Base-Promoted Chemodivergent Construction of 2H-Chromen-2-one and Chromeno[2,3-c]pyrrole Scaffolds from para-Quinone Methides and α-Alkylidene Succinimides.

Herein, we evolve a base-promoted synthesis of 2H-chromen-2-one and chromeno[2,3-c]pyrrole scaffolds via (4 + 2) annulation of α-alkylidene succinimides with 2-hydroxyphenyl-substituted para-quinone methides (p-QMs). Extremely selective and switchable cyclizations were obtained by modifying the base. This metal-free protocol is highlighted by its mild reaction conditions and broad substrate scope, and the viability of the existing protocol was additionally illustrated by gram-scale synthesis and further modification. Several control experiments were performed to understand the reaction mechanism.