Anhydrides, alcoholysis hydrolysis

Table 11.1-23. Lipase-catalyzed enantiomer- and enantiotopos-differentiating alcoholysis of carboxylic acid esters and anhydrides, alcoholysis or hydrolysis of oxazolin-2-ones, and esterification of carboxylic acids (PPL pig pancreas lipase, PCL Pseudomonas cepacia lipase, ANL Aspergillus niger lipase, CSL Candida sp. lipase, Candida cylindracea lipase, CAL-B Candida antarctica B lipase, CRL Candida rugosa lipase).

Polyesters have been obtained in organic medium by polyesterification of hydroxy acids,328,329 hydroxy esters,330 stoichiometric mixtures of diols and diacids,331-333 diols and diesters,334-339 and diols and cyclic anhydrides.340 Lipases have also been reported to catalyze ester-ester interchanges in solution or in die bulk at moderate temperature.341 Since lipases obviously catalyze the reverse reaction (i.e., hydrolysis or alcoholysis of polyester), lipase-catalyzed polyesterifications can be regarded as equilibrium polycondensations taking place in mild conditions (Scheme 2.35). 

The compounds referred to as azolides are heterocyclic amides in which the amide nitrogen is part of an azole ring, such as imidazole, pyrazole, triazole, tetrazole, benzimidazole, benzotriazole, and their substituted derivatives. In contrast to normal amides, most of which show particularly low reactivities in such nucleophilic reactions as hydrolysis, alcoholysis, aminolysis, etc., the azolides are characterized by high reactivities in reactions with nucleophiles within the carbonyl group placing these compounds at about the same reactivity level as the corresponding acid chlorides or anhydrides. 11... 

For the mechanism of azolide hydrolysis under specific conditions like, for example, in micelles,[24] in the presence of cycloamyloses,[25] or transition metals,[26] see the references noted and the literature cited therein. Thorough investigation of the hydrolysis of azolides is certainly important for studying the reactivity of those compounds in chemical and biochemical systems.[27] On the other hand, from the point of view of synthetic chemistry, interest is centred instead on die potential for chemical transformations e.g., alcoholysis to esters, aminolysis to amides or peptides, acylation of carboxylic acids to anhydrides and of peroxides to peroxycarboxylic acids, as well as certain C-acylations and a variety of other preparative applications. 

The influence of temperature on the ortho effect has been evaluated in the alkaline hydrolysis in aqueous DMSO solutions of ortho-, meta- and para-substituted phenyl benzoates (26). The alcoholysis of phthalic anhydride (27) to monoalkyl phthalates (28) occurs through an A-2 mechanism via rate-determining attack of the alcohol on a carbonyl carbon of the anhydride (Scheme 4). Evidence adduced for this proposal included highly negative A 5 values and a p value of 4-2.1. In the same study, titanium tetra-n-butoxide and tri-n-butyltin ethanoxide were shown to act as effective catalysts of the half-ester formation from (27), the mechanism involving alkoxy ligand exchange at the metal as an initial step. ... 

Esters are less reactive than acid chlorides and acid anhydrides. They are converted to carboxylic acid hy acid or base hydrolysis, and to another ester by acid or base alcoholysis (transesterification). The 1°, 2° or 3° amides are obtained from esters by treatment with ammonia or 1° or 2° amines, respectively. 

Alcoholysis of trihalides 0-6 Hydrolysis of ortho esters 0-20 Alcoholysis of acyl halides 0-21 Alcoholysis of anhydrides 0-22 Esterification of carboxylic acids 0-23 Transesterification 0-24 Alkylation of carboxylic acid salts 0-25 Cleavage of ethers with anhydrides 0-26 Alkylation of carboxylic acids with diazo compounds... 

Each structural assignment of signals 1-7 in the spectrum of Figure 4 is based on the addition of the authentic compound to the crude ozonolysis mixture, and—aside from peak 1—is also based on additional analytical evidence 2,2,3,3-tetrabromobutane (peak 2), 3,3-dibromobu-tanone (peak 4), and acetic acid were actually isolated while acetyl bromide (peak 3) as well as acetic anhydride (peak 5) were further identified by their sensitivity to solvolysis reactions, particularly hydrolysis and alcoholysis to form the corresponding esters. Diacetylperoxide (peak 6) was identified by the disappearance of peak 6 from the NMR spectrum as well as the disappearance of the typical infrared bands at 1810 and 1835 cm"1 when the reaction mixture was treated with sodium iodide. 

The arsonons esters are easily synthesized by the reaction of the dihaloarsines with alcohols or alkoxides. With alcohols, CaCl2 mnst be present because the esters are very sensitive toward hydrolysis, which leads to the reformation of the anhydride (equation 129). The reaction of an alcohol with a bisaminoarsine leads to an arsonous ester (equation 130), as does the alcoholysis of the anhydride. Reaction of diols with bis(drmethylamino)alkylarsines leads to esters of macrocycUc arsinous acid. ... 

Polymers with pendant groups that are derivatives of carboxylic acid can he hydrolyzed to yield poly(acrylic acid). This includes polymers like polyacrylamide, polyacrylonitrile, and polyacrylates. When heated, poly(acrylic acid) form polymeric anhydrides, which undergo typical reactions of anhydrides, such as hydrolysis, alcoholysis, and amidation. 

The influence of temperature on the ortho effect has been evaluated in the alkaline hydrolysis in aqueous DMSO solutions of ortho-, meta- and para-substituted phenyl benzoates (26). The alcoholysis of phthalic anhydride (27) to monoalkyl phthalates... 

P(NB/MA) proved to be surprisingly resistant to hydrolysis, both in solution and as a thin film(2. Moreover, the diacid prepared by hydrolysis in concentrated TMAH reverts to the anhydride upon heating(2ri). Similarly, alcoholysis with methanol is difficult and the methyl half-ester reverts to the anhydride on heating(2ri). Reactions with amines to yield poly(amic acids) and poly(imides) proceed more readily. However polyimides are too strongly absoibing at 193 nm to make suitable resist matrices. Also, because primaiy amines are potent imidization catalysts for amic adds(P), amidization of P(1 /MA) with these also causes strong absoibance at 193 nm. Selective amidization can be achieved with buU secondary amines which yield stable poly(amic add) with aqueous base solubility and acceptable transparency (absorbance = ca 0.5 AU/pm at 193 nm). These materials... 

The relative reactivities toward nucleophilic addition-elimination are acyl chlorides > acid anhydrides > esters carboxylic acids > amides > carboxylate ions. Hydrolysis, alcoholysis, and aminolysis are reactions in which water, alcohols, and amines, respectively, convert one compound into two compounds. 

Treatment of [2- C]malonic acid with acetone in the presence of acetic anhydride and catalytic amounts of concentrated sulfuric acids provides [5- C]Meldrum s acid (419). one of the most versatile low molecular weight building blocks . As summarized in Figure 6.124, its reactivity at C2 is analogous with that of the malonate diesters already discussed. However, the reactivity of the initial adducts differs. For example, hydrolysis or alcoholysis (including tert-BuOH) of the initial adducts with alkyl halides , aldehydes and acyl chlorides gives directly the [2- C]carboxylic acids/esters, a,/3-unsaturated acids/esters and /3-keto acids/esters, respectively, with simultaneous elimination of acetone and In contrast, the 2-(alkoxymethylene)[2- C]malonate... 

The same synthetic approach was used for the preparation of cyclic anhydrides [39- 3]. It was known before that succinic and glutaric acid form cyclic anhydrides which do not polymerize (see Formula 3.1, bottom). HiU and Carothers studied the reactions of higher dicarboxylic acids with acetyl chloride or acetic anhydride. In aU cases, polymeric anhydrides were obtained which were supposed to possess mixed anhydride end groups containing acetyl residues. The sensitivity to hydrolysis alcoholysis and phenolysis prevented exact molar mass measurements. However, a reliable distinction from monomeric cyclic anhydrides was achieved by reaction with aniline, because cyclic anhydrides can only yield one reaction product. When the polymeric anhydrides were heated to 150 °C in vacuum they degraded almost completely by back-biting . In this way 10 new cyclic anhydrides were isolated. These cyclic anhydrides underwent rapid polymerization in contact with traces of moisture. 

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