Photoinduced reaction of o-ethenylaryl isocyanides with organic disulfides in the presence of diphenyl ditellurides affords the corresponding bisthiolated indole derivatives via a radical cyclization process. The cyclization can proceed at room temperature upon visible-light irradiation and exhibits good tolerance to functional groups. Several organic disulfides also can be employed for this cyclization, and the corresponding bisthiolated indole derivatives are obtained selectively. In addition, the photoinduced reaction of o-ethenylaryl isocyanides with bis(2-aminophenyl) disulfide affords tetracyclic compounds in one portion.

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Upon treatment with (PhTe)(2) under visible-light irradiation, o-ethynylaryl isocyanides underwent intramolecular radical cyclization with introduction of telluro groups, affording the corresponding bistellurated quinolines.

When a mixture of o-alkynylaryl isocyanides and organic dichalcogenides such as diselenides or ditellurides was irradiated with light of wavelength over 300 or 400 nm, the intramolecular cyclization of the isocyanides took place to afford the corresponding 2,4-bischalcogenated quinolines selectively. The photochemical cyclization of 2-(phenylethynyl)phenyl isocyanide could also proceed in the presence of hydrogen transfer reagents such as tris(trimethylsilyl)silane, tributylgermyl hydride, alkanethiols, and benzeneselenol, providing the corresponding 3-phenylquinoline as the result of 2,4-dihydrogenation.

Photoinduced Intramolecular Cyclization of o-Ethenylaryl Isocyanides with Organic Disulfides Mediated by DiphenylDitelluride. -Irradiation of isocyanides of type (I) with diaryl disulfides in the presence of diphenyl ditelluride results in formation of bisthiolated indole derivatives. Treatment of (Ia) and (Id) with the functionalized disulfide (VI) affords the benzothiazoles (VII). The reaction of (Ib) and the nitrile (IX) with (VI) provides a new approach to tetracyclic pyrimidines. Coupling of (IX) with diphenyl disulfide does not yield the bisthiolated indole (XI) but its hydrolysis product (XII). -(MITAMURA, T.; IWATA, K.; OGAWA*, A.; J. Org. Chem. 76 (2011) 10, 3880-3887, http://dx.