Stereoselective Cyclopropylmethylation Reactions of Homoallylstannanes with Carbon Electrophiles

The reactions of homoallylstannanes with acetals, aldehydes, and acyl chlorides in the presence of a Lewis acid proceeded smoothly to give the corresponding cyclopropylmethylated products. The reactions of E-3-pentenylstannane with aldehydes were stereoselective and gave the erythro products predominantly. A mechanism involving antiperiplanar attack is suggested. The stereoselectivity of the Z isomer was, however, not high.