Benzene reaction with, phosgene

This reaction is typical for the synthesis of sulfonylureas it is mildly exothermic and proceeds smoothly in a variety of inert aprotic solvents. The product is usually obtained in very high yield, as a fine crystalline precipitate. The sulfonyl isocyanates are readily prepared from the substituted benzene sulfonamides by reaction with phosgene, Fig. 3, in the presence of an alkyl isocyanate, for example, butyl isocyanate in an inert solvent at 120 to 140°C according to the general procedure of H. Ulrich and A. A. R. Sayigh (Ref. 3). 

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),... 

This procedure is a modification of preparations of 3-phen)d, sydnone described earlier. The dehydration of N-nitroso-N phenylglycine has also been effected by the use of thionyl chloride and pyridine in dioxane, thionyl chloride in ethertrifluoroacetic anhydride in etherand diisopropylcarbodiimide in water or by reaction of the alkali metal salts of N-nitroso-N-phenylglycine with phosgene or benzenesulfonyl chloride in water or with acetyl chloride in benzene. ... 

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. 

In this method, an ale soln of benzene-sulfonic acid(previously standardized with phosgene by weighing the pptd diphenyl-carbamide) is added from a burette to a sample of aniline(or its nitrated compd not jiighvr thsji tctrsnitro-) until the 3ppcufuptcc of a dirty-bluish coloration, when a drop of the reaction mist is placed on a filter paper previously impregnated with amino-/3-naphthol indicator(spot test). This method is not applicable for analysis of penta-nitroani ine(Ref 15)... 

The kinetics and mechanism of the reaction of carboxylic acids with phosgene COCI2 in DMF in benzene were zero-order in substrate and proceeded via rapid formation of... 

Phenoxazine is easily acylated with acetic anhydride or on heating with acyl chlorides in benzene.12-71,75 A very convenient method is the reaction of phenoxazine with phosgene to give phenoxazine-10-carbonyl chloride (37).73- 76 This acyl chloride is very stable it is not decomposed by short boiling in water or methanol, and gives phenoxazine only with hot sodium hydroxide. On prolonged boiling... 

CONSENSUS REPORTS lARC Cancer Review Animal Sufficient Evidence IMEMDT 5,47,74 IMEMDT 20,195,79. SAFETY PROFILE Confirmed carcinogen with experimental tumorigenic and neoplastigenic data. Poison by inhalation and ingestion. Human systemic effects by an unspecified route convulsions. Potentially dangerous reaction with DMF in presence of Fe, also CCU. When heated to decomposition it emits highly toxic fumes of cr, HCl, and phosgene. See also BENZENE HEXACHLORIDE and other benzenehexachloride entries. 

The reaction between ethyne and phosgene has also been studied under photochemical conditions (>220 nm) [2185a]. As in the analogous reaction with ethene (see Section 10.1.2), the phosgene merely acts as a convenient source of chlorine radicals the principal products were CO, CHj=CHCl, 1-chloro-l, 3-butadiene, benzene and polymer trace amounts of HC Cl and CgHjCl were also detected [2185a]. 

Upon protracted contact with aluminium(III) chloride at higher temperatures, and especially if the aromatic hydrocarbon is itself used as the solvent, the product of the reaction between phosgene and aromatic hydrocarbons is usually the corresponding benzophenone [2026]. Friedel and Crafts [686aa] found that COCI, reacts with benzene in the presence of a stoicheiometric amount of aluminium(III) chloride to give benzophenone ... 

Cyclizations can occur when two amino groups are adjacent on a benzene ring. For example, reaction of phosgene with 2,3-diaminotoluene in chlorobenzene gave a precipitate containing a five-membered ring, considered to be a cyclic urea [1154] ... 

Interestingly, the chloroformate (diphosgene) and the carbonate (triphosgene) react with pyridine to give the same product (see also Chapter 12). The material described as (py)j. jCOClj, prepared from the reaction of phosgene with pyridine in benzene solution, was noted to lose half a molar equivalent of pyridine upon standing over PjOj in vacuo [1809a]. 

These reactions may be catalysed by amides, such as HC(0)NMej (R = Et, Pr, MCjCH, Me(CHj)3, MCjC, Me(CH2) Ar = Ph) [2036], activated carbon (R = Et) [27], or NEtj [1406a]. EtSC(0)Cl has been prepared by treating a benzene soiution of EtSH with phosgene in the presence of a 20 % aqueous soiution of NaOH [1785]. As with... 

Reaction of thioureas with phosgene is usually performed at room temperature in an inert solvent (such as benzene, chlorobenzene or 1,2-dichloroethane) in which the thiourea is soluble. By-products, if formed, are readily separated with ethoxyethane in which the chloroformamidinium chloride salts are insoluble. 

Cyclopropanols can be converted to various cyclopropyloxy derivatives (esters, e.g. acetates, ethers, e.g. methyl and ethyl ethers, and acetals, e.g. tetrahydropyran-2-yloxy derivatives) under the appropriate reaction conditions. In most cases the synthesis of cyclopropyl esters by the reaction between a cyclopropanol and an acid chloride (e.g. formation of 1 ) or acetic anhydride (e.g. formation of 2 ) have been reported. The yields were particularly good (84-95%) when acetic anhydride was used, although a drawback of the reaction can be byproduct formation. When a reactive moiety is attached to the cyclopropane ring in addition to the hydroxy group, other reactions can also occur m-l-(aminomethyl)-2,2-dimethyl-3-(2-methylprop-l-enyl)cyclopropanol (3) reacted with phosgene in benzene to give the corresponding carbamate l,l-dimethyl-2-(2-methylprop-l-enyl)-4-oxa-6-azaspiro[2.4]heptan-5-one (4) in 31% yield. ... 

Wilson, R.E. and Fuller, E.W. 1922. The reactions of phosgene with benzene and m-xylene in the presence of aluminum chloride. Journal of Industrial Engineering Chemistry, 14 406 109. 

The reagent is prepared by reaction of /3,/3,/1-tribromoethanol with phosgene in benzene. It reacts with primary and secondary hydroxyl groups of nucleosides to give /3,/8,/8-tribromoethoxycarbonyl compounds (I). The protective gronp is removed by /3-elimination with a zinc-copper couple.1... 

Cyclization of a 2-oximinoazine with phosgene may occur either by reaction in pyridine at OX, or by passing phosgene into a boiling solution of the substrate (. 4) in benzene. 

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. 

Thienylthioethanols were obtained in high yields by the reaction of thiophen-2-thiols with ethylene oxide.The reaction of 2,4-dinitro-3-bromothiophen with sodium dimethylthiocarbamate or sodium t-butyl-trithiocarbonate yielded (142). Decomposition of (142b) in glacial acetic acid led to a mixture of (143) and (144) in moderate yield. The reaction of thiophen-3,4-dithiol with phosgene chloride, followed by nitration, gave (145). The reaction of thiophen-2-thiol with p-(methylsulphonyl)bromo-benzene was used for the preparation of 2-thienyl p-(methylsulphonyl)phenyl sulphide. 

The anhydrides 186 react with primary amines in alcohol and form compounds 187. The reaction of the latter with phosgene in pyridine (80°C) [104], in boiling benzene [109, 110], or in toluene (90°C) [111] leads to cyclization with the formation of 2,4-quinazolinedione derivatives 188 [104, 109-111],... 

Tetramethylurea has been used as a catalyst in the reaction of phosgene with barbituric acid and when 1,3-dimethylbarbituric acid was allowed to react with phosgene in benzene under reflux in the presence of tetramethylurea, l,3,7,9,-tetramethyl-2,4,5,6,8-pentaoxopyrano[2,3-d 6,5-d ]dipyrimidine (XLVI) was obtained in 48 per cent yield [32],... 

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