Synthesis and investigation of mass spectra of some nitrogen heterocycles

ABSTRACT

2, 3-diphenyl-l, 2-dihydro-quinoxaline [2], 2, 3-diphenyl-quinoxaline [3] and 2, 3-diphenyl-l, 2, 3, 4-tetrahydro-quinoxaline [4] were prepared via the reaction of benzoin with o-phenylene diamine under different reaction conditions. Acylation of 2 and 4 with acetic anhydride yielded the corresponding N-acetyl [5] and N, N-l, 4-diacetyl derivative [7], respectively. Bromination of 2 with bromine gave the corresponding 6, 7-dibromo-2,3- diphenyl-quinoxaline [6]. 2, 3, 5, 6-tetraphenylpyrazine [8] and l-[benzylidene] amino-4, 5-diphenyl-l,5-dihydro-imidazoldine-2-thione [9] were synthesized by treatment of benzoin [1] with thiourea and benzaldehyde-thiosemicarbazone. The electron impact mass spectra of both of the above series of compounds have also been recorded and their fragmentation pattern is discussed