An efficient entry into pyrazol-3-ones is described starting from propenoic acids that were first transformed into the corresponding hydrazides. Oxidation of the hydrazides gave the diazenes and the latter cyclized to pyrazol-3-ones on treatment with ZrCl4. The methoxycarbonyl protection of the N-1 of the pyrazolone derivatives was easily removed under mild reaction conditions.
Intramolecular addition of acyldiazenecarboxylates onto double bonds in the synthesis of heterocycles
作者:José V. Prata、Dina-Telma S. Clemente、Sundaresan Prabhakar、Ana M. Lobo、Isabel Mourato (in part)、Paula S. Branco (in part)
DOI:10.1039/b110414d
日期:2002.2.6
Appropriate aryl-substituted unsymmetrical azodicarbonyl compounds, generated from bishydrazides by oxidation, undergo intramolecular cyclisations to furnish a variety of useful heterocycles such as N-substituted oxindoles, carbostyrils, benzazepinones, benzazocinones, benzimidazolones, benzoxazinones and pyrazolones in varying degrees of efficiency. Methods are described to remove the N-acyl groups from the heteroaromatic compounds. Under mildly acidic conditions where equal opportunities are available for an ipso or a normal cyclisation it is the former process that occurs preferentially. Evidence is presented in favour of a C-to-C migration in the ipso product for the formation of a methoxy-substituted carbostyril derivative. One of the spiro substances is shown to participate in dienone–phenol rearrangement to provide the corresponding quinolone–phenol in high yield.
The present invention relates to new carbazates of the formula (I) ##STR1## wherein A is C.sub.3 to C.sub.10 alkenyl, C.sub.2 to C.sub.10 haloalkyl, trifluoromethyl, phenyl-C.sub.1 to C.sub.3 alkyl, phenyl-C.sub.2 to C.sub.3 alkenyl, naphthyl-C.sub.1 to C.sub.3 alkyl, C.sub.3 to C.sub.7 cycloalkyl-C.sub.1 to C.sub.3 alkyl, furyl which can be nitro-substituted, diphenyl-hydroxymethyl or indazolyl which can be substituted by one or more C.sub.1 to C.sub.4 alkoxy groups; and R is C.sub.1 to C.sub.4 alkyl, and acid addition salts thereof, a process for the preparation thereof and feed additives comprising the same. The compounds of formula (I) may be used in animal husbandry due to their weight-gain increasing and fodder utilization improving effect.