The design of diastereoselective Mukaiyama-Michael reaction of ketene silyl acetal
作者:Junzo Otera、Yukihiro Fujita、Shunichi Fukuzumi
DOI:10.1016/0040-4020(96)00478-4
日期:1996.7
The highly diastereoselective Mukaiyama-Michaelreaction has been designed. Suppression of an electron-transfer process is crucial for this purpose and the following conditions should be satisfied. (1) TiCl4 is employed as a Lewisacid. (2) Ketenesilylacetals have bulky siloxy and/or alkoxy group(s). (3) α-Enones have a bulky acyl group. The excellent syn-selectivity up to a 99:1 ratio is attained
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