Asymmetric Cobalt‐Catalyzed Regioselective Hydrosilylation/Cyclization of 1,6‐Enynes

Abstract

AbstractWe report an enantioselective cobalt‐catalyzed hydrosilylation/cyclization reaction of 1,6‐enynes with secondary and tertiary hydrosilanes employing a catalyst generated in situ from the combination of Co(acac)2 and (R,Sp)‐Josiphos. A wide range of oxygen‐, nitrogen‐, and carbon‐tethered 1,6‐enynes reacted with Ph2SiH2, (EtO)3SiH, or (RO)2MeSiH to afford the corresponding chiral organosilane products in high yields and up to >99 % ee. This cobalt‐catalyzed hydrosilylation/cyclization also occurred with prochiral secondary hydrosilane PhMeSiH2 to yield chiral alkylsilanes containing both carbon‐ and silicon‐stereogenic centers with excellent enantioselectivity, albeit with modest diastereoselectivity. The chiral organosilane products from this cobalt‐catalyzed asymmetric hydrosilylation/cyclization could be converted to a variety of chiral five‐membered heterocyclic compounds by stereospecific conversion of their C−Si and Si−H bonds without loss of enantiopurity.