Reversal of the facial diastereoselectivity in the Paternò-Büchi reaction of silyl enol ethers carrying a chiral substituent in α-position
作者:Thorsten Bach、Kai Jödicke、Birgit Wibbeling
DOI:10.1016/0040-4020(96)00610-2
日期:1996.8
diastereoselectivity in the Paternò-Büchi reaction of benzaldehyde and silyl enol ethers 1 which bear a chiral substituent R∗ in α-position has been studied. Since the regioselectivity and the simple diastereoselectivity of the photocycloaddition is very good only two diastereoisomers are obtained whose ratio reflects the facial diastereoselectivity. With the silyloxy substituted substrates 1a-1c the selectivity
研究了苯醛和甲硅烷基烯醇醚1的Paternò-Büchi反应在α位上的非对映选择性。由于光环加成的区域选择性和简单的非对映选择性非常好,因此仅获得两种非对映异构体,它们的比率反映了面部非对映选择性。使用甲硅烷氧基取代的底物1a-1c时,选择性低()。但是,苄氧基取代的甲硅烷基烯醇醚1d()已经表现出显着的非对映选择性,并且优先生成氧杂环丁烷2d()。如果底物中的苄氧基取代基被氯原子()恢复了脸部非弹性选择的方向。因此,甲硅烷基烯醇醚1e与苯甲醛的反应优选产生氧杂环丁烷3e()。