Rhodium-Catalyzed Enantioselective Cycloisomerization to Cyclohexenes Bearing Quaternary Carbon Centers

We report a Rh-catalyzed enantioselective cycloisomerization of alpha, omega-heptadienes to afford cyclohexenes bearing quaternary carbon centers. Rhodium(I) and a new SDP ligand promote chemoselective formation of a cydohex-3-enecarbaldehyde motif that is inaccessible by the Diels-Alder cycloaddition. Various alpha,alpha-bisallylaldehydes rearrange to generate six-membered rings by a mechanism triggered by aldehyde C-H bond activation. Mechanistic studies suggest a pathway involving regioselective carbometalation and endocyclic beta-hydride elimination.