Concise and Modular Access to a Chiral Biaryl Monophosphine Library and Downstream Use in Catalytic Enantioselective Transformations

ABSTRACT Atropoisomeric biaryl monophosphines, chiral variants of Buchwald‐type ligands, are powerful ligands for asymmetric catalysis. However, their synthesis relies heavily on resolution or step‐intensive synthetic approaches, restricting structural diversity and tuning options, thus limiting systematic exploration of their catalytic potential. We report a unified strategy for streamlined access to a broadly tunable family of atrop‐chiral biaryl monophosphines. The three‐step assembly protocol first exploits a Cp X ‐Ir III ‐catalyzed atroposelective C─H arylation of phosphine oxide to forge the biaryl core with three different diversity points. Subsequently, reduction to the phosphine and installation of the fourth diversity point provide a diverse library of 35 chiral air‐stable monophosphine ligands. Their catalytic performance was benchmarked in a challenging enantioselective gold‐catalyzed cycloisomerization and a palladium‐catalyzed asymmetric phenol dearomatization, leading to the discovery of high‐performing library members providing excellent enantioselectivities of up to 99:1 er in both transformations.