Competitive reactivity of the aryl isothiocyanate dipolarophile at NC versus CS 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 NC and CS 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.