Studies on Ketene and Its Derivatives. LXXXII. Reaction of Diketene with N-Phenylhydroxylamine Derivatives

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The reaction of diketene with N-arylhydroxylamine (Ia-g) gave N-hydroxyaceto-acetanilide derivative (VI), as a main product, besides the formation of azobenzene derivative (II), azoxybenzene derivative (III), 2-methylindole derivative (IV), and 2-aryl-5-methyl-4-isoxazolin-3-one (V). In the cases of Ia, Ic and Id, the reaction gave 2'-acetonyl-acetoacetanilide derivative (VIIa, c, d), which on hydrolysis with alkali was transformed to 1, 5-dihydro-4-methyl-2H-1-benzazepin-2-one derivative (VIIIa, c, d). In the formation of 2-methylindole derivative from Ic and Ie, reactions proceeded regiospectifically to give 2, 6-dimethylindole (IVc) and 6-chloro-2-methylindole (IVe), respectively. Similarly in the formation of compound VII from Ic, the reaction gave a sole product (VIIc). The reaction mechanisms are also discussed in connection with the structural elucidations.