Carbonic acid anhydrides cyclic

Where acid chlorides are difficult to obtain, Weinstock s method of using mixed carboxylic-carbonic acid anhydrides can be helpful. The acid to be converted into its azide is treated with ethyl chlorofor-mate and base, the ethyl carbonate moiety is then displaced by azide ion. The method has been used in the penicillin field . It is not general, however when the alkanoyl part of the mixed anhydride is sterically hindered, the azide ion displaces it instead of the carbonate moiety, and ethyl azidoformate is produced Cyclic anhydrides can be opened by azide ion, to give the salts of omega-azidocarbonyl acids, such as Na+ "OOCCHaCHaCONa . 

In this short section, cyclic compounds are discussed that are not strictly lactones since they contain an endocyclic structural motif of the type -O-CO-X- or -X-O-CO-. However, these compounds share with lactones the possibility to be hydrolyzed at the endocyclic -CO-O- bond. This is the case for cyclic diesters of carbonic acid (-O-CO-O-), cyclic esters of car-bamic acid (-0-C0-NH-), and cyclic anhydrides (-C0-0-C0-). One example of each class is presented here. 

Lenchs anhydride Cyclic anhydride that decomposes to carbon dioxide and an amino acid. 

Potassium carboxylate groups introduced onto the surface of carbon fibers initiated anionic polymerization of epoxides (e.g., styrene oxide, epichlorohydrin, and glycidyl phenyl ethers) and cyclic acid anhydrides (e.g., maleic anhydride, succinic anhydride, and phthalic anhydride) in the presence of 18-crown-6 [41]. 

The known adduct (385) of furan and vinylene carbonate, previously used for the synthesis of some cyclitols,256,257 has been transformed into DL-ribose derivatives. After hydroxylation of 385 and subsequent formation of the isopropylidene derivative, the carbonate group was removed by treatment with barium hydroxide, and the resulting diol was cleaved by oxidation with permanganate. Dicarboxyl-ic acid 386 gave, upon treatment with acetic anhydride, cyclic anhydride 387. The reaction of 387 with azidotrimethylsilane produced... 

Another type of elimination reaction favoured under plasma conditions is the decarboxylation. Carbocyclic acids easily lose carbon dioxide to form the parent hydrocarbons. In acid anhydrides decarboxylation is followed by a decar-bonylation. Cyclic or bicyclic anhydrides fragment forming unsaturated compounds, a reaction which has been studied with phthalie anhydride 24>. This anhydride decomposes to dehydrobenzene which, in the absence of other compounds, dimerizes, trimerizes or polymerizes. Orientation experiments indicated similar results for aliphatic acid anhydrides. 

Coordination polymerisation of heterocyclic monomers comprises polymerisation and copolymerisation processes of such monomers as oxacyclic monomers, especially epoxides [2,61-71], thiacyclic monomers like episulphides [72-76], azacyclic monomers [77,78] and phosphacyclic monomers [79]. Monomers with an exocyclic oxygen atom, such as cyclic esters like lactones [80-90] and lactide [90-92], cyclic acid anhydrides [93-98], cyclic carbonates [99,100] and related monomers, belong to oxacyclic monomers undergoing coordination polymerisation or copolymerisation. 

Since oxiranes are representative heterocyclic monomers containing an endo-cyclic heteroatom, and the most commonly polymerised of such monomers, they have been subjected to copolymerisations with heterocyclic monomers containing both an endocyclic and an exocyclic heteroatom. Coordination copolymerisations of heterocyclic monomers with different functions are focused on oxirane copolymerisation with cyclic dicarboxylic acid anhydride and cyclic carbonate. However, the statistical copolymerisation of heterocyclic monomers with an endocyclic heteroatom and monomers with both endocyclic and exocyclic heteroatoms have only a limited importance. Also, the block copolymerisation of oxirane with lactone or cyclic dicarboxylic acid anhydride is of interest both from the synthetic and from the mechanistic point of view. Block copolymerisation deserves special interest in terms of the exceptionally wide potential utility of block copolymers obtained from comonomers with various functions. It should be noted, however, that the variety of comonomers that might be subjected to a random, alternating and block polymerisation involving a nucleophilic attack on the coordinating monomer is rather small. 

Although rather scant information concerning the structure of active sites in the above copolymerisation systems is available [183-189], cyclic acid anhydrides can be considered as coordinating to metal species via the carbonyl oxygen atom and reacting by nucleophilic attack of the metal substituent on the carbon atom of the coordinated carbonyl group [190,191], Thus, the oxi-rane/cyclic acid anhydride copolymerisation pathway may be presented schematically as follows [82] ... 

Diethanolamine will react with acids, acid anhydrides, acid chlorides, and esters to form amide derivatives, and with propylene carbonate or other cyclic carbonates to give the corresponding carbonates. As a secondary amine, diethanolamine reacts with aldehydes and ketones to yield aldimines and ketimines. Diethanolamine also reacts with copper to form complex salts. Discoloration and precipitation will take place in the presence of salts of heavy metals. 

Only half of the anhydride appears in the acyl product the other half forntSva carboxylic acid. A cyclic anhydride, we see, undergoes exactly the same reactions as any other anhydride. However, since both halves of the anhydride are attached to each other by carbon-carbon bonds, the acyl compound and the carboxylic acid formed will have to be part of the same molecule. Cyclic anhydrides... 

Phosgenation of a-hydroxy acids affords cyclic mixed carboxylic-carbonic anhydrides which can be used as activated form of acid function in reaction with amines to afford amides as illustrated by the example given in scheme 182 (Ref. 235). 

Phosgene is reported to combine with a wide range of oxygenated materials, including alcohols, ethers, ketones, carboxylic acids, anhydrides, lactones, esters, carbonic acid derivatives, etc. Only the reactions of COCIF with alcohols, phenols and cyclic ethers have been reported, resulting usually in the generation of fluoroformates. Such materials can often be usefully converted into the corresponding fluoro compound by means of decarboxylation in the presence of BF3, EtjO, pyridine, or other materials. 

Reduction of cyclic anhydrides. Although acid anhydrides are reduced to only a slight extent by sodium borohydride, cyclic anhydrides are reduced to 8- and y-lactones in 51-97% yield. Hydride attack occurs principally at the carbonyl group adjacent to the more highly substituted carbon atom.7... 

A carbonyl group is a carbon double-bonded to an oxygen an acyl group is a carbonyl group attached to an alkyl or aryl group. Acyl halides, acid anhydrides, esters, and amides are called carboxylic acid derivatives because they differ from a carboxylic acid only in the nature of the group that has replaced the OH group of the carboxylic acid. Cyclic esters are called lactones cyclic amides are lactams. There are symmetrical anhydrides and mixed anhydrides. 

Anhydrides and cyclic carbonates. Symmetrical anhydrides are formed when acids are treated with (Cl jCOlaCO and Et3N. The transformation of the terminal glycol unit of a 1,2,3-triol to the cyclic carbonate can be accomplished with triphosgene and pyridine on the other hand, the internal diol system is protected using NaH and (MeO)2CO. 

Anionic polymerizations can be terminated by addition of another molecule, which will introduce an co-functional group in the chain. Excess carbon dioxide or cyclic anhydrides lead to terminal carboxylic groups, whereas addition of excess phosgene produces an acid chloride function. Similarly, isocyanates generate coamide functions, and lactones yield co-hydroxyl groups. 

A phenyl-substituted cyclic silyl enolate is synthesized from 1,1-dimethylsilacyclobutane and benzoyl chloride in the presence of a stoichiometric amount of triethylamine and a catalytic amount of PdCl2(PhCN)2 (eq 8). In the case of aliphatic acid chlorides, the use of diisopropylamine instead of triethylamine gives better results. A platinum complex, Pt(CH2=CH2)(PPh3)2, also mediates the reaction although its performance is inferior to that of palladium complexes. Acid anhydrides or combinations of organic halides and carbon monoxide are alternatives to acid chlorides. In the case of acid anhydrides, the amine is not necessary for the reaction. 

Control of moleculair weight in polymerization reaction is a central subject of synthetic polymer chemistry in fundamental as well as practical aspects. We have developed metsdloporphyrins such as 1 and 2 as excellent initiator for living pol3mierizations of a variety of cyclic and vinyl monomers such as epoxides episulfides, lactones, methacrylates, acrylates, and methacrylonitrile, and also for living cdtemating copolymerization of epoxide ind carbon dioxide " or cyclic acid anhydride . ... 

---