Remote asymmetric induction using allylstannanes

Abstract

Allylstannanes are becoming useful reagents for stereoselective organic synthesis. In this review, the transmetallation of allylstannanes with heteroatom functionality at the 4-, 5-, and 6-positions using tin(IV) halides is discussed. This generates allyltin trihalides in which the electron deficient tin is coordinated to the heteroatom. These intermediates react with aldehydes to give homoallylic alcohols with excellent levels of 1,5-, 1,6-, and 1,7-asymmetric induction. Significantly, the double-bonds of the homoallylic alcohols are formed exclusively with the Z-geometry. Similar remote stereoselectivity is observed in reactions of the heterofunctionalised allylstannanes with imines, except in this case, the double-bonds in the products have the E-geometry. Aspects of the mechanisms of these reactions are discussed together with the origin of the stereoselectivity. This chemistry provides a new approach to remote stereochemical control which should find application in synthesis.