Allylstannation: X. Stereochemical course of the addition reactions of ( E/Z-Bu 3SnCH 2CHCHCH 3 with aldehydes in the presence of Lewis acids (Bu 2SnCl 2, BF 3·Et 2O, and TiCl 4)

Abstract

Reactions between ( E/Z)-Bu 3SnCH 2CHCHCH 3 and RCHO (R  CH 3, C 2H 5, n-C 3H 7, n-C 4H 9, n-C 5H 11, (CH 3) 2CH, (CH 3) 3C, C 6H 5, CH 2CH, CH 2C(CH 3), ( E)-CH 3CHCH, ( E)-C 3H 7CHCH, ( E)-C 6H 5CHCH) have been carried out in the presence of Lewis acids such as Bu 2SnCl 2, BF 3·Et 2O and TiCl 4. The stereochemical course of the reactions to give homoallylic alcohols does not necessarily depend on the formation of intermediate Lewis acid-aldehyde complexes, but rather upon the formation of allylmetal compounds (e.g., Bu 2ClSnCH 2CHCHCH 3, Bu 2ClSnCH(CH 3)CHCH 2, Cl 3TiCH 2CHCHCH 3, etc.) which are the actual species which react with the carbonyl compounds. Bu 3SnCH 2CHCHCH 3 does not undergo the reaction.