Acid anhydride derivatives

Saalfrank, Hoffmann and co-workers performed a number of reactions with tetra-alkoxyallenes such as 196 (Scheme 8.47) [1, 41, 105, 114—116] and demonstrated that this class of donor-substituted allenes can serve as a 1,3-dianion equivalent of malonic acid. Treatment of 196 with cyclopropyldicarboxylic acid dichloride 197 produces 2,4-dioxo-3,4-dihydro-2H-pyran 198 through release of two molecules of ethyl chloride [115]. Similarily, the reaction of this allene 196 with oxalyl chloride gives 3-chloromalonic acid anhydride derivative 199. This intermediate is a reactive dieno-phile which accepts 2,3-dimethyl-l,3-butadiene in a subsequent [4+2] cycloaddition to afford cycloadduct 200 in good yield [116]. 

Attempts to prepare acid anhydride derivatives by our methodology were unsuccessful. Various carboxylic acids were reacted with PCTFE in the presence of Cr(CO)6 in efforts to prepare anhydrides, but no appreciable reaction occurred in any case. The major side reaction in each case appears to have been formation of the carboxylated PCTFE derivative. 

The acid anhydride derived from the true hydrogen form, generally called dehydroxylated Y and assumed to be formed according to Reaction 3 of Uytterhoeven, Christner, and Hall (15). 

Another protecting group often employed for amines is the benzyloxycarbonyl group. The chemistry here is reminiscent of that of the BOC group in that the amine is protected by conversion to a carbamate. This time an acyl chloride derivative, car-bobenzoxy chloride, rather than an acid anhydride derivative, is reacted with the amine. 

The 2,3,5-trimethyl-3-chloromethylthiophene was converted to a cyanomethyl derivative with NaCN, and then the cyanomethyl compounds were coupled in an NaOH alkaline aqueous solution in the presence of CC14. The l,2-dicyano-l,2-bis(2,3,5-trimethylthiophen-3-yl)ethene was hydrolyzed in an alkaline solution to produce the acid anhydride derivative. The method can be applied to various diarylmaleic anhydrides. 

Organophosphorous anticholinesterases (OPs), usually acid anhydride derivatives of phosphoric acid, are among the most toxic substances identified. Originally, OP were developed for use as insecticides, but their extreme toxicity toward higher vertebrates has led to their adoption as weapons of warfare." The OPs most com-... 

CjfeHjgOe, Mr 446.58, cryst., mp. 59-60°C. Bis-citra-conic acid anhydride derivative and an inhibitor of leucine and cysteine aminopeptidases from cultures of the wood-rotting fungus Tyromyces lacteus (Basidiomy-cetes). T. shows cytostatic activity. 

Analyses by high-resolution mass spectrometry and electron impact HRGC/MS were used to determine that most of the compounds in the methanol fraction of the LDDI and LDDII extracts were quinones, ketones, and dicarboxylic acid anhydride derivatives of PAHs. Representative compounds tentatively identified in the methanol fractions are given in Table 3. 

Attempts to prepare acid anhydride derivatives by our methodology were unsuccessful. Various carboxylic acids were reacted with PCTFE in the presence of Cr(CO)6... 

Figure 23 McLafferty rearrangement ion nVz 186 of the triflu-oroacetic acid anhydride derivatives of 2-hydroxy fatty acid methyl esters.

Besides the ester and imide derivatives that are known to be polymerized by the noble metal catalysts, nitrile, amide, pyridyl and acid anhydride derivatives were found to undergo polymerization by the present catalyst systems. The ester derivatives were easily polymerized by the binary catalyst to a high conversion at the catalyst-to-monomer molar ratio as low as 10. The nitrile derivatives were less reactive but... 

The ir spectra of the polymers from imide, pyridyl and acid anhydride derivatives were similar to those of the polymers from nitrile and ester derivatives and had an absorption at 970 cm characteristic of C=C linkage, indicating the structure (I). The polymers were resinous and hard materials. Their glass transition temperatures(Tg) are given in TABLE I. 

One can of course ask why only PEG is chosen for protein modification instead of other polymers. Actually, very few examples of conjugation with other polymers have been reported so far, the most successful being the poly(styrene-co-maleic acid/anhydride) derivative of neocardnostatin (SMANCS) developed by Maeda [118]. The main reason Hes in the mono-functionahty of mPEG that avoids a cross-linking reaction with the polyfunc-tionalized proteins. The usual natural or synthetic polymers present multiple points of attachment in the same molecule. This is the case of polysaccharide, for instance, but also for the extensively studied poly(N-(2-hydroxypropyl) methacrylamide) copolymers (HPMA) [119]. 

B) ACID ANHYDRIDES. Acetic anhydride, succinic anhydride phthalic anhydride (and substituted derivatives). 

The choice of type of derivative should be based on whether the chloride or anhydride is aliphatic or aromatic, because this factoi largely determines the reactivity. Aliphatic acid chlorides are best converted into their anilides, as in 4 above aromatic acid chloride may be similarly converted into their anilides, or they may be converted into their amides by shaking with an excess of ammonia (p, 120). (M.ps., pp. 544-545.) Aliphatic acid anhydrides should be converted into their crystalline anilides, but aromatic acid anhydrides arc best hydrolysed to the acid, which can then be converted into one of the standard derivatives (p. 349). 

Two different access routes are used, whether the leaving group is carried on thiazolium derivatives such as anilinovinyl (method A), acetanilidovinyl (method B), formyl methylene, or thioformylmethylene or on the ketomethylene compound (method C). The use of acid anhydride together with pyridine has been patented (method E). 

The chemistry of the carbonyl group is probably the single most important aspect of organic chemical reactivity Classes of compounds that contain the carbonyl group include many derived from carboxylic acids (acyl chlorides acid anhydrides esters and amides) as well as the two related classes discussed m this chapter aldehydes and ketones... 

The chemistry of carboxylic acids is the central theme of this chapter The impor tance of carboxylic acids is magnified when we realize that they are the parent com pounds of a large group of derivatives that includes acyl chlorides acid anhydrides esters and amides Those classes of compounds will be discussed m Chapter 20 Together this chapter and the next tell the story of some of the most fundamental struc tural types and functional group transformations m organic and biological chemistry... 

After acyl halides acid anhydrides are the most reactive carboxylic acid derivatives Three of them acetic anhydride phthahc anhydride and maleic anhydride are mdus trial chemicals and are encountered far more often than others Phthahc anhydride and maleic anhydride have their anhydride function incorporated into a nng and are referred to as cyclic anhydrides... 

Conversions of acid anhydrides to other carboxylic acid derivatives are illustrated m Table 20 2 Because a more highly stabilized carbonyl group must result m order for nucleophilic acyl substitution to be effective acid anhydrides are readily converted to carboxylic acids esters and amides but not to acyl chlorides... 

Conversion of Acid Anhydrides to Other Carboxylic Acid Derivatives... 

The carbonyl group of an amide is stabilized to a greater extent than that of an acyl chlo ride acid anhydride or ester amides are formed rapidly and m high yield from each of these carboxylic acid derivatives... 

This chapter concerns the preparation and reactions of acyl chlorides acid anhydrides thioesters esters amides and nitriles These com pounds are generally classified as carboxylic acid derivatives and their nomenclature is based on that of carboxylic acids... 

ANALGESICS,ANTIPYRETICS,ANDANTIINFLAL 4ATORY AGENTS] (Vol 2) -from acetic anhydride [ACETIC ACID AND DERIVATIVES - ANHYDRIDE] (Vol 1)... 

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