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[摘要]：A direct microwave-assisted one-pot Beckmann rearrangement of 3-acyl-2-(alkylamino)quinolin-4-(1H)-ones in ethanol-pyridine (2:1) provided 2,3-dialkylimidazo[4,5-b]quinolin-9-ols, e.g., I, as major products along with 2-alkyl-N-alkyloxazolo[4,5-c]quinolin-4-amines, e.g., II, and 3-alkyl-N-alkylisooxazolo[4,5-c]quinolin-4-amines, e.g., III, as minor products. Reactions of 3-acylquinolin-4-(1H)-ones contg. secondary amine substituent at C-2 gave 2-alkyloxazolo[5,4-b]quinolin-9-ols as major products via elimination of the secondary amine group. A mechanism proposed for the formation of Beckmann rearrangement products involves initial generation of a nitrilium ion intermediate, which is trapped either by the adjacent nitrogen of the g-amino group to form imidazoquinolinols or by the oxygen of g-hydroxy group of the tautomeric form of the ketoxime to form oxazoloquinolinamines. |
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