A simple and efficient visible-light-promoted method for the C-3 thiocyanation of indoles has been developed. The transformation uses Rose Bengal as the photocatalyst and air as the terminal oxidant. The reaction is mild, high-yielding, and environmentally benign.

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An aerobic visible-light driven photoredox catalytic formation of 2-substituted benzothiazoles through radical cyclization of thioanilides has been accomplished. The reaction features C-H functionalization and C-S bond formation with no direct metal involvement except the sensitizer. The reaction highlights the following: (1) visible-light is the reaction driving force; (2) molecular oxygen is the terminal oxidant, and (3) water is the only byproduct.

Direct arylation of unactivated arenes or heteroarenes with aryl halides could be carried out in the presence of potassium tert-butoxide and dimethyl sulfoxide under visible-light irradiation. Ir(ppy)3 was found to be an effective photoredox catalyst for this reaction. The reactions of aryl iodides occurred at room temperature. Elevated temperature was required for aryl bromides. Homolytic aromatic substitution was proposed to be the operative reaction pathway.

Cleavage of the aldehyde C=O bond takes place in the zirconocene‐ and AlCl3‐mediated cyclization of two molecules of an alkyne with an aldehyde to afford cyclopentadiene derivatives [Eq. (1)]. Only one of the possible positional double‐bond isomers is formed. The same method can also be used to couple two different alkynes with an aldehyde.