Characterization of the isomeric dialkylbarbituric acids formed by the reaction of barbiturates with diazoalkanes

The reaction of barbituric acids with diazoalkanes (diazomethane and diazoethane) gives the N,N′-dialkylbarbituric acids as the major products. Gas chromatograms of the reaction products show up to four additional peaks. These have been shown by mass and proton magnetic resonance spectrometry to be produced by the two isomeric N,O-dialkylbarbituric acids (1,4- and 1,2-dialkylbarbituric acids) and the two O,O′-dialkyl isomers.