In a dry reaction flask, 2-chloropyridine (1 mmol) was dissolved in hot acetone. Then, excess iodomethane was added to the reaction mixture with stirring. The resulting mixture was stirred at room temperature for three hours. After the reaction was complete, the reaction solution was directly evaporated, and the resulting solid precipitate was 2-Chloro-1-methylpyridinium iodide.
Figure: Synthetic route of 2-Chloro-1-methylpyridinium iodide
2-Chloro-1-methylpyridinium iodide is a reagent in a wide variety of dehydrative coupling reactions. It is also used to form carboxylate esters from acids and alcohols, carboxamides from acids and amines, lactones from -hydroxy acids and carbodiimides from N,N-disubstituted thioureas.
Condensation reagent for the synthesis of esters and ketenes, and for the kinetic resolution of carboxylic acids and alcohols.
2-Chloro-1-methylpyridinium iodide (Mukaiyama reagent), is a commonly used reagent in organic synthesis for the activation of the hydroxy group of alcohols and carboxylic acids. It is used to synthesize derivatives of esters, lactones, amides, lactams, and ketenes from the corresponding carboxylic acids. It is also used as an efficient coupling reagent in the synthesis of peptides because of its low toxicity, simple reaction conditions, and also less expensive than EDC.
Purify it by dissolving in EtOH and adding dry Et2O. The solid is washed with Me2CO and dried at 20o/0.35mm. Store it in the dark. Attempted recrystallisation from Me2CO/EtOH/pet ether (b 40-60o) causes some exchange of the Cl substituent by I. The picrate has m 106-107o, and the perchlorate has m 212-213o. [Jones et al. J Am Chem Soc 111 1157 1989, UV and solvolysis: Barlin & Benbow J Chem Soc, Perkin Trans 2 790 1974, Beilstein 20/5 V 405.]
