Abstract
Abstract The reactions of 2- and 8-(substituted amino)-1-azaazulenes with dimethyl acetylenedicarboxylate (DMAD) were investigated. Treatment of ethyl 2-acetylamino-1-azaazulene-3-carboxylate with DMAD in refluxing acetonitrile gave 9-ethyl 1,2,3-trimethyl 3a-azacyclopent[a]azulene-1,2,3,9-tetracarboxylate, 5-ethyl 1,2,2a,3-tetramethyl 4-acetyl-2a,3-dihydro-4H-4, 10b-diazapentaleno[1,6-aj]azulene-1,2,2a,3,5-pentacarboxylate (3a), and dimethyl (10-ethoxycarbonyl-4-methoxycarbonyl-2,4a-dihydro-2-oxo-2H-1,4a-diazabenz[a]azulen-3-yl)maleate. Compound 3a thermally rearranged to 9-ethyl 2,3,10,11-tetramethyl 1-acetyl-2,3,4,4a-tetrahydro-1H-1,4-diaza-3,4a-ethenofluorene-2,3,9,10,11-pentacarboxylate. The reaction of ethyl 2-alkylamino-1-azaazulene-3-carboxylate with DMAD gave the corresponding 4-alkyl-2a,3-dihydro-4H-4,10b-diazapentaleno[1,6-aj]azulene derivatives, and the etheno-bridged 1-azaheptalene derivative. The reaction of 8-ethylamino-3-phenyl-1-azaazulene with DMAD gave trimethyl 1-phenyl-2a-azabenz[cd]azulene-3,4,5-tricarboxylate, tetramethyl 6-ethyl-1-phenyl-4a,5-dihydro-6H-2a,6-diazapentaleno[1,6-cd]azulene-3,4,4a,5-tetracarboxylate, tetramethyl 3-phenyl-9b-azaindeno[1,6,7-bcd]azulene-1,2,8,9-tetracarboxylate, and dimethyl [8-phenyl-1,2,3-tris(methoxycarbonyl)-8H-3a-azacyclopent[1,2-a]inden-8-yl]maleate. However, the reaction of 8-acetylamino-3-phenyl-1-azaazulene with DMAD gave dimethyl-1-phenyl-2a,5-diazabenz[cd]azulene-3,4-dicarboxylate, trimethyl 3-phenyl-8,9b-diazaindeno[1,6,7-bcd]azulene-1,2,9-tricarboxylate, dimethyl 3-phenyl-8,9b-diazaindeno[1,6,7-bcd]azulene-1,2-dicarboxylate, tetramethyl 6-acetyl-1-phenyl-4a,5-dihydro-6H-2a,6-diazapentaleno[1,6,7-cd]azulene-3,4,4a,5-tetracarboxylate. The structures of the obtained compounds were determined by inspections of their physical and spectral data, and by single-crystal X-ray analyses of some of these compounds. The reaction mechanisms of these reactions are discussed.
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