engleski

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o- vinylstyryl)oxazoles

Novel cis/trans-4- and cis/trans-5-(2- vinylstyryl)oxazoles have been synthesized by Wittig reactions from the diphosphonium salt of α, α’-o-xylene dibromide, formaldehyde and 4- and 5-oxazolecarbaldehydes, respectively. In contrast, trans-5-(2- vinylstyryl)oxazole has been synthesized by the van Leusen reaction from trans-3-(2-vinylphenyl)acrylaldehyde which is prepared from o-vinylbenzaldehyde and (formylmethylene)triphenylphosphorane. The 4- and 5-(2-vinylstyryl)oxazoles afford, by photochemical intramolecular cycloaddition, diverse fused oxazoline- benzobicyclo[3.2.1]octadienes, which are identified and characterized by spectroscopic methods. The photoproducts formed are relatively unstable and spontaneously or on silica gel undergo oxazoline ring opening followed by formation of formiato- or formamido-benzobicyclo[3.2.1]octenone derivatives. On irradiation of 4-(2- vinylstyryl)oxazole small quantities of electrocyclization product, 4-(1, 2- dihydronaphthalen-2-yl)oxazole, are isolated and spectroscopically characterized.

bicyclo[3.2.1]octane; intramolecular photocycloaddition; oxazole; styryl; vinyl

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