| 摘要 |
<p>1302690 Preparing cia-1-propenyl phosphonic acid and intermediates therefor MERCK & CO Inc 21 Dec 1970 [29 Dec 1969] 60639/70 Heading C2P Propadienyl phosphonic dichloride (II) is obtained by reacting propargyl alcohol with an excess of PCl 3 in the absence of an acid acceptor at 60-110‹ C. to form 2-propynyl phosphorodichloridite (I) and heating the latter to rearrange it. A solvent may be present but if a large excess of phosphorus trichloride is used, e.g. by using 10 to 30 moles PCl 3 per mole of the propargyl alcohol, the excess PCl 3 serves as solvent. The process is preferably conducted in an inert atmosphere, e.g. of nitrogen and HCl gas formed in the first step may be removed by distillation as it is formed. The process may be carried out continuously rather than step-wise, this being suitably effected by adding the reactants, e.g. in a PCl 3 to propargyl alcohol molar ratio of 3 : 1 to 10 : 1 to an inert solvent such as benzene, toluene, xylene, or cyclohexane, e.g. at 85-110‹ C. In this case, the formation of the dichlorophosphite intermediate (I) and its rearrangement occur simultaneously and the propadienyl phosphonic dichloride product is continuously removed from the reaction mixture as it is formed. The dichloride product (II) may be hydrogenated, preferably catalytically, to form cis-1-propenyl phosphonic dichloride (III), the preferred catalyst being palladium or Raney nickel on a support such as active carbon, barium sulphate or calcium carbonate. The hydrogenation is generally stopped when one mole of hydrogen has been taken up per mole of the dichloride (II). The dichloride (III) may then be hydrolysed with water to form cis- 1 - propenyl phosphonic acid (IV). The dichloride (II) may alternatively be hydrolysed to form propadienyl phosphonic acid (V) and the latter then selectively reduced to form (IV). The latter (selective reduction) step is suitably effected in a basic aqueous solution when 1-propynyl phosphonic acid dibasic salt (e.g. the disodium salt) is first formed by isomerization of (V) in the presence of excess base and is catalytically hydrogenated then in the solution, after initial dilution with water, to form the corresponding salt of (IV) which is then converted to the free acid (IV) by ion exchange. The cis-1-propenyl phosphonic acid is useful in making (Œ) and (- )(cis-1,2-epoxy propyl) phosphonic acid and salts and esters thereof which have antibacterial activity.</p> |
