A Facile Approach to 4,5-Dihydro[1,2,4]triazolo[3,2-d][1,5]benzoxazepines

Abstract

The novel tricyclic heterocycles of 4,5-dihydro[1,2,4]triazolo[3,2-d][1,5]benzoxazepine derivatives were prepared by the cycloaddition of the corresponding bicyclic cationic 1,3-dipoles, which were easily generated from the azoacetates by reaction with AlCl₃ as a Lewis acid, to the triple bond of nitriles along with the consecutive ring expansion. The formation of products deviating from the normal reaction aptitudes was observed and the mechanistic aspects are discussed herein. Crystal diffraction analysis for two of the products unequivocally established the respective structures proposed.

Key words

1-aza-2-azoniaallene cations - cycloaddition - nitriles - ring enlargement - benzoxazepine

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