Patent ID: 6717007
Filing Date: 2004-04-06
Classification: C07F

Abstract:
An improved regiospecific process for preparing phosphonous acids of formula (I), conforming to anti-Markonikoff addition, where R1 is straight or branched alkyl of 1 to 10 carbon atoms; alkyl substituted with halogen, trifluoromethyl, hydroxy, alkoxy, carboxy and amino groups; cycloalkyl of 3 to 7 carbon atoms; phenyl substituted with halogen, trifluoromethyl, hydroxy, amino, alkyl and alkyl substituted by halogen, trifluoromethyl, hydroxy, alkoxy, carboxy and amino groups; carboxylic acid or carboxylic acid ester; cyano; aldehyde; and a substituted five or six membered heterocyclic ring system, wherein the heteroatom is nitrogen, oxygen or sulfur and the substituent is an alkyl or carboxylic acid group; wherein the process comprises reacting an olefin of formula (II),R1â€”CH&boxH;CH2â€ƒâ€ƒ(II) wherein R1 is as defined above, with hypophosphorous acid in presence of a water-miscible organic solvent and an inorganic persulfate of formula (III),M2S2O8â€ƒâ€ƒ(III) wherein M is ammonium, sodium or potassium, at a temperature in the range of 60Â° C. to 80Â° C. for 15-60 minutes at atmospheric pressure at a pH within the range of from 4.5 to 7.0, and recovering the said phosphonous acid formed from the reaction mixture.