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

2014; Beilstein Institute for the Advancement of Chemical Sciences; Volume: 10; Linguagem: Inglês

10.3762/bjoc.10.230

2195-951X

Ivana Šagud, Simona Božić, Željko Marinić, Marija Šindler‐Kulyk,

Synthesis of Indole Derivatives

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.