Ethyl hydrogen malonate

Ethyl 3-oxoalkanoates when not commercially available can be prepared by the acylation of tert-butyl ethyl malonate with an appropriate acid chloride by way of the magnesium enolate derivative. Hydrolysis and decarboxylation in acid solution yields the desired 3-oxo esters [59]. 3-Keto esters can also be prepared in excellent yields either from 2-alkanone by condensation with ethyl chloroformate by means of lithium diisopropylamide (LDA) [60] or from ethyl hydrogen malonate and alkanoyl chloride usingbutyllithium [61]. Alternatively P-keto esters have also been prepared by the alcoholysis of 5-acylated Mel-drum s acid (2,2-dimethyl-l,3-dioxane-4,6-dione). The latter are prepared in almost quantitative yield by the condensation of Meldrum s acid either with an appropriate fatty acid in the presence of DCCI and DMAP [62] or with an acid chloride in the presence of pyridine [62] (Scheme 7). 

A rapid and low cost preparation of the tiE, 5Z )-alkadienyl system encountered in several insect pheromones has been developed. Knoevenagel condensation of (T )-2-alkenals with ethyl hydrogen malonate in DMSO, in the presence... 

In an alternative method (cognate preparation in Expt 5.177), the dilithio complex of ethyl hydrogen malonate in tetrahydrofuran at low temperature is reacted with the acid chloride194 the decarboxylation process takes place spontaneously when the reaction mixture is quenched with dilute acid. 

Ethyl hydrogen malonate may be prepared from diethyl malonate by controlled hydrolysis with potassium hydroxide (see also Expt 5.147, Note (1)). 

Olefinic esters are obtained directly by the Knoevenagel condensation (cf. method 37) of ethyl hydrogen malonate with an aliphatic or aromatic aldehyde. 

The bisacylation of methylene-active compounds mentioned above can be avoided by using acylimidazoles in place of acyl halides (acylimidazoles are obtained from the carboxylic acid and sulfinyldiimidazole) for example, reaction of the magnesium enolate of ethyl hydrogen malonate and an acylimid-azole, with concomitant decarboxylation, gives the corresponding / -oxo ester 430... 

Substituted tetronic acids (89) can be obtained by condensation between the magnesium complex of ethyl hydrogen malonate and a-acetoxy-acid chlorides, followed by acid-catalysed lactonization in the presence of an alcohol (Scheme 15).The fungal metabolite derivative methyl (if)-O-methylmulticolanate (90)... 

The magnesium enolate of ethyl hydrogen malonate has been found to add in a conjugative manner to enones (141) to provide a one-pot method for the elaboration of 5-keto-esters (142). ° ... 

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