Phosgene, reaction with diols

By application of the Corey-Winter reaction,vicinal diols 1 can be converted into olefins 3. The key step is the cleavage of cyclic thionocarbonates 2 (1,3-dioxolanyl-2-thiones) upon treatment with trivalent phosphorus compounds. The required cyclic thionocarbonate 2 can be prepared from a 1,2-diol 1 and thio-phosgene 4 in the presence of 4-dimethylaminopyridine (DMtVP) ... 

Meprobamate Meprobamate, 2-methyl-2-propyl-l,3-propandiol dicarbamate (5.2.2) is synthesized by the reaction of 2-methylvaleraldehyde with two molecules of formaldehyde and the subsequent transformation of the resulting 2-methyl-2-propylpropan-l,3-diol (5.2.1) into the dicarbamate via successive reactions with phosgene and ammonia [48-50]. 

Oleic acid was converted to the erythro diol 264 or the threo diol 258 by reaction with permanganate or hydrogenperoxide respectively. The threo compound 258 was converted to the 9,11-dioxahomoprostanoids. Reaction with paraformaldehyde formed 259 or 260, phosgene converted the diol into 261 whereas reaction with thiophosgene gave compound 262. 

A few of the polyeondensation reactions may be performed in a single liquid phase. Examples of this are the reaction of diisocyanates with diols (8) or diamines (7) and the formation of polycarbonates from bisphenols and phosgene in a solvent with pyridine as the acid acceptor 15, 22),... 

Phosgene reacts, sometimes violently, with a large number of common inorganic (Chapter 9) and organic (Chapter 10) substances. Hazardous reactions with lithium, sodium, potassium, aluminium, lithium amide, hexa-2,4-diyn-l, 6-diol, propan-2-ol, and hexafluoropropene have been mentioned specifically [1787]. Mixtures of potassium and phosgene are reported to explode when subjected to shock [1913a]. In addition, phosgene... 

Organosilicon diols possessing ether linkages combine with phosgene to give a large spectrum of products (arising both by reaction with COClj and with HCl) ... 

Polycarbonates (. Polycarbonates may be prepared by a variety of synthetic methods. Procedures most commonly used include reaction of diols with phosgene (Reaction 2A), transesterification of diesters of carbonic acid with dihydroxy compounds (Reaction 25), and polymerization of cyclic carbonates (Reaction 26). 

This class of polymers is obtained by the reaction of diols with carbonic acid derivatives and the most important polycarbonate, PC, is made from bisphenol A and phosgene. 

Toluene diisocyanate (a) is produced industrially together with its isomer 2,6-toluene diisocyanate in a three-step reaction sequence First toluene nitration is carried out and from the obtained mixture of ortho-, meta-, and para-isomers only the ortho/para mixture is retained for further nitration. The resulting 2,4- and 2,6-dini-trotoluenes are then hydrogenated using nickel or palladium catalysts to the corresponding aromatic diamines. The latter are converted with phosgene into the technical TDI mixture, which is almost exclusively applied in combination with diols and triols to form polyurethane foam materials. 

Diisocyanates are commonly used with either diols or a mixture of diols and polyols. When diols are exclusively used and the trimerization reaction is minimized, the polyurethane is substantially linear, but it becomes increasingly three-dimensional with increasing levels of polyol or with trimerization of the diisocyanate. The trimerization reaction and the use of polyols enable thermoset polyurethanes. Common diisocyanates include toluene diisocyanate (TDl), methylene diphenyl diisocyanate (MDl), naphthalene diisocyanate (NDl), and hexamethylene diisocyanate (HDl). TDI is prepared by the nitration of toluene to give a mixture of mainly 2,4- and 2,6-dinitrotoluene, followed by reduction and reaction with phosgene. The isomers are typically not separated and are used as a mixture. 

Polycarbonates are polyesters of carbonic acid formed by reaction of diols (aromatic, aliphatic or a mixture of both) with a derivative of carbonic acid. The first preparations of polycarbonates were reported by Einhorn in 1898 [155], by reaction of phosgene with resorcinol or hydroquinone in a pyridine solution. Bischoff and van Hedenstrom in 1902 [156] obtained the same aromatic polycarbonates via transesterification with diphenyl carbonate (DPC). Thus the main routes to polycarbonates were established early, but the properties of the products seemed uninteresting. Around 1930 aliphatic polycarbonates were studied by Carothers and van Natta [157]. These carbonates have low melting points and thermal resistance and are not commercially interesting as stand-alone thermoplastics. Low molecular... 

Although a polymeric carbonate could be produced in the reaction of a diol with phosgene, these products are usually obtained by a transesterification reaction with a dialkyl (or diaryl) carbonate. The reaction of diethyl carbon with a phenol called bisphenol A gives a polycarbonate known as Lexan. 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

When a diisocyanate reacts with a diol, a linear polyurethane is generated, and when it reacts with a polyol, it generates a cross-linked polymer. The isocyanates are commonly prepared by the reaction of phosgene and primary amines as follows ... 

There is thus considerable scope for further examination of the reactions of phosgene with a wide variety of alcohols, diols, aldehydes, hydroxy-aldehydes, epoxides, esters, acids and anhydrides to produce the desired range of chlorinated organic materials. The analogous reactions of COFj and of COCIF will be described in Chapters 13 and 16, respectively. 

The gas phase reaction of phosgene with ethane-1,2-diol over activated charcoal results in the formation of 1,2-dichloroethane with a yield of about 70% at 210 C higher temperatures caused the decomposition of the diol [1C186]. 

Reaction of ethane-1,2-diol with phosgene in the liquid phase gives the... 

Because of the ease with which this cyclization reaction occurs, phosgene has been used as a reagent for the enantiomeric resolution of 1,2- and 1,3-diols [1151,1152] ... 

Reaction of the following fused-ring cis-diol with phosgene gives a bridged carbonate... 

Probably the simplest polymer formation reaction involving phosgene is that with the dihydric aliphatic alcohols, such as ethylene, propylene or butylene glycol viz. ethane-1,2-diol, propane-1,3-diol or butane-1,4-diol) this reaction results in the formation of linear, wax-like polymers suitable for the impregnation of materials requiring water barrier properties [1133]. 

The reaction of phosgene with vic-diols (including sugars) leads to cyclic carbonates (Kawabata et al., 1986). 

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