3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)nitrobenzene

3-Nitrophenylboronic Acid Pinacol Ester is used in the preparation of [(pyrimidoindolyl)phenyl]benzamide derivatives and analogs as Janus kinase inhibitors.

3-Nitrophenylboronic acid pinacol ester was prepared as follows: in a dry tubular reactor under argon, 3-nitrophenyl diazonium tetrafluoroborate (1 mmol) and ferrocene (10 mol, 1.8 mg) were dissolved in 2 mL of anhydrous CH3CN. Diisopropylaminoborane (2 mmol, 226 mg) was then added to this solution and the mixture was stirred at room temperature for 2 h 30 min. The reaction mixture (2 mL) was quenched by slow addition of anhydrous MeOH at 0 C and stirred for another 1 hour at room temperature. After removing all volatiles, 1.3 equivalents of pinacol were added to Et2O (2 mL) and the mixture was stirred at room temperature for 4 hours. The crude mixture was washed with 50 g / L CuCl2 solution (2 x 5 mL). The organic layer was separated, dried with Na2SO4, filtered and concentrated to dryness. The resulting oil was dissolved with CH2Cl 2 and filtered through a silica gel pad, eluting with CH2Cl2 to give the corresponding boronic acid ester 3-nitrophenylboronic acid pinacol ester.