THE DIMERIZATION OF (E)-1,3-DIPHENYL-1,3-BUTADIENE PROCEEDS SUPRAFACIALLY WITH RESPECT TO BOTH COMPONENTS - EVIDENCE FOR A CONCERTED [4+2]-CYCLOADDITION

Despite the potential stabilization of diradical intermediates through the phenyl groups, the thermal dimerization of (E)‐1,3‐diphenyl‐1,3‐butadiene does not follow a diradical mechanism as previously assumed, but a concerted pathway. The case examined here is the dimerization of the deuteriated diene 1 giving 2, which proceeds suprafacially with regard to both diene and dienophile. (Figure Presented.) Copyright © 1995 by VCH Verlagsgesellschaft mbH, Germany