Chlorosuccinimide → N-(5,6-Dichloropyridin-2-yl)pivalamide

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To a solution of N-(6-chloropyridin-2-yl)pivalamide, synthesized as in J. Org. Chem 2005, 70, 1771, (1.02 g, 4.80 mmol) in chloroform (25 mL) was added 1-chloropyrrolidine-2,5-dione (0.62 g, 4.67 mmol) and the mixture was refluxed in an oil bath for 3 hrs. It was allowed to cool to room temperature overnight. The reaction mixture was evaporated in vacuo and re-dissolved in DMF (15 mL). Another 480 mg 1-chloropyrrolidine-2,5-dione was added and the resulting solution was heated overnight in an oil bath at 95-100°, then cooled again to room temperature. The solvent was removed in vacuo and the residue was partitioned between water and ethyl acetate. The aqueous phase was washed twice more with ethyl acetate and the combined organic phases were washed with brine, dried over magnesium sulfate, and evaporated in vacuo. TLC (10% ethyl acetate/hexane) showed a robust spot at Rf 0.6 with smaller spots at Rf 0.4 and 0.2. The material was subjected to the Biotage in 5-10% ethyl acetate/hexane, collecting the Rf 0.6 fraction to give 790 mg (66%) white solid, N-(5,6-dichloropyridin-2-yl)pivalamide. 1H NMR (500 MHz, CDCl3) δ ppm 8.17 (s, 1 H), 7.96 (s, 1 H), 7.72 (s, 1 H), 1.31 (s, 10 H). MS (LC/MS) R.T.=1.85; [M+H]+=248.8.

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