Transition-metal-free cascade benzannulations for synthesizing 2-hydroxybenzophenones.

A set of cascade benzannulations of readily accessible chromone-3-carboxaldehydes and γ-nitroaldehydes for synthesizing biologically relevant 2-hydroxybenzophenones has been developed. The cascade was found to provide a transition-metal-free strategy for synthesizing 2-hydroxybenzophenones in acceptable yields (up to 57%).