Dimethyl carbonate amines

CycHc carbonates are made by treating 1,2-diols with dialkyl carbonates using an alkyl ammonium and tertiary amine catalyst. The combination of propylene glycol and dimethyl carbonate has been reported to result in a 98% yield of propylene carbonate (21). 

Both dimethyl carbonate [616-38-6] and diphenyl carbonate [102-09-0] have been used, in place of carbon monoxide, as reagents for the conversion of amines into isocyanates via this route (28,29). Alternatively, aniline [62-53-3] toluene diamines (I JJA), and methylene dianilines (MDA) have also been used as starting materials in the carbonylations to provide a wide variety of isocyanate monomers. 

Other approaches have explored the reaction of amines with dimethyl carbonate or its precursors (28). A reaction scheme for the production of polymeric MDI is as follows ... 

Wetting times of /V,/V-dimethy1-/ -alkyl amine oxides as a function of the alkyl chain length show a minimum with dimethyl dodecyl amine oxide (Table 3). Foam generation of dimethyl-/ -alkylamine oxides solutions show a maximum when the alkyl group contains 14 carbons. 

For primary aromatic amines dimethyl carbonate, Y-Zeolite, 130-150°, 72-93% yields. ... 

It is supposed that the nickel enolate intermediate 157 reacts with electrophiles rather than with protons. The successful use of trimethylsilyl-sub-stituted amines (Scheme 57) permits a new carbon-carbon bond to be formed between 157 and electrophiles such as benzaldehyde and ethyl acrylate. The adduct 158 is obtained stereoselectively only by mixing nickel tetracarbonyl, the gem-dibromocyclopropane 150, dimethyl (trimethylsilyl) amine, and an electrophile [82]. gem-Functionalization on a cyclopropane ring carbon atom is attained in this four-component coupling reaction. Phenyl trimethyl silylsulfide serves as an excellent nucleophile to yield the thiol ester, which is in sharp contrast to the formation of a complicated product mixture starting from thiols instead of the silylsulfide [81]. (Scheme 58)... 

Dimethylarsinic acid (DMA), 3 274 present in water and food, 3 276t Dimethylbenzyl carbinol, aroma chemical derived from toluene, 3 234 N, AT-Dimethylbenzyl vinyl amine (DMBVA), 20 487 Dimethylbismuthine, 4 18, 26 Dimethylbromostibine, 3 68 Dimethylcadmium, 4 516-517 physical properties of, 4 517t Dimethyl carbonate, 6 313-314... 

Aresta and Quaranta studied the reactivity of alkylammonium N-alkylcarbamates (RNH3)02CNHR towards a different acylating substrate, such as dimethyl carbonate (DMC) [62a, b]. Carbamate salts (RNH3)02CNHR (R = benzyl, allyl, cyclohexyl), prepared in situ from aliphatic primary amines and C02, reacted with DMC to afford N-alkyl methylcarbamates (Equation 6.6). The reaction requires mild conditions (343-363 K 0.1 MPa C02 pressure) and can be carried out in DMC used as solvent and reagent. At 363 K, carbamate esters were obtained in satisfactory yield (45-92%) with high selectivity, as side products such as ureas, N,N-dialkylcarbamate esters, and alkylated amines were formed in very small amounts. 

Scheme 6.7 Synthesis of carbamates from aliphatic primary amines and dimethyl carbonate (DMC) in the presence of C02. The catalytic role of C02.

A fourth type of product, a carbamate RNHCOOR , can be obtained from primary or secondary amines, if these are treated with CO, O2, and an alcohol R OH in the presence of a catalyst. " Primary amines react with dimethyl carbonate in supercritical CO2 (see p. 414) to give a carbamate. " Carbamates can also be obtained from nitroso compounds, by treatment with CO, R OH, Pd(OAc)2, and Cu(OAc)2, " and from nitro compounds. " When allylic amines (R2C=CHRCHRNR 2) are treated with CO and a palladium-phosphine catalyst, the CO inserts to produce the p,y-unsa-turated amides (R2C=CHRCHRCONR 2) in good yields. " Ring-expanded lactams are obtained from cyclic amines via a similar reaction (see also, 16-22). Silyloxy carbamates (RNHC02SiR 3) can be prepared by the reaction of a primary amine with carbon dioxide and triethylamine, followed by reaction with triisopropylsilyl triflate and tetrabutylammonium fluoride. ... 

Even though formic anhydride is not a stable compound (see p. 723), amines can be formylated with the mixed anhydride of acetic and formic acids (HCOO-COMe) or with a mixture of formic acid and acetic anhydride. Acetamides are not formed with these reagents. Secondary amines can be acylated in the presence of a primary amine by conversion to their salts and addition of 18-crown-6. The crown ether complexes the primary ammonium salt, preventing its acylation, while the secondary ammonium salts, which do not fit easily into the cavity, are free to be acylated. Dimethyl carbonate can be used to prepare methyl carbamates in a related procedure. A-Acetylsulfonamides were prepared from acetic anhydride and a primary sulfonamide, catalyzed by Montmorillonite KlO-FeO or sulfuric acid. "... 

For primary aromatic amines dimethyl carbonate, Y-zeolite, 130-150°C, 72-93% yields. Y-faujasites have been used as catalysts and require lower temperatures to achieve methylation. CO2 must be removed with a stream of N2 to prevent carbamates formation. ... 

Dimethyl carbonate can be used to alkylate phenols, aromatic amines, acetylenes, and active methylene compounds. What other alkylations might be carried out with it that are now performed with iodomethane or dimethyl sulfate ... 

DIMETHYL CARBONATE (616-38-6) Forms explosive mixture with air (flash point 66°F/19°C oc). Reacts violently with strong oxidizers, strong bases, potassium-rert-butoxide. Incompatible with sulfuric acid, aliphatic amines, alkanolamines, amides, organic anhydrides, isocyanates, vinyl acetate, alkylene oxides, epichlorohydrin. Incompatible with aluminum, magnesium, silicone. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Carbamates and ureas. Stepwise displacement of the methoxy groups of dimethyl carbonate by amines leads to carbamates and then ureas. ... 

Treatment of 20 with dimethyl carbonate led to carbamate 21, which was reduced by hydrogenation over 5% Rh/C to afford the corresponding piperidine 22 as a 17 1 mixture of cis trans diastereomers. A reductive amination using benzaldehyde provided 23 as the hydrochloride salt. The carbamate was reduced with LAH and resolved with di-p-toluoyl-L-tartaric acid to provide the DPTTA salt of 14. 

Dimethyl carbonate and diphenyl carbonate as amine carboxylating reagents... 

Carbonic add diesters are very attractive reagents and of great economic interest because they represent safe, nonenvironmentally acceptable alternatives to phosgene for carbonylation and carboxylation reactions. For example, methoxycarboxylation with dimethyl carbonate offers an eco-friendly alternative route for the production of carbamates and isocyanates, which are valuable precursors of ureas (see Sections 4.3.1 and 4.3.2) [781, 782]. The method is comparable, from an environmental point of view, with the transition metal catalyzed carbonylation of nitro compounds and amines with CO. 

It has been reported that reaction of tran.s-1,2-diaminocyclohexane 1136a with either phosgene or phosgene equivalents such as l.l -carbonyldiimidazole, urea, dimethyl carbonate, or methyl chloroformate does not give the desired imidazolidin-2-one 1139a, but rather an oligomeric product [806]. This indicates that the in-termolecular reaction competes effectively with the intramolecular cyclization, a result that has some precedent in the reaction of 1,2-diaminoethane (ethylenedi-amine) with urea [807]. 

Nevertheless, this does not seem to be a useful route from an industrial point of view. Similarly, the use of solid triphosgene, CO(OCCb)2, in place of phosgene in the reaction with amines [12], although useful as far as transport and storage are concerned, does not appear to be a significant solution to the industrial problems. Note that triphosgene is prepared by reaction of chlorine with dimethyl carbonate. 

Sc(OTf) 3 was found to be a more active catalyst for carbomethoxylation of aliphatic amines with dimethyl carbonate (DMC) than a homolog La salt (Scheme 12.39)... 

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