Synthesis of some benzofurooxepines’ derivatives via [3+2] cycloaddition of epoxide with tethered alkyne: A photochemical approach

•Benzoyl oxiranes act as substrates for the benzofurooxepinones.•A novel, environmentally benign photochemical approach for the synthesis of benzofurooxepinones.•Furo-oxepinone ring formation via [3+2] cycloaddition.•2-Arylbenzo[b]furo[2,3-e]oxepin-10(4H)-ones may have pharmaceutical importance.

A novel, environmentally benign and single-step synthesis of 8-chloro-2-arylbenzo[b]furo[2,3-e]oxepin-10(4H)-ones by the photochemical irradiation of 2-{5-chloro-2-(prop-2-ynyloxy)benzoyl}-3-aryloxiranes has been developed. Some of these substrates also furnished hydroxyalkenones alongside. The formation of oxepinones as major products from these substrates has been envisioned to occur through the heterolytic CC bond cleavage of epoxide, the oxirane ring giving carbonyl ylide intermediates followed by the furo-oxepinone ring formation via [3+2] cycloaddition while the hydroxyalkenones’ formation as minor products takes place through the initial β-H abstraction followed by oxirane ring opening.

Graphical abstractA novel, environmentally benign and single-step photochemical synthesis of 8-chloro-2-arylbenzo[b]furo[2,3-e]oxepin-10(4H)-ones from 2-{5-chloro-2-(prop-2-ynyloxy)benzoyl}-3-aryloxiranes involving the carbonyl ylide intermediates produced through the heterolytic CC bond cleavage of the oxirane ring followed by [3+2] cycloaddition has been described.Figure optionsDownload full-size imageDownload as PowerPoint slide