Synthesis, properties, and oxidizing function of 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates

Uracil-annulated heteroazulenes, 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates , which are the isoelectronic compounds of 5-dezazaflavin, were synthesized. X-Ray crystal analysis and MO calculations were carried out to clarify the structural characteristics of . The stability of cations is expressed by the pKR+ values which were determined spectrophotometrically to be 10.9 and 11.2, respectively. The electrochemical reduction of exhibited high reduction potentials at −0.84 and −0.87 (V vs Ag/AgNO3) upon cyclic voltammetry (CV). A good linear correlation between the pKR+ values and reduction potentials (E1red) of and reference compounds and was obtained. In a search of the reactivity, reactions of with some nucleophiles, hydride and diethylamine, were carried out to clarify that the introduction of nucleophiles to give regio-isomers is dependent on the nucleophile. The photo-induced oxidation reactions of toward some alcohols under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compounds ], suggesting the oxidizing function of toward alcohols in the autorecycling process.