Stereospecific decarboylative allylation of sulfones

Abstract

Allyl sulfonyl acetic esters undergo highly stereospecific, palladium-catalyzed decarboxylative allylation. The reaction allows the stereospecific formation of tertiary homoallylic sulfones in high yield. In contrast to related reactions that proceed at -100 °C and require highly basic preformed organometallics, the decarboxylative coupling described herein occurs under mild non-basic conditions and requires no stoichiometric additives. Allylation of the intermediate α-sulfonyl anion is more rapid than racemization, leading to a highly enantiospecific process. DFT calculations indicate that the barrier for racemization is 9.9 kcal/mol and thus the barrier of allylation must be <9.9 kcal/mol.