Ethyl pyrocarbonate

Ethylpyridine-4-carbothioamide, 2976 Ethyl pyrocarbonate, see Diethyl dicarbonate, 2438 Ethyl sodioacetoacetate, 2398 Ethylsodium, 0873... 

DIETHYL PYROCARBONATE DIETHYL PYROCARBONIC ACID DKD ETHYL PYROCARBONATE... 

In addition to the very important palladium-catalysed reactions, boronic acids undergo a number of useful reactions that do not require transition-metal catalysis, particularly those involving electrophilic ipso-substitutions by carbon electrophiles. The Petasis reaction involves ip,y(9-replacement of boron under Mannich-like conditions and is successful with electron-rich heterocyclic boronic acids. A variety of quinolines and isoquinolines, activated by ethyl pyrocarbonate, have been used as the Mannich reagent . A Petasis reaction on indole 3-boronic acids under standard conditions was an efficient route to very high de a-indolylglycines. " ... 

Chemical stabilization has been accomplished by the addition of sorbates, benzoates, ascorbic acid, sulfur dioxide, or diethyl pyrocarbonate (DEPC). This method has not been universally accepted because of the public s general aversion to chemical preservatives and undesirable side affects. For example, DEPC is very toxic until it breaks down into ethyl alcohol, carbon dioxide, and ethyl pyrocarbonate. 

Purines react with acylating agents such as chloroformates or ethyl pyrocarbonate to give non-isolable A -acyl salts which can suffer various fates following nucleophilic addition products of cleavage of either ring have been observed, as have recyclisation products. " ... 

Diethyl pyrocarbonic acid Ethoxyformic acid anhydride Ethoxyformic anhydride Ethyl pyrocarbonate Formic acid, oxydi-, diethyl ester... 

Ethyl-2-pyridyl) ethyl propenoate. See 2-(5-Ethyl-2-pyridyl)ethyl acrylate Ethyl pyrocarbonate. See Diethyl pyrocarbonate... 

Pyridone and phosgene in tetrahydrofuran give di-(2-pyridyl) carbonate (XII-(H)4). Ethyl pyrocarbonate and pyridinols in aqueous ethanol give the corresponding pyridyl ethyl carbonates. ... 

The use of diethyldicarbonate (DEDC), or ethyl pyrocarbonate (Baycovin), was authorized in the United States and Germany for a few years in the early 1970s. This fungicide is very effective on yeasts after acting it is hydrolyzed in a few hours after application, at a rate that varies with temperature, according to the following reaction ... 

It rapidly became apparent that the reaction of ethyl pyrocarbonate in wine was more complex than indicated by the reaction shown above. Ethyl alcohol and carbon dioxide were certainly the main degradation by-products, but small quantities of ethyl carbonate were also formed, and its fruit aroma was perceptible above a certain threshold. Most importantly, ethyl pyrocarbonate is a highly reactive molecnle and combines with certain substances in wine (organic acids, polyphenols, and nitrogen-based componnds) to produce urethanes, e.g. ethyl carbamate, which is toxic and carcinogenic. Quantities never exceeded 2-4 mg/1, significantly below the ofQcial threshold of 30 mg/1 in Canada. However, this risk was sufficient for the product to be completely abandoned. 

On the basis of these findings, DMDC was initially authorized in the United States, then in other countries. Like ethyl pyrocarbonate, DMDC is most effective at the time of bottling, although it has also been suggested for use in stopping the fermentation of sweet (botrytized) wines (Bertrand and Guillou, 1999), thus reducing the amount of SO2 required. In any case, a certain quantity of free SO2 is always necessary to protect the wine from oxidation. 

A solution of 0.9 mmol of the imine and l.2mmol of diethyl pyrocarbonate in 1.5 mL of dry ethanol (distilled from magnesium ethoxide) is stirred under nitrogen at 60 C for 24 h. Then the solvent is removed in vacuo and the residue flash chromatographed (silica gel, ethyl acetate/hexane 1 5) to give the product as an oil. 

Procedure for BOC-amino acids. A solution of the amino acid (10 mol) in a mixture of dioxane (20 ml), water (10 ml) and 1 m sodium hydroxide (10 ml) is stirred and cooled in an ice-water bath. Di-t-butyl pyrocarbonate (1) (2.4 g, 11 mmol) is added and stirring is continued at room temperature for 30 minutes. The solution is concentrated in vacuo to about 10-15 ml, cooled in an ice-water bath, covered with a layer of ethyl acetate (30 ml) and acidified with dilute aqueous potassium hydrogen sulphate solution to pH 2-3 (Congo red). The aqueous phase is extracted with ethyl acetate (2 x 15 ml). The ethyl acetate extracts are pooled, washed with water (2 x 30 ml), dried over anhydrous sodium sulphate and evaporated in vacuo. The residue is recrystallised with a suitable solvent (e.g. ethyl acetate-hexane). 

Fig. 6. 35. Preparation of the dicarbonate ("pyrocarbonate") H ("Boc anhydride," "Boc20") from potassium tert-butoxide, carbon dioxide and phosgene. The tricarbonate E is isolated as an intermediate. Only upon addition of a catalytic amount of the nucleophilic amine F does E react to afford Boc 0, while the analogous ethyl derivative ofthe tricarbonate does so spontaneously. Boc20 applications are shown in Figures 6.37 and 6.38, an application ofthe analogous diethyldicarbonate is given in Figure 13.62.

Another method of benzannulation to a furan ring uses precursors of type 59, which are available by cross-coupling reaction with the corresponding 3-bromofuran. Upon treatment with ethyl chloroformate and triethylamine, a pyrocarbonate is formed which acylates the furan nucleus in an intramolecular reaction. With an excess base the 7-hydroxybenzofurans are obtained (Equation 123) <1998TL5609>. 

OXYDIFORMIC ACID DIETHYL ESTER PIREF PYROCARBONATE d ETHYLE (FRENCH) PYROCARBONIC ACID, DIETHYL ESTER PYROKOHL-ENSAEURE DIAETHYL ESTER (GERMAN)... 

Preservatives for wines, soft drinks, fruit juices, especially in the case of diethyl pyrocarbonate R = R = Ethyl. 

Diethyl oxide. See Ethyl ether 0,0-Diethyl-S-(4-oxo-3H-1,2,3-benzotriazine-3-yl)-methyl dithiophosphate 0,0-Diethyl-S-4-0X0-1,2,3-benzotriazin-3(4H)-yl methyl phosphorodithioate. See Azinphos-ethyl Diethyl oxydiformate. See Diethyl pyrocarbonate Diethyl palmitoyl aspartate Definition Palmitic amide of diethyl aspartate Empirical C24H45NO6 Uses Emollient in cosmetics... 

Formic acid methyl ester. See Methyl formate Formic acid 1-methyl-1-(4-methyl-cyclohex-3-enyl) ethyl ester. See Terpinyl formate Formic acid, neryl ester. See Neryl formate Formic acid octyl ester. See Octyl formate Formic acid, oxydi-, diethyl ester. See Diethyl pyrocarbonate... 

Diethyl pyrocarbonate 4,4 -(2-Ethyl-2-nitrotrimethylene) dimorpholine Ferulic acid Fluorosalan Hexetidine Kojic acid d-Limonene Mandelic acid Myrtrimonium bromide 2-Nitro-1-butanol 4-(2-Nitrobutyl) morpholine 2-Nitro-2-ethyl-1,3-propanediol 2-Nitro-2-methyl-1 -propanol Octadecyidimethyl [3-(trimethoxysilyl) propyl] ammonium chloride Sodium chlorite. Sulfacetamide Sulfamethizole Thymol Zinc pyrithione... 

Diethyl pyrocarbonate 1609-86-5 t-Butyl isocyanate 1623-19-4 Triallyl phosphate 1629-58-9 Ethyl vinyl ketone... 

Diethyl pyrocarbonate 216-544-9 t-Butyl isocyanate 216-624-3 Ethyl vinyl ketone 216-633-2... 

Since diethyl carbonate may be a teratogenic agent and ethyl urethane is a carcinogen, the use of diethyl pyrocarbonate is discussed under toxicological aspects. The compound should be replaced by dimethyl pyrocarbonate, since methyl urethane, unlike ethyl urethane, is not carcinogenic. 

Diethyl dicarbonate (diethyl pyrocarbonate) was used in the past as a preservative for soft drinks and some alcohohc beverages (including wine). In aqueous solution, however, diethyl dicarbonate is rapidly hydrolysed to ethanol and carbon dioxide, and in alcoholic beverages it is transformed into diethyl carbonate by reaction with ethanol. In the presence of ammonium salts toxic ethyl carbamate then results, which is also known as urethane (Figure 11.2). For these reasons, diethyl dicarbonate is not approved in the EU, but the approved compound is dimethyl dicarbonate (E242), which can be used for the preservation of soft drinks, teas, herbal teas and in some countries to stabilise wine. The methyl carbamate produced from dimethtyl dicarbonate is a non-toxic substance. In treated wines it occurs in amounts up to 10 xg/l. 

Formylphenoxyacetic acid added at 40° during 10 min. to diethyl pyro-carbonate, heated 3 hrs. at 80° until dissolved, more diethyl pyrocarbonate added, and heating continued for 2 hrs. ethyl 4-formylphenoxyacetate. Y 92.5%.—This mild method is particularly suited for compounds bearing additional reactive groups. F. e. and reactions s. W. Thoma and H. Rinke, A. 624, 30 (1959). 

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