Quinoxaline Derivatives. XII. The Reactions of Quinoxaline 1,4-Dioxides with Acetic Anhydride

Article abstract of DOI:10.1246/bcsj.60.1145

Quinoxaline 1,4-dioxide (XIIIa) with acetic anhydride gave 1-acetoxy-2(1H)-quinoxalinone (XIVa) which was prone to facile hydrolysis to yield 1-hydroxy-2(1H)-quinoxalinone (XVa).Both XIVa and XVa were isolated from the reaction mixture.On prolonged heating with acetic anhydride, XIIIa, XIVa and XVa were converted slowly to the same end product, 2,3(1H,4H)-quinoxalinedione (XXa). 6-Ethoxy- (XIIIb), 6-methoxy- (XIIIc), and 6-methylquinoxaline 1,4-dioxide (XIIId) behaved similarly, except that the attack of the reagent took place exclusively on N-oxide para to the electron-donating substituents, and none of the other expected isomeric compounds XVIIb-d were isolated.Whereas 6-chloroqinoxaline 1,4-dioxide (XIIIe) bearing an electron-attracting chloro substituent on the benzene ring gave exclusively the other isomers XVIIe, XVIIIe, and XXe.A mechanism for this novel rearrangement is proposed and discussed.