Transalkylation and Migration of N-Substituent upon Alkylation of 1,2,3-Triazoles Containing Good Leaving N-Substituents

The synthesis of four new 1,2,3-triazole derivatives and seven 1,2,3-triazolium salts that contain an organometallic group (i.e., cymantrenyl and ferrocenyl) at either the N-1, N-2, or N-3 position was realized. The alkylation of organometallic and organic triazole derivatives was investigated, and as a result of these studies, it was found that the presence of a good leaving group at the heterocyclic nitrogen atom led to transalkylation and subsequent migration of the N-1 substituent to the N-2 position of the triazole moiety. The nucleophilicity of the counterion of the triazolium salt influenced the transalkylation and isomerization processes, which suggests that the elimination of the N-substituent most likely occurs though a concerted mechanism with nucleophilic assistance from the counterion. Thus, a new approach to the synthesis of 2,4-disubstituted 1,2,3-triazoles has been developed.