Uracil-annulated heteroazulenes, 6-substituted 7,9-dimethylcyclohepta[b]
pyrimido [5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates 7a,bβ’BF 4 2 , 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 7a,bβ’BF 4
2 . The stability of cations 7a,b is expressed by the pK RΓΎ values which were determined spectrophotometrically to be 10.9 and 11.2, respectively. The electrochemical reduction of 7a,b exhibited high reduction potentials at 20.84 and 20.87 (V vs Ag/AgNO 3 ) upon cyclic voltammetry (CV). A good linear correlation between the pK RΓΎ values and reduction potentials (E1 red ) of 7a,bβ’BF 4 2 and reference compounds 4β’BF 4 2 and 5β’BF 4 2 was obtained. In a search of the reactivity, reactions of 7a,bβ’BF 4 2 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 7a,bβ’BF 4 2 toward some alcohols under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compounds 7a,bβ’BF 4 2 ], suggesting the oxidizing function of 7a,bβ’BF 4 2 toward alcohols in the autorecycling process.