Microfluidic Visible‐Light Paternò–Büchi Reaction of Oxindole Enol Ethers.

A novel microfluidic visible‐light process for the functionalisation of oxindoles is reported. The chemistry is based on the reactivity of the corresponding enol ethers, which participate in a site‐, regio‐ and diastereoselective [2+2] heterocycloaddition (Paternò–Büchi) process. The mild reaction conditions, the use of available ketones, together with the high generality (23 examples) and robustness (up to gram scale) make this process a useful synthetic platform for the construction of structurally strained heterocycles. [ABSTRACT FROM AUTHOR]