Nitro-Substituted Hoveyda−Grubbs Ruthenium Carbenes:  Enhancement of Catalyst Activity through Electronic Activation

Demchuk O.M., Pietrusiewicz K.M., Michrowska A., Grela K.

[reaction: see text] Substituted vinylphosphine oxides have been prepared in good yield and exclusive (E)-olefin selectivity via olefin cross-metathesis using Grubbs and Hoveyda-type ruthenium catalysts. In addition, metathesis of chiral vinylphosphine oxides proceeds without racemization of the phosphorus chirality center, providing easy access to functionalized chiral nonracemic (E)-alkenylphosphine oxides.

Grela K., Harutyunyan S., Michrowska A.

A simple three-step synthesis leads to the formation of the active complex 1, which operates under very mild conditions (even at 0 °C!) and can be successfully applied in various types of olefin metathesis (ring-closing metathesis, cross metathesis, enyne metathesis), for example, in the cyclization of 2 to form 3.

Kitamura T., Sato Y., Mori M.

In ring-closing metathesis (RCM) reactions of enynes, the substituents on the multiple bonds are quite important. Although RCM of an enyne having a monosubstituted alkene proceeds smoothly using the first-generation ruthenium-carbene complex 1a, that of an enyne having a disubstituted alkene and internal alkyne using 1a does not proceed. However, the second-generation ruthenium-carbene complex 1b or 1c containing an N-heterocyclic carbene as a ligand was found to be very effective for such an enyne, and the two-metathesis products were formed in high yields.

Law M., Kind H., Messer B., Kim F., Yang P.

Himmel H., Manceron L., Downs A.J., Pullumbi P.

Herein we describe the cocondensation of Ga or In vapor with H2 in an excess of Ar at 10 ± 12 K, and the subsequent irradiation of the resulting matrix with light of different wavelengths. We show that the reaction of Ga2 or In2 with H2 directly or indirectly gives rise to three isomers of Ga2H2 and two isomers of In2H2, namely the bis( -hydrido) species Ga( -H)2Ga (1a) and In( -H)2In (1b), the trans-bent species HGaGaH (3a) and HInInH (3b), and GaGaH2 (2a) with two terminal Ga H bonds (Scheme 1). All these molecules have

Kingsbury J.S., Garber S.B., Giftos J.M., Gray B.L., Okamoto M.M., Farrer R.A., Fourkas J.T., Hoveyda A.H.

Glass-bound Ru-based catalysts! Ru-containing glass pellets (see picture) efficiently promote olefin metathesis reactions and are easily employed in syntheses of compound libraries. These robust catalysts are active in air and commercially available solvents, can be recycled up to 16 times, and removed from reaction mixtures with a simple pair of tweezers (minimal solvent waste).

Grela K., Bieniek M.

A cross-metathesis reaction was achieved between functionalised terminal olefins and phenyl vinyl sulfone by using the commercially available ruthenium catalyst 1c . The cross-metathesis products were isolated in moderate to good yield with excellent ( E )-stereoselectivity.

Garber S.B., Kingsbury J.S., Gray B.L., Hoveyda A.H.

Several highly active, recoverable and recyclable Ru-based metathesis catalysts are presented. The crystal structure of Ru complex 5, bearing a 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene and styrenyl ether ligand is disclosed. The heterocyclic ligand significantly enhances the catalytic activity, and the styrenyl ether allows for the easy recovery of the Ru complex. Catalyst 5 promotes ring-closing metathesis (RCM) and the efficient formation of various trisubstituted olefins at ambient temperature in high yield within 2 h; the catalyst is obtained in >95% yield after silica gel chromatography and can be used directly in subsequent reactions. Tetrasubstituted olefins can also be synthesized by RCM reactions catalyzed by 5. In addition, the synthesis and catalytic activities of two dendritic and recyclable Ru-based complexes are disclosed (32 and 33). Examples involving catalytic ring-closing, ring-opening, and cross metatheses are presented where, unlike monomer 5, dendritic 33 can be readily recovered.

Sierra M.A., de la Torre M.C.

From the very beginning organic chemistry and total synthesis have been intimately joined. In fact, one of the first things that freshmen in organic chemistry learn is how to join two molecules together to obtain a more complex one. Of course they still have a long way to go to become fully mature synthetic chemists, but they must have the primary instinct to build molecules, as synthesis is the essence of organic chemistry. With the different points of view that actually coexist in the chemical community about the maturity of the science (art, or both) of organic synthesis, it is clear that nowadays we know how to make almost all of the most complex molecules ever isolated. The primary question is how easy is it to accomplish? For the readers of papers describing the total synthesis of either simple or complex molecules, it appears that the routes followed are, most of the time, smooth and free of troubles. The synthetic scheme written on paper is, apparently, done in the laboratory with few, if any, modifications and these, essentially, seem to be based on finding the optimal experimental conditions to effect the desired reaction. Failures in the planned synthetic scheme to achieve the goal, detours imposed by unexpected reactivity, or the absence of reactivity are almost never discussed, since they may diminish the value of the work reported. This review attempts to look at total synthesis from a different side; it will focus on troubles found during the synthetic work that cause detours from the original synthetic plan, or on the dead ends that eventually may force redesign. From there, the evolution from the original route to the final successful one that achieves the synthetic target will be presented. The syntheses discussed in this paper have been selected because they contain explicit information about the failures of the original synthetic plan, together with the evolution of the final route to the target molecule. Therefore, they contain a lot of useful negative information that may otherwise be lost.

Kingsbury J.S., Harrity J.P., Bonitatebus P.J., Hoveyda A.H.

A Ru carbene (8, Scheme 2) that contains an internal metal−oxygen chelate is an active metathesis catalyst and is readily obtained by the sequential treatment of Cl2Ru(PPh3)3 with (2-isopropoxyphenyl)diazomethane and PCy3. This Ru-carbene complex offers excellent stability to air and moisture and can be recycled in high yield by silica gel column chromatography. The structures of this and related complexes have been unambiguously established by NMR and single-crystal X-ray diffraction studies.

Mąkosza M., Ziobrowski T., Serebriakov M., Kwast A.

Toluenesulfonates of nitrophenols react with carbanions possessing leaving groups giving products of the vicarious nucleophilic substitution of hydrogen. The yields and orientation depend on the reaction conditions and the structure of the reagents. The products obtained can be easily hydrolyzed to the corresponding phenols or — in certain cases — to hydroxynitrobenzaldehydes.

Schwab P., Grubbs R.H., Ziller J.W.

The reactions of RuCl2(PPh3)3 with a number of diazoalkanes were surveyed, and alkylidene transfer to give RuCl2(CHR)(PPh3)2 (R = Me (1), Et (2)) and RuCl2(CH-p-C6H4X)(PPh3)2 (X = H (3), NMe2 (4), OMe (5), Me (6), F (7), Cl (8), NO2 (9)) was observed for alkyl diazoalkanes RCHN2 and various para-substituted aryl diazoalkanes p-C6H4XCHN2. Kinetic studies on the living ring-opening metathesis polymerization (ROMP) of norbornene using complexes 3−9 as catalysts have shown that initiation is in all cases faster than propagation (ki/kp = 9 for 3) and that the electronic effect of X on the metathesis activity of 3−9 is relatively small. Phosphine exchange in 3−9 with tricyclohexylphosphine leads to RuCl2(CH-p-C6H4X)(PCy3)2 10−16, which are efficient catalysts for ROMP of cyclooctene (PDI = 1.51−1.63) and 1,5-cyclooctadiene (PDI = 1.56−1.67). The crystal structure of RuCl2(CH-p-C6H4Cl)(PCy3)2 (15) indicated a distorted square-pyramidal geometry, in which the two phosphines are trans to each other, and the alkyli...

Mulliken R.S.

With increasing availability of good all-electron LCAO MO (LCAO molecular orbital) wave functions for molecules, a systematic procedure for obtaining maximum insight from such data has become desirable. An analysis in quantitative form is given here in terms of breakdowns of the electronic population into partial and total ``gross atomic populations,'' or into partial and total ``net atomic populations'' together with ``overlap populations.'' ``Gross atomic populations'' distribute the electrons almost perfectly among the various AOs (atomic orbitals) of the various atoms in the molecule. From these numbers, a definite figure is obtained for the amount of promotion (e.g., from 2s to 2p) in each atom; and also for the gross charge Q on each atom if the bonds are polar. The total overlap population for any pair of atoms in a molecule is in general made up of positive and negative contributions. If the total overlap population between two atoms is positive, they are bonded; if negative, they are antibonded. Tables of gross atomic populations and overlap populations, also gross atomic charges Q, computed from SCF (self-consistent field) LCAO-MO data on CO and H2O, are given. The amount of s-p promotion is found to be nearly the same for the O atom in CO and in H2O (0.14 electron in CO and 0.15e in H2O). For the C atom in CO it is 0.50e. For the N atom in N2 it is 0.26e according to calculations by Scherr. In spite of very strong polarity in the π bonds in CO, the σ and π overlap populations are very similar to those in N2. In CO the total overlap population for the π electrons is about twice that for the σ electrons. The most easily ionized electrons of CO are in an MO such that its gross atomic population is 94% localized on the carbon atom; these electrons account for the (weak) electron donor properties of CO. A comparison between changes of bond lengths observed on removal of an electron from one or another MO of CO and H2, and corresponding changes in computed overlap populations, shows good correlation. Several other points of interest are discussed.

Barik R., Das J., Nanda S.

We herein disclose the synthesis of fully functionalized [5,1,0] ring system consisting of cycloheptane core fused with cyclopropane unit of naturally occurring sesquiterpene capillosanane V. Initially, an unsuccessful RCM reaction...

Sasaki M., Ohba M., Murakami A., Umehara A.

Antonova Alexandra S., Zubkov Fedor I.

Catalytic olefin metathesis using Hoveyda-Grubbs type ruthenium complexes is a powerful tool for creating complex molecules possessing a variety of practically useful properties. This method is also applied for obtaining modern polymer materials from low-demand petroleum products. Among all ruthenium complexes containing five- or six-membered chelate rings, the commercially available HG-II catalyst is the most common. In addition, other Hoveyda-Grubbs type complexes, which include a Het→Ru donor–acceptor bond in the chelate ring, often exhibit metathesis activity equal to or superior to that of HG-II. This review considers second-generation N-heterocyclic ruthenium carbene Hoveyda-Grubbs type complexes with donor–acceptor bonds such as O→Ru, S→Ru, Se→Ru, N→Ru, P→Ru and Hal→Ru in the chelate ring. Methods of preparation, analysis of stability and catalytic activity of such complexes are compared, and examples of the application of these organometallic ruthenium derivatives in the synthesis of practically relevant products are provided. The literature from 2010 to 2023 is summarized, making this review useful for a broad audience of chemists working in heterocyclic and organometallic chemistry, as well as practitioners involved in the production of catalysts and polymers.The bibliography includes 174 references.

Odewole O.A., Swart M.R., Erasmus E.

Olefin metathesis catalysts by Schrock and Grubbs have witnessed tremendous success as it has led to the development of several metathesis transformations. However, the use of additives in olefin metathesis reactions which employs the commercially available Schrock's or Grubbs's catalyst has been investigated. It has resulted in better catalyst performance, catalyst stability, suppression of other non-metathetic reactions like olefin isomerization, self-metathesis and improved desired metathesis product yield. This survey will firstly highlight some types of metathesis reactions, followed by a brief overview of the Schrock's and Grubbs's catalysts and then enumerate the influence of additives as co-catalyst on the activity and selectivity of the specified available olefin metathesis catalyst.

Sivakumar V., Watile R.A., Colacot T.J.

Die Bedeutung der Organometallchemie für die Entwicklung organischer Prozesse wird kurz aus historischer Sicht dargestellt, damit die Leser den Inhalt dieses speziellen Bandes schätzen können. Neben der Hervorhebung bekannter Namen wurde ein Abschnitt den aufkommenden Technologien gewidmet, in der Hoffnung, dass einige dieser Technologien innerhalb weniger Jahre zu realen Anwendungen reifen könnten. Beispiele hierfür sind Photokatalyse, Fließchemie, elektroorganische Synthese und computergestützte Vorhersagen.

Rao W., Li Y., Jiang L., Gao C., Wang Y., Liu J., Zhou F., Zou G., Cao X.

Purohit V.B., Pięta M., Pietrasik J., Plummer C.M.

Over the past century the advancement of polymer chemistry has provided civilization with a plethora of plastic products that have significantly contributed to day-to-day life and the general well-being of humanity. However, the disposal of used plastic has led to an accumulation of plastic waste in the environment which can destroy fragile ecosystems. It is therefore imperative that viable alternatives to the presently used non–degradable polymers are developed. Two emerging approaches for addressing the contemporary plastic waste crisis are the development of degradable and chemically recyclable polymers. Among the various polymerization techniques, ring–opening metathesis polymerization (ROMP) remains a viable candidate for the design and preparation of such next-generation polymers. Within this review article an overview is presented regarding the history, mechanism and catalyst developments in ROMP, detailing significant developments over the previous decades which reassert the importance of ROMP in designing advanced polymers. Moreover, this article aims to explore the chemistry involved in ROMP by summarizing the state-of-the-art, as well as providing an overview of the fundamental challenges involved in synthesizing such next-generation polymers, including potential future directions.

Talcik J., Serrato M., Del Vecchio A., Colombel-Rouen S., Morvan J., Roisnel T., Jazzar R., Melaimi M., Bertrand G., Mauduit M.

The synthesis of ruthenium-complexes with cyclic (amino)(barrelene)carbenes (namely CABCs) as ligand is reported. Isolated in moderate to good yields, those new complexes showed an impressive thermal stability at 110 °C...

Cheng-Sánchez I., Moya-Utrera F., Sarabia F.

Kotha S., Mehta G.

Deng M., Wilde M., Welch J.T.

Barteczko N., Brzęczek-Szafran A., Wolny A., Jurczyk S., Jakubik-Kolon A., Chrobok A.

Supported olefin metathesis catalysts have attracted considerable interest for over two decades, regarding their facile separation, reusability and decreased product contamination. In this study two strategies toward synthesis of heterogeneous ruthenium-catalyst were explored using supported ionic liquid phase (SILP) and supported ionic liquid-like phase (SILLP) with multi-walled carbon nanotubes (MWCNTs) as a support. The structure of ionic liquids used for the construction of catalysts was varied regarding length of alkyl chain and anion in terms of providing influence on catalytic activity and stability as well as reaction product contamination. The activity of prepared catalysts was tested in ring-closing metathesis (RCM). The Ru-based SILLP catalyst demonstrated high performance (conversions >90 % in five reaction cycles), compared to SILP and [email protected] catalyst synthesized using unmodified MWCNTs, additionally decreasing the product contamination with Ru (14 ppm).

Ishizuka H., Nureki A., Adachi K., Takayanagi Y., Odagi M., Yotsu-Yamashita M., Nagasawa K.

Liu J., Jia M., Yuan F., Hong Z., Tong W., Zheng C., Wang C., Wang H.

AbstractHydrogenated nitrile butadiene rubber (HNBR) is a high‐performance elastomer widely used in the petrochemical and automotive industries. A ruthenium‐based catalyst, namely [1,3‐bis(2,4,6‐trimethylphenyl)‐2‐imidazolidinylidene]‐[2‐[[(4‐methylphenyl)imino]methyl]‐4‐nitrophenoyl]chloro[3‐phenylindenylidene]ruthenium(II) (M41), was investigated for the direct hydrogenation of NBR latex. The catalytic selectivity for the hydrogenation of CC bond instead of CN group was confirmed by both Fourier transform infrared and 1H NMR spectroscopies. The effects of reaction conditions (such as temperature, pressure, catalyst levels, agitation speed and solid content) on the hydrogenation reaction were examined, and hydrogenation products with over 95 mol% conversion were obtained for only 3 h with a catalyst/NBR ratio of 0.05 wt% and no gel was formed within HNBR. The results suggest that the current limitations in the hydrogenation of NBR latex could be addressed with this catalyst. © 2023 Society of Industrial Chemistry.

Ou X., Occhipinti G., Boisvert E.Y., Jensen V.R., Fogg D.E.