Synthesis and characterization of heterocyclic compounds containing guanidine moiety

Abstract

Heterocyclic compounds containing guanidine moiety were synthesized and characterized. A novel tautomerism was found in dihyropyrimidines such as 2,4,6,6-tetramethyldihydro-pyrimidine and 2-amino-4,6,6-trimethyldihydropyrimidine by the observation of H-D exchanges on both 2-and 6-methyl protons by the treatment of dihydropyrimidines with $CD_3OD$ in the absence of base under the mild conditions. The ratio of their tautomeric isomers is differentiated according to solvents. New acyclic nucleosides were synthsized by the reaction of dihydropyrimidines with acyclic chains and characterized. Melamine which is an important compound in the industrial fields was easily synthesized in 1,1,1,3,3,3-hexamethyldisilazane and the mechanism was examined. The reaction of urea with α, β -unsaturated ketones did not give cyclized compounds. However, silylated urea was reacted with α, β -unsaturated ketones under catalytic amount of lithium hydroxide to give tetrahydropyrimidine-2-ones in good yields. Silylated diimide is an important moiety which may be converted into silylated guanidine, silylated urea, and silylated thiourea moiety. Silylated diimide was successfully synthesized from bistrimethylsilylurea and triphenylphosphine dibromide in good yield.