General approach to substituted naphtho[1,2-b]benzofurans via photochemical 6π-electrocyclization of benzofuranyl containing cinnamonitriles

At the first time, we elaborated the method of synthesis of naphtho[1,2-b]benzofurans based on photoinduced reaction of acrylonitriles containing 2-arylbenzofuran fragment as part of 1,3,5-hexatriene system. The considered reaction proceeds via initial 6π-electrocyclization followed by [1,9]-H sigmatropic shift and final oxidative aromatization of central benzene ring. It was shown that 5,6-dihydronaphtho[1,2-b]benzofurans are key intermediates of studied process. The structures of obtained 5,6-dihydronaphtho[1,2-b]benzofuran and one of the target naphtho[1,2-b]benzofurans were confirmed by X-ray diffraction. [Display omitted] •Photocyclization of benzofuranyl containing cinnamonitriles was studied.•The photochemical method of the synthesis of naphtho[1,2-b]benzofurans was elaborated.•The key intermediate 5,6-dihydronaphtho[1,2-b]benzofuran was isolated.•Typical structures were confirmed by X-ray crystallographic analysis.