N-Heterocyclic Carbene Catalyzed Synthesis of Dihydroxybenzophenones from β-Methylenals and Aurones.

N-heterocyclic carbene catalyzed synthesis of 2,2'-dihydroxybenzophenones from β-methylenals and aurones was developed. The cleavage of the C-O bond by a retro-Michael addition is the key step from the spirocyclic intermediate to final product.