Synthesis of tetrahydropyrimidines with 2-oxoalkyl groups using pyrimidinium salts and enol silyl ethers: formation of diazabicyclo[3.3.1]nona-3,6-diene derivatives
Reactions of N-silyl- or N-acyl-pyrimidinium salts with enol trimethylsilyl ethers were carried out to afford the adducts with a 2-oxoalkylgroup, that is, 2-hydroxy-4-(2-oxoalkyl)-1,2,3,4-tetrahydropyrimidines (9) or the 3-acyl derivatives (8), respectively. Monoacylation of compounds (9) gave monoamides (8) in high yields. Exhaustive acylation of diamines (9) with a large excess of 2,2,2-trichloroethyl