Trimethylamine oxide → 2-(3-Fluoropropyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

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2.5 ml (25 mmol) of borane-dimethyl sulphide (1:1) complex were dissolved in 50 ml of dimethoxyethane and the solution was cooled to 0° C. under nitrogen. 5.3 ml (52.5 mmol) of cyclohexene were then added. The solution was stirred at 0° C. for 15 minutes, then at room temperature for 1 hour and then cooled to -10° C. 1.6 g (27 mmol) of 3-fluoropropene were condensed and then added to the foregoing solution which was then stirred at room temperature under a dry ice condenser. After 1 hour the condenser was removed and stirring was continued for a further 1 hour. 3.9 g (52 mmol) of trimethylamine N-oxide were added and the solution was stirred for 1 hour. 3.1 g (26.3 mmol) of 2,3-dimethyl-2,3-butanediol were added and the solution was stirred for 16 hours. The solution was evaporated and the residue was distilled. The distillate boiling at 35-65° C./1mm Hg was collected and purified by chromatography on silica gel using diethyl ether/ hexane (1:9) for the elution to give 1.67 g of 4,4,5,5-tetramethyl-2-(3-fluoropropyl)-1,3,2-dioxaborolane as a colourless oil; 1H NMR (250 MHz, CDCl3) δ: 0.75-0.85 (m, 2H), 1.25 (s, 12H), 1.7-1.9 (m, 2H), 4.28 (t, 1H), 4.48 (t, 1H).

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