The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• Yuya A. Lin Benjamin G. Davis Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom 10.3762/bjoc.6.140 Abstract Olefin metathesis has emerged as a powerful tool in organic synthesis. The activating effect of an allylic

• examples of such a reaction on proteins. This led to a new benchmark in substrate complexity for cross-metathesis and expanded the potential of olefin metathesis for other applications in chemical biology. The enhanced reactivity of allyl sulfide, along with earlier reports of a similar effect by allylic

• hydroxy groups, suggests that allyl chalcogens generally play an important role in modulating the rate of olefin metathesis. In this review, we discuss the effect of allylic chalcogens in olefin metathesis and highlight its most recent applications in synthetic chemistry and protein modifications

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• catalysts show similar activity in cross metathesis reactions. Keywords: homogeneous catalysis; N-heterocyclic carbenes; olefin metathesis; pyridine ligand; Ruthenium carbene complexes; Introduction Over the past two decades, the olefin metathesis reaction became one of the most important C–C-bond forming

• are significantly lower and yields exceed 50% only in few cases such as 4b, 4e and 4f. A particularly difficult substrate for olefin metathesis reactions is acrylate 3g, which has recently been used by us as an intermediate in the synthesis of the natural product (–)-cleistenolide [51]. Acrylate 3g

• recently observed a considerable reduction of isomerization side reactions if acrylates are present during a metathesis reaction. Therefore, 8 was subjected to olefin metathesis conditions in the absence of acrylates to check if any isomerization occurred, or if dimer 11 was the preferred or sole product

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• synthesis [7][8][9][10]. The monometallic ruthenium–benzylidene complex [RuCl2(=CHPh)(PCy3)2] (3) and its second- or even third-generation analogues developed by Grubbs and co-workers are prominent examples of catalyst precursors that were applied to olefin metathesis in tandem with ATRA [11], ATRC [11][12

• the Ru(II)–Ru(III) mixed-valence compound [(p-cymene)Ru(μ-Cl)3RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions. Keywords: Grubbs catalyst; indenylidene ligands; Kharasch reaction; microwave heating; olefin

• metathesis; Introduction During the course of our investigations on homobimetallic ruthenium–arene complexes, we found that the indenylidene compound [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) was a very efficient promoter for the ring-closing metathesis (RCM) of diethyl 2,2

New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

• Etienne Borré,
• Frederic Caijo,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2010, 6, 1159–1166, doi:10.3762/bjoc.6.132

• catalysts was investigated with various substrates in ring-closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to various chemical functions. Keywords: cross-metathesis; kinetic studies; olefin metathesis; RCM; ruthenium

• ; Introduction In the last decades, olefin metathesis has become a powerful tool in organic chemistry. Since the discovery of the well-defined ruthenium precatalyst (Cl2(PPh3)2Ru=CHPh) [1], which is tolerant to many functional groups, several synthetic routes (from petrochemical to fine chemical products) have

• olefin metathesis. Structure of precatalyst 3 and 4. Kinetic studies of RCM of 8 (0.1 M) with precatalysts 4a–g (1 mol %) in CD2Cl2 at 30 °C. Synthesis of catalysts 4a–g. Scope of 4a–e for CM transformationsa. Comparison of 4b and 4g in metathesis reactionsa. Supporting Information Supporting

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• ; metathesis; olefin isomerization; renewable raw materials; ruthenium–indenylidene catalysts; Introduction Among the large number of organic and organometallic reactions allowing the formation of carbon–carbon bonds, olefin metathesis has found its place in organic synthesis as well as polymer science as a

• ]. Later it was demonstrated that the degradation product of Grubbs 1st generation catalyst was capable of catalyzing olefin isomerization [12]. Double bond isomerization was also observed with 2nd generation catalysts on a broad variety of substrates competitively and sometimes prior to olefin metathesis

• guide to application of olefin metathesis catalysts was published by Grela and co-workers [43]. They examined the effectiveness of Ru–indenylidene complexes in standard olefin metathesis reactions and compared their activities to those of Grubbs and Hoveyda–Grubbs type catalysts. In contrast to Grubbs

Backbone tuning in indenylidene–ruthenium complexes bearing an unsaturated N-heterocyclic carbene

• César A. Urbina-Blanco,
• Xavier Bantreil,
• Hervé Clavier,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2010, 6, 1120–1126, doi:10.3762/bjoc.6.128

• parameters. Keywords: N-heterocyclic carbene; olefin metathesis; percent buried volume; ruthenium–indenylidene; Tolman electronic parameter; Introduction The use of N-heterocyclic carbenes (NHC) as spectator ligands in ruthenium-mediated olefin metathesis represents one of the most important breakthroughs

• generation catalysts has been the wide selection of NHCs available [11][12]. These highly basic ligands have now been featured in a number of catalysts that display excellent activity in olefin metathesis. NHCs have become the ligand par excellence in olefin metathesis (Figure 1) [7][8]. In order to improve

• ≈ IMesBr > IMes ≈ IMesMe. Synthesis of ruthenium–indenylidene catalysts and their performance in olefin metathesis The ruthenium–indenylidene complexes were synthesized in order to establish how strongly the electronic and steric parameters of the NHC influence catalytic activity in olefin metathesis. As

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2010, 6, 1106–1119, doi:10.3762/bjoc.6.127

• present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions. Keywords: catalysis; light activation; olefin metathesis; photoactivation; photoinitiation; photoisomerisation; RCM; ROMP; ruthenium; tungsten; Introduction The metal

• catalysed olefin metathesis reaction [1][2][3][4][5][6][7][8] has undoubtedly become one of the most widely used methodologies for the formation of carbon–carbon bonds. Its ubiquitous use in polymer chemistry [9][10][11][12][13] and natural product [14][15][16][17] and fine chemical synthesis [3][18][19][20

• ], ultimately led to the 2005 Nobel Prize award to Yves Chauvin, Richard Schrock and Robert Grubbs [21] for the development of this reaction. Since, olefin metathesis has seen much progress, such as the use of new ligands for aqueous applications [22][23][24][25][26], asymmetric synthesis [27][28][29][30] and

Halide exchanged Hoveyda-type complexes in olefin metathesis

• Julia Wappel,
• César A. Urbina-Blanco,
• Mudassar Abbas,
• Jörg H. Albering,
• Robert Saf,
• Steven P. Nolan and
• Christian Slugovc

Beilstein J. Org. Chem. 2010, 6, 1091–1098, doi:10.3762/bjoc.6.125

• Andrews KY16 9ST, United Kingdom 10.3762/bjoc.6.125 Abstract The aims of this contribution are to present a straightforward synthesis of 2nd generation Hoveyda-type olefin metathesis catalysts bearing bromo and iodo ligands, and to disclose the subtle influence of the different anionic co-ligands on the

• catalytic performance of the complexes in ring opening metathesis polymerisation, ring closing metathesis, enyne cycloisomerisation and cross metathesis reactions. Keywords: cross metathesis; olefin metathesis; RCM; ROMP; ruthenium; Introduction Since the pioneering reports on the utilisation of N

• -heterocyclic carbenes (NHC) as co-ligands in ruthenium-based carbene complexes for olefin metathesis [1][2][3] in the late nineties of the last century, olefin metathesis has become a powerful carbon-carbon double-bond-forming tool presenting unique synthetic opportunities [4]. Developments in this area can be

Progress in metathesis chemistry

• Karol Grela

Beilstein J. Org. Chem. 2010, 6, 1089–1090, doi:10.3762/bjoc.6.124

• , which started shortly after the discovery of the “olefin scrambling” reaction, it was not until much later that this transformation was “rediscovered” by the academic world. In the last decade of the 20th century, the so-called olefin metathesis reaction gained real significance in advanced organic

• more sensitive towards air and moisture, molybdenum catalysts provide excellent results in stereoselective metathesis and are sometimes more active. Therefore these catalyst families can be used in a complementary fashion. Currently, olefin metathesis (and its sister reaction, alkyne metathesis) [3] is

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP

• Olubummo Adekunle,
• Susanne Tanner and
• Wolfgang H. Binder

Beilstein J. Org. Chem. 2010, 6, No. 59, doi:10.3762/bjoc.6.59

• achieved extensively via living polymerization methods. Thus, besides acyclic diene metathesis polymerization (ADMET) [2], ring opening metathesis polymerization (ROMP) [3][4][5] is another type of olefin metathesis polymerization that can be used for the synthesis of block copolymers. Early examples of

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

Total synthesis of the indolizidine alkaloid tashiromine

• Stephen P. Marsden and
• Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

• phosphorane [17] or nickel-catalysed 1,2-metallate rearrangement of lithiated dihydropyran [18]. Our approach was informed by the prior work by our own group [19][20][21][22][23][24] and others [25][26][27][28][29][30][31][32][33][34][35][36][37][38] on the use of olefin metathesis to generate functionalised

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

• Wolfgang Maison,
• Marina Büchert and
• Nina Deppermann

Beilstein J. Org. Chem. 2007, 3, No. 48, doi:10.1186/1860-5397-3-48

• Wolfgang Maison Marina Buchert Nina Deppermann Institut für Organische Chemie, Heinrich-Buff-Ring 58, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany 10.1186/1860-5397-3-48 Abstract Background Tandem olefin metathesis sequences are known to be versatile for the generation of natural

• -azabicycloalkenes by intra- and intermolecular tandem metathesis sequences with ruthenium based catalysts. Conclusion Desymmetrization of 7-azabicycloalkenes by olefin metathesis is an efficient process for the preparation of common natural product scaffolds such as pyrrolidines, indolizidines and isoindoles

• accomplished while generating a double bond as a valuable functional group for further manipulations. In addition, the common ruthenium (Figure 1) and molybdenum based catalysts for olefin metathesis are well known for their broad functional group tolerance. The application of RCM to the synthesis of

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• sequences. Recent examples of the use of silicon-containing tethers have centred upon the Diels-Alder reaction,[4][5] radical reactions[6] and olefin metathesis reactions. There have been reports of applying the temporary tethering methodology of silicon species to the P-K reaction, but with limited success