2,6-Dichloroisonicotinic acid → tert-Butyl 2,6-dichloropyridine-4-carboxylate

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Reaction Steps

A solution of 2,6-dichloroisonicotinic acid (38.4 g, 0.20 mole) in thionyl chloride (60 ml.) and cyclohexane (100 ml) containing a few drops of dimethylformamide is heated at 80° for three hours. The solution is cooled and excess thionyl chloride and cyclohexane are removed in vacuo. The residue is dissolved in chloroform (40 ml.) and added dropwise to a solution of t-butanol (50 ml.) and N,N-dimethylaniline (40 ml.). The solution is heated at reflux for six hours, cooled, diluted with diethyl ether and washed successively with water, water containing 4 ml. of concentrated sulfuric acid, water, dilute sodium carbonate solution and dried over anhydrous sodium sulfate. The solvent is removed under vacuum and the residue is crystallized from a minimum amount of methanol to give 24 g. of product, m.p. 79°-81°.

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