Visible-light-induced radical cascade cyclization of pyrazoles bearing a coumarin unit

Abstract

Herein, we have described an efficient, eco-friendly, metal free, visible light catalysed synthesis of coumarin based pyrazoles under an open atmosphere involving a photoredox catalyst, which is an inexpensive organic dye. The present strategy is the first example of visible light promoted, aerobic, oxidative cyclization of pyrazoles bearing a coumarin unit via the formation of C–C, C–O and C–N bonds to afford excellent yields of the products in a simple one-pot operation under mild reaction conditions. The major advantages of the present methodology include short reaction time, cost effectiveness, easy work-up, broad substrate scope and high atom economy.