Synthesis and photochemistry of 3,6-difluoro-10,11-benzopentacyclo [6,4,0.0,0.0]dodeca-4,10-diene

Abstract

9,1 2- Difluoro- and 9,12-dichlorotetracyclo[6.4.2.2.0] hexadeca-2,4,6,13,15-pentaene-1 0,1 1-dicarboxylic anhydrides (2a) and (2b) were prepared by 4π_s+ 4π_s photocycloaddition between cis-3,6-difluoro- or cis-3,6-dichloro-1,2-dihydrophthalic anhydride and naphthalene, respectively. 12,15-Difluoro- and 12,15-dichlorohexacyclo[8.6.0.0.0.0.0]hexadeca-3,5,7-triene-13,14-dicarboxylic anhydrides (6a) and (6b) were obtained by 2π_s+ 2π_s intramolecular photocycloaddition of adducts (2a) and (2b), respectively. 12,15-Difluorohexacyclo[8.6.0.0.0.0.0]hexadeca-3,5,7,13-tetraene (7a) has been synthesized by the electro-oxidative decarboxylation of anhydride (6a) and the excited singlet naphthalene has been observed on irradiation of adduct (7a), and is presumably formed via an adiabatic pathway.