Competitive reactivity of the aryl isothiocyanate dipolarophile at N[double bond, length half m-dash]C versus C[double bond, length half m-dash]S with nucleophilic 1,3-dipoles: a combined experimental and theoretical study. The reactions of substituted 1,2,3-triazolium-1-aminide 1,3-dipoles with aryl isothiocyanates: new tricyclic thiazolo[4,5-d][1,2,3]triazoles

Abstract

Substituted 1,2,3-triazolium-1-aminide 1,3-dipoles react with aryl isothiocyanates at both the N[double bond, length half m-dash]C and C[double bond, length half m-dash]S sites to give mixtures of substituted imidazolo[4,5-d][1,2,3]triazoles and new thiazolo[4,5-d][1,2,3]triazoles including tricyclic derivatives with the C-3a and C-6a bridgeheads linked via (CH₂)₄ and phenanthro groups. The product distribution is controlled by the para-substituent of the aryl isothiocyanate. Theoretical calculations, 3-21G* and 6-31G*, suggest that linear triple bonded canonical forms of the aryl isothiocyanate system play a key role in the ambident reactivity of these systems.

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