Highly Stereoselective Cobalt(III)-Catalyzed Three-Component C-H Bond Addition Cascade

A highly stereoselective three-component C(sp(2))-H bond addition across alkene and polarized -bonds is reported for which Co-III catalysis was shown to be much more effective than Rh-III. The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp(2))-H bonds undergo the three-component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five-membered lactones. Additionally, the first asymmetric reactions with Co-III-catalyzed C-H functionalization are demonstrated with three-component C-H bond addition cascades employing N-tert-butanesulfinyl imines. These examples represent the first transition metal catalyzed C-H bond additions to N-tert-butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines.