Visible-Light Photocatalytic Tri- and Difluoroalkylation Cyclizations: Access to a Series of Indole[2,1‑<i>a</i>]isoquinoline Derivatives in Continuous Flow

A process for achieving photocatalyzed tri- and difluoromethylation/cyclizations for constructing a series of tri- or difluoromethylated indole­[2,1-a]­isoquinoline derivatives is described. This protocol utilized an inexpensive organic photoredox catalyst and provided good yields. Moreover, the combination of continuous flow and photochemistry, designed to provide researchers with a unique green process, was also shown to be key to allowing the reaction to proceed (product yield of 83% in flow vs 0% in batch).