To a mixture of tert-butyl 4-bromophenylcarbamate (1.67 g, 6.14 mmol), potassium carbonate (3.38 g, 24.46 mmol), and tetrakis(triphenylphosphine)palladium (365 mg, 0.316 mmol), was added 4,4,6-trimethyl-2-(3,3,3-trifluoroprop-1-en-2-yl)-1,3,2-dioxaborinane (1.64 g, 7.39 mmol), and degassed 1,2-dimethoxyethane (40 mL) and water (20 mL). The mixture for refluxed for 2 hours, cooled to ambient temperature, added more of 4,4,6-trimethyl-2-(3,3,3-trifluoroprop-1-en-2-yl)-1,3,2-dioxaborinane (475 mg, 2.14 mmol) and tetrakis(triphenylphosphine)palladium-(189 mg, 0.164 mmol), and refluxed for 5 hours. The reaction mixture was cooled to room temperature, filtered, diluted with water (200 mL), extracted twice with ethyl acetate (200 mL), washed with brine, dried (Na2SO4) and concentrated to an orange oil. The residue was purified by silica gel chromatography (AnaLogix® SF25-40G; 50 micron silica; eluted with 0-15% ethyl acetate in hexane at 30 mL/min) to provide the title compound (1.223 g, 4.26 mmol, 69.4% yield) as a yellow solid. 1H NMR (300 MHz, DMSO-d6) δ ppm 9.53 (s, 1H), 7.52 (d, J=8.8, 2H), 7.40 (d, J=8.4, 2H), 6.03-5.99 (m, 1H), 5.97-5.94 (m, 1H), 1.48 (s, 9H); MS (DCI/NH3) m/e 305 (M+NH4)+.
