Iron(III)-Catalysis in Flow: A Sustainable Alternative to Precious-Metal-Based Lewis Acidic Superelectrophiles for Carbonyl-Olefin Metathesis

Accessing sizes larger than 5-membered rings remains challenging via catalytic carbonyl-olefin metathesis and requires Lewis acidic superelectrophiles formed with precious metal additives. Herein we report the development of a continuous flow reactor that overcomes this challenge to access 6-membered rings using FeCl3 as the Lewis acid catalyst. The plug-flow reactor design foregoes the use of precious metal additives, is user-friendly, benchtop amenable, and demonstrates up to 200-fold improved reaction efficiency over batch conditions. Computational and experimental investigations support a mechanism for catalytic carbonyl-olefin metathesis that relies on a bimolecular pathway and intermolecular proton transfer event.