Allylstannanes reactions

The first example of truly catalytic, enantioselective allylation of imines has been reported by Yamamoto [46a]. These authors had first discovered that imines could undergo allylation reaction via a palladium-catalyzed allylstannane reaction to afford the corresponding homoallylamines in high yields [47a, 47b,... 

Interestingly, changing the radical trap from allylstannane to allylsilane increased the enantioselectivity of these allylations from 76% ee to 90% ee (Eq. 6) [10]. The by-product in the allylstannane reactions is tin halide, which is itself a Lewis acid which can promote achiral allylations. In addition, it was observed that a simple change in Lewis acid reversed the sense of stereoinduction. 

---