Yu. Sh. Gol'dberg

Hydrosilylation of carbonyl compounds catalysed by alkali metal fluorides in the presence of crown ethers

Abstract Hydrosilylation of the C=O bond with dimethylphenylsilane proceeds readily in low-polarity solvents (dichloromethane, benzene, THF) in the presence of the catalytic pair MF/18-crown-6 (M = Cs, Rb, K), with caesium and rubidium fluorides being the most active. Using the CsF/18-crown-6 pair, the hydrosilylation of a number of aromatic and heteroaromatic aldehydes and ketones has been carried out. Silyl ethers of the corresponding alcohols have been prepared in good yields.

Alkylation of 6-Methylthio- and 6-Benzyloxyguanine under Phase-Transfer Conditions

Abstract Phase-transfer-catalyzed alkylation of 6-methylthio- and 6-benzyloxyguanine followed by acid hydrolysis provides a simple procedure for the preparation of various 9- and 7-substituted guanines.

1H, 13C and 29Si NMR study of α- and β-silylstyrenes and their adducts with dichlorocarbene

Abstract 1 H, 13 C and 29 Si NMR spectra for the α- and β-silylstyrenes ( E )-PhCHCHSiR 3 (I) and PhC(SiR 3 )CH 2 (II) (R = Cl, Me, Ph), and those for some dichlorocarbene adducts of I and II (R = Me, Ph), were examined. From the 13 C NMR data, the phenyl substituent in the molecules I and II enhances the electronic effects of the organosilicon substituent at Cα, and weakens these effects on the C α resonance. The degree to which polarization of the vinyl CC bond is polarized increases with increased electron-withdrawing properties of substituent R in the SiR 3 group in compounds I and II, and correlates with the reduced reactivity of the bond toward electrophilic dichlorocarbene. Several long-range coupling constants (CC) in the molecules I, II and in their adducts with :CCl 2 were measured. The estimated CC is a useful aid for the study of electronic effects in organosilicon compounds.

O-Alkylation of Pyridine Aldoximes Under Phase-Transfer Conditions

Abstract Phase-transfer catalysed alkylation of (E)-pyridine aldoximes with alkyl and benzyl halides in the benzene/10% aq. NaOH system in the presence of tetraoctylammonium bromide proceeds regiospecifically to afford the corresponding O-ethers in good yield.

Conversions of [2-(4,5-dihydrofuryl)]-silanes and -germanes under catalytic hydrogenation conditions

Abstract (2-Tetrahydrofuryl)-silanes and -germanes were obtained in high yield by the heterogeneous liquid-phase hydrogenation of [2-(4,5-dihydrofuryl)]trimethylsilane (I), bis[2-(4,5-dihydrofuryl)]dimethylsilane (II) and [2-(4,5-dihydrofuryl)]trimethylgermane with a Pd/Al 2 O 3 catalyst. The dihydrofurylsilanes I and II were found to undergo disproportionation and dehydrogenation, the latter being involved in both intra- and inter-molecular disproportionation.

Synthesis of 3-(2,5-dihydrofuryl)-silanes and -germanes and their transformations under catalytic hydrogenation conditions

Abstract A number of 3-triorganosilyl- and 3-trimethylgermyl-2,5-dihydrofurans have been prepared by the cyclization of 2-triorganosilyl(germyl)-2-butene-1,4-diols obtained from the hydrosilylation and hydrogermylation products of 1,4-bis(trimethylsiloxy)-2-butyne. It has been found that the liquid-phase heterogeneous hydrogenation of these compounds over palladium catalysts is accompanied by simultaneous isomerization and disproportionation to give the corresponding 3-(4,5-dihydrofuryl)-, 3-tetrahydrofuryl- and 3-furyl- derivatives.

Hydrosilylation of Pyridinealdehydes and Acetylpyridines Catalyzed by Caesium Fluoride in the Presence of 18-Crown-6

Abstract Reactions of isomeric pyridinealdehydes and acetylpyridines with dime thylphenylsi lane proceed readily in dichloromethane in the presence of catalytic amounts of CsF and 18-crown-6 to give silyl ethers of the corresponding pyridyl carbinols in good yields (50–70%).

Fluoride ion-induced hydrosilylation of aldehydes and ketones under phase-transfer conditions

Abstract The hydrosilylation of aldehydes and ketones with dimethylphenylsilane occurs readily in dichloromethane at room temperature in the presence of catalytic amounts of caesium fluoride and 18-crown-6 to afford silyl ethers of the corresponding aryl and hetaryl carbinols in good yields.

Reactions of vinylsilanes with ethoxycarbonylnitrene under phase-transfer conditions: A novel route to silicon-containing aziridines

Abstract The addition of ethoxycarbonylnitrene, generated from ethyl N -( p -nitrobenzenesulphonyloxy)carbamate under liquid-liquid phase-transfer conditions to vinyl-, α-bromovinyl- and (β-methoxycarbonylvinyl)(trialkyl)silanes affords the corresponding 1-ethoxycarbonyl-2-trialkylsilylaziridines.

Synthesis of Isopropyl and Tert-butyl Pyridyl Ketones by Alkylation of Acetylpyridines with Methyl Iodide Using Phase Transfer Catalysis

Abstract Isomeric acetylpyridines undergo regiospecific alkylation with methyl iodide under solid/liquid phase transfer conditions (aromatic solvent/KOH/18-crown-6) to give the corresponding isopropyl and/or tert-butyl pyridyl ketones, depending on reaction conditions.