Cobalt-Catalyzed Allylic C(sp~3)-H Carboxylation with CO_2

摘要

Catalytic carboxylation of the allylic C-(sp~3)-H bond of terminal alkenes with CO_2 was developed with the aid of a Co/Xantphos complex. A wide range of allylarenes and 1,4-dienes were successfully transformed into the linear styrylacetic acid and hexa-3,5-dienoic acid derivatives in moderate to high yields, with excellent regioselectivity. The carboxylation showed remarkable functional group tolerability, so that selective addition to CO_2 occurred in the presence of other carbonyl groups such as amide, ester, and ketone. Since styrylacetic acid derivatives can be readily converted into optically active γ-butyrolactones through Sharpless asymmetric dihydroxylation, this allylic C(sp~3)-H carboxylation showcases a facile synthesis of γ-butyrolactones from simple allylarenes via short steps.