Palladium-catalyzed synthesis of enantiomerically pure alpha-substituted allylboronic esters and their addition to aldehydes.

Tartrate-derived boronic esters 2 can be subjected to palladium-catalyzed carbonyl allylations with SnCl(2) to obtain enantiomerically pure alpha-substituted allylboronic esters 8 and 9. The reaction proceeds regioselectively and with high, simple diastereoselectivity to form anti-products. Their addition to aldehydes yields enantiomerically enriched homoallylic alcohols 17 and 18, respectively. Synthesis, characterization, and a mechanistic rational is presented here.