Chlorination of phosphorus compounds

High purity triphenylphosphine, as required in the Wittig ylide synthesis of al-kenes such as vitamin A, is prepared by the reaction of triphenylphosphine dichloride Ph3PCl2 with Mg, 7U, and/or Fe in the presence of an inert solvent. The Ph3PCl2 content of phosgene, chlorine, diphosgene, HCl, thionyl chloride, sulfuryl chloride, phosphorus trichloride and/or aliphatic halogen compounds (active chlorine compounds) must total less than 1000 ppm of free chlorine [1313]. 

Triphosgene reacts with Pha P according to a simple mechanism to produce exclusively PhsPCU as the sole phosphorus product [988]. 

PhaP was dissolved in dichloromethane or 1,2-dichloroethane (1 5 v/v) and a solution of triphosgene (0.33 equiv.) in the same solvent was added dropwise whilst cooling to maintain the temperature at 20 °C. After completion of the addition, the reaction mixture was stirred until gas evolution ceased. A solution of the substrate (Table 4.50), containing triethylamine where necessary, was then added (or inverse addition by means of syringe or cannula, if required). Tkfter the reaction, the products were isolated by standard techniques. 

Reaction of the chlorinated Lewis acids carbonic dichloride, phosphoryl chloride, chloroiminium chloride, and chlorine with hexamethylphosphoric triamide 

The Vilsmeier reagent prepared by treating DMF with COCI2 is a useful reagent in nudeic add chemistry, e.g. for chlorination and formylation of nucleosides, and in the synthesis of oligonucleotides [1315]. 

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