Preparation background and overview of potassium 3-pyridyl trifluoroborate
Potassium 3-pyridyltrifluoroborate can be used as a pharmaceutical synthesis intermediate. It can be prepared from 4-methoxyboronic acid as the reaction raw material, or pyridin-2-ylboronic acid as the reaction raw material.
Preparation of potassium 3-pyridyl trifluoroborate
Preparation Report 1 of Potassium 3-Pyridyl Trifluoroborate,
Add a solution of potassium hydrogen difluoride (2.06g, 26.3mmol) in H2O (15mL) to a solution of 4-methoxyboronic acid (6.60mmol) in methanol (15mL) to obtain White precipitate. The mixture was stirred at room temperature (18°C) for 2 hours and then concentrated under reduced pressure to reveal a white solid. The product was extracted with 20% methanol in acetone (3 × 20 mL). The extracts were combined and concentrated until a small amount of precipitate was observed. Add diethyl ether (40 mL) to promote precipitation, filter the precipitate, wash with diethyl ether (2 × 5 mL cyclopentopyridine), and dry on a Buchner flask to obtain 3-pyridyl potassium trifluoroborate, yield 1.14 g, 76%. Melting point (℃): 235-236; measured value: 235-236.
Preparation report 2 of potassium 3-pyridyl trifluoroborate,
To a solution of pyridin-2-ylboronic acid (1.0 g, 8.93 mmol methyltetrahydrofuran) in MeOH (2.6 mL) at 0°C under nitrogen protection was added portionwise KHF2 (2.09g, 26.8mmol). Then continue adding H2O (5.95 mL, 4.5 M) dropwise to the suspension at 0°C. Remove the ice-water bath and stir the reaction at room temperature until 11BNMR indicates the reaction is complete (~2 minutes). The crude mixture was concentrated and dried under vacuum overnight, and the crude solid was purified by successive Soxhlet extractions (4 h) using acetone (60 mL). The collected solvent was concentrated and then redissolved in a minimum amount of acetone (5 mL) and diethyl ether (30 mL) was added to precipitate the product. The product was filtered, concentrated, and dried under vacuum to obtain the pure compound 3-pyridyl potassium trifluoroborate (1.08 g, 8.03 mmol) in a yield of 90%.
References
[1] Suzuki-Miyaura Coupling Reactions of Iodo(difluoroenol) Derivatives, Fluorinated Building Blocks Accessible at Near-Ambient Temperatures
[2] Scope of the Suzuki-Miyaura Cross-Coupling Reactions of Potassium Heteroaryltrifluoroborates
