Malonic esters, acylation with

Aminothiazole, with acetaldehyde, 42 to 2-mercaptothiazoie, 370 4-Aminothiazole-2,5-diphenyl, to 2,5 di-phenyl-A-2-thiazoline-4-one, 421 Ammothiazoie-A -oxide, 118 2-Aminothiazoles. 12 acidity of, 90 and acrylophenone, 42 acylations of, with acetic acid. 53 with acetic anhydride, 52 with acyl halides, 48 with chloracetyl chloride, 49 with-y-chlorobutyrylchloride, 50 with 0-chloropropionylchloride, 50 with esters, 53 with ethy acrylate, 54 with indoiyl derivatives, 48 with malonic esters, 55 with malonyl chloride, 49 with oxalyl chloride, 50 with sodium acetate, 52 with unsaturated acyl chloride, 49 additions to double bonds, 40 with aldehydes, 98 alkylations, with alcohols, 38 with benzyhydryl chloride, 34 with benzyl chloride, 80 with chloracetic acid, 33 with chloracetic esters, 33 with 2-chloropropionic acid, 32 with dialkylaminoalkyl halides, 33 with dimethylaminoethylchloride, 35 with ethylene oxide, 34, 38... 

The malonic ester synthesis might seem like an arcane technique that only an organic chemist would use. Still, it is much like the method that cells use to synthesize the long-chain fatty acids found in fats, oils, waxes, and cell membranes. Figure 22-4 outlines the steps that take place in the lengthening of a fatty acid chain by two carbon atoms at a time. The growing acid derivative (acyl-CoA) is activated as its thioester with coenzyme A (structure on page 1027). A malonic ester acylation adds two of the three carbons of malonic acid (as malonyl-CoA), with the third carbon lost in the decarboxylation. A )8-ketoester results. Reduction of the ketone, followed by dehydration and reduction of... 

The synthesis of barbiturates is relatively simple and relies on reactions that are now familiar enolate alkylations and nucleophilic acyl substitutions. Starting with diethyl malonate, or malonic ester, alkylation of the corresponding enolate ion with simple alkyl halides provides a wealth of different disubstituted malonic esters. Reaction with urea, (H2N)2C=0, then gives the product barbiturates by a twofold nucleophilic acyl substitution reaction of the ester groups with the -NH2 groups of urea (Figure 22.7). Amobarbi-tal (Amytal), pentobarbital (Nembutal), and secobarbital (Seconal) are typical examples. 

Ethylmalonic Acid.—Like acetoacetic ester (see p. 83), diethylmalonate contains the gioup CO.CHj.CO. By the action of sodium or sodium alroholate, the hydrogen atoms of the methylene group are successively replaceable by sodium. The sodium atoms are in turn replaceable by alkyl or acyl groups. Thus, in the present preparation, ethyl malonic ester is obtained by the action of ethyl iodide on the monosodium compound. If this substance be treated with a second molecule of sodium alcoholate and a second molecule of alkyl iodide, a second radical would be in roduced, and a compound formed of the general formula... 

The Gould-Jacobs reaction is a sequence of the following reactions (1) condensation of an arylamine 1 with either alkoxy methylenemalonic ester or acyl malonic ester 2 providing the anilidomethylenemalonic ester 3 (2) cyclization of 3 to the 4-hydroxy-3-carboalkoxyquinoline 4 (3) saponification to form acid 5, and (4) decarboxylation to give the 4-hydroxyquinoline 6. All steps of this process will be described herein with emphasis on the formation of intermediates like 3 and 4. 

Magnesium enolates play an important role in C-acylation reactions. The magnesium enolate of diethyl malonate, for example, can be prepared by reaction with magnesium metal in ethanol. It is soluble in ether and undergoes C-acylation by acid anhydrides and acyl chlorides (entries 1 and 3 in Scheme 2.14). Monoalkyl esters of malonic acid react with Grignard reagents to give a chelated enolate of the malonate monoanion. 

The Grohe-Heitzer sequence (Scheme 4.2) begins with acylation of malonate derivative 37 with benzoyl chloride 36 to give malonate 38 (Mitscher, 2005). Condensation of the malonate with an ortho-ester in the presence of a dehydrating agent such as acetic anhydride affords enol ether 39. The enol ether then undergoes an addition-elimination... 

Fig. 13.65. Acylation of various malonic diester or malonic half-ester enolates with carboxylic acid chlorides. Spontaneous decarboxylation of the acylation products to furnish /3-ketoesters (see variants 1 and 2) and transformation of the acylation products into /3-ketoesters by way of alcoholysis/decarboxylation (see variant 3).

When malonic esters are the acylating agents, further reaction may occur with an excess of 2-aminothiazole. yielding 118 (Scheme 79) (278). 

Many alkylation and acylation reactions are most effective using anions of /3-dicarbonyl compounds that can be completely deprotonated and converted to their enolate ions by common bases such as alkoxide ions. The malonic ester synthesis and the acetoacetic ester synthesis use the enhanced acidity of the a protons in malonic ester and acetoacetic ester to accomplish alkylations and acylations that are difficult or impossible with simple esters. 

Fatty acid biosynthesis. Activated as its coenzyme A thioester, the growing fatty acid (acyl-CoA) acylates malonyl-CoA in a malonic ester synthesis. Two carbon atoms are added, with the third lost as C02. Enzymatic reduction, dehydration, and further reduction gives a fatty acid that has been lengthened by two carbon atoms. 

The first is the acylation of the magnesium derivative of diethyl malonate. The magnesium atom prevents 0-acylation with acid chlorides, and decarboxylation (p. 678) removes the redundant ester group. 

C-Alkylation of the sodio derivative is accomplished by a technique similar to the alkylation of malonic ester. Primary halogen compounds, quaternary ammonium salts,and an alkene oxide have been used as alkylating agents. Alkylation by secondary halides has been less successful. Hydrolysis of the substituted esters to acetylated amino acids is described for leucine (64%) and phenylalanine (83%). Hydrolysis with deacylation has been used to prepare histidine (45%) and phenylalanine (67%). Glutamic acid (75%) is obtained from substituted acylaminomalonates prepared by the Michael condensation of methyl acrylate and the acylated amino esters. ... 

A reaction similar to the above involves the acylation of malonic ester through its magnesium enolate. Thus, the reaction of propionyl chloride with the ester enolate leads to diethyl propionylmalonate. Thermal decomposition of this compound with /3-naphthalenesulfonic acid yields ethyl propionylacetate (57%). This modification appears to be general in that it has been extended to the use of aliphatic, aromatic, and car-balkoxy acyl chlorides. ... 

The described method of preparing diethyl jS-ketopimelate is a modification of that described by Bouveault and is essentially the same as that reported by Bardhan and Nasipuri. This ester has also been prepared by condensation of 7-carbethoxybutyryl chloride with ethoxymagnesiummalonic ester and cleavage of the resulting acylated malonic ester by (3-naphthalenesulfonic add or by acetic or propionic acids containing a trace of concentrated sulfuric acid. ... 

We have been particularly enamored with the development of experiments involving carbon-carbon bond formation, especially as part of tandem reactions occurring in a single container (see the Diels-Alder reaction. Figure 1). One such reaction is the synthesis of simple esters of coumarin-3-carboxylic acids via a Knoevenagel condensation between malonic esters and various a-hydroxybenzaldehydes, followed by intramolecular nucleophilic acyl substitution. This conversion, catalyzed by piperidine, has been carried out under a variety of conditions, for example, at room temperature without solvent... 

The first synthesis of rfZ-deoxynupharidine was reported by Kotake et al. (30). The starting material w as 2,5-lutidine which was made to react with formaldehyde to give the diol XXVII on dehydration, acetylation, and condensation with malonic ester XXVII afforded the diester XXVIII. On hydrogenation and acid hydrolysis XXVIII was decarboxylated to the valeric acid derivative XXIX. After esterification the acid was acylated with 3-furoyl chloride and distilled with soda lime to yield dehydrodeoxynupharidine (XXX), and this on hydrogenation gave dl-deoxynupharidine (II). 

The classical preparation of cyclobutyl ketones involves the base-catalyzed reaction of 1,3-dihaloalkanes with malonate esters. However, the initial product of this reaction is a cyclobutane carboxylic acid. S.D. Van Arnum and co-workers showed that cyclobutyl ketones can be efficiently synthesized starting from acyl succinates and using the... 

OrTiiphenylphosphoranyl ketoesters A facile synthesis of the compounds RCOC(=PPh3)COOEt involves zinc-mediated acylation of PhjP=CHCOOEt with RCOCI at room temperature (8 examples, 80-85%). The analogous malonate esters are obtained by reaction with chloroformates. 

Mixed anhydride synthesis. A method widfely used for the synthesis of peptides provides a general method of acylation, illustrated by the benzoylation of diethyl malonate. Benzoic acid is converted into the triethylamine salt in toluene, and the solution is treated at 0 with ethyl chloroformate to form the mixed benzoic-carbonic anhydride, with precipitation of triethylamine hydrochloride. The second component, ethoxymagnesium malonic ester, is prepared from diethyl malonate in ethanol-ether... 

These compounds are listed in Table XLVIII. iV-Acyl-3,5-pyra-zolidinediones are prepared either by acylation with acid chlorides,976 in which case acylation at C-4 occurs, or by cyclization.506,976 Cycliza-tion involves condensation of semicarbazides with malonic esters or cyclization of 3-acylsemicarbazides. 

C-Phosphorylated malonic acid derivatives are conveniently obtained by the acylation of phosphonoacetic ester anions with chloroformic esters. Further consideration has been given to the formation (and properties) of A -l,4,2-oxaza-phospholine 2-oxides (44) by cyclization of a-benzamidovinylphosphinic esters with PClg. ... 

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