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 TV-methylhydroxylamine. The substituents range from electron withdrawing, i.e., CO 2 Et, NO 2 , CN, COCH 3 , Br, and CF 3 , to electron releasing, i.e., OCH 3 . 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 -CO 2 Et and -CN substituents, a significant change to lower frequency is seen in the NH 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., CO 2 Et, -COCH 3 , or NO 2 ) causes a downfield shift of the NH proton resonance.