Cobalt-Catalyzed Allylic C(sp)-H Carboxylation with CO.

Catalytic carboxylation of the allylic C(sp)-H bond of terminal alkenes with CO 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 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)-H carboxylation showcases a facile synthesis of γ-butyrolactones from simple allylarenes via short steps.