v-Triazolines. Part 34. Thermal behaviour of 1-(2-aminophenyl)-4,5-dihydro-5-morpholino-1,2,3-triazoles: new synthesis of 2-alkylquinoxalines

Abstract

4,5-Dihydro-5-morpholino-1-(2-nitrophenyl)-1,2,3-triazoles 4 are prepared by reaction of an aldehyde with morpholine and the appropriate aryl azide. On reduction 1-(2-aminophenyl)-4,5-dihydro-5-morpholino-1,2,3-triazoles 5 are formed. Thermal rearrangement of compounds 5 affords unstable 2-alkyl -3-amino -1,2,3,4-tetrahydroquinoxalines 7, which undergo deamination to 2-alkyl-1,2-dihydroquinoxalines 8. Oxidation of these affords 2-alkylquinoxalines 10. The mechanism of the thermal rearrangement of triazoles 5 is investigated and discussed.