Diethyl /3-ketopimelate

The distillate contains mostly C-acyl ester with a little of 0-acyl ester. Separation of these two esters by means of a carbonate solution in which only the C-acyl ester is soluble is possible. This separation is unnecessary in the present procedure for the 0-acyl derivative gives rise to ethyl acetoacetate during decomposition with ammonia. This low-boiling ester is removed during the distillation of diethyl -ketopimelate. 

DIETHYL P-KETOPIMELATE (Pimelic acid, p-oxo-, diethyl ester)... 

A. Diethyl oi-acelyl-fi-ketopimelate. In a 2-1. three-necked flask equipped with a merauy-sealed Hershberg stirrer, a dropping funnel, and a reflux condenser protected with a caldum chloride tube are placed ll.S g. (0.5 g. atom) of finely powdered sodium (Note 1) and 500 ml. of dry ether. The flask is placed in an ice bath, and 65.0 g. (63.5 ml., 0.5 mole) of freshly distilled ethyl acetoacetate in 150 ml. of dry ether is slowly added from the dropping funnel with stirring (approximate time for addition is 30-40 minutes). The mixture is stirred overnight, then it is... 

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. ... 

The present method offers a more convenient synthesis with appreciably higher yields of diethyl /3-ketopimelate. It is reported to be useful for the preparation of dimethyl /3-hetoadipate and diethyl /3-ketosubcrate. ... 

Gardner and co-workers developed an efficient synthesis of pimelic acid (4) from furfural (1) involving conversion to furylacrylic acid (2) and esterification, which proceeds with cleavage of the ring and disproportionation to give diethyl y-ketopimelate (3). Huang-Minlon reduction by the usual procedure in diethylene... 

Coned. H2S04 added, in very small portions at first, with manual stirring at —20 to 5° to diethyl a- (m-methoxyphenylethyl) -/ -ketopimelate, then allowed to warm to near room temp., and worked up, whereby the ester is hydrolized by refluxing 2.5 hrs. in aq. ale. KOH — y-(6-methoxy-2-carboxy-3,4-dihydro-l-naphthyl)-butyric acid. Crude Y 82%. (J. H. Hunter and J. Al Hogg, Am. Soc. 71, 1922 (1949).) s. a. 2, 795... 

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