Recent advances in transition metal catalyzed oxidation of organic substrates with molecular oxygen.

This Critical Review provides an overview of the recent developments in the synthesis and characterization of bimetallic nanoparticles. Initially the review follows a materials science perspective on preparing bimetallic nanoparticles with designer morphologies, after which the emphasis shifts towards recent developments in using these bimetallic particles for catalysing either oxidation or reduction. In the final part of this review we present an overview of the utilization of bimetallic catalyst systems for the transformation of bio-renewable substrates and reactions related to the realization of a bio-refinery. Because of the sheer number of examples of transformations in this area, a few key examples, namely selective oxidation, hydrogenation/hydrogenolysis and reforming of biomass derived molecules, have been chosen for this review. Reports of bimetallic catalysts being used for the aforementioned transformations are critically analysed and the potential for exploiting such bimetallic catalysts have also been highlighted. A specific objective of this review article is to motivate researchers to synthesize some of the “designer” bimetallic catalysts with specific nanostructures, inspired from recent advances in the area of materials chemistry, and to utilize them for the transformation of biomass derived materials that are very complex and pose different challenges compared to those of simple organic molecules. We consider that supported bimetallic nanoparticles have an important role to play as catalysts in our quest for a more green and sustainable society.

Designing bimetallic catalysts for a green and sustainable future

Ruthenium-Catalyzed Reactions for Organic Synthesis.

Oxidation reactions are of fundamental importance in nature, and are key transformations in organic synthesis. The development of new processes that employ transition metals as substrate-selective catalysts and stoichiometric environmentally friendly oxidants, such as molecular oxygen or hydrogen peroxide, is one of the most important goals in oxidation chemistry. Direct oxidation of the catalyst by molecular oxygen or hydrogen peroxide is often kinetically unfavored. The use of coupled catalytic systems with electron-transfer mediators (ETMs) usually facilitates the procedures by transporting the electrons from the catalyst to the oxidant along a low-energy pathway, thereby increasing the efficiency of the oxidation and thus complementing the direct oxidation reactions. As a result of the similarities with biological systems, this can be dubbed a biomimetic approach.

Catalytic Oxidation of Organic Substrates by Molecular Oxygen and Hydrogen Peroxide by Multistep Electron Transfer : A Biomimetic Approach

Conventional methods for carrying out carbon–hydrogen functionalization and carbon–nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon–carbon and carbon–heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon–hydrogen functionalization and carbon–nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

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Electrochemical strategies for C-H functionalization and C-N bond formation.

Ruthenium-cobalt catalysts effectively catalyze the oxidation of alcohols by O{sub 2}. The aerobic oxidation method is attractive for a number of pragmatic reasons and has previously been limited to activated systems. 1 tab.

Aerobic oxidation of alcohols with ruthenium-cobalt bimetallic catalyst in the presence of aldehydes

N,N‘,N‘ ‘-Trihydroxyisocianuric acid (THICA) was found to be a very efficient catalyst for the oxidation of alkylbenzenes with dioxygen. Thus, a variety of meta- and para-substituted toluenes bearing an electron-withdrawing substituent such as cyanotoluene, chlorotoluene, and toluic acid under O2 (1 atm) in the presence of THICA (5 mol %) and Co(OAc)2 (0.5 mol %) at 100 °C were smoothly oxidized to the corresponding benzoic acids in almost quantitative yields. The aerobic oxidation of toluene by THICA was compared with that by N-hydroxyphthalimide. p-Xylene was efficiently oxidized by THICA to telephthalic acid in high yield (over 95%) under mild conditions.

Naruhisa Hirai

Papers

Aerobic oxidation of alcohols with ruthenium-cobalt bimetallic catalyst in the presence of aldehydes

Oxidation of substituted toluenes with molecular oxygen in the presence of N, N', N-trihydroxyisocyanuric acid as a key catalyst

Ruthenium-Catalyzed Oxidation of Alcohols with Peracids

Aerobic oxidation of 1,3,5-triisopropylbenzene using N-hydroxyphthalimide (NHPI) as key catalyst

Development of an efficient method for preparation of 1,3,5-trihydroxyisocyanuric acid (THICA) and its use as aerobic oxidation catalyst