Aromatic amines reaction with, phosgene

Ketone formation can also be avoided if one of the functional acyl halogens ia phosgene is blocked. Carbamyl chlorides, readily obtained by the reaction of phosgene with ammonia or amines, are suitable reagents for the preparation of amides ia direct Friedel-Crafts acylation of aromatics. The resulting amides can be hydroly2ed to the corresponding acids (134) ... 

Aromatic Isocyanates. A variety of methods are described in the Hterature for the synthesis of aromatic isocyanates. Only the phosgenation of amines or amine salts is used on a commercial scale (5). Much process refinement has occurred to minimise the formation of disubstituted ureas arising by the reaction of the generated isocyanate with the amine starting material. A listing of the key commercially available isocyanates is presented in Table 1. 

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. 

V-Phenylsuccinimide [83-25-0] (succanil) is obtained in essentially quantitative yield by heating equivalent amounts of succinic acid and aniline at 140—150°C (25). The reaction of a primary aromatic amine with phosgene leads to formation of an arylcarbamoyl chloride, that when heated loses hydrogen chloride to form an isocyanate. Commercially important isocyanates are obtained from aromatic primary diamines. 

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),... 

The two key isocyanates that are used in the greatest volumes for polyurethane polymers are toluene diisocyanate (TDl) and methylene diphenyl diisocyanate (MDl). Both isocyanates are produced first by nitration of aromatics (toluene and benzene, respectively), followed by hydrogenation of the nitro aromatics to provide aromatic amines. In the case of MDl, the aniline intermediate is then condensed with formaldehyde to produce methylene dianiline (MDA), which is a mixture of monomeric MDA and an oligomeric form that is typical of aniline/formaldehyde condensation products [2]. The subsequent reaction of phosgene with the aromatic amines provides the isocyanate products. Isocyanates can also be prepared by the reaction of aromatic amines with dimethylcarbonate [3, 4]. This technology has been tested at the industrial pilot scale, but is not believed to be practiced commercially at this time. 

Isocyanates are produeed almost exclusively by the reaction of amines with phosgene (COCy, with the speeifie reaetion eonditions varying particularly for aromatic and aliphatic isocyanates (Chadwick and Cleveland 1981 Codd et al. 1972 Ulrich 1989). Aliphatic diisocyanates are produced by reaction of phosgene with either a slurry of the carbamate salts obtained in the reaction of the aliphatic diamines with earbon dioxide, or with a slimy of the amine hydrochloride (Ulrich 1989). Hexamethylene diisocyanate (HDI) is produeed by the reaction of phosgene with the amine salt (Chadwick and Cleveland 1981). The trimerie HDI biuret (HDI-BT), which has a low monomer content and is widely used in the formulation of exeeptionally high quality polymer coatings, is produced by controlled reaction of HDI with water, a water generator, or an amine (Chadwick and Cleveland 1981). 

The first methanes involved the reaction of isocyanate with simple alcohols and amines. They were of sufficient economic value to foster the development of a number of isocyanates, including the aromatics that play dominant roles in modem polyurethanes. An isocyanate is made by reacting an amine with phosgene. 

Long-chain alkyl chlorides can be used lor the synthesis of various amines, while benzyl chloride is used for production of quaternary ammonium compounds. Alkyl chlorides are used for the formation of organometallics, including the Grignard reagents as well as for alkylation of aromatics. One of the important reactions or phosgene is with diamines for production of diisocyunates (polyurethanes). 

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). 

If methyleneindoline-o)-aldehydes are condensed with cyclic amines substituted by an amino group in the aromatic ring, dyes are obtained that can be dimerized either by reaction with cyanuric chloride in a molar ratio of 2 1 or with phosgene. On account of their high substantivity these dyes are suitable for dyeing bleached sulfite pulp [22],... 

When (253) reacts with phosgene the 1-acyl chloride product (254) can react with amines to give amides (79LA1756X while in a further transfer reaction with ketones the compounds (255) and (256) are produced (Scheme 146) (80H(14)97). Acylation of aromatic hydrocarbons using 1-acylimidazoles in the presence of trifluoracetic acid gives high yields provided that the aryl compounds are electron rich, e.g. p-dimethoxybenzene, thiophene, anisole <80BCJ1638). 

The reaction of phosgene with a primary aliphatic or aromatic amine Equation (10.1) is generally rapid, and takes place initially according to a 1 1 stoicheiometry, even at temperatures as low as -15 C [1861] ... 

Kinetic measurements on reactions of an excess of phosgene with primary aromatic amines were carried out in toluene at -S, +5 and +25 C [436]. The results are summarized in Table 10.1, and the mechanism of the bimolecular nucleophilic substitution reaction is ... 

SECOND ORDER RATE CONSTANTS, ACTIVATION ENTHALPIES AND ACTIVATION ENTROPIES FOR THE REACTIONS OF PHOSGENE WITH SOME PRIMARY AROMATIC AMINES [436]... 

Full processes for the preparation of aromatic isocyanates by DMC were also patented. In particular recently it was published a patent which claims an integrated process for the production of aromatic isocyanates without phosgene. In the examples the various phases of the process are repotted, starting form the reaction of the amine (TDA) with DMC to carbamate with zinc acetate dihydrate as catalyst, following a passivation treatment of the urethane catalytic residues and then pyrolysis of urethane in gas phase. 

Reactions with nucleophiles other than alcohols can produce other carbonic acid derivatives. For example, reaction with anhydrous ammonia yields urea, 0 = C(NH2)2. Aromatic primary amines can, depending on reaction conditions, react with phosgene to form carbamoyl chlorides (Csuros et al., 1969). 

A resin with mixed carbonic-carboxylic anhydride function has been prepared and used as acylating reagent [144], Thus, the supported chloroformate 140 was obtained by reaction of hydroxymethylated polystyrene with phosgene in benzene (Scheme 7.43). Further treatment with benzoic acid in the presence of triethyl-amine in benzene gave rise to the supported mixed anhydride 141. This polymer has been used in the benzoylation of several amines, although variable amounts of benzoic acid from attack to the internal carbonyl were obtained when using aromatic amines. 

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