Sodium hydride → (R)-2-Ethyl-piperazine-1,4-dicarboxylic acid 4-tert-butyl ester 1-(4-cyclopropylmethoxy-2,6-difluoro-benzyl)ester

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A mixture of 4-cyclopropylmethoxy-2,6-difluoro-benzylalcohol (270 mg, 1.26 mM) and (R)-4-chlorocarbonyl-3-ethyl-piperazine-1-carboxylic acid tert-butyl ester (349 mg, 1.26 mM) in dimethylformamide (2 mL) was added slowly to a suspension of sodium hydride (83 mg, 55%, 1.89 mM) in dimethylformamide (2 mL). The mixture was stirred at room temperature for 5 h and partitioned between water and diethylether. Organic phases were pooled, washed with brine and dried with MgSO4 to yield after evaporation a yellow oil (585 mg). This residue was purified by column chromatography (silica gel; n-hexane/ethylacetate gradient) to yield 406 mg (71%) of the product as a yellowish oil. MS (ISP): 477.3 (M+H)+.

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