Cobalt(diamine)-catalyzed cross-coupling reaction of alkyl halides with arylmagnesium reagents: Stereoselective constructions of arylated asymmetric carbons and application to total synthesis of AH13205

A cobalt-diamine complex catalyzes the cross-coupling reactions of primary and secondary alkyl halides with aryl Grignard reagents. It is confirmed that oxidative addition of alkyl halide to cobalt proceeds via a radical process. Optically pure Ueno-Stork halo acetals undergo diastereoselective crosscoupling reactions, the products of which are transformed into optically active THF derivatives. A sequential radical cyclization/arylation reaction under cobalt catalysis provides extremely short access to a synthetic prostaglandin AH13205.