Phosphorus reaction with, phosgene

Triphenylphosphine oxide from the commercial production of vitamin A by a Wittig reaction is recycled by reaction with phosgene to give the phosphine dichloride and reduction of the dichloride to triphenylphosphine with elemental phosphorus (461. Polymeric phosphine oxides have been converted to phosphine dichlorides with oxalyl chloride and then reduced to phosphine with diisobutylaluminum hydride (471. 

The reaction with disubstituted formamides and phosphorus oxychloride, called the Vilsmeier or the Vilsmeier-Haack reaction,is the most common method for the formylation of aromatic rings. However, it is applicable only to active substrates, such as amines and phenols. An intramolecular version is also known.Aromatic hydrocarbons and heterocycles can also be formylated, but only if they are much more active than benzene (e.g., azulenes, ferrocenes). Though A-phenyl-A-methyl-formamide is a common reagent, other arylalkyl amides and dialkyl amides are also used. Phosgene (COCI2) has been used in place of POCI3. The reaction has also been carried out with other amides to give ketones (actually an example of 11-14),... 

When thionophosphonic esters are used for conversion to the phosphonothiochloridates, observation of the stereospecificities of the reactions is possible. Alternative results may be attained through judicious choice of the reagent system. For example, the optically active O-isopropyl methylphosphonothioate, as shown in Equation 4.10, reacts with phosgene at sulfur only to form the O-isopropyl methylphosphonochloridate with inversion of configuration at phosphorus.20... 

Guanidines have been prepared by the reaction between an amine, or an amine salt, and a host of other reagents, such as a thiourea in the presence of lead or mercuric oxide [83, 157, 158], carbodi-imides [140, 174, 175],calcium cyanamide [176, 177], isonitrile dichlorides [178—180], chloroformamidines [181], dialkyl imidocarbonates [182], orthocarbonate esters [183], trichloro-methanesulphenyl chloride [184], and nitro- or nitroso-guanidines [185-188]. Substituted ureas can furnish guanidines, either by treatment with amines and phosphorus oxychloride [189], or by reaction with phenylisocyanate [190] or phosgene [191]. 

Condensation Reactions. Many triam inotriarylmethane dyes can be produced by condensation of Michlers ketone (9) with aromatic amines. The ketone must generally be activated with phosgene or phosphorus oxychloride, whereby a reactive blue chloro compound (10) is formed from the intermediate geminal dichloride. With V-phcnyl-1 -naphthylaminc, for example, (13) reacts to form Victoria blue B (11). 

Preparation of acid chlorides. The thionyl chloride method of preparing acid chlorides fails with some carboxylic acids (e.g., p-NOjCsHaCOzH) and with all sulfonic acids. Bosshard and co-workers" found that dimethylformamide catalyzes both reactions, either when used as solvent or when employed in catalytic amount in an inert solvent. The reactive, hygroscopic intermediate dimethylformirainium chloride was isolated from one equivalent each of dimethylformamide and thionyl chloride, and also obtained by reaction of dimethylformamide with phosgene, oxalyl chloride, or phosphorus pentachloride. It reacts with an acid with regeneration of dimethylformamide, the catalyst. In one example, 0.3 mole of p-nitrobenzoic acid was heated briefly at 90-95° with 0.315 mole of thionyl chloride and 0.03 mole... 

Davy reported that elemental arsenic and antimony both react with phosgene, upon heating, to produce their respective chlorides and carbon monoxide [467]. Phosphorus, however, can be sublimed in an atmosphere of phosgene without any reaction occurring [467]. 

Surprisingly little work has been published on the reactions of phosgene and ketones. Unlike phosphorus(V) chloride, phosgene is reported not to react with ketones to replace the carbonyl oxygen with chlorine, even at elevated temperatures [1704]. 

Haszeldine and Iserson have also speculated [899,903] that various tetrahalomethanes can be prepared from the reactions of COBrF with phosphorus(V) halides, analogous to the reaction of phosgene with PClj to give CCl and POCI3. For example ... 

The reaction of V-cyanocarboximidamide with (chloromethylene)iniinium salts provides another important route to substituted 1,3,5-triazines.394,395 The (chloromethylene)iminium salts are prepared in situ from the corresponding amides, thioamides or dithiocarbamates and phosphoryl chloride, phosphorus pentachloride or phosgene (cf. Houben-Weyl, Vol. E5,... 

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