Patent ID: 6852858

Claim:
A process for purifying zaleplon comprising the steps of: (a) forming a solution of a solid comprising zaleplon and a regioisomer of zaleplon at elevated temperature in a solvent selected from the group consisting of: (1) an organic solvent selected from the group consisting of ethanol, methyl ethyl ketone, methyl isobutyl ketone, diethyl ether, methyl t-butyl ether, propionic acid, ethyl acetate, isobutyl acetate, acrylonitrile, benzene, toluene, xylenes, dichloromethane, chloroform and mixtures thereof, and (2) mixtures of said organic solvent and water, (b) cooling the solution to induce precipitation of a solid enriched in zaleplon and depleted of the regioisomer relative to the solid comprising zaleplon used to from the solution, and (c) isolating the precipitated solid that is enriched in zaleplon and depleted of the regioisomer, wherein the separated precipitate is zaleplon crystalline Form IV.