γ-Hydroxy α,β-unsaturated acetylenic ketones have been converted to 4-amino-substituted furfurals by reaction with secondary amines followed by treatment with acid in a mixture of THF and water. The stability of the furfurals depends to some extent on the nature of the amino group, whereas the reactivity has been shown to be reagent-dependent. When treated with phosphorus ylids, the expected alkenes are formed with E configuration in high yields, but when exposed to nitroalkanes under basic conditions (the Henry reaction) abnormal transformations appear to occur, and 2-acylated furans are obtained, albeit in low yield, instead of nitroalkanols.

Herein is disclosed a novel visible-light photocatalytic double C-H functionalization of indoles. The reaction affords 2,3-difunctionalized indoles in up to 84% yield, but the reaction rate depends strongly on electronic substituent effects. Mechanistic DFT studies and control experiments suggest that the secondary functionalization occurs through an independent photocatalytic oxidation of bromide ions formed during the reaction to generate molecular bromine capable of electrophilic C-3 bromination.

The title compounds can be readily functionalized via Wittig‐type reactions (not shown).