Merger of visible-light photoredox catalysis and C–H activation for the room-temperature C-2 acylation of indoles in batch and flow

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.