Dearomatization–Rearomatization Strategy for Palladium-Catalyzed C–N Cross-Coupling Reactions

Abstract

Substituted aromatic compounds play important roles in materials, biological agents, dyes, etc. Thus, the synthesis of substituted aromatic compounds has been a hot topic throughout the history of organic chemistry. Traditionally, the Friedel–Crafts reaction was a powerful tool for synthesizing substituted aromatic compounds. In recent decades, metal-catalyzed cross-coupling reactions were well developed via carbon–heteroatom bond cleavage, however, having difficulties towards some strong bonds, such as C(Ar)–OH. To overcome such challenges, newer strategies are needed. In this review, we summarize the recent efforts in the development of dearomatization–rearomatization strategy for cross-coupling reactions via C(Ar)–O bond cleavage.1 Introduction2 Dearomatization–Rearomatization Strategy for Cross-Coupling of Phenols3 Dearomatization–Rearomatization Strategy for Cross-Coupling of Biphenols4 Dearomatization–Rearomatization Strategy for Cross-Coupling of Diphenyl Ethers5 Dearomatization–Rearomatization Strategy for Cross-Coupling of Indoles6 Summary

Ruthenium/η5-Phenoxo-Catalyzed Amination of Phenols with Amines

“…We performed the amination with α-deuterated n -dodecylamine ( 2a- d ) under the optimized conditions (Scheme ). The resulting aniline 3a- d exhibited deuterium incorporation of 97% ∼ 94%, with no significant decrease in deuterium incorporation observed over the course of 36 h. This outcome does not align with a hydrogen transfer mechanism for this amination, as it would have led to a decrease in the α-D content of the amine and H/D scrambling on the phenyl ring …”

“…Transition-metal-catalyzed cross-coupling strategies, utilizing palladium or nickel catalysts, have emerged as powerful methods for producing anilines from phenol derivatives containing a masked hydroxy group, such as trifluoromethanesulfonate . For heterogeneous Pd catalysts, amination occurs through a hydrogen-borrowing mechanism in the presence of either an external or internal hydrogen source . Recently, our group reported a rhodium­(III)-catalyzed amination of phenols with amines by leveraging π-coordination-enabled umpolung substitution .…”