Yuko Yokota

Controlled reduction of pyrimidin(e)-2(1H)-ones and -thiones with metal hydride complexes. Regioselective preparation of dihydro- and tetrahydro-pyrimidin-2(1H)-ones and the corresponding thiones

1,4,6-Trisubstituted pyrimidin-2(1H)-ones were easily reduced with sodium borohydride to give mixtures of 3-aryl-3,4-dihydro-, 1-aryl-3,4-dihydro-, and 3,4,5,6-tetrahydro-pyrimidin-2(1H)-ones. The ratio of the three products was dramatically dependent on the reaction conditions and on the nature of the 4- and 6-substituents in the pyrimidine ring. The reaction with lithium aluminium hydride is also discussed.

Reaction of pyrimidin-2(1H)-ones and -thiones with organometallic compounds. Regioselective preparation of dihydropyrimidin-2(1H)-ones and -thiones

4,6-Dimethyl-1-phenylpyrimidin-2(1H)-one (1) reacted with methylmagnesium iodide to afford 4,6,6-trimethyl-1-phenyl-3,6-dihydropyrimidin-2(1H)-one (8a) selectively; compound (1) reacted with methyl-lithium to give mainly 4,4,6-trimethyl-1-phenyl-3,4-dihydropyrimidin-2(1H)-one (8b). The reactions of various pyrimidin-2(1H)-ones and -thiones with organometallic compounds, and the influence of bulkiness of alkyl groups upon the product ratio, are also discussed.