Anhydrides of carboxylic acids

Lactones, which may be regarded as cyclic or inner esters, react similarly. Anhydrides of carboxylic acids also react with hydroxylamine to form hydroxamic acids ... 

Theperfluoroorganozmc compounds have limited application in organic syn thesis because of their lack of reactivity However, heptafluoro I methylethylzinc iodide reacts with acyl fluorides or anhydrides of carboxylic acids in the presence of pyndine to give the corresponding ketones [7S] (equations 28 and 29) In the presence of zinc fluoride, acyl chlorides can be used as substrates [7d]... 

Anhydrides of carboxylic acids will consume only half a mole of sodium ethoxide per original carboxyl group ... 

We are now familiar with anhydrides of carboxylic acids, e.g. acetic anhydride, and of phosphoric acid, e.g. ATP. In each case we can rationalize their reactivity by considering nucleophilic attack onto the C=0 or P=0, followed by loss of a leaving group, carboxylate or a phosphate derivative. 

The nomenclature for this homologous series is somewhat confused. The term PANs has been used historically to denote peroxyacyl nitrates, and this terminology continues to be used extensively in the literature, despite the lack of adherence to traditional IUPAC rules of nomenclature. Because the PANs can be considered to be mixed anhydrides of carboxylic acids and nitric acid, another suggestion (Roberts, 1990) has been peroxyacetic nitric anhydride for CH,C(0)00NO2 and peroxy carboxylic nitric anhydrides for the whole class of compounds. Although it does not follow the IUPAC rules, it would be consistent with the widespread use of the name PAN but also reflect the structure more accurately. Table 6.20 shows the structures and commonly used names of some PANs that have been observed in the atmosphere and/or in laboratory studies. 

New Soluble Catalysts. Trifluoromethansulfonic acid (triflic acid, TfOH)42 and acyl triflates, that is mixed anhydrides of carboxylic acids and triflic acid,43 44 were first reported to be effective for Friedel-Crafts acylation in 1972. Significantly lower yields (<30%) were obtained with other Brpnsted acids. High activities were also observed for perfluorobutanesulfonic acid.37... 

The dicarbonyl [12539-66-1] available from 1,10-(N2)2B10H8 is another important species because of the scope ofits chemistry. Carbonyls of P 12 -12] can be formed from CO and the conjugate acid of [B12H12]2 . The B10- and B12-carbonyls exhibit very similar reactivity (99). The carbonyls can be considered anhydrides of carboxylic acids and accordingly react with alcohols and amines-to give esters and amides ... 

Studies on mixed anhydrides of carboxylic acids and triflic acid have shown them to be extremely powerful acylating agents.350 Similarly, higher perfluoroalkanesulfonic acids also form mixed anhydrides.351... 

The catalytic action of ChE s is, however, not limited to ester hydrolysis. Thus, these enzymes catalyze also the reverse reaction, i.e., esterification of acids with choline (14). They promote transesterification 15) and the condensation of hydroxylamine with acids 14) or esters 15). Anhydrides of carboxylic acids are also substrates of ChE s 16, 17) and can undergo all the reactions, mentioned with esters, i.e., hydrolysis, esterification, and hydroxamation. 

Except for lactam n-acyl derivatives, compounds such as esters, anhydrides and halogen anhydrides of carboxylic acids, which can activate lactam polymerization, can also be used as activators (promoters). 

Reactions between a representative range of alkyl- and aryl-amines and of aliphatic and aromatic acids showed that the direct formation of amides from primary amines and carboxylic acids without catalyst occurs under relatively low-temperature conditions (Scheme 1). The best result obtained was a 60% yield of N-bcnzyl-4-phenylbutan-amide from benzylamine and 4-phenylbutanoic acid. For all these reactions, an anhydride intermediate was proposed. Boric and boronic acid-based catalysts improved the reaction, especially for the less reactive aromatic acids, and initial results indicated that bifunctional catalysts showed even greater potential. Again, anhydride intermediates were proposed, in these cases mixed anhydrides of carboxylic acids and arylboronic acids, e.g. (I).1... 

Carboxylic acid dimethylamides Anhydrides of carboxylic acids when heated with excess hexamethylphosphorous triamide at 150 170° are convened into carboxylic... 

The requisite W-methoxy-W-methylamides may be pre >ared from acid chlorides by employing a slight excess of the commercially available W,G-dimetiiylhydroxylamine hydrochloride in the presence of pyridine. They have also been pre >ared from acylimidazoles and from mixed anhydrides of carboxylic acids. Once prepared, these systems X)ssess stability equivalent to that of most tertiary amides and, in... 

Mixed anhydrides of carboxylic acids (RCO2H) and thiohydroxamic acid react with Sb(SPh)3 in the presence of O2 and water to give alcohols (ROH) via RSb(SPh)2 intermediates (Scheme 14.7) [28]. Both thioethers and sulfoxides bearing a hydrogen atoms are converted to a-fluorothioethers by treatment wifh (diefhylamino)sulfur trifluoride under Sb(.T, catalysis (Scheme 14.8) [29]. Treatment of 2-amino-6-halo nucleosides with tert-butyl nitrite in the presence of SbCls affords the 2-chloro-6-halopurine nucleosides (Scheme 14.9) [30]. 

Aminotetrazole, under the action of tosyl chloride in alkaline solution, yields 1-tosylaminotetrazole however, on carrying out the same reaction with chlorides and anhydrides of carboxylic acids, a characteristic reaction for tetrazoles—transformation to 2-acylamino-l,3,4-oxadiazoles—took place (60CB850). 

Pudovik, A.N., and Konovalova, I.V., Reaction of chlorides of carboxylic acids and anhydrides of carboxylic acids with diethyl sodiophosphonate, Zh. Obshch. Khim., 33, 98, 1963 Chem. Abstr, 59, 656a, 1963. 

The introduction of 0-acyl thiohydroxamates (mixed anhydrides of carboxylic acids with thiohydroxamic acids) by the Barton group in 1983 [1] has provided one of the mildest and most convenient and versatile sources of carbon-centered radicals which fulfill the above criteria, and can hence, in Sir Derek s own words, be described as disciplined . Since their preparation from carboxylic acids is extremely straightforward, and since they have demonstrated a rapacious radicophilicity in a wide variety of very useful transformations, it is no surprise that these derivatives are commonly named either as Barton esters or by the acronym PTOC (pyridine thiocarbonyl) esters. The ongoing development of this chemistry has been summarized over the years in several useful reviews [2], and some of the tried and tested experimental procedures have also been collated [3]. 

Anhydrides of carboxylic acids are best prepared by the classical method of treating acid chlorides with salts of acids, a method that can be used equally for preparing mixed anhydrides. The salt may be replaced by the free acid if pyridine is added to the reaction mixture. Further, water may be removed directly from carboxylic acids, either by heat in certain cases where aliphatic or aromatic dicarboxylic acids give cyclic anhydrides, or by means of acetic anhydride or acetyl chloride. 

Chemical Transformations of Saturated Heterocyclic Compounds Containing C=0 or SO2 Groups The reactivity of this class of compounds is governed by the functional groups such as C=0 or SO2. For example, the lactone 22, cyclic anhydrides of carboxylic acids 24 or 25, or sulfonic acids... 

Anhydrides of carboxylic acids were obtained in 53-95% yield by treatment of appropriate carboxylic acids with CDMT or 2,4-dichloro-6-methoxy-l,3,5-triazine (DCMT) in the presence of A -methylmorpholine <1985TL2901>. 

Examples of the resin components of expoxies are listed in Table 1. Several chemical substances can be used as hardeners for epoxies [5,6], The two main groups of cross-linking agents used in industry are two or more functionalized amines and anhydrides of carboxylic acids. Cross-linking with amines is possible at room temperature as well as at elevated temperatures, depending on the chemical structure of the amines (Table 2). Anhydrides of carboxylic acids react at elevated temperatures only. 

A particular group of acid anhydrides are anhydrides of carboxylic acids. They have a general formula of the type R.CO.O.CO.R, ... 

One of the simplest and most efficient methods of acylation is the treatment of amines (or other nucleophiles) with anhydrides of carboxylic acids. Acetylation with acetic anhydride is common practice and it may seem rather surprising that the analogous reaction has not been used for peptide bond formation from the earliest days of peptide synthesis. One possible explanation for this delay in the acceptance of anhydrides is the wastefulness of the process. Of the two molecules of the carboxylic acid comprised in the molecule of the anhydride only one is incorporated into the product while the other is regenerated but usually not recovered ... 

Another strategy for in situ activation, used for the s3uithesis of aliphatic cellulose esters, is the exploitation of DCC in combination with 4-pyrrolidinopyridine (PP) [35]. Among the advantages of this method are the high reactivity of the intermediately formed mixed anhydride with PP and a completely homogeneous reaction in DMA/LiCl up to hexanoic acid. If the reaction is carried out with the anhydrides of carboxylic acids, the carboxylic acid liberated is recycled by forming the mixed anhydride with PP, which is applied only in a catalytic amount. The toxic DCC can be recycled from the reaction mixture (Fig. 16.4). In addition, the method is utilized to obtain unsaturated esters (e.g. methacrylic-, cinnamic-, and vinyl acetic acid esters) and esters of aromatic... 

The curing (hardening) of epoxy compounds can be produced by (a) anhydrides of carboxylic acids [poly(carboxylic acid anhydrides)], (b) compounds with active hydrogen [polyamines, polyphenols, polyalcohols, poly(carboxylic acids), polythiols], or (c) catalysts such as Lewis acids or t-amines. These compounds, which are called curing agents, are used in quantities of up to 30-40 % by weight. 

Because of the special importance of anhydrides of phosphoric acid in biochemical systems (Chapter 21), we include them here to show the similarity between them and the anhydrides of carboxylic acids. The functional group of a phosphoric anhydride is two... 

Anhydrides of carboxylic acids are, as the name suggests, the product of two carboxylic acid units that couple together with loss of water. It is possible to convert carboxylic acids directly to anhydrides, but more commonly they are prepared from acid chlorides. Once an acid chloride has been prepared, it is highly reactive in the presence of a variety of nucleophiles, even relatively weak nucleophiles. In Section 20.2, for example, the reaction of an acid chloride with water gave the parent carboxylic acid. Acid chlorides react with other carboxylic acids to form anhydrides where the acid behaves as a nucleophile. 

Hydroxylamine-ferric chloride for lactones, esters, amides and anhydrides of carboxylic acids. 

Mixed anhydrides of carboxylic acids normally react with alcohols or amines to give a mixture of esters or amides, respectively, according to Eq. (2). 

The Mechanism of reaction of acylation of bicyclophosphites by chlorine anhydride of carboxylic acids consists of three stages. The first stage of reaction is investigated in Ref [4]. The mechanism of the second stage of reaction now is not studied. One of the first investigation phases of the mechanism of synthesis of studied compound (I) can consider an estimation of acid force of components of synthesis pKa (II) and pKa (III) and a required product pKa (I) and an establishment of dependence between them. 

The Mechanism of reaction acylation of bicycle phosphites by chlorine anhydride of carboxylic acids consists of three stages. The mechanism of the first stage is studied by us in Ref [1]. Results of research of the second stage of this reaction are presented in the yielded work. The second stage represents interaction of acetyl chloride and 5-acetyloxymethyl-2-chlorine-5-ethyl-l,2,3-dioxaphosphorynan ina gas phase ... 

Cyclic anhydrides of carboxylic acid are also used as cross-linkers for epoxy resins. Curing is initiated by reaction of a hydroxyl with an anhydride to yield a half ester and a carboxylic acid group. The newly formed carboxylic acid will in turn react with the epoxy to generate an ester and a new hydroxyl group. These complementary reactions result in a cross-linked network. Etherification reactions... 

---