Oxomalonic Ester

The best carbonyl components for these reactions are highly electrophilic compounds such as glyocylate, pyruvate, and oxomalonate esters, as well as chlorinated and fluorinated aldehydes. Most synthetic applications of the carbonyl-ene reaction utilize Lewis acids. Although such reactions may be stepwise in character, the stereochemical outcome is often consistent with a cyclic TS. It was found, for example, that steric effects of trimethylsilyl groups provide a strong stereochemical influence.28... 

The Martinet reaction is a somewhat similar method that makes use of the reaction of an aniline and oxomalonic ester to give 22, which on OH o... 

The Martinet procedure for the synthesis of indole-2,3-diones involves the reaction of an aminoaromatic compound and either an oxomalonate ester or its hydrate in the presence of an acid to yield a 3-(3-hydroxy-2-oxindole)carboxylic acid derivative which after oxidative decarboxylation yields the respective isatin. This method was applied with success for the synthesis of 5,6-dimethoxyisatin from 4-aminoveratrole whereas the use of 2,4-dimethoxyaniline was less successful40 (Scheme 9). 

Thermal and Lewis acid catalyzed ene reactions of electron-deficient ketones proceed in good yield. Dialkyl oxomalonate esters " and pyruvate esters have been most extensively studied. 1,2,3-Tri-ketones, methyl phenylglyoxylate, carbonyl sulfide, carbonyl cyanide, hexafluoroacetone, hexafluorocyclobutanone and 1,1,1-trifluoromethyl ketones have also been developed as enophiles. 

The Cu(n)-catalyzed reaction of silyl enol ethers with oxomalonic esters in the presence of a bis(oxazoline) ligand constitutes the first step of an access to chiral p-hydroxy acids. Enantioselective Mukaiyama aldol reaction performed in the presence of 52, and that in aqueous ethanol has been accomplished to a certain degree of success (32-85% ee). ... 

When an aromatic ring is treated with diethyl oxomalonate, (Et00C)2C=0, the product is an arylmalonic acid derivative, ArC(OH)(COOEt)2, which can be converted to an arylmalonic acid, ArCH(COOEt)2. This is therefore a way of applying the malonic ester synthesis (10-104) to an aryl group (see also 13-12). Of course, the opposite mechanism applies here The aryl species is the nucleophile. 

Or, alternatively (see Scheme 3.3), the immediate precursor of patulin could be iO, arriving through this new route to tetrahydro-y-pyrone 12, as the starting material, together with the synthon =CH-COOR, which conveniently elaborated gives either a glyoxylic ester, OCH-COOR, or an oxomalonic diester. 

Allylic carboxylation. Diethyl oxomalonate (1) undergoes a thermal ene reaction with mono-, di-, and trisubstituted alkenes at 145 180°. The reaction is also subject to catalysis with Lewis acids, which can lead to a different ene product. The products are a-hydroxymalonic esters. The corresponding malonic acids are converted to carboxylic acids by bisdecarboxylation with NaI04 and a trace of pyridine- or with ceric ammonium nitrate (CAN). Diethyl oxomalonate then functions as an cnophilic equivalent of C02. 

This reaction was initially reported by Martinet in 1913. It is a synthesis of dioxindole derivatives by alkali treatment of the condensation products from substituted anilines and ethyl or methyl ester of oxomalonic acid in the absence of oxygen. Thus it is known as the Martinet reaction. In the presence of oxygen, the dioxindoles are further oxidized into isatins. This reaction has been extended to the preparation of a- and -naphthisatins." ... 

The formation of epoxy products from the reaction of diazomethane with a-keto esters and oxomalonates could also involve soft attack at carbonyl oxygen initially. 

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