REACTION OF 2-AMINO-1-AZAAZULENES AND 2-(SUBSTITUTED AMINO)-1-AZAAZULENES WITH CHLORO-KETENE, PHENYL-KETENE AND DIPHENYL-KETENE

Chloro- and phenyl-ketene react with 2-amino-1-azaazulene 1 to give 4, 4a-dihydro-1,4a-diazacyclopent[a]azulen-4-one derivatives 2a and 2b as cycloadducts, With 2-alkylamino-1-azaazulenes 4 chloroketene reacts t o give anhydro-3-hydroxy-1,3a-diazacyclopent[a]hydroxide derivatives 5 , whereas phenylketene gives -1,2,3,4-tetrahydro-1,10-diazabenz[a]azul en-2-ones 6, 2-alkylamino-3-phenylacetyl-1-azaazulenes 7 and -benzyl-1 ,2-dihydro-1,10-diazabenz[a]azulen-2-ones 8. The structures of compoun ds 5a, 6a and 8a are deduced by X-ray structural analysis, These react ions are interpreted in the terms of the hard-soft-acid-base principle .