H4‐2‐NMe2](Et2S)]
Authors: Wehman Erik , van Koten Gerard , Hardeman Gerard , Stam Casper H. , Pfeffer Michel
Published: September 2010

Cyclometallated platinum complexes of the monoanionic ligand 2‐NMe2C6H4CH(SiR3)− (R = Me, Ph; dmat‐SiR3−) have been synthesized via the reaction of the organolithium reagent with both [PtCl2(Et2S)2] and [PtCl2(Et2COD] (COD = 1,5‐cyclooctadiene). The 1:1 reaction of Li(dmat‐SiR3) with [PtCl2(Et2S)2] affords the mono‐alkylated platinum complexes [PtCl(dmat‐SiR3)Et2S]. The X‐ray crystal structure of one of these (R = Me) was determined. The platinum centre has a square‐planar geometry with a trans‐C‐Pt‐Cl arrangement and the chelate dmat‐SiMe3 ring has a conformation that places the bulky SiMe3 substituent out of the aryl ring plane. From the 2:1 reaction of Li(dmat‐SiR3) with [PtCl2(Et2S)2] no stable organoplatinum compound could be isolated. However with [PtCl2(Et2S)2COD] this 2:1 reaction affords complexes of [Pt(dmat‐SiR3)2COD] stoichiometry. These latter monomeric complexes contain one cyclometallated dmat‐SiR3 ligand and a COD ligand that, after having undergone an addition of the second dmat‐SiR3 ligand to one of its double bonds, is η2, η1−bound to the metal.
Asymmetric addition of methyllithium to di‐p‐tolylsulfine using chiral ligands
Authors: Rewinkel J. B. M. , Porskamp P. A. T. W. , Zwanenburg B.
Published: September 2010

The asymmetric addition of MeLi to di‐p‐tolylsulfine 1 in the presence of the chiral ligands (2S,2′S)‐2‐(hydroxymethyl)‐1‐[(1‐methylpyrrolidin‐2‐yl)methyl]pyrrolidine 2, (2S)‐2‐hydroxymethyl‐1‐methylpyrrolidine 4, (2S,2′S)‐2‐(methoxymethyl)‐1‐[(1‐methylpyrrolidin‐2‐yl) methyl]‐pyrrolidine 5 and (2S,2′S)‐2‐(1‐hydroxy‐1‐propylbutyl)‐1 ‐[(1‐methylpyrrolidin‐2‐yl)methyl]‐pyrrolidine 6 was investigated. The influence of the molar ratio of substrate, MeLi and ligand, of temperature and of solvents on the enantiomeric excess of the sulfoxide 3 was studied for ligand 2. The optical yield varied from 5‐55%. The highest enantiomeric excess (55%) for the sulfoxide 3 was obtained using ligand 2 (ratio sulfine 1/MeLi/ligand 2 = 1.0/6.7/4.0) in tetrahydrofuran at ‐ 78°C. The results are discussed by comparing them with the enantioselective addition of MeLi to aldehydes in the presence of the same ligands.
Phosphorylation of hydroxy groups via silylated intermediates
Authors: Montero Jean‐Louis , Toiron Catherine , Clavel Jean‐Louis , Imbach Jean‐Louis
Published: September 2010

Biologically interesting allylic phosphates have been prepared by a novel route starting from silylated alcools.
Syntheses, conformational analyses, X‐ray analyses and force‐field‐calculations of 7,8‐dihydrohexahelicene and 5,6‐dihydrohexahelicene
Authors: Prinsen W. J. C. , Laarhoven W. H. , Bosman W. P. , Behm H. , Beurskens P. T.
Published: September 2010

The photocyclization of 2‐styrylbenzo[c]phenanthrene (1) in n‐butylamine yields a mixture of hexahelicene (3) and two dihydrohexahelicenes (5 and 6). Both dihydrohexahelicenes could be isolated from the irradiation mixture as pure compounds by chromatography on a silica gel coated with R( ‐ )‐TAPA, a chiral stationary phase developed for the resolution of the enantiomers of hexahelicene (3). The NMR spectra of 5,6‐dihydrohexahelicene (5) and 7,8‐dihydrohexahelicene (6) exhibit remarkable differences in the aromatic region. These differences are attributed to the location of the alicyclic ring in the hexahelicene skeleton. The X‐ray structure analyses of the dihydrohexahelicenes 5 and 6 demonstrate that, in the crystalline state, both isomers occur in only one of two possible conformations. The NMR spectra of the two compounds lead to the conclusion that, in solution, the same conformation as in the solid state is highly preferred, although the existence of the second conformation cannot be completely excluded. Structural analyses by forcefield calculations corroborate this conclusion.
Benzotriazoles. Part 151: The preparation of 1‐(1‐alkenyl)benzotriazoles
Authors: Katritzky Alan R. , Offerman Rick J. , Cabildo Pilar , Soleiman Mohammed
Published: September 2010

The title compounds are prepared either (A) from 1‐(1‐chloroalkyl)benzotriazoles and aldehydes via Wittig reaction or (B) from 1‐[1,1‐bis(trimethylsilyl)alkyl]benzotriazoles by alkylative desilylation by fluoride ion in the presence of a carbonyl compound (in one instance by lithiation of the silyl compound and subsequent reaction with a carbonyl electrophile) via a Peterson olefination. The methods are applicable to both alkyl and aryl ketones and to aldehydes, with method (B) giving the highest yields.
On the intermediacy of phenyl hydrogen sulfates in the sulfonation of phenols. Sulfonation of phenol, anisole, methyl phenyl sulfate, the 2‐halogenophenols, a series of phenyl methanesulfonates together with 2,6‐dimethylaniline and its N‐methylsulfonyl derivative
Authors: de Wit Peter , Woldhuis Alex F. , Cerfontain Hans
Published: September 2010

The sulfonation of methyl phenyl sulfate (4) with concentrated aqueous sulfuric acid at 25°C yields the 4‐sulfonic acid. This initial product then decomposes to give phenol‐4‐sulfonic acid, which is subsequently sulfonated to phenol‐2,4‐disulfonic acid. From the first‐order‐rate coefficients obtained for sulfonation of phenyl methanesulfonate (3) and (4) in 93.2% H2SO4, for which acid concentration the sulfonating entity is H2S2O7, the σp+ values of the OSO2Me and OSO2OMe substituents have been determined to be 0.40 and 0.46, respectively. The sulfonation of both 2‐chlorophenyl (10) and 2‐methylphenyl methanesulfonate (14) with 2.0 equiv of SO3 in nitromethane at 0.0°C yields the 4‐sulfonic acid as the exclusive product, whereas 2‐methoxyphenyl methanesulfonate (13), under the same conditions, forms exclusively the 5‐sulfonic acid.

2‐Chloro‐ (6), 2‐bromo‐ (7) and 2‐iodophenol (8) with 1.0 and 4.0 equiv of SO3 in nitromethane yield exclusively the 4‐sulfonic acid, while 2‐fluorophenol (5) with 2.0 and 5.0 equiv of SO3 yields in addition the 5‐sulfonic acid to the extent of 4 and 30%, respectively.

In the reactions of 2,6‐dimethylphenol (15) and 2,6‐dimethylaniline (17) with at least 1 equiv of SO3 in nitromethane, the 3‐SO3H/4‐SO3H ratio was found to increase on increasing the relative amount of SO3. For both 15 and 17, the limiting 3‐SO3H/4‐SO3H ratio at high SO3/ArOH ratios is 86/14 and this value is considered to be the ratio for the sulfonation of both 2,6‐dimethylphenyl hydrogen sulfate and 2,6‐dimethylaniline‐N‐sulfonic acid. This assumption is supported by the observation that the sulfonation of 2,6‐dimethylphenyl methanesulfonate (16) and N‐(methylsulfonyl)‐2,6‐dimethyl‐aniline (18) with SO3 leads to a similar 3‐SO3H/4‐SO3H ratio.
Synthesis of 3‐aryl‐1‐naphthalenamines
Authors: Selvaraj S. , Ramakrishnan P. S. , Arumugam N.
Published: September 2010

1‐(Hydroxyimino)‐3‐aryl‐1,2,3,4‐tetrahydronaphthalenes, when subjected to Semmler‐Wolff reaction using Beckmann's mixture, give hitherto unknown 3‐aryl‐1‐naphthalenamines, which have been characterised using elemental analyses and spectral data.
Synthesis of several sulphated and non‐sulphated pentasaccharides, corresponding to the E. coli K5 glycosaminoglycan
Authors: Kraaijeveld N. A. , van Boeckel C. A. A.
Published: September 2010

The synthesis is described of four pentasaccharides, which are structurally related to the bacterial capsular polysaccharide isolated from E. coli K5 (010/K5/H40), i.e. the so‐called K5 antigen.

These four synthetic compounds comprise:

(i) a pentasaccharide that is structurally identical to the K5 antigen (i.e. compound 16);

(ii,iii) two pentasaccharides containing two and three O‐sulphated groups respectively on defined positions (i.e. compounds 15a and 15b);

(iv) a pentasaccharide that is O‐sulphated on all hydroxyl groups (i.e. compound 17). These four K5‐antigen‐related pentasaccharides were synthesized from the fully protected pentasaccharides 13a and 13b. The preparation of compounds 13a,b was based on coupling of disaccharide 6b with the disaccharide 10a or 10b to give tetrasaccharides 11a,c, respectively, which in turn were coupled to monosaccharide 12. Deblocking of the pentasaccharides 13a,b and conversion into the pentasaccharides 15a and 15b was performed by saponification of the ester functions, O‐sulphation, hydrogenolysis and finally selective N‐acetylation. Compound 16 was obtained from 13a,b by saponification of the ester functions, deblocking of the benzyl and N‐protective groups, followed by selective N‐acetylation. The persulphated derivative 17 was obtained from 15a by extensive O‐sulphation. The structure of the K5‐antigen‐related pentamers was confirmed by 1H NMR‐ and 13C NMR‐spectroscopical techniques.
Synthesis and spectroscopic study of 13C‐labelled citric acids
Authors: Winkel C. , Buitenhuis E. G. , Lugtenburg J.
Published: September 2010

The synthesis of (1′‐13C)‐, (3‐13C)‐ and (2,4‐13C2)citric acid from simple starting compounds is described. Using the same procedure, any mono‐ or multiply‐labelled citric acid can be prepared.

The 13C‐labelled citric acids have been characterized by 1H NMR, 13C NMR and mass spectroscopy.
A general coordination‐ionization scheme for polyhydroxy carboxylic acids in water
Authors: van Duin M. , Peters J. A. , Kieboom A. P. G. , van Bekkum H.
Published: September 2010

The structural changes of coordination compounds of polyhydroxy carboxylic acids as a function of the pH are discussed. A general coordination‐ionization scheme, based on literature data and covering some forty cations, is provided. The following trend is observed on going from low to high pH: (i)bidentate coordination of the cation by the α‐hydroxy carboxylic acid moiety, (ii) ionization of the carboxylic acid function, (iii) ionization of the α‐hydroxyl group and (iv) coordination by an ionized‐diol function. For complexes of metal ions, the pH effects are correlated with the acidity of the hydrated cation and explained using an extended electrostatic model. The coordination‐ionization scheme provides an explanation for and allows prediction of both metal‐ion‐catalyzed addition reactions and synergetic effects in sequestering agents.
A novel one pot synthesis of substituted 1‐oxo‐1,2,4,6‐thiatriazinium salts
Authors: Tashtoush Hasan , Al‐Talib Mahmoud
Published: September 2010

N‐Chlorosulfinyl diarylketimine reacts with Lewis acids to give an orange precipitate of l‐oxa‐2‐thia‐3‐azabutatrienium salts. The latter compounds readily react with two equivalents of dialkylcarbodiimides to afford good yields of l‐oxo‐1,2,4,6‐thiatriazinium salts, 3.
The “tert‐amino effect” in heterocyclic chemistry: Synthesis of 3,1‐benzoxazines and 3,1‐benzothiazines
Authors: Nijhuis W. H. N. , Verboom W. , Reinhoudt D. N. , Harkema S.
Published: September 2010

Two different routes are described for the synthesis of the 2,2,2‐trifluoro‐l‐[2‐(dialkyl‐amino)phenyl]ethanones 2 and 9 and their hydrates 3 and 10, respectively, via trifluoroacetylation of the N,N‐dialkylanilines 1 and via a Barbier reaction of 2‐fluorobenzaldehyde. These compounds were thermally converted into a mixture of cis‐ and trans‐pyrrolo‐ and pyrido[1,2‐a] [3,1]benzoxazines, (11: cis; 12: trans). The structure of these compounds was proven by X‐ray analysis (11a) and 1H NOE difference spectroscopy. Cyclization of (R)‐9b (R1 = CH3) gave predominantly one enantiomer (12f, 70%) and in addition two diastereomers of 17a and two of 18a (total yield ≈︁ 17%), while cyclization of (S)‐9c (R1 = CH2OCH3) gave a mixture of 12g (18%), two diastereomers of 17b (36%) and two diastereomers of 18b (18%). The benzaldehyde 19a (R3 = H), acetophenone 19d (R3 = CH3), trifluoroacetophenones 19b,c (R3 = CF3) and benzophenone 19e (R3 = C6H5) reacted with Lawesson's reagent to yield exclusively the trans‐pyrrolo[1,2‐a] [3,1]benzothiazines 21a‐e in yields of 33‐77%. Reaction of 19f (R1 = CH3, R3 = H), 19g (R1 = CH3, R3 = CF3) and 19h (R1 = CH3, R3 = CH3) with Lawesson's reagent resulted in the formation of mixtures of isomers 21‐24.
pH dependence of the stability of boric acid and borate esters of amino acids and amino diols in aqueous medium as studied by 1B and 1H NMR spectroscopy
Authors: van Haveren J. , Peters J. A. , Batelaan J. G. , Kieboom A. P. G. , van Bekkum H.
Published: September 2010

11B and 1H NMR spectroscopy studies have revealed that the apparent association constants for borate esters of 2‐amino 1,3‐diols are pH dependent, whereas such a pH dependence is not found in the case of methyl‐substituted diols or 3‐amino‐1,2‐propanediol. These studies have also shown that boric acid ester formation can be detected using 11B NMR.
Effect of pH on the epoxidation of alkenes by the cytochrome P‐450 model manganese(III) porphyrin/hypochlorite
Authors: van der Made A. W. , Bax J. M. C. , Nolte R. J. M. , Drenth W.
Published: September 2010

The epoxidation of alkenes by hypochlorite catalysed by manganese(III) tetraarylporphyrins in a two‐phase water/dichloromethane system is accelerated by lowering the pH of the aqueous phase. This effect is explained by a faster formation of the active [(P)MnO]+ species from a (P)MnOCl complex for all types of porphyrin catalysts and additionally by a suppression of dimerization phenomena for non‐sterically hindered catalysts.
A cage compound derived from cyclotriveratrylene and diphenylglycoluril sub‐units
Authors: Smeets J. W. H. , Coolen H. K. A. C. , Zwikker J. W. , Norte R. J. M.
Published: September 2010

To diphenylglycoluril (2), four aliphatic chains were attached, each with a vanillyl alcohol group at the end. In an acid‐catalyzed reaction, three of the vanillyl alcohol groups cyclize to form a cyclotriveratrylene unit. The resulting compound (3) has a well‐defined cavity and a free, functionalized arm. Cyclization of four vanillyl alcohol groups (5) does not occur, probably for steric reasons.
Benzylation of sugar polyols by means of the PTC method
Authors: Szeja W. , Fokt I. , Grynkiewicz G.
Published: September 2010

Studies on benzylation of hydrophilic carbohydrate derivatives with benzyl chloride, using a phase‐transfer technique, have led to the conclusion that alkylation of a substrate can be greatly facilitated by the introduction of a “co‐catalyst” (e.g. a tertiary alcohol) and/or a co‐solvent (e.g. DMSO) to the reaction mixture. Efficient procedures for benzylation of sugar derivatives having three to eight hydroxyl groups per molecule, in a two‐phase system employing an almost stoichiometric amount of the alkylating agent, are presented.
Studies of relaxation times in three substituted acetophenones in benzene
Authors: Khanna R. K. , Bhatnagar Abha , Jain Subhash
Published: September 2010

Measurements of the static dielectric constant at 10 KHz, the refractive index (using a sodium light) and the complex dielectric constant at 9.34 GHz have been made for three substituted acetophenones in a dilute solution of benzene over the temperature range 30‐60 °C. Dielectric relaxation times τ(1) and τ(2) have been calculated using the single‐frequency concentration‐variation method as suggested by Higasi. Comparison with a few available results indicates that τ(2) leads to relaxation times for overall molecular rotation, whereas τ(1) becomes an explicit function of both inter‐ and intramolecular‐relaxation times. τ(2), as well as the distribution parameter (α), show a systematic decrease with increase in temperature. Values of the dipole moments are also reported for these acetophenones.
A convenient one‐pot synthesis of bis(trimethylsilyl)hexatriyne: A precursor of an organic superconductor?
Authors: Alberts Albert H.
Published: September 2010

A medium‐scale one‐pot synthesis of bis(trimethylsilyl)hexatriyne is described and the potential of this compound as a precursor of an organic superconductor (the “Little model)” is discussed.
An expeditious in situ preparation of benzyl (S)‐2‐aziridinecarboxylate
Authors: Kuyl‐Yeheskiely E. , Dreef‐Tromp C. M. , van der Marel G. A. , van Boom J. H.
Published: September 2010

The use of diethoxytriphenylphosphorane in the preparation of benzyl (S)‐2‐aziridinecarboxylate is illustrated. The latter compound has been coupled with Z‐Ala‐OH and the aziridine dipeptide thus obtained ring‐opened via C‐3‐N‐1 cleavage with benzyl alcohol and ethanethiol to afford Z‐Ala‐Ser(Bzl)‐OBzl and Z‐Ala‐Cys(Et)‐OBzl, respectively.
Synthesis of benzo(ij)cycl[3.3.2]azines via a palladium mediated cyclisation reaction
Authors: Pfeffer Michel , Rotteveel Marc A.
Published: September 2010

A convenient one step synthesis of tetrasubstituted benzo(ij)cycl[3.3.2]azines is performed through the reactions between disubstituted alkynes and cyclopalladated 8‐methylquinoline species.
Partial characterization of the N‐linked oligosaccharides occurring on rat hepatocyte glycoproteins
Authors: Bierhuizen Marti F. A. , de Wit Moniek , Govers Carin A. R. L. , van Dijk Willem
Published: September 2010

Primary monolayers of isolated rat hepatocytes were cultured in the presence of [2‐3H]mannose and [1‐14C]fucose to label metabolically the carbohydrate portion of glycoproteins. Subsequently, glycopeptides were prepared by extensive pronase digestion in order that the relative occurrence of N‐linked oligosaccharides could be examined by lectin‐agarose affinity chromatography.

The results indicate that isolated rat hepatocytes are able to synthesize many of the N‐linked oligosaccharides known to be present in whole‐rat‐liver tissue and in rat‐serum glycoproteins. Differences were noticed, however, in the relative occurrence of N‐linked glycans and their degree of galactosylation. Biantennary complex‐type glycans were predominant in isolated rat hepatocytes, whereas the majority of the N‐linked complex‐type glycans in rat‐liver tissue glycoproteins has been reported to be of the tetraantennary type. Furthermore, the degree of P‐galactosylation of the glycans of the hepatocytes appeared to be substantially lower than reported for the peripheral branches of liver tissue complex‐type glycans. However, most of the P‐linked Gal residues present appeared to be substituted by sialic acid.
Studies directed towards the synthesis of sulphated and non‐sulphated glyco‐conjugate fragments using insoluble silver‐salt promoters
Authors: Spijker N. M. , Zuurmond H. , Westerduin P. , van Boeckel C. A. A.
Published: September 2010

The synthesis of three fucosylated oligosaccharides (i.e. compounds 8, 10 and 14) and a keratan sulphate fragment (i.e. compound 24) is presented. The formation of β bonds in these glyco‐conjugate fragments was promoted by insoluble silver salts, while non‐participating groups are present at C‐2 of the glycosyl bromide. Thus, glycosyl donors can be used which have also been employed for a glycoside synthesis. It was found that insoluble silver salt promoters can be very worthwile for the formation of β bonds in larger oligosaccharides when relatively reactive glycons with suitable substitution pattern are condensed with reactive aglycons. The application of this coupling methodology is of special advantage for the synthesis of functionalized oligosaccharides (such as 24), which synthesis may require the use of building blocks having non‐participating (e.g. benzyloxy or azido) protecting groups at C‐2.
Synthesis of (+)‐sesbanimide a. Structure of the crucial silyl ether AB ring intermediate
Authors: Vloon W. J. , van den Bos J. C. , Willard N. P. , Koomen G.‐J. , Pandit U. K.
Published: September 2010

Attempts to protect the 8‐hydroxy group (sesbanimide numbering) of the AB ring intermediate 2a, derived from D‐xylose, by tert‐butyldiphenylsilyl trifluoromethanesulfonate, led unexpectedly to the formation of a novel 2‐O‐silyl derivative possessing a tricyclic structure. This intermediate has been converted into (+)‐sesbanimide A.
The use of histidine decarboxylase for the isolation of D‐histidine from the racemate
Authors: Foppen Marie‐Anne E. , van Rantwijk Fred , Maat Leendert , Kieboom Antonius P. G.
Published: September 2010

A procedure has been developed for the straightforward isolation of enantiomerically pure D‐histidine from the racemate by action of histidine decarboxylase (EC 4.1.1.22) on racemic histidine followed by crystallization. The histamine formed has been isolated as its dipicrate from the mother liquor.
2‐alkoxy‐3‐methylenetetrahydrofurans by addition of 2‐(bromozincmethyl)‐3,3‐dialkoxy‐1‐propenes to aldehydes and ketones followed by Pd(0)‐catalyzed cyclization
Authors: van der Louw J. , van der Baan J. L. , Timmerman P. , de Kanter F. J. J. , Bickelhaupt F. , Klumpp G. W.
Published: September 2010

Reaction of 2‐(bromozincmethyl)‐3,3‐dialkoxy‐1‐propenes 2 with aldehydes and ketones afforded addition products 4 which underwent Pd(0)‐catalyzed cyclization to 2‐alkoxy‐3‐methylenetetrahydrofurans 5.
The Hurtley reaction III. A reactivity study of copper(I) 2‐halobenzoates either as pure reagents, or under Hurtley reaction conditions, and as a part of mixed (benzoato)(mesityl)copper(I) clusters
Authors: Aalten Henk L. , van Koten Gerard , Vrieze Kees , van der Kerk‐van Hoof Anca
Published: September 2010

The reactivity of pure isolated copper(I) 2‐halobenzoates has been studied at 20 and 80 °C either with or without oxidizing agents (O2 and CuBr2). Furthermore, these complexes have been reacted at 80°C either alone or in combination with sodium acetylacetonate, i.e. under “Hurtley reaction conditions”. Corresponding reactivity of the mixed (2‐halobenzoato)(mesityl)copper(I) clusters, wherein the mesityl fragment can be considered as an intramolecularly bonded nucleophile, has also been studied.

The organic products of these reactions and their distribution, measured by combined gas chromatography‐mass spectrometry (GC–MS) and gas–liquid chromatography (GLC), for both types of reactions showed remarkable similarities. The principal products of these reactions, e.g. biaryls, methyl 2‐(1‐acetyl‐2‐oxopropyl)benzoate and 2‐mesitylbenzoate derivatives, are formed by a halogen substitution reaction. Compared to the chlorobenzoate derivatives, the more reactive bromo species generate more by‐products. The presence of a coordinating solvent, such as acetylacetone, proved to be necessary in order to obtain a good yield from the condensation reaction between the copper(I) 2‐halobenzoates and sodium acetylacetonate. A detailed mechanism involving dinuclear copper(I) intermediates is proposed for the Hurtley reaction.
Hydrolysis of 2,4‐dinitrophenyl phosphate catalyzed by single‐chain, twin‐tailed and bolaform surfactants
Authors: Bunton Clifford A. , Dorwin Ellen L. , Savelli Gianfranco , Si Victoria C.
Published: September 2010

The spontaneous hydrolysis of 2,4‐dinitrophenyl phosphate dianion (2,4‐DNPP) is speeded by cationic micelles of cetyltrimethylammonium salts [CTAX, X = Cl, Br, (SO4)0.5] and of bolaform(22)X2 [Me3N+ (CH2)nN+ Me3 2X−, n = 22, X = Br, (SO4)0.5]. The shorter‐chain bolaform surfactants (n = 16, 12, X = Br) are less effective. Twin‐chain surfactants of didodecyl and dicetyldimethylammonium salts (C12H25)2NMe2X, X = Br, Cl, (SO4)0.5 and (C16H33)2NMe2X, X = Cl, (SO4)0.5 and pyridinium‐ion surfactants C16H33NC5H5Cl and its 4‐(dimethylamino) derivative, also speed hydrolysis. The first‐order rate constants increase to limiting values (k′M) when substrate is fully bound and these values are not very sensitive to the nature of the surfactant and are generally greater than in water by factors of 20–110. However, the extent of binding of 2,4‐DNPP is sensitive to the nature of the surfactant. Tertiary amines, e.g., pyridine and DABCO speed the reaction in CTACl by generating an intermediate phosphoramidate.
Hysteresis during CO‐oxidation activity measurements on carbon‐supported copper/chromium catalysts
Authors: Stegenga S. , Dekker N. J. J. , van Soest R. , Kapteijn F. , Moulijn J. A.
Published: September 2010

Carbon‐supported catalysts containing Cu and Cr are active in oxidation and reduction reactions. In CO oxidation experiments, an activity hysteresis has been observed for the Cu/Cr‐carbon catalyst during temperature cycling. From results of CO oxidation experiments and Temperature‐Programmed Reduction (TPR) in CO of fresh, pre‐reduced and pre‐oxidized samples, it is concluded that an oxidation–reduction cycle of the active phase is the reason for this hysteresis phenomenon. Furthermore, TPR(CO) reveals the presence of highly active oxygen species on a Cu/Cr catalyst, which might be the reactive intermediate in CO oxidation. It is also shown that the active phase catalytically oxidizes the carbon support, resulting in a high TPR(CO) background.
The photochemical rearrangement of 1,2‐dihydronaphthalenes into 1,4‐dihydronaphthalenes induced by amines
Authors: Cuppen Th. J. H. M. , Berendsen N. , Laarhoven W. H.
Published: September 2010

The synthetic usefulness of the deprotonation/protonation reaction of excited 1,2‐dihydronaphthalenes into 1,4‐dihydronaphthalenes induced by amines has been investigated using 13 different substituted 1,2‐dihydronaphthalenes and related compounds. The yield of the rearrangement ranges from 5 to 96%. The formation of side‐products depends on the position of protons in the substrate, which can be abstracted by the amine, and on competitive photoreactions.
Polyamides and polyesters containing 2,4:3,5‐di‐O‐methylene‐L‐idaroyl residues
Authors: Tinnemans A. H. A. , Budding H. A. , Stein F. , Venekamp J. C.
Published: September 2010

Electrochemical oxidation of 2,4:3,5‐di‐O‐methylene‐D‐gluconic acid in strong alkaline medium afforded a mixture of 2,4:3,5‐di‐O‐methylene‐D‐glucaric acid 4 and 2,4:3,5‐di‐O‐methylene‐L‐idaric acid 1 in a 1/8 ratio with a current efficiency of 53%. Force‐field calculations using Allinger's molecular mechanics program MM2p85 on 1 and 4 indicate that these cis‐fused tetrahydro‐[1,3]dioxino[5,4‐d]‐1,3‐dioxin ring systems possess an O‐inside conformation with a steric energy of 110.3 and 123.5 kJ·mol−1, respectively. Their conformation was confirmed by 400‐MHz 1H‐ and 100‐MHz 13C NMR measurements.

A series of polycondensates were prepared by homogeneous solution polymerisation of 1 with an aromatic diol or aromatic diamine, which were analyzed by DSC and TGA.
Metal‐Metal interactions in indium(I) and thallium(I) cyclopentadienyls
Authors: Budzelaar Peter H. M. , Boersma J.
Published: September 2010

The short metal‐metal contacts frequently observed in solid indium(I) and thallium(I) cyclopentadienyls are interpreted as weak donor‐acceptor interactions, similar to the Sn‐Sn bond in dimeric stannylenes.
On the chemistry of binding sites VII. Enantioselective binding using chiral boronic acids
Authors: Wulff Günter , Stellbrink Heike
Published: September 2010

For the construction of chiral binding sites in chromatography, various phenylboronic acids have been prepared as model substances carrying, in the ortho (3a‐d) or ortho, ortho position (4a‐d), optically active side‐groups containing basic nitrogen atoms. The compound carrying two prolyl residues shows the highest selectivity in chiral recognition of racemic diols (separation factor α between 1.70‐2.25). Separation occurs via the formation of a cyclic boronic diester of the diol. The thermodynamic properties of this esterification reaction are well suited to chromatography and furthermore the reaction seems to be adequately rapid.
Synthesis and characterization of μ‐cyano(octaethylporphyrinato)cobalt(III)
Authors: Fahmy Naglaa , Hanack Michael
Published: September 2010

(Octaethylporphyrinato)cobalt(II), OEPCo (1), reacts with sodium cyanide and undergoes simultaneous oxidation with air oxygen to form sodium dicyano(octaethylporphyrinato)‐cobalt(III), Na[OEPCo(CN)2] (2), which is converted into μ‐cyano(octaethylporphyrinato)‐cobalt(III), [OEPCoCN]n (3), in aqueous medium. Compounds 2 and 3 are chatacterized by IR, 1H NMR, UV/VIS, TG/DTA and mass spectroscopy. Treatment of the oligomer 3 with pyridine leads to the monomeric complex OEPCoCN(py) (4).
CO2 hydrogenation on nickel based catalysts supported on alumina
Authors: Ghazi M. , Menezo J. C. , Barrault J.
Published: September 2010

On nickel‐alumina catalysts, the hydrogenation of carbon dioxide into methane is more rapid than that of carbon monoxide due to much slower de‐activation of the catalysts in the presence of the mixture (CO2 + H2). Under the same conditions, competitive hydrogenation of CO and CO2 leads to intermediate results which are, nevertheless, close to those obtained with the mixture (CO + H2) due to significant CO adsorption.
Synthesis and NMR‐spectral characterization of N,N‐dialkyl‐3‐nitroanilines, N,N‐dialkyl‐1,3‐benzenediamines and their acyl derivatives
Authors: Katritzky Alan R. , Rachwal Bogumila , Rachwal Stanislaw
Published: September 2010

A recently discovered method for the synthesis of N,N‐dialkyl‐1,3‐benzenediamines with two different alkyl groups is shown to be general. This is demonstrated by the synthesis of N‐butyl‐N‐phenethyl‐1,3‐benzenediamine by the condensation of 3‐nitroaniline with phenyl‐acetaldehyde and benzotriazole, reduction of the adduct with sodium borohydride, acylation of the resulting N‐phenethyl‐3‐nitroaniline with butyryl chloride, catalytic reduction of the nitro group by formic acid in the presence of triethylamine and palladium and finally reduction of the butyramide carbonyl group to the butyl substituent by lithium aluminum hydride. Several other routes were less efficient or failed completely.

Classical methods for the synthesis of N,N‐diethyl‐1,3‐benzenediamine were reexamined and improved. The recommended procedure involves alkylation of 3‐nitroaniline with diethyl sulfate, trapping of N‐ethyl‐3‐nitroaniline (by‐product) by benzoylation, distillation of N,N‐diethyl‐3‐nitro‐aniline under reduced pressure and reduction of the nitro group by formic acid catalyzed by palladium.
A Static‐Secondary‐Ion‐Mass‐Spectrometry study of the surfaces of poly(hydroxyalkyl methacrylates) before and after chemical modification
Authors: Lub J. , van der Wei H. , van Vroonhoven F. C. B. M. , Benninghoven A.
Published: September 2010

Positive and negative secondary‐ion‐mass spectra of poly(2‐hydroxyethyl methacrylate), poly(2‐hydroxypropyl methacrylate) and both polymers after modification with D2O and propionyl chloride are presented. The spectra were obtained with a Time‐of‐Flight Secondary‐Ion‐Mass Spectrometer. The structures of typical ions in the mass range 10‐150 amu are given and the intensities of these ions were used to obtain quantitative information about the ion formation processes. Furthermore, the spectra of poly(2‐hydroxyethyl methacrylate), poly[2‐(propionyloxy)ethyl methacrylate] and four copolymers of 2‐hydroxyethyl methacrylate and 2‐(propionyloxy)ethyl methacrylate are compared to provide quantitative results on ion‐formation efficiency and/or stability. The results of this study can be used to study the kinetics of the reaction of propionyl chloride with poly(2‐hydroxyethyl methacrylate) at a surface.
Synthesis and spectroscopy of (14′‐13C)‐ and (15′‐13C)spheroidene
Authors: Gebhard R. , van der Hoef K. , Lefeber A. W. M. , Erkelens C. , Lugtenburg J.
Published: September 2010

The preparation of two13C‐labelled isotopomers of spheroidene, the carotenoid bound in the photosynthetic reaction center ofRhodobacter sphaeroides, is described.All‐E(14′‐13C)‐spheroidene has been synthesized in high yield and purity and with more than 98%13C incorporation starting from (2‐13C)acetonitrile; similarly, all‐E(15′‐13C)spheroidene has been obtained starting from (I‐13C)acetonitrile. The spectroscopic properties of all‐Espheroidene and its (14′‐13C)‐ and (15′‐13C)isotopomers are discussed. The mass spectra of the labelled compounds reveal that toluene is eliminated mainly from the central part of the molecule. Analysis of the ′H‐NMR spectrum of all‐E(15′‐13C)spheroidene gives a value of 14.0 Hz for the1H ‐1H coupling constant of the 15‐15′ double bond.
Synthesis, molecular structure, and complexation of 1,4‐dihydropyridines containing ligands for intramolecular complexation of metal electrophiles
Authors: Kaptein Bernard , Kellogg Richard M. , van Bolhuis F.
Published: September 2010

A series of 4‐substituted Hantzsch 1,4‐dihydropyridines has been synthesized. Substituents at the 4‐position include 2‐pyridyl, 2‐imidazolyl, and 1‐methyl‐2‐imidazolyl. By use of various acetoacetic ester derivatives methoxy and methylthio groups have been introduced in the ester side chains at the 3,5‐positions. A representative example is bis(2‐methoxyethyl) 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5h). The crystal structure of bis‐[(2‐methylthio)ethyl] 1,4‐dihydro‐2,6‐dimethyl‐4‐(1H‐imidazol‐2‐yl)‐3,5‐pyridinedicarboxylate (5i) has been determined. The imidazole group at the 4‐position is located in a pseudo‐axial position. In the13C‐ and1H‐NMR spectra line doubling is seen in the 4‐imidazole‐substituted derivatives. This is apparently the result of slow tautomerization. Various complexes with Zn(NO3)2· 4H2O have been prepared but no crystal structures could be obtained. These 1,4‐dihydropyridines have little capacity, either in the presence or absence of metal ions, to carry out reductions. This may be the result of a stereoelectronic effect caused by the (presumably) equatorial orientation of the hydrogen (hydride) to be donated.
Alkaline decarboalkoxylative cyclization in the preparation of antirihine analogues
Authors: Lounasmaa Mauri , Jokela Reija
Published: September 2010

Alkaline decarboalkoxylative cyclization of 1.4.5.6‐tetrahydropyridine 3b does not lead to dl‐18‐nor‐18,19‐dihydroantirhine 1b [C(3)H‐C(15)H trans relationship] but to the corresponding 3‐epi analogue 2b [C(3)H‐C(15)H cis relationship].
Synthesis and photoreactions of some spiro[cycloalkanephenalenes]
Authors: Hempenius M. A. , Lugtenburg J. , Cornelisse J.
Published: September 2010

Reaction of the phenalenyl anion (1−) with 1,2‐dibromoethane, 1,4‐dibromobutane and 1,5‐dibromopentane results in the formation of (bromoalkyl)phenalene derivatives. These derivatives undergo ring closure when treated with base to spiro[cyclopropane‐1,1′‐[1H]phenalene] (2), spiro[cyclopentane‐1,1′‐[1H]phenalene] (4) and spiro[cyclohexane‐1,1′‐[1H]phenalene] (5). Reaction of 1− with 1,3‐dibromopropane gives a 1:1 mixture of 1,2,3,5‐tetrahydropyrene (3a) and 1,2,3,6‐tetrahydropyrene (3b), both of which can easily be dehydrogenated to pyrene.

Photochemical reactions of spiro[cycloalkanephenalenes] 2, 4 and 5 are discussed. The introduction and photochemical opening of a spirocyclopropane ring in phenalene results in the formation of 1,2‐dihydro‐4H‐cyclopenta[cd]phenalene (6), a compound with a fused five‐membered ring. The construction of pyrene and cyclopenta[cd]phenalene skeletons starting from phenalene represents a new approach in the synthesis of polycyclic aromatic hydrocarbons and their derivatives.
Unprecedented ring cleavage in the reaction of 1‐methyl‐3‐phenacyl benzimidazolium ylide with diethyl azodicarboxylate
Authors: Sepúlveda‐Arques José , Arbiol Eva Romero , González Rosende M. Eugenia , Lápez‐Rodriguez Matias , Afonso Ricardo Pérez
Published: September 2010

The reaction with diethyl azodicarboxylate (DEAZD) of different cycloimmonium ylides derived from pyridinium, quinolinium, isoquinolinium and 1‐methylbenzimidazolium bromides (3, 4, 5 and 6) yielded 3‐substituted tetraazapentenes (2). In the special case of 1‐methyl‐3‐phenacyl‐benzimidazolium bromide (6a), the ring cleavage compound N‐[1‐[(ethoxycarbonyl)amino]‐2‐oxo‐2‐phenylethylidene]‐N‐formyl‐N‐methyl‐1,2‐benzenediamine (7a) was obtained. Its structure was established by X‐ray crystallography.
A convenient iodonium‐ion‐assisted synthesis of an immunologically active tetrameric β (1→5)‐linked D‐galactofuranoside from the extracellular polysaccharide of Aspergillus and Penicillium species
Authors: Zuurmond H. M. , van der Klein P. A. M. , Veeneman G. H. , van Boom J. H.
Published: September 2010

The non‐terminal glycosyl donor, ethyl 2,3‐di‐O‐benzoyl‐5‐O‐(chloroacetyl)‐6‐O‐pivaloyl‐1‐thio‐α‐D‐galactofuranoside, could be used, with the promoter N‐iodosuccinimide and catalytic trifluoromethanesulfonic acid, for the preparation of β‐D‐Galf‐(1→5)‐β‐D‐Galf‐(1→5)‐β‐D‐Galf‐(1→5)‐β‐D‐Galf‐OMe.
Tuning of tantalum alkylidene reactivity with a terdentate aryl amine ligand: Synthesis, structure and reactivity of [TaCl2{C6H3(CH2NMe2)2‐2,6}(CHBut)]
Authors: Abbenhuis Hendrikus C. L. , Grove David M. , van Koten Gerard , van der Sluis Paul , Spek Anthony L.
Published: September 2010

The terdentate aryldiamine ligand in the aryltantalum(V) alkylidene complex [TaCl2{C6H3(CH2NMe2)2‐2,6}(CHBut)] (1) controls alkylidene reactivity in a range of metal‐mediated Wittig reactions. An X‐ray diffraction study of (1) shows that the hexacoordinate tantalum centre has a very irregular ligand array in which the aryldiamine ligand adopts a new facial N,C,N coordination mode.
Substituent effects. 13. Anomalous dissociation constants in water‐organic solvent mixtures: Alicyclic and aliphatic carboxylic acids
Authors: Hoefnagel A. J. , Wepster B. M.
Published: September 2010

The effects on pK of 3‐, 4‐, and 3,5‐(di)alkyl groups in all‐equatorial cyclohexane‐carboxylic acids are examined in detail. They show quantitatively the same anomalies as in the benzoic acids. Similar characteristics have been found for cyclohexanecarboxylic acids with carboxyl axial, for cyclohexaneacetic acids, β‐tert‐butylpropionic acid, γ‐tert‐butylbutyric acid, and trans‐2‐(trimethylsilyl)cyclohexanecarboxylic acid. Substituent effects from the 2 and α positions usually show the presence of additional factors.
Photochemistry of α‐oxo oximes. Part 10: Photochemistry of three cyclic α‐oxo oxime methyl ethers and their acyclic analogue at λ 254 nm
Authors: Buys Theo S. V. , Cerfontain Hans , Geenevasen Jan A. J. , Stunnenberg Frank
Published: September 2010

The (E)‐ and (Z)‐isomers of the 3,3,n,n‐tetramethyl‐2‐(methoxyimino)‐1‐cycloalkanones (n = 5 to 7) (3a‐c) and their acyclic analogue (Z)‐4‐(methoxyimino)‐2,2,5,5‐tetramethyl‐3‐hexanone [(Z)‐4] have been irradiated at λ 254 nm in acetonitrile as solvent in order to study the influence of ring size on product formation. The dependence of product composition on irradiation time revealed that the (E)‐isomers of 3a‐c undergo both E‐Z isomerization and photodecomposition, whereas the (Z)‐isomers undergo only Z‐E isomerization. The primary step in photodecomposition is homolysis of the NO bond. The observed products result from the various possible reactions of initially formed methoxy and cyclic iminyl radicals 17, cyanoacyl radicals 18 formed by ring opening of 17, cyanoalkyl radicals 19 formed from 18 by decarbonylation and cyclopentaniminyl radical 20b, formed by cyclization of the 5‐cyano‐2‐hexyl radical 19b. Mechanisms for the formation of the various products are proposed and the relative importance of the various steps is discussed, also in relation to the results obtained using carbon tetrachloride as radical scavenger.

Irradiation of (Z)‐4 at λ 254 nm leads to decomposition with formation of 2,2‐dimethylpropanenitrile, methanol, isobutane and isobutene.
Electrochemical reduction of benzyl chloride catalyzed by a hetero‐dinuclear complex
Authors: van Veggel Frank C. J. M. , Verboom Willem , Reinhoudt David N. , Bos Martinus
Published: September 2010

The co‐complexed Ba2+ cation in the hetero‐dinuclear complex 1 stabilizes the carbon‐nickel bond that is formed in the reductive coupling of benzyl chloride and 1; the “PhCH2NiII/Ba2+” intermediate reacts with CO2 or acetic anhydride.
1‐Aryl‐2,2‐dimethyl‐1,3‐propanediols as chiral auxiliaries. Acetal formation with α,β‐unsaturated aldehydes and analysis of the stereochemistry of cyclopropanation
Authors: Ebens Rijko , Kellogg Richard M.
Published: September 2010

Optically pure 1‐aryl‐ (phenyl and 2‐chlorophenyl) 1,3‐propanediols, 1a and 1b, condense smoothly with aldehydes to provide the corresponding cyclic acetals 3. Except in cases that the aldehyde is substituted at the α‐carbon atom, a single product is obtained. With the aid of 2D‐NMR the stereochemistry was established to be that with the aldehyde substituent as well as the aryl group equatorial in the favored chair form.

The condensation products with some α,β‐unsaturated aldehydes were subjected to cyclopropanation with diiodomethane/diethylzinc. Reactions proceeded in good yields. Deprotection was achieved by ozonolysis. The cyclopropanecarboxylic acids 6 were obtained in 34‐67% yields and in enantiomeric excesses ranging from 21‐78%.

A stereochemical rationalization of the results is given.
Nucleophilic substitution in diphenylmethyl derivatives. I. Formolysis of diarylmethyl derivatives: An α‐substituent effect
Authors: Strazzolini Paolo , Giumanini Angelo G. , Verardo Giancarlo
Published: September 2010

The reactions of formic acid with and without addition of sodium formate with diphenylmethanol (4) and chlorodiphenylmethane (3) were compared to those with hydroxydiphenylacetic (benzilic) acid (12a) and chlorodiphenylacetic acid (14a). Formic acid did not favour any SNl‐type reaction on 4, but a strong catalysis by iodide ion was observed. Sodium formate rapidly performed the substitution of the chlorine in 3. A similar outcome was obtained with chloro acid 14a, but the rationalization of the results is different. Chloro acid 14a and its methyl ester 14b were prompt to react, but the equilibria were shifted to α‐formyloxy products 13 only by the addition of HCOONa. HCOOH was unable to perform any reduction on either 3 and 4 or 12a and 14a, a fact which was taken as evidence for concerted substitution mechanisms on ion pairs or betaine 15. Mechanistic implications are drawn.
Comparison of flexibly and rigidly bridged donor‐acceptor systems; solvent induced switching between folded and extended emissive charge‐transfer states
Authors: Scherer T. , Willemse R. J. , Verhoeven J. W.
Published: September 2010

Aniline and naphthalene chromophores were linked by either a flexible trimethylene chain (in 1) or a semirigidly extended piperidine ring (in 2). While 1 undergoes photoinduced intramolecular electron transfer in all solvents 2 does so only in more polar solvents, indicating that solvent stabilization is required to make this process feasible at the donor‐acceptor distance imposed in 2. In both 1 and 2 charge recombination is accompanied by exciplex‐type emission which, in polar solvents, appears to stem from a conformationally extended conformation devoid of extensive direct overlap between the chromophores.
Improved synthesis and application of lanthanide 1,4,7,10‐tetrakis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane complexes Ln(DOTP)
Authors: Swinkels Dorine W. , Tesser Godefridus I. , van Duynhoven John P. M. , Hilbers Cornelis W.
Published: September 2010

Complexes of lanthanides with 1,4,7,10‐tetrakis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane (DOTP) were synthesized for use as shift reagents in a study on the three‐dimensional structure of the gene‐5 protein encoded by Coli‐phage M13. The detailed synthesis is an improvement of methods scattered throughout the literature on three main aspects, and involves a series of three steps. The first step consists of condensation of diethylenetriamine and diethanolamine, yielding the twelve‐membered ring 1,4,7,10‐tetraazacyclododecane (“cyclen”). Ring closure was performed by reaction of N‐(4‐toluenesulfonyl)diethanolamine bis‐4‐toluenesulfonic ester (the synthesis of which was improved), and the disodium salt of tris(4‐toluenesulfonyl)diethylenetriamine. Following hydrolysis, a simplified work‐up procedure was devised. Subsequently, in the second step, phosphonomethyl groups were introduced in the amino functions by condensation with formaldehyde and phosphorous acid to give DOTP. Since DOTP failed to crystallize spontaneously, the previously described work‐up procedure was modified. In the third step, a lanthanide ion (Ln3 +) was added to a small excess of DOTP at 80 °C and pH 8‐9. The identity of each desired Ln(DOTP) complex was determined by: (1)1H NMR and 31PNMR spectroscopy and (2) lanthanide ion fluorescence experiments. Preliminary 1H NMR studies were performed to determine the activity of the Ln(DOTP) complexes as shift reagents for the gene‐5 protein.