MOLECULAR-REARRANGEMENTS OF 4-IMINOMETHYL-1,2,3-TRIAZOLES - REPLACEMENT OF 1-ARYL SUBSTITUENTS IN 1H-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-degrees. 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 C-13 nmr spectroscopy and the mechanistic details of the rearrangement are discussed.