Regioselective Hydroacylation of 1,3-Dienes by Cobalt Catalysis

ABSTRACT: We describe a cobalt-catalyzed hydroacylation of 1,3-dienes with non-chelating aldehydes. Aromatic aldehydes provide 1,4-addition products as the major isomer, while aliphatic aldehydes favor 1,2-hydroacylation products. The kinetic profile supports an oxidative cyclization mec-hanism involving a cobaltacycle intermediate that undergoes transformation with high regio- and stereoselectivity. A modern challenge in organic synthesis is the invention ofmethods that use catalysts derived from first-row transition metals.1 A number of valuable olefin transformations, including hydrogenation,2 hydroformylation,3 and hydrovinylation,4 have been achieved by cobalt catalysis. These breakthroughs highlight Co as an attractive and complementary alternative to Rh due to its relatively low cost and high abundance. Encouraged by this progress, we recently turned our attention to developing olefin hydroacylation5−14 by cobalt catalysis.15 Brookhar