A Facile Synthesis of Polycyclic Pyrimidine Fluorophores via Inter- and Intramolecular Cyclization of Activated 2-Amino-3,6-disubstitued Pyrimidin-4-ones

An efficient synthesis and fluorescent properties of a new series of fused pyrimidine derivatives are described. Condensation of aminopyrimidine derivative 1 with acetophenone leads to olefinic pyrimidine 2, various addition-cyclization reactions of which give the corresponding bicyclic pyrimidines 4, 6, and 8. Cycloaddition reaction of pyrimidine 1 to benzoyl isothiocyanate gives thiourea derivative 9. Intramolecular cyclization of compound 9 with NaOH or Br2 produces pyrimidine derivatives 10 or 12, respectively. Heteroannulation of pyrimidine 1 with ninhydrin or α-carbonyl carboxylic acid 15 gives the tetracyclic pyrimidine 14 and diazepine derivative 18, respectively. Fluorescence properties of pyrimidine derivatives have been tested.