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. © 2017 American Chemical Society.