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The ring-closing metathesis of N-(γ-fluoroallyl)-3-butenamides provides unsaturated fluoro δ-lactams in high yields, which are suitable synthetic intermediates of fluoro pseudopeptides.

We report a convenient synthesis of carbazole-1,4-quinone alkaloid koeniginequinones A and B using a tandem ring-closing metathesis with the dehydrogenation reaction sequence under an O2 atmosphere as an important step. Using this method, carbazole-1,4-quinones substituted at the 5-, 6-, 7-, and/or 8-positions have been synthesized. Moreover, 24 compounds, including koeniginequinones A and B, have been evaluated for their antiproliferative activity against HCT-116 and HL-60 cells, and the 6-nitro analog exhibited the most potent activity against both tumor cell types.

Azonia aromatic heterocycles are an important subclass of aza-heterocyles as they are the structural motif of relevant cationic alkaloids, and they have a wide range of potential applications such as bioactive compounds and organic materials. In this Synopsis, recent and novel approaches to their synthesis are surveyed, with particular emphasis on ring-closing metathesis reactions and annulation reactions based on C–H activation.

Exploiting catalytic carbonyl-olefin metathesis is an ongoing challenge in organic synthesis. Reported herein is an FeCl3 -catalyzed ring-closing carbonyl-olefin metathesis. The protocol allows access to a range of carbo-/heterocyclic alkenes with good efficiency and excellent trans diastereoselectivity. The methodology presents one of the rare examples of catalytic ring-closing carbonyl-olefin metathesis. This process is proposed to take place by FeCl3 -catalyzed oxetane formation followed by retro-ring-opening to deliver metathesis products.

In this communication, a concise and efficient synthetic route for the synthesis of decarestrictine J in enantioselective way has been described. In this synthesis, Yamaguchi esterification and ring closing metathesis (RCM) for macrocyclic ring formation have been applied as key steps.

A kinetically controlled Z-selective cross-metathesis yielding α,β-unsaturated esters is presented.

The total synthesis of (−)-conduramine A-1 was achieved by using a diastereomerically enriched syn , anti -oxazine intermediate. The key steps in this strategy were the stereoselective extension of the chirality of syn , anti -oxazine, a Wittig reaction, and a ring-closing metathesis reaction.

The temporary silicon-tethered ring-closing metathesis of chiral non-racemic allylic and homoallylic alcohols affords unsymmetrical Z -configured trisubstituted olefins that readily undergo stereoselective hydroboration and dihydroxylation to provide a novel approach to masked polypropionate and polyol fragments present in an array of biologically important natural products. For example, this strategy provides a convenient method for the construction of polyol fragments relevant to the secondary metabolites amphidinol 3 and lophodiol A, which have antifungal and cytotoxic activity, respectively.

This third review in a series involving reactions of hydrosilanes and transition metal complexes and characterization of the products covers the period 2009 thru 2013. After a brief discussion of other synthetic methods used for the formation of Si-TM complexes, Section 3 provides an extended discussion of the types of ligands and metal complexes used as reactants with hydrosilanes. The increase in use of pincer ligands in forming stable, isolable complexes is featured. Three tables list the complexes reported for primary, secondary, and tertiary silanes. Many reactions leading to SiTM complexes are initiated by loss of a ligand prior to oxidative addition of the hydrosilane or by a metathesis reaction. Structural data are tabulated for the isolated complexes and provide the Si-TM bond ranges for the elements in the “d” block. A major section on nonclassical (σ or agostic) complexes includes two general groupings with Si–H···TM and M–H···Si interactions. A section on solution processes identified by NMR s...

A plethora of strategies for immobilizing well-defined metathesis catalysts on solid supports have been developed over the past decades. Whereas most reviews on classical heterogeneous metathesis catalyst designs mainly discuss covalent binding approaches, we here extended this topic with non-covalent surface science methods, a research area that gained interest recently. Within this context, the main focus was set on the immobilization of ruthenium alkylidenes or so-called Grubbs complexes, as these catalysts are known for their high activity, stability and commercial viability. Besides giving an overview of different immobilization strategies, the wide diversity of supported Grubbs catalysts also allows for discussing implications of attaching Grubbs catalysts that go beyond the traditional benefits of heterogeneous catalysis, such as easy catalyst separation. More specifically, this Review will summarize several unique opportunities of immobilized homogeneous catalysts in liquid-phase metathesis transformations in terms of impact on activity, stability, and product selectivity, as to highlight the economic potential, but without ignoring possible shortcomings and limitations.

A cost-efficient method for the preparation of a series of N-substituted 2-fluoroallylamines and their application in the synthesis of fluoroalkene-containing lactams are described. N-substituted 2-fluoroallylamine could be readily synthesized from methyl 2-fluoroacrylate via aminolysis and subsequently selective reduction of the amide group. These amines were further converted into the corresponding amides with diverse acids bearing a terminal double bond. The Ring-Closing Metathesis (RCM) of the resulting amides led to the formation fluorovinyl-containing lactams in good yields.

The incorporation of organometallic catalyst precursors in proteins results in so-called artificial metalloenzymes. The protein structure will control activity, selectivity and stability of the organometallic site in aqueous medium and allow non-natural reactions in biological settings. Grubbs-Hoveyda type ruthenium catalysts with an N-heterocyclic carbene (NHC) as ancillary ligand, known to be active in olefin metathesis, have recently been incorporated in various proteins. An overview of these artificial metalloproteins and their potential application in olefin metathesis is given.

Recent developments in catalytic carbonyl-olefin metathesis are summarized in this Highlight. Schindler and co-workers have reported that the environmentally benign FeCl3 catalyst promotes ring-closing carbonyl-olefin metathesis (RCCOM) in high yield under very mild conditions.

A tandem olefin metathesis/oxidative cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific oxidative cyclization.

In the past decade, numerous examples of chemical technologies based on olefin metathesis have been developed to make olefin metathesis increasingly dominant in several sustainable and green chemical processes. In spite of the wide application profile, conjugated olefin metathesis, especially conjugated polyene metathesis, is an area of great interest with little exploration. The metathesis of conjugated polyenes is often cumbersome and requires a high catalyst loading, most probably because of the formation of poorly active or inactive ruthenium η3-vinylcarbene intermediates. A mechanistic understanding and the development of a new highly active catalytic system for olefin metathesis will open new areas for exploration, such as the utilisation of cyclopentadiene and other petrochemical by-products or a new way to use butadiene, isoprene and conjugated electron systems that contain natural products such as terpenes and polyunsaturated fatty acids. An understanding of the mechanism of ruthenium η1–η3-vinylcarbene interconversion may open the way to the development of a new generation of Ru-based latent metathesis catalyst systems. This review summarises the most relevant pioneering work focused on the metathesis of conjugated polyenes to open new ideas for the development of forthcoming latent metathesis catalysts and to explore different applications.

Alkyne metathesis catalysts composed of molybdenum(VI) propylidyne and multidentate tris(2-hydroxylbenzyl)methane ligands have been developed, which exhibit excellent stability (remains active in solution for months at room temperature), high activity, and broad functional-group tolerance. The homodimerization and cyclooligomerization of monopropynyl or dipropynyl substrates, including challenging heterocycle substrates (e.g., pyridine), proceed efficiently at 40-55 °C in a closed system. The ligand structure and catalytic activity relationship has been investigated, which shows that the ortho groups of the multidentate phenol ligands are critical to the stability and activity of such a catalyst system.

An asymmetric carbene cascade reaction, which proceeds through carbene/alkyne metathesis and formal (3+2) cycloaddition and converts alkynyl-tethered enol diazoacetates to chiral bicyclic cyclopentadienes, is presented; and no catalytic asymmetric version of these carbene cascade transformations has been disclosed so far. The proton signals of the cyclopropene intermediates are observed in the mechanism study, which clearly demonstrate the reaction pathways. In addition, these products are intercepted via Diels–Alder reactions to provide bridged polycyclic structures in high yields and enantioselectivities.

A facile and efficient strategy for the synthesis of α,β-unsaturated lactams through ring-closing metathesis of easily prepared diene amides is being reported here. Reaction conditions were optimized for metathetic cyclization of diene amides to obtain five- to sevenmembered unsubstituted and β-substituted α,β-unsaturated lactams in good to excellent yield.

The synthesis of enantiomerically enriched 7- and 8-hydroxy­stearic acids (7- and 8-HSA) has been successfully accomplished starting from chiral nonracemic 1-pentadecen-4-ol and 1-tetradecen-4-ol, respectively. Their Yamaguchi’s esterification with 4-pentenoic and 5-hexenoic acids, respectively, afforded the suitable dienic esters which were submitted to ring-closing metathesis reaction. After hydrogenation and basic hydrolysis of the complex reaction mixture, chiral nonracemic 7- and 8-HSA were obtained in about 40% total yield.

Today there are many types of transition-metal-catalyzed carbon–carbon bond-forming reactions. Of these, the olefin metathesis has made possible a wide range of transformations with commercially available and easily handled catalysts. Olefin metathesis is widely considered as one of the most powerful synthetic tool in organic chemistry. During the last 20 years many new catalysts with excellent selectivity and efficiency have been developed, also to be used in solid phase organic chemistry protocols. The understanding of the mechanisms and interactions between the catalyst and substrate has resulted that an increasing number of research groups have employed these reactions in multistep procedures and in the synthesis of active pharmaceutical ingredients and natural products. Although the olefin metathesis reaction still proceeds better in homogeneous phase, some structural modifications of the catalyst and new approaches for immobilization have provided interesting possibilities towards more efficient use also in heterogeneous phase. To celebrate 10 years since the Nobel Prize in Chemistry given to Yves Chauvin, Richard Schrock and Robert Grubbs for the “development of the metathesis method in organic synthesis” and to summarize recent results obtained in the field of solid phase metathesis chemistry this short review was written.

In the past two decades, alkene metathesis has risen in prominence to become a significant synthetic strategy for alkene formation. Many total syntheses of natural products have used this transformation. We review the use, from 2003 to 2015, of ring-closing alkene metathesis (RCM) for the generation of dihydrofurans or -pyrans in natural product synthesis. The strategies used to assemble the RCM precursors and the subsequent use of the newly formed unsaturation will also be highlighted and placed in context.

A straightforward approach toward enantioenriched α-substituted α,β-unsaturated δ-lactams is described. Although a considerable number of approaches toward α,β-unsaturated δ-lactams have been reported, there are relatively few examples of enantioenriched α,δ-disubstituted α,β-unsaturated δ-lactams formation. The δ-stereocenter was formed by addition of allylmagnesium bromide to an N-tert-butylsulfinyl imine. The α,β-unsaturated δ-lactam was furnished by ring-closing metathesis. Although Baylis–Hillman chemistry failed on this cyclic compound, introduction of the hydroxyethyl group prior to ring-closing metathesis was successful. A Baylis–Hillman reaction was used to introduce the substituent at the α-position of the α,β-unsaturated lactam.

Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value.

A highly efficient 12-step synthesis of the marine alkaloid (-)-nakadomarin A has been accomplished. The key advanced intermediate, a tetracyclic ketone derivative, was constructed in just seven steps using a sequence that includes an asymmetric Pauson-Khand reaction, an Overman rearrangement reaction, a ring-closing metathesis reaction, and an amination reaction. Late introduction of the furan ring during the synthesis of (-)-nakadomarin A means that the key tetracyclic ketone derivative has the potential to serve as an advanced intermediate for the synthesis of related marine alkaloids.

A concise and simple synthetic approach to cis-syn-cis-triquinanes and -propellanes has been demonstrated via olefin metathesis starting with exo-nadic anhydride. This approach involves a ring-opening and ring-closing metathesis sequence of norbornene derivatives using Grubb’s catalyst. Early-stage diallylation of norbornene derivatives is demonstrated followed by ring-closing metathesis that delivers propellanes exclusively. Surprisingly, ring-opening metathesis, late-stage diallylation, followed by ring-closing metathesis delivers triquinane as well as propellane derivatives.

The nitridosilicate chloride Ba1.63La7.39Si11N23Cl0.42:Ce3+ was synthesized by metathesis reaction starting from LaCl3, BaH2, CeF3 and the product of the ammonolysis of Si2Cl6. The title compound is stable towards air and moisture. Diffraction data of a microcrystal were recorded using microfocused synchrotron radiation. X-ray spectroscopy confirms the chemical composition of the crystal. IR spectra corroborate absence of N-H bonds. The compound is homeotypic to Ba2Nd7Si11N23 and crystallizes in space group Cmmm with a = 11.009(3), b = 23.243(8), c = 9.706(4) angstrom and Z = 4, R-1(all) = 0.0174. According to bond valence sum calculations, some crystallographic positions show complete occupancy by Ba or La whereas others contain significant amounts of both elements. In contrast to the structure prototype Ba2Nd7Si11N23, Ba1.63La7.39Si11N23Cl0.42:Ce3+ contains chloride ions in channels of the SiN4 tetrahedra network, hinting at various substitution possibilities of the complex zeolite-like structure.

Herein, we report the successful transformation of a 1(st) generation Grubbs metathesis catalyst into an asymmetric transfer hydrogenation (ATH) catalyst. Upon addition of a chiral amine ligand, an alcohol and a base, the 1(st) generation Hoveyda-Grubbs catalyst (HG-I) was found to promote the enantioselective reduction of acetophenone to 1-phenylethanol. After optimizing the order of addition and the reaction conditions, the substrate scope was assessed leading to enantiomeric excesses up to 97% ee. NMR experiments were run in order to get information about the in situ-generated ATH catalyst. Furthermore, the possibility to perform olefin metathesis and ketone transfer hydrogenation sequentially in one pot was demonstrated, and the first tandem olefin metathesis-ketone asymmetric transfer hydrogenation was carried out.

A silica-supported ionic liquid phase catalyst containing Keggin-type anion has been prepared by covalent grafting of ferrocene-tagged ionic liquid in a matrix of silica followed by anion metathesis reaction. This novel catalyst served as a robust heterogeneous catalyst for the synthesis of biologically active sulfonamides from 4-toluenesulfonyl chloride and amines. Additionally, recycling experiments showed that the catalyst could be reused five times. Copyright © 2015 John Wiley & Sons, Ltd.

The synthesis of a new type of Hoveyda-Grubbs 2(nd) generation catalyst bearing a modified N-heterocyclic carbene ligands is reported. The new catalyst contains an NHC ligand symmetrically substituted with chromanyl moieties. The complex was tested in model CM and RCM reactions. It showed very high activity in CM reactions with electron-deficient α,β-unsaturated compounds even at 0 °C. It was also examined in more demanding systems such as conjugated dienes and polyenes. The catalyst is stable, storable and easy to purify.

The preparation of new allylphosphonates and allylphosphoramidates bearing alkoxycarbonyl substituents is described. Both P-based precursors were subjected to RCM. In this context, several Ru-based catalysts were tested and compared in order to prepare new oxa- and aza-dihydrophosphinine oxides. P-heterocycles and homodimers have been obtained depending on the nature of the catalyst and the reaction conditions. In addition, homodimers were converted into six-membered cyclic phosphonates and phosphoramidates under Ru-promoted conditions.

N-Alkyl-N-(2-vinylbenzyl)prop-2-en-1-amine derivatives undergo a one-pot olefin isomerization/aliphatic enamine ring-closing metathesis (RCM)/oxidation/1,3-dipolar cycloaddition sequence with the ruthenium complex, Ru(CO)HCl(PPh3)3, a second generation Hoveyda–Grubbs catalyst, and a 1,3-dipolarophile. Overall, in a single operation the reaction sequence converts simple benzylamine derivatives into isoindolo[1,2-a]isoquinolines with a π-conjugated four-ring system, through three unique ruthenium-catalyzed transformations.

Aprocess for the assembly of carbazole alkaloids has been developed on the basis of ring-closing metathesis (RCM) and ringrearrangement-aromatization (RRA) as the key steps. This method is based on allyl Grignard addition to isatin derivatives to provide smooth access to 2,2-diallyl 3-oxindole derivatives through a 1,2-allyl shift. The diallyl derivatives were used as RCM precursors to afford a novel class of spirocyclopentene-3-oxindole derivatives, which underwent a novel RRA reaction to afford carbazole derivatives. The synthetic sequence to carbazoles was shortened by combining the RCM and RRA steps in an orthogonal tandem catalytic process. The utility of this methodology was further demonstrated by the straightforward synthesis of carbazole alkaloids, including amukonal derivative, girinimbilol, heptaphylline, and bis(2-hydroxy-3-methylcarbazole).

The new title compound is prepared by solid state metathesis reaction of MgCl2, GaN, Li3N, and Li3BN2 in the molar ratio of 3:1:1:1 (Nb ampule, 1100 °C, 48 h).

The new Hoveyda-Grubbs type ruthenium carbene catalyst exhibits excellent performance for both ring-closing and cross metathesis reactions.

The synthesis of crystals of a zinc- and tin-based earth-abundant element nitride (ZnSnN2) semiconductor was successfully achieved via a metathesis reaction under high pressure. Pressures exceeding 5.5 GPa were required to obtain single-phase crystals. The material's bandgap was determined to be 1.4 eV, which is ideal for photovoltaic absorbers and visible light-active photocatalysts. The decomposition temperature of the material was estimated to be approximately 350‒400 °C at atmospheric pressure. Finally, the chemical stability of the material against alkali and acid solutions was sufficient for photovoltaic and photocatalytic applications.

A deconjugative electrophilic fluorodesilylation is accomplished for the first time by reacting γ-silyl-butenamides.

A series of phenylene vinylene macrocycles (PVMs) bearing substituents with various sizes and electronic properties have been synthesized through a one-step acyclic diene metathesis macrocyclization approach and their aggregation behaviors have been investigated. In great contrast to the aggregation of the analogous phenylene ethynylene macrocycles, which aggregate only when substituted with electron-withdrawing groups, these PVMs undergo exceptionally strong aggregation, regardless of the electron-donating or -withdrawing characters of the substituents. The unusual aggregation behavior of the PVMs is further investigated with thermodynamic and computer modeling studies, which show a good agreement with the recently proposed direct through-space interaction model, rather than the polar/π model. The high aggregation tendency of PVMs suggests the great potential of this novel class of shape-persistent macrocycles in a variety of applications, such as ion channels, host-guest recognition, and catalysis.

Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions.

This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials.

Ring-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008-2014).

The ability of 2-p-tolylbenzyl carbanions to behave as a source of chiral benzylic nucleophiles has been shown in its reaction with fluorinated imines. The process takes place with high levels of stereocontrol, rendering the corresponding amines as single diastereoisomers. Subsequent cross-metathesis followed by intramolecular aza-Michael reaction makes the synthesis of fluorinated homoproline derivatives bearing three stereogenic centers possible. Furthermore, the selectivity of the cyclization process can easily be tuned up in a diastereodivergent manner simply by changing the reaction conditions.

Triene substrates containing an (E)-dibromo-tetrasubstituted alkene moiety participate in selective ene-ene ring-closing metathesis reactions.

A series of 2,5-disubstituted pyrrolidines was synthesized through an efficient telescoped cross-metathesis/cyclizing aza-Michael addition involving N-heteroaromatic olefinic derivatives. This synthetic route was applied to the preparation of original nicotine–lobeline, nicotine–pelletierine and lobeline–nicotine–epibatidine hybrids.

α-Mn(BH4)2 is prepared by high—energy ball milling of stoichiometric amounts of LiBH4 and MnCl2 or by metathesis reaction of the latter precursors in Et2O to yield NaMn2(BH4)2·2Et2O followed by desolvation under vacuum at 110 °C.