Lead acetate Malonic acid

The decomposition pathways of DBNPA described by Exner et al. (1973) are shown in Figure 21. Hydrolysis ends with oxalic acid which oxidizes slowly to CO2. The reaction of DBNPA with nucleophiles leads to malonic acid, which is just as oxalic acid a naturally occurring dicarboxylic acid it may further degrade to acetic acid and CO2. 

Raney nickel desulfurization has been applied especially to the synthesis of different kinds of amino acids. a-Amino acids have been prepared by the Strecker synthesis of substituted thiophenealdehydes, followed by desulfurization of the thiophene a-amino acids. a-Amino-n-enantic acid, a-amino-n-caprylic acid, and norleucin have been obtained in about 50% yield from the appropriate thiophene aldehydes. From the desulfurization of thiophene -amino acids, obtained from the reaction of thiophenealdehydes with malonic acid in ammonia, aliphatic j8-amino acids, isolated as acetates, have been obtained in high yields. The desulfurization of 3-nitrothiophenes, such as (232), in ammonia leads to y-substituted amino acids (233). ... 

The acid chlorides have served as useful synthetic intermediates leading to ketones via the malonic acid synthesis and Friedel rafts reaction, thiadiazole acetic acid derivatives, and halo ketones via the Arndt Eistert synthesis and carbinols by hydride reduction <68AHC(9)107>. The dialkylcadmium conversion of acid chlorides into ketones fails in the 1,2,5-thiadiazole series. The major product is either a tertiary carbinol or the corresponding dehydration product, by virtue of the high reactivity of the intermediate ketone. 

Also, research on the use of UV/H202 system to treat NOM has been carried out [192-194], Backlund [192] carried out the oxidation of an aquatic humic material with a 254-nm UV lamp in the presence and absence of hydrogen peroxide. He reported significant increases in the humic removal rate with the combined system. He noticed the destruction of macromolecules to yield smaller fragments and identified some compounds such as oxalic acid, acetic acid, malonic acid, etc., which accounted for 20% and 80% of the NOM in UV and UV/H202 systems. Also, he observed that these processes do not lead to any mutagenic activity in the treated water. 

Figure 13.39 shows that malonic ester syntheses can also lead to acetic acid derivatives with a heteroatom in the a-position. The benzylation of (acetamido)malonic acid diethyl ester... 

Previous work on this reaction has included the use of triethanolamine as catalyst, as well as triethylamine as catalyst and solvent. [21-24] The use of elevated temperatures (>75°C) can lead to uncontrolled decarboxylation of malonic acid before condensation, giving acetic acid, which is then too weak a carbon acid to condense. This difficulty means that often up to 3 equivalents of the malonic acid need to be used to achieve good conversion. Our aim in this work was therefore to find a catalyst which would cause the condensation to occur efficiently, but at low enough temperatures to avoid decomposition of the malonic acid. Using THF as solvent and a 1 1 ratio of malonic acid to aldehyde, with 15g of catalyst per mole of reagent, we obtained high levels of conversion of aldehyde in a reasonable time (Table 3). 

Olefinic esters may be obtained directly by the Knoevenagel reaction. Alkyl hydrogen malonates are used in place of malonic acid. Decarboxylation then gives the ester directly as in the preparation of ethyl 2-heptenoate (78%) and methyl m-nitrocinnamate (87%). Alkyl hydrogen malonates are readily available by partial hydrolysis of dialkyl malonates. The use of malonic ester in the condensation leads to olefinic diesters, namely, alkylidenemalonates such as ethyl heptylidenemalonate (68%). A small amount of organic acid is added to the amine catalyst since the salts rather than the free amines have been shown to be the catalysts in condensations of this type. Various catalysts have been studied in the preparation of diethyl methylenemalonate. Increased yields are obtained in the presence of copper salts. Trimethylacetalde-hyde and malonic ester are condensed by acetic anhydride and zinc chloride. Acetic anhydride is also used for the condensation of furfural and malonic ester to furfurylidenemalonic ester (82%). ... 

Malonic acid, ethyl malonate, and their monoalkyl derivatives can be readily halogenated in ether solution subsequent decarboxylation leads to the corresponding a-halogenated acetic acid in 55-80% yield. The reaction of the potassium salts of monoethyl alkylmalonates with bromine provides the a-bromo esters directly, although the yields ate relatively low. ... 

The so-called acetate-malonate pathway leads to three different kinds of natiu al products depending on the detailed pathway followed. Fatty acids result from a reductive pathway to be described here, but acetate and malonate are also precursors for the isoprenoids (terpenes and sterols) produced via mevalonic acid (Ce) and... 

Tetrone derivative (331) is one of the products of decomposition of (330) which takes place when this reactive intermediate is generated in situ and then the solution is left at room temperature. Diethyl malonic acid and pyrazole derivative (332) are additional products of this decomposition. Pyrazole derivative (332) treated with acetic anhydride provides tetrone derivative (331) <69JOC3l8l>. Species (334), similar to (330), is supposed to be an intermediate in the treatment of chloro-pyrazolinone (333) with a base leading to a mixture of corresponding bimanes (185) and (335)... 

Suppl. 67). Laboratory fires have been reported, cansed by contact of moisture with a potassium bromate, malonic acid, and cerinm ammoninm nitrate mixtnre, setting a high exothermic reaction (Bartmess et al. 1998). Bromates ignite when mixed with concentrated mineral acids, lead acetate, or phospho-ninm iodide, PH4I. Finely divided mixtures of bromates with finely divided metals, phosphorus, sulfur, or metal sulfides can explode when heated or subjected to friction (Mellor 1946). 

Historically, simple phenolic acids have been the most frequently identified allelopathic agents (see literature reviews by Rice 1974, 1979, 1983, 1984, 1986). One would assume this was partly because of the fact that the necessary technology to isolate, identify, and quantify phenolic acids, even though crude in the early days, was readily available to most researchers. Furthermore, simple phenolic acids, such as the benzoic acid and cinnamic acid derivatives serve a variety of plant and ecosystem functions and are widespread in higher plants (Fig. 2.4 Bates-Smith 1956 Harborne 1982,1990 Goodwin and Mercer 1983 Siqueira et al. 1991). The ubiquitous distribution in nature and their apparent rapid turnover rates in soils, however, have lead to some controversy as to the importance of phenolic acids in plant-plant allelopathic interactions (Schmidt 1988 Schmidt and Ley 1999 Blum 2004, 2006). Finally, the behavior of phenolic acids in soil systems are somewhat similar to the behavior of a whole host of other organic acids (e.g., acetic acid, butyric acid, citric acid, formic acid, fiimaric acid, lactic acid, malonic acid, tannic acids and tartaric... 

The acetate-malonate pathway of biosynthesis leads, through simple variants, to three major categories of natural products fatty acids by a reductive pathway, isoprenoids via mevalonate, and phenols by cyclisation of polyketides. 

The use of malonyl-CoA for carbon chain synthesis appeared to be especially attractive from the thermodynamic point of view. The condensation of acyl-CoA with a thiolester of malonic acid leads to the same jS-ketoacyl derivative as with the thiolester of acetic acid, but in this case the simultaneous liberation of CO2 [equation (4)] shifts the equilibrium toward synthesis. 

The biosynthesis of the skeletons of many natural products by head to tail linkage of acetate-malonate units is firmly estabhshed (Birch, 1962 Richards and Hendrickson, 1964). Two possible mechanisms (see Fig. 1) for the cyclization of the intermediate linear S-polyketomethylene chain have been discussed. Acetylphloroglucinol (Fig. 1, VII) and orsellinic acid (Fig. 1, VI) can be derived by internal Claisen and aldol condensation respectively of 3)5,7-trioxooctanoic acid, probably as its coenz3mie-A ester. The alternative aldol condensation leads to 3>5 dihydroxyphenylacetic acid (Fig. 1, V). Considerable academic interest in the biosynthesis of griseofulvin arises from the observation that its formation from a linear polyketomethylene chain of seven acetate-malonate units could involve both types of condensation. 

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

Treatment of compound 270 with 1 equiv of ethoxymethylene malonate provides 271 and heating with acetic acid leads to the cyclized product 133 (Scheme 34) <2003MI1>. 

Acetogenins. Acetogenins are produced upon chain elongation with activated acetate units (or malonate followed by loss of carbon dioxide). A simplified sketch of this sequence is given in Fig. 1. During the first steps, a Claisen-type condensation of two acyl precursors yields a (3-ketoacyl intermediate A. Upon reduction to B and dehydration to C, followed by hydrogenation to D and hydrolysis, the chain elongated fatty acid E is produced. The next cycle will add another two carbons to the chain. Similarly, a reversed sequence leads to chain... 

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