Diethyl malonate

uses

Diethyl malonate is the diethyl ester of malonic acid. It naturally occuring in grapes and strawberries, is widely used in the manufacture of pharmaceuticals, antioxidants, and dyes.Diethyl malonate is used in organic synthesis for the preparation of alpha-aryl malonates, mono-substituted and di-substituted acetic acid, barbiturates and artificial flavorings. It is also involved in the synthesis of pharmaceuticals like chloroquine, butazolidin and barbital. It acts as intermediate in the synthesis of vitamin B1, vitamin B6, non-steroidal anti-inflammatory agents agrochemicals and perfumes. In Knoevenagel condensation reaction, it reacts with benzaldehyde to get diethyl benzylidenemalonate.

Preparation

Reacting chloroacetic acid to cyanoacetic acid using sodium cyanide and subsequent saponification; malonic acid is finally esterified by azeotropic distillation with ethanol in benzene

Taste threshold values

Taste characteristics at 50 ppm: sweet and fruity with apple and pineapple nuances.

Synthesis Reference(s)

The Journal of Organic Chemistry, 46, p. 3151, 1981 DOI: 10.1021/jo00328a041Tetrahedron Letters, 36, p. 3997, 1995 DOI: 10.1016/0040-4039(95)00697-B

General Description

Diethyl malonate is diethyl ester of malonic acid. Acylation of diethyl malonate using magnesium chloride and triethylamine is reported. K2CO3-catalyzed 1,4-addition reaction of diethyl malonate with various substituted 1,2-allenic ketones yields polyfunctionalized β,γ-unsaturated enones.

Safety Profile

Mildly toxic by ingestion. A skin irritant. Combustible liquid when exposed to heat or flame; can react with oxidizing materials. To fight fire, use water to blanket fire, foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes. See also ESTERS.

Metabolism

When the ester was fed to chicks at a level of 5% in the diet, 32% of the energy from diethyl malonate was available (Yoshida et al. 1970). Hydrolysis of diethyl malonate would produce ethanol and malonic acid, which is a relatively strong acid and acts as an inhibitor of enzymes, including succinic dehydrogenase (Fassett, 1963). Malonic acid injected into rats or rabbits is excreted largely unchanged, but also causes increased excretion of citric and a-ketoglutaric acids (Krebs, Salvin & Johnson, 1938). Some malonate may be metabolized through the tricarboxylic acid cycle, with decarboxylation to acetate followed by transformation to succinate, which has been detected in rat urine (Lee & Lifson, 1951). Diethyl malonate was hydrolysed by adipose-tissue lipase (Lynn & Perryman, 1960) and to the monoester by α-chymotrypsin (Cohen & Crossely, 1964). It was oxidized in 110 min to the extent of 34% by the homogenized mycelium of urethane-grown Streptomyces nitrifica (Schatz, Trelawny, Schatz & Mohan, 1957).

Purification Methods

If too impure (IR, NMR) the ester (250g) is heated on a steam bath for 36hours with absolute EtOH (125mL) and conc H2SO4 (75mL), then fractionally distilled under reduced pressure. Otherwise fractionally distil it under reduced pressure and collect the steady boiling middle fraction. [Beilstein 2 IV 1881.]