α-Thiosubstituted chiral imines/secondary enamines: their use in the asymmetric Michael reaction
摘要:
The asymmetric Michael reaction between 2-thiosubstituted chiral imines/secondary enamines derived from (S)I-phenylethylamine and electrophilic alkenes (methyl acrylate, MVK) was investigated. 2-Phenylthio derivatives furnished the expected Michael adducts with excellent ee. By contrast, an in situ elimination of p-toluenesulfenic acid took place when using the p-toluenesulfinyl analogs. (C) 2000 Elsevier Science Ltd. All rights reserved.
Stereocontrolled Reduction of 2-(<i>p</i>-Tolylsulfinyl)cycloalkanones under Basic Conditions: π-Facial Selection in Cyclic Systems Directed by a Chiral Side Chain
作者:Katsuyuki Ogura、Michio Ishida、Makoto Fujita
DOI:10.1246/bcsj.62.3987
日期:1989.12
Reduction of a 2-(p-tolylsulfinyl)cycloalkanone with sodium borohydride in methanol–triethylamine is accompanied by rapid epimerization at C2. Under the conditions employed here, the π-facial selectivity of the reduction is directed by the side chain chirality and, among four possible isomers of the corresponding cycloalkanol, one isomer is given with high selectivities up to 85%.
Ketones are reported to be conveniently converted into their α-tolylsulfinylated derivatives. This new procedure is based on the reaction of their corresponding trimethylsilyl enol ethers with p-toluenesulfinyl p-tolylsulfone in the presence of tris(dimethylamino)sulfur trimethylsilyldifluoride (TAS-F). Considering that β-ketosulfoxides are key intermediates for the preparation of α,β-unsaturated ketones