Acetaldehyde → 5-Ethyl-2-nitro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine

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Reaction Steps

A 150-mL single-neck round-bottomed flask equipped with a magnetic stirrer was charged with methanol (60 mL), 2-nitro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine 205a (1.5 g, 8.9 mmol), ZnCl2 (2.43 g, 17.8 mmol), acetaldehyde (784 mg, 17.8 mmol), and NaBH3CN (1.12 g, 17.8 mmol). The mixture was stirred at room temperature for 2 h and concentrated under reduced pressure. The residue was purified with silica-gel column chromatography eluting with 40:1 petroleum ether/ethyl acetate to afford 208a (1.4 g, 81%) as a yellow oil. MS-ESI: [M+H]+ 197

Provenance & Evidence