A mild and versatile protocol for the C–H acylation of indoles via dual photoredox/transition-metal catalysis was established in batch and flow. The C–H bond functionalization occurred selectively at the C-2 position of N-pyrimidylindoles. This room-temperature protocol tolerated a wide range of functional groups and allowed for the synthesis of a diverse set of acylated indoles. Various aromatic as well as aliphatic aldehydes (both primary and secondary) reacted successfully. Interestingly, significant acceleration (20 to 2 h) and higher yields were obtained under micro flow conditions.

A series of new secondary phosphine oxide (SPO)–gold(I) complexes have been synthesized and characterized by X-ray crystallography. Complexes exhibited dimeric structures interconnected by O–H···Cl hydrogen bonds. Their first use in homogeneous catalysis is reported and suggests a broad field of application in prototypical enyne cycloisomerization and hydroxy- and methoxycyclization reactions.

We present a supported silver nanoparticle-catalyzed dearomatization of 3-substituted indoles towards 3-spiroindolenines. Two scaffolds were investigated for this transformation. The yields range from moderate to high. In case of chiral reactants (Ugi 4-Component Reaction adducts) the process is diastereoselective with diastereomeric excess between 75 % and 92 %. The catalyst was characterized by TEM and XPS. Metal leaching was investigated by a hot-filtration and ICP-AES experiments. An apparent TOF was determined.