Preparation of 4-trifluoromethylbenzylboronic acid pinacol ester_Industrial additives

Preparation background and overview of 4-trifluoromethylbenzylboronic acid pinacol ester

4-Trifluoromethylbenzylboronic acid pinacol ester is an organic chemical intermediate that can be used in suzuki coupling reactions.

Preparation of 4-trifluoromethylbenzylboronic acid pinacol ester

Method 1:

Place [Cu(MeCN)_{4formylbenzeneboronic acid}]²⁺ [BF4^– ]₂ (5.0 mol%, 4.0 mg) and Xantphos (6.5 mol%, 7.5 mg) were dissolved in 0.5 mL MTBE in a dry vial in a boron trifluoride tetrahydrofuran complex glove box under argon and the reaction was stirred for 5 minute. Then, pinacol diborate (1.2 equiv, 60.9 mg), 1f (1.0 equiv, 35.2 mg) and Ti (OⁱPr)₄ (1.0 equiv , 59.2 μL) were added in this order. Finally, another 0.5 mL of MTBE was added to the mixture. The reaction was heated to 100°C under argon for 20 hours. Pass the crude mixture through a Celite pad. Then, the solvent was removed on a rotary evaporator (30 °C, 350 mbar). 2f was purified by flash chromatography (Pentane/EtOAc = 97/3), during which some decomposition occurred. Isolated yield: 92% (52.8 mg, colorless liquid). ¹HNMR (300MHz, CDCl₃)d 7.46-7.50 (m, 2H), 7.26-7.29 (m, 2H), 2.35 (s, 2H), 1.23 ( s, 12H).¹³C{1H} NMR (75MHz, CDCl₃) 143.3,129.3,127.4 (q, J_C-F = 33Hz ), 125.3 (q, J_C-F = 4Hz), 124.7 (q, J_C-F = 272Hz), 83.8, 24.9, 20.3 (wide, low intensity). ¹¹B NMR (96MHz, CDCl₃) δ32.8,

¹⁹F NMR (470MHz, CDCl₃) δ-62.6, HRMS (ASAP): m/z [M+ H] of C14H19BrF3O2 ⁺Calculated: 287.1425, Found: 287.1422.

Method 2:

Reaction conditions: Aryl tricarboxylate (0.1mmol), pinacol borate (1.5 equivalent), Pd(OAc)₂ (5mol%), PPh_{3</sub (10 mol%), base (3 equiv) in 1 mL in Ar atmosphere at room temperature using dioxane for 3-6 h. TBAOH¼tetrabutylammonium hydroxide.}