Visible-Light-Mediated Aerobic Oxidation of Organoboron Compounds Using in Situ Generated Hydrogen Peroxide

Abstract

A simple and general visible-light-mediated oxidation of organoboron compounds has been developed with rose bengal as the photocatalyst, substoichiometric EtN as the electron donor, as well as air as the oxidant. This mild and metal-free protocol shows a broad substrate scope and provides a wide range of aliphatic alcohols and phenols in moderate to excellent yields. Notably, the robustness of this method is demonstrated on the stereospecific aerobic oxidation of organoboron compounds.

Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer

“…The methods using oxygen have been well studied. 13,14 Some Ru, 15 Pd, 16 Fe, 17 Cu, [18][19][20] complexes have been reported to be effective catalysts in this reaction (Scheme 1b). However, the catalysts are expensive, hard to synthesis, and not environmentally friendly.…”

Amino‐Acid‐Mediated Aerobic Oxidation of Organoborons for the Synthesis of Phenolic Derivatives Using Single Electron Transfer

“…In order to identify the reaction pathways, we could pinpoint few observations during the optimization of reaction conditions, they are; i) negligible outcome of the reaction was obtained when the reaction was performed in absence of aerial conditions (Table , Entry 21), ii) albeit in very low yield (14 %), the reaction proceeded in presence of 1,4‐benzoquinone which acts as a superoxide quencher (Table , Entry 22), iii) The formation of hydrogen peroxide was detected using iodometric titration method (details of iodometric titration are given in SI) . Having observed these facts, it was assumed that the reaction mechanism involves the thermal degradation of Et 3 N in presence of l ‐histidine.…”

“…These methods are using benzoquinone, gallic acid, ascorbic acid and rose bengal as organocatalysts for the ipso ‐hydroxylation of boronic acids. Also, it was reported that the aerial oxygen can be introduced as an oxidant to accomplish the desired chemical transformations –––. Although, most of the previously reported methods are efficient and found valuable, few of these protocols are associated with limitations such as use of excess oxidizing agent, highly basic conditions, hazardous solvents, peroxides and expensive catalysts.…”

Recent Advances in Green Synthesis of Functionalized Phenols from Aromatic Boronic Compounds

“…Zhang and co‐workers reported a visible‐light‐mediated aerobic oxidation of organoboron compounds using a rose bengal photocatalyst (Scheme a) . The stereospecific aerobic oxidation of organoboron compounds demonstrated the advantage of this method.…”