Vicinal alkylation-carboxymethylation of electron-poor alkenes by radical-chain reactions with O-alkyl O-silyl ketene acetals and their [3+2]annulation by reaction with O-cyclopropylcarbinyl O-silyl ketene acetals

摘要

O-Silyl ketene acetals of the type H_2C=C(OR)OSiMe_2Bu~t,in which R is a tertiary or secondary alkyl group,react with electron-poor alkenes to bring about vicinal alkylation-carboxymethylation of the latter.When R is a cyclopropyldimethylcarbinyl group such reactions take a more complex course involving ring opening of the cyclopropylcarbinyl radical and lead ultimately to [3+2]annulation of the alkene.