Malonic acid cyclic

The 3f/-pyrazole-3,5(4//)-diones (7), prepared by lead tetraacetate,29,30 or tert-butyl hypochlorite31,32 oxidation of malonic acid cyclic hydrazides, are generally less stable than the triazoles 5, and are not isolable. The monocarbonyl derivatives (8-10) have been reported.33-36 The unstable 1,3,4-thiadiazole-2,5-dione (11) has been generated and reacted in situ.31,3 ... 

Meldrum s acid Malonic acid, cyclic isopropylidene ester (8) 1,3-Dioxane-4,6-dione, 2,2-dimethyl- (9) (2033-24-1)... 

Dimethyl-1,3-Dioxane-4,6-dione (Meldrum s Acid) Malonic acid, cyclic isopropylidene ester (8) 1,3-Dioxane-4,6-dione, 2,2-dimethyl- (9) (2033-24-1) Ethylenediammonium diacetate 1,2-Ethanediamine diacetate (9) (38734-69-9) (R)-Citronellal 6-Octenal, 3,7-dimethyl-, (R)-(+)- (8,9) (2385-77-5)... 

MELDRUM S ACID 2,2-DIMETHYL-1,3-DIOXANE-4,6-DIONE MALONIC ACID, CYCLIC ISOPROPYLIDENE ESTER 1,3-DIOXANE-4,6-DIONE, 2,2-DIMETHYL- (2033-24-1), 67, 170 69, 33 p-Mentha-6,8-dien-2-one (6485-40-1), 66, 13... 

Meldrum s acid Malonic acid, cyclic isopropylidene ester (8) ... 

In contrast to other acids, anhydrous hydrogen fluoride does not cause hydroly SIS and decarboxylation of the malonic acid residues in these reactions [5]. It is a good reagent for the cyclization of a-benzamidoacetophenones to 2,5 diphenyl-oxazoles [6] (equation 7) The same reaction with concentrated sulfuric acid gives cyclic product with only a 12% yield [6]... 

These compounds yield, on hydrolysis, the free acids, which, like all acids containing two carbo.xyl groups attached to the same carbon atom, lose COj on heating. Thus, ethyl malonic acid yields butyric acid. In this way the synthesis of monobasic acids may be readily effected. Malonic ester, moreover, may be used in the preparation of cyclic compounds as well as of tetrabasic and also dibasic acids of the malonic acid series ( Perkin). To give one illustration malonic ester, and ethylene bromide in presence of sodium alcoholate, yield triniethyleiic dicarbo.xylic ester and tetramethylene tetracarbo.xylic ester. The first reaction takes place in two steps,... 

Decarboxylation is not a general reaction of carboxylic acids. Rather, it is unique to compounds that have a second carbonyl group two atoms away from the —COoH. That is, only substituted malonic acids and /3-keto acids undergo loss of CC>2 on heating. The decarboxylation reaction occurs by a cyclic mechanism and involves initial formation of an enol, thereby accounting for the need to have a second carbonyl group appropriately positioned. 

Succinates (e.g., dicyclohexyl succinate) Hexafluoropropylene oxide (HFPO) dimers and trimers Fluorochloro compounds having CFC12 Malonic acids C(0)CH2C(0)0CH3 Cyclic sulfides... 

Barbituric acid can be considered as a cyclized malonic acid diamide (malonyl-urea). It is therefore a cyclic diketone that may be classified, in the sense of the compounds discussed in Section 12.6, as a coupling component with a methylene group activated by two carbonyl groups in the a- and a -positions. The reaction with arenediazonium salts was studied by Nesynov and Besprozvannaya (1971). These authors obtained coupling products (in good yield) that they considered to be arylhydrazones. Coupling with 4-(phenylazo)benzenediazonium chloride was studied by Chandra and Thosh (1991). The lH NMR spectra of these compounds are consistent with the arylhydrazone structure 12.68. 

Malonic acid and its derivatives, which would give four-membered cyclic anhydrides, do not give this reaction when heated but undergo decarboxylation (12-38) instead. 

It is noteworthy that the value of this substrate is smaller by one order compared to non-cyclic compounds. According to the discussions proposed above, this is considered to be due to its conformation already being fixed to the one that fits to the binding site of the enzyme. This estimation was demonstrated to be true by the examination of the effect of temperature on the kinetic parameters. Arrhenius plots of the rate constants of indane dicarboxylic acid and phenyl-malonic acid showed that the activation entropies of these substrates are —27.6 and —38.5 calmol K , respectively. The smaller activation entropy for the cyclic compound demonstrates that the 5yn-periplanar conformation of the substrate resembles the one of the transition state. 

Phenylaminomethylenemalonates (444) were prepared in 92-95% yields in the reactions of aniline, ethyl orthoformate, and the appropriate cyclic ester of malonic acid [441, R = R1 = Me, —(CH2)5—] at reflux temperature or 15 min (80CB2630). 

Acylated derivatives of urea are referred to as ureides. Acylation of urea with a monoacid produces acyclic ureides, whereas diacylation with malonic acid (a diacid) yields the cyclic structure of barbiturates. The acyclic ureides carbromal and bromisoval, now outdated hypnotics, can be considered ring-opened analogues of the barbiturates to be examined in the next subsection. 

The chemistry of dicarboxylic acids depends on the value of n. See Problem 16.18 for decarboxylations of oxalic acid (n =0) and malonic acid (n = 1). When n = 2 or 3, the diacid forms cyclic anhydrides when heated. When n exceeds 3, acyclic anhydrides, often polymers, are formed. 

Titanium(IV) chloride is used as the catalyst in a Knoevenagel reaction between various 2,2-disubstituted 3-hydroxypropanals and malonic acid or its esters. The products are substituted dihydropyran-2-ones (536) (79LA751). The reaction, which occurs cleanly and in good yield, utilizes an excess of the titanium halide and is thought to involve a cyclic complex which undergoes an ester exchange to a lactone complex (Scheme 198). 

The 1,3-binucleophilic components of cyclocondensations can react with oc,(3-unsaturated carbonyl compounds containing a CH-acidic reaction center (Scheme 3.1, reaction e). Examples of these are derivatives of malonic acid (mal-ononitrile, malonoamide, cyanoacetic acid, ethyl cyanoacetate, cyanoacetamide, cyanothioacetamide etc,), cyclic monoketones and diketones, and barbituric acid derivatives. 

Fig. 4.13 Cyclic voltammograms of (a) urea/ChCl, (b) ethylene gly-col/ChCl and (c) malonic acid/ChCl ionic liquids. Voltammograms were acquired at room temperature (20°C), using a Pt disk (2 mm diameter) working electrode, a Ag wire reference electrode and a potential scan rate of50mVs 1.

Different cyclic products are formed in the double Michael addition of malonic acid ethyl methyl ester to ( vE)-l,5-diphenylpenta-l,4-dien-3-one under basic conditions. Label the stereogenic units in the reaction products with the appropriate stereodescriptors. 

The treatment of alkenes with iodine(III) reagents usually results in functionalization of the carbon-carbon double bond. However, 1,1-diphenylethylene affords a low yield of (l,l-diphenylethenyl)phenyliodonium tosylate with HTIB (equation 181)11,138. The cyclic dithiolylidene derivative of malonic acid, shown in equation 182, undergoes decarboxylation with [bis(trifiuoroacetoxy)iodo]benzene in methanol and gives an unusual vinyliodo-nium trifluoroacetate139. Finally, when the allenylphosphonate shown in equation 183 is added to a mixture of (difluoroiodo)benzene and BF3-etherate in dichloromethane, a... 

Ozonolysis of ketene dimer gives a very unstable compound that can be observed only at low temperatures (-78 °C or below). It has two carbonyl bands in the IR and reacts with amines to give amides, so it looks like an anhydride (Chapter 12). Can it be the previously unknown cyclic anhydride of malonic acid ... 

Solid phase synthesis of highly substituted thiophene derivatives 15 using a cyclic malonic acid ester resin 14 was also reported. Highly pure thiophene derivatives were reported to have been prepared by this solid phase synthesis <0314851>. While alkyl or aromatic substitutions on the P position to the carbonyl yielded the corresponding 5-alkyl/aryl substituted 2-acyl aminothiophene, acetaldehyde did not produce the corresponding 2,3- disubstituted thiophene. 

Huebner et al. studied the stoichiometry and approximate rates of oxidation of a number of compounds containing an active methylene group. They found that not all such compounds are oxidised by periodate, and that in general one of the activating groups must be -CHO or -COOH for oxidation to occur. Thus diethyl malonate, ethyl acetoacetate, and cyanoacetic acid are not oxidised. Acetylacetone and other acyclic 1,3-diketones are oxidised very slowly, but cyclic 1,3-diketones are readily oxidised (Wolfrom and Bobbitt ). The first step in the oxidation of a compound containing an active methylene group is hydroxylation, then this is followed by further oxidation, e.g. malonic acid and 1,3-cyclohexanedione react as follows... 

The pH dependence may be due to the reactive periodate species being lOJ, but the mechanism of hydroxylation is uncertain. The exceptions noted above show that enolisation cannot be the sole factor determining whether or not hydroxylation occurs, furthermore some weakly enolised compounds (e.g. malonic acid) are readily oxidised. Bose et suggested a cyclic mechanism, but such a mechanism cannot be extended readily to malonic acid, or, for steric reasons, to 1,3-cyclohexanedione (Sklarz ). Bunton has suggested that hydroxylation may occur by IO4 acting as an electrophilic oxidant transferring oxygen to the substrate, viz. 

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