Enantioselective Olefin Metathesis Research Articles

Challenges and Breakthroughs in Z‐Enantioselective Olefin Metathesis

AbstractAsymmetric Olefin Metathesis (AOM) represents a highly versatile synthetic tool to lead to relevant chiral building blocks with excellent enantiopurity. As the Z‐alkene moiety is ubiquitous in a wide range of natural products, the development of catalysts which are able to control both the Z‐selectivity and the enantioselectivity of metathesis transformations is in high demands. This review aims to provide a comprehensive overview covering all the breakthroughs accomplished in the field of challenging Z‐enantioselective olefin metathesis, which is of interest in the total synthesis of complex molecules.

Ambivalent Role of Rotamers in Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Enantioselective Ring-Opening Cross-Metathesis

The development of highly efficient enantioselective olefin metathesis catalysts is a significant challenge. Using optically pure chiral cyclic (alkyl)(amino)carbene (ChiCAAC) ligands combined with preliminary mechanistic insights and density functional theory (DFT) computations, we show that catalytic performances in this field can be impaired by the formation of rotamers before the enantio-determining step. Using DFT, we also demonstrate that these results can help accelerate the process of ligand discovery by providing faster methods to discriminate potential candidates.

Catalyst for Enantioselective Olefin Metathesis

Catalyst for Enantioselective Olefin Metathesis

ChemInform Abstract: Enantioselective Olefin Metathesis with Cyclometalated Ruthenium Complexes.

AbstractEnantioenriched complexes incorporating cyclometalated NHC ligands catalyze (Z)‐ and enantioselective asymmetric ring opening/cross metathesis reactions of norbornenes and cyclobutenes, and the difference in ring strain between these two compounds leads to different propagating species in the catalytic cycle.

Enantioselective olefin metathesis with cyclometalated ruthenium complexes.

The success of enantioselective olefin metathesis relies on the design of enantioenriched alkylidene complexes capable of transferring stereochemical information from the catalyst structure to the reactants. Cyclometalation of the NHC ligand has proven to be a successful strategy to incorporate stereogenic atoms into the catalyst structure. Enantioenriched complexes incorporating this design element catalyze highly Z- and enantioselective asymmetric ring opening/cross metathesis (AROCM) of norbornenes and cyclobutenes, and the difference in ring strain between these two substrates leads to different propagating species in the catalytic cycle. Asymmetric ring closing metathesis (ARCM) of a challenging class of prochiral trienes has also been achieved. The extent of reversibility and effect of reaction setup was also explored. Finally, promising levels of enantioselectivity in an unprecedented Z-selective asymmetric cross metathesis (ACM) of a prochiral 1,4-diene was demonstrated.

ChemInform Abstract: Catalytic Enantioselective Olefin Metathesis and Natural Product Synthesis

AbstractReview: 18 refs.

ChemInform Abstract: Catalytic Enantioselective Olefin Metathesis in Natural Product Synthesis. Chiral Metal‐Based Complexes that Deliver High Enantioselectivity and More

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic Enantioselective Olefin Metathesis in Natural Product Synthesis. Chiral Metal‐Based Complexes that Deliver High Enantioselectivity and More

Chiral olefin metathesis catalysts enable chemists to access enantiomerically enriched small molecules with high efficiency; synthesis schemes involving such complexes can be substantially more concise than those that would involve enantiomerically pure substrates and achiral Mo alkylidenes or Ru-based carbenes. The scope of research towards design and development of chiral catalysts is not limited to discovery of complexes that are merely the chiral versions of the related achiral variants. A chiral olefin metathesis catalyst, in addition to furnishing products of high enantiomeric purity, can offer levels of efficiency, product selectivity and/or olefin stereoselectivity that are unavailable through the achiral variants. Such positive attributes of chiral catalysts (whether utilized in racemic or enantiomerically enriched form) should be considered as general, applicable to other classes of transformations.

The Significance of Degenerate Processes to Enantioselective Olefin Metathesis Reactions Promoted by Stereogenic-at-Mo Complexes

The present study provides spectroscopic and experimental evidence demonstrating that degenerate metathesis is critical to the effectiveness of this emerging class of chiral catalysts. Isolation and X-ray characterization of both diastereomeric complexes, as well as an examination of the reactivity and enantioselectivity patterns exhibited by such initiating neophylidenes in promoting ring-closing metathesis processes, are disclosed. Only when sufficient amounts of ethylene are generated and inversion at Mo through degenerate processes occurs at a sufficiently rapid rate is high enantioselectivity achieved, irrespective of the stereochemical identity of the initiating alkylidene (Curtin-Hammett kinetics). With diastereomeric metal complexes that undergo rapid interconversion, stereomutation at the metal center becomes inconsequential, and stereoselective synthesis of a chiral catalyst is not required.

Enantioselective Synthesis of P‐Stereogenic Phosphinates and Phosphine Oxides by Molybdenum‐Catalyzed Asymmetric Ring‐Closing Metathesis

Chiral phosphines have found widespread use in chemical synthesis as ligands for transition metal catalysis.[1] Along with phosphine oxides and other derivatives, they have also become popular choices as catalysts in organic synthesis.[2] Organophosphorus-based catalysis will undoubtedly benefit from a more diverse range of P-stereogenic phosphines. In response to this demand, metal-catalyzed asymmetric syntheses of P-stereogenic phosphines and their derivatives have recently emerged, with key contributions including alkyne hydrophosphorylation,[3] the alkylation and arylation of secondary phosphines,[4] enantioselective deprotonation,[5] and rhodium-catalyzed [2+2+2] cycloaddition.[6] To date, these catalytic enantioselective routes remain largely outnumbered by well-established methods based on resolutions[7] or on the use of chiral auxiliaries.[8] In spite of recent advances in the area of olefin metathesis, the utility of asymmetric ring-closing metathesis (ARCM)[9] has not been applied to the preparation of P-stereogenic phosphine derivatives.[10] In light of literature precedents, which demonstrate that various P-containing dienes, trienes, and tetraenes are suitable substrates for olefin metathesis,[11] we reasoned that the ARCM of P-templates would be a strategically unique and valuable reaction for the preparation of P-stereogenic compounds. We opted for a catalytic enantioselective desymmetrization process of prochiral P-templates, as this approach offers the opportunity to explore ARCM with the chirality arising from the formation of a stereogenic center other than a carbon atom (Scheme 1). Moreover, the resulting products are structurally novel P-stereogenic scaffolds amenable to rich chemistry further downstream. Herein, we report the first examples of catalytic enantioselective olefin metathesis reactions of phosphinates and phosphine oxides, which lead to the formation of five-, six-, and seven-membered P-heterocycles in up to 98% ee. We also report an unprecedented case of complementary asymmetric induction in reactions promoted by a pair of chiral molybdenum-based complexes differing structurally in their achiral imido ligand.

A Highly Active Chiral Ruthenium‐Based Catalyst for Enantioselective Olefin Metathesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A Highly Active Chiral Ruthenium-Based Catalyst for Enantioselective Olefin Metathesis

A chiral Ru-based olefin metathesis catalyst bearing a chiral NHC ligand that is both C1-symmetric and monodentate is described. The catalyst shows increased reactivity in comparison to existing chiral Ru-based catalysts that possess a C2-symmetric NHC and successfully induces asymmetry in desymmetrization reactions.

A Readily Available Chiral Ag-Based N-Heterocyclic Carbene Complex for Use in Efficient and Highly Enantioselective Ru-Catalyzed Olefin Metathesis and Cu-Catalyzed Allylic Alkylation Reactions

A new chiral bidentate N-heterocyclic carbene (NHC) ligand has been designed and synthesized. The NHC ligand bears a chiral diamine backbone and an achiral biphenol group; upon metal complexation (derived from Ag(I), Ru(II), or Cu(II)), the diamine moiety induces >98% diastereoselectivity such that the biaryl unit coordinates to the metal center to afford the desired complex as a single atropisomer. Because the ligand does not require optically pure biaryl amino alcohols, its synthesis is significantly shorter and simpler than the related first generation ligands bearing a chiral binaphthyl-based amino alcohol. The chiral NHC ligand can be used in the preparation of highly effective Ru- and Cu-based complexes (prepared and used in situ from the Ag(I) carbene) that promote enantioselective olefin metathesis and allylic alkylations with scope that is improved from previously reported protocols. In many cases, transformations promoted by the chiral NHC-based complexes proceed with higher enantioselectivity and reactivity than was observed with previously reported complexes.

Supported Chiral Mo‐Based Complexes as Efficient Catalysts for Enantioselective Olefin Metathesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Supported chiral Mo-based complexes as efficient catalysts for enantioselective olefin metathesis.

Syntheses and catalytic activities of seven new polymer-supported chiral Mo-based complexes are disclosed. Four of the complexes are polystyrene-based, and three involve polynorbornene supports. Studies concerning the ability of the polymer-bound chiral complexes to promote an assortment of asymmetric ring-closing (ARCM) and ring-opening (AROM) metathesis reactions are detailed. In many instances, levels of reactivity and enantioselectivity are competitive with those of the analogous homogeneous catalysts. The positive effect of lower cross-linking within the polymer backbone on reaction efficiency and asymmetric induction is detailed. The optically enriched products obtained through the use of the supported complexes, after simple filtration and removal of the supported Mo catalysts, contain significantly lower levels of metal impurities as compared to products synthesized with the corresponding homogeneous catalysts.

Catalytic Asymmetric Olefin Metathesis

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis in Air [J. Am. Chem. Soc. 2002, 124, 4954−4955

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionA Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis in Air [J. Am. Chem. Soc.2002, 124, 4954−4955].Joshua J. Van Veldhuizen, Steven B. Garber, Jason S. Kingsbury, and Amir H. HoveydaCite this: J. Am. Chem. Soc. 2003, 125, 41, 12666Publication Date (Web):September 13, 2003Publication History Published online13 September 2003Published inissue 1 October 2003https://doi.org/10.1021/ja033454fCopyright © 2003 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views910Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (16 KB) Get e-Alerts Get e-Alerts

An Enantiomerically Pure Adamantylimido Molybdenum Alkylidene Complex. An Effective New Catalyst for Enantioselective Olefin Metathesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An enantiomerically pure adamantylimido molybdenum alkylidene complex. An effective new catalyst for enantioselective olefin metathesis.

An enantiomerically pure Mo-based complex that bears an alkylimido ligand is prepared and characterized through NMR spectroscopy and X-ray analysis. Mo complex 4 is the only reported chiral alkylimido catalyst; all previous chiral complexes are arylimido systems. These studies show that the chiral Mo catalyst exists exclusively as the syn isomer and that it offers unique reactivity and selectivity profiles in asymmetric olefin metathesis.

Enhancement of Enantioselectivity by THF in Asymmetric Mo‐Catalyzed Olefin Metathesis. Catalytic Enantioselective Synthesis of Cyclic Tertiary Ethers and Spirocycles.

AbstractFor Abstract see ChemInform Abstract in Full Text.