Atroposelective Arene‐Forming Wittig Reaction by Phosphorus PIII/PV=O Redox Catalysis

The Wittig reaction is renowned as exceptionally versatile method for converting a diversity of aldehydes and ketones into alkenes. Recently, strategies for chiral phosphine catalysis under PIII/PV=O redox cycling emerged to render this venerable transformation stereoselective. Herein, we describe that phosphine redox catalysis enables the enantioselective synthesis of pertinent biaryl atropisomers by means of a stereocontrolled arene‐forming Wittig reaction. Key to the process is the release of an endogenous base from readily accessible tert‐butyloxycarbonylated Morita–Baylis–Hillman adducts triggered by catalyst intramolecularization, permitting mild phosphine redox catalysis for atroposelective Wittig reactions. By this strategy, a broad diversity of biaryl atropisomers is obtained with up to 94 : 6 enantioselectivity. We report the atroposelective Wittig reaction enabled by PIII/PV=O redox catalysis. An endogenous base release compatible with Lewis acid co‐catalysis thereby generates the ylide intermediates. The mild, chiral phosphine‐catalyzed arene‐forming Wittig reaction allows the synthesis of a broad range of atropisomers with enantioselectivities of up to 94 : 6 e.r.