bluuebunny/crossref_metadata_2025 huggingface dataset:
Vinylcyclopropan‐Komplexe und Vinylcyclopropane aus Carben‐Komplexen und 1,3‐Dienen
Authors: Fischer Hemut , Hofmann Josef
Published: July 2007

Vinylcyclopropane Complexes and Vinylcyclopropanes from Benzylidene Complexes and 1,3‐Dienes

Benzylidenepentacarbonyl complexes (CO)5M[C(C6H4R‐p)H] (1) [M – W:RH (a), OMe (b); MCr: R – H (c), OMe (d)], react with cyclopentadiene by stereospecific transfer of the benzylidene ligand to one CC bond of the diene and coordination of the resulting endo;‐6‐arylbicyclo[3.1.0]hex‐2‐ene (4) to the metal. The [CO]5M fragment occupies the exo‐position. Addition of bromide liberates 4 from the metal. The reaction of 1a with 1,3‐cyclohexadiene gives the corresponding (endo;‐7‐phenylbicyclo[4.1.0]hept‐2‐ene)tungsten complex (6) and, after addition of Br−, the free bicyclic compound. The sequential reaction of 1a with 1,2,3,4,5‐pentamethylcyclopentadiene and Br− affords the endo;‐6‐phenyl‐exo;‐4‐methyl isomer of pentamethylphenylbicyclo[3.1.0]hex‐2‐ene 9 with more than 85% stereoselectivity. The benzylidene transfer from 1a to cis‐and trans‐pentadiene, isoprene, and 2‐chloro‐1,3‐butadiene proceeds regiospecifically to the more electron‐rich CC bond to give (E)‐ and (Z)‐phenylvinylcyclopropanes. The E/Z ratio ranges from 0.52 to 2.2. The structures of the complexes 3d and 6 were established by X‐ray analyses.
Organosubstituierte 2,5‐Dihydro‐1,2,5‐oxoniasilaboratole Charakterisierung und Reaktivität
Authors: Köster Roland , Seidel Günter , Wrackmeyer Bernd
Published: July 2007

Organosubstituted 2,5‐Dihydro‐1,2,5‐oxoniasilaboratoles – Characterization and Reactivity.

The potassium salts of the anions (2a−d, a: R2,3 = CH3; b: R2 = C2H5, R3 = CH3; c: R2 = C6H5, R3 = CH3; d: R3 = C6H5), prepared from the organosubstituted cis;‐2‐boryl‐1‐silylalkenes 1a – d and KOH, react with the electrophiles R1Hal [R1 = H: HCl, (CH3)3NHCl; R1 = CH3: (CH3)I, (CH3)4NCl; or (CH3)3ElIV(CH3)3, ElIV=Si, Ge, Sn, Pb] to give the neutral five‐membered ring compounds [R1 = H: 3H; CH3; 3Me; ElIV(CH3)3: 3ElIV]. On heating of 3H or 3Sn either ethyl migration occurs to yield the saturated diastereomers (4) [4/4′: R3′ = H; 4Sn/4′Sn: R3′ = Sn(CH3)3], or elimination of ethane takes place to give the unsaturated compounds (5). The reaction of 2 with ClPb(CH3)3 leads to 3Pb [R1=Pb(CH3)3] (11B‐NMR), which exclusively form 5 with elimination of C2H5Pb(CH3)3.
Tetrahydrofuran‐Soluble Magnesium Dihydride by Catalytic Hydrogenation of Magnesium*)
Authors: Bogdanovic Borislav , Bons Peter , Schwickardi Manfred , Seevogel Klaus
Published: July 2007

Upon hydrogenation of magnesium in THF using homogeneous magnesium‐anthracene transition‐metal halide catalysts in the presence of small amounts of MgCl2 and solubilizing agents L, a dissolved form of magnesium hydride (MgH'2) is produced. The preferred L's are quinuclidine (QC) or organomagnesium compounds; however, organoaluminium and ‐boron compounds can also be used. The fraction n of magnesium hydride produced in the dissolved form and the stability of the MgH'2 solutions are investigated as a function of the kind and the amount of solubilizing agents and catalysts. The optimized method for the preparation of MgH'2 is described. The magnesium hydride dissolved in THF is characterized by IR spectroscopy. In order to elucidate the role of the solubilizing agents, THF‐soluble MgCl2‐containing stoichiometric MgH2 · QC model complexes are also prepared and characterized by IR spectra. Advantages and disadvantages of using MgH'2 for synthetic purposes instead of catalytically prepared suspensions of magnesium hydride (MgH2) are discussed.
Kohlenwasserstoffverbrückte Metallkomplexe, XVIII. Heterometallische Ethylen‐verbrückte Komplexe (OC)5ReCH2CH2Mn(CO)5, (OC)5ReCH2CH2Ru(CO)2Cp, (OC)5ReCH2CH2Os(CO)4CH2CH2Re(CO)5und (OC)5ReCH2CH2CH2Os(CO)4Os(CO)4(CO)4Os(CO)4CH2CH2Re(CO)5
Authors: Breimair Josef , Niemer Burkhart , Raab Klaus , Beck Wolfgang
Published: July 2007

Hydrocarbon‐Bridged Metal complexes, XVIII. – Heterometallic Ethylene‐Bridged Complexes (OC)5ReCH2CH2Mn(CO)5, (OC)5ReCH2CH2Ru(CO)2Cp, (OC)5ReCH2CH2Os(CO)4CH2CH2Re(CO)5and (OC)5ReCH2CH2CH2Os(CO)4Os(CO)4(CO)4Os(CO)4CH2CH2Re(CO)5

Addition of [(OC)5Re(C2H4)]+to the carbonylmetallates [Mn(CO)5]−, [RuCp(CO)2]−, [Os(CO)4]2−, [Os3(CO)12]2−affords the title complexes in a directed way. The dynamic behaviour of (OC)5ReCH2CH2Mn(CO)5in solution is attributed to a dyotropic exchange of the pentacarbonylmetal groups on the CH2CH2bridge.
Intramolecular, Metallacyclic Organoaluminium, ‐gallium and ‐indium Addition Compounds Crystal Structure of 1‐Galla‐5‐azabicyclo[3.3.3]undecane
Authors: Schuman Herbert , Hartman Uwe , Wassermann Wilfried , Just Oliver , Dietrich Andreas , Pohl Ludwig , Hostalek Martin , Lokai Matthias
Published: July 2007

Intramolecularly base‐stabilized four‐coordinated metallacyclic organoaluminium, ‐gallium, and ‐indium compounds C5H10‐Al(CH2)3NMe2 (4), C4H8Ga(CH2)3NMe2 (5), C5H10Ga(CH2)3N‐Me2 (6), C5H10GaCH2CH(Me)CH2NMe2 (7), C4H8Ga(CH2)4NMe2 (8), C5H10Ga(CH2)4NMe2 (9), EtAl[(CH2)3]2NMe (10), MeGa‐[(CH2)3]2NMe (11), EtGa[(CH2)3]2NMe (12), MeIn[(CH2)3]2NMe (13), and (14) have been synthesized by the reaction of [3‐(dimethylamino)propyl]aluminium dichloride (1), [3‐(dimethylamino)propyl]gallium dichloride (2), [3‐(dimethylamino)‐2‐methylpropyl]gallium dichloride (3), or [4‐(dimethylamino)butyl)gallium dichloride with the respective bis‐Grignard reagents or by the reaction of the organometal dichlorides RMCl2 with bis[3‐(chloromagnesio)propyl]methylamine or with N,N′‐bis[3‐(chloromagnesio)propyl]‐N,N′‐dimethyl ethylenediamine. Aluminium or gallium trichloride reacts with tris[3‐(chloromagnesio)propyl]amine to give Al[(CH2)3]3N (15) and Ga[(CH2)3]3N (16). The 1H‐, 13C‐NMR and mass spectra of the new compounds as well as the X‐ray crystal structure of 16 are discussed. 4, 6, and 12 have been tested successfully as MOVPE precursors.
Heterogeneous Photocatalysis, IX. Zinc Sulfide Catalyzed Photoreduction of Carbon Dioxide
Authors: Kisch Horst , Twardzik Gerhard
Published: July 2007

Carbon dioxide is catalytically reduced to formate in a suspension of zinc sulfide in water/2,5‐dihydrofuran when irradiated (λ ≥ 290 nm). Turnover rates are in the range of 1.5 monolayers CO2/h. No reaction occurs at pH=12, and a very slow one at pH=3.2,5‐Dihydrofuran functions as reducing agent which is oxidized to dehydro dimers. When it is substituted by 2‐propanol, no CO2 reduction is observed. Semiconductor photocatalysis by a two‐electron transfer from zinc sulfide to adsorbed hydrogen carbonate is assumed as the key step of CO2 fixation.
Synthesis of Optically Active Bis(2‐oxazolines): Crystal Structure of a 1,2‐Bis(2‐oxazolinyl)benzene ZnCl2 Complex
Authors: Bolm Carsten , Weickhardt Konrad , Zehnder Margareta , Ranff Tobias
Published: July 2007

Dinitriles (5–7, 12, 13) react with enantiomerically pure β‐amino alcohols (8 – 11,17) under zinc chloride catalysis to give optically active C2‐symmetric bis(oxazolines). 1,2‐Bis(2‐oxazolin‐2‐yl)benzenes 1a – e are obtained under mild reaction conditions. 1H‐NMR spectroscopy indicates the formation of 1:1 complexes 23 of these compounds with ZnCl2. The energy required for a conformational interconversion of zinc dichloride complex 23e was determined by variable‐temperature 1H‐NMR studies. An X‐ray structure analysis was performed with the substituted [1,2‐bis(2‐oxazolinyl)benzene]zinc dichloride complex 23a.
Azobrücken aus Azinen, XII. Transannulare Hydroborierung von parallel benachbarten CC/NN‐Bindungen
Authors: Brand Uwe , Hünig Siegfried , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Azo Bridges from Azines, XII., – Transannular Hydroboration of Close Parallel CC and NN Bonds

In the systems 3 and 5 9‐borabicyclo[3.3.1]nonane (9‐BBN) adds to the close parallel CC/NN bonds in a transannular reaction. A B – N bond is formed and the borane hydrogen transferred to the CC bond regio‐ and stereospecifically. The structure of the adducts 4 and 6 is elucidated by NMR spectroscopy and in the case of 4a by an X‐ray analysis. The catecholborane 9 forms with 3 an azo – borane adduct at first, pointing to a stepwise transannular reaction.
Ring – Chain Tautomerism of 4‐Hydroximino‐hexahydropyrimidines Substituted in Position 2
Authors: Korbonits Dezsö , Tóbiás‐Héja Erzsébet , Kolonits Pαl
Published: July 2007

As shown by NMR spectroscopy, the reaction of 3‐aminopropionamide oxime (9) with benzaldehyde or benzaldehyde derivatives 2a–d substituted with electron‐attracting substituents affords products which exist as an equilibrium mixture of tautomers involving the open‐chain 3‐(benzylideneamino)‐propionamide oximes 11a – d and the cyclic 4‐hydroximinohexahydropyrimidines 12a – d. Tautomers 11 and 12, isolated also in crystalline form, can be interconverted by using an appropiate solvent. In contrast, in the reaction of benzaldehydes substituted with electron‐releasing groups (2e, f) and cinnamaldehyde (2g) with 9 only the open‐chain imines are formed, and in aprotic solvents no tautomerism can be observed.
Organische Synthesen mit übergangsmetall‐Komplexen, 51. 1‐Metalla‐1,3,5‐triene und 1‐Metalla‐1,3‐dien‐5‐ine von Chrom und Wolfram durch Insertion von Alkinen in MC‐ bzw. CC‐Bindungen von 1‐Metalla‐1,3‐dienen bzw. 1‐Metalla‐1‐en‐2‐inen
Authors: Aumann Rudolf , Heinen Heinrich , Hinterding Peter , Str äter Norbert , Krebs Bernt
Published: July 2007

Organic Syntheses via Transition Metal Complexes, 51. – 1‐Metalla‐1,3,5‐trienes and 1‐Metalla‐1,3‐dien‐5‐ynes of Chromium and Tungsten by Insertion of Alkynes into MC and CC Bonds of 1‐Metalla‐1,3‐dienes and 1‐Metalla‐1‐en‐3‐ynes, respectively

1‐Metalla‐1,3,5‐trienes LnMC(NEt2)–C(Me)C(OEt)–CHCHPh (3,4) and LnMC(OEt)– CHC(NEt2) – C(Me)=CHPh [5, LnMCr(CO)5 (a), W(CO)5 (b)] are obtained for the first time from the corresponding 1‐metalla‐1,3‐dienes LnMC(OEt) – CHCHPh (1a, b) under very mild conditions by the insertion of the electron‐rich alkyne Et2N–C  C – Me (2) into the MC and the CC bonds, respectively, of 1. The chelate complex (6b) and the cyclobutenyl carbene complex 7b are isolated as minor side products. 1‐Metalla‐1,3‐dien‐5‐ynes LnMC(NEt2) – C(Me)=C(OEt) – C  CPh [9, 10, LnMCr(CO)5 (a), W(CO)5 (b)] are formed with high regio‐ and stereoselectivity on insertion of 2 into the MC bonds of 1‐metalla‐1‐en‐3‐ynes 8. X‐ray data are given for the tungsten complex 3b.
Alkine und Cumulene, XXIII. über einige Neben‐ und Folgeprodukte der Dichlorketen‐Herstellung aus α,α‐Dichloracetylchlorid
Authors: Hopf Henning , Stamm Reiner , Jones Peter G.
Published: July 2007

Alkynes and Cumulenes, XXIII. – On Some Byproducts of the Dichloroketene Preparation from α,α‐Dichloroacetyl Chloride

When α,α‐dichloroacetyl chloride (1) is dehydrochlorinated with triethylamine in refluxing ether, two oligomers are obtained: 1‐dichloroacetoxy‐1‐dichloromethyl‐2,2‐dichloroethylene (3) and octachloro‐1,2‐bis(methylene)cyclobutane (4). The mechanisms of formation of these tri‐ and tetrameric products of 1 and dichloroketene (2), respectively, are discussed, and an X‐ray structural analysis of 4 is reported.
Synthese und Kristallstruktur von Li2[(Me3SiCH2)3AlCH2Al(CH2SiMe3)3] — ein Addukt des Dilithiomethans CH2Li2?
Authors: Uhl Werner , Layh Marcus , Massa Werner
Published: July 2007

Synthesis and Crystal Structure of Li2[(Me3SiCH2)3AlCH2Al(CH2SiMe3)3]—a Dilithiomethane Derivative?

Reaction of (trimethylsilyl)methyllithium with the methylene‐bridged aluminium tetrachloride Cl2AlCH2AlCl2 yields dilithium methylenebis[tris(trimethylsilylmethyl)aluminate] (2) as the only isolable product. All attempts for preparing the tetraalkyl analogue have been unsuccessful. The crystal structure of 2 exhibits a hexacoordinated central carbon atom with short LiC distances. Both lithium atoms and the methylene hydrogens of the AlCH2 Al unit are almost coplanar. The discussion of the structure and properties leads to the attractive description of 2 as an adduct of tris(trimethylsilylmethyl)‐aluminium to dilithiomethane CH2Li2.
Syntheses and Molecular Structures of an Isoelectronic Series of (2‐Hetero‐)1,3‐Diphosphabenzenes
Authors: Schmidbaur Hubert , Gamper Siegfried , Paschalidis Christos , Steigelmann Oliver , Müller Gerhard
Published: July 2007

Syntheses, NMR spectra, and X‐ray molecular structures of three (2‐hetero‐)1,3‐diphosphabenzenes are reported which constitute an isoelectronic triade of compounds with BH2, CH, and N bridging units between the two phosphorus atoms. The remaining three carbon atoms of the rings are part of a 2‐methallylic system. The 2‐borataheterocycle 3 has been prepared by the reaction of CH2 = C(CH2)PPh2)2 (1) with Me2SBH2Br to give an intermediate 2 still containing the exocyclic olefinic bond. Treatment of 2 with a base, deprotonation of one ring CH2 group, and proton migration from the other one to the olefinic CH2 group afford the 5‐methyl‐1λ5‐phospha‐3‐phosphonia‐2‐boratabenzene 3. The PBP unit is tilted by 144.0(2)° against the planar C3P2 part of the ring. A heterocyclic precursor 4 for the carbon analog is generated from 1 and CH2I2, which on reaction with a strong base yields the diphosphabenzene 5 with a fully planar ring skeleton. For the synthesis of the aza analog 7, CH2=C(CH2Cl)2 is treated with HN(PPh2)2 to give the precursor 6, which can be deprotonatad at nitrogen and carbon with a base. In the crystals of 7, two independent molecules of very similar structure are present. The molecules show planar heterocycles.
Fusing Cyclopentadiene and Ferrocene by Two Silyl Bridges Stereochemically Well‐Defined Building Blocks for High‐Nuclear Metallocenes
Authors: Fritz Monika , Hiermeier Johann , Hertkorn Norbert , Köhler Frank H. , Müller Gerhard , Reber Gabriele , Steigelmann Oliver
Published: July 2007

The tetrahydro‐4,4,8,8‐tetramethyl‐4,8‐disila‐s‐indacenyl anion (LH) reacts with or without cyclopentadienyl anion (Cp−) and Fe2Cl4(THF)3 to give the mixed ferrocenes CpFe(LH) and (LH)2Fe in 50 and 63% yield, respectively. Near room temperature and in solution CpFe(LH) exists as a pair of enantiomers (syn‐3a/b). According to an X‐ray analysis both enantiomers are present in a single crystal. Compound 3 consists of a ferrocene linked to a cyclopentadiene by two Me2Si groups such that the acidic Cp proton points towards the iron. Temperature‐dependent NMR spectra show that syn‐3a and syn‐3b are non‐rigid molecules which are interconverted by 1,2‐silatropic bond shifts (Ea = 49.2 ± 2.9 kJmol‐1). Three more isomers (anti‐3a, anti‐3b, and the spiro derivative 3c), though present only in low concentration, are engaged in the rearrangement. (LH)2Fe is also non‐rigid and exists as a pair of diastereomers (4a and 4b). The isomers of 3 and 4 undergo hydrolysis (e.g., syn‐3a/3b gives [(Me2SiOSiMe2)Cp]FeCp (5) among others) and deprotonation. The latter yields CpFe(L–) (7) and (L−)2Fe (8), which are characterized by NMR spectroscopy. 7 forms crystals with [Li(TMEDA)]+ as counterion, and an X‐ray analysis shows that lithium and iron are located at opposite sides of the strongly folded ligand L. The reaction of 7 with CrCl2(THF) gives the trinuclear stacked metallocene 9 in 47% yield. 9 has two unpaired electrons which are located essentially in the center of the molecule.
Umwandlung der Cluster Fe3(CO)9(μ3‐η2‐N2Et2) und Fe3(CO)9(μ3‐NEt)2 zu organischen Produkten 1)
Authors: Tasi Miklos , Powell Anne K. , Vahrenkamp Heinrich
Published: July 2007

Conversion of the Clusters Fe3(CO)9(μ3‐η2‐N2Et2 and Fe3(CO)9(μ3‐NEt)2 into Organic Products

The azoalkane‐bridged cluster Fe3(CO)9(μ3‐η2‐N2Et2) (1) and its thermal rearrangement product Fe3(CO)9(μ3‐NEt)2 (2) are converted by standard routes into derivatives with one carbene ligand C(Ph)OEt (3, 4). Degradation (thermally or oxidatively) of these compounds produces the diaziridine magnified image (5) and/or the iminoester EtN = C(Ph)OEt (6). 4 and moist p‐tolyl isocyanide form the indole derivative 8. 1 adds one or two equiv. of alkynes leading to the alkyne‐bridged cluster 9 or the ferrole‐type clusters 10. The clusters 10, resulting from HCCPh, exist as two isomers 10a and b which can be equilibrated and separated. An alternative route to 10 c (alkyne: MeCCMe) starts from Fe2(CO)6(C4Me4) by treating it with Fe2(CO)9 and N2Et2. Photolytic or oxidative degradation of the clusters 10 produces substituted furan 13, pyrrole 14, or dihydropyridazine 15. The crystal structures of the clusters 4, 9, 10a, and 10b have been determined.
Synthesis and Characterization of Organogallium and Organoindium Compounds with Tridentate 2,6‐Bis[(dialkylamino)methyl]phenyl Ligands
Authors: Schumann Herbert , Hartmann Uwe , Wassermann Wilfried
Published: July 2007

The intramolecularly stabilized five‐coordinated organogallium and organoindium compounds {2,6‐[(CH3)2NCH2]2C6H3H3}‐GaMe2 (1), {2,6‐[(CH3)2NCH2]2C6H3}InR2 (2–4), and {2,6‐[(C2H5)2‐NCH2]2C6H3}InEt2 (5) have been synthesized from {2,6‐bis‐[(dimethylamino)methyl]phenyl)}lithium or from {2,6‐bis[(diethylamino)methyl]phenyl}lithium and the corresponding diorganogallium or diorganoindium chloride. The 1H‐, 13C‐NMR and mass spectra of the new compounds are reported and discussed.
Complexes with sterically demanding ligands, XVI. An unexpected coupling of trimethylsilyl‐substituted cyclopentadienide anion by ferric chloride
Authors: Okuda Jun , Herdtweck Eberhardt , Zeller Edgar M.
Published: July 2007

Reaction of 1,2,4‐tris(trimethylsilyl)cyclopentadienyllithium with ferric chloride in THF at ‐95°C leads to the formation of a thermally sensitive iron(III) complex which decomposes to the new dihydrofulvalene derivative 3,7‐dihydro‐1,3,3,5,7,7‐hexakis(trimethylsilyl)fulvalene (1).
Methine‐Brigded Five‐Membered Heterocycles as Precursors for Low‐Gap Polymers
Authors: Hieber Gunter , Hanack Michael , Wurst Klaus , Strähle Joachim
Published: July 2007

The synthesis of suitable precursors of polyarenemethines (PAM) 1, which are predicted to be potential low gap polymers, is described. The Knoevenagel condensation of heteroaromatic aldehydes with 2,5‐dihydrothiophene 1,1‐dioxide (5), 2,5‐dihydrothiophene 1‐oxide (9), and its benzo‐annulated analogs [6 and [10] yields the methine‐bridged compounds 7, [8], 11, and [12], respectively. Reduction of the methine‐bridged sulfoxides 11 and [12] leads to the corresponding sulfides 13 and [14]. For compound 18 with a high sterical demand another route has been developed. Thus, the reaction of the dicarbinol 17 with HI yields directly the heteroaromatic quinodimethane 18. The molecular structures of 7a and 18 are determined by X‐ray analysis.
Retention of Configuration and E/Z Stereoselectivity in the Photolysis of cis‐ and trans‐Tetraalkyl‐4‐methylene‐1‐pyrazolines
Authors: Quast Helmut , Jakobi Harald
Published: July 2007

The isomeric 4‐methylene‐1‐pyrazolines cis‐ and trans‐2 are synthesized by a Wittig reaction from the pyrazolin‐4‐ones cis‐ and trans‐1, respectively. Direct irradiation with 350‐nm light of cis‐2 affords the alkylidenecyclopropanes cis‐8, (E)‐ and (Z)‐9 (64: 17: 19) besides molecular nitrogen and small amounts of the 4‐methylenepyrazolidine cis‐7 as a result of photoreduction. Under the same conditions, trans‐2 is converted into trans‐8 as well as (E)‐ and (Z)‐9 (64: 14: 22). The configurations of cis‐ and trans‐8 have been established by means of a 1,3‐dipolar cycloaddition with mesityl nitrile oxide which furnishes two cycloadducts from cis‐8, e.g. cis‐14A and B, but only one cycloadduct from trans‐8, viz. trans‐14. The configurations of (E)‐ and (Z)‐9 have been assigned on the basis of homoallylic 1H,1H coupling constants and nuclear Overhauser experiments. The results demonstrate that, on the least‐motion paths leading to cis‐ and trans‐8, the configuration of the ring substituents in cis‐ and trans‐2 is completely retained. Of the non‐least‐motion products (E)‐ and (Z)‐9 the latter is favoured regardless of the configuration of the precursors cis‐ and trans‐2 though the extent of (Z) selectivity depends on that configuration. The results are interpreted in terms of bis‐orthogonal trimethylenemethane diradicals as primary intermediates from which irreversible paths bifurcate. Cyclization yields cis‐8 (from cis‐2) or trans‐8 (from trans‐2) and 90°‐bond rotations afford two diastereomeric mono‐orthogonal trimethylenemethane diradicals [(E)‐ and (Z)‐18] which eventually cyclize to the corresponding non‐least‐motion products (E)‐9 and (Z)‐9.
Reaktionen von Komplexliganden, XLIII. Optisch aktive Aminocarben‐Komplexe: Reagentien für die regiospezifische und diastereoselektive Synthese von γ‐Lactamen
Authors: Dötz Karl Heinz , Weber Rita
Published: July 2007

Reactions of Complex Ligands, XLIII. ‐ Optically Active Aminocarbene Complexes: Reagents for the Regiospecific and Diastereoselective Synthesis of γ‐Lactams

Optically active pentacarbonyl[amino(aryl)carbene] complexes 2 ‐ 5 of chromium have been obtained by aminolysis of methoxycarbene complexes 1 with L‐amino acid esters. The alanyl and phenylalanyl compounds 2, 3 react with 1‐octyne regiospecifically and moderately diastereoselectively to give the pyrrolinones 6, 7.
Darstellung O‐geschützter (R)‐2‐Hydroxyaldehyde und ihre Hydrocyanierung
Authors: Effenberger Franz , Hopf Martin , Ziegler Thomas , Hudelmayer Jochen
Published: July 2007

Synthesis of O‐Protected (R)‐2‐Hydroxy Aldehydes and Their Hydrocyanation

The synthesis of O‐silyl‐ and O‐benzyl‐protected (R)‐2‐hydroxy aldehydes (R)‐6 from (R)‐2‐hydroxy carboxylic acids (R)‐1 is described. While attempts for their diastereoselective hydrocyanation with hydrocyanic acid and (R)‐oxynitrilase as catalyst have not been successful, the cyano silylation with trimethylsilyl cyanide occurred diastereoselectively with a ratio of 81 : 19 preferring the threo form without racemization at C‐2 of the 2‐hydroxy aldehyde.
Geminal‐Dialkyl‐Effect‐Controlled Site Selectivity of Fe(I)‐Mediated C  H/C  C Bond Activation of Aliphatic Ketones
Authors: Schröder Detlef , Bowie John H. , Stringer M. B. , Schwarz Helmut
Published: July 2007

Depending on the internal energy content, due to the operation of a geminal dialkyl effect, the Fe+ ‐mediated dehydrogenation of α,α‐dimethyl‐substituted ketones preferably involves the more substituted alkyl chain.
Pyrazole—Organoboranes, VIII Thermal C—Borylation in Crowded Pyrazolylboranes
Authors: Yalpani Mohamed , Köster Roland , Boese Roland
Published: July 2007

Crowded 3,5‐disubstituted pyrazoles, e. g. 3,5‐di‐tert‐butyl‐,3,5‐di‐tert‐butyl‐4‐methyl‐, or 3,5‐di‐tert‐butyl‐4‐ethylpyrazole [(tb)2Pz, (tb)2mPz, or (tb)2ePz, respectively], fail to react with activated trialkylboranes (e. g. BEt3* or BPr3*) at 110°C, even after prolonged heating. At 170°C the reaction of (tb)2Pz with activated triethylborane gives the monomeric diethyl(3,5‐di‐tert‐butyl‐1‐pyrazolyl)borane (3). At 220–230°C the dimeric boracycles (4)2 are mainly formed [X‐ray structure of (4a)2]. In contrast, the reactions of these crowded pyrazoles with tetraalkyldiboranes(6) commence just above room temperature. Diethylhydroborane adducts (5) of 3 and dimeric alkyl(3,5‐di‐tert‐butyl‐1‐pyrazolyl)‐boranes (2b)2 and (2c)2 are the main products.
Kurzmitteilung/Short Communication Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, LXXV Synthese eines Diphosphamolybdacyclopentens durch Alkin‐Insertion in die P—P‐Bindung eines Diphosphamolybdacyclopropans
Authors: Lindner Ekkehard , Heckmann Maria
Published: July 2007

Metal‐Containing Heterocycles: Preparation, Properties, Reactions, LXXV1). — Synthesis of a Diphosphamolybdacyclopentene by Alkyne Insertion into the P ‐ P Bond of a Diphosphamolybdacyclopropane

Insertion of the alkyne RCCR (R = CO2Me) into the P ‐ P bond of the diphosphamolybdacyclopropane (5‐C5H5)‐(OC)2Mo‐PPh2‐PAr (2) [Ar = 2,4,6‐(tBu)3C6H2] results in the formation of the thermally and kinetically stable diphosphamolybdacyclopentene (η5‐C5H5)(OC)2Mo‐PPh2‐RC = CR‐PAr (3), which is characterized on the basis of mass, IR, 31P{1H}‐, 1H‐, and 13C{1H}‐NMR spectra.
Stable N‐Phosphanyl Nitrilimines: Reactivity on the Periphery of the Nitrilimine Skeleton
Authors: Castan Florence , Granier Michel , Baceiredo Antoine , Bertrand Guy , Straw Thomas A. , Dillon Keith B.
Published: July 2007

Reactions involving the λ3‐phosphorus atom of N‐[bis(diisopropylamino)phosphanyl)]‐C‐[(bis(diisopropylamino) ‐thio‐phosphoranyl)nitrilimine (1) are reported. Addition of elemental sulfur or selenium to 1 leads, by a formal [1 + 4] cycloaddition, to 1,3,4,2λ5‐thiadiazaphosphole 3a or 1,3,4,2λ5‐selenodiazaphosphole 3b in 85 and 84% yield, respectively. Reactions of 1 with dimethyl acetylenedicarboxylate and tetracyanoethylene afford the corresponding [2 + 4] adducts 1,2,3λ5‐diazaphosphinine 6 (80% yield) and 1,2,4,3λ5‐triazaphosphinine 10 (80% yield). Phenyl azide reacts with 1 with loss of nitrogen to give 1,2,4,3λ5‐triazaphosphole 15 (74% yield), while the reaction of 1 with α‐diazo ketone 17 leads with conservation of the N2 grouping to the formation of 1,2,4,3λ5‐triazaphosphole 20 (85% yield). Addition of methyl trifluoromethanesulfonate to 1 affords N‐[bis(diisopropylamino)methylphosphonioyl]‐C‐[bis(diisopropylamino)thiophosphoranyl]nitrilimine 22. In contrast to 1, the new stable nitrilimine 22 is strongly electrophilic. [2 + 3] cycloadditions are observed with ethyl vinyl ether, styrene, methyl acrylate and phenylacetylene to furnish the corresponding pyrazolines 23 – 25 and pyrazole 26 in good yields. Water adds to 22 by a 1,3‐addition process to give hydrazine 27 (88% yield). The lithium salt 30 of [bis(diisopropyl‐amino)thiophosphoranyl](diazo)methane reacts with [bis(pentafluorophenyl)](chloro)phosphane to afford the corresponding diazo compound 32 (50% yield) while the reaction with (chloro)(phenyl)[2,4,6‐tris(trifluoromethyl)phenyl]phosphane furnishes nitrilimine 33 in 82% yield. Only 1,3‐addition reactions with water or diisopropylamine leading to hydrazine 34 (65% yield) and hydrazone 35 (54% yield) are observed on treatment with this new poorly reactive nitrilimine.
Photolysis of Tetraalkyl‐1‐pyrazoline‐4‐thiones. – Diastereoselective Formation of (E)/(Z)‐Alkylidenethiiranes from cis‐ and trans‐Tetraalkyl‐1‐pyrazoline‐4‐thiones
Authors: Quast Helmut , Fuß Andreas , Jakobi Harald
Published: July 2007

The tetraalkyl‐1‐pyrazolin‐4‐ones 5 react with hydrazine to afford the hydrazones 6 which are transformed into the thiones 7 in high yields by treatment with disulphur dichloride in the presence of triethylamine. Selective excitation of the azo chromophor of 7a with 350‐nm light gives rise to the isopropylidenethiirane 8, besides molecular nitrogen, in a very clean reaction; at almost quantitative conversions, less than 2% of byproducts are observed, and about 10% of 8 have isomerized to the pentadienethiol 9. Photolysis of the stereoisomers cis‐ and trans‐7b yields mixtures of the alkylidenethiiranes (E)‐and (Z)‐10 with (E)/(Z) ratios of 35:65 and 49:51. The results are interpreted in terms of diastereomeric bis‐orthogonal (cis‐ and trans‐21) and mono‐orthogonal thioxyallyl diradicals (E)‐ and (Z)‐23 which cyclize to furnish (E)‐ and (Z)‐10. There seems to be a qualitative resemblance between the photochemical and thermal stabilities in the series of 4‐substituted tetramethyl‐1‐pyrazolines, viz. 7a < 12 < 5a, 13, similar to that suggested by Engel for 2,3‐diazabicyclo[2.2.2]oct‐2‐ene derivatives.
3‐Aza‐ und syn‐3,7‐Diazaoctabisvalen Synthesen, Röntgenstrukturanalysen, neue Heterocyclen
Authors: Trupp Björn , Fritz Hans , Prinzbach Horst , Irngartinger Hermann , Reifenstahl Uwe
Published: July 2007

3‐Aza‐ and syn‐3,7‐Diazaoctabisvalene. ‐ Syntheses, X‐ray Structural Analyses, Novel Heterocycles

Preparatively useful routes for 3‐aza‐ and syn‐3,7‐diazaoctabisvalenes have been designed based on well available materials. Thus, 7‐cyano‐3‐azaoctabisvalene (4) becomes available in a six‐ (five‐) step synthesis from the valence tautomers 7‐cyanotropilidene ⇄ 7‐cyanonorcaradiene (7 ⇄ 8) (derived dioxides 9/10) in an overall yield of ca. 30%, syn‐3,7‐diazaoctabisvalene (5) in a three‐step synthesis from muco‐diazidotetrol 30a in ca. 25% overall yield. For 4 and 5 spectroscopic (e.g. 15N‐NMR resonances, 13C,13C coupling constants) and structural details (X‐ray analyses) are determined. 4 and 5 serve as starting materials for the construction of several novel heteropolycyclic skeletons (e.g. 46, 48, 50, 51, 52, 54).
N‐[α‐(o‐ and p‐Methoxyaryl)alkyl]benzotriazoles: Preparation and Use in Synthesis
Authors: Katritzky Alan R. , Lan Xiangfu , Lam Jamshed N.
Published: July 2007

Methoxybenzenes and ‐naphthalenes are benzotriazolylmethylated in the para‐position or if this is blocked in an ortho‐ position. The methylene groups in the products are readily substituted by electrophiles via the lithiated derivatives. Displacement of the benzotriazole group can be effected by organometallic reagents or by electron‐rich benzoid compounds to afford a versatile method for the synthesis of substituted aryl ethers.
Improved Synthesis of Fluoromethanesulfonyl Chloride
Authors: Lange Ulla , Senning Alexander
Published: July 2007

Introduction of fluorine into 4‐chlorobenzyl chloromethyl sulfide (7) by crown‐ether‐assisted nucleophilic substitution furnishes 4‐chlorobenzyl fluoromethyl sulfide (5), a key intermediate for the preparation of fluoromethanesulfonyl chloride (1).
Synthese und Strukturen von metallhaltigen achtgliedrigen N — S — O‐Heterocyclen
Authors: Dembowski Udo , Noltemeyer Mathias , Gilje John W. , Roesky Herbert W.
Published: July 2007

Synthesis and Structures of Metal‐Containing Eight‐Membered N — S — O Heterocycles

Racemic N‐alkylsulfinamides 1a, b react with aluminium, gallium, and indium alkyls 2a — d to form puckered eight‐membered NSO‐complexes [Me2AlN(CF3)2C6H3S(tBu)O]2 (3a), [Me2AlN‐(Ph)S(tBu)O]2 (3b), [Me2GaN(CF3)2C6H3S(tBu)O]2 (3c), [(Me3‐ SiCH2)2GaN(CF3)2C6H3S(tBu)O]2 (3d), [(Me3SiCH2)2InN(Ph)S‐ (tBu)O]2 (3e), and [(Me3SiCH2)2InN(CF3)2C6H3S(tBu)O]2 (3f). Compounds 3a, c, d crystallize in the triclinic space group P¯1. A comparision of the X‐ray structures of 3a, c, d reveals that the sulfur atoms in one molecule of 3d have either (R,R) or (S,S) configuration (Z = 2). In the case of less bulky ligands at the metal atoms (3a, c) both configurations at the sulfur atoms (R,S) are present in one molecule (Z = 1).
Eine einfache Synthese von 1,3‐Diphospha‐2,4‐disilabicyclo[1.1.0]butanen und Isomerisierung durch Silicium‐Inversion
Authors: DrieB Matthias , Pritzkow Hans , Reisgys Michael
Published: July 2007

A Facile Synthesis of 1,3‐Diphospha‐2,4‐disilabicyclo[1.1.0]butanes and Isomerization by Silicon Inversion

Dilithiation of the PH positions of the P2Si2 cyclobutanes 2a—h with n‐BuLi and treatment with tBuHgCl leads to the 1,3‐bis(tert‐butylmercurio) compounds 3a—h. According to NMR spectroscopy and X‐ray structural analysis the tert‐butylmercurio groups at phosphours occupy trans configuration. Photolysis of solutions of 3a—d and 3f, g in toluene yields the corresponding 1,3‐diphospha‐2,4‐disilabicyclo[1.1.0]butanes 1a—d and 1f, g. Interestingly, the dimercury compound 3e (R = mesityl and tert‐butoxy) is quite stable in visible light, probably due to intramolecular donor (tBuO) acceptor (Hg) stabilization. Starting from 3b, the light‐induced elimination of the tBuHg groups gives the expected exo,endo‐P2Si2‐bicyclo[1.1.0]butane 1b only as intermediate. The final product of the latter photolysis is the CMe3/CMe3‐exo,exo isomer 1b′. The formation of 1b′ from 1b is an irreversible silicon inversion process caused by unfavourable interaction of the endo substituents in 1b. In comparison, the exo,endo isomer of 1g (R = isityl and CMe3 at silicon) does not rearrange to the Me3C/Me3C‐exo,exo derivative 1g′ under similar photolysis conditions or when heated at 140°C for several days. The route to 1,3‐diphospha‐2,4‐disilabicyclo[1.1.0]butanes 1 described herein allows the synthesis of new derivatives which cannot be prepared from disilenes and white phosphorus.
Zur Kenntnis neuer 1,3,2,4‐Diphosphadisiletan‐ und Diorganodi(phosphino)silan‐Derivate
Authors: DrieB Matthias , Pritzkow Hans , Reisgys Michael
Published: July 2007

Reaction of the bulkily substituted dichlorodiorganosilanes R1R2SiCl2 (R1 = Mesityl, R2 = Mesityl, tBu, OtBu, Xylyl, iBu) with LiPH2. dme in a 1 : 2 molar ratio in THF at ‐30°C leads to the new organo‐substituted 1,3,2,4‐diphosphadisiletanes 1a—e. Compounds 1c—e are isolated as mixtures of diastereomers. The crowded dichlorosilane Is(tBu)SiCl2 (Is = 2,4,6‐ triisopropylphenyl) reacts with LiPH2. dme above 10°C to yield the disubstituted products Is(tBu)Si(PH2)2 (2f) in 87% yield and only minor amounts of the corresponding four‐membered ring [Is(tBu)SiPH]2 (1f), detected by 31P‐ and 29Si‐NMR spectroscopy. Treatment of 2f with 2 equivalents of nBuLi in Et2O gives Is(tBu)Si(PHLi)2 (3f), which with Is(tBu)SiCl2 forms 1f. The reaction of difluorodiisitylsilane with LiPH2.dme in THF leads to different products, depending on the reaction temperature. At — 30°C Is2Si(PHLi)F (7g) is obtained as sole product, whereas at 28°C the air‐stable diphosphino‐substituted Is2Si(PH2)2 (2g) is formed. Elimination of LiF from 7g affords the tetraisityl‐substituted P2Si2‐cyclobutane 1g, and treatment with H2O and Me3SiCl leads to Is2Si(PH2)F (8g) and Is2Si(PHSiMe3)F (9g). The temperature‐dependent 1H‐NMR spectra of 1a — g exhibit two dynamic processes: hindered rotation of the aryl groups at silicon and inversion at phosphorus. — The solid state structures of 1a, 1b, 1g, and 2g are established by X‐ray crystallography. Reaction of 1a with 2 equivalents of M(CO)5.thf (M = Cr, W) yields the P,P′‐bis(pentacarbonylmetal) complexes 10a (M = Cr) and 11a (M = W). A single‐crystal X‐ray diffraction analysis of 10a is performed.

Concerning New 1,3,2,4‐Diphosphadisiletanes and Diorganodi(phosphino)silane Derivatives
Kohlenstoffkettenlänge als Kontrolle bei der Stabilisierung von Propargylradikalen in Mangan(III)‐initiierten Reaktionen von 1‐Alken‐3‐inen. Ein einfacher Zugang zu langkettigen 4‐Acetoxy‐5‐alkinsäuren
Authors: Melikyan Gagik G. , Mkrtchyan Varsik M. , Badanyan Shaliko O. , Vostrowsky Otto , Bestmann Hans Jürgen
Published: July 2007

Control of the Propargylic Radical Stabilization by Carbon‐Chain Length in Manganese(III)‐Mediated Reactions of 1‐Alken‐3‐ynes. – A Facile Synthetic Way to Long‐Chain 4‐Acetoxy‐5‐alkynoic Acids

By investigation of reactions of 1‐alken‐3‐ynes RC  C – CH = CH2 4 with acetic acid/acetic anhydride, mediated by manganese(III) acetate, it has been found that the stabilization of propargylic radical adducts depends on the carbon‐chain length of R in 4. R = C8H17 is shown to be the “critical” chain length when ligand transfer reaction appears to be the only way of stabilization of intermediates, thus providing a facile one‐step access to long‐chain 4‐acetoxy‐5‐alkynoic acids. The dependence of the product ratios on the AcOH/Ac2O ratio has also been demonstrated.
Stereochemie der Ringöffnung von Aziridinonen (α‐Lactamen)
Authors: Quast Helmut , Leybach Holger
Published: July 2007

Stereochemistry of Ring Opening of Aziridinones (α‐Lactams)

The chiral, non‐racemic aziridinone (R)‐4 (e.e. 92%) reacts with magnesium halides to afford the α‐halo amides (S)‐3a (e.e. 88.8%), (S)‐3b (e.e. 89.0%), and (S)‐3c (e.e. 88.2%) in high yields. Acid‐catalysed hydrolysis of (R)‐4 in aqueous acetone yields 74% of the α‐hydroxy amide (S)‐3d (e.e. 88.0%). Methanolysis of (R)‐4 in [D4]methanol at 60°C followed the first‐order rate law with k = 1.53 ṁ 10–5 s–1 yielding quantitatively a 82:18 mixture of the α‐methoxy amide (S)‐3e (e.e. 89%) and the α‐amino ester (R)‐14 (e.e. 87%). The latter is obtained exclusively (e.e. 87%) when (R)‐4 reacts with sodium methoxide and methanol in ether while only the former is formed (e.e. 88.2%) by slow methanolysis in the presence of a catalytic amount of 4‐toluenesulfonic acid. The absolute configurations of the major enantiomers derived from (R)‐4 are based on the retention on a Chirasil‐L‐Val capillary gas chromatography column, CD spectra, and the comparison with authentic samples of (S)‐3a, obtained from (S)‐tert‐leucine [(S)‐1] and (S)‐3d. The results demonstrate that the N – C(3) bond of the aziridinone (R)‐4 is cleaved by nucleophiles with a high degree of stereospecificity and inversion of configuration. This stereochemical course is at variance with that inferred from the methanolysis of the similar aziridinone (R)‐7. – Treatment of (R)‐4 in [D4]methanol with one equivalent of 3‐chloroperbenzoic acid (15) containing 5% of 3‐chlorobenzoic acid (16) affords carbon monoxide and the racemic oxaziridine 18 in quantitative yield, which is also obtained from the imine 19 in a very fast reaction. The acid 16 effects slow decomposition of (R,S)‐4 into carbon monoxide and imine 19, probably by general acid catalysis. The stereochemical result obtained from (R)‐4 as well as the reaction conditions and differences in rate for formation and epoxidation of 19 suggest that in the peracid oxidation of an aziridinone the sequence of events consists of a rate‐limiting, acid‐catalysed decomposition into carbon monoxide and an imine, followed by very fast epoxidation of the latter. The previous mechanism, invoking as intermediates alleged aziridinone N‐oxides, e.g. 17, is not supported by the present study.
Zur Reaktion von Halogen(trimethylsilyl)benzolen mit Elektrophilen und Basen – Carbodesilylierung und Eliminierung als Konkurrenzreaktionen
Authors: Effenberger Franz , Daub Wolfgang
Published: July 2007

Reaction of Halo(trimethylsilyl)benzenes with Electrophiles and Bases – Carbodestlylation and Elimination as Competitive Reactions

Elimination to dehydrobenzenes takes place as competitive reaction in the base‐catalyzed carbodesilylation of 1‐halo‐2‐(trimethylsilyl)benzenes 1 with carbonyl compounds 2 in the presence of furans 3, 6. Elimination is preferred with increasing leaving tendency of the halides (I > Br > > Cl > > F) and with decreasing reactivity of the carbonyl compounds. Exclusive elimination to 1,2‐didehydrobenzenes – which are trapped with furans – occurs in the reaction when no electrophiles are present.
Darstellung von Didehydropyridinen aus (Trimethylsilyl)pyridinen
Authors: Effenberger Franz , Daub Wolfgang
Published: July 2007

Preparation of Didehydropyridines from (Trimethylsilyl)pyridines

Halogen‐substituted (trimethylsilyl)pyridines 2, 3, 5 – 7 and trifluoromethylsulfonyloxy‐substituted (trimethylsilyl)pyridines 9b, 11b are obtained from 2‐ and 3‐halopyridines 1, 4 or hydroxypyridines 8, 10, and 12. Reactions of the 3‐ and 2‐(trimethylsilyl)pyridines 2,9b and 11b with bases in the presence of furans 15 give only protodesilylation or hydrolysis products but no indication is found for the formation of a 2,3‐didehydropyridine. 3‐Bromo‐4‐(trimethylsilyl)pyridine (5a) reacts with KOCMe3 in the presence of furan (15a) to give a mixture of products from which the isoquinoline derivative 20 and the tert‐butoxypyridines 23, 24 are formed by addition to 3,4‐didehydropyridine. Under comparable conditions far higher yields of 3,4‐didehydropyridines are obtained by treatment of the 3‐halo‐2,4‐bis(trimethylsilyl)pyridines 7 with strong bases.
Metallkomplexe mit Tetrapyrrol‐Liganden, LIX Redoxpotentiale, Nah‐Infrarot‐Absorption, Ionenradien sowie Ring‐Ring‐Abstand in Metall(III)‐bis(tetraphenylporphyrinat)‐Systemen mit Porphyrinringen in unterschiedlichen Oxidationsstufen
Authors: Buchler Johann W. , Hammerschmitt Peter , Kaufeld Isolde , Löffler Jürgen
Published: July 2007

Metal Complexes with Tetrapyrrole Ligands, LIX. – Redox Potentials, Near‐Infrared Absorption, Ionic Radii, and Ring‐Ring Distance in Metal(III) Bis(tetraphenylporphyrinate) Systems with Porphyrin Rings in Different Oxidation States

An extended series of tetrabutylammonium salts of bisporphyrinate double decker anions NBu4[MIII(TPP)2] (M = Y, La – Lu except Pm) is described. The complexes are characterized by UV/Vis/NIR and 1H‐NMR spectroscopy, cyclic voltammetry, and spectroelectrochemistry. The redox potentials of the new sandwich compounds and the near‐infrared absorption energies of their corresponding oxidation products M(TPP)2 and [M(TPP)2]+ are shown to depend linearly on the ionic radii of the central ions. The gradients of the first and second oxidation potentials are positive whereas those of the third and fourth oxidation potentials are negative. This result is interpreted by means of a qualitative molecular orbital diagram describing the ππ interactions of the four frontier orbitals of the two macrocycles in the double decker molecules.
Metallacyclobutene aus η2‐Cyclopropen‐Komplexen des Titanocens und Zirkonocens
Authors: Binger Paul , Müller Patrik , Herrmann Albert T. , Philipps Petra , Gabor Barbara , Langhauser Franz , Krüger Carl
Published: July 2007

Metallacyclobutenes via η2‐Cyclopropene Complexes of Titanocene and Zirconocene

(η2‐Cyclopropene)(trimethylposphane) complexes of titanocene (4, 5) and zirconocene (8) are obtained in good yields by the reaction of 1,2‐diphenylcyclopropene (2) or 4,8‐dioxaspiro[2.5]oct‐1‐ene (3) with bis(trimethylphosphane)titanocene (1) and (1‐butene)(trimethylphosphane)zirconocene (7), respectively. In solution the new complexes 4 and 8 rearrange smoothly above room temperature to give the metallacyclobutene derivatives 6 and 9. All new compounds were characterized by spectroscopic methods (31P, 1H, 13C NMR), and the crystal structure of 9 was determined by an X‐ray analysis.
Protonenaustausch in Re(CO)4(μ‐H)(μ‐PPh2)Mo(η5‐C5H5)(CO)2 gegen Triphenylphosphan‐IB‐Metallkationen
Authors: Haupt Hans‐Jürgen , Flörke Ulrich , Disse Gerd , Heinekamp Christoph
Published: July 2007

Proton Exchange in Re(CO)4(μ‐H)(μ‐PPh2)Mo(η5‐C5H5)(CO)2 Against Cationic IB Metal Phosphane Species

Decacarbonyldirheniumreacts with hexacarbonylbis(η‐cyclopentadienyl)dimolybdenum and diphenylphosphane to give Re(CO)4(μ‐H)(μ‐PPh2)Mo(η5‐C5H5)(CO)2 (1) with a Mo — Re bond as ascertained by an X‐ray structure analysis. The bridging H atom of the heteronuclear metal‐metal bond in 1 is deprotaned with DBU. The redox condensation reaction of the obtained anion1 and triphenylphosphane IB metal cations gave Re(CO)4(μ‐H)(μ‐PPh2)Mo(η5‐C5H5)(CO)2 [M = Au (2), Ag (3), and Cu (4)] containing an MReMo triangle. Their yields increase in the sequence of compounds 4 < 3 < 2. 1, 1‐, and 2 were characterized by cyclovoltammetric measurements, NMR, IR, and UV/Vis spectra.
1,3,2‐Diazaborinium‐Verbindungen — neue Heteroaren‐Kationen des Bors
Authors: Kuhn Norbert , Kuhn Annette , Lewandowski Jörg , Speis Martin
Published: July 2007

1,3,2‐Diazaborinium Compounds — New Cationic Boron Heteroarenes

The diazaborinium cation 9 is obtained by the reaction of the vinamidine boron chelate 8 with Et2O—BF3. The cyclic aluminium compound 13 forms with the dichloroboranes RBCl2 (R = Cl, Et, Ph) the cations 15,16a, and 16b. AM1 calculations demonstrate the π interaction of the boron with the nitrogen atoms as well as with the fluoro substituent.
Deprotonation of 5,6‐Dihydro‐5‐methylene‐4H‐1,2‐oxazines and Regioselective Reactions with Electrophiles
Authors: Unger Clemens , Zimmer Reinhold , Reißig Hans‐Ulrich , Würthwein Ernst‐Ulrich
Published: July 2007

5,6‐Dihydro‐5‐methylene‐4H‐1,2‐oxazine 1 is smoothly converted by n‐butyllithium into 1‐Li which reacts with electrophiles such as D2O, carbonyl compounds, dimethyl sulfide, or an azo diester to give the γ‐adducts 4a–4f. On the other hand, alkylation of 1‐Li occurs exclusively at C‐4 of the heterocycle and provides the α‐adducts 3g and 3h. These reactions require the activation of 1‐Li by tetramethylethylenediamine. Treatment with allyl bromide and methyl acrylate affords mixtures of regioisomers 3 and 4. 1,2‐Oxazine 5 with a conjugated C = C bond is less acidic than 1 but is also converted into 1‐Li, whilst compound 6, lacking the 6‐methoxy group, is not deprotonated under standard conditions. The dianion of 1,2‐oxazine 7 is generated by employing an excess of n‐butyllithium. This dianion displays a similar regiochemical behavior as 1‐Li. Deuterium is exclusively incorporated into the γ‐position to give product 8, while methylation occurs at C‐4 to produce 9. 1,2‐Oxazine 3g with an additional 4‐methyl group can also be metalated and affords γ‐adducts 10 and 11 upon reaction with D2O or acetone. Treatment with methyl iodide gives a 3:1 mixture of regioisomers 12 and 13. Deuteration of 1,2‐oxazines 14 and 16 bearing a 3‐CF3 or 3‐CO2Et substituent requires more severe deprotonation conditions to provide the γ‐adducts 15 and 17 in moderate yields. MNDO calculations of neutral 1,2‐oxazines, the corresponding carbanions, and the lithium compounds allow an insight into the structure and charge distribution of these species, and also an estimation of the relative acidities. The regioselectivity of reactions of 1‐Li is discussed on the basis of these semiempirical calculations and comparison with related ambident nucleophiles.
Photoreaktion von 3,6‐Dihydrophthalsäureanhydrid mit Alkinen
Authors: Askani Rainer , Hoffmann Jochen
Published: July 2007

Photoreaction of 3,6‐Dihydrophthalic Anhydride with Alkynes

The title compound 1 and various alkynes undergo photocycloadditions to give cyclobutenes 3 and/or tetracyclooctane derivatives 4. The proportion varies from 100% cyclobutene (3d) to 100% tetracyclooctane (4e, 1) according to the substituents on the alkyne and the temperature.
Lösliche (Tetraethylphthalocyaninato)eisen(II)‐ und ‐cobalt(II)‐Verbindungen
Authors: Beck Anton , Mangold Klaus‐Michael , Hanack Michael
Published: July 2007

Soluble (Tetraethylphthalocyaninato)iron(II) and ‐cobalt(II) Compounds

The (tetraethylphthalocyaninato)iron and ‐cobalt compounds Et4PcFe (9), Et4PcCo (8), and Et4PcH2(7) have been synthesized starting from 3,4‐dibromoacetophenone (1) via the corresponding dinitrile 5 or isoindolenine6, respectively. Et4PcFe (9) reacts withtBuNC,p‐diisocyanobenzene (dib), and me4dib to form the bisaxially coordinated compound Et4PcFe(tBuNc)2(10) and the oligomers [Et4PcFe(dib)]n(11) and [Et4PcFe‐ (me4dib)]n(12). All of the synthesized compounds, except the oligomers with a chain length of more than 8 – 14 units, are soluble in organic solvents such as chloroform or toluene. The new compounds were characterized by1H‐,13C‐NMR,13C‐CP/NMR, UV/Vis, and IR spectra. In addition the redox properties of Et4PcCo (8) were studied by cyclic voltammetry and spectroelectrochemical methods. The Mößbauer spectra of the (phthalocyaninato)iron compounds9, 11, and12demonstrate the bridged structure of [Et4PcFe(L)]n(L = dib, me4dib) (11,12). The powder conductivity of [Et4PcFe(dib)]n(11) (σRT= 5·10‐6S/cm) is ca. 106times higher than that of Et4PcFe (9) (σRT= 9·10‐12S/cm). After doping with iodine the oligomers11and12show an increase in conductivity of 105and 104, respectively (σRT≈︁ 10‐2S/cm for [Et4PcFe(dib)I0.85]n).
Über die verbesserte Darstellung von Silyl‐ und Germylkalium sowie die Synthese von Silylgermanen
Authors: Lobreyer Thomas , Oeler Johannes , Sundermeyer Wolfgang
Published: July 2007

An Improved Preparation of Silyl‐ and Germylpotassium and Synthesis of Silylgermanes

The preparation of KSiH3 and KGeH3 is improved, and several syntheses of silylgermane, H3Si – GeH3, are described. A series of other potential processing gases for PE‐CVD is prepared: H3Ge – SiR1R2R3 (R1, R2, R3 = H, H, Me; H, H, Et; H, H, tBu; H, H, Ph; H, Me, Me; Et, Et, Et; H, Me, Ph; H, Me, GeH3). A new method for the preparation of silylgermanes by the reaction of silyl esters of sulfonic acids (RSO3H, R = C4,F9, Me, Ph) with KGeH3 is reported.