Investigations On Synthesis Of Quinoxaline And Oxazepinone Derivatives

Pyrrolo[1,2-a]quinoxaline,imidazo[1,5-a]quinoxaline,quinoxaline and oxazepinone play important roles in nitrogen-containing heterocycle,and garnered significant attention for their abundant bioactivities.Many synthetic strategies have been reported for the preparation of above compounds.However,most of these methods suffer from harsh reaction conditions,complex manipulation,critical product isolation procedures and unsatisfactory product yields which limit their use in green chemistry.We developed construction of quinoxaline using PTSA as catalyst,modification of quinoxaline using Pd(TFA)2 as catalyst,construction of oxazepinone using Cu2O as catalyst,and construction of Pyrrolo[1,2-a]quinoxaline and imidazo[1,5-a]quinoxaline using I2 as catalyst,respectively.Several series of target compounds were obtained in good to excellent yields under mild reaction conditions with excellent functional group compatibility.1.An efficient PTSA catalyzed one-pot two-step oxidative system for cyclization of o-diaminobenzene with 1,2-diaryl-2-hydroxyethanone to quinoxalines was described.A nontoxic,readily available oxidant-DMSO was applied in this process.A broad range of substrates were applied to this method,and target compounds were obtained with good yields.2.A large library 5,8-distyrylquinoxaline fluorophores were obtained in good-to-excellent yields viathe palladium-catalyzed oxidative C-H/C-H cross-coupling of electron-deficient fluorinated quinoxalines with electron-rich styrenes.The directly coupled fluorophores,named Qu-Fluors,exhibit tunable color emissions with quantum yields up to 83%and large Stokes shifts up to 6236 cm-1 in CH2Cl2.The bioimaging performance of Qu-Fluors is shown to have potential as NIR fluorescent probes for Mitochondria.3.An efficient Cu-catalyzed cascade reaction protocol was developed for the synthesis of fused oxazepinone derivatives via sp2 C-H and O-H cross-dehydrogenative coupling.A readily available catalyst,Cu2O,was used in this modular and convergent approach.An unusual Smiles rearrangement reaction was involved in this synthesis.The various reaction parameters were evaluated and optimized,and the target compounds were obtained in good-to-excellent yields.4.An efficient I2-catalyzed cascade coupling protocol was developed for the synthesis of pyrrolo[1,2-a]quinoxaline and imidazo[1,5-a]quinoxaline derivatives via sp and sp C-H cross-dehydrogenative coupling.A nontoxic,readily available catalyst,I2,and an oxidant,DMSO,were used in this metal-free process.The target compounds were obtained in good-to-excellent yields with a broad substrate scope.