Synthesis and resolution of a 1,1′-biazulene analogue of BINOL

Abstract

Biaryls exhibiting axial chirality have been extensively exploited in fields such as asymmetric catalysis, but the biaryl linkage typically consists of benzenoid aromatic rings, with non-benzenoid biaryls being scarce. Here we report the first preparation of a (non-benzenoid) 1,1′-biazulene-2,2′-diol (“1,1′-BAzOL”) in enantiopure form and determine its barrier to racemisation. Furthermore we transformed a 1,1′-biazulene-2,2′-diol into the corresponding 2,2′-bis(phosphonate), thereby demonstrating functional group interconversion through cross coupling and highlighting the potential for diversification.