Monocyclic 1, 2, 3-triazines were reacted with ketene silyl acetal or silyl enol ether in the presence of 1-chloroethyl chloroformate to give 5-substituted 2-(1-chloroethoxycarbonyl)-2, 5-dihydrotriazines. These dihydro-adducts were readily oxidized and hydrolyzed with ceric ammonium nitrate in CH3CN/H2O to afford 5-substituted triazines.
Monocyclic 1,2,3-triazines have been allowed to react with silyl enol ether or ketene silyl acetal in the presence of 1-chloroethyl chloroformate to give 2-(1-chloroethoxycarbonyl)-5-substituted-2,5-dihydrotriazines in good yields. These dihydro adducts are oxidized by ceric ammonium nitrate in CH3CN–H2O to afford 5-substituted 1,2,3-triazines.