GB1237232A - Production of cis-1,2-propenylphosphonic acid - Google Patents

Abstract

1,237,232. cis-1,2-propenyl phosphonic acid and intermediates therefor. MERCK & CO. Inc. 24 Oct., 1968 [15 May, 1968], No. 50628/68. Heading C2C. cis-1,2-Propenylphosphonic acid (I) is obtained by reacting phosphorus trichloride with at least two equivalents of a C 1 -C 5 alkyl, or C 2 -C 5 alkenyl alcohol or an alkalkyl alcohol, or a phenol, or with at least one equivalent of a dihydric phenol, e.g. catechol or of a C 2 -C 5 alkylene glycol in an inert organic solvent, reacting the resulting diorgano phosphorochloridite (II) with propargyl alcohol to form a 2- propynyl di-organo-phosphite (III), rearranging the latter to form the corresponding allenyl phosphonic acid diester (IV), hydrogenating the latter to form the cis-1,2-propenyl phosphonic acid diester (V) and cleaving the latter to form the free cis-1,2-propenyl phosphonic acid (I), the process being generally carried out without isolating the intermediate compounds. The 2-propynyl diorganophosphite (III) gradually rearranges on standing to form (IV) but the rearrangement is preferably effected by heating the mixture at 50-100‹ C. or to reflux, the heating being preferably carried out in an inert atmosphere, e.g. of N 2 or helium. The diester (IV) is then hydrogenated, preferably catalytically, in order to form the diester (V). Suitable hydrogenation catalysts are Pd/C, Pd/CaCO 3 and Raney nickel. The free olefinic acid (I) may be obtained from the cis-olefinic diester (V) by acid or base-acid hydrolysis or where appropriate by pyrolysis in the absence of a solvent. Where, however, the ester group in (IV) is aralkyl or substituted aralkyl, e.g. benzyl or chlorobenzyl, the hydrogenation step additionally serves to remove the ester groups thus yielding (I) directly. When acid is used in the ester cleavage of (V) to (I) the acid may be (I) itself or may be a strong mineral acid or an organic acid, e.g. benzene sulphonic acid or p-toluene sulphonic acid. Acidic ion exchange resins and catalytically acidic surfaces, e.g. sea sand, silica gel or acid washed alumina may also be used. When pyrolysis is used to cleave the ester it is suitably effected at 85-200‹ C. in the presence or absence of an acid catalyst. The reaction in the first two steps may be carried out in the presence of an acid-binding agent, e.g. a tertiary amine, or an oxide such as propylene oxide. In a modification of the process the allenylphosphonic acid diester (IV) is rearranged to form an α,#-propynylphosphonic acid diester and the latter hydrogenated to produce the cisolefinic diester (V) which is then cleaved. The cis-propenyl phosphonic acid product may be converted to the antimicrobial agent (Œ) (cis- 1,2-epoxypropyl)-phosphonic acid by oxidation with H 2 O 2 either directly or by first converting to the monobenzylamine salt prior to the oxidation. The invention also includes per se the compound di-t-butylallenyl phosphonate obtained as an intermediate in the third step of the process using the appropriate reactants.