Synthesis of hexahelicene and 1-methoxyhexahelicene via cycloisomerization of biphenylyl-naphthalene derivatives.

The new approach provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key biphenylyl-naphthalenes and their platinum-catalyzed double cycloisomerization. This sequence of reactions provides a synthetic route to helicenes in two steps from simply accessible building blocks. Furthermore, the method enables the introduction of substituents into the hexahelicene skeleton. The strategy developed is exemplified by the synthesis of 6,10-dimethylhexahelicene and 1-methoxy-6,10-dimethylhexahelicene.