Visible light-enabled regioselective chlorination of coumarins using CuCl₂via LMCT excitation

Abstract

An efficient, regioselective chlorination of coumarins using earth-abundant and cost-effective CuCl2 under visible light irradiation is reported. A key feature of this protocol is the photocatalytic dissociation of copper (II)...

Light-induced homolysis of copper(ii)-complexes – a perspective for photocatalysis

“…The group of Zhang described a synthetic procedure for the efficient regioselective chlorination of coumarins 23 ( Scheme 7 ). 27 Again, LIH of CuCl 2 delivered chlorine radicals. Direct regioselective addition of the Cl radical to the 3-position of coumarin 23a would give rise to a stable benzylic radical 25 (path A).…”

Photoredox-Catalyzed Redox-Neutral Decarboxylative C–H Acylations of Coumarins with α-Keto Acid

“…These privileged scaffolds are widely present in pharmaceutical compounds and possess significant biological activities such as anticancer, anti-HIV, antimicrobial, antifungal, antioxidant, anti-inflammatory, and anticoagulant activities. − Therefore, chemists have spent a great deal of effort to develop powerful and reliable methods for the synthesis of coumarin derivatives. A quick survey of the literature highlights various synthetic methods for functionalization of coumarin at position C-3 by transition metal catalysis or photocatalysis. − Though a huge amount of progress has been achieved in C-3 functionalization, − after decades of research, practical methods for the functionalization of coumarin at position C-4 are still lacking. Among the well-known procedures, palladium-catalyzed cross-coupling and nickel-catalyzed cross-coupling were regarded as two of the predominant approaches. , Wu and Yang described nickel-catalyzed cross-coupling of 4-diethylphosphonooxycoumarins with organozinc bromides to give 4-substituted coumarins (Scheme a) .…”