The cross-metathesis of methyl oleate with cis-2-butene-1,4-diyl diacetate and the influence of protecting groups

• Arno Behr and
• Jessica Pérez Gomes

Beilstein J. Org. Chem. 2011, 7, 1–8, doi:10.3762/bjoc.7.1

• has become a routine and competent synthetic method for the formation of carbon–carbon double bonds [1][2][3][4][5]. Among investigations of ring opening metathesis polymerisation [6] and ring closing metathesis [7], the olefin cross-metathesis has demonstrated its great importance in providing access

Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

• Jakub Saadi,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

• ][7][8][9][10][11][12][13][14][15][16][17][18]. Successful approaches include ring-closing metathesis [4], rearrangements [5], and cycloadditions [6], transition metal-catalyzed cyclizations [7][8], nucleophilic and electrophilic substitution reactions [9] as well as ring expansion reactions [10

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

• groups in ring-closing metathesis (RCM) was first identified by Hoye and Zhao in 1999 [19]. In this work, the influence of both the steric and electronic character of allylic substituent of linalool and related analogues in RCM was assessed. The free hydroxy group on linalool greatly enhanced RCM

• ]. Ring-closing metathesis on a protein [18]. Expanded substrate scope of cross-metathesis on proteins [38]. Acknowledgements We gratefully acknowledge the EPSRC for financial support. BGD is a Royal Society Wolfson Research Merit Award recipient.

• -closing metathesis; ROM = ring-opening metathesis. b) Conventional ruthenium-based metathesis catalysts. The influence of different OR groups on ring size-selectivity [21]. Synthesis of palmerolide A precursors by Nicolaou et al. illustrates enhancement by an allylic hydroxy group in an RCM strategy [22

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

• benzylidene complexes bearing a tricyclohexylphosphine or a pyridine ligand in ring closing metathesis (RCM), cross metathesis, and ring closing enyne metathesis (RCEYM) reactions is compared. While the PCy3 complexes perform significantly better in RCM and RCEYM reactions than the pyridine complex, all

• catalyst loading As a test reaction, we initially investigated the ring closing metathesis of allyl ether 1 to dihydropyran 2 (Scheme 1). To this end, conversion to the desired product in the presence of 5 mol % of catalyst H was determined after a reaction time of one hour at a slightly elevated

• loading of 2 mol % was sufficient to achieve a 92% conversion within one hour (Figure 4). Ring closing metathesis of acrylates Having established the beneficial effect of acetic acid for the ring closing metathesis reaction of allyl ether 1 catalyzed by H, we were interested to see if a similar effect

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

• Compostela, Campus Vida, 15782 Santiago de Compostela, Spain 10.3762/bjoc.6.133 Abstract The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to

• 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

• studies. Comparison between catalysts was done at the initiation step. Moreover, conversions were compared over a reaction time of one hour. The 2-allyl-2-methallylmalonate 8 is usually used as benchmark substrate for ring-closing metathesis, inasmuch it shows significant differences between an activated

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

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

• ring-opening metathesis polymerisation was reviewed in 1997 [63]. The interest in photoactivated olefin metathesis motivated Fürstner [64] to use complex 12b for photoinduced ring closing metathesis (RCM) by using regular neon light or strong daylight as a photon source instead of the UV lamps used

• thus far. Indeed, 12b catalysed the ring-closing metathesis reaction of diallyl tosylamide in 90% yield when illuminated by neon light. Alternatively, the commercially available dimer complex 13 (Figure 5) mixed with PCy3 could be irradiated to produce similar results. Some of the photoinduced RCM

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

• 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

• substrates are transformed. The lack of reactivity data for halide-exchanged complexes prompted us to investigate the catalytic activity of bromo and iodo analogues of Hoveyda 2nd generation catalyst (1) in ring closing metathesis (RCM), enyne metathesis and cross metathesis (CM). Moreover, the scope of

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

• Satoru Arimitsu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2010, 6, No. 48, doi:10.3762/bjoc.6.48

• difluorodihydropyridinones via a ring-closing metathesis reaction, and of 4,4-difluoro-3-oxoisoquinolines through a ring-closing metathesis–enyne metathesis tandem reaction. These products, in turn, undergo a Diels–Alder reaction to yield heterotricyclic systems in moderate to good yields. Keywords: bicyclic lactams

• ; cycloisomerization; difluoropropargyl; enyne; ring-closing metathesis; Introduction It has been estimated that as many as 25% of all synthetic pharmaceutical drugs contain an amide bond [1]. Commonly, β- and γ-lactams are present in many natural products and pharmaceuticals, and the introduction of a gem

• medium-size heterocyclics are found in many natural products as part of fused cyclic structures. In their pioneering work on middle-range lactams bearing fluorine(s), Fustero et al. developed a ring-closing metathesis of α,α-difluoro-1,n-dienyl amides to furnish the corresponding α,α-difluorinated

A short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone via ring- closing metathesis

• Palakodety Radha Krishna,
• Krishnarao Lopinti and
• K. L. N. Reddy

Beilstein J. Org. Chem. 2009, 5, No. 14, doi:10.3762/bjoc.5.14

• short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone was successfully completed. Key steps included the application of Carreira’s asymmetric alkynylation reaction to form a propargylic alcohol and subsequently lactone formation using the powerful ring-closing metathesis reaction. Keywords

• : Carreira asymmetric alkynylation; Cryptocarya bourdilloni GAMB (Lauraceae); ring-closing metathesis; Sharpless asymmetric epoxidation; Introduction Natural products play an important role in the development of drugs and mankind has always taken advantage of nature as pharmacy: approximately 40% of the

• moiety [36][37], and herein we describe a short and efficient synthesis of cryptocaryalactone 1. Results and Discussion Retrosynthetic analysis Retrosynthetic analysis (Figure 2) reveals that compound 1 could be synthesized from bis-olefin 6 by a ring-closing metathesis reaction, while the bis-olefin

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

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• prepare potential bioactive fluorinated nucleosides, our group recently described the stereoselective synthesis of 3',3'-difluoro-4',5'-unsaturated OTCs 2–3 and 5 [11]. The whole synthesis highlighted the stereoselective Reformatskii-Claisen rearrangement, ring-closing metathesis (RCM), and Pd-catalyzed

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

• , ring closing metathesis (RCM) and tandem metatheses [10][11][12][13] have been particularly successful strategies for the assembly of common natural product scaffolds. [14][15][16][17][18][19][20][21][22] A general advantage of these approaches is that ring closure and/or scaffold-rearrangements can be

• and submitted to a ring closing metathesis (RCM). As a part of a general synthetic concept using azabicycloalkenes as masked analogs of functionalized pyrrolidines or piperidines [32][33][34][35][36][37][38][39] we have previously applied the concept of intramolecular ring-opening/ring-closing

• metathesis (RORCM) [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] to N-acylated 2-azabicycloalkenes 4 as precursors for azabicyclo [X.3.0]alkanes like 6 (Scheme 1).[55] Various other strained heterocycles have also been used for ring opening metathesis or other tandem metathesis sequences. [56

Synthesis of densely functionalized enantiopure indolizidines by ring- closing metathesis (RCM) of hydroxylamines from carbohydrate- derived nitrones

• Marco Bonanni,
• Marco Marradi,
• Francesca Cardona,
• Stefano Cicchi and
• Andrea Goti

Beilstein J. Org. Chem. 2007, 3, No. 44, doi:10.1186/1860-5397-3-44

• . To establish new straightforward accesses to these molecules is therefore highly desirable. Results The ring closing metathesis (RCM) of enantiopure hydroxylamines bearing suitable unsaturated groups cleanly afforded piperidine derivatives in good yields. Further cyclization and deprotection of the

• straightforward access to indolizidine derivatives and a pyrroloazepine analogue through a key ring closing metathesis (RCM) of sugar derived hydroxylamines 1 and 3 bearing suitable unsaturated substituents at the α and α' positions. Results and discussion Unsymetrically α,α'-disubstituted hydroxylamines 5 and 6

• was observed under these conditions. Ring-closing metathesis (RCM) of O-acetylhydroxylamines 8–10 using the second generation Grubbs' catalyst 11 [30] in refluxing CH2Cl2 afforded compounds 12–14 in nearly quantitative yields (Scheme 3). However, compounds 12 and 13 suffered from low stability and for

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• elimination of its mesylate (Scheme 3). Subsequent to this we became aware of a much shorter sequence for realising 4f via condensation of dimethoxydihydrofuran with benzylamine [16] or via a ring-closing metathesis reaction.[17] Pyrrolinone 4f was then subjected to the standard Mukaiyama aldol sequence

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

• applied as temporary tethers in reactions.[32] Silyl acetals have, for example, been applied to any reactions to which silyl ether have been applied, such as radical, Diels Alder reaction or ring closing metathesis, albeit with varying degrees of success. The advantage of silyl acetals over silyl ethers

Reaction of benzoxasilocines with aromatic aldehydes: Synthesis of homopterocarpans

• Míriam Álvarez-Corral,
• Cristóbal López-Sánchez,
• Leticia Jiménez-González,
• Antonio Rosales,
• Manuel Muñoz-Dorado and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2007, 3, No. 5, doi:10.1186/1860-5397-3-5

• Starting materials The starting material required for this synthesis is the novel heterocycle 3,6-dihydro-2,2-dimethyl-2H-benzo [g][1,2]oxasilocine (5), which can be prepared through ring closing metathesis (RCM), as has been previously reported for the non-benzofused system. [17][18][19] Thus, silylation

Synthesis and glycosidase inhibitory activity of new hexa- substituted C8-glycomimetics

• Olivia Andriuzzi,
• Christine Gravier-Pelletier,
• Gildas Bertho,
• Thierry Prangé and
• Yves Le Merrer

Beilstein J. Org. Chem. 2005, 1, No. 12, doi:10.1186/1860-5397-1-12

• new eight-membered carbasugars (Figure 2, A = OH) and related aminocyclitols (A = NHR) from C2-symmetrical L-ido- or D-manno- cyclooctene, easily available by ring closing metathesis of 1,9-diene derived from L-ido- or D-manno-bis-epoxide [33]. Thus, synthetic potentialities of the newly created

• concerning biological activity of C8-glycomimetics are seldom, the reported activities are often weak [24][25][26][27][28][29][30]. In summary, utilizing the readily available polyhydroxylated L-ido or D-manno-cyclooctenes, coming from ring closing metathesis of C2-symmetrical 1,9-dienes, we have

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• ) ring closing metathesis,[12][13] (iv) vinylsilane cyclization of oxocarbenium ions,[14] and (v) intramolecular allylations.[15][16] However, we were unaware of any reports that describe the direct conversion of 1,5-diols containing an internal olefin such as 2 directly to 2,6-trans-disubstituted 5,6