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Selective, nickel-catalyzed hydrogenolysis of aryl ethers.

Science (New York, N.Y.) (2011-04-23)
Alexey G Sergeev, John F Hartwig
ABSTRACT

Selective hydrogenolysis of the aromatic carbon-oxygen (C-O) bonds in aryl ethers is an unsolved synthetic problem important for the generation of fuels and chemical feedstocks from biomass and for the liquefaction of coal. Currently, the hydrogenolysis of aromatic C-O bonds requires heterogeneous catalysts that operate at high temperature and pressure and lead to a mixture of products from competing hydrogenolysis of aliphatic C-O bonds and hydrogenation of the arene. Here, we report hydrogenolyses of aromatic C-O bonds in alkyl aryl and diaryl ethers that form exclusively arenes and alcohols. This process is catalyzed by a soluble nickel carbene complex under just 1 bar of hydrogen at temperatures of 80 to 120°C; the relative reactivity of ether substrates scale as Ar-OAr>Ar-OMe>ArCH(2)-OMe (Ar, Aryl; Me, Methyl). Hydrogenolysis of lignin model compounds highlights the potential of this approach for the conversion of refractory aryl ether biopolymers to hydrocarbons.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Diphenyl ether, SAJ first grade, ≥98.0%
Sigma-Aldrich
Diphenyl ether, ReagentPlus®, 99%
Sigma-Aldrich
Diphenyl ether, ≥99%, FG
Sigma-Aldrich
Nickel, wire, diam. 0.25 mm, ≥99.9%
Sigma-Aldrich
Diphenyl ether, ReagentPlus®, ≥99%
Supelco
Diphenyl ether, Selectophore, ≥99.9%