Vinylphosphonic dichloride

PCI 5 (followed by SOa) converts ethyl thioethers into alkylthiovinylphosphonic dichlorides (42)36 and acetals into alkoxy(aryloxy)vinylphosphonic dichlorides... 

Early reports on the addition of chlorine or bromine to diethyl vinylphosphonate (133 R = EtO) and to vinylphosphonic dichloride (133 R = Cl) " suggest a lack of predictability even in such simple cases. The addition of bromine in chloroform to 133 (R = EtO) leads to 134 with smaller amounts of 135 chlorination of the same ester in CCI4 also leads to a mixture of the two types, in this case in roughly equal amounts. On the other hand, the bromination of vinylphosphonic dichloride yields (l,2-dibromoethyl)phospho-nic dichloride (135 R = Cl, X = Br), which is sufficiently stable to allow hydrolysis to (1,2-dibromoethyl)phosphonic acid. The ready loss of HBr followed the addition of 2 mol of bromine to phenyl(4-phenylbuta-1,3-dienyl)phosphinic acid the product consisted almost exclusively of Ph(PhC4H3Br3)P02tf... 

Another strategy concerns the esterification of the vinylphosphonic dichloride monomer (Scheme 3.1b) in the presence of hydrojgrl compounds, catalyzed by primary amines. This reaction usually proceeds quantitatively, but requires the prior synthesis of the vinylphosphonic dichloride monomer. Alternative methods have also been developed to obtain the diallg l vinylphosphonate monomers, but are based on multiple-step reactions. 

The synthesis and characterization of VPA was previously described by Kabachnik and Medvedev. They used vinylphosphonic dichloride as the starting reagent, which was prepared by catalytic dehydrochlorination of the already known 2-chloroethylphosphonic dichloride (Scheme 4.1) by passing its vapor through a quartz tube filled with barium chloride at high temperature. ... 

VPA was obtained as a viscous liquid by hydrolysis of vinylphosphonic dichloride in cool water, distillation of water and hydrochloric acid, and drying under vacuum (Scheme 4.2). 

Scheme 4.7 Vinylphosphonic dichloride obtained from its diesters.

VPA can also be obtained by hydrolysis of vinylphosphonic dichloride in the presence of dichloromethane, at low temperature. The resulting hydrogen chloride and dichloromethane are removed by vacuum distillation. It was found that the reaction of VPA esters with phosphorus pen-tachloride at higher temperature leads to the formation of vinylphosphonic dichloride (Scheme 4.7). 

In this reaction, VPA esters can be used with short-chain aliphatic alcohols. The vinylphosphonic dichloride can be obtained from the reaction mixture in a pure state by distillation under reduced pressure. The use of metal halides as catalysts leads to vinylphosphonic dichloride in higher yield. It is advantageous to use iron(III) chloride as catalyst because the residue can be removed easily from the reaction vessel. 

Other possibilities to obtain VPA are by hydrolysis of vinylphosphonic dichloride or from phosphorus trichloride, ethylene oxide, and thionyl chloride, following five steps. An economical method consists in the heating of 2-acet03grethylphosphonic acid diallqrl esters (allgrl = methyl, ethyl) at a temperature around 200 °C, in the presenee of an aeidie or basic catalyst when a teehnieal grade crude VPA or ester eontaining crude VPA is obtained. 

Fluoroalkanephosphonic acid can be obtained by addition of iodine perfluoroalkane to vinylphosphonic acid dichloride followed by saponification and deiodination by sodium amalgam [141]. Fluoroalkanephosphonic acids can be transformed to fluoroalkanephosphonic acid glycil esters by 2 mol of epi-chlorhydrin in a water-free solution followed by reaction with alkalines or amines [142]. Compounds of this kind with an alkyl chain of 8-20 carbon at-... 

Reactions of Vinylthiophens and Related Compounds. - 2-Aroyl-5-vinyl-thiophens react with triphenylphosphine, palladium chloride, and carbon monoxide to give 2-(5-aroyl-2-thienyl)propionic acid. Cycloaddition of sulphene, from methanesulphonyl chloride and triethylamine, to 2-(a-dimethylaminovinyl)thiophen gave (160). The synthesis of some substituted 3-(2-thienyl)acryloylamino-acids has been described. Some reactions of 3-chloro-j8-(2-thienyl)vinylphosphonic acid dichlorides have been studied, ... 

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