Collect. Czech. Chem. Commun. 1982, 47, 518-522

Kinetics of cyclization of 1-phenyl-3-(1,2-dimethyl-3-oxo-1-butenyl)urea and ethyl 2-methyl-3-N-(N'-phenylureido)-2-butenoate

Jaromír Kaválek, Jiří Hruška and Vojeslav Štěrba

Department of Organic Chemistry, Institute of Chemical Technology, 532 10 Pardubice


1-Phenyl-3-(1,2-dimethyl-3-oxo-1-butenyl)urea (III) has been prepared by reaction of phenyl isocyanate with 4-amino-3-methyl-3-penten-2-one (I). Ethyl 2-methyl-3-N-(N'-phenylureido)-2-butenoate (V) has been prepared by analogous reaction with ethyl 3-amino-2-methyl-2-butenoate (II). Kinetics have been measured of acid and base catalyzed cyclization of III and that of base catalyzed cyclization of V giving 1-phenyl-4,5,6-trimethylpyrimidin-2(1H)-one (IV) and 3-phenyl-5,6-dimethyluracil (VI), respectively. In acid medium the compound V is only hydrolyzed. The base catalyzed cyclization of III is faster than that of V by almost two orders of magnitude.