Malonate ions, formation

Irradiation accelerates the reactions of Scheme 4.1, and the substitution products are formed in 70-80% yields. Acceptors of radicals (e.g., di-tert-butylnitroxyl) or electrons (e.g., m-dinitro-benzene [DNB]) completely inhibit the snbstitution even if the acceptors are added to the reaction mixture in small amonnts. The mentioned snbstitution reactions do not take place when no cyano groups are present in the initial a-phenylsnlphonyl cumene. Hence, the cyano groups send the reaction via the ion-radical pathway. Like the nitro gronp, the cyano group promotes the formation of anion-radical, which originates on one-electron transfer from the thiophenolate or malonate ions to the substrate. 

Nitrosylcarbonyhron complexes, [Fe(CO)3(NO)] and Fe(CO)2(NO)2, are capable of catalyzing the substitution of allyhc chlorides, formates, acetates, and carbonates by malonate ion. The attack on substituted substrates goes with retention of double bond stereochemistry, with high retention of stereochemistry at the substituted carbon atom, and with... 

The highest value of feMA is obtained for M"+ = Cu2+. Less active catalysts than Cu2+ are the ions Ni2+, Zn2+ and Co2+. The sequence of the catalytic powers of the metal ions is identical with that found by Irving and Williams [268] for the equilibrium constants of complex formation. There is a linear relationship between log feMA and log i Mmaionate the logarithm of the complex formation constant of Mn+ with malonate ion. 

The following sequence of dipositive metal ions shows a decreasing effect on the rate of decarboxylation of oxaloacetic acid Cu(II), Zn(II), Co(II), Ni(II), Mn(II), Cu(II) (91). The rate constants for these decarboxylations approximately parallel the formation constants of the corresponding metal oxalates. A similar result was found in the decarboxylation of acetonedicarboxylic acid in the presence of certain transition metal ions the decarboxylation rates paralleled the formation constants of the metal malonates (170). These parallelisms indicate that the effectiveness of a metal ion in these decarboxylation reactions depends on its ability to chelate with the oxalate ion and the malonate ion, which resemble the transition states of the oxaloacetic and acetonedicarboxylic acids, respectively. 

Other Reactions of Unsaturated Steroids.—A review on organopalladium intermediates includes several steroidal examples. A mechanistic study of the formation of the 7r-allyl palladium complex (65) from the corresponding 3-oxocholest-4-ene led to the conclusion that initial 7r-complexing was rate limiting. Reactions of a series of similar ir-allyl palladium complexes (66)—(68) with dialkyl malonate ion gave the 3-oxo-A -6/S-yl malonates (69)—(71) respec-... 

The mechanism for 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)-mediated oxidative C—C bond formation has been supported by characterization of a trapped intermediate iminium ion (using X-ray crystallography, elemental analysis, and solid-state NMR spectroscopy), which has been shown to react with a range of nucleophiles including a malonate ion ... 

Co(NH3)50xH]2+,S04. Base hydrolysis of [Co(NH3)sOx]+ is not affected by OAc, but the rate of reaction is retarded by other ions in the order C032"complex formation with the unco-ordinated carboxylate group ... 

Multidentate Leaving Groups.—Very few reports have appeared for this class of reaction. Dicarboxylato-complexes of the type [Cofox) - or [Co(mal)3] (ox = oxalate ion, mal = malonate ion) continue to receive attention. Acid-catalysed decomposition of these complex ions is believed to occur concurrently with redox reactions involving the formation of organic radicals, e.g. [Co(ox)3] -> Co +(aq) + ox + 2ox. Ignoring a previous study of [Co(mal)3] in which an analogous... 

The use of CI3CCO2" ion as a catalyst for the formation of [CrfacacHla) is recommended. [Cr(acacH)2(02CCCl3)(H20)] was isolated as an intermediate in this reaction. Although many other carboxylate ions catalyse the formation of (Cr-(acacH)3l, oxalate and malonate ions are deactivators. ... 

Multidentate Leaving Groups.—The hydrolysis of [Co(ox)a] - and of [Co(ox)2(OH2)2], which ultimately produces cobalt(n) and carbon dioxide, involves the formation of an intermediate containing a unidentate oxalate ligand previous to the rate-determining step. Free radical intermediates are thought unlikely in the decomposition of these oxalato-complexes, but malonate ion-radicals are thought to be intermediates both in the thermal and photochemical hydrolysis of the [Co(mal)3] anion. Kinetics are reported for a third example of these aquation-redox processes, [Co(acac)2] in acidic solution. ... 

The complexes formed by oxalic and malonic acids have been carefully studied and the detailed structural features have been obtained from X-ray diffraction measurements (Hansson, I973e). The oxalate ions in these complexes serve as bridging ligands and the larger metal ions have coordination number nine whereas the smaller ions have coordination number eight. The malonate ions in the rare earth malonates are of two different types, those that are involved in six-membered chelate ring formation and those which are not. 

In 1994, Kawara and Taguchi reported on the apphca-tion of the chiral alkyl quaternary ammonium salt derived from Z>-prohne in the asymmetric Michael addition of malonate to cychc enone. The enone moiety was activated via electrophilic iminium ion formation. The results indicated that the facial selectivity of enone at the time of... 

Reaction of chloroacetic acid with cyanide ion yields cyanoacetic acid [372-09-8] C2H2NO2, (8) which is used in the formation of coumarin, malonic acid and esters, and barbiturates. Reaction of chloroacetic acid with hydroxide results in the formation of glycoUc acid [79-14-1]. 

MnP is the most commonly widespread of the class II peroxidases [72, 73], It catalyzes a PLC -dependent oxidation of Mn2+ to Mn3+. The catalytic cycle is initiated by binding of H2O2 or an organic peroxide to the native ferric enzyme and formation of an iron-peroxide complex the Mn3+ ions finally produced after subsequent electron transfers are stabilized via chelation with organic acids like oxalate, malonate, malate, tartrate or lactate [74], The chelates of Mn3+ with carboxylic acids cause one-electron oxidation of various substrates thus, chelates and carboxylic acids can react with each other to form alkyl radicals, which after several reactions result in the production of other radicals. These final radicals are the source of autocataly tic ally produced peroxides and are used by MnP in the absence of H2O2. The versatile oxidative capacity of MnP is apparently due to the chelated Mn3+ ions, which act as diffusible redox-mediator and attacking, non-specifically, phenolic compounds such as biopolymers, milled wood, humic substances and several xenobiotics [72, 75, 76]. 

Fig. 3.46. High-performance ion chromatographic analysis of C.I. Reactive yellow 84 after 120 min of the catalytic oxidation over Fe-Y80 catalyst. Initial conditions were 100 mg/1 azo-dye, pH 5, t = 50°C, catalyst concentration 1 g/1 and 20 mmol H202. Peak identities are as follows 1, acetate 2, formate 3, chloride (used for pH adjusting) 4, nitrate 5, malonate 6, sulphate 7, oxalate. Reprinted with permission from M. Neamtu et al. [121].

Various transition metals have been used in redox processes. For example, tandem sequences of cyclization have been initiated from malonate enolates by electron-transfer-induced oxidation with ferricenium ion Cp2pe+ (51) followed by cyclization and either radical or cationic termination (Scheme 41). ° Titanium, in the form of Cp2TiPh, has been used to initiate reductive radical cyclizations to give y- and 5-cyano esters in a 5- or 6-exo manner, respectively (Scheme 42). The Ti(III) reagent coordinates both to the C=0 and CN groups and cyclization proceeds irreversibly without formation of iminyl radical intermediates.The oxidation of benzylic and allylic alcohols in a two-phase system in the presence of r-butyl hydroperoxide, a copper catalyst, and a phase-transfer catalyst has been examined. The reactions were shown to proceed via a heterolytic mechanism however, the oxidations of related active methylene compounds (without the alcohol functionality) were determined to be free-radical processes. 

In other work, solution complex formation of the pendant-arm ligands 1,4,10,13-tetraoxoa-7,16-diazacyclooctadecane-7-malonate and 1,4,10,13-tetraoxoa-7,16-diazacyclooctadecane-7,16-bis(malonate) has been investigated with a range of both transition and nontransition metal ions the 1 1 manganese(II) complexes of these species have been reported to show stabilities (log Ai values) of 7.41 and 5.60, respectively, in water (7=0.15, 25°C). 

Diethyl malonate has been proposed for use as a proton source in these cyclization reactions [124], It is not a sufficiently strong acid to protonate the radical-anion rapidly. However it irreversibly protonates the enol intermediate generated after carbon-caibon bond formation. In one case, control of stereochemistry in favour of the traHS-sunstituted five membered ring 39 was achieved by the addition of cerium(Ill) ions [124],... 

The use of /i-ketocstcrs and malonic ester enolates has largely been supplanted by the development of the newer procedures based on selective enolate formation that permit direct alkylation of ketone and ester enolates and avoid the hydrolysis and decarboxylation of ketoesters intermediates. Most enolate alkylations are carried out by deprotonating the ketone under conditions that are appropriate for kinetic or thermodynamic control. Enolates can also be prepared from silyl enol ethers and by reduction of enones (see Section 1.3). Alkylation also can be carried out using silyl enol ethers by reaction with fluoride ion.31 Tetraalkylammonium fluoride salts in anhydrous solvents are normally the... 

A typical chemical system is the oxidative decarboxylation of malonic acid catalyzed by cerium ions and bromine, the so-called Zhabotinsky reaction this reaction in a given domain leads to the evolution of sustained oscillations and chemical waves. Furthermore, these states have been observed in a number of enzyme systems. The simplest case is the reaction catalyzed by the enzyme peroxidase. The reaction kinetics display either steady states, bistability, or oscillations. A more complex system is the ubiquitous process of glycolysis catalyzed by a sequence of coordinated enzyme reactions. In a given domain the process readily exhibits continuous oscillations of chemical concentrations and fluxes, which can be recorded by spectroscopic and electrometric techniques. The source of the periodicity is the enzyme phosphofructokinase, which catalyzes the phosphorylation of fructose-6-phosphate by ATP, resulting in the formation of fructose-1,6 biphosphate and ADP. The overall activity of the octameric enzyme is described by an allosteric model with fructose-6-phosphate, ATP, and AMP as controlling ligands. 

Many formation constants involve polycarboxylates Table 28 summarizes the data. Nagyp l and Fabian s report on the oxalic and malonic systems seems the most complete as hydrolysis of both metal ion and complexes has been included.584 A concentration distribution of the complexes in the malonic system is shown in Figure 25. The order of basicities is succinic > citraconic > itaconic > maleic > malonic acid and log /3U0 should follow the same order. However, from Table 28, the order of stabilities is citraconic > malonic > maleic > itaconic > succinic acid.608... 

A related reaction sequence that involves the Michael addition of a coordinated amide ion to an a,0-unsaturated malonate results in the formation of a P-carboxyaspartic acid complex. The acid is isolated as the calcium salt by reduction of cobalt(III) followed by recovery and hydrolysis of the diethyl ester (Scheme 45).215... 

---