Triphenylphosphine → ethyl 1-{2-[(tert-butoxycarbonyl)amino]propyl}-3-(phenoxymethyl)-1H-pyrazole-5-carboxylate

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Reaction Conditions

Reaction Steps

Di-tert-butyl azodicarboxylate (2.52 g, 10.96 mmol) was added to a stirred solution of triphenylphosphine (2.87 g, 10.96 mmol), 2-hydroxy-rac-1-methyl-ethyl-carbamic acid tert-butyl ester (2.13 g, 12.18 mmol) and 5-phenoxymethyl-2H-pyrazole-3-carboxylic acid ethyl ester (1.5 g, 6.09 mmol) in THF (45 mL). The mixture was stirred at 120° C. for 20 minutes under microwave irradiation and the solvents evaporated in vacuo. The crude product was purified by open column chromatography (silica; AcOEt in DCM 0/100 to 10/90). The desired fractions were collected and the solvents evaporated in vacuo to yield rac-2-(2-tert-butoxycarbonylamino-propyl)-5-phenoxymethyl-2H-pyrazole-3-carboxylic acid ethyl ester (5.58 g, 91% yield, 40% pure) as a colorless oil that crystallized upon standing in white crystals.

Provenance & Evidence