Reductive cyclization of 8-(2-nitrophenyl)-1-azaazulene derivatives; Formation of 6a,7-diazanaphth[3,2,1-c d]azulene and 7H-1,7-diazaindeno[1,2-e]azulene systems, a new DNA intercalater

Reaction of ethyl 2-dimethylamino-8-(2-nitrophenyl)-1-azaazulene-3-carboxylate with hexamethylphosphorous triamide gave ethyl 6-dimethylamino-6a, 7-diazanaphth[3,2,1-cd]azulene-5-carboxylate (7b) and ethyl 2-dimethylamino-7H-1,7-diazaindeno[1,2-e]azulene-3-carboxylate (8b). The structures of 7b and 8b were determined by X-Ray structure analyses. Compound (8b) was intercalated to Calf-Thymus DNA and a 12-mer DNA with binding constants K-D = 1.55 x 10(6) and 1.75 x 10(6) M-1, respectively.