New fused quinoxalines: Synthesis and reactions of pyrimidothienoquinoxaline and oxadizolylthienoquinoxalines

Abstract

Diazotization of 3-amino-2-ethoxycarbonylthieno[2,3-b]quinoxaline 1 gave the diazonium salt 2 which was reacted with SO2 and N-methylaniline to give sulfamoylquinoxaline derivatives 3-5. Imidazothienoquinoxaline 8 was obtained from the reaction of carboxylic acid hydrazide 6 with nitrous acid and followed by boilling the carboazide 7 in dry xylene. Also, compound 6 react with CH(OEt)3 to give aminopyrimidine 9 which was reacted with arylidene malonodinitrile, furfural and/or dimethoxy-tetrahydrofuran to afford compounds 10, 11 and/or 12 respectively. Refluxing of 6 with CS2 gave oxadiazolylthienoquinoxaline 13, reaction of 13 with hyrazine hydrate, CH(OEt)3, nitrous acid, CS2 and α-halocompounds to give 14-19.