1H-Indene-2-boronic acid pinacol ester

10485-09-3

25015-63-8

749869-98-5

The general procedure for the synthesis of 2-(1H-inden-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolanes from 2-bromoindene and pinacolborane was carried out as follows: under nitrogen protection (PPh3)2PdCl2 (0.54 g, 0.77 mmol) and 2-bromoindene (4.98 g, 25.54 mmol) were added to a pre-oven-dried Schlenk flask followed by addition of dioxane (50 mL). Triethylamine (10.7 mL, 76.6 mmol) and pinacolborane (5.56 mL, 38.31 mmol) were added sequentially via syringe at room temperature (25 °C). The reaction mixture was stirred at 80 °C for 5.5 hours. After completion of the reaction, it was cooled to room temperature, the reaction was quenched with water and saturated saline (20 mL) was added. The organic layer was separated and the aqueous layer was extracted with ether (2 x 50 mL). The organic layers were combined, washed with brine, dried over anhydrous Na2SO4 and concentrated. Purification of the residue by Kugelrohr distillation gave the target product 2-(1H-inden-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane as a white solid (melting point 73-74 °C) in 69% yield. The product is stable in air and can be stored and handled.1H NMR (300 MHz, CDCl3) δ 7.58 (s, 1H), 7.50 (d, J = 7 Hz, 1H), 7.46 (d, J = 7 Hz, 1H), 7.30-7.21 (m, 2H), 3.54 (s, 2H), 1.33 (s, 12H); 13C NMR (75 MHz, CDCl3) δ 147.0, 145.7, 145.0, 126.3, 126.0, 124.0, 122.0, 83.6, 41.7, 25.1.