Selective oxidative C–C bond cleavage of a lignin model compound in the presence of acetic acid with a vanadium catalyst

Abstract

Selective transformation of lignin into value-added aromatics is highly attractive and rather challenging.Catalytic oxidative degradation provides a promising approach to obtain aromatics from lignin while preserving the benzene units. In this study, vanadium-catalyzed aerobic oxidation of 2-phenoxy-1-phenylethanol was studied as a lignin model compound. The solvent played a significant role in the distribution of oxidation products. In the presence of acetic acid, oxidative C-C bond cleavage was preferred, while oxidation products via C-H bond cleavage were rather limited. A one-electron transfer process was involved in the oxidation reaction. The occurrence of vanadium(V) was detected, and the carboxylic group could coordinate to vanadium(V) through exchange with the acetylacetonato ligand during oxidation in the presence of acetic acid.

Metal Catalyst‐Free Oxidative C−C Bond Cleavage of a Lignin Model Compound by H2O2 in Formic acid

“…2‐Phenoxy‐1‐phenylethanone (LMC 1 ) and 2‐phenoxy‐1‐phenylethanol (LMC 2 ) were synthesized according to previously reported methods with phenol and 2‐bromoacetophenone as the starting materials …”

Oxidative C−C Cleavage of Ketols over Vanadium–Carbon Catalysts

“…However, homogeneous vanadium catalysts are active in the oxidative C−C cleavage of aliphatic ketols such as 2‐hydroxycyclohexanone and sugars to adipic acid and formic acid, respectively (Scheme ). As related systems, the oxidation of catechols and lignin model compounds with homogeneous vanadium catalysts have also been investigated intensively. The most investigated V‐based catalyst in the oxidative C−C cleavage of ketols is the Keggin‐type polyoxometalate H 3+ n PV n Mo 12− n O 40 (PVMo) .…”

Controlled Photocatalytic Hydrocarbon Oxidation by Uranyl Complexes

“…We were curious to see if the reaction scope could be extended from catalytic C−H to C−C bond cleavage. Lignin mimics that possess benzylic C−H bonds, such as 2‐phenoxy‐1‐phenylethanol (2P1PE; Table , entry 8), have been reported to undergo C−C bond cleavage rather than C−H bond activation, for example, when treated with [V V O 2 (acac)] (acac=acetylacetonate) under photocatalytic conditions, yielding benzaldehyde and benzoic acid with 54 % conversion in CH 3 CN . Similarly, both U NO3 and U Ph2phen catalyse photolytic C−C bond cleavage, albeit at lower yields (19 % and 18 % by GC‐MS, respectively; Table S8, entry 8), suggesting that *U VI O 2 2+ ‐mediated reactivity may be viable for lignin decomposition.…”