Asymmetric catalysis in the [2+2+2] cycloaddition of arynes and alkynes:: Enantioselective synthesis of a pentahelicene

The use of BINAP-based palladium(0) catalysts in the reaction of 7-methoxy-1,2-didehydronaphthalene (2) and dimethyl acetylenedicarboxylate (DMAD) affords non-racemic 9,12-dimethoxypentahelicene I with reasonable ees, among other cycloaddition products. This is the first example of an enantioselective, metal-catalyzed cycloaddition involving arynes.