engleski

Photochemical transformations of omega, omega'-diaryl substituted butadienes

The photochemistry of styryl substituted monofuran derivatives has been thoroughly investigated (1). The irradiation of the unsubstituted furan derivative 1 resulted in intramolecular cycloaddition and formation of the bicyclo[3.2.1]octadiene structure 2 via 1, 6-ring closure, in a very good yield. In order to prepare new polycyclic structures by the same methodology, new o-substituted omega, omega'-diaryl-1, 3-butadienes 3 were synthesized and the photochemistry of this system with prolonged conjugation was studied. Upon irradiation of a mixture of isomers of 1, 3-butadiene derivative 3, on 350 nm the endo-7-phenyl-2, 3-benzobicyclo[3.2.1]octa-2, 5-diene (4) was isolated as the only product. Photochemical reaction on 300 nm gave an equimolar mixture of the bicyclic structure 4 and endo-7-phenyl-2, 3-benzotricyclo[3.2.1.0 4.6]oct-2-ene (5). The identification and the mechanism of the formation of the obtained products will be discussed.

photochemistry; butadienes; cycloadditions; conjugated systems; polycyclic structures

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