Synthesis of optically active β-lactams by the reaction of 2-acyl-3-phenyl-l-menthopyrazoles with CN compounds

The reaction of 1-acyl-3,5-dimethylpyrazoles 1 with C?N compounds was kinetically controlled with syn stereoselectivity through a lithium enolate intermediate using lithium diisopropylamide. In contrast, the anti stereoselective reaction of 1 was caused by the action of diisopropylethylamine in the presence of magnesium bromide under the thermodynamic control. Reaction of 2-acyl-3-phenyl-l-menthopyrazoles 12 with C?N compounds was observed in higher chemical and optical yields with the predominant 2′S configuration. An especially diastereomerically pure product was isolated in the reaction of 2-propanoyl-3-phenyl-l-menthopyrazole ( 12a ) with N-benzylidene-4-toluenesulfonamide ( 2 ). The products from N-acyl-pyrazoles and C?N compounds were further cyclized into β-lactams directly or with short conversion steps.