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

Novel photo-induced oxidative cyclization was accomplished to synthesize areno[b]pyrimido[5,4-e]pyran-2,4(1,3H)-dionylium ions 13a-c(+) (.) ClO4-. Furthermore, 13a-c(+) (.) BF4- and their phenyl-substituted derivatives 19a,b(+) (.) BF4- were alternatively synthesized by the reaction of salicylaldehyde and its naphthyl derivatives with barbituric acids and subsequent treatment with aq. HBF4. 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(+) (.) BF4- with some nucleophiles, hydride, benzylamine, and H2O, were also carried out. The photo-induced autorecycling oxidation reactions of 13a-c(+) (.) BF4- 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(+) (.) BF4-: 6.4-36.0). (c) 2005 Elsevier Ltd. All rights reserved.