The direct hydroxylation of arene C-H bonds is a highly sought-after transformation but remains an unsolved challenge due to the difficulty in efficient and regioselective C-H oxygenation and high reactivity of the phenolic products leading to overoxidation. Herein we report electrochemical C-H hydroxylation of arenes in continuous flow for the synthesis of phenols. The method is characterized by broad scope (compatible with arenes of diverse electronic properties), mild conditions without any catalysts or chemical oxidants, and excellent scalability as demonstrated by the continuous production of 1 mol (204 grams) of one of the phenol products.
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http://dx.doi.org/10.1038/s41467-022-31634-4 | DOI Listing |
Chem Sci
January 2025
Department of Chemistry, Indian Institute of Technology Hauz Khas Delhi New Delhi 110016 India
The direct transformation of methane into C oxygenates such as acetic acid selectively using molecular oxygen (O) is a significant challenge due to the chemical inertness of methane, the difficulty of methane C-H bond activation/C-C bond coupling and the thermodynamically favored over-oxidation. In this study, we have successfully developed a porous aluminium metal-organic framework (MOF)-supported single-site mono-copper(ii) hydroxyl catalyst [MIL-53(Al)-Cu(OH)], which is efficient in directly oxidizing methane to acetic acid in water at 175 °C with a remarkable selectivity using only O. This heterogeneous catalyst achieved an exceptional acetic acid productivity of 11 796 mmol mol h in 9.
View Article and Find Full Text PDFEur J Inorg Chem
May 2024
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent metalloenzymes that catalyze the hydroxylation of strong C-H bonds in polysaccharides using O or HO as oxidants (monooxygenase/peroxygenase). In the absence of C-H substrate, LPMOs reduce O to HO (oxidase) and HO to HO (peroxidase) using proton/electron donors. This rich oxidative reactivity is promoted by a mononuclear Cu center in which some of the amino acid residues surrounding the metal might can accept and donate protons and/or electrons during O and HO reduction.
View Article and Find Full Text PDFOrg Lett
January 2025
Department of Chemistry and School of Pharmacy, China State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. China.
Here we present a regio- and stereoselective alkylation approach for unprotected saccharides using synergistic boronic acid and photoredox catalysis. Targeting the equatorial C-H bond of the -1,2-diol motif, this method employs MeB(OH) as a catalyst. Mechanistic investigations indicate that the formation of a tetracoordinate boron species, resulting from the interaction between the cyclic boronic diol ester and a free hydroxyl group in the saccharide, is critical to this transformation.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720.
Polysaccharide monooxygenase (PMO) catalysis involves the chemically difficult hydroxylation of unactivated C-H bonds in carbohydrates. The reaction requires reducing equivalents and will utilize either oxygen or hydrogen peroxide as a cosubstrate. Two key mechanistic questions are addressed here: 1) How does the enzyme regulate the timely and tightly controlled electron delivery to the mononuclear copper active site, especially when bound substrate occludes the active site? and 2) How does this electron delivery differ when utilizing oxygen or hydrogen peroxide as a cosubstrate? Using a computational approach, potential paths of electron transfer (ET) to the active site copper ion were identified in a representative AA9 family PMO from (PMO9E).
View Article and Find Full Text PDFNature
January 2025
Department of Chemistry, The Scripps Research Institute, La Jolla, CA, USA.
C-H activation is the most direct way of functionalizing organic molecules. Many advances in this field still require specific directing groups to achieve the necessary activity and selectivity. Developing C-H activation reactions directed by native functional groups is essential for their broad application in synthesis.
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