TAUTOMERISM OF 5,5-DIPHENYLDIHYDRO-4H-1,2,3-TRIAZOL-4-ONE AND 5-AMINO-4,4-DIPHENYL-4H-1,2,3-TRIAZOLES

Methylation of the 5-amino-4H-1,2,3-triazole 5 affords the N-methyl- (12) and the N,N-dimethylaminotriazole 13. X-ray diffraction analyses show that the tautomer Sb exists in the crystal and that 5b and 13 possess similar structures and atomic distances. Both compounds exhibit restricted rotation of the amino groups in solution. The comparison of UV, carbon-13 and nitrogen-15 spectra of the tautomeric triazoles 2 and 5 with those of the N-methyl compounds 3 and 13 demonstrates that the tautomers 2a and 5b are strongly favoured also in solution.