Volume 27, Issue 38 p. 9748-9752
Communication

Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor

Joël Wellauer

Joël Wellauer

Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland

These authors contributed equally to this work.

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Dragan Miladinov

Dragan Miladinov

Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland

These authors contributed equally to this work.

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Thomas Buchholz

Thomas Buchholz

Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland

These authors contributed equally to this work.

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Dr. Jan Schütz

Dr. Jan Schütz

DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland

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Dr. René T. Stemmler

Dr. René T. Stemmler

DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland

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Dr. Jonathan A. Medlock

Dr. Jonathan A. Medlock

DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland

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Dr. Werner Bonrath

Dr. Werner Bonrath

DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland

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Prof. Dr. Christof Sparr

Corresponding Author

Prof. Dr. Christof Sparr

Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland

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First published: 19 April 2021
Citations: 12

Dedicated to Professor Steven V. Ley on the occasion of his 75th birthday

Graphical Abstract

The design of a customized continuous-flow photoreactor enabled a highly efficient aerobic oxygenation of phenols to provide benzoquinones and p-quinols. By using pressurized air as oxidant, ecologically benign solvents and low amounts of methylene blue as organophotocatalyst in combination with hyper red LEDs, excellent selectivity values and yields were obtained. The method is expected to improve sustainability for the production of a variety of crucial products and intermediates.

Abstract

A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.