Mixed carboxylates

The addition of nickel formate to magnesium formate significantly reduced the decomposition temperature [1151]. The acceleratory period characteristic of the decomposition of pure Mg(HC02)2 was eliminated and the value of E was substantially diminished. For the double (Zn,Ba) and (Cu,Ba) formates, the rate of decomposition [1152] of the less stable component (Zn or Cu) was slower and that of the more stable component (Ba) more rapid than the values characteristic of pure preparations of these substances. 

Decompositions of oxalates containing the strongly electropositive metals yield an oxide product but the more noble elements yield the metal. Discussion of the mechanisms of these reactions and, in particular, whether metal formation necessarily involves the intermediate production of oxide which is subsequently reduced by CO has been extended to consideration of the kinetics of pyrolysis of the mixed oxalates [32]. 

Kadlec and Rosmusova [1153] believe that both Ni and Co oxalates initially yield product oxide and that the proportion of metal increases with a. Since nickel oxalate decomposes at temperatures 60 K lower than those for CoC204, even a small proportion of Ni2+ markedly increases the rate of decomposition of cobalt oxalate. The effect was attributed to the catalytic properties of the preferentially formed Ni metal. The a—time curves were generally sigmoid and showed only slight deviations in shape with changes in the Ni Co ratio. In the decomposition of a mechanical 

Guslev et al. [1155] confirm the increase in stability of (Ni,Mg) oxalates with increase in magnesium content. These workers suggest that the impurity cation in the solid solution (i.e. that which is present at the lower concentration) disturbs the symmetry of the oxalate ion, so promoting its breakdown. 

Decomposition rates of (Ni,Co) mellitates [1110] increase with increase in nickel content. The a—time curves for the pure components and the mixed mellitates were deceleratory throughout and there was no discontinuity in shape with changes in composition. Rates of decomposition of the solid solutions were appreciably greater than those expected from the decomposition of the individual components present (Fig. 19). The values of E determined for the initial stages of the decomposition of mixtures were close to that found for the nickel salt (184 kJ mole 1) and in the latter stages tended to increase towards that for cobalt mellitate (251 kJ mole-1). Values of A showed a systematic decrease with increase in cobalt content. 

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The synthesis of (+)-N-methylmaysenine, a preliminary for the later synthesis of the antitumor agent maytansine, was accomplished by the joining of fragments A and B, chain extension and macrolactam closure using a mixed carboxylic-sulfonic acid anhydride. 

These authors suggest that the reaction may proceed through the formation of their mixed anhydrides , and illustrate a metal ion templated, mixed carboxylic-sulfonic anhydride. 

As shown in Figure 16.10, this reaction mechanism involves nucleophilic attack by —SH on the substrate glyceraldehyde-3-P to form a covalent acylcysteine (or hemithioaeetal) intermediate. Hydride transfer to NAD generates a thioester intermediate. Nucleophilic attack by phosphate yields the desired mixed carboxylic-phosphoric anhydride product, 1,3-bisphosphoglycerate. Several examples of covalent catalysis will be discussed in detail in later chapters. 

Like all anhydrides (Section 21.5), the mixed carboxylic-phosphoric anhydride is a reactive substrate in nucleophilic acyl (or phosphoryl) substitution reactions. Reaction of 1,3-bisphosphoglycerate with ADR occurs in step 7 by substitution on phosphorus, resulting in transfer of a phosphate group to ADP and giving ATP plus 3-phosphoglycerate. The process is catalyzed by phospho-gjvcerate kinase and requires Mg2+ as cofactor. Together, steps 6 and 7 accomplish the oxidation of an aldehyde to a carboxylic acid. 

Sulfur compounds have also been widely studied as activating agents for polyesterification reactions. p-Toluenesulfonyl chloride (tosyl chloride) reacts with DMF in pyridine to form a Vilsmeir adduct which easily reacts with carboxylic acids at 100-120° C, giving highly reactive mixed carboxylic-sulfonic anhydrides.312 The reaction is efficient both for aromatic dicarboxylic acid-bisphenol312 and hydroxybenzoic acid314 polyesterifications (Scheme 2.31). The formation of phenyl tosylates as significant side products of this reaction has been reported.315... 

Another useful reagent for amide formation is compound 1, known as BOP-C1,141 which also proceeds by formation of a mixed carboxylic phosphoric anhydride. 

Scheme 19 Selective acyl transfer in reductive hydroacylations involving mixed carboxylic anhydrides derived from pivalic acid...

Phenylcyclopentanecarboxylic acid, with ethyl chlorocar-bonate to give mixed carboxylic-carbonic anhydride, 51, 48... 

Curtius reaction, modification using mixed carboxylic-... 

Sodium, with l-bromo-3-chloro-cyclobutane to give bicyclo [l.l.O]butane, 51, 55 Sodium amalgam, 50, 50, 51 Sodium amide, with 2,4-pentane-dione and diphenyliodonium chloride to give l-phenyl-2, 4-pentanedione, 51, 128 Sodium azide, 50, 107 with mixed carboxylic-carbonic anhydrides, 51, 49 Sodium borohydride, reduction of erythro-3-methanesulfony-loxy-2-butyl cyclobutanecar-boxylate, 51, 12 reduction of 2-(1-phenylcyclo-pentyl)-4,4,6-trimethyl-5,6-dihydro-1,3(4H)-oxazine to 2-(1-phenylcyclopentyl)-4,4, 6-trimethyltetrahydro-l,3-oxazine, 51, 25 Sodium cyanoborohydride, used... 

FMF Chen, M Slebioda, NL Benoiton. Mixed carboxylic-carbonic acid anhydrides of acylamino acids and peptides as a convenient source of 2,4-dialky 1 -5(AH)-oxazo-lones. Int J Pept Prot Res 31, 339, 1988. 

A variant that eliminates the production of water and that has proved effective for esterification of hydroxy and aromatic amino acids involves the use of thionyl chloride instead of acid. At a low temperature, the alcohol reacts with the chloride, generating methyl sulfinyl chloride, which produces the ester, probably through the mixed carboxylic acid-sulfinic acid anhydride (Figure 3.18, B). p-Toluenesulfonyl chloride added to the acid and benzyl alcohol serves the same purpose in the preparation of benzyl esters. 

S Kim, JL Lee, YC Kim. A simple and mild esterification method for carboxylic acids using the mixed carboxylic-carbonic anhydrides. J Org Chem 50, 560, 1985. 

DS Tarbell, EJ Longosz. Thermal decomposition of mixed carboxylic-carbonic anhydrides. Factors affecting ester formation. J Org Chem 24, 774, 1959. 

Amine oxides, anhydrous, SO, 55, 58 Amines, protecting group for, 50,12 AMINES FROM MIXED CARBOXYLIC-CARBONIC ANHYDRIDES 1-PHENYLCYCLOPENTYL-AMINE,51,4S... 

Cuprous oxide, in thiol arylation, 50, 75 Curtius reaction, modiflcation using mixed carboxylic-carbonic aidiy-drides, 51, 51... 

Bis alkanoyl amino-2,4,6-triiodobenzyl esters Nanoparticulate diagnostic mixed carboxylic anhydrides... 

It has been possible to substitute the axial carboxylates with a different carboxylate to form the mixed-carboxylate complexes [Mni20i2(02CCFICl2)8(02CCFl2Bu )8(Fl20)3] (67) and... 

There have been efforts to form aromatic polyamides directly from diacids at moderate temperatures by using various phosphorus compounds for in situ activation of the carboxyl groups [Arai et al., 1985 Higashi and Kohayashi, 1989 Krigbaum et al., 1985]. A useful agent is diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate, which probably activates the carboxyl group by forming a mixed carboxylic-phosphoric anhydride [Ueda, 1999 Ueda et al., 1991]. 

AMINES FROM MIXED CARBOXYLIC-CARBONIC ANHYDRIDES ... 

Alenylacetylenes, 50,101 Aluminum chloride, with ethylene and p-methoxyphenylacetyl chloride to give 6-methoxy-/3-tetralone, 51,109 with propylene and acetyl chloride to give 4-chloropentan-2-one, 51,116 Amine oxides, anhydrous, 50, 55, 58 Amines, protecting group for, 50,12 AMINES FROM MIXED CARBOXYLIC-CARBONIC ANHYDRIDES 1-PHENYLCYCLOPENTYLAMINE,... 

Phenylcyclopentylamine has also been prepared from 1-phenylcyclopentanecarboxylic acid by means of the Hofmann degradation of the intermediate amide4 6 and from the intermediate carboxylic acid chloride by the Curtius reaction.6 In the method described, using the mixed carboxylic-carbonic anhydride,7 improved yields of the amine are obtained. 

The usual procedure of preparing acid azides, which involves treating an acid chloride with sodium azide,8,9 suffers from the disadvantage that it is often difficult to obtain pure acid chlorides in good yields from acids which either decompose or undergo isomerization in the presence of mineral acids.7 Synthesis of the azide by way of the ester and hydrazide10 has been used to circumvent this difficulty but is much less convenient. The present procedure permits ready formation of acid azides in excellent yields from mixed carboxylic-carbonic anhydrides and sodium azide under very mild conditions. 

Proton acids can be used as catalysts when the reagent is a carboxylic acid. The mixed carboxylic sulfonic anhydrides RCOOSO2CF3 are extremely reactive acylating agents and can smoothly acylate benzene without a catalyst.265 With active substrates (e.g., aryl ethers, fused-ring systems, thiophenes), Friedel-Crafts acylation can be carried out with very small amounts of catalyst, often just a trace, or even sometimes with no catalyst at all. Ferric chloride, iodine, zinc chloride, and iron are the most common catalysts when the reactions is carried out in this manner.266... 

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