Synthesis and characterization of novel Schiff bases containing pyrimidine unit

The work involves synthesis of novel Schiff base derivatives containing a pyrimidine unit starting with chalcones. 4-Aminoacetophenone was reacted with 4-nitrobenzaldehyde or 4-chlorobenzaldehyde in basic medium giving chalcones, I]_a and I]_b, respectively, by Claisen-Schemidt reaction. The chalcones I]_a and I]_b were reacted with urea in HCl medium giving oxopyrimidines, II]_a and II]_b. They were also reacted with thiourea in basic medium to give thioxopyrimidines, III]_a and III]_b. The novel mono and bis Schiff bases, VIII]_na, VIII]_nb, IX]_na, IX]_nb, X]_na, X]_nb, XI]_na, and XI]_nb were synthesized by the reaction of pyrimidine derivatives; oxopyrimdines, II]_a and II]_b and thioxopyrimidines, III]_a and III]_b with 4-(4′-n-alkoxybenzoloxy)benzaldehyde VI] and polymethylene-α,ω-bis-4-oxybenzaldehydes VII]_m, respectively, in dry benzene using drops of glacial acetic acid as a catalyst. The synthesized compounds were characterized by melting points, elemental analysis, FTIR, and ¹H NMR spectroscopy.