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Reaction of fluorine with 1,2,4-triazine-3,5(2H,4H)-dione (I) in acetic acid afforded the 6-fluoro derivative II in low yield. The 6-nitro compound III was prepared by oxidation of the 6-amino derivative of compound I with hydrogen peroxide in trifluoroacetic acid. Synthesis of the 6-cyano compound IV was accomplished by treatment of the 6-bromo derivative with cuprous cyanide in N,N,N',N'-tetramethylurea. The effect of substituents on the carbonyl frequencies for 6-substituted derivatives of I was studied.

The title compound (II) was prepared by acid-catalysed hydrolysis of N,N-disubstituted β-methoxy-α-methylacryloylureas V-VIII. This reaction is accompanied by the parallel cleavage of the amide bond in the compounds V-VII leading to N,N-disubstituted ureas and α-formylpropionic acid.

Stereoisomeric methyl 3-(N' -alkylureido)-2-methyl-2-propenoates (Ia-Id) were prepared by acid-catalyzed reaction of N-alkylureas (R = methyl, benzyl, isopropyl and tert-butyl) with methyl 3-methoxy-2-methyl-2-propenoate (III). Reaction of the ester III with N-tert-butyl-thiourea afforded the thioureides (E)-Ie and (Z)-Ie. On treatment with sodium methoxide in methanol, compounds Ia-Ic cyclized to the corresponding 3-alkyl-5-methyluracils IIa-IIc whereas compounds Id and Ie underwent only a base-catalyzed E/Z isomerization with (E)-isomers predominating.

Lithium diisopropylamide used as a base in the Claisen condensation of alkylacetates and cycloalkylacetates with ethyl formate or acetate gave substantially higher yields of β-oxo esters than sodium hydride or sodium bis(trimethylsilyl)amide. Reaction of the obtained β-oxo esters with thiourea in an alkaline medium afforded 5- or 5,6-disubstituted 2-thiouracils Ib-XIIb which on subsequent reaction with chloroacetic acid were transformed into the uracil derivatives Ia-XIIa. The UV spectra of uracils substituted in the positions 5 or 6 with cyclopropane ring exhibit in the 265 nm region bathochromic shifts of 1 to 6.5 nm as compared with the correspondingly substituted alkyl derivatives. A qualitative correlation of these shifts with the electron deficit on the carbon atom bonded to the cyclopropane ring was attempted.