Chemical Properties
White to faint yellow crystalline powder
Uses
Di-2-pyridyl carbonate is used as a coupling agent in the esterification of carboxylic acids (e.g. 3-Cyclohexenylcarboxylic acid [C988195]). Di-2-pyridyl carbonate is also used as a reagent to synthesize active carbonates (e.g. benzyl 2-pyridyl carbonate) and carbamates (e.g. 3-Pyridyl diethylcarbamate [P992950]).
Preparation
A solution of phosgene (2.5 m in toluene, 2 mL, 5.0 mmol) was diluted with dichloromethane (8 mL) and then a solution of 2-pyridinol 853 (950 mg, 10 mmol) and triethylamine (1.214 g, 10.2 mmol) in dichloromethane (20 mL) was added at 0 ℃. The reaction mixture was stirred at 0℃ for 1 h, then washed with cold 5% NaHCO3 solution (20 mL) and cold saturated brine (20 mL), dried over MgSO4, and filtered. The filtrate was concentrated to dryness to give di-2-pyridyl carbonate, DPC, 725 (972 mg) in 90% yield. It was recrystallized from dichloromethane/petroleum ether (811 mg, 75%); mp 84–86℃. DPC has also been produced as its hydrochloride salt 877, in a more facile procedure on a larger scale, in 97% yield.
Synthesis
(b) Synthesis of di(2-pyridyl) carbonate: Under argon protection, triethylamine (10.5 mL, 75 mmol) was slowly added dropwise to a solution of anhydrous dichloromethane (500 mL) containing triphosgene (3.0 g, 10 mmol) and 2-hydroxypyridine (5.7 g, 60 mmol), keeping the reaction temperature at 0°C. The reaction mixture was then gradually warmed to room temperature and stirred continuously overnight. Subsequently, the reaction mixture was gradually warmed to room temperature and stirred continuously overnight. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure and the resulting residue was dissolved in ethyl acetate (500 mL). The organic phase was washed sequentially with saturated aqueous sodium bicarbonate (2 x 150 mL) and brine (200 mL), and then dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated to give an orange colored oil. Crystallization by mixed ethyl acetate/hexane solvent resulted in an off-white crystalline solid of bis(2-pyridyl) carbonate (3.70 g, 57% yield). The nuclear magnetic resonance hydrogen spectrum (1H NMR) data were as follows: δ 8.42 (2H, dd, J = 4.8, 1.1 Hz), 7.83 (2H, ddd, J = 7.8, 7.7, 1.8 Hz), 7.30-7.23 (4H, m).
storage
CARBONIC ACID DI-2-PYRIDYL ESTER is quite stable and can be stored under nitrogen at rt for several months without any noticeable decomposition.
References
[1] Journal of the American Chemical Society, 2004, vol. 126, # 24, p. 7452 - 7453
[2] Patent: US5563151, 1996, A
