Synthesis and some reactions of ethyl (2-alkylimino-1,2-dihydro-1-azaazulen-1-yl)acetates

Ethyl (2-alkylimino-1,2-dihydro-1-azaazulen-1-yl)acetates (3) were synthesized from 2-alkylamino-1-ethoxycarbonylmethyl-1-azaazulenium salts, which were produced from 2-alkylamino-1-azaazulenes with ethyl bromoacetate. Reaction of 3 with acid anhydrides gave the mesoionic anhydro-3-acyl-1-alkyl-2-hydroxy-1,3a-diazacyclopent[a]azulenium hydroxide. Polar cycloaddition of 3 with methyl propiolate gave methyl 2-alkyl-1-oxo-1,2-dihydro-2,9b-diazaindeno[3,3a,4,5-bcd]azulene-8-carboxylate and 3-ethyl 5-methyl 2-alkylamino-2a-azabenz[cd]azulene-3,5-dicarboxylate.