Diels-Alder approach to biaryls (DAB): importance of the ortho-nitro moiety in the [4 + 2] cycloaddition.

A series of nitrophenyl acetylenes were evaluated for their utility in a cycloaddition-cycloreversion approach to polysubstituted biaryls. ortho-Nitrophenyl acetylene consistently provided the target biaryls in superior yields as compared to the meta and para nitro substituted variants.