New cyclopenta[b]-pyrroles and -pyridines by reaction of 2-azido- and 2-phosphoranylideneaminocyclopent-1-ene-1-carbaldehydes with aliphatic esters

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Abstract
A new cyclopenta [b]pyrrole has been synthesized by reaction of 2-azidocyclopent-1-ene-1-carbaldehyde with ethyl acetate and subsequent thermal cyclisation. Dicyclopenta [b,e] pyrazines have been isolated from a similar reaction with ethyl propionate or t-butyl propionate. Condensation of the corresponding iminophosphorane from 2-azidocyclopent-1-ene-1-carbaldehyde with ethyl acetate and cyclisation of the dienic iminophosphorane so obtained gave a cyclopenta[b]pyridine. The products were characterized on the basis of 1H n.m.r., i.r., and mass spectrometric results.