Selectivity Manipulation of Bicyclization Reactions of 1,5‐Bis(1,2‐allenylketone)s: Pd versus Rh and Electronic Effect

Abstract

Select Rh! The rhodium(I)-catalyzed double cyclization of 1,5-bis(1,2-allenylketone)s gives TNF-α inhibitor (A)-type skeletons at room temperature in acetone or 1,2-dichloroethane (DCE, see scheme; Ts=Tosyl). Compared with [PdCl2(MeCN)2], [RhCl(CO)2]2 shows excellent selectivity towards the nonaromatic CC bond. The selectivity of unsymmetrical substrates can be controlled by the electronic effect.