Novel Synthesis, Properties, and NAD+-NADH Type Redox Ability of 1,3-Dimethylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine- 2,4(1,3H)-dionylium Ions Annulated with Additional Pyrrolo[2,3-d]pyrimidine-1,3(2,4H)-dione and Furan Analogue, and Their Hydride Adducts

A convenient preparation of novel cations 11a,b+·BF4- and 12a,b+·BF4-, which are derived from annulation of the 1,3-dimethylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dionylium ion with additional pyrrolo[2,3-d]pyrimidine-1,3(2,4H)-dione and a furan analogue, was accomplished by a novel oxidative cyclization of 1,7-dihydro-7-[1‘,3‘-dimethyl-2‘,4‘(1‘,3‘H)-dioxo-6‘-(phenylamino)-pyrimidin-5‘-yl]-1,3-dimethyl-10-phenylcyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1,3H)-dione 9 and its furan-analogue by using DDQ or photoirradiation under aerobic conditions. Structural characteristics of 11a,b+ and 12a,b+ were clarified on inspection of the UV−vis and NMR spectral data as well as X-ray crystal analyses. The stability of cations 11a,b+ and 12a,b+ is expressed by the pKR+ values that were determined spectrophotometrically to be 10.7−12.6. The electrochemical reduction of 11a,b+·BF4- and 12a,b+·BF4- exhibited reduction potential at −0.93 to −1.00 (V vs Ag/AgNO3). The first reduction potential of 11a+ was re...