Asymmetric synthesis of [7]helicene-like molecules

A new approach to nonracemic [7]helicene-like molecules has been developed. Stereoselective Col-mediated [2 + 2 + 2] cycloisomerization of aromatic triynes containing an asymmetric carbon atom produces [7]helicene-like scaffolds in diastereomeric ratios up to 100:0. This central-to-helical chirality transfer can be controlled by the absolute configuration at the asymmetric center and by the presence of carbon substituents.