Benzyl Bromide → 2-Benzyl-2,4,5,6-tetrahydro-cyclopentapyrazole-3-carboxylic acid amide

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Reaction Steps

To a stirring solution of 1,4,5,6-tetrahydro-cyclopentapyrazole-3-carboxylic acid amide (2.57 g, 17.0 mmol) in DMF (34 mL) at 25° C. was added K2CO3 (5.87 g, 42.5 mmol) followed by benzyl bromide (4.36 g g, 25.5 mmol). The reaction was stirred at ambient temperature for 16 h at which time the mixture was diluted with EtOAc (75 mL) and filtered. The filtrate was washed with H2O (100 mL) and the aqueous phase was back-extracted with EtOAc (75 mL) and CH2Cl2 (75 mL). The combined organic extracts were dried over MgSO4, filtered, and concentrated in vacuo. Purification by silica gel chromatography (50% EtOAc in hexanes gradient to 95% EtOAc in hexanes) gave 2-benzyl-2,4,5,6-tetrahydro-cyclopentapyrazole-3-carboxylic acid amide (739 mg, 3.07 mmol, 18% yield) isolated as a white solid followed by 1-benzyl-1,4,5,6-tetrahydro-cyclopentapyrazole-3-carboxylic acid amide (3.24 g, 13.4 mmol, 79% yield) isolated as a white solid.

Provenance & Evidence