Organometallics for Green Catalysis

Table of Contents

1. Frontmatter

2. Metal-Catalysed Hydrogenation of CO2 into Methanol

   Maximilian Franz Hertrich, Matthias Beller

   Abstract

   The conversion of carbon dioxide into value-added chemicals is of growing importance for academic and industrial scientists. Regarding scale, the reduction of carbon dioxide to methanol is the most important reaction, not only for chemical products but also as a potential energy vector. Herein, we describe recent developments in carbon dioxide reduction to methanol focusing on the use of organometallic catalysts.

3. Catalytic Processes Combining CO2 and Alkenes into Value-Added Chemicals

   Synthesis of Cyclic Carbonates, Lactones, Carboxylic Acids, Esters, Aldehydes, Alcohols, and Amines Marc Schmitz, Matilde V. Solmi, Walter Leitner

   Abstract

   The present chapter comprises an overview on catalytic pathways to synthesize a highly desired variety of common compounds/chemicals starting from carbon dioxide as C1 building block and simple alkenes. After a summary of the corresponding pioneering work of the past, the authors focus on state-of-the-art protocols. New transformations based on simple and non-activated starting materials containing a C–C double bond functionality leading to a broad product portfolio are covered. Overall, this chapter embraces sustainable routes, reagents, and apparatus to produce value-added products starting from CO₂ and alkenes as cheap and readily available building blocks.

4. Recent Advances on CO2 Utilization as C1 Building Block in C-N and C-O Bond Formation

   Synthesis of N-Formyl Amines, N-Methylamines, and Dialkoxymethanes Kassem Beydoun, Jürgen Klankermayer

   Abstract

   In the last decade, enormous efforts have been initiated to establish catalytic transformations with carbon dioxide (CO₂) as a C₁ building block toward the synthesis of value-added products. The scientific development was largely based on the design of tailored molecular catalysts and ligands, making novel synthetic pathways with CO₂ as substrate achievable. Herein, recent applications using CO₂ for the homogeneous catalyzed formation of C-N and C-O bonds within the synthesis of formamides, methylamines, and dialkoxymethanes are summarized, focusing on the construction of value-added intermediates and products.

5. Alkene Metathesis for Transformations of Renewables

   Christian Bruneau, Cédric Fischmeister

   Abstract

   Alkene metathesis of unsaturated bio-sourced olefins, a green and atom economic strategy, has been recently investigated with the objective of producing high-value molecules and polymer precursors. This chapter contains the recent developments in this field using terpenes, terpenoids, and fatty acid derivatives as olefin metathesis partners. The successful achievements with these renewable substrates presenting different types of carbon-carbon double bonds in self-metathesis, ring closing metathesis, cross metathesis including ethenolysis, and ring opening metathesis are presented.

6. Metal-Catalyzed Aromatic C-O Bond Activation/Transformation

   Mamoru Tobisu, Naoto Chatani

   Abstract

   Phenol derivatives have attracted significant attention as a renewable aromatic feedstock for the production of organic compounds that are required by society. However, the inertness of a C(aryl)-O bond of phenol derivatives poses a significant challenge for the direct functionalization at the ipso position. This review summarizes the recent advances in the area of catalytic transformations of unactivated phenol derivatives via the activation of C(aryl)-O bonds of aryl esters, carbamates, and ethers as well as arenols. The most intensively studied catalysts are nickel complexes, which allow a range of nucleophiles to be coupled with phenol derivatives. Group 8 and 9 metal complexes have also been used to activate C(aryl)-O bond of such phenol derivatives, and these are also covered in this review.

7. Hydrogenation/Dehydrogenation of Unsaturated Bonds with Iron Pincer Catalysis

   William D. Jones

   Abstract

   This chapter examines iron pincer complexes that catalyze hydrogenation and dehydrogenation reactions of common organic compounds, focusing on work reported in the last decade. Substrates include aldehydes, ketones, alcohols, esters, nitriles, imines, amines, CO₂, formic acid, amides, alkenes, and alkynes. Hydroboration and hydrosilation catalysis with iron pincers are also summarized. Some examples of enantioselective iron catalysis using pincers and tetradentate ligands are included. Examples of C–O cleavage have also been reported, and the scope of this chemistry is presented.

8. Conversion of Alcohols to Carboxylates Using Water and Base with H2 Liberation

   Peng Hu, David Milstein

   Abstract

   Production of carboxylic acids from alcohols is an important process for both industry and laboratory. Traditional methods usually require environmentally unfriendly oxidants and generate stoichiometric waste. Recently, methods using O₂ as oxidant, oxidation processes applying stoichiometric hydrogen acceptors and acceptorless dehydrogenative coupling reactions to generate carboxylic acids/carboxylic acid salts have been developed. This chapter reviews the reported results on the generation of carboxylic acids/carboxylates by acceptorless dehydrogenative coupling of alcohols and water. The chapter is according to the types of catalysts used; reaction conditions, product yields, and mechanisms are also discussed.

9. Selective Transfer Hydrogenation of α,β-Unsaturated Carbonyl Compounds

   Ronald A. Farrar-Tobar, Sergey Tin, Johannes G. de Vries

   Abstract

   Allylic alcohols are very versatile compounds which are used in a large variety of industrial processes. Transfer hydrogenation of α,β-unsaturated carbonyl compounds is a very appealing approach to obtain allylic alcohols. It avoids the use of stoichiometric and hazardous reagents such as NaBH₄ or LiAlH₄. Furthermore, compared to classical catalytic hydrogenations, these reactions do not need special equipment such as autoclaves or high-pressure reactors. Thus, protocols for transfer hydrogenation are cheaper and safer. One of the major problems in the reduction of unsaturated carbonyl compounds is to achieve high chemoselectivity. Free energy barriers for the reduction of carbonyl compounds and for the reduction of conjugated carbon-carbon double bonds are often very close in value. For that reason, mixtures of products as well as fully reduced products are often obtained making the scope of many catalysts limited. Herein we review the literature on selective transfer hydrogenation of α,β-unsaturated carbonyl compounds to the allylic alcohols using soluble transition metal complexes as catalysts. Ruthenium is the most employed metal in this field followed by iridium. In addition, some examples using complexes based on other transition metals including some first-row transition metals were found. This is a rapidly growing field. The review is structured according to the metals and to the hydrogen source used. In addition to these reductions catalysed by transition metal-based catalysts, there exists another type of transfer hydrogenation which follows a different mechanism which is known as the Meerwein-Ponndorf-Verley (MPV) reaction. This reaction uses metal alkoxide catalysts based on cheap metals such as aluminium. Whereas the original catalysts such as aluminium tri-isopropoxide were very slow, new variants have been developed that are much faster. The mechanisms reported for the MPV reaction and the transfer hydrogenation are briefly summarized, and the most interesting features of all references cited in this work are highlighted.

10. Functionalization of C(sp2)–H Bonds of Arenes and Heteroarenes Assisted by Photoredox Catalysts for the C–C Bond Formation

    Pierre H. Dixneuf, Jean-François Soulé

    Abstract

    The formation of C–C bonds from arenes and heteroarenes through transition metal-catalyzed C–H bond functionalizations is one of the major achievements of these last decades. It is now possible to perform such transformations under mild reaction conditions with the help of visible light photocatalysis leading to eco-friendly and safer process to build organic molecules or materials. This chapter will focus on photoredox catalysis which involves a C(sp²)–H bond functionalization step for the formation of C(sp²)–C bonds [i.e., direct arylations and (perfluoro)alkylations] and will show how this hot topic contributes to the development of green chemistry.

11. Green Cross-Coupling Using Visible Light for C–O and C–N Bond Formation

    Hong Yi, Yichang Liu, Aiwen Lei

    Abstract

    The development of green and sustainable approaches in organic synthesis can provide an environmentally friendly method in the industrial manufacture. Recently, visible-light-mediated photocatalysis has achieved great progress and been a powerful tool to the construction of new chemical bonds in the green synthetic community. This chapter provides an updated summary of visible-light-mediated cross-coupling for C–O and C–N bond formations. Compared with the traditional synthetic methods, the visible-light catalysis provides a new way for the useful compounds synthesis (O-containing and N-containing molecules).

12. Correction to: Functionalization of C(sp2)–H Bonds of Arenes and Heteroarenes Assisted by Photoredox Catalysts for the C–C Bond Formation

    Pierre H. Dixneuf, Jean-François Soulé

13. Backmatter