Synthesis of Dibenzyls by Nickel-Catalyzed Homocoupling of Benzyl Alcohols

Abstract

Dibenzyls are essential building blocks widely used in organic synthesis, and they are typically prepared by the homocoupling of halides, organometallics, and ethers. Herein, we reported an approach to this class of compounds using alcohols, which are more stable and readily available. The reaction proceeds via nickel-catalyzed and DMO-assisted dynamic kinetic homocoupling of benzyl alcohols. Both primary and secondary alcohols are tolerated.

Reductive Deoxygenative Functionalization of Alcohols by First‐Row Transition Metal Catalysis

“…The Shu group has used this strategy to synthesize dibenzyls by nickel‐catalyzed direct homocoupling of benzylic alcohols (Scheme 24). [ 41 ] By utilization of Ni(dppe)Cl 2 (5 mol%) without additional nitrogen ligand, various primary benzyl alcohols were dimerized to dibenzyls. Of note, aryl chloride has been reported to couple with benzyl alcohols, and it was tolerated.…”

CO2-Promoted and Copper-Catalyzed Dehydroxylative Coupling of Benzylic Alcohols by the NaBH4/I2 System

“…In 2021, Shu and co-workers found that dimethyl oxalate (DMO) can undergo an equilibrium reaction with alcohols, and the formed alkyl oxalates can participate in coupling reactions. They used this strategy to successfully synthesize dibenzyls by utilization of Ni­(dppe)­Cl 2 without additional nitrogen ligand . Recently, Iwasawa’s group reported a Ti–O bond photohomolysis under UV-light irradiation for generating Ti­(III) using isopropyl alcohol as a stoichiometric reductant.…”

Eosin Y‐catalyzed reductive homocoupling of para‐quinone methides under visible‐light

“…5,6 The compound IV (Figure 1), owing tetra-arylethane motif, is a sunscreen-based photolabile caged molecule for controlled discharge of carbonyl compounds. 7 Numerous synthetic protocols have been demonstrated so far to access tetra-arylethane derivatives, including dehydroxylative dimerization of benzylic alcohols under visible-light irradiation, 8 nickel/oxo-rhenium-catalyzed and ReIO 2 (PPh 3 ) 2 -promoted reductive coupling of secondary benzylic alcohols, [9][10][11] dehalogenative radical coupling of secondary benzylic halides, [12][13][14][15][16] dehydrogenative homocoupling of benzylic C-H bonds under photoredox catalysis, 17 photoderiven decarboxylative radical dimerization of diphenyl acetic acid, 18 hydrogenation of tetraphenylethylene using a metal-based amide catalyst, 19 nickel-catalyzed and hydrazine-mediated deoxygenative coupling of ketones 20 and reductive coupling of aromatic ketones under photoredox conditions. 21,22 Recently, Tang, Cai and coworkers have been described a visible lightmediated potassium-modified carbon nitride (CN-K) catalyzed reductive dimerization of p-quinone methides (p-QMs) to access tetra-arylethane derivatives.…”