Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• Arabia 10.3762/bjoc.11.158 Abstract Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted

• reactivity of the complexes. Keywords: DFT calculations; olefin metathesis; ring closing metathesis; ring-opening metathesis polymerisation; ruthenium; Introduction Olefin metathesis is a catalytic process during which C–C double bonds are exchanged [1]. Since the first examples were published in the 1950s

• basic structure of ruthenium-based olefin metathesis catalysts led to a diversification of catalytic profiles (Figure 1) [5][6]. Perhaps the most important one was the introduction of bidentate benzylidene ligands instead of simple alkylidenes, thus giving rise to the class of Hoveyda-type complexes

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• Praha 6, Czech Republic 10.3762/bjoc.11.150 Abstract Cross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in

• ; catalysis; carbohydrates; cross-metathesis; ruthenium; Introduction Natural and unnatural C-substituted glycosides are important compounds with a plethora of attractive biological properties and they often have been used as artificial DNA components [1]. Among various synthetic procedures providing C

• corresponding vinyl α-C-deoxyriboside α-2 and β-C-deoxyriboside β-2 [16]. As far as further transformation of vinyl C-deoxyribosides relying on the metathesis reaction is concerned, only one paper dealing with successful cross-metathesis with 4-vinyl-5-methyl-2-oxazolone has been reported [16]. This finding is

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• -rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence

• . Interestingly the starting materials used are simple and commercially available. Keywords: alkenylation; Diels–Alder reaction; ring-rearrangement metathesis; sulfones; Introduction Sulfones [1][2][3][4][5][6][7][8] are popular building blocks [9] in organic synthesis. They are also useful substrates for the

• Ramberg–Bäcklund reaction [10] and they can be alkylated via carbanion chemistry. Moreover, they are suitable synthons in Diels–Alder (DA) reactions [11][12][13][14]. In view of various applications of sulfone derivatives, we envisioned a new synthetic strategy based on ring-rearrangement metathesis (RRM

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• -pyrano cage compound 7 involving ring-closing metathesis is reported. The hexacyclic dione 10 was prepared from simple and readily available starting materials such as 1,4-naphthoquinone and cyclopentadiene. The synthesis of an unprecedented octacyclic cage compound through intramolecular Diels–Alder (DA

• ) reaction as a key step is described. The structures of three new cage compounds 7, 12 and 18 were confirmed by single crystal X-ray diffraction studies. Keywords: cage molecules; Diels–Alder reaction; Grignard reaction; ring-closing metathesis; spirocycles; Introduction Design and synthesis of

• -closing metathesis (RCM) are considered as viable options. The retrosynthetic analysis to the target bis-spiro-cage compound 7 is shown in Figure 2. The target compound 7 could be obtained from O-allylation of the Grignard addition product 11 followed by the two-fold RCM sequence. The required cage dione

Pd(OAc)₂-catalyzed dehydrogenative C–H activation: An expedient synthesis of uracil-annulated β-carbolinones

• Biplab Mondal,
• Somjit Hazra,
• Tarun K. Panda and
• Brindaban Roy

Beilstein J. Org. Chem. 2015, 11, 1360–1366, doi:10.3762/bjoc.11.146

• mechanistic pathway that commence with electrophilic metalation at the indole C3 postion. The nucleophilicity of indole at C3 is well known [58] and a similar kind of electrophilic reaction leads to the intermediate A (Scheme 3). We believe this intermediate then undergoes a σ-bond metathesis reaction to form

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• cyclophanes. To keep the length of the review at a manageable level the literature related to orthocyclophanes was not included. Keywords: addition reactions; coupling reactions; cyclophane; metathesis; muscopyridine; name reactions; natural products; Indroduction Cyclophanes [1][2][3][4][5][6][7][8][9][10

• -binding abilities, an improved affinity can be achieved by polytopic hosts [61][62][63] through multivalency effects in macrocycles. Olefin metathesis has played a key role in the development of cyclophane chemistry. Some of the catalysts used for this purpose are listed in Figure 3. The development of

• agents in the presence of Cu(II). Fürstner and co-workers [72] have reported the total synthesis of natural products 22–24 by using a metathesis reaction [73][74][75][76][77][78][79][80][81][82] as the key step. The ring-closing metathesis (RCM) has been utilized for the synthesis of the turriane with a

Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Ongolu Ravikumar

Beilstein J. Org. Chem. 2015, 11, 1259–1264, doi:10.3762/bjoc.11.140

• Sambasivarao Kotha Ongolu Ravikumar Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400 076, India, Fax: 022-25767152 10.3762/bjoc.11.140 Abstract Atom efficient processes such as the Diels–Alder reaction (DA) and the ring-rearrangement metathesis (RRM) have been

• : Diels–Alder reaction; Grignard addition; ring-rearrangement metathesis; polycycles; Introduction Design and synthesis of complex polycycles in a minimum number of steps will enhance the overall synthetic economy of the preparation of a target molecule. The ring-rearrangement metathesis (RRM) is a

• ; HRMS (Q–ToF) m/z: [M + Na]+ calcd for C25H32NaO2, 387.2295; found, 387.2292. Commercially available ruthenium catalysts used in RRM metathesis. Crystal structure of 5 with thermal ellipsoids drawn at 50% probability level. Synthesis of hexacyclic compound 6a by using an RRM approach. Synthesis of

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• )-di-μ-acetatobis[1-(4-isopropyloxazolin-2-yl)naphthalen-2-yl-C,N]dipalladium(II) (3) (Scheme 1). Unfortunately, complex dimer 3 was relatively unstable, so only its 1H NMR and FTIR data were performed. The metathesis of dimer 3 with lithium chloride in acetone afforded the more stable (S,S)-dimer 4 in

• cool to rt and filtered through celite. The solvent was evaporated, and the crude product was recrystallized from ether/petroleum ether to obtain 3 (89%). The metathesis of dimer 3 (0.196 mmol, 1 equiv) with LiCl (18.5 mg, 0.43 mmol, 2.2 equiv) in acetone (7.0 mL) at room temperature for 24 h afforded

Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.0^2,6]undeca-3,11-dione and its congeners via ring-closing metathesis

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Rashid Ali

Beilstein J. Org. Chem. 2015, 11, 1123–1128, doi:10.3762/bjoc.11.126

• based macrocycle 6 involving Fischer indolization and ring-closing metathesis (RCM). Various spiro-polyquinane derivatives have been assembled via RCM as a key step. Keywords: aza-polyquiananes; Fischer indolization; macrocycles; ring-closing metathesis; spiropolyquinanes; Introduction Design and

• new strategy based on Fischer indolization and ring-closing metathesis as the key steps. To develop a simple synthetic methodology to aza-polycycles and spiropolycycles from readily available starting materials [47][48][49][50][51][52], bicyclic, tricyclic and pentacyclic diones (1–3) were identified

• ]. Also, based on Fischer indolization and ring-closing metathesis (RCM), we have developed a new strategy to indole-based propellane derivatives [57]. Here, the tricyclic dione 2 required was prepared starting with the Cookson’s dione 4 in two steps involving flash vacuum pyrolysis (FVP) and

Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• -closing metathesis of the N,O-diallylic spiro structure and subsequent Claisen rearrangement gave rise to the new (1R,8aS,17aS)-rel-1,2-dihydro-1-vinyl-8H,17H,9H-benz[2',3']pyrrolizino[1',7a':2,3]pyrido[1,2-a]indole-8,17-(2H,9H)-dione heterocyclic system. Keywords: allylation; cascade reactions; indigo

• structural complexity through post-allylation ring-closing metathesis, plus new biological activity investigations, which are now reported herein. Results and Discussion A range of strategies are available to potentially control reaction-path selectivity in cascade pathways [5][6] but in these indigo

• 12, with its pendant allyl substituents, affords an ideal substrate for a ring-closing metathesis reaction. In the event, treatment of 12 with Grubbs' II catalyst at reflux in CH2Cl2 produced not the expected 9-membered ring, but rather the novel fused heterocycle 31 in 70% isolated yield (Scheme 10

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• with 1,4-diiodo-2,5-bis(octyloxy)benzene (9). There are two main reactions of polycondensation that have been reported as synthetic approaches towards PAEs: the acyclic diyne metathesis polymerization (ADIMET) [55] and the Sonogashira coupling [56]. Both of them have their own advantages and drawbacks

Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

• Zhengning Li,
• Chongnian Wang and
• Zengchang Li

Beilstein J. Org. Chem. 2015, 11, 213–218, doi:10.3762/bjoc.11.23

• -lactone with a γ-exo-ester group, in 90% yield (Table 1, entry 1). Since the existing methyl methacrylate may also compete as the enolate acceptor, the high yield of 3aa indicate that lactonization of the aldolization alkoxide B proceeded much faster than metathesis of B with a silane, which gave γ

Enantioselective synthesis of polyhydroxyindolizidinone and quinolizidinone derivatives from a common precursor

• Nemai Saha and
• Shital K. Chattopadhyay

Beilstein J. Org. Chem. 2014, 10, 3104–3110, doi:10.3762/bjoc.10.327

• from a common intermediate which featured a highly selective dihydroxylation reaction and a RCM reaction as key steps. Keywords: chiral pool; dihydroxylation; indolizidines; quinolizidine; ring-closing metathesis; Introduction Polyhydroxylated indolizidine derivatives have attracted continued

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• ) [76][77]. The ability to introduce two carbon–carbon bonds on to the same α-carbon to prepare spirocyclic systems is a challenge, yet the application of electrochemistry in tandem with ring closing metathesis (RCM) readily achieved this feat. The use of the Shono-type electrooxidation in natural

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• phenanthridine core starting from a simple disubstituted aniline relied on the aza-Claisen rearrangement, ring-closing enyne metathesis and Diels–Alder reaction [41] (Scheme 18). The obtained phenanthridine derivatives were polysubstituted at the phenyl side-rings, while retaining the unsubstituted central

Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

• Malgorzata Adamkiewicz,
• David O’Hagan and
• Georg Hähner

Beilstein J. Org. Chem. 2014, 10, 2897–2902, doi:10.3762/bjoc.10.307

• of vinyl-terminated SAMs has been demonstrated, e.g., through surface modification of radicals generated by C–O bond thermolysis [17] and in a more controlled sense via olefin cross metathesis/enyne metathesis [18] of mixed vinyl and acetylenyl-terminated SAMs followed by Diels–Alder modifications of

Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

• Sambasivarao Kotha and
• Mirtunjay Kumar Dipak

Beilstein J. Org. Chem. 2014, 10, 2664–2670, doi:10.3762/bjoc.10.280

• rearrangement, a ring-closing metathesis (RCM) and an alkenyl Grignard addition. The introduction of olefinic moieties in the pentacycloundecane (PCUD) framework at appropriate positions followed by RCM led to the formation of novel heptacyclic cage systems. Keywords: Diels–Alder cycloaddition; Grignard

• addition; pentacycloundecane (PCUD); ring-closing metathesis; Introduction Caged polycyclic compounds draw the attention of synthetic organic chemists due to their unusual reactivity patterns as well as their strained nature [1][2][3][4][5][6][7][8][9]. Several pentacycloundecane (PCUD) related molecules

• . The addition of alkyl groups can take place from the less hindered exo side of this caged system. If the R and R’ groups contain unsaturated systems one can think of constructing additional rings on the pentacyclic framework by utilizing ring-closing metathesis (RCM). By varying the length of

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• could be transformed into cycloalkenes with a stereocenter remote to the olefin [44], chiral diene 27 was submitted to ring closing metathesis to generate 28 in 90% yield and 92% ee [43]. Cyclohexene 28 readily undergoes acetonide cleavage and periodic acid oxidation to provide carboxylic acid (S)-22

• converted to 2-allyl-2-methylcyclohexanone (2) in 85% yield and 88% ee [58] with a catalytic amount of [Pd2(dba)3] and (S)-t-BuPHOX (5, Scheme 1). The allyl ketone was enriched to 98% ee via recrystallization of semicarbazone 33 [59]. Using the Grubbs 2nd generation metathesis catalyst, allyl ketone (−)-2

A modular phosphate tether-mediated divergent strategy to complex polyols

• Paul R. Hanson,
• Susanthi Jayasinghe,
• Soma Maitra,
• Cornelius N. Ndi and
• Rambabu Chegondi

Beilstein J. Org. Chem. 2014, 10, 2332–2337, doi:10.3762/bjoc.10.242

• generates five polyol fragments, bearing differential Z- and E-olefins, from a pair of olefinic-alcohol components A and B and a pseudo-C2-symmetric phosphoryl chloride (S,S)-1. Moreover, the method relies on simple "order of addition" of components for the phosphoryl coupling, ring-closing metathesis (RCM

• ) and cross metathesis (CM) steps of the process as outlined in Scheme 1. This protocol further highlights the utility of phosphate tether mediated desymmetrization of C2-symmetric 1,3-anti-diene-diol subunit to generate polyol scaffolds which would otherwise be difficult to produce via (Z)-and (E

• and subsequent LiAlH4 reduction to generate tetraol 17 in 24% yield over 4 reaction steps in a two-pot operation (70% avg/rxn) (Scheme 3). Further, starting with the same triene 6, which was previously used in Scheme 2, but utilizing a different cross-metathesis partner (homoallylic alcohol 4), a

De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles

• Richard T. Desmond,
• Anniefer N. Magpusao,
• Chris Lorenc,
• Jeremy B. Alverson,
• Nigel Priestley and
• Mark W. Peczuh

Beilstein J. Org. Chem. 2014, 10, 2215–2221, doi:10.3762/bjoc.10.229

• . Results and Discussion The syntheses of 5 and 6 (Scheme 1) generally followed a ring closing metathesis (RCM) strategy that had been established previously [9]. C4,C6-O-Benzylidene-protected allyl glucoside 7, as a mixture of α- and β-anomers, was the starting material for the synthesis. In the first step

• 5 and 6 from an angle perpendicular to the D-glucose plane; e) and f) Newman projections, sighting down the glycosidic bond, of 5 and 6. Synthesis of macrolides 5 and 6 by a ring closing metathesis strategy. Selected bond angles for 5 and 6 from X-ray crystallographic data. MIC (μg/mL) values for

Organophosphorus chemistry

• Paul R. Hanson

Beilstein J. Org. Chem. 2014, 10, 2087–2088, doi:10.3762/bjoc.10.217

• phosphinoyl-indoles and phosphinoyl-isocoumarins and new chemistries of H-phosphonates. The Thematic Series also details work on new metathesis-based reactions of vinyl phosphonates and phosphate tethers, novel phosphorus-based ligands in asymmetric catalysis, novel rasta resin–triphenylphosphine oxides and

Relay cross metathesis reactions of vinylphosphonates

• Raj K. Malla,
• Jeremy N. Ridenour and
• Christopher D. Spilling

Beilstein J. Org. Chem. 2014, 10, 1933–1941, doi:10.3762/bjoc.10.201

• Raj K. Malla Jeremy N. Ridenour Christopher D. Spilling Department of Chemistry and Biochemistry, University of Missouri St. Louis, One University Boulevard, St. Louis, MO 63121, USA 10.3762/bjoc.10.201 Abstract Dimethyl (β-substituted) vinylphosphonates do not readily undergo cross metathesis

• reactions with Grubbs catalyst and terminal alkenes. However, the corresponding mono- or diallyl vinylphosphonate esters undergo facile cross metathesis reactions. The improved reactivity is attributed to a relay step in the cross metathesis reaction mechanism. Keywords: centrolobine; metathesis; organo

• . Unlike the parent compound, vinylphosphonates substituted with an aryl or alkyl group on the alkene appear to have somewhat limited reactivity. This lack of reactivity is exemplified by the Grubbs cross metathesis reaction [10]. Grubbs and co-workers classified terminal vinylphosphonates as type III

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

Postsynthetic functionalization of glycodendrons at the focal point

• Thisbe K. Lindhorst and
• Katharina Elsner

Beilstein J. Org. Chem. 2014, 10, 1482–1487, doi:10.3762/bjoc.10.152

• etherification, thiol-ene reaction and in particular olefin cross metathesis. Keywords: amphiphilic glycomimetics; cross metathesis; glycodendrons; multivalent glycoconjugates; multivalent glycosystems; Introduction In addition to nucleic acids and proteins, molecular life is based on a third important class

• , respectively, in fair yields. Deprotection conditions employing TFA in water left the thioethers intact. These results were encouraging for further postsynthetic modification of glycodendrons. In a second part of our study we have investigated olefin cross metathesis [11] of polyether di- and tetravalent

• -configured alkenes were the only cross-coupling products obtained. This might be due to the specific structure of the used substrates, as sterically hindered olefins are known to enhance trans-selectivity in metathesis [12]. The same reactions were successful with the tetravalent glycodendron 9 yielding the

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• derivatization as well as for solid-phase peptide synthesis. With respect to according motifs occurring in natural products, we have converted these building blocks into 3-O-acylated structures. Utilizing an esterification and cross-metathesis protocol, (2S,3S)-3-hydroxyleucine derivatives were synthesized, thus

• opening up an excellent approach for the synthesis of bioactive natural products and derivatives thereof for structure activity relationship (SAR) studies. Keywords: chiral pool; cross metathesis; esterification; β-hydroxy-α-amino acids; natural products; Introduction Besides the proteinogenic β-hydroxy

• develop a method for the modification of the acyl side chain of a previously incorporated O-acylated β-hydroxy-α-amino acid building block at a very late stage and under mild conditions, e.g., by olefin cross metathesis. Therefore, amino alcohol 5 was Fmoc-protected (product 34, 84% yield), followed by