Synthesis of Pyrazolone Derivatives. XXXI. Asynmetric Synthesis of 3a-Alkyl-3, 3a, 4, 5, 6, 7-hexahydro-2H-indazol-3-ones

抄録

The reaction of pimelyl dichloride and (-)-menthol gave (-)-(1R, 2S, 5R)-dimethyl pimelate (I), which was cyclized by the Dieckmann reaction to give (-)-(1R, 2S, 5R)-menthyl 2-oxocyclohexanecarboxylate (II). Alkylation of II gave (-)-(1R, 2S, 5R)-menthyl 1-alkyl-2-oxocyclohexanecarboxylates (IIIa-c), which were condensed with hydrazine hydrate in ethanol to give 3a-alkyl-3, 3a, 4, 5, 6, 7-hexahydro-2H-indazol-3-ones (Va-c). The compounds (Va, b) were found to be optical active. The condensation of ethyl 2-oxocyclohexanecarboxylate with (-)-(1R, 2S, 5R)-methyl carbazate (VII) gave (-)-(1R, 2S, 5R)-menthyl 3-hydroxy-4, 5, 6, 7-tetrahydro-2H-indazole-2-carboxylate (IX), whose reaction with benzyl bromide gave (-)-(1R, 2S, 5R)-menthyl 1-benzyl-3-oxo-2, 3, 4, 5, 6, 7-hexahydro-1H-indazole-2-carboxylate (X) and (-)-(1R, 2S, 5R)-menthyl 3a-benzyl-3-oxo-3, 3a, 4, 5, 6, 7-hexahydro-2H-indazole-2-carboxylate (XI). The hydrolysis of XI gave Va. However, the compound Va obtained by this method did not show optical rotation.