Halides phosphorus, reaction

These compounds generally exist in carbonyl forms. The oxygen function can be converted into halogen by phosphorus halides. Reactions with electrophiles are quite complex. Thus urazole (511) reacts with diazomethane quickly to yield (512), which is more slowly converted into (513). 1-Phenylurazole gives (514) however, 4-phenylurazole yields (515). Oxadiazolinones of type (516) can be alkylated at both O- and N-atoms. 

Amine-phosphorus halide reactions involve hydrogen halide (or amine hydrohalide) formation. They can be complicated through acid catalysis or side reactions. Thus, the possible formation of skeletally stabilized products through transamination reactions in which no hydrohalide products are obtained is of interest. 

When carried out in the presence of a phosphorus halide, reactions of aldehydes with phosphites provide high yields of substances which appear to derive from reaction of intermediate 25 with the phosphorus halide (57). 

I. Reactions with Miscbli.aneous Inorganic Compounds 1. Phosphorus Halides... 

Reaction between phosphorus halides and Grignard reagents... 

Arbusov reaction of thienyl halides with phosphites in the presence of nickel catalyst [41, 42], or palladium catalyzed phosphorylation of thienyl halides [43], and some of them are commercially available (Scheme 22). 2,5-Diphosphorylthiophenes were synthesized by Arbusov reaction of thienyl halides with phosphites in the presence of nickel catalyst [44] or reaction of 2,5-dilithiothiophene with phosphorus halides followed by oxidation [45] (Scheme 23). 

When the phosphorus halide is PI3, this reaction is a convenient way to produce HI. Arsenic trihalides hydrolyze in an analogous way but the trihalides of antimony and bismuth react to produce oxyhalides. 

Preparation of diethyl 3-diphenylthiophosphoryl-2-morpholino-l-cyclohexenylphosphonous acid — Reaction of an enamine with a phosphorus halide and subsequent esterification... 

Preparation of bis(4-methoxyphenyl)phenylphosphine oxide — Reaction of a Grignard reagent with a phosphorus halide... 

Reaction of a phosphorus halide with a 2-alkynol and subsequent rearrangement to generate a hydroxyphosphonate... 

Both of these types of organometallics have the disadvantages of difficulties in preparation and extreme toxicity. Their major advantage is that they provide a controlled reaction, allowing a single halogen of the phosphorus halide to be displaced, leaving the others untouched. 

The reaction is performed most simply by the addition of the propargylic alcohol to a solution of the phosphorus halide. Rearrangement of the phosphorus ester proceeds at ambient temperature or with mild heating. When phosphorus trihalides are used, the product can be isolated as the phosphonic dichloride.168169 Aqueous workup provides the phosphonic acid.162 In most instances, however, a dialkyl phosphorochloridite with only a single halogen on phosphorus available for reaction with alcohol has been used.165 170 174... 

Reaction of an enamine with a phosphorus halide and subsequent esterification72... 

The second reaction proceeds much more energetically than the first, especially if preformed phosphorus halide is used. This is, however, not always necessary, at least not in the case of replacements by bromine and iodine in many cases the procedure is rather to produce the halide only during the reaction, either by dropping bromine from a separating funnel into a mixture of alcohol and red phosphorus or, as above, by adding finely powdered iodine. Like the former, this reaction can also be applied to polyhydric and to substituted alcohols indeed, it is possible to replace all the OH groups by halogens, and in particular also by chlorine. 

A commonly used and important reaction of sulfonic acids, or sulfonates, is their conversion to sulfonyl chlorides by treatment with phosphorus halides, or sometimes with thionyl chloride. Although it is easy to postulate mechanisms for this conversion, the exact path followed has never been determined. Similarly, although mechanisms can be suggested for other known reactions involving sulfonic acids, such as the cleavage of dialkyl ethers by anhydrous sulfonic acids (Klamann and Weyerstahl, 1965), or the formation of sulfones by treatment of an aromatic hydrocarbon with a mixture of sulfonic acid plus polyphosphoric acid (Graybill, 1967), nothing truly definitive is known about the details of the actual mechanisms of these reactions. 

The mechanism for the reactions with phosphorus halides can be illustrated using phosphorus tribromide. Initial reaction between the alcohol and phosphorus tribromide leads to a trialkyl phosphite ester by successive displacements of bromide. The reaction stops at this stage if it is run in the presence of an amine which neutralizes the hydrogen bromide that is formed.9 If the hydrogen bromide is not neutralized the phosphite ester is protonated and each alkyl group is successively converted to the halide by nucleophilic substitution by bromide ion. The driving force for cleavage of the C—O bond is the... 

The action of phosphorus halides on pyrrolinones and related compounds offers an alternative route to chloropyrroles. Yields of around 60% of 2,5-dichloropyrroles were obtained in this way from N-substituted succinimides (82ZC126). Vilsmeier reaction of N-alkylsuccinimidals formed chlorinated pyrrole aldehydes in modest yields (90CJC791), and there are other examples [66YZ158 81H(15)547]. A useful synthesis of chloropyrrole-2-carboxylates employed the action of phosphorus pentachloride on pyrrolidin-2-one-5-carboxylates (40) (87CB45) (Scheme 15), and in a Pummerer-type reaction pyrrol-3-yl sulfoxides were transformed by thionyl chloride into chloropyrroles. Yields were increased to >80% by the use of oxalyl chloride (88JOC2634) (Scheme 15). 

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