Synthesis and properties of 1-aryl-2-alkyl-1,4,5,6- tetrahydropyrimidines

Article abstract of DOI:10.1002/jhet.5570360116

A general method is described for the synthesis of 1-aryl-2-alkyl- 1,4,5,6-tetrahydropyrimidines 1, by cyclization of N-acyl-N'- aryltrimethylenediamines 2 with trimethylsilyl polyphosphate. Precursors 2 were obtained by aminolysis of the corresponding N-(3-bromopropyl)arnides 3. The ¹H nmr spectra of tetrahydropyrimidines 1 are analyzed, discussing the influence of substituents in positions 1 and 2 of the heterocyclic ring. Alkaline hydrolysis of compounds 1, which originates exclusively N-acyl-N'- aryltrimethylenediamines 2, through an intermediate carbinolamine, was also studied. Cleavage of such an intermediate is discussed in the light of the stereoelectronic control theory. Reduction of compounds 1 with borane, leads regiospecifically to N-alkyl-N'-aryltrimethylenediamines 6.