Synthesis
The general procedure for the synthesis of neopentyl glycol ester of biphenylboronic acid from neopentyl glycol was as follows: tetrakis(dimethylamino)diboron (9.89 g, 52.65 mmol) was slowly added to a solution of 2,2-dimethyl-1,3-propanediol (neopentyl glycol, 10.42 g, 100 mmol) in toluene (40 mL) at room temperature. The reaction mixture was then heated to 105°C, at which point dimethylamine gas began to be released. After maintaining this temperature and continuing the reaction for 60 min, the toluene solvent was removed by distillation under reduced pressure to give 11.39 g of white solid product in 95.8% yield. The crude product was purified by recrystallization from toluene to give 6.48 g of bis(neopentylglycolic acid)boron (molecular formula: C10H20B2O4; molecular weight: 225.89) in 54.5% yield. The melting point of the product was 182.5-184.5 °C. NMR hydrogen spectrum (CDCl3, 200 MHz) data: δ 0.94 (s, 12H), 3.58 (s, 6H) ppm; NMR carbon spectrum (CDCl3, 50 MHz) data: δ 22.3 (4×CH3), 31.9 (2×C), 71.7 (4×CH2) ppm. The mother liquor was retained for subsequent recrystallization.
