Novel photo-induced oxidative cyclization of 1,3-dimethyl-5-(1-arylmethylidene)pyrimidine-2,4,6(1,3,5 H)-triones: synthesis and properties of areno[5,6]pyrano[2,3- d]pyrimidine-2,4(1,3 H)-dionylium ions and their photo-induced autorecycling oxidizing reaction toward some amines

Abstract

Novel photo-induced oxidative cyclization was accomplished to synthesize areno[ b]pyrimido[5,4- e]pyran-2,4(1,3 H)-dionylium ions 13a– c +· ClO 4 − . Furthermore, 13a– c +· BF 4 − and their phenyl-substituted derivatives 19a, b +· BF 4 − were alternatively synthesized by the reaction of salicylaldehyde and its naphthyl derivatives with barbituric acids and subsequent treatment with aq. HBF 4. Structural characteristics of 13a– c + and 19a, b + were clarified on inspection of the UV–vis and NMR spectral data as well as X-ray crystal analyses. The electrochemical properties were studied by the CV measurement. In a search for reactivity, reactions of 13a– c +· BF 4 − with some nucleophiles, hydride, benzylamine, and H 2O, were also carried out. The photo-induced autorecycling oxidation reactions of 13a– c +· BF 4 − toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) in 643–3600% yield (recycling number of 13a– c +· BF 4 − : 6.4–36.0).