Thermolysis of Triazoles as Melts - Is the 3,5-Diphenyl-1,2,4-triazole Group a Good Leaving Group?

The mechanism of the rearrangement of 4-alkyltriazoles to the corresponding 1-alkyltriazoles on the thermolysis at 330 C is shown to involve initial formation of an intermediate 1,4-dialkyltriazolium triazolate salt. The triazolate ion subsequently attacks at the alkyl group bearing 1- and 4-positions of the dialkyltriazolium ion, yielding the observed products. No evidence for unimolecular reaction steps has been found. The triazole moiety in these compounds is only a weak leaving group, which requires activation by alkylation. Unimolecular reaction steps never take place, neither from neutral triazole species nor from activated dialkyl-substituted trazolium species.