An Adventure in Sustainable Cross-Coupling of Phenols and Derivatives via Carbon–Oxygen Bond Cleavage

Abstract

Aryl halides are very useful electrophiles for synthesizing various substituted aromatic compounds via metal-catalyzed cross-coupling reactions. Because of the high cost associated with their synthesis and the stoichiometric halide waste produced when using aryl halide feedstocks, cheaper and more sustainable alternatives have been explored, such as phenols. However, phenols have a very reactive hydroxyl group and a C–O bond with high dissociation energy. To overcome such challenges, earlier studies focused on finding ways to reduce the energy of the C–O bond while removing the active proton by transforming phenols into phenol derivatives (e.g., sulfonates, esters, carbamates, ethers, and metal salts). A greater ambition is to directly cross-couple phenols with nucleophiles via C–O cleavage. In this Perspective, we briefly summarize efforts and accomplishments concerning the cross-coupling of phenol derivatives and phenols.

Ethereal C–O Bond Cleavage Mediated by Ni(0)-Ate Complex: A DFT Study

“…Based on this work, together with our previous mechanistic study on etheric Kumada-Tamao reaction, we identify and characterize a novel catalytic cycle for cross-coupling mediated by Ni(0)-ate complex.Key words cross-coupling; ether; nickel catalyst; organolithium; organozinc; density functional theory (DFT) calculation Efficient and selective cleavage and transformation of C-O bonds, particularly by means of cross-coupling methods, has attracted great interest, since compounds containing C-O moieties occur widely in nature and are also extensively utilized in industry.1-8) Among C-O compounds, ethers are particularly attractive, [1][2][3][4][5][6][7][8] as they offer the advantages of 1) high atom economy/conversion efficiency (the use of ethers as simple as MeO as substrates affords fewer by-products compared with tosylate, mesylate, triflate, phosphate, etc. ), 2) environmental compatibility (cleavage of the C-O moiety in ether releases non-halogen-containing waste), and 3) excellent stability, easy accessibility and wide diversity.…”

“…1-8) Among C-O compounds, ethers are particularly attractive, [1][2][3][4][5][6][7][8] as they offer the advantages of 1) high atom economy/conversion efficiency (the use of ethers as simple as MeO as substrates affords fewer by-products compared with tosylate, mesylate, triflate, phosphate, etc. ), 2) environmental compatibility (cleavage of the C-O moiety in ether releases non-halogen-containing waste), and 3) excellent stability, easy accessibility and wide diversity.…”

Direct Synthesis of Diphenylamines from Phenols and Ammonium Formate Catalyzed by Palladium

“…[21] In an attempt to replace aryl halidesa s startingm aterials, our group has investigated the possibilityo f using phenolsa sacoupling partner for the formation of CÀN bonds through the use of heterogeneous palladium as ac atalyst. [21] In an attempt to replace aryl halidesa s startingm aterials, our group has investigated the possibilityo f using phenolsa sacoupling partner for the formation of CÀN bonds through the use of heterogeneous palladium as ac atalyst.…”

Palladium‐Catalyzed Synthesis of N‐Cyclohexyl Anilines from Phenols with Hydrazine or Hydroxylamine via N‐N/O Cleavage

“…[4] To date, a series of elegant methods for the synthesis of N-cyclohexyl anilines have been developed, which can be divided into two categories (Scheme 1, a): one involves the use of anilines as amino sources, [5] with coupling partners including arylboronic acids, [6] phenols, [7] anilines, [8] cyclohexanones [9] or cyclohexanols; [10] and the other relates to the use of cyclohexylamines as precursors, with coupling partners covering various aryl sources such as haloarenes, [11] phenols [12] and their derivatives, [13] arylboronic acids [6] and aryl Grignard reagents. [15] In 2015, our group developed a Pdcatalyzed reductive coupling of phenols with amines using sodium formate as a convenient hydrogen source to produce anilines or cyclohexylamines. Phenols are abundant and naturally occurring motifs in renewable lignocellulosic biomass, and are important precursors of aryl or cyclohexyl groups (Scheme 1, b).…”