A Convergent Pd-Catalyzed Asymmetric Allylic Alkylation of dl- and meso-Divinylethylene Carbonate:Enantioselective Synthesis of (+)-Australine Hydrochloride and Formal Synthesis of Isoaltholactone

摘要

The use of a mixture of dl-and meso-divinylethylene carbonate as an electrophile in palladium-catalyzed asymmetric allylic alkylation reactions is reported.From the diastereomeric mixture of meso and chiral racemic starting materials,a single product is obtained in high optical purity employing either oxygen or nitrogen nucleo-philes.The resulting dienes have proven to be versatile synthetic intermediates as each carbon is functional-ized for further transformation and differentiated by virtue of the reaction.A mechanism for this intriguing transformation is proposed and a concise enantioselective total synthesis of (+)-aus-traline hydrochloride is reported as well as a formal synthesis of isoaltholactone.