Phosphorus chloride phosgene

Amino-pyridazines and -pyridazinones react with monomethyl- or iV,A-dimethyl-formamide and other aliphatic amides in the presence of phosphorus trichloride, thionyl chloride, phosgene or benzenesuUonyl chloride to give mono- or di-alkylaminomethyl-eneamino derivatives. The same compounds can be prepared conveniently with A,iV-dimethylformamide dimethyl acetal in high yield (Scheme 50). 

The course of the reaction is similar when the chlorides of phosphorus (or phosgene) are used. 

Preparation of oxazole Cyclocondensation of amides, through dehydration, leads to the formation of corresponding oxazoles. This synthesis is known as Robinson-Gabriel synthesis. A number of acids or acid anhydrides, e.g. phosphoric acid, phosphorus oxychloride, phosgene and thionyl chloride, can bring about this dehydration. 

The Vilsmeier-Haack formylation procedure (Scheme 24) provides the most effective synthesis of formylpyrroles and indoles. Reaction of the heterocycles with the immonium cation (72), derived from DMF or (V-methylformanilide with an acid chloride, such as phosphorus oxychloride, thionyl chloride, phosgene, oxalyl chloride, benzoyl chloride or bromotriphenylphosphonium bromide, yields the intermediate heteroarylimmonium salt (73). Under suitable reaction conditions, this salt may be isolated from the reaction involving phosphorus oxychloride as an impure chlorophosphate (78TH30500) or precipitated from the reaction system as the thermally unstable perchlorate by the addition of sodium... 

In practice the dehydration can be achieved with a broad range of acids or acid anhydrides, such as phosphoric add, phosphorus oxychloride, phosgene (COCI2), and thionyl chloride. An example of the mechanism is shown below for thionyl chloride and involves activation of the amide to imidolyl halide 3.16 then intramolecular attack by the enolic form of the ketone. 

There are two general routes to arylsulfonyl chlorides. The first involves the conversion of an already sulfur-substituted aromatic compound to the sulfonyl chloride. Thus arylsulfonic acids or their alkali metal salts yield sulfonyl chlorides by treatment with a variety of chlorinating agents such as phosphorus pentachloride, thionyl chloride, phosgene, and chlorosulfonic acid. Alternatively, substituted thiophenols or aryl disulfides can be oxidized by chlorine-water to the sulfonyl chloride.6... 

The ethylidene, or unsymmetrical di-halogen substitution products of ethane, are not of much importance, because they do not easily undergo reaction. They are prepared by the reactions just described, viz., from aldehyde by the action of phosphorus penta-chloride, -bromide, or -iodide. Also by the action of phosphorus chlor-bromide, PCl3Br2, or of carbonyl chloride (phosgene), COCI2. They may also be made by the further halogenation of the mono-halogen ethanes ... 

The maiin domain of oxidation with dimethyl sulfoxide is the conver-sionofprimary alcoholsinto aldehydes andofsecondaryalcoholsintoketones. These reactions are accomplished under very mild conditions, sometimes at temperatures well below 0 °C. The reactions require the presence of acid catalysts such as acetic anhydride [713, 1008, 1009], trifluoroacetic acid [1010], trifluoroacetic anhydride [1011, 1012, 1013], trifluorometh-anesulfonic acid [1014], phosphoric acid [1015, 1016], phosphorus pentox-ide [1006, 1017], hydrobromic acid [1001], sulfur trioxide [1018], chlorine [1019, 1020], A -bromosuccinimide [997], carbonyl chloride (phosgene) [1021], and oxalyl chloride (the Swem oxidation) [1022, 1023, 1024], Dimethyl sulfoxide also converts sufficiently reactive halogen derivatives. into aldehydes or ketones [998, 999] and epoxides to a-hydroxy ketones at -78 °C [1014]. 

Practically, the above reactions are combined into one operation. The above condensation-product is treated with a chloride of phosphorus or phosgene, and the resulting chloride,... 

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]. 

Compounds of this type are usually prepared from the corresponding quinoxaline-2,3-diones. A variety of chlorinating reagents have been used, including phosphoryl chloride," phosgene," thionyl chloride, and mixtures of phosphoryl chloride with N,N-dimethylaniline or N,N-diethylaniline" " or phosphorus pentachloride." The reactions are normally carried out under reflux in an open vessel for periods of about... 

HAZARD RISK Dangerous fire hazard when exposed to heat or flame contact with strong oxidizers may cause fire vapors may flow to distant ignition sources and flash back forms explosive mixtures with powdered sodium or phosphorus trichloride and sodium violent reaction with silver perchlorate and dimethyl sulfoxide closed containers exposed to heat may explode decomposition emits toxic gases of hydrogen chloride, phosgene, carbon monoxide, carbon dioxide NFPA Code H 2 F 3 R 0. 

Acid chlorides are made from fatty acids by reaction with phosphorus trichloride, phosphorus penta-chloride, phosphorus oxychloride, phosgene, oxalyl chloride, thionyl chloride or triphenylphosphine and carbon tetrachloride. Phosphorus trichloride is probably the most economical reagent for large-scale reaction. Improved yields have been claimed when the reaction is carried out in the absence of oxygen. The most common laboratory procedures require the acid to stand at room temperature for... 

Acid chlorides are prepared by reaction of a carboxylic acid with a halogenating agent sueh as thionyl chloride, phosphorus trichloride, phosphorus pentachloride, phosgene, or oxalyl chloride. 

The following section highlights some selected recent applications of the use of phosgene equivalents in the preparation of Vilsmeier-type chlorinated derivatives of amides and ureas. Thionyl chloride, carbonyl bromides, phosphorus oxychloride, phosgene, triphosgene, oxalyl chloride, and p-toluenesulfonyl chloride are all efficient oxophilic promoters capable of generating Vilsmeier-type chloro imi-nium ion intermediate 1770 by reaction with formamides, particularly dimethyl-formaraide, and ureas. 

Phosphorus chlorides have usually been used, but phosgene and thionyl chloride are also effective . Generally, heating l-alkyl-2-pyridones with phosphorus chlorides has led to the isolation of 2-chloropyridines, but in some cases the intermediate l-alkyl-2-chloropyridinium salt has been isolated (p. 223). l-Methyl-4-pyridone also produced 4-chloro-l-methylpyri-dinium chloride which gave 4-chloropyridine and methyl chloride when heated Other examples of the conversion of 1-substituted 4-pyridones into 4-chloropyridinium quaternary salts are known 7 Examples of that of l-aryl-2-pyridones into 2-chloropyridines are rarer but exist 25 ... 

Related Reagents. Dimethylchloromethyleneammonium Chloride Hexamethylphosphoric Triamide-Thionyl Chloride Hydrogen Chloride Oxalyl Chloride Phosgene Phosphorus(III) Chloride Phosphorus(V) Chloride Phosphorus(V) Oxide Phosphorus Oxychloride Triphenylphosphine-Carbon Tetrachloride Triphenylphosphine Dichloride. 

Nitrophenyl isocyanate has been prepared by heating -nitrophenyl carbamyl chloride. The latter has been obtained by the action of phosgene on -nitroaniline in benzene-toluene solutions, and by the action of phosphorus pentachloride on methyl jii-nitrophenylcarbamate. The preparation given above is based upon recent publications of the authors. ... 

Diselenium dichloride and seleninyl chloride both explode on addition of potassium [1,3], while the metal ignites in contact with phosphorus trichloride vapour or liquid [2], Mixtures of potassium with sulfur dichloride or sulfur dibromide, phosphorus tribromide or phosphorus trichloride, and with phosgene are shock-sensitive, usually exploding violently on impact. Potassium also explodes violently on heating with disulfur dichloride, and with sulfur dichloride or seleninyl bromide without heating [3]. 

Intermediates with wide civilian uses, for example, in the production of insecticides, pharmaceuticals, paints and lacquers, coating agents and lubricants etc. (e.g. phosgene, phosphorus oxygen chloride). 

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]. 

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