Sodium hydride → 4-Ethoxycarbonyl-4-(3,5-difluorophenyl)-2-methyltetrahydropyran

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Reaction Steps

Sodium hydride (60% w/w dispersion in mineral oil, 9.17 g) was added portionwise to a solution of ethyl 3,5-difluorophenylacetate (17 g) in THF (400 ml) and the mixture was stirred at ambient temperature for 1 hour. A solution of 1,5-diiodo-2-methyl-3-oxapentane (30.3 g) in THF (20 ml) was added dropwise and the mixture was stirred at ambient temperature for 2 hours. The mixture was filtered and the filtrate was evaporated. The residue was purified by column chromatography using a 19:1 v/v mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained, as a mixture of diastereoisomers, 4-ethoxycarbonyl-4-(3,5-difluorophenyl)-2-methyltetrahydropyran (16.5 g). The mixture of diastereoisomers was separated by further chromatography using a 10:1 v/v mixture of petroleum ether (b.p 40°-60° C.) and ethyl acetate as eluent. There was thus obtained:

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