Ethyl, amine malonic acid

Keywords aromatic aldehyde, primary amine, malonic acid monoethyl ester, Rodionov reaction, microwave irradiation, / -aryl-/ -amino acid ester, ethyl cinna-mate... 

It is now applied more widely to include malonic acid derivatives, such as diethyl monoethyl-malonate, ethyl cyanacetate, etc. Various amines may be used as catalysts, and usually the most effective is piperidine (hexahydro-pyridine) a mixture of piperidine and pyridine, or pyridine alone, is also often used. 

In the above reaction one molecular proportion of sodium ethoxide is employed this is Michael s original method for conducting the reaction, which is reversible and particularly so under these conditions, and in certain circumstances may lead to apparently abnormal results. With smaller amounts of sodium alkoxide (1/5 mol or so the so-called catal3rtic method) or in the presence of secondary amines, the equilibrium is usually more on the side of the adduct, and good yields of adducts are frequently obtained. An example of the Michael addition of the latter type is to be found in the formation of ethyl propane-1 1 3 3 tetracarboxylate (II) from formaldehyde and ethyl malonate in the presence of diethylamine. Ethyl methylene-malonate (I) is formed intermediately by the simple Knoevenagel reaction and this Is followed by the Michael addition. Acid hydrolysis of (II) gives glutaric acid (III). 

Wolfbeis investigated the reactions of amines and orthoesters with different CH-acid molecules (81CB3471). When the reactions of aniline, ethyl orthoformate, and dialkyl malonates (2 mol) were carried out at 130-140°C for 4 hr, phenylaminomethylenemalonamates (245) were obtained (81CB3471). Similar reactions with aliphatic amines were unsuccessful. Phenylaminomethylenemalonic acid could not be prepared in the reactions of aniline, methyl orthoformate or orthoacetate, and malonic acid. When these reactions were carried out in 2-propanol, only amidines (246) were obtained. 

The synthesis of the moxifloxacin core (de Souza, 2006 Martel et al., 1997 Seidel et al., 2000) proceeds from a Grohe-Heitzer sequence as described earlier in the chapter. Unlike the traditional Grohe-Heitzer sequence, however, the opening step involved the reaction between acid chloride 101 with the mono potassium salt of malonic acid monoethyl ester (102) in the presence of triethylamine to deliver ketoester 103 (Scheme 4.18). Treatment of 103 with ethyl orthoformate furnished acrylate 104, which reacted with cyclopropyl amine to afford 105. Cyclization of 105 in the presence of sodium fluoride in DMF gave the moxifloxicin core 106. 

The Pechmann and Knoevenagel reactions have been widely used to synthesise coumarins and developments in both have been reported. Activated phenols react rapidly with ethyl acetoacetate, propenoic acid and propynoic acid under microwave irradiation using cation-exchange resins as catalyst <99SL608>. Similarly, salicylaldehydes are converted into coumarin-3-carboxylic acids when the reaction with malonic acid is catalysed by the montmorillonite KSF <99JOC1033>. In both cases the use of a solid catalyst has environmentally friendly benefits. Methyl 3-(3-coumarinyl)propenoate 44, prepared from dimethyl glutaconate and salicylaldehyde, is a stable electron deficient diene which reacts with enamines to form benzo[c]coumarins. An inverse electron demand Diels-Alder reaction is followed by elimination of a secondary amine and aromatisation (Scheme 26) <99SL477>. 

Ail equimolar mixture of an aldehyde 1, ail amine acetate, and a malonic acid derivative 3 (without solvent) was irradiated in an open glass vessel in a micro-wave oven (Funai M0785VT, 170 W) for several minutes (until the release of CO2 was complete). The reaction was monitored by TLC. The reaction products were separated by column chromatography on silica gel with a benzene-ethyl acetate eluent (2 1). Note that an increase in the microwave power up to 350 W resulted in a decrease in the yield of the target amino ester. 

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%). ... 

The synthesis of 2,2-dimethylsuccinic acid (Expt 5.135) provides a further variant of the synthetic utility of the Knoevenagel-Michael reaction sequence. Ketones (e.g. acetone) do not readily undergo Knoevenagel reactions with malonic esters, but will condense readily in the presence of secondary amines with the more reactive ethyl cyanoacetate to give an a, /f-unsaturated cyanoester (e.g. 15). When treated with ethanolic potassium cyanide the cyanoester (15) undergoes addition of cyanide ion in the Michael manner to give a dicyanoester (16) which on hydrolysis and decarboxylation affords 2,2-dimethylsuccinic acid. 

Melphalan and the racemic analog have been prepared by two general routes (Scheme I). In Approach (A) the amino acid function is protected, and the nitrogen mustard moiety is prepared by conventional methods from aromatic nitro-derivatives. Thus, the ethyl ester of N-phthaloyl-phenylalanine was nitrated and reduced catalytically to amine I. Compound I was reacted with ethylene oxide to form the corresponding bis(2-hydroxyethyl)amino derivative II, which was then treated with phosphorus oxychloride or thionyl chloride. The blocking groups were removed by acidic hydrolysis. Melphalan was precipitated by addition of sodium acetate and was recrystallized from methanol. No racemization was detected [10,28—30]. The hydrochloride was obtained in pure form from the final hydrolysis mixture by partial neutralization to pH 0.5 [31]. Variants of this approach, used for the preparation of the racemic compound, followed the same route via the a-acylamino-a-p-aminobenzyl malonic ester III [10,28—30,32,33] or the hydantoin IV [12]. 

It is, however, possible to obtain either pyrido[2,3-rf]pyrimidine-2,4,7(1/7,377,8//)-triones or, to a lesser extent, py rido[2,3-acetic acid 99 affords ethyl 1,3-dimethyl-2,4,7-trioxo-l,2,3,4,7,8-hexahydropyrido[2,3-d]pyrimidine-6-carboxylate. Further examples of this pathway are the reaction of diethyl (ethoxymethylene)malonate with 6-amino-165 or 6-(methylamino)-l,3-dimethyluracil 222 neat at 220-230 °C, or with 6-amino-2-methoxypyrimidin-4(3/7)-one223 in acetic acid to yield the corresponding ethyl 2,4,7-trioxo-l, 2,3,4,7,8-hexahydropyrido[2,3-[Pg.118]

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