Palladium-Catalyzed Synthesis of Enantiomerically Pure α-Substituted Allylboronic Esters and Their Addition to Aldehydes

Tartrate-derived boronic esters 2 can be subjected to palladium-catalyzed carbonyl allylations with SnCl2 to obtain enantiomerically pure α-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.