Recent Advances in C-O Bond Cleavage of Aryl, Vinyl, and Benzylic Ethers

Transition metal-catalyzed cross-coupling with aryl halides has revolutionized the way of diversifying aromatic compounds. Aryl ethers are attractive alternatives to aromatic halides as coupling partners considering the accessibility and potential environmental benefits. The last two decades have witnessed a striking success in the field of C-O bond activation of aryl ethers, including the construction of C-C bond and C-X bond, as well as reductive deoxygenation. Here, we present a comprehensive review of C-O bond activation in the context of aryl, vinyl, and benzylic ethers. This review elaborates on the current state-of-the-art methods, categorized by different catalytic systems, including transition metal catalysis, photoredox catalysis, and other innovative approaches. The newly developed methods allow C-O bond activation under mild conditions with exceptional functional group tolerance, potentially enabling the late-stage functionalization of pharmaceuticals. The limitations and future perspectives of the methods are also presented.

Transition-Metal-Catalyzed Cross-Coupling Reactions of Grignard Reagents

Transition-metal-catalyzed cross-coupling of organo­halides, ethers, sulfides, amines, and alcohols (and derivatives thereof) with Grignard reagents, known as the Kumada–Tamao–Corriu reaction, can be used to prepare important intermediates in the synthesis of numerous­ biologically active compounds. The most frequently used transition metals are nickel, palladium, and iron, but there are several examples for cross-coupling reactions catalyzed by copper, cobalt, manganese, chromium, etc. salts and complexes. The aim of this review is to summarize the most important transition-metal-catalyzed cross-coupling reactions realized in the period 2000 to 2020.

1 Introduction

2 Nickel Catalysis

3 Palladium Catalysis

4 Iron Catalysis

5 Catalysis by Other Transition Metals

5.1 Cobalt Catalysis

5.2 Copper Catalysis

5.3 Manganese Catalysis

5.4 Chromium Catalysis

6 Conclusion

Catalytic C(sp2)-C(sp3) Bond Formation of Methoxyarenes by the Organic Superbase t-Bu-P4

The organic superbase catalyst t-Bu-P4 achieves nucleophilic aromatic substitution of methoxyarenes with alkanenitrile pronucleophiles. A variety of functional groups [cyano, nitro, (non)enolizable ketone, chloride, and amide moieties] are allowed on methoxyarenes. Moreover, an array of alkanenitriles with/without an aryl moiety at the nitrile α-position can be employed. The system also features no requirement of a stoichiometric base, MeOH (not salt waste) formation as a byproduct, and the production of congested quaternary carbon centers.