Synthesis, properties, and oxidizing ability of 9,11-dimethylbenzocyclohepta[6,7-b]pyrimido[5,4-d]furan- 10(9H),12(11H)-dionylium tetrafluoroborate.

Convenient preparation of novel 9,11-dimethylbenzocyclohepta[6,7-b]pyrimido[5,4-d]furan-10(9H),12(11H)-dionylium tetrafluoroborate 11.BF 4 - consisted of a condensation reaction of benzo-[d]tropone with dimethylbarbituric acid and following oxidative cyclization reaction by using DDQ-Sc(OTf) 3 or photoirradiation under aerobic conditions. Alternative synthesis of 11.BF 4 - was also accomplished by a condensation reaction of 2-methoxybenzo[d]tropone with dimethylbarbituric acid and a subsequent cyclization reaction by using 42% aq HBF 4 . The X-ray crystal analysis and MO calculation were carried out to clarify the structural characteristics. Properties of the cation 11 were studied by the pK R + value (4.7) and reduction potentials (-0.46 and -1.07 V vs Ag/AgNO 3 ) as well as the reaction with some nucleophiles. The oxidizing ability of 11.BF 4 - toward alcohols in the autorecycling process was demonstrated as well.