Acid anhydrides, reaction with

In this type of protein immobilization, reactions involve the acylation of an NH2 group on a protein or an enzyme by pendent groups of the carrier such as azide, acid anhydride, carbodiimide, sulfonyl chloride, and hydroxysuccinimide esters. Copolymers of acrylamide and maleic anhydride have been useful for enzyme immobilization through the acid anhydride reaction with the enzyme. This system of... 

Acid anhydrides react with alcohols to form esters The reaction may be carried out in the presence of pyridine or it may be catalyzed by acids In the example shown only one acyl group of acetic anhydride becomes incorporated into the ester the other becomes the ac yl group of an acetic acid molecule... 

Reaction with Acid Anhydrides. Below room temperature, acid anhydrides react with alkanolamines to produce amides, which partially rearrange to esters on warming to room temperature or slighdy above. 

Organic Chlorides/Halides — Several organic compounds also are hydrolyzed (or react with water) to produce corrosive materials. Notable inclusions among these compounds are acetic anhydride ([CH3COJ2O), and acetyl chloride (CH3COCI), both of which produce acetic acid upon reaction with water. Both acetic anhydride and acetyl chloride are corrosive in addition, mixtures of the vapors of acetic anhydride and acetic acid are flammable in air, and acetyl chloride itself is flammable. 

Reaction with alcohols (Section 15.8) Acid anhydrides react with alcohols to form esters. 

Reaction with ammonia and amines (Section 20.14) Acid anhydrides react with ammonia and amines to form amides. 

Somewhat milder oxidative conditions lead to loss of but one carbon. Periodic acid cleavage of the side chain in 65, leads to the so-called etio acid (66). Reaction with propionic anhydride leads to acylation of the 17-hydroxyl group (67). Possibilities for neighboring group participation severely limit the methods available for activating the acid for esterification. Best results seemed to have been obtained by use of a mixed anhydride from treatment with diphenyl chloro-... 

The chemistry of acid anhydrides is similar to that of acid chlorides. Although anhydrides react more slowly than acid chlorides, the kinds of reactions the two groups undergo are the same. Thus, acid anhydrides react with water to form acids, with alcohols to form esters, with amines to form amides, and with UAIH4 to form primary alcohols. Only the ester and amide forming reactions are much used, however. 

Phosphorus pentachloride, for conversion of pentaacetylgluconic add to add chloride, 41, 80 for oxidation of cycloheptatriene to tropylium fluoborate, 43, 101 with cyanoacetic acid, 41, 5 Phosphorus tribromide, reaction with 1.5-hexadien-3-ol, 41, 50 Phthalic anhydride, reaction with L-phenylalanine to yield N-phthalyl-L-phenylalanine, 40, 82 Phthalic monoperacid, 42, 77 N-Phthalyl-i.-alanine, 40, 84 N-Phthalyl-/3-alanine, 40, 84 N-Phthalylglycine, 40, 84 N-Phthalyl-l-/5-phenylalanine, 40, 82... 

In addition to acyl halides and acid anhydrides, there are a number of milder and more selective acylating agents that can be readily prepared from carboxylic acids. Imidazolides, the (V-acyl derivatives of imidazole, are examples.115 Imidazolides are isolable substances and can be prepared directly from the carboxylic acid by reaction with carbonyldiimidazole. 

A racemic alcohol may be converted into a racemic acid by reaction with one molar equivalent of phthalic anhydride the product is a half ester of a dicarboxylic acid (see Section 7.9.1). This can now be subjected to the resolution process for acids and, in due course, the alcohols can be regenerated by hydrolysis of the ester. 

Reactions with anhydrides and acid chlorides are more rapid and can occur in an essentially nonreversible fashion. But, anhydrides and acid chlorides are considered high-energy reactants since they often involve additional energy-requiring steps in their production, and are thus less suitable for large-scale production of materials. The activity energies for direct esterification and transesterification are on the order of 30 kcal/mol (120 kJ/mol) while the activation energies for anhydride and acid chloride reaction with alcohols are on the order of 15-20 kcal/mol (60-80 kJ/mol). 

Bi(0Tf)3-xH20 proved to be a superior catalyst than BiCl3 for FC acylation (Schemes 7 and 8). Its activity as a Lewis acid is restricted to acid anhydrides since with acid chlorides Bi(0Tf)3-xH20 leads to ligand exchange reactions in which mixed anhydrides (RCOOTf, see path a in Scheme 8) are the active acylating... 

The corresponding imides (1.40), called fulgimides, are most readily synthesised by conversion of the fulgide into the succinamic acids by reaction with amines, followed by dehydration. Functionalisation of the anhydride can also be achieved by reaction of the fulgides with malononitrile in the presence of diethylamine and subsequent recyclisation with acetyl chloride to give (1.41) from the corresponding E-fulgide and (1.42) from the Z-isomer. 

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