SYNTHESIS OF A SERIES OF 3-ARYL-1-METHYLTRIAZENE 1-OXIDES WITH SUBSTITUENTS IN THE ORTHO OR PARA POSITION IN THE ARYL GROUP

A series of 3-aryl-1-methyltriazene 1-oxides, with a variety of substituents in the ortho or para position, have been prepared by coupling of the appropriate diazonium salt with N-methylhydroxylamine. The substituents range from electron withdrawing, i.e., CO2Et, NO2, CN, COCH3, Br, and CF3, to electron releasing, i.e., OCH3. In all cases studied, the triazenes exist as the 1-oxide tautomer; there is no evidence for the presence of a 3-hydroxy tautomer in any of these cases. The 1-oxide structures have been confirmed by IR and NMR spectroscopy and by elemental analysis of new compounds. In the case of the -CO2Et and -CN substituents, a significant change to lower frequency is seen in the N-H vibration frequency in the IR spectra when the substituent is moved from the para to the ortho position. This change can be readily explained by the presence of intramolecular H-bonding, which is confirmed by the NMR spectra. The presence of an ortho substituent with H-bonding potential (i.e., CO2Et, -COCH3, or NO2) causes a downfield shift of the N-H proton resonance.