Molecular rearrangements of 4‐iminomethyl‐1,2,3‐triazoles. Replacement of 1‐aryl substituents in 1 H ‐1,2,3‐triazole‐4‐carbaldehydes

The two structural isomers, 4 and 5 , of 1‐substituted‐4‐iminomethyl‐1,2,3‐triazoles are interconvertible when heated in dimethyl sulfoxide at 80°. The equilibrium position depends on the electronic properties of the R‐substituent, favoring 5 for R = alkyl, benzyl and anisyl, and 4 for p ‐chlorophenyl and p ‐nitrophenyl. An interesting application is the synthesis of 1‐alkyl‐1,2,3‐triazole‐4‐carbaldehydes from 1‐phenyl‐1,2,3‐triazole‐4‐carbaldehyde by Scheme I. The hydrazones 4ij and the oxime 4k do not rearrange due to an unfavorable Z‐configuration around the C N bond, whereas the acyloximino derivative 4m is converted into the nitrile 11 . The structures of the products have been fully characterized by 13 C nmr spectroscopy and the mechanistic details of the rearrangement are discussed.