Visible Light-induced Heterogeneous Catalytic Synthesis Of Quinoxaline-2(1H)-one Condensed Heterocyclic Compounds

Heterocycles are widely present in natural products,drugs and bioactive molecules,showing important research value and application prospects in many fields such as pharmaceutical,agriculture and materials.59%of US FDA-approved drugs are composed of nitrogen heterocycles.Radical cascade cyclization has proven to be an extremely valuable approach in the construction of complicated carbo-and heterocycles,showing high atom and step-economy.With the development of visible light-catalyzed organic synthesis in recent years,the conversion of traditional chemical conversion by heating into visible-light-induced photochemical processes has obvious advantages such as greenness and sustainability.Therefore,the development of new methods for photocatalysis,especially heterogeneous catalysis,to synthesize new heterocyclic frameworks is an important research direction in the contemporary synthesis field.Quinoxaline-2(1H)-one compounds are an important class of nitrogen-containing heterocyclic units.Due to their important chemical and biological activities,they show good application value in natural products and drug molecules.It is particularly worth pointing out that synthetic works using quinoxaline-2(1H)-one as the starting material has basically focused on the alteration of its C3 functional group for the past many years,and the synthetic alteration of these diverse functional group derivatives is mainly achieved through the radical addition and subsequent oxidation mechanism shown in the figure below.However,new methods for synthesizing more complex functionalized fused heterocyclic compounds using quinoxaline-2(1H)-one as the starting material via tandem cyclization reactions initiated by radicals are rarely reported.This dissertation developed(?)a novel approach that visible-light-induced CsPbBr3catalyzed radical tandem cyclization reaction for the construction of a class of polyfused heterocycles,tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones by employing quinoxalin-2(1H)-ones with N-arylglycines as reaction substrates in one pot;(?)using the same starting materials,a new method for the solvent-controlled selective synthesis of a series of dihydroquinoxalin-2(1H)-ones and tetrahydroimidazo[1,5-a]quinoxalin4(5H)-one compounds using metal-free g-C3N4 as a heterogeneous photocatalyst has been developed as shown below.The specific research contents are as follows:1.Using perovskite as photocatalyst to synthesize a series of fused heterocyclic tetrahydroimidazo[1,5-a]quinoxaline-4(5H)-oneBy employing quinoxalin-2(1H)-ones and N-arylglycines as starting material and recyclable perovskite(CsPbBr3)as a heterogeneous photocatalyst,a large variety of poly-fused heterocycles,tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones were prepared in green solvent(DMC:dimethyl carbonate)in one pot under white-light irradiation conditions.Great advantages of this strategy include highly efficient ring formation,the use of easily available and recyclable catalyst,green solvent,wide substrate scope,mild reaction conditions,etc.2.using g-C3N4 as a photocatalyst to selective synthesis of a series of fused heterocyclic tetrahydroimidazo[1,5-a]quinoxaline-4(5H)-ones and dihydroquinoxalin2(1H)-ones through solvent controlBy employing quinoxalin-2(1H)-ones and N-arylglycines as starting material and metal-free g-C3N4 as a heterogeneous photocatalyst,a series of dihydroquinoxalin2(1H)-ones were prepared using DMSO/H2O as a mixed solvent;and a variety of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones were synthesized employing EtOH as a solvent.This reaction system offers advantages including high chemoselectivity,the use of metal-free and recyclable heterogeneous catalysts,simple and easy operation,short reaction time,metal/additive/oxidant-free and mild reaction conditions.