Studies into diastereoselective Dِtz benzannulations for the synthesis of axially chiral biaryls

A series of racemic chiral ortho substituents on 1-phenylhex-1-yne have been found to control the atroposelective formation of a biaryl from Dötz benzannulation with pentacarbonyl(methoxyphenylmethylene)chromium(0). The results show there is a subtle balance between the chiral ortho substituent controlling atroposelectivity with a dr 3–5:1 and allowing benzannulation to proceed in yields of 44–67%.