Study On C3-Arylation And Alkylation Of Quinoxalinones

Quinoxalinones,especially C3-substituent quinoxalin-2(1H)-one derivatives are important motifs in many medicinally important compounds and natural products.In this thesis,an efficient method for palladium-catalyzed direct Hiyama coupling of various quinoxalin-2(1H)-ones with aryl siloxanes has been developed.The transitionmetal-free decarbonyl alkylation of aryl ketone compounds with quinoxalinones has also been investigated.The main contents are as follows:1.Palladium-catalyzed direct Hiyama arylation of quinoxalin-2(1H)-ones with aryl siloxanesAn efficient method for palladium-catalyzed arylation of various quinoxalin2(1H)-ones using aryl siloxanes as coupling reagents has been achieved.The reaction of quinoxalin-2(1H)-ones with triethoxy(aryl)silane was carried out in the presence of Pd(OAc)2 as catalyst,1,10-phenanthroline as ligand in H2O under oxygen for 9 h.Under the optimized conditions,most of the C3-arylated 1-methylquinoxalin-2(1H)one derivatives could be obtained in reasonable yields.The method has considerable advantages of mild reaction condition,a simple procedure and a broad substrate scope.Owing to using water as a solvent and oxygen as an oxidant,this method is an environmental-friendly protocol for the synthesis of biological and pharmaceutical interest quinoxalin-2(1H)-ones scaffolds.2.Metal-free decarbonyl alkylation of quinoxalinones with aryl ketones An efficient method for transition-metal-free decarbonyl alkylation of aryl ketone compounds with quinoxalinones has been studied.The reaction of quinoxalin-2(1H)ones with aromatic ketones was carried out in the presence of DBU as base,TEMPO as additive in a mixture of DMSO/EtOH(1:1)at 120℃ under air atmosphere for 10 h.The desired 3-alkylquinoxalin-2(1H)-one compounds were obtained in 86%isolated yield.Under the optimized conditions,a series of 3-alkyl substitute quinoxalinones were obtained in moderate to good yields(scheme 2).We believe this facile work can be widely utilized in industrial processes and laboratory methods.