Ethyl ethoxalylpropionate

Ethyl ethoxalylpropionate has been prepared by the Claisen condensation of ethyl oxalate with ethyl propionate as above, and by the alkylation of ethyl ethoxalylacetate. ... 

Three hundred and forty-five grams (1.7 moles) of ethyl ethoxalylpropionate, b.p., ii4-ii6°/io mm. (p. 54), is placed in a round-bottomed flask, of suitable size carrying a reflux condenser, and a thermometer is suspended from the top of the condenser into the liquid. The ethyl ethoxalylpropionate is then heated until a Aigorous evolution of carbon monoxide begins (130-150 ). The temperature of the liquid is gradually raised as the gas evolution diminishes, and finally the liquid is refluxed until no more gas comes off. The ethyl methylmalonate is then distilled. It boils at ig4-iq6 /745 mm., and the yield is 288 g. (97 per cent of the theoretical amount). 

A few extensions of the Conrad-Limpach synthesis have been applied to the synthesis of 4,7-phenanthrolines. Unlike o-phenylenediamine, which gives a quinoxaline derivative, p-phenylenediamine reacts with excess of ethyl ethoxalylpropionate to give an intermediate bisanil, which cyclizes in hot diphenyl ether to afford 3,8-dicarboethoxy-l,10-dihydroxy-2,9-dimethyl-4,7-phenanthroline in high yield.237 With diethyl ethoxymethylenemalonate as condensing agent, 6-amino-8-methoxy-quinoline has been converted into 2-carboethoxy-l-hydroxy-6-methoxy-4,7-phenanthroline.238 A related condensation affording 1-... 

An example is the synthesis of ethyl a-ethoxalylpropionate (R = CH,) in 70% yield. Ethyl oxalate and ethyl succinate form ethyl a-ethoxalyl-succinate (83%). In a mixed ester condensation, the use of a more reactive ester, such as the phenyl or biphenyl ester, helps to prevent side reactions. Simple heterocyclic esters, namely, ethyl nicotinate and ethyl 8-quinolinecarboxylate, undergo the mixed ester condensation in good yields. The internal condensation of ethyl adipate to give 2-carbethoxycyclopentanone (Dieckmann reaction) is an example of cyclization (81%). ... 

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