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■ Catalytic Reduction of 3-(4,4-Dimethyl-5-keto-3-isoxazole)propionic Acid and Its Derivatives

Henry Feuer and Philip C. Scholl*

*Wetherill Laboratory, Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, U.S.A.

Abstract

Catalytic hydrogenation of 3-(4,4-dimethyl-5-keto-3-isoxazole)propionic acid (1) in glacial acetic acid in the presence of 5% palladium on charcoal gives 4-amino-5-methylhexanoic acid (2). Reductions of the corresponding ester, methyl 3-(4,4-dimethyl-5-keto-3-isoxazole)propionate (3) and amide, 3-(4,4-dimethyl-5-keto-3-isoxazole)propionamide (4) afford, however, γ-isopropylbutyrolactam (5). Reductions of 1 and 3 in aqueous acetic acid give 4-keto-5-methylhexanoic acid (6) and methyl 4-keto-5-methylhexanoate (7), respectively. On the other hand amide 4 is converted to 2-hydroxy-5-isopropylidene-Δ¹-pyrroline (8). Compound 8 is also obtained if 4 is reduced in acetic acid containing a small amount of hydrogen chloride.