Novel synthesis and properties of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate: autorecycling oxidation of some alcohols under photo-irradiation

Three-step reactions starting from 2-chlorotropone with barbituric acid afforded novel 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (·BF4−), which is the isoelectronic compound of the 5-ethyl-3-methyllumiflavinium ion. The stability of cation is expressed by the pKR+ value, which was determined spectrophotometrically, as ca. 6.0. The electrochemical reduction of exhibited low reduction potential at −0.58 (V vs Ag/AgNO3), upon cyclic voltammetry (CV). In a search for the reactivity, reactions of ·BF4− with some nucleophiles, hydroxide, hydride, amines, thiols, and methanol, were carried out to exhibit that the introduction of nucleophiles is dependent on the nucleophile itself. The photo-induced oxidation reactions of some alcohols catalyzed by ·BF4− under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compound ·BF4−], suggesting the oxidizing function of ·BF4− toward alcohols in the autorecycling process. The UV–vis and fluorescence spectra of were studied to suggest the electron transfer from alcohols to the excited .