Sodium hydride → N-Methyl-4-ethynyl-4-(4-fluoro-2-nitrophenoxy)piperidine

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To a stirred solution of dimsyl sodium prepared from 43.0 g of sodium hydride (50% in oil, washed three times with hexanes) and 1100 ml of dimethylsulfoxide was added, in aliquots, 125 g of N-methyl-4-ethynyl-4-piperidinol at a rate such that the temperature remained below 23°. When the addition was complete, 167 g of 2,5-difluoronitrobenzene was added slowly dropwise at a rate such that the temperature remained below 21°. When the addition was complete, the mixture was poured into ice, extracted twice with ether, washed with saturated sodium chloride solution, and dried over anhydrous magnesium sulfate. The mixture was filtered and the filtrate was concentrated. The residue was filtered through 800 g of silica gel (70-250 mesh) and eluted with 3 l of 10% methanol/dichloromethane. Evaporation of solvent provided an oil, which crystallized on standing to yield 134 g (54%) of product. Recrystallization from cyclohexane provided the analytical sample, mp 70°-73°.

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