Hydrochloric Acid → 7,8-Difluorochroman-6-ol

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Reaction Steps

81.2 ml (0.13 mol) of n-BuLi (15% soln. in hexane) are added to a soln. of 20.0 g (0.12 mol) of 7,8-difluorochroman in 400 ml of THF at −70° C. After 3 h at this temperature, 14.4 ml (0.13 mol) of trimethyl borate are added dropwise, and the batch is warmed to RT. 30 ml of dilute acetic acid (about 30%) are added, and 30 ml of aqueous hydrogen peroxide solution (35%) are carefully added to the batch. When the addition is complete, the mixture is stirred at RT for 17 h. Water is added, and the batch is acidified using 2 N hydrochloric acid. The solution is extracted a number of times with MTBE, and the combined organic phases are washed successively with water, sat. sodium chloride soln. and ammonium iron(II) sulfate soln. The solution is dried using sodium sulfate and evaporated to dryness. The crude product is purified by column chromatography (SiO2, n-heptane: MTBE=2:1).

Provenance & Evidence