3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

The fascinating story of olefin (or alkene) metathesis (eq
1) began almost five decades ago, when Anderson and
Merckling reported the first carbon-carbon double-bond
rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

https://core.ac.uk/download/pdf/4884240.pdf

Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts.

N atom, thus providing carbenes derived from pyrazolium, isothiazolium, and even quinolinium salts that contain a stabilizing heteroatom in a remote position (G-J in Figure 1). Recently, carbenes such as K, which are comprised of only one heteroatom and lack delocalization through the heterocycle, have been discovered as versatile ligands, thus constituting another important class of carbenes with low heteroatom stabilization. Both the synthesis of the organometallic complexes of these ligands as well as the (catalytic) properties of the coordinated metal centers generally show distinct differences, compared to the more classical NHC complexes, such as C2-metallated imidazolylidenes. This review intends to describe such differences and highlights the chemical peculiarities of these types of N-heterocyclic carbene complexes. It introduces, in a qualitative manner, the synthetic routes that have been established for the preparation of such complexes, covering the literature from the very beginning of activities in this area up to 2008. While specialized reviews on some aspects of the present topic have recently appeared,7 a comprehensive overview of the subject has not been available thus far. Rather than just being descriptive, the present account is mainly directed toward the impact of these still unusual metal-carbene bonding modes on the electronic properties and on the new catalytic applications that have been realized by employing such new carbene complexes. As a consequence of our focus on complexes with less-stabilized heterocyclic ligands, systems comprising acyclic carbenes have not been included, and the interested reader is, instead, referred to the pioneering and

/pdf/beyond-conventional-n-heterocyclic-carbenes-abnormal-remote-7nhdaf2lno.pdf

Beyond Conventional N-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

N-Heterocyclic carbene (NHC) ligands, introduced as analogues to phosphines, are recently getting wide attention in the design of diverse homogeneous catalytic systems.1-6 During recent years, olefin metathesis has gained a position of increasing significance.7-9 The ruthenium complex (PCy3)2(Cl2)RudCHPh 1 (Cy ) cyclohexyl) developed by Grubbs et al.10 constitutes a highly efficient metathesis catalyst11 tolerating most functional groups. In spite of the generally superb application profile of 1, its limited stability and the low activity toward substituted double bonds are major drawbacks. The initial success of olefin metathesis has spurred the intense investigation of new catalysts for this transformation. Inter alia, the recent introduction of NHCs * To whom correspondence should be addressed. E-mail: klgrela@ gmail.com. † Polish Academy of Sciences. ‡ Warsaw University. Cezary Samojłowicz was born in 1983 in Sokołów Podlaski, Poland. He obtained his MSc Eng. degree in chemical technology from the Warsaw University of Technology, studying sigmatropic rearrangements of sulfur ylides under the supervision of Tadeusz Zdrojewski. Before moving to olefin metathesis, he conducted work on supramolecular chemistry with David Reinhoudt at Twente University. Since 2007, he is conducting his PhD study under the supervision of Karol Grela.

Ruthenium-based olefin metathesis catalysts bearing N-heterocyclic carbene ligands.

The success of homogeneous catalysis can be attributed largely to the development of a diverse range of ligand frameworks that have been used to tune the behavior of various systems. Spectacular results in this area have been achieved using cyclic diaminocarbenes (NHCs) as a result of their strong σ-donor properties. Although it is possible to cursorily tune the structure of NHCs, any diversity is still far from matching their phosphorus-based counterparts, which is one of the great strengths of the latter. A variety of stable acyclic carbenes are known, but they are either reluctant to bind metals or they give rise to fragile metal complexes. During the last five years, new types of stable cyclic carbenes, as well as related carbon-based ligands (which are not NHCs), and which feature even stronger σ-donor properties have been developed. Their synthesis and characterization as well as the stability, electronic properties, coordination behavior, and catalytic activity of the ensuing complexes are discussed, and comparisons with their NHC cousins are made.

/pdf/stable-cyclic-carbenes-and-related-species-beyond-1d50zjyjzd.pdf

Stable Cyclic Carbenes and Related Species beyond Diaminocarbenes

Highly Efficient Ruthenium Catalysts for the Formation of Tetrasubstituted Olefins via Ring-Closing Metathesis

Latent ruthenium olefin metathesis catalysts that contain an N-heterocyclic carbene ligand

Kinetic Selectivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes.

Ruthenium olefin metathesis catalysts have been evaluated for the ethenolysis of methyl oleate, a natural seed oil derivative, to produce useful terminal olefins. Several N-heterocyclic carbene-based ruthenium catalysts demonstrate good activity and selectivity for the formation of terminal olefins. In particular, catalysts (10) and (21) achieved higher TONs (>20 000).

Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

In this paper, we will demonstrate the value of olefin cross metathesis as an effective synthetic tool for applications in the agrochemical and pharmaceut- ical industries. First, we will demonstrate the useful- ness of cross metathesis reactions in the efficient synthesis of the major component of the Peach Twig Borer pheromone and the of Omnivorous Leafroller pheromone, insect pheromones are environmentally friendly pest-controlling agents. Second, we will demonstrate highly efficient cross metathesis routes into novel ,-unsaturated carbonyl intermediates. These novel ,-unsaturated carbonyl intermediates can be further functionalized into pharmaceutical compounds that are difficult to prepare by the traditional synthetic methodologies. This paper high- lights key catalyst-substrate reactivity variations with different ruthenium olefin metathesis catalysts, high- lights cross metathesis reactions and techniques and highlights an efficient ruthenium catalyst removal technique.

Thay Ung

Papers

Highly Efficient Ruthenium Catalysts for the Formation of Tetrasubstituted Olefins via Ring-Closing Metathesis

Latent ruthenium olefin metathesis catalysts that contain an N-heterocyclic carbene ligand

Kinetic Selectivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes.

Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

Applications of Olefin Cross Metathesis to Commercial Products