Synthesis and properties of 4,9-methanoundecafulvenes and their transformation to 3-substituted 7,12-methanocycloundeca[4,5]furo[2,3- d]pyrimidine-2,4(1 H,3 H)-diones: photo-induced autorecycling oxidizing reaction toward amines

Abstract

The synthesis and properties of 4,9-methanoundecafulvene [5-(4,9-methanocycloundeca-2′,4′,6′,8′,10′-pentaenylidene)pyrimidine-2,4,6(1,3,5 H)-trione] derivatives 8a, b were studied. Their structural characteristics were investigated on the basis of the 1H and 13C NMR and UV–vis spectra. The rotational barrier (Δ G ‡) around the exocyclic double bond of 8a was found to be 12.55 kcal mol −1 by the variable temperature 1H NMR measurement. The electrochemical properties of 8a, b were also studied by CV measurement. Furthermore, the transformation of 8a, b to 3-substituted 7,12-methanocycloundeca[4,5]furo[2,3- d]pyrimidine-2,4(1 H,3 H)-diones 16a, b was accomplished by oxidative cyclization using DDQ and subsequent ring-opening and ring-closure. The structural details and chemical properties of 16a, b were clarified. Reaction of 16a with deuteride afforded C13-adduct 19 as the single product, and thus, the methano-bridge controls the nucleophilic attack to prefer endo-selectivity. The photo-induced oxidation reaction of 16a and a vinylogous compound, 3-methylcyclohepta[4,5]furo[2,3- d]pyrimidine-2,4(3 H)-dione 2a , toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) with the recycling number of 6.1–64.0 (for 16a ) and 2.7–17.2 (for 2a ), respectively.