Ethyl carbamate oxidation

Ethyl carbamate, C2HyN02, is developed naturally during the fermentation of alcohoHc beverages. It also appears in foods such as bread and yogurt. Since ethyl carbamate is not easily distilled, its formation most likely involves a distillable precursor. The mechanism of ethyl carbamate formation probably involves cyanate produced from the oxidation of cyanide or from urea-based compounds in the beer. Cyanate reacts with alcohol to form ethyl carbamate as follows ... 

The in vivo metabolism of a homologous series of alkyl carbamates (7.2, Fig. 7.3) has yielded some informative results [13]. The hydrolysis of these esters liberates carbamic acid (7.3, Fig. 7.3), which breaks down spontaneously to C02 and NH3, allowing the extent of hydrolysis to be determined conveniently and specifically by monitoring C02 production. When such substrates were administered to rats, there was an inverse relationship between side-chain hydroxylation and ester-bond hydrolysis. Thus, for compounds 12 the contribution of hydrolysis to total metabolism (90 - 95% of dose) decreased in the series R=Et (ca. 85-90%), Bu (ca. 60-65%), hexyl (ca. 45 - 50%), and octyl (ca. 30%). Ethyl carbamate (urethane) is of particular toxicological interest, being a well-established carcinogen in experimental animals. In vitro studies of adduct formation have confirmed the competition between oxidative toxification mediated by CYP2E1 and hydrolytic detoxification mediated by carboxylesterases [14]. 

Carbamates have been prepared by heating ethyl carbamate with a higherboiling alcohol in the presence or absence of catalysts [31-33], Aluminum iso-propoxide has been reported [34] to be an excellent catalyst for the interchange reaction between ethyl carbamate and benzyl alcohol. The interchange reaction is also effective for /V-alkyl carbamates as well as unsubstituted carbamates [35]. This catalyst is effective in preparing mono- and dicarbamates in excellent yields from primary and secondary alcohols and diols. Other effective catalysts are dibutyltin dilaurate [36], dibutyltin oxide [37], sulfuric acid or p-toluenesulfonic acid [31], and sodium metal (reacts with alcohols to give the alkoxide catalyst) [33]. 

A related reaction accompanied by cyclization occurred with ortho-substituted benzamides (and also non-cyclic amides such as RCH(CONH2)2 [60]. Several compounds with a primary amino group, such as t-butylamine, p-tol uenesulphona-mide, ethyl carbamate, etc. were oxidized by DIB in presence of alkenes or nitroso compounds to give, respectively, aziridines or azoxy compounds. 

When the reaction was carried out in chloroform in the presence of ethyl carbamate with boron trifluoride-etherate as catalyst, /J-ethoxycarbonylaminoalkyl phenyl tellurium oxides were formed. These tellurium oxides were not purified but reduced with hydrazine to the corresponding tellurium compounds. ... 

When the addition reactions were performed in the presence of (9-ethyl carbamate, 2-(0-elhylcarbamoylamino)-l-alkyl and 2-((9 -ethylcarbamoylamino)-alkyl phenyl tellurium oxides were formed. The tellurium oxides were once again not isolated but reduced with hydrazine hydrate to the corresponding alkyl phenyl telluriums4. 

Sharpless and co-workers first reported the aminohydroxyIation of alkenes in 1975 and have subsequently extended the reaction into an efficient one-step catalytic asymmetric aminohydroxylation. This reaction uses an osmium catalyst [K20s02(OH)4], chloramine salt (such as chloramine T see Chapter 7, section 7.6) as the oxidant and cinchona alkaloid 1.71 or 1.72 as the chiral ligand. For example, asymmetric aminohydroxylation of styrene (1.73) could produce two regioisomeric amino alcohols 1.74 and 1.75. Using Sharpless asymmetric aminohydroxylation, (IR)-N-ethoxycarbonyl-l-phenyl-2-hydroxyethylamine (1.74) was obtained by O Brien et al as the major product and with high enantiomeric excess than its regioisomeric counterpart (R)-N-ethoxycarbonyl-2-phenyl-2-hydroxyethylamine (1.75). The corresponding free amino alcohols were obtained by deprotection of ethyl carbamate (urethane) derivatives. 

Epoxybutane Ethyl acetate Ethyl acrylate Ethyl benzene Ethyl carbamate Ethyl chloride Ethylene dibromide Ethylene dichloride Ethylene glycol Ethylene imine Ethylene oxide Ethylene thiourea Ethylidene dichloride Fine mineral fibers Formaldehyde Glycol ethers Eleptachlor Elexachlorobenzene Elexachlorobutadiene Elexachlorocyclopentadiene Elexachloroethane Elexamethylene-1,6-diisocyanate Elexamethylphosphoramide Elexane... 

If Insufficient lead tetraacetate is used in the oxidation, unoxidized starting enamide is hydrolyzed during the workup to tert-butyl 2-(2-acetyl-3,4-dimethoxyphenyl) ethyl carbamate, mp 111.5-112.5°C (cf. Note 2) 1H NMR (270 MHz,... 

ETHYL CARBAMATE (51-79-6) Incompatible with 2-naphthol, gallium, perchlorate, phosphorus pentachloride, strong oxidizers. 

Scheme 5.11 Multistep oxidations of ethyl carbamate (a) and ethanol (b) catalyzed by ...

The use of lead oxide (PbO) for the conversion of ethyl carbamate (EC) to form diethyl carbonate (DEC) using ethanol has been reported this reaction is the second step in the conversion of urea to DEC by alcoholysis (Scheme 22.15). Of interest is that the catalytic species appears to be a mixture of metallic Pb and PbOj, generated under the reactions conditions from the initially added PbO by reaction with ethanol to generate ethane, acetaldehyde, carbon dioxide and water. This lead oxide catalyst exhibited excellent activity in comparison other metals and high conversion yield (16%), and could be reused up to five times without significant loss in activity. ... 

Guo L, Zhao X, An H, Wang Y (2012) Catalysis by lead oxide for diethyl carbonate synthesis from ethyl carbamate and ethanol. Chin J Catal 33 595-600... 

Carbamates are produced by the oxidative carbonylation of amines in alcohol, and active research on the commercial production of carbamates as a precursor of isoyanates based on this reaction has been carried out. As an example, ethyl phenylcarbamate (582) is produced in a high yield (95%) with... 

The N-oxides of isoquinolines have proved to be excellent intermediates for the preparation of many compounds. Trialkylboranes give 1-alkyl derivatives (147). With cyanogen bromide in ethanol, ethyl N-(l- and 4-isoquinolyl)carbamates are formed (148). A compHcated but potentially important reaction is the formation of 1-acetonyLisoquinoline and 1-cyanoisoquinoline [1198-30-7] when isoquinoline N-oxide reacts with metbacrylonitrile in the presence of hydroquinone (149). Isoquinoline N-oxide undergoes direct acylamination with /V-benzoylanilinoisoquinoline salts to form 1-/V-benzoylanilinoisoquinoline [53112-20-4] in 55% yield (150). A similar reaction of AJ-sulfinyl- -toluenesulfonamide leads to l-(tos5larriino)isoquinoline [25770-51-8] which is readily hydrolyzed to 1-aminoisoquinoline (151). 

Carbodiimides have been prepared by desulfurization of thioureas by metal oxides, by sodium hypochlorite,4 or by ethyl chloroformate in the presence of a tertiary amine by halogena-tion of ureas or thioureas followed by dehydrohalogenation of the N,N -disubstituted carbamic chloride 8 and by dehydration of disubstituted ureas using -toluenesulfonyl chloride and pyridine.7 The method described above is a modification of that of Campbell and Verbanc. ... 

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