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
Trimethylsilyl enol ethers bearing trialkylsilyl-protected hydroxy groups were converted into synthetically valuable bifunctional alkenyl nonaflates under the action of nonafluorobutane-1-sulfonyl fluoride combined with potassium fluoride in the presence of catalytic amounts of dibenzo-18-crown-6. The methodology has been demonstrated for structurally diverse substrates possessing various trialkylsilyl-protected hydroxy groups which remained intact during the reaction course.