Chemoselective Metal-Free Aerobic Alcohol Oxidation in Lignin
作者:Alireza Rahimi、Ali Azarpira、Hoon Kim、John Ralph、Shannon S. Stahl
DOI:10.1021/ja401793n
日期:2013.5.1
An efficient organocatalyticmethod for chemoselectiveaerobicoxidation of secondary benzylic alcohols within lignin model compounds has been identified. Extension to selective oxidation in natural lignins has also been demonstrated. The optimal catalyst system consists of 4-acetamido-TEMPO (5 mol %; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) in combination with HNO3 and HCl (10 mol % each). Preliminary
Photocatalytic Oxidation of Lignin Model Systems by Merging Visible-Light Photoredox and Palladium Catalysis
作者:Markus D. Kärkäs、Irene Bosque、Bryan S. Matsuura、Corey R. J. Stephenson
DOI:10.1021/acs.orglett.6b02651
日期:2016.10.7
Two-step oxidation/reduction strategies, whereby the first oxidation step is required to “activate” lignin systems for controlled fragmentation reactions, have recently emerged as viable routes toward this goal. Herein we describe a catalytic protocol for oxidation of lignin model systems by combining photoredox and Pd catalysis. The developed dual catalytic protocol allowed the efficient oxidation of lignin
SELECTIVE AEROBIC ALCOHOL OXIDATION METHOD FOR CONVERSION OF LIGNIN INTO SIMPLE AROMATIC COMPOUNDS
申请人:WISCONSIN ALUMNI RESEARCH FOUNDATION
公开号:US20140235838A1
公开(公告)日:2014-08-21
Described is a method to oxidize lignin or lignin sub-units. The method includes oxidation of secondary benzylic alcohol in the lignin or lignin sub-unit to a corresponding ketone in the presence of unprotected primarily aliphatic alcohol in the lignin or lignin sub-unit. The optimal catalyst system consists of HNO
3
in combination with another Brønsted acid, in the absence of a metal-containing catalyst, thereby yielding a selectively oxidized lignin or lignin sub-unit. The method may be carried out in the presence or absence of additional reagents including TEMPO and TEMPO derivatives.
Mild and Robust Redox-Neutral Pd/C-Catalyzed Lignol β-O-4′ Bond Cleavage Through a Low-Energy-Barrier Pathway
作者:Maxim V. Galkin、Christian Dahlstrand、Joseph S. M. Samec
DOI:10.1002/cssc.201500117
日期:2015.7.8
A Pd/Ccatalyzedredox neutral CO bondcleavage of 2‐aryloxy‐1‐arylethanols has been developed. The reactions are carried out at 80 °C, in air, using a green solvent system to yield the aryl ketones in near quantitative yields. Addition of catalytic amounts of a hydrogen source to the reaction mixture activates the catalyst to proceed through a low energy barrier pathway. Initial studies support a