A bio-inspired synthesis of hybrid flavonoids from 2-hydroxychalcone driven by visible light

Abstract

A bio-inspired synthesis of hybrid flavonoids from 2-hydroxylchalcone is described. Under the irradiation of 24 W CFL, 2-hydroxychalcone reacts with various nucleophiles to deliver structurally diverse hybrid flavonoids in good to excellent yields in the presence of a catalytic Brønsted acid. Moreover, moderate enantioselectivities could be obtained using a catalytic chiral phosphoric acid <i>via</i> counter anion directed addition. Based on mechanistic studies, the reaction is proposed to proceed <i>via</i> tandem double-bond isomerization/dehydrated cyclization of 2-hydroxychalcone to form a transient flavylium cation, which is <i>in situ</i> captured by nucleophiles to afford hybrid flavonoids.