4‐(4,4,5,5‐Tetramethyl‐1,3,2‐dioxoborolan‐2‐yl)‐isoxazole

[928664-98-6] C9H14BNO3 (MW: 195.11) InChI = 1S/C9H14BNO3/c1-8(2)9(3,4)14-10(13-8)7-5-11-12-6-7/h5-6H,1-4H3 InChIKey = LXCICYRNWIGDQA-UHFFFAOYSA-N (Suzuki coupling reagent, acetonitrile anion equivalent1, 2) Physical Data: mp 109–112 °C. Solubility: soluble in most organic solvents (EtOAc, CH2Cl2, DMSO, DMF, alcohols, and ethers). Form Supplied in: white crystals; commercially available. Analysis of Reagent Purity: purity is analyzed by 1H NMR (300 MHz, CDCl3) δ 1.32 (s, 12H), 8.41 (s, 1H), 8.68 (s, 1H). 13C NMR:(75 MHz, CDCl3) = 24.8, 84.1, 152.3, 164.7; 11B NMR (96 MHz, CDCl3) δ 29.0; IR-ATR: vmax (film) = 3100 (m), 2984 (m), 2935 (m), 1590 (s), 1447 (s), 1406 (m), 1374 (s), 1333 (s), 1285 (m), 1217 (s), 1143 (s), 1106 (s), 982 (s), 685 (s); MS (EI, 70 eV): m/z (%) = 195 (8) [M+], 180 (100), 153 (13), 138 (8), 126 (14), 111 (16), 96 (30), 85 (25), 69 (14), 58 (59). Preparative Methods: prepared by lithiation of 4-bromo isoxazole (n-BuLi, THF, argon atmosphere, −78 °C) followed by quenching with triisopropyl borate. Acidification with 1 N HCl and esterification with pinacol led to the title compound (eq 1). (1) Purification: the product is readily purified by silica gel column chromatography (EtOAc/Cyclohexane = 1:4, Rf = 0.15). Handling, Storage, and Precautions: air stable; can be stored for several months; treatment with water/acid causes hydrolysis to the boronic acid.