Acetic anhydride Conversion

As one might expect, the addition of carbanions to the ylide (34) results in addition to the iminium bond. Similarly, this bond is reduced to form the diazetidinone (35), which displays some interesting chemistry, such as ring-expansion to an oxadiazine upon treatment with acetic anhydride.Conversion of the ylide into 3-oxo-1,2-diazetidinium tosylate (36) is achieved by using toluene-p-sulphonic acid. Treating the tosylate with a 1,3-dicarbonyl compound provides a novel route to pyrazoles. ... 

Conversion of (3- into a-glucose penta-acetate. Add 0-5 g. of anhydrous zinc chloride rapidly to 25 ml. of acetic anhydride in a 200 ml. round-bottomed flask, attach a reflux condenser, and heat on a boiling water bath for 5-10 minutes to dissolve the solid. Then add 5 g. of the pure P glucose penta-acetate, and heat on a water bath for 30 minutes. Pour the hot solution into 250 ml. of ice water, and stir vigorously in order to induce crystaUisation of the oily drops. Filter the solid at the pump, wash with cold water, and recrystaUise from methylated spirit or from methyl alcohol. Pure a-glucose penta-acetate, m.p. 110-111°, will be obtained. Confirm its identity by a mixed m.p. determination. 

From aldehydes by conversion into the oximes, followed by removal of the elements of water by the action of acetic anhydride, for example ... 

The nitric acid used in this work contained 10% of water, which introduced a considerable proportion of acetic acid into the medium. Further dilution of the solvent wnth acetic acid up to a concentration of 50 moles % had no effect on the rate, but the addition of yet more acetic acid decreased the rate, and in the absence of acetic anhydride there was no observed reaction. It was supposed from these results that the adventitious acetic acid would have no effect. The rate coefficients of the nitration diminished rapidly with time in one experiment the value of k was reduced by a factor of 2 in i h. Corrected values were obtained by extrapolation to zero time. The author ascribed the decrease to the conversion of acetyl nitrate into tetranitromethane, but this conversion cannot be the explanation because independent studies agree in concluding that it is too slow ( 5.3.1). 

At 4-0 °C using a freshly prepared solution of nitric acid (0-14 mol 1 ) in acetic anhydride for 20 min under these conditions the half-life for the conversion of nitric acid into acetyl nitrate was 7 min. 

At this temperature, and provided that the concentration of acetic acid in the acetic anhydride was small, the conversion of nitric acid into acetyl nitrate would have had a half-life of 7-10 min. The description of the experimental method makes it clear that the solutions used by Dewar in this work contained acetyl nitrate over the vast majority of the reaction. Therefore it must be supposed that in this... 

Synthesis gas is obtained either from methane reforming or from coal gasification (see Coal conversion processes). Telescoping the methanol carbonylation into an esterification scheme furnishes methyl acetate directly. Thermal decomposition of methyl acetate yields carbon and acetic anhydride,... 

Synthesis Gas Chemicals. Hydrocarbons are used to generate synthesis gas, a mixture of carbon monoxide and hydrogen, for conversion to other chemicals. The primary chemical made from synthesis gas is methanol, though acetic acid and acetic anhydride are also made by this route. Carbon monoxide (qv) is produced by partial oxidation of hydrocarbons or by the catalytic steam reforming of natural gas. About 96% of synthesis gas is made by steam reforming, followed by the water gas shift reaction to give the desired H2 /CO ratio. 

Conversion of aniline to acetanilide [103-84-4] by reaction with acetic anhydride, is a convenient method for protecting the amino group. The acetyl group can later be removed by acid or base hydrolysis. 

Scheme 6 depicts a typical penicillin sulfoxide rearrangement (69JA1401). The mechanism probably involves an initial thermal formation of a sulfenic acid which is trapped by the acetic anhydride as the mixed sulfenic-acetic anhydride. Nucleophilic attack by the double bond on the sulfur leads to an episulfonium ion which, depending on the site of acetate attack, can afford either the penam (19) or the cepham (20). Product ratios are dependent on reaction conditions. For example, in another related study acetic anhydride gave predominantly the penam product, while chloroacetic anhydride gave the cepham product (7lJCS(O3540). The rearrangement can also be effected by acid in this case the principal products are the cepham (21) and the cephem (22 Scheme 7). Since these early studies a wide variety of reagents have been found to catalyze the conversion of a penicillin sulfoxide to the cepham/cephem ring system (e.g. 77JOC2887).

Eastman Chemical Company has operated a coal-to-methanol plant in Kingsport, Tennessee, since 1983. Two Texaco gasifiers (one is a backup) process 34 Mg/h (37 US ton/h) of coal to synthesis gas. The synthesis gas is converted to methanol by use of ICl methanol technology. Methanol is an intermediate for producing methyl acetate and acetic acid. The plant produces about 225 Gg/a (250,000 US ton/a) of acetic anhydride. As part of the DOE Clean Coal Technology Program, Air Products and Cnemicals, Inc., and Eastman Chemic Company are constructing a 9.8-Mg/h (260-US ton/d) slurry-phase reactor for the conversion of synthesis gas to methanol and dimethyl... 

Snyder and Smith prepared diethyl acetamidomalonate in 40% yield by reduction of diethyl isonitrosomalonate in ethanol over palladium on charcoal followed by direct acetylation of diethyl aminomalonate in the filtrate with acetic anhydride. Ghosh and Dutta used zinc dust instead of palladium. A modification using Raney nickel is described by Akabori et al. Shaw and Nolan reported a 98% yield by conversion of diethyl oximino-malonate-sodium acetate complex. 

On boiling with 25 per cent, hydrochloric acid cphedrine is partially converted into -ephedrine. This change is reversible, an equilibrium mixture of the two bases being formed, though according to Mitchell the commercially desirable conversion of 0-ephedrine into Z-ephedrine is effected with more difficulty than the reverse process. Mitchell also states that when ephedrine is heated with acetic anhydride at 70° for ten minutes it is converted into 0-acetylephedrine,. 2H2O,... 

Olefins may be obtained by elimination from the organoboron intermediates formed from enol derivatives and diborane. " As in the reaction with a,jS-unsaturated ketones (section IX), the conversion is carried out in two parts first formation of the diborane adduct and second, decomposition in refluxing acetic anhydride. 

A later variation of the general method, which extends the scope to 20-ketones, involves reaction of the ketone with benzylamine to give the imine, followed by conversion to the A-acetyl derivative with acetic anhydride. Although the resulting compound also has a A -double bond, it does not react sufficiently fast with peracid, and a A -double bond can not be preserved. 

Equation (3-178) suggests that a plot of A obs/[ROH] vs. [N] will be linear. Because the conversion to the intermediate is quantitative, [N] = [N]o — [AXJq. Plots according to Eq. (3-178) were linear, permitting ky and A in to be estimated. Turning to the acetic anhydride—alcohol system, it is inferred that (in the absence of water) itj/lLi is close to zero (Scheme XXIV). Although the intermediate could not be detected spectrally, its possible presence is admitted in the rate equation for the loss of anhydride ... 

Several examples exist for the conversion of 5-aminothiazoles into the corresponding thiazolopyrimidines. Shaw and Butler report the formation of aminothiazole thiocarboxyamide 27 from the thioamide 26 and carbon disulphide using Cook and Heilbron s procedure. Methylation of 27 gave carboxythioimidate 28 which then reacted with sodium hydroxide to give amino-nitrile 29, and with formic acid and acetic anhydride to give the thiazolopyrimidine 30. 

A recent report describes the conversion of A-formyl- and N-acetyl-L-leucine into optically active azlactones with dicyclohexyl-carbodiimide (DCC) [Eq. (29)]. Other cyclization reagents, e.g. acetic anhydride, POCI3, SOCI2, and polyphosphoric acid, cause racemiza-tion. These azlactones react with optically active amino acid esters to give esters of dipeptides with retention of activity. 

Conversion of Acid Anhydrides into Esters Acetic anhydride is often used to prepare acetate esters from alcohols. For example, aspirin (acetylsalicylic acid) is prepared commercially by the acetylation of o-hydroxybenzoic acid (salicylic acid) with acetic anhydride. 

Conversion of Acid Anhydrides into Amides Acetic anhydride is also commonly used to prepare iV-substituted acetamides from amines. For example, acetaminophen, a drug used in over-the-counter analgesics such as Tylenol, is prepared by reaction of p-hydroxyaniline with acetic anhydride. Note that the more nucleophilic -NH2 group reacts rather than the less nucleophilic -OH group. 

Conversion of the aldehyde into a nitrile is accomplished by treatment of an aldose with hydroxvlamine to give an oxime (Section 19.8), followed by dehydration of the oxJme with acetic anhydride. The Wohl degradation does not give particularly high yields of chain-shortened aldoses, but the reaction is general for all aldopentoses and aldohexoses. For example, D-galactose is converted by Wohl degradation into n-lyxose. 

In 1970, it was disclosed that it is possible to achieve the conversion of dimethylformamide cyclic acetals, prepared in one step from vicinal diols, into alkenes through thermolysis in the presence of acetic anhydride." In the context of 31, this two-step process performs admirably and furnishes the desired trans alkene 33 in an overall yield of 40 % from 29. In the event, when diol 31 is heated in the presence of V, V-dimethylforrnamide dimethyl acetal, cyclic dimethylformamide acetal 32 forms. When this substance is heated further in the presence of acetic anhydride, an elimination reaction takes place to give trans olefin 33. Although the mechanism for the elimination step was not established, it was demonstrated in the original report that acetic acid, yV, V-dimethylacetamide, and carbon dioxide are produced in addition to the alkene product."... 

Some other processes are known for sulfoxidation but have no technical importance. The acetic anhydride process has attracted some interest because it does not need exposure to light and enables conversion rates up to 15% of paraffin feedstock. Once started by peroxide or UV light initiation, it propagates without further radical-forming initiation steps. The addition of some 2.5% acetic anhydride to the reacting alkane is crucial to form a mixed anhydride of par-... 

Even though formic anhydride is not a stable compound (see p. 714), 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. 

Whereas conversion of sulfoxides to the corresponding a-acyloxysulfides by acid anhydrides, for example acetic anhydride, the Pummerer reaction [1], has been known for quite a time, the conversion of sulfoxides with silylating reagents via the unstable intermediate O-silyl compounds to a-silyloxysulfides, the Sila-Pummerer reaction is a relatively new reaction, which has recently been reviewed [1—4-]. 

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