| 摘要 |
PURPOSE:To carry out the optical resolution of 2-(4-bromophenyl)-3-methylbutanoic acid, by preparing a supersaturated solution of the diethylamine salt of said acid, preferentially crystallizing the optically active diethylamine (2:1) salt of the acid from the solution, separating the crystal from the liquid, and decomposing the separated crystal. CONSTITUTION:(+ or -)-2-(4-bromophenyl)-3-methylbutanoic acid (abbreviated as BPA) or BPA containing one of the optically active isomers in excess, is dissolved together with about 0.5-1.0mol ratio of diethylamine salt of the acid in a liquid diluent under heating to obtain a supersaturated solution. The solution is added with a seed crystal comprising a crystal of a salt preferably composed of 2mol of (+) or (-)-2-(4-bromophenyl)-3-methylbutanoic acid and 1mol of diethylamine to preferentially crystallize the salt composed of 2mol of the above (+) or (-) acid and 1mol of diethylamine. The crystallized salt is separated, and decomposed under acidic condition to obtain an optically active acid. USE:An acid component of synthetic pyrethroid ester.
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