Polar effects in the homolytic methylation of pyrimidine: orientation and polysubstitution

The homolytic methylation of pyrimidine in aqueous solution has been investigated with three different radical sources: ButOOH–Fe2+, MeCO2H–S2O82––Ag+, and MeSOMe–H2O2–Fe2+. This last reagent, used for the first time in homolytic aromatic substitution, turned out to be the most efficient. The orientation of mono-and poly-methylated derivatives is discussed on the basis of polar effects.