Synthesis of Hindered Biaryls via Aryne Addition and in Situ Dimerization

Benzynes generated under Knochel conditions from 2-iodophenylsulfonates and (PrMgCl)-Pr-i smoothly add to thiol, selenol, and amine nucleophiles. Treatment of the resulting aryl Grignard intermediate with a copper salt and an organic oxidant then affords symmetrical biaryls in good yield. 3-Substituted arynes undergo regioselective addition, enabling synthesis of atropisomeric biaryls with chelating S, Se, or N groups in the 2,2' positions.