An anomalous course of the reduction of 2-(3-oxo-3,4-dihydroquinoxalin-2-yl)benzene diazonium salt: A reinvestigation

The 1H,13C and 15N NMR spectra of the reduction product of 2‐(3‐oxo‐3,4‐dihydroquinoxalin‐2‐yl)benzene diazonium salt with sodium sulfite were measured and analysed. It is shown that the reaction product corresponds to 1‐(indazol‐3‐yl)‐1,2‐dihydro‐benzimidazol‐2‐on and not 6H‐quinoxalino[1,2‐c] [1,2,3]benzotriazin‐12(13H)‐one as published previously. The correctness of the structure was confirmed by an independent synthesis. The observed 15N chemical shifts were compared with the predicted ones using the ACD/NNMR 9.01 program. Copyright © 2006 John Wiley & Sons, Ltd.