In the presence of a catalytic amount of trityl salts, silyl enol ethers of thioesters react with α-substituted α,β-unsaturated cyclic ketones to afford the corresponding Michael adducts in good yields with excellent lk diastereoselectivities.
Trimethysilyl triflate in organic synthesis11Part 11 of this series. Part 10: S. Murata and R. Noyori, Tetrahedron Letters 2107 (1981).
作者:R. Noyori、S. Murata、M. Suzuki
DOI:10.1016/s0040-4020(01)93263-6
日期:——
Trimethylsilyl triflate is a powerful silylating agent for organic compounds and acts as a catalyst which accelerates a variety of nucleophilic reactions in aprotic media. The reactions proceed via one-center, electrophilic coordination of the silyl group to hetero functional groups and exhibit unique selectivities.
Aqueous Asymmetric Mukaiyama Aldol Reaction Catalyzed by Chiral Gallium Lewis Acid with Trost-Type Semi-Crown Ligands
作者:Hui-Jing Li、Hong-Yu Tian、Yan-Chao Wu、Yong-Jun Chen、Li Liu、Dong Wang、Chao-Jun Li
DOI:10.1002/adsc.200505089
日期:2005.7
generates highly effective chiral gallium Lewis acid catalysts for aqueous asymmetric aldolreactions of aromatic silyl enol ethers with aldehydes. A ligand-acceleration effect was observed. Water is essential for obtaining high diastereoselectivity and enantioselectivity. The p-phenyl substituent in aromatic silyl enol ether (2 h) plays an important role and increases the enantioselectivity up to 95%
Trimethylsilyl trifltate catalyzed aldol-type reaction of enol silyl ethers and acetals or related compounds
作者:Shizuaki Murata、Masaaki Suzuki、Ryoji Noyori
DOI:10.1016/s0040-4020(01)86671-0
日期:1988.1
condensation of enol trimethylsllyl ethers with acetals, orthoformate, or 2-acetoxytetrahydrofuran or -pyrans to give the corresponding β-alkoxy carbonylcompounds. Reaction of enolsilylethers and carboxonium triflate ion-pair intermediates occurs via acyclic transition states and exhibits moderate to high erythro selectivity independent of the geometry (E/Z) of the enolsilylethers.
aldol reactions in water using a catalytic amount of diarylborinic acid have been developed. The reactions proceeded smoothly in the presence of a small amount of an anionic surfactant and a Brønsted acid. Water was the most suitable solvent, and organic solvents such as ether and dichloromethane were ineffective in this system. Use of bis(4-trifluoromethylphenyl)borinic acid gave high catalytic activity