Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• pathways. Results and Discussion The present work began with the synthesis of the aryl vinyl ether 1 from p-propylphenol in 2 steps (Scheme S1 and Figure S1 in Supporting Information File 1). Both E- and Z-forms were readily purified by silica gel column chromatography. When the anodic oxidation of the Z

• reaction of the aryl vinyl ether 1 (Scheme 7). On the basis of the oxidation potentials, oxidative SET would selectively take place from the aryl vinyl ether 1 even in the presence of 2,3-dimethyl-1,3-butadiene (2) to generate the radical cation 1·+, in which the stereochemistry derived from the starting

• anodic oxidation of the Diels–Alder adduct 3 does not give either the retro-reaction product 1 or the vinylcyclobutane 4 and therefore, it seems that the overall transformation involves irreversible steps. Thus, the radical cation Diels–Alder reaction of aryl vinyl ether 1 effectively proceeds either via

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• presence of a large excess of ethyl vinyl ether as o-QM trapping agent, they isolated several 2-ethoxychromane derivatives 16. However, yields as low as 36% were found in some cases. o-QMs derived from Mannich adducts also appear to be key intermediates in the syntheses of biologically active natural

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• -mannosylations [92]. In accordance with the linking strategy, the vinyl ether 70 was obtained in 98% yield from the corresponding 2-O-allyl ether 69 by the treatment with Wilkinson’s catalyst and BuLi (Scheme 17) [93]. Subsequent NIS-mediated tethering of 70 and acceptor 71 gave the tethered donor–acceptor pair

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen

• Naoki Doi,
• Yasushi Sasai,
• Yukinori Yamauchi,
• Tetsuo Adachi,
• Masayuki Kuzuya and
• Shin-ichi Kondo

Beilstein J. Org. Chem. 2017, 13, 1174–1183, doi:10.3762/bjoc.13.116

• microcrystalline cellulose powder through mechanocation polymerization with isobutyl vinyl ether in vacuum at 77 K [24]. The aforementioned mechanoanion was confirmed through tetracyanoethylene (TCNE) radical anion formation. The latter radical is produced by a single-electron transfer from the mechanoanion to

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• this protocol for the preparation of phosphonodihydropyrans 163 or 164 starting from phosphonopyruvate 159 or phosphonopyruvamide 160, p-nitrobenzaldehyde (161) and ethyl vinyl ether (162) in a reactor equipped with a Dean–Stark separator (Scheme 35) [73]. The yields of the resulting cycloadducts 163

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• 8-oxabicyclo[3.2.1]octane 21 framework. In this reaction, the main factor of achieving high yields or enantioselectivities, is how electron-rich or electron-poor, the dienophile is. Electron-rich olefins, like the benzyl vinyl ether and ethyl vinyl ether, reacted with success providing high yields

Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes

• Adrián Gómez-Suárez,
• Yoshihiro Oonishi,
• Anthony R. Martin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2016, 12, 172–178, doi:10.3762/bjoc.12.19

• potential applications of the vinyl ether derivatives 3 as synthetic building blocks [28], we decided to further explore the scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes. With this study, we sought to answer the following questions: what is the functional group tolerance of

• -substituted alkynes bearing ortho-substituents due to synthetic reasons. The use of the ortho-chlorophenyl derivative 1f afforded the desired vinyl ether 3ft in good yields, while changing the chlorides for methyl groups resulted in no reaction, even when using harsher reaction conditions (3gt, Scheme 4). One

• conditions, 0.5 mol % [{Au(IPr)}2(µ-OH)][BF4] as catalyst, in toluene at 80 °C for 1 h. However, GC–FID analysis of the reaction mixture revealed only traces of product. A more careful study of the crude reaction mixture by 1H NMR spectroscopy, revealed 8% conversion to the desired vinyl ether 3kt, as well

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• dark green in complexes 1–3 and from brownish to red to yellow in 4. The reaction progress of the polymerization reaction was monitored using thin-layer chromatography. After complete consumption of the monomer, the reaction was stopped with an excess of ethyl vinyl ether, precipitated in vigorously

• ; HCl relative to ruthenium) was added to activate the reaction. The reaction was followed by TLC (cyclohexane/ethyl acetate = 3:1) and after complete conversion stopped with an excess of ethyl vinyl ether. The Polymer was precipitated in vigorously stirred methanol (approx. 25 mL for 100 mg polymer

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• prepared by regioselective reduction of the carbonyl group, silylation of the resulting alcohol and further reduction of the enone moiety. An ensuing transetherification of alcohol 59 with ethyl vinyl ether gave an allyl vinyl ether, which underwent a magnesium perchlorate-promoted [1,3]-sigmatropic

• formation of the cyclooctene core was achieved via an acid-catalyzed cyclization to form tetrahydropyran 147. The following key sequence consisted of a thermal selenoxide 1,2-elimination to generate allyl vinyl ether 148 which underwent a stereoselective Claisen rearrangement [69] to furnish cyclooctenone

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• single-chain-stranded with poly(methyl vinyl ether) (PMVE) [4] or poly(dimethylsiloxane) (PDMS) [5], but also double-chain-stranded with PEG and poly(ε-caprolactone) (PCL) [6]. Recently, Akashi et al. reported the single-chain-stranded inclusion complexation of γ-CDs with poly(methyl methacrylate) (PMMA

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

• Hynek Balcar,
• Naděžda Žilková,
• Martin Kubů,
• Michal Mazur,
• Zdeněk Bastl and
• Jiří Čejka

Beilstein J. Org. Chem. 2015, 11, 2087–2096, doi:10.3762/bjoc.11.225

• to 1 μmol of Ru was put into the reactor, then toluene (13 mL) was added and the suspension was heated to 60 °C. The reaction was started by addition of (−)-β-citronellene (2 mmol) under stirring (900 rpm). At given time intervals, samples (0.1 mL) were taken and quenched with ethyl vinyl ether, and

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• with ethyl vinyl ether, dried under vacuum, and the monomer conversion was monitored via 1H NMR spectroscopy (300.1 MHz, 20 °C, D2O) by integration of the signals δ 2.58 (DAMA-CH2) and δ 2.98 ppm (cyclopentene-CH2). The aliquots taken after 60 min indicated the same conversion level as those taken

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• demonstrated a simple approach to the synthesis of 2,6-dioxabicyclo[3.3.0]octenes 286 starting with the vinyl ether 284 derived from endo-7-oxanorbornene-2-ol by employing a tandem RRM–CM protocol (Scheme 60). Norbornene systems containing two heteroatoms Kouklovsky and Vincent have disclosed the RRM of

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• magnetic stirrer under inert atmosphere at 20 °C. The polymerization was stopped by the addition of 0.3 mL of ethyl vinyl ether after 2 h. The polymers were precipitated in a 0.1% acetone solution of an antioxidant 2,2’-methylenebis(6-tert-butyl-4-methylphenol) (1), decanted, washed with several portions

• ) solution in toluene (12.3 mL) prepared as described above at 20 °C. The polymerization was stopped by the addition of 0.4 mL of ethyl vinyl ether after 1 h. The polymers were precipitated in a 0.1% ethanol solution of antioxidant 1, decanted, washed with several portions of the same solution, and dried

• mixture to 0.2 mL of ethyl vinyl ether, stirred for 30–40 min at ambient temperature, and concentrated in vacuum, after that CDCl3 was added. For DSC and GPC measurements, the copolymers were precipitated in ethanol and dried as described above. A typical 13C NMR spectrum is shown in Figure 11

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• cooling to room temperature, ethyl vinyl ether (1 mL) was added and the reaction mixture was allowed to stir for another 30 min. Finally, the reaction mixture was poured into methanol. The polymer was obtained as a white or off-white solid. General ROMP-procedure with recycling: Ru-2 (11.1 mg, 10 µmol

• methanol. The IL phase was extracted with toluene (4 × 2 mL). The extracted organic phases were also poured into methanol. Poly-M1 was obtained as a white solid. New M1 was added to the IL phase and the procedure was repeated. After the last cycle, the reaction was quenched with ethyl vinyl ether (1 mL

Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• solvent was added (5 mL) and then the pre-catalyst was weighed and charged into the Schlenk flask. Out of the glovebox, the reaction was performed at the desired temperature. Samples were taken under nitrogen flow and quenched with ethyl vinyl ether. Data were obtained by GC analysis. Examples of

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• -Diels–Alder reaction involving alkynes, ethyl glyoxalate and ethyl vinyl ether was described for the preparation of 2,3-dihydropyrans [24][25]. Additionally, a tandem CEYM–IMDAR reaction in combination with a final aromatization step was employed for the synthesis of biaryl derivatives [26]. Herein, a

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• this assumption a sample in the DSC crucible was flooded with ethyl vinyl ether for 5 days, trying to deactivate any remaining catalytic species by formation of inert Fischer carbene [32]. A control sample was flooded with diethyl ether. To our satisfaction, in the sample treated with ethyl vinyl ether

• vinyl ether. Bottom: Sample after 1 week with diethyl ether. ROMP of dicyclopentadiene by a ruthenium alkylidene initiator. Tg dependence on CPD content (%). Acknowledgements The Israel Science Foundation is gratefully acknowledged for partial financial support.

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• vinyl ether, this approach was successfully applied in the key steps of the total synthesis of a member of the thiomarinol class of marine antibiotics (Scheme 19) [66][67]. More recently, Hall and co-workers described the total synthesis of a complex 20-membered marine macrolide, palmerolide A, a potent

• ]-cycloadditons, can further be engaged in an allylation reaction that significantly increased the structural diversity of the final products (Scheme 24). As 3-boronoacrolein esters which have been used in metal-catalyzed inverse electron demand [4 + 2]-cycloadditions, 32 reacted with ethyl vinyl ether in the

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• : Claisen rearrangement. In planning the synthesis we were inspired by Ley’s synthesis of azadirachtin in which a Claisen rearrangement has been successfully employed as key transformation [37][38]. Thus the allyl vinyl ether rearrangement precursor 11 was thought to be obtained from an O-alkylation between

• allyl vinyl ether failed. Equally, copper-catalyzed C–O couplings [46] of the alcohols 19, 20 and 22 with organotrifluoroborates failed or gave only low yields. Likewise Buchwald’s procedure for the copper-catalyzed coupling of primary alcohols with vinyl iodides to yield the allyl vinyl ether or

• , depending on the reaction conditions, directly the Claisen rearrangement products was not successful [47]. Alternative strategy: Ireland–Claisen rearrangement. As the Claisen rearrangement precursor, the allyl vinyl ether, could not be obtained under various conditions, we had to change the synthetic

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• ethyl vinyl ether. The necessary diazo moiety was installed using tosylazide as a diazo-transfer reagent to yield 134. Copper catalyzed intramolecular cyclopropanation furnished bicycle 135. Reduction of the carbonyl moiety and protection of the resulting alcohol was followed by ether cleavage and

• as the corresponding bis-zinc-enolate species. DVCPR occurred at ambient temperature, final acidic workup provided cycloheptadione 247 in excellent yield (see Scheme 31). Toste and coworkers [203] reported a tandem gold-catalyzed Claisen rearrangement from popargyl vinyl ether 248 (see Scheme 32) to

The total synthesis of D-chalcose and its C-3 epimer

• Jun Sun,
• Song Fan,
• Zhan Wang,
• Guoning Zhang,
• Kai Bao and
• Weige Zhang

Beilstein J. Org. Chem. 2013, 9, 2620–2624, doi:10.3762/bjoc.9.296

• retrosynthetic analysis of I and I′ is presented in Scheme 1. Diol II and II′ arose from a Sharpless asymmetric dihydroxylation that form the C2 stereogenic center. The installation of the C3 stereocenter on vinyl ether III was proposed to utilize a Grignard reaction followed by chromatographic separation

• set using a Grignard reaction, and the hydroxy group on C2 could be introduced with the correct stereochemistry by performing a Sharpless asymmetric dihydroxylation on vinyl ether 5. In addition, diol 6 was converted to 11 by protection with TBSOTf followed by selective unveiling of the C1 hydroxy

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• signature reactions in the field (known as Teles hydration) [12]. This reaction usually utilized the combination of methanol and water, wherein methanol served as the nucleophile to attack the triple bond, forming the vinyl ether intermediate. This vinyl ether then collapsed to give a ketone as the final

• product [13][14][15][16][17]. A vinyl ether is a common and versatile building block in organic synthesis as well as polymer chemistry. Typical methods for the preparation of a vinyl ether involve elimination, olefination of esters, addition of alcohols to alkynes, as well as transition metal-mediated

• cross-coupling reactions [18]. Based on the π-carbophilicity of gold(I), the addition of alcohol to alkyne should provide direct access to the corresponding vinyl ether. However, most of the reported gold-catalyzed O-nucleophile additions to alkynes are intramolecular reactions. No general protocol for

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• general transition state 29. Negative charge in transition state 29 should be stabilized by a W-group at C(I). Substantial partial charge development would seem to be present from the observed results. In contrast, a W-group attached at C(I) of an allyl vinyl ether slightly decelerates a Claisen

• group has a small accelerative effect and alkoxy groups a larger accelerative effect when located at the C(VI) site of the allyl vinyl ether [3][23]. These observations were attributed to an electronic effect whereby the C(VI)-substituent weakened the O–C(IV) bond and hence the rearrangement energy

Acid, silver, and solvent-free gold-catalyzed hydrophenoxylation of internal alkynes

• Marcia E. Richard,
• Daniel V. Fraccica,
• Kevin J. Garcia,
• Erica J. Miller,
• Rosa M. Ciccarelli,
• Erin C. Holahan,
• Victoria L. Resh,
• Aakash Shah,
• Peter M. Findeis and
• Robert A. Stockland Jr.

Beilstein J. Org. Chem. 2013, 9, 2002–2008, doi:10.3762/bjoc.9.235

• 18). The effectiveness of different gold catalysts on the addition reaction was also studied (Table 1). While 1 was effective at promoting the addition reaction, an arylgold compound bearing a bulkier Buchwald ligand (2) afforded lower yields of the vinyl ether. Adding an additional equivalent of t

• -BuXPhos increased the yield slightly; however, 1 was still a superior catalyst. Increasing the electron-donating ability of the substituent on the aromatic group attached to the gold center in the t-BuXPhos based catalyst 3 slightly increased the yield of the vinyl ether. To investigate the effectiveness