Phenobarbital: Phenobarbital, 5-ethyl-5-phenylbarbituric acid or 5-ethyl-5-phenylhexa-hydropyrimindin-2,4,6-trione (4.1.4), has been synthesized in several different ways [1-4]. There is no major difference between them. The first method consists of ethanolysis of benzyl cyanide in the presence of acid, giving phenylacetic acid ethyl ether, the methylene group of which undergoes acylation using the diethyloxalate, giving diethyl ester of phenyloxobutandioic acid (4.1.1), which upon heating easily loses carbon oxide and turns into phenylmalonic ester (4.1.2). Alkylation of the obtained product using ethylbromide in the presence of sodium ethoxide leads to the formation of a-phenyl-a-ethylmalonic ester (4.1.3), the condensation of which with urea gives phenobarbital
C2H5OH / H
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