2,5-Dichloropyridine → 5-Chloro-2-cyanopyridine

Participants

Reaction Conditions

Reaction Steps

Add in a 22-L 3-neck round bottom equipped with overhead stirrer, reflux condenser, and thermometer, N,N-dimethylacetamide (DMAC, 6 L), 2,5-dichloropyridine (347.0 g, 2.34 mol), zinc cyanide (138.0 g, 1.17 mol), bis(diphenylphosphino)dipalladium II CH2Cl2 complex (DPPF, 20.8 g, 0.02 mol), and zinc dust (1.6 g, 0.02 mol). Slowly warm the reaction mixture to 160° C. As the temperature reaches 160° C., an exotherm (controllable) may result and the internal temperature may rise to 180-185° C. Remove the heat from the dark solution and cool the mixture slowly cool to room temperature. Extract the bulk reaction mixture by taking 2 L of the dark solution, diluting with brine (2 L), filtering over celite, and addition of ethyl acetate (4 L). Repeat the process 3 times to extract all material, and dry the combined organics over magnesium sulfate. Cautious concentration at 25-30° C. might give a dark liquid. (Note: Product volatility maybe observed at higher temperatures so the temperature upon concentration is kept low in all steps.) Stir the liquid and add water (5 L), resulting in a solid After 1 h, filter, and back-wash with water (2 L). Dry the filter cake to give 215 g of crude product. Extract the aqueous filtrate with ethyl ether (8 L). Dry the organics over magnesium sulfate and concentrate to provide 51 g of crude product. Combine with the 215 g lot and purify by chromatography over silica gel (biotage 150; eluting with 5% ethyl acetate in hexanes increasing to 10% ethyl acetate in hexanes) to provide a white solid of pure title compound (193 g, 59%); 1H NMR (CDCl3) δ 8.68 (d, J=2.0 Hz, 1H), 7.84 (dd, J=2.7, 8.6 Hz, 1H), 7.66 (d, J=8.3 Hz, 1H).

Provenance & Evidence