Dehydration, dicarboxylic acids

The tropolone alkaloid of Liliaceae species, colchicine, is transformed by acetylation, alkaline cyclization, and dehydration into the tetracyclic pyrrolotropone acetyl anhydrocolchicine [77TL2977 83AX(C)1709]. When the dicarboxylic acid anhydride groups of puberulonic and stipitatonic acids (metabolites of Penicillium species) condense with o-phenylenediamine, another tetracyclic pyrrolotropone structure is formed (51JCS1139 59JCS2847). 

Methyl-3,3 -bipyridine has been oxidized by permanganate to 3,3 -bi-pyridine-4-carboxylic acid. " 3,3 -Bipyridine carboxylic acids are easily decarboxylated and have been esterified and converted to amides, hydrazides, and acylazides. The Hofmann degradation, of the diamide of 3,3 -bipyridine-2,2 -dicarboxylic acid affords the expected 2,2 -diamino-3,3 -bipyridine, but some of the tricyclic system 108 is formed as well. A 2,2 -bis(acylazide) is converted to a similar tricyclic system with ethanol via the intermediate isocyanate, and several related reactions have been described. The simultaneous dehydration... 

Heating dicarboxylic acids, HOOC(CH,) COOH n = 2 or 3), forms cyclic anhydrides by intramolecular dehydration [Problem 16.22(a), (6)]. Anhydrides resemble acid halides in their reactions. Because acetic anhydride reacts less violently, it is often used in place of acetyl chloride. Acid anhydrides can also be used to acylate aromatic rings in electrophilic substitutions. 

Cyclic tetrafluoro ethers are also the main or sole products of the sulfur tctrafluoridc fluorination of phthalic and pyromellitic acids, or their anhydrides, possessing two bulky ortho substituents (e.g., CF3. N02, Br. Cl or even Me). These substituents create steric crowding which pushes two neighboring carboxylic acid groups towards each other and forces cyclization acid anhydrides and difluoro lactones are the intermediates and they may be isolated from reactions carried out under sufficiently mild conditions. Thus, reaction of 3,6-bis(trifluoromcthyl)bcn-zcnc-1,2-dicarboxylic acid (4) with sulfur tctrafluoridc at ambient temperature results in dehydration to give exclusively the corresponding cyclic anhydride 5 at 60"C a mixture of the anhydride 5, 3,6-bis(trifluoromethyl)phthaloyI difluoride (6) and 3,3-difluoro-4,7-bis(trifluoro-methyl)isobenzofuran-l(3//)-one (7) is obtained, but at 200"C the final product, 1,1,3,3-tct-rafluoro-4,7-bis(trifluoromethyl)-l,3-dihydroisobenzofuran (8), is formed as the sole product.137... 

By hydrolysis and dehydration of quinuclidin-3-one cyanhydrin (108), 3-alkoxycarbonyl-Zl2-dehydroquinuclidines (109) were obtained, which can be reduced and saponified to quinuclidine-3-carboxylic acid (110).121,122 Quinuclidine-2,3-dicarboxylic acid (112) was similarly prepared from 2-ethoxycarbonylquinuclidin-3-one cyanohydrin (111).109... 

Acid anhydrides, as their name implies, are formed from the dehydration reaction of two carboxylic acid groups (Fig. 72). Anhydrides are highly reactive toward nucleophiles and are able to acylate a number of the important functional groups of proteins and other macromolecules. Upon nucleophilic attack, the anhydride yields one carboxylic acid for every acylated product. If the anhydride was formed from monocar-boxylic acids, such as acetic anhydride, then the acylation occurs with release of one carboxylate group. However for dicarboxylic acid anhydrides, such as succinic anhydride, upon reaction with a nucleophile the ring structure of the anhydride opens, forming the acylated product modified to contain a newly formed carboxylate group. 

Furan-2,5-dicarboxylic add also has tremendous industrial potential, because it could replace oil-derived diadds such as adipic or terephthalic acid as monomers for polyesters and polyamides [98, 99]. This diadd can be synthesized by Pt-catalyzed oxidation with 02 of 5-hydroxymethylfurfural the latter is obtained by acid-catalyzed dehydration of D-frudose or frudosans (inulin) the latter, however, are too expensive as starting materials, and yields from glucose-based waste raw materials are no higher than 40%. Therefore, the potential attractive option of furan-2,5-dicarboxylic acid will develop only after an effident generation of 5-hydroxymethylfurfural from forestry waste materials has been developed. The same compound is also the starting material for the synthesis of other interesting chemicals obtained by oxidative processes, such as 5-hydroxymethylfuroic add, 5-formylfuran-2-carboxylic add and the 1,6-dialdehyde. 

Malonate and the dianions of the other aliphatic dicarboxylic acids H02 C(CH2 ) CO,H (n = 1-8) have been isolated as crystalline hydrates, and some of these have been dehydrated.293 X-Ray structural analyses have been reported for the malonate dihydrate,294 which has trans H2Os and bridging malonates of type (110), and for the succinate tetrahydrate and adipate dihydrate 295 the succinate reputedly has a trans- fAn02 (H2 0)4 ] polyhedron with bridging dicarboxylate, presumably as in (109). The monoanion of maleic acid (111) is only unidentate in crystalline [Mn(H-maleate)2-(H20)4] 296 but the equivalent compound of phthalic acid is a bis-chelated octahedral [Mn(0,0)2 (H2 0)2] species.297 Clearly other interactions in the solids, as well as the bonding interactions with Mn", define structure in the carboxylate compounds. 

The procedure described is a modification of the directions of Prelog, Frenkiel, Kobelt, and Barman. Cyclodecanone has been prepared by the dehydration of sebacoin followed by catalytic hydrogenation, by the pyrolysis of the thorium or yttrimn salt of nonane-1,9-dicarboxylic acid, and by the ring enlargement of cyclononanone, as well as by the reduction of sebacoin. ... 

Substituted succinic anhydrides, and related anhydrides are formed under acidic conditions. Dicarboxylic acids are dehydrated with acetyl chloride, trifluoroacetic anhydride, or sulfuric acid (hydrolysis of amide and condensation). ... 

Mercurioferrocenes (290) and (291) are separable by Soxhlet extraction and these may be used to prepare bromoferrocene or dibromoferrocene or the iodo analogs. Alternatively, these halogenated ferrocenes are prepared from the ferrocene boronic acids or from anions (322) or (323). Bromoferrocene is the starting material for cyanoferrocene, azidoferrocene, or aminoferrocenes, generally in the presence of a copper salt. Amtnoferrocene can be acylated to produce an amide, or converted to isocyanoferrocene by a formylation/dehydration sequence (Scheme 96). The 1,T-diisocyanoferrocene is available from the bis(acyl)azide, itself derived from ferrocene dicarboxylic acid. ... 

Carboxylic acids cannot be readily converted to anhydrides, but dicarboxylic acids can be converted to cyclic anhydrides by heating to high temperatures. This is a dehydration reaction because a water molecule is lost from the diacid. 

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