Synthesis of 2-Amino-2'-hydroxy-1,1'-biaryls via Cascade Benzannulation and C-N Bond Cleavage Sequence.

A serendipitous synthesis of N-substituted 2-amino-2'-hydroxy-1,1'-biaryls through an aryne annulation with indolyl β-ketonitrile/ester in a cascade manner is demonstrated. The reaction sequence involves benzyne-mediated [2 + 2] Stoltz-type cycloaddition-cleavage and intramolecular Michael addition followed by C-N bond cleavage under transition-metal-free reaction conditions. Interestingly, while [4 + 2] Diels-Alder reaction is a possible pathway, no traces of the regioisomer was isolated.