Helical Phenanthrenes, Part 5. Synthesis of Pentahelicene-7,8-dione via Intramolecular Benzoin Condensation
The intramolecular benzoin condensation of [1,1'-binaphthyl]-2,2'-dicarbaldehyde ( 5 ), followed by oxidation with air, provides a new synthesis of ( MP )-pentahelicene-7,8-dione ( 1 ). With reference to the original preparation of this quinone via acyloin condensation, its present yield (73% for the ring-closing step) is considerably increased.