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Regioselectivity in the Reaction of Nitroquinoxaline‐N‐Oxides With Phosphoryl Chloride

par Hinkens, Raymonde ;Vande Vyver, Gisèle;Nasielski, Jacques
Référence Bulletin des Sociétés chimiques belges, 95, 8, page (663-670)
Publication Publié, 1986

Article révisé par les pairs

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Résumé :

6‐nitro‐, 2‐methyl‐6‐nitro‐ and 2,3‐dimethyl‐6‐nitroquinoxaline have been transformed into their N‐oxides by MCPBA in chloroform; the nitro group orients the oxygen atom preferentially to nitrogen atom N1, but the N4:N1 selectivity is diminished in the methylated derivatives. Under the action of POCl3 (the Meisenheimer reaction), the N‐oxides of the unmethylated compounds are transformed into chloro‐nitroquinoxalines having lost the N‐oxide oxygen atom. The orientation of the entering chloride ion is discussed on the basis of electronic effects induced by the N‐oxide and nitro groups, and it is suggested that the last step, the elimination of “HPO2Cl2” is a concerted process. Copyright © 1986 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim