Photochemistry of aroyloxiranes: Substituent effect on oxepinones and hydroxyalkenones formation

• In this study, the photo-irradiation of some aroyloxiranes with Pyrex filtered UV-light from 125 W medium pressure Hg lamp has been described. These compound furnished the 2-aryl-4,10-dihydrofuro[3,2-c][1]benzoxepin-10-ones as well as hydroxyalkenones by the photochemical irradiation. The product formation/distribution in terms of oxepinones and the hydroxyalkenones largely depended upon the nature of the substituent.

The photo-irradiation of some aroyloxiranes with Pyrex filtered UV-light from 125 W medium pressure Hg lamp has been described. These compounds furnished the 2-aryl-4,10-dihydrofuro[3,2-c][1]benzoxepin-10-ones and the hydroxyalkenones by the photochemical irradiation. The product(s) formation/distribution in terms of oxepinones and the hydroxyalkenones largely depended upon the nature of the substituent: the oxiranes having electron-donating groups in their benzoyl moiety gave the hydroxyalkenones while oxiranes having electron-withdrawing groups furnished the oxepinones as the major products. The formation of oxepinones has been envisaged to occur through the heterolytic CC bond cleavage of epoxide to give carbonyl ylide intermediates followed by the furo-oxepinone ring formation via [3+2] cycloaddition and of hydroxyalkenones through the initial β-H abstraction followed by epoxide ring opening. The structures of all the compounds (substrates and photoproducts) have been determined on the basis of their spectral data (IR, NMR and Mass).

The photo-transformation of some aroyloxiranes into oxepinones and the hydroxyalkenones has been described. The oxepinones and the hydroxyalkenones, whose distribution largely depended upon the nature of the substituent, have been envisaged to be formed through [3+2] cycloaddition and β-H abstraction, respectively.Figure optionsDownload as PowerPoint slide