TRANSFORMATIONS THERMIQUES DES PHOTOOXYDES MESO DES ACENES-VI. CAS DES PHOTOOXYDES DE PENTACENES

Article abstract of DOI:10.1016/0040-4020(80)80116-5

Thermolysis of the meso-pentacenic photooxides 1P, 1dP and 1tP, in solution, brings about various isomerizations which appear strongly affected by the phenyl substituents.Thus the pentacene photooxide 1P gives only the bicyclic acetal 9P, beside pentacenequinone 5P in high ratio.With the photooxides 1dP of 6,13-diphenylpentacene and 1tP of 5,7,12,14-tetraphenylpentacene, the main products are the naphthocyclobutenic diethers 8dP and 8tP, which are formed in competition with the bicyclic acetals 9dP and 9tP and, in the first case, with an isomer of a new kind, the bis-naphthofuranic diether 13dP.These discrepancies are interpreted in terms of the effect of phenyl groups on the successive steps of the previously established isomerization process of meso-acenic photooxides. Comparative analysis of the chemical shifts of the central carbon atoms, in (13)C NMR, allows the unambiguous assignment of the structure of each isomer.