Process for preparing phosphonous acids.

摘要

A process is provided for preparing phosphonous acids of the structure wherein R1 is lower alkyl or arylalkyl <CHEM> which are useful in preparing phosphinic and phosphonic acid ACE inhibitors, which process includes the steps of treating an olefin of the structure R1-CH=CH2 wherein R2is lower alkyl or arylalkyl with a phosphorus-containing reagent such as sodium hypophosphite or hypophosphorous acid in the presence of an organic alcohol solvent such as ethanol or methanol, and a radical initiator such as azobisisobutyronitrile, under acidic conditions, preferably at the reflux temperature of the organic solvent, to form the phosphonous acid without forming the alkyl ester.