0-Hydroxylaminobenzaldehydes and the N-Acylated Derivatives Thereof
Joseph M. Muchowski* and Michael L. Maddox
Chemistry, Roche Palo Alto, 3431 Hillview Avenue, Palo Alto, CA 94304, U.S.A.
Received March 9, 2005 ]]> Accepted March 29, 2005
Abstract
Ethyl acetate solutions of o-hydroxylaminobenzaldehydes (1a, 8c, 8d) can be generated by reduction of the corresponding nitro compounds with zinc and ammonium chloride in a two phase ethyl acetate-water system at room temperature, but 2-nitro-3,6-dimethoxy-benzaldeyhde (4b) is converted into the anthranil 11 under these conditions. The N-acylated compounds derived from 1a and 8c exist exclusively as the cyclic tautomers (6a-c and 9a) in solution and in the solid state, whereas the N-acetyl compound 9b is in equilibrium with the open chain form 10 in solution, but only the cyclic form is present in the solid state. The N-acylated-o-hydroxylaminobenzalde-hydes undergo a novel internal redox reaction on thermolysis generating o-acylaminobenzoic acids which are converted into 2-substituted-4H-3,1-benzoxazin-4-ones (e.g., 6b→12b→13b) to a greater or lesser extent under the reaction conditions.
Keywords: O-hydroxyaminobenzaldehydes, reduction, anthranil, N-acyl, benzoxozinones.
Resumen
Soluciones de o-hidroxilaminobenzaldehídos (1a, 8c, 8d) en acetato de etilo se pueden generar por medio de la reducción del correspondiente compuesto nitro con zinc y cloruro de amonio en un sistema bifásico de acetato de etilo-agua a temperatura ambiente, sin embargo, el 2-nitro-3,6-dimetoxibenz-aldehido (4b) se convierte en el antralino 11 bajo estas condiciones. Los compuestos N-acilados derivados de 1a y 8c existen exclusivamente como los tautómeros cíclicos (6a-c y 9a) en solución y en el estado sólido, mientras que el compuesto N-acetilo 9b esta en equilibrio con la forma abierta 10 en solución, pero solo la forma cíclica está presente en el estado sólido. Los N-acilados o-hidroxilaminobenzaldehídos sufren una nueva reacción oxidoreductiva interna bajo termólisis generando ácidos o-acilaminobenzóicos los cuales son convertidos en 2-substituidos-4H-3,1-benzoxazin-4-onas (e.g., 6b→12b→13b) en mayor o menor grado, bajo las condiciones de reacción.
Palabras clave: O-hidroxiaminobenzaldehídos, reducción, antranilo, N-acilo, benzoxazinones.
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References and Notes
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