these reactions. Enhanced preference for the more sterically demanding Michael adducts is obtained with Bu(2)Sn(OTf)(2), SnCl(4), and Et(3)SiClO(4) in the former reaction while TiCl(4) gives the highest selectivity for the less sterically demanding products in the latter case. These results are interpreted in terms of alternative reaction mechanisms. The reaction of less bulky ketene silyl acetals are
Diastereoselective Mukaiyama-Michael reaction of O,S-ketene silyl acetal
作者:Yukihiro Fujita、Junzo Otera、Shunichi Fukuzumi
DOI:10.1016/0040-4020(96)00479-6
日期:1996.7
The highly diastereoselective Mukaiyama-Michaelreaction has been realized by use of O,S-ketene silylacetals. Of special importance in this reaction is the effective tuning of the stereochemical course simply by changing the double bond geometry of ketenesilylacetals. Thus, both syn- and anti-Michael adducts can be obtained on the synthetically useful levels of stereochemical purity.