Hydrochloric Acid → 2,2-Difluoro-1,3-benzodioxol-4-ol

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Reaction Steps

15.8 g (100 mmol) of 2,2-difluoro-1,3-benzodioxole are metallated according to Example 2, at -20° C., with 70 ml (110 mmol) of n-butyllithium (1.58M in hexane) and 12.8 g (110 mmol) of TMEDA in 120 ml of hexane. To the white suspension there is added dropwise at -100° C., over a period of 5 minutes, a solution of 10.4 g (100 mmol) of trimethyl borate in 50 ml of diethyl ether. When the reaction mixture has warmed up and has been stirred for 30 minutes at room temperature, there are added to the precipitated dimethoxy-(2,2-difluoro-1,3-benzodioxol-4-yl)borane, while cooling with ice, 35 ml of 3N sodium hydroxide solution, immediately followed by the addition, over a period of 10 minutes, of 32 ml (~310 mmol) of 30% hydrogen peroxide solution. The yellow-orange emulsion is adjusted to pH 3 with 10% HCl. The aqueous phase is extracted three times with 150 ml of diethyl ether each time. The organic solutions are washed three times with 100 ml of 2N FeSO4 solution each time, then twice with 100 ml of 20% sodium bisulfite solution each time and finally with 50 ml of brine, dried over MgSO4 and concentrated in a vacuum rotary evaporator. Upon distillation of the residue, 8.4 g (48%) of the product distil over in the form of a pale yellow oil at boiling point (b.p.) 135°-139° C./25 mbar.

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