N,1-dihydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbimidoyl chloride → 5-(5-(3,5-dichlorophenyl)-5-(perfluoroethyl)-4,5-dihydroisoxazol-3-yl)-3,3-dimethylbenzo[c][1,2]oxaborol-1(3H)-ol

To a solution of N,1-dihydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbimidoyl chloride (378 mg, 1.58 mmol) and 1,3-dichloro-5-(3,3,4,4,4-pentafluorobut-1-en-2-yl)benzene (506 mg, 1.74 mmol) in DMF (5 mL) at rt was added TEA (176 mg, 1.74 mmol). The reaction mixture was stirred at rt for 18 h, poured into ice-water and extracted with EA (20 mL). The organic layer was washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was purified by column chromatography to give the final desired title compound 5-(5-(3,5-dichlorophenyl)-5-(perfluoroethyl)-4,5-dihydroisoxazol-3-yl)-3,3-dimethylbenzo[c][1,2]oxaborol-1(3H)-ol (180 mg; 23% yield) as a white solid. 1H NMR (400 MHz, DMSO-d6): δ 9.22 (s, 1H), 7.82 (s, 2H), 7.77-7.70 (m, 3H), 7.60 (s, 1H), 4.55 (d, J=18.4 Hz, 1H), 4.32 (d, J=17.2 Hz, 1H), 1.48 (s,6 H) ppm; HPLC purity: 97.7% at 220 nm and 99.5% at 254 nm; MS: m/z=496.3 (M+, ESI+).