Allenylsilanes [1] and allylsilanes [2] have been successfully used by Danheiser etal. and Knçlker etal. as nucleophiles in reactions with activated alkenes using Lewis acids in formal [3+ 2] cycloadditions for the formation of substituted cyclopentanes. Analogous transformations with heteroolefins C= X (X= O, NR) have also been accomplished to provide the corresponding five-membered heterocycles.[3] These annulations occur through initial ...
