Synthesis of potential related substances of mirtazapine

Abstract

The synthesis of three contaminants of mirtazapine 6, formed during the preparation of mirtazapine bulk drug, is described. The products are 2-methyl-1,2,3,4,10,14b-hexahydrobenzo[c]pyrazino(1,2-a)pyrido[3,2-f] azepine-2-oxide (N-oxide, 7), 1-(3-methylpyridyl-2)-2-phenyl-4-methylpiperazine (deshydroxy compound, 9), and 2-methyl-1,2,3,4,10,14b-hexahydro-10-oxo-benzo[c] pyrazino (1,2-a)pyrido[3,2-f]azepine (oxo compound 11). The structures of these compounds were established on the basis of spectral data (IR, 1H-NMR and MS).