Rhodium‐Catalyzed Benzylic Addition Reactions of Alkylarenes to Michael Acceptors

• Published in: Angewandte Chemie International Edition 2022-08, Vol.61 (35), p.e202207917-n/a
• Main Authors: Li, Yuntong, Wu, Wen‐Qiang, Zhu, Hui, Kang, Qi‐Kai, Xu, Lun, Shi, Hang
• Format: Article
• Language: English
• Subjects: all-carbon quaternary center; Aromatic compounds; benzylic addition; Catalysts; Chemical reactions; C−H activation; Hydrogen atoms; Hydrogen bonds; Michael acceptors; Nucleophiles; Rhodium; π-coordination
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202207917

The use of alkylarenes as nucleophile precursors in benzylic addition is challenging because the benzylic hydrogen atoms of these compounds are inert to deprotonation. Herein, we report Rh‐catalyzed benzylic addition of alkylarenes to Michael acceptors for the formation of C(sp3)−C(sp3) bonds. The catalyst is proposed to activate the aromatic ring via η6‐coordination, dramatically facilitating deprotonation of the unactivated benzylic C−H bond and addition of the resulting carbanion to the α,β‐unsaturated double bond in the absence of bases. Notably, this byproduct‐free method provides an access to all‐carbon quaternary centers through the development of ligands. A rhodium catalyzed benzylic C(sp3)− C(sp3) bond formation with Michael acceptors was achieved. The catalyst is proposed to activate the aromatic ring via η6‐coordination, dramatically facilitating benzylic deprotonation and addition of the resulting carbanion to the electrophile in the absence of a base. This byproduct‐free method features a wide scope of alkylarenes bearing primary, secondary, or tertiary benzylic C−H bonds.