Patent ID: 7560445
Filing Date: 2009-07-14
Classification: A01N,A61P,C07F

Abstract:
1. A process for preparing malathion for a topical pharmaceutical composition comprising the steps of: (a) preparing a solution of O,O-dimethyldithiophosphoric acid in an organic solvent selected from the group consisting of toluene, xylene and benzene; (b) extracting the O,O-dimethyldithiophosphoric acid into water to generate an aqueous solution of O,O-dimethyldithiophosphoric acid; (c) reacting the aqueous solution of O,O-dimethyldithiophosphoric acid with diethyl maleate to form malathion; and, (d) treating the malathion from step (c) with a sulfur reagent, wherein the sulfur reagent has a pH less than about 7.0; wherein the malathion comprises greater than about 98.5% (w/w) malathion, less than about 0.1% (w/w) MeOOSPO, less than about 0.1% (w/w) MeOSSPO, less than about 0.2% (w/w) MeOOSPS, less than about 0.3% (w/w) malathion carboxylic acid, less than 0.1% (w/w) methyl malathion, less than about 0.1% (w/w) malaoxon, and less than about 0.1% (w/w) isomalathion.