Synthesis and some reactions of 1,2-diamino-1,3-diaza- and 1,2-diamino-1-azaazulenium salts

Abstract

Amination of azaazulenes 1–3 with O-mesitylsulfonylhydroxylamine occurs at N-1 and gives the corresponding azaazulenium salts 4–6. The treatment of the salts 4 and 6 with potassium carbonate gives 1-amino-2-imino-1,2-dihydro-1,3-diaza- and 1-azaazulenes. The structure of 1-amino-2-ethylimino-1,2-dihydro-1-azaazulene (10) was characterized by X-ray crystal structure analysis. Reaction of the salt 4 with acetic anhydride gave 2-methyl-1,3,3a,9-tetraazacyclopent[a]azulene. The reaction of the salts 4 and 5 with diethyl ethoxymethylenedicarboxylate (DEEM) in the presence of potassium carbonate in acetonitrile gave 1,3,3a,9-tetraaza- (19) and 1,3,3a-triazacyclopent[a]azulene derivatives (21) as major products, whereas the reaction in ethanol gave 1,2a,3-triaza- (17) and 2a,3-diazabenz[cd]azulene derivatives (22), respectively. Similar treatment of 6 with DEEM gave diethyl (2-ethylimino-1,2-dihydro-1-azaazulen-1-yl)aminomethylenemalonate 23, which converted to 2a,3-diazabenz[cd]azulene derivative (24). The salts 4–6 reacted with active methylene compounds such as diethyl acetonedicarboxylate, diethyl oxalacetate and ethyl pyruvate, at the N-amino group followed by a cyclization at the C-8 position on the azaazulene ring to give 1,2a,3-triaza- (25, 28, 29) and 2a,3-diazabenz[cd]azulene derivatives (26, 27, 30). Cycloaddition of the salts 4–6 with acetylenic esters in the presence of potassium carbonate proceeded regioselectively and gave 1,2a,3-triaza- (32–35) or 2a,3-diazabenz[cd]azulene derivatives (31, 36, 37, 39–41).