Ammonium Type

Use of cationic 4-borono-1-methylpyridinium iodide catalyst (Fig. 1) as a dehydrative condensation agent gives amides from an equimolar mixture of carboxylic acids and amines. This catalyst also enables dehydrative condensation of amides in biphasic solution of a low-polar solvent such as toluene or ionic solution. After completion of the reaction, amide can be extracted with diethyl ether and the catalyst can be recovered and recycled repeatedly as an ionic solution. Esterification of α-hydroxycarboxylic acids also progresses in alcohol solvent at a high yield with high yield.