Streamlined Access to Steroid‐Like Frameworks With Vicinal Tertiary and Quaternary Centers via Pd‐Catalyzed Asymmetric Bisallylation

ABSTRACT Despite remarkable advances in all‐carbon quaternary stereocenter construction, catalytic enantioselective assembly of sterically congested vicinal tertiary–all‐carbon quaternary stereodyads remains underdeveloped. Stereocontrolled access to such motifs embedded in steroid‐like frameworks represents a particularly formidable challenge. Herein, we disclose a highly efficient Pd‐catalyzed enantioselective bisallylation/ring‐closing metathesis (RCM) cascade, enabling modular asymmetric assembly of enantioenriched polycyclic architectures from simple coumarin‐derived precursors. With the newly developed chiral biaryl monophosphine ligand–Pd 2 (dba) 3 system, the reaction proceeds with exceptional enantiocontrol and diastereoselectivity. Synthetic versatility is demonstrated by divergent transformations into diverse high‐value chiral building blocks. Computational studies reveal that the formation of the bis‐π‐allylpalladium intermediate is the rate‐determining step of this sequential process. Notably, this simple yet powerful catalytic system is also applicable to cyclic N‐sulfonyl imines, offering a general and robust platform for the facile synthesis of enantioenriched homoallylic amines and structurally intricate N‐polycyclic skeletons.