Ipso-hydroxylation Of Arylboronic Acids Research Articles

Organocatalyzed ipso hydroxylation of aryl boronic acids in aqueous medium: A metal free approach

A highly efficient protocol was developed for the ipso hydroxylation of arylboronic acids using citric acid as an effective organocatalyst. The sustainable methodology offers good to excellent yields with in the rapid reaction time in water as a solvent media and 30% H2O2 as an oxidant. The reaction proceeds without the aid of any metal catalyst or base and is simple, safe, and clean. The current protocol enables the access to variety of phenols and is found to be tolerable to the diverse electronic substrates. Even, the devised reaction conditions have been found to be effective in the gram-scale synthesis of an API, Mequinol.

Surface Nanoarchitectonics of Boron Nitride Nanosheets for Highly Efficient and Sustainable ipso-Hydroxylation of Arylboronic Acids.

One of the important industrial processes commonly employed in the pharmaceutical, explosive, and plastic manufacturing industries is ipso-hydroxylation of arylboronic acids. In this work, a straightforward, metal-free methodology for the synthesis of phenols from arylboronic acids has been demonstrated using hydroxyl functionalized boron nitride (BN-OH) nanosheets. The functionalized hydroxyl groups on the BN nanosheets act as the active sites for the hydroxylation reaction to take place. The detailed optimization of reaction parameters was done in order to attain high catalytic efficiency, and the reactions were conducted in water, which eliminates the use of toxic solvents. The as-synthesized catalysts exhibited excellent recyclability and reusability in addition to high product yields and good turnover numbers. The green metrics parameters were also evaluated for the model reaction to examine the sustainable nature of the developed protocol. The use of BN-OH catalysts for the ipso-hydroxylation reactions under base-free and metal-free conditions using environmentally benign solvents is utmost desired for industrial processes and can pave a way toward sustainable organic catalysis.

Template-Less and Surfactant-Less Synthesis of CeO2 Nanostructures for Catalytic Application in Ipso-hydroxylation of Aryl Boronic Acids and the aza-Michael Reaction.

Due to its excellent physicochemical properties, CeO2 has found great importance as an electrochemical and in electronics, photocatalysis, sensing, and heterogeneous catalysis. Herein, we report the surfactant-less and template-less synthesis of CeO2 nanostructures by the hydrothermal method. The synthesized CeO2 nanostructures have been characterized in detail by electron microscopy, spectroscopy, diffractometry, and other analytical methods. The XRD studies revealed the formation of pure crystalline CeO2, possessing a cubic fluorite structure with an average crystallite size of 15.6 to 16.4 nm. Electron microscopy studies reveal the formation of cube-shaped CeO2 nanostructures with sizes below 25 nm. The cube-shaped CeO2 nanostructures exhibited a higher BET surface area compared to their bulk counterparts. The XPS analysis has confirmed the existence of Ce in the mixed oxidation states of +3 and +4, while O is present as O2- in the sample. The as-synthesized CeO2 nanostructures exhibit excellent catalytic activity in both the ipso-hydroxylation of aryl boronic acids and the aza-Michael reaction. The analysis of the used catalyst has confirmed its stability under the reported reaction conditions. The catalysts retain their catalytic activity up to the fifth run in both types of reactions, which is economically beneficial for industrial application.

Application of Raw and Chemically Modified Biomasses for Heterogeneous Cu-Catalysed Conversion of Aryl boronic Acids to Phenols Derivatives

This work describes the application of raw and chemically modified cellulose and sugarcane bagasse for ipso-hydroxylation of aryl boronic acids in environmentally friendly reaction conditions. The catalytic efficiency of five support-[Cu] materials was compared in forming phenols from aryl boronic acids. Our investigation highlights that the CEDA-[Cu] material (6-deoxy-6-aminoethyleneamino cellulose loaded with Cu) leads to the best results under very mild reaction conditions. The optimized catalytic sequence, allowing a facile transformation of boronic acids to phenols, required the mandatory and joint presence of the support, Cu2O, and KOH at room temperature. CEDA-[Cu] was characterized using 13C solid-state NMR, ICP, and FTIR. The use of CEDA-[Cu] accounts for the efficacious synthesis of variously substituted phenol derivatives and presents very good recyclability after five catalytic cycles.

Autocatalytic aerobic ipso-hydroxylation of arylboronic acid with Hantzsch ester and Hantzsch pyridine

ipso-Hydroxylation of arylboronic acids with Hantzsch ester has been developed. The by-product Hantzsch pyridine was found to promote the reaction in the presence of oxygen under ambient conditions.

Versatile catalysis of “natural extract”: oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids

In the present work, we have described the versatile applications of naturally available inexpensive citrous lemon juice as biocatalyst for controlled oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids using 30% H2O2 as a green oxidant. A series of structurally divergent sulfides and benzyl alcohols were oxidized to their corresponding sulfoxides and aldehydes, respectively, with good-to-excellent yields. Similarly, aryl and heteroaryl boronic acids were rapidly, often within minutes, transformed to their corresponding phenols at room temperature.

On-water synthesis of phenols using biogenic Cu2O nanoparticles without using H2O2

Facile synthesis of phenols using biogenic Cu2O NPs without using H2O2, ligand, base.