- ω-Alkenylallylboronates: Design, Synthesis, and Application to the Asymmetric Allylation/RCM Tandem Sequence
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The synthesis of allylboronates bearing an alkenyl moiety appended at a remote position is described for the first time. For that aim, the palladium-catalyzed borylation of the corresponding allylic alcohols was used as the key step. The required allylic alcohols were in turn obtained in 3–4 step sequences. The presence of an extra alkenyl moiety at a strategic position allows the triggering of a tandem asymmetric allylation/RCM reaction sequence that efficiently affords different sized cycles featuring two consecutive stereocenters and an exocyclic alcohol function. Products are obtained in moderate to excellent yields and high enantioselectivities, in most of the cases.
- Barrio, Pablo,Garnes-Portolés, Francisco,Grayson, Matthew N.,Miguélez, Rubén
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- Unsaturated acyclic analogues of 2'-deoxyadenosine and thymidine containing fluorine: Synthesis and biological activity
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The syntheses and biological activities of fluorobutynol 11 and (E)- and (Z)-fluorobutenols 8a,d and 9a,d are described. Alkylation of adenine with bromofluorobutyne 13a afforded intermediate 14 which was converted to fluorobutynol 11. Aldehyde 16a and (c
- Xu,Qiu,Chokekijchai,Mitsuya,Zemlicka
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- A novel oxidative cleavage reaction of propargyl alcohol derivatives using K2FeO4-Al2O3
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Recent work has shown that a new K2FeO4 based oxidation protocol can promote a highly unusual carbon-carbon bond cleaving reaction of functionalised propargyl alcohols.
- Caddick, Stephen,Murtagh, Lorraine,Weaving, Robert
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- Chiral acyl radical equivalents: 5-exo cyclization of conformationally constrained 1,3-dioxolanyl radicals
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Chiral 1,3-dioxolan-2-yl radicals derived from acetals 8 and 9 underwent intramolecular hydrogen abstraction followed by 5-exo-trig cyclization on treatment with tributyltin hydride and AIBN with modest and opposite stereoselectivities. The more highly su
- Stien,Crich,Bertrand
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Read Online
- Structure and solvent-induced tuning of laser property and photostability of a boradiazaindacene (BODIPY) dye
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Boradiazaindacene (BODIPY) class of laser dyes are highly efficient but degrade rapidly in alcohol solution during lasing action, progressively reducing output power. Photodegradation of these dyes is mainly due to reaction with the in situ generated singlet oxygen (1O2). With the aim to increase the lasing lifetimes of these dyes, we have designed and synthesized a new congener of the widely used BODIPY dye (PM567) by substitution at its B-centre. The new dye was highly fluorescent, and showed comparable lasing efficiency, but better photostability relative to PM567 in both polar (ethanol) and non-polar (1,4-dioxane) solvents, when excited by 2nd harmonic (532 nm) of a pulsed Nd-YAG laser. More interestingly, the lasing efficiency and photostability of both the dyes were much better in 1,4-dioxane than in ethanol. The relative photostabilities of the dyes were rationalized by absorption spectroscopic analyses of their triplet state properties in the respective solvents in the presence of a 1O2 generator or quencher as an additive, pulse radiolysis studies and quantum chemical calculations.
- Gupta, Monika,Mula, Soumyaditya,Ghanty, Tapan K.,Naik,Ray, Alok K.,Sharma, Anubha,Chattopadhyay, Subrata
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- Synthesis and Photoswitching Properties of Bioinspired Dissymmetric I-Pyrone, an Analogue of Cyclocurcumin
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Cyclocurcumin (CC), a turmeric curcuminoid with potential therapeutic properties, is also a natural photoswitch that may undergo E/Z photoisomerization under UV light. To be further exploited in relevant biological applications, photoactivation under near-infrared (NIR) irradiation is required. Such requirement can be met through opportune chemical modifications, by favoring two-photon absorption (TPA) probability. Herein, a general and efficient synthesis of a biomimetic 2,6-disubstituted-δ-pyrone analogue of CC is described, motivated by the fact that molecular modeling previews an order of magnitude increase of its NIR TPA compared to CC. Three retrosynthetic pathways have been identified (i) via an aryl-oxazole intermediate or via aryl-diynone through (ii) a bottom-up or (iii) a top-down approach. While avoiding the passage through unstable synthons or low-yield intermediate reactions, only the latest approach could conveniently afford the 2,6-disubstituted-I-pyrone analogue of CC, in ten steps and with an overall yield of 18%. The photophysical properties of our biomimetic analogue have also been characterized showing an improved photoisomerization yield over the parent natural compound. The potentially improved nonlinear optical properties, as well as enhanced stability, may be correlated to the enforcement of the planarity of the pyrone moiety leading to a quadrupolar D-π-A-π-D system.
- Pecourneau, Jérémy,Losantos, Raúl,Monari, Antonio,Parant, Stéphane,Pasc, Andreea,Mourer, Maxime
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p. 8112 - 8126
(2021/06/30)
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- Ni-catalyzed direct carboxylation of propargylic alcohols with carbon dioxide
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The carboxylation of propargylic alcohols containing a silyl group at the terminal position was conducted in a CO2 atmosphere at atmospheric pressure in the presence of a nickel catalyst and diethylzinc. Here, CO2 was used as not only the C1 source but also the promoter of the COH cleavage processes for the oxidative addition of propargylic alcohols.
- Yamahira, Tatsuya,Onodera, Gen,Fukuda, Tsutomu,Kimura, Masanari
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supporting information
p. 853 - 855
(2021/05/19)
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- Method for synthesizing sex pheromone of hyphantria cunea
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The invention relates to the technical field of hyphantria cunea prevention and treatment, in particular to a synthetic method for synthesizing sex pheromone of hyphantria cunea. According to a traditional method for synthesizing (3Z,6Z,9S,10R)-9,10-epoxy-3,6-heneicosadiene by using propargyl alcohol as a starting material in the traditional technology, various side reactions are liable to occur during a sulfonic acid esterification reaction on a key intermediate (2S,3R)-2,3-epoxy-1-tetradecanol by using trifluoromethanesulfonic anhydride. In order to solve the problems, the (3Z,6Z,9S,10R)-9,10-epoxy-3,6-heneicosadiene is successfully synthesized by taking propargyl alcohol as an initial raw material and taking a Sharpless asymmetric dihydroxylation reaction as a key step without the step of the sulfonic acid esterification reaction on a key intermediate (2S,3R)-2,3-epoxy-1-tetradecanol by trifluoromethanesulfonic anhydride in the preparation process. Therefore, the whole reaction is mild and controllable and few in side reactions, and enantioselectivity is high.
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Paragraph 0034-0037
(2021/04/17)
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- Stereoselective synthesis of C3–C17 and C18–C34 subunits of bullatanocin utilizing α-chloro sulfide intermediates
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A convergent synthesis of bullatanocin is envisaged by the union of C18–C34, C3–C17 and the butenolide subunits. The synthesis of the C3–C17 and C18–C34 subunits is disclosed that takes advantage of the chirality of tartaric acid for 1,2-asymmetric induct
- Chowhan, L. Raju,Raghavan, Sadagopan
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supporting information
(2019/09/17)
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- Stereochemistry of Linoleic Acid Esters of Hydroxy Linoleic Acids
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The syntheses of linoleic acid esters of hydroxy linoleic acids (LAHLAs) present in oat oil and human serum have been achieved, providing access to material for testing and the determination of the stereochemistry of the natural compounds. While 9- and 13-LAHLAs were found to be a mixture of enantiomers 15-LAHLA is generated in a single optical form in oat oil. The stereochemistry of 15-LAHLA in oat oil was found to be opposite to that reported for digalactosyldiacylglycerol that possesses an embedded 15-LAHLA.
- Wang, Huijing,Kolar, Matthew J.,Chang, Tina,Rizo, José,Konduri, Srihari,McNerlin, Clare,Saghatelian, Alan,Siegel, Dionicio
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supporting information
p. 8080 - 8084
(2019/10/14)
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- Cu(I) catalyzed coumarin-1,2,3-triazole hybrids: Click chemistry
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A series of novel coumarin-1,2,3-triazole derivatives were synthesized in good yield via click chemistry using Cu(I) catalyzed intermolecular Huisgen [3+2] cycloaddition reaction. All the synthesized compounds were characterized spectroscopically. This piece of work could be helpful to develop biologically relevant coumarin analogs.
- Mamgain, Ritu
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p. 2543 - 2547
(2019/10/02)
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- An orthogonally protected CycloTriVeratrylene (CTV) as a highly pre-organized molecular scaffold for subsequent ligation of different cyclic peptides towards protein mimics
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The synthesis of a semi-orthogonally protected CycloTriVeratrilene (CTV) scaffold derivative as well as the sequential introduction of three different peptide loops onto this molecular scaffold via Cu(I)-catalyzed azide alkyne cycloaddition towards a medium-sized protein mimic is described. This approach for the construction of medium-sized protein mimics is illustrated by the synthesis of a paratope mimic of the monoclonal antibody Infliximab (Remicade) and provides access to a range of highly pre-organized molecular constructs bearing three different peptide segments. This approach may find wide applications for development of protein-protein interaction disruptors as well as synthetic vaccines.
- Longin, Ond?ej,van de Langemheen, Helmus,Liskamp, Rob M.J.
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p. 5008 - 5015
(2017/09/19)
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- Gold-catalyzed N, O-functionalizations of 6-allenyl-1-ynes with n-hydroxyanilines to construct benzo[b]-azepin-4-one cores
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Gold-catalyzed reactions of 6-allen-1-ynes with N-hydroxyanilines afford thermally stable benzoazepin-4-ones in anti-selectivity; these anti-configured products are easily isomerized to their syn-isomers on a silica column. The mechanism of reactions likely involve initial nitrone/allene cycloadditions, followed by skeletal rearrangement of resulting intermediates.
- Raj, Antony Sekar Kulandai,Kale, Balaji S.,Mokar, Bhanudas Dattatray,Liu, Rai-Shung
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supporting information
p. 5340 - 5343
(2017/11/07)
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- Synthesis of Functionalized [3], [4], [5] and [6]Dendralenes through Palladium-Catalyzed Cross-Couplings of Substituted Allenoates
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A mild method for the synthesis of highly functionalized [3]–[6]dendralenes is reported, representing a general strategy to diversely substituted higher homologues of the dendralenes. The methodology utilizes allenoates bearing various substitution patter
- Lippincott, Daniel J.,Linstadt, Roscoe T. H.,Maser, Michael R.,Lipshutz, Bruce H.
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supporting information
p. 847 - 850
(2017/01/14)
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- Zwitterionic imidazolium salt: An efficient organocatalyst for tetrahydropyranylation of alcohols
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An aprotic imidazole based zwitterionic-salt, 4-(3-methylimidazolium)-butane sulfonate has been found to be an efficient organocatalyst for tetrahydropyranylation by the reaction of 3,4-dihydro-2H-pyran (DHP) and different aliphatic alcohols as well as various phenolic compounds. The notable advantages of the present method are general applicability to various alcohols, clean reaction, production of no hazardous waste, open air reaction conditions and high yields. The catalyst can be reused without the loss of significant catalytic activity.
- Mahato, Sachinta,Chatterjee, Rana,Chakraborty Ghosal, Nirnita,Majee, Adinath
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supporting information
p. 1905 - 1915
(2017/10/07)
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- The (+)-cis- and (+)-trans-Olibanic Acids: Key Odorants of Frankincense
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Frankincense (olibanum) is one of the oldest aromatic materials used by humans, but the key molecular constituents contributing to its characteristic odor remained unknown. Reported herein is the discovery that (1S,2S)-(+)-trans- and (1S,2R)-(+)-cis-2-octylcyclopropyl-1-carboxylic acids are highly potent and substantive odorants occurring in ppm amounts in all of the frankincense samples analyzed, even those showing radically different volatile compositions. These cyclopropyl-derived acids provide the very characteristic old churchlike endnote of the frankincense odor.
- Cerutti-Delasalle, Céline,Mehiri, Mohamed,Cagliero, Cecilia,Rubiolo, Patrizia,Bicchi, Carlo,Meierhenrich, Uwe J.,Baldovini, Nicolas
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supporting information
p. 13719 - 13723
(2016/10/26)
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- Asymmetric hydrogenation of furans and benzofurans with iridium-pyridine-phosphinite catalysts
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Enantioselective hydrogenation of furans and benzofurans remains a challenging task. We report the hydrogenation of 2- and 3-substituted furans by using iridium catalysts that bear bicyclic pyridine-phosphinite ligands. Excellent enantioselectivities and high conversions were obtained for monosubstituted furans with a 3-alkyl or 3-aryl group. Furans substituted at the 2-position and 2,4-disubstituted furans proved to be more difficult substrates. The best results (80-97% conversion, 65-82% enantiomeric excess) were obtained with monosubstituted 2-alkylfurans and 2-[4-(trifluoromethyl)phenyl]furan. Benzofurans with an alkyl substituent at the 2- or 3-position also gave high conversions and enantioselectivity, whereas 2-aryl derivatives showed essentially no reactivity. The asymmetric hydrogenation of a 3-methylbenzofuran derivative was used as a key step in the formal total synthesis of the cytotoxic naphthoquinone natural product (-)-thespesone.
- Pauli, Larissa,Tannert, Re,Scheil, Robin,Pfaltz, Andreas
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supporting information
p. 1482 - 1487
(2015/01/30)
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- Gold-catalyzed allene cycloisomerization for pyrrole synthesis: Towards highly fluorinated BODIPY dyes
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A novel synthetic strategy toward highly fluorinated BODIPY dyes with exceptional photostabilities relying on sustainable gold catalysis has been developed. A key to the tailored pyrrole precursors is the gold catalysis performed in ionic liquids as the reaction medium, allowing a facile recycling of the catalysts. The dyes prepared are well-matching with the spectral windows of popular rhodamine dyes and possess high brightness while showing a distinctly higher photostability than the rhodamines especially in aprotic solvents.
- Lempke, Linda,Fischer, Tobias,Bell, Jérémy,Kraus, Werner,Rurack, Knut,Krause, Norbert
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supporting information
p. 3787 - 3791
(2015/03/30)
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- Synthesis of furans through silver-catalyzed propargyl-claisen rearrangement followed by cyclocondensation
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The generation of highly substituted furans from propargyl vinyl ethers bearing a free hydroxy group was investigated. In the presence of catalytic amounts of AgBF4, a formal [3,3] sigmatropic rearrangement takes place in the first stage of the
- Palisse, Adeline,Kirsch, Stefan F.
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supporting information
p. 7095 - 7098
(2015/01/09)
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- Highly regioselective hydrosilylation of unsymmetric alkynes using a phenylthio directing group
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Cobalt-assisted hydrosilylation of acetylenes is particularly interesting in organic synthesis since alkynyl group functionalization can give way to more useful substructures. This study aims to answer the general question of how to control hydrosilylatio
- Huang, Kuan-Hsun,Isobe, Minoru
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supporting information
p. 4733 - 4740
(2014/08/05)
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- Regio- and diastereoselective copper(I)-catalyzed allylic substitution of δ-hydroxy allylic chlorides by a silicon nucleophile
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A perfectly γ-selective copper(I)-catalyzed allylic substitution of protected δ-hydroxy allylic chlorides with a silicon nucleophile generated by Si-B bond activation provides diastereoselective access to β-hydroxy α-chiral allylic silanes with an anti re
- Hazra, Chinmoy K.,Irran, Elisabeth,Oestreich, Martin
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supporting information
p. 4903 - 4908
(2013/08/23)
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- Construction of enantioenriched cyclic compounds by asymmetric allylic alkylation and ring-closing metathesis
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A new approach to highly enantioenriched cyclic compounds (up to 98a€‰% ee) has been developed by using ω-ethylenic allylic substrates in a one-pot asymmetric allylic alkylation and ring-closing metathesis sequence. The starting compounds are synthetic equivalents of cyclic allylic substrates. The method is exemplified with both Cu and Ir catalysts, and chiral phosphoramidite ligands. A new approach to highly enantioenriched cyclic compounds (up to 98a€‰% ee) has been developed by using ω-ethylenic allylic substrates in a one-pot asymmetric allylic alkylation and ring-closing metathesis sequence. The starting compounds are synthetic equivalents of cyclic allylic substrates. The method is exemplified with both Cu and Ir catalysts, and chiral phosphoramidite ligands. Copyright
- Giacomina, Francesca,Alexakis, Alexandre
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supporting information
p. 6710 - 6721
(2013/11/06)
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- Enantiomer and conformer recognition of (+) and (-)-disparlure and their analogs by the pheromone binding proteins of the gypsy moth, Lymantria dispar
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Adult female gypsy moths produce a sex pheromone (+)-(7R,8S)-2-methyl-7,8- epoxyoctadecane, (+)-disparlure, to attract male gypsy moths. To better understand the recognition of (+)-disparlure by the male's olfactory system, we synthesized racemic and enantiopure oxa and thia analogs of (+)-disparlure (ee > 98%). Ab initio calculations of the conformeric landscapes around the dihedral angles C5-6-7-8 and C7-8-9-10 of (+)-disparlure and corresponding dihedral angles of analogs revealed that introduction of the heteroatom changes the conformeric landscape around these important epitopes. The energy difference between HOMO and LUMO decreased after oxygen or sulfur was introduced into the backbone. Consistent with this, an enhancement of binding affinity between sulfur analogs and the pheromone-binding proteins (PBPs) was observed in vitro. Docking of the pheromone and analogs onto models of the two known PBPs of the gypsy moth revealed that the internal binding pocket of PBP1 showed higher selectivity than that of PBP2, consistent with in vitro binding assays. Further energy analysis revealed that enantiomers adopted different conformations with different energies when docked in the internal binding pocket of PBPs, resulting in enantiomer discrimination of PBPs towards disparlure and its analogs.
- Yu, Yang,Plettner, Erika
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supporting information
p. 1811 - 1822
(2013/04/24)
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- Synthesis of functionalized oxazoles via silver-catalyzed cyclization of propargylamides and allenylamides
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Silver(I)-catalyzed [3,3] rearrangement of N-sulfonyl propargylamides affords functionalized oxazoles with highly regioselective migration of the sulfonyl group by the introduction of acyloxy groups. The allenylamides, generated from the corresponding propargylamides, can also undergo the silver-catalyzed cyclization to give various 5-vinyloxazoles.
- Hu, Yancheng,Yi, Ruxia,Wu, Fan,Wan, Boshun
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p. 7714 - 7726
(2013/09/02)
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- METHODS FOR THE SYNTHESIS OF PLASMALOGENS AND PLASMALOGEN DERIVATIVES, AND THERAPEUTIC USES THEREOF
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A method for preparing plasmalogens and derivatives thereof represented by Formula B, wherein R1 and R2 are similar or different, derived from fatty acids; R3 is selected from hydrogen and small alkyl groups. The synthetic route involves production of novel cyclic plasmalogen precursors of Formula A and their conversion to plasmalogens and plasmalogen derivatives of Formula B. Also disclosed is the therapeutic use of plasmalogens and derivatives thereof as produced by the synthetic route of the present invention.
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Page/Page column 19-20
(2013/06/05)
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- Solvent-free NaHSO4-SiO2-catalyzed efficient tetrahydropyranylation of alcohols and phenols
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A simple and efficient tetrahydropyranylation of alcohols and phenols has been developed using NaHSO4-SiO2 (0.5 mol%) as a catalyst under solvent-free conditions to yield corresponding tetrahydropyranyl ethers in excellent yields.
- Kinfe, Henok H.,Mebrahtu, Fanuel M.,Moshapo, Paseka T.
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p. 1237 - 1242
(2013/04/10)
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- Concise catalytic asymmetric total synthesis of biologically active tropane alkaloids
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A general strategy for the total asymmetric synthesis of valuable tropane alkaloids by catalytic stereoselective transformations is disclosed. The power of this approach is exemplified by the concise catalytic enantioselective total syntheses of (+)-methylecgonine, (-)-cocaine and (+)-cocaine as well as the first catalytic asymmetric total syntheses of a cocaine C-1 derivative and (+)-ferruginine starting from 5-oxo-protected-α,β-unsaturated enals using only two and three column chromatographic purification steps, respectively. Copyright
- Cordova, Armando,Lin, Shuangzheng,Tseggai, Abrehet
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supporting information; experimental part
p. 1363 - 1372
(2012/06/18)
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- Novel triacsin C analogs as potential antivirals against rotavirus infections
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Recently our group has demonstrated that cellular triglyceride (TG) levels play an important role in rotavirus replication. In this study, we further examined the roles of the key enzymes for TG synthesis (lipogenesis) in the replication of rotaviruses by
- Kim, Yunjeong,George, David,Prior, Allan M.,Prasain, Keshar,Hao, Shuanghong,Le, Duy D.,Hua, Duy H.,Chang, Kyeong-Ok
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experimental part
p. 311 - 318
(2012/06/29)
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- Synthesis of sulfonic acid functionalized carbon catalyst from glycerol pitch and its application for tetrahydropyranyl protection/deprotection of alcohols and phenols
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A novel carbon catalyst with -SO3H, -OH and -COOH functional groups was prepared from glycerol pitch by in situ partial carbonization and sulfonation with sulfuric acid. The activity of the catalyst was investigated through tetrahydropyranylation and dehydropyranylation of a wide variety of alcohols and phenols at room temperature by changing the solvent medium from dichloromethane to methanol. Excellent yields, short reaction times, easy and quick isolation of the products and reusability of the catalyst are the main attractions of this method. The novel carbon catalyst holds great potential in the green chemical processes.
- Prabhavathi Devi,Gangadhar,Siva Kumar,Shiva Shanker,Prasad,Sai Prasad
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experimental part
p. 96 - 100
(2011/10/05)
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- Generation of α,β-unsaturated platinum carbenes from homopropargylic alcohols: Rearrangements to polysubstituted furans
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A number of diversely substituted furans are synthesized via a cycloisomerization process that goes through a unique metal carbene species. Both ligand structure and the nature of the leaving group are evaluated. The characteristics of the carbene intermediate can be modulated, resulting in highly selective hydrogen or silicon group migrations.
- Allegretti, Paul A.,Ferreira, Eric M.
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supporting information; experimental part
p. 5924 - 5927
(2011/12/16)
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- Synthesis of 5-acetyloxazoles and 1,2-diketones from β-alkoxy-β- ketoenamides and their subsequent transformations
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Lithiated alkoxyallenes, nitriles, and carboxylic acids have been employed as precursors in a three-component reaction leading to highly substituted β-alkoxy-β-ketoenamides. Upon treatment with trifluoroacetic acid, these enamides could be easily cyclized
- Lechel, Tilman,Gerhard, Markus,Trawny, Daniel,Brusilowskij, Boris,Schefzig, Luise,Zimmer, Reinhold,Rabe, Juergen P.,Lentz, Dieter,Schalley, Christoph A.,Reissig, Hans-Ulrich
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supporting information; experimental part
p. 7480 - 7491
(2011/08/08)
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- Efficient tetrahydropyranyl and tetrahydrofuranyl protection/deprotection of alcohols and phenols with Al(OTf)3 as catalyst
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A simple and efficient method for the conversion of alcohols and phenols into their corresponding THP and THF ethers at room temperature has been developed using 1 mol % aluminium triflate as catalyst. The deprotection reaction in the presence of methanol using Al(OTf)3 was equally successful and could be performed at ambient temperature in high yields.
- Williams, D. Bradley G.,Simelane, Sandile B.,Lawton, Michelle,Kinfe, Henok H.
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experimental part
p. 4573 - 4576
(2010/07/05)
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- Synthesis of demethylated nidulol via an intramolecular Michael reaction
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An expeditious synthesis of 5,7-dihydroxy-6-methylphthalide from open-chain precursors is described. The key intermediates, synthons 3 and 4, were readily obtained from accessible materials and were further transformed to a common precursor, a five-membered lactone derivative, via an intramolecular Michael addition. Lactone 2 was aromatised to the phthalide system under basic conditions. The process thus constitutes a formal synthesis of the phthalide framework.
- Jimenez, Rogelio,Maldonado, Luis A.,Salgado-Zamora, Hector
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scheme or table
p. 1274 - 1281
(2010/12/19)
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- Synthesis of 1-stannylated and 1-iodinated 1-chloroalkenes as versatile synthetic intermediates
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An efficient and convenient synthesis of 1-stannylated and iodinated 1-chloroalkenes is described based on MoBI3-catalyzed hydrostannations of 1-chloroalkynes, followed by a tin-iodine exchange. The 1-chloro-1-iodoalkenes are suitable substrates for further modification, for example, via cross-coupling reactions.
- Pratap, Ramendra,Kazmaier, Uli
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experimental part
p. 3073 - 3077
(2011/02/25)
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- Gosteli-claisen rearrangement: Substrate synthesis, simple diastereoselectivity, and kinetic studies
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The results of kinetic studies on the uncatalyzed [3,3]-sigmatropic rearrangement of 2-alkoxycarbonyl- substituted allyl vinyl ethers are reported. Apparently first reported by Gosteli in 1972, this variation of a Claisen rearrangement enjoyed a shadowy existence for three decades until its potential for the development of a catalytic asymmetric Claisen rearrangement was discovered. Inspired by this development, we have studied substituent and solvent rate effects, and we provide evidence that a chairlike transition state is highly favorable for the uncatalyzed Gosteli-Claisen rearrangement.
- Rehbein, Julia,Leick, Sabine,Hiersemann, Martin
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supporting information; experimental part
p. 1531 - 1540
(2009/09/05)
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- A new pd-catalyzed cascade reaction for the synthesis of strained aromatic polycycles
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Two new palladium catalyzed cascade reactions involving a 4-exo-dig cyclocarbopalladation are described. These processes are shown to convert bromoenediynes and bromodienynes into strained aromatic compounds in a single step.
- Blond, Gaelle,Bour, Christophe,Salem, Bahaa,Suffert, Jean
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supporting information; body text
p. 1075 - 1078
(2009/04/06)
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- Design, synthesis and biological evaluations of a novel series of enediynes constituted with DNA cleavage, alkylating and DNA binding agents via varies spacers
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Among the three series of complicated combinatory enediynes, 3a-d were more active than 2a-c and 4a-b, in which 3a-b showed equally inhibitory activity against the growth of Hepa59T/VGH, KB and Hela with mean IC50 values lower than 10 μg/mL. Co
- Linb, Chi-Fong,Hwanga, Martin,Kuo, Yao-Haur,Wu, Ming-Jung
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p. 525 - 532
(2008/02/11)
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- Generally applicable organocatalytic tetrahydropyranylation of hydroxy functionalities with very low catalyst loading
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This paper presents the first acid-free, organocatalytic tetrahydropyran and 2-methoxypropene protection of alcohols, phenols, and other ROH derivatives utilizing privileged N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea and a polystyrene-bound analogue. The reactions are broadly applicably (also on preparative scale), in particular, to acid-sensitive substrates such as aldol products, hydroxy esters, acetals, silyl-protected alcohols, and cyanohydrins. The catalytic efficiency is truly remarkably with turnover numbers of 100,000 and turnover frequencies of up to 5700 h-1 at catalyst loadings down to 0.001 mol%. The computationally supported mechanistic interpretation emphasizes the hydrogen bond assisted heterolysis of the alcohol and concomitant preferential stabilization of the oxyanion hole in the transition state. Georg Thieme Verlag Stuttgart.
- Kotke, Mike,Schreiner, Peter R.
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p. 779 - 790
(2008/01/03)
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- A mild and efficient chemoselective tetrahydropyranylation of primary alcohols using La(NO3)3·6H2O as a catalyst under solvent-free conditions
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Primary alcohols undergo selective and efficient tetrahydropyranylation in the presence of a catalytic amount of La(NO3)3?6H2O under solvent-free conditions.
- Reddy, T. Srikanth,Ravinder,Suryakiran,Narasimhulu,Mahesh, K. Chinni,Venkateswarlu
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p. 2341 - 2344
(2007/10/03)
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- Efficient role of ionic liquid (bmim)HSO4 as novel catalyst for monotetrahydropyranylation of diols and tetrahydropyranylation of alcohols
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A simple procedure for the monotetrahydropyranylation of diols and alcohols, in excellent to moderate yields, has been reported using a catalytic amount of the acidic ionic liquid, 1-butyl-3-methylimidazolium hydrogensulphate (bmim)HSO4 under microwave and ultrasonic irradiation. Results have been compared with those obtained by reactions in the absence of these energies, and effectiveness of the recycled ionic liquid has also been studied. Copyright Taylor & Francis Group, LLC.
- Singh, Jasvinder,Gupta, Neeraj,Kad, Goverdhan L.,Kaur, Jasamrit
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p. 2893 - 2900
(2007/10/03)
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- Ruthenium(III) acetylacetonate [Ru(acac)3] - An efficient chemoselective catalyst for the tetrahydropyranylation (THP) of alcohols and phenols under solvent-free conditions
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A catalytic amount of ruthenium(III) acetylacetonate (2 mol%) [Ru(acac)3] enables solvent-free tetrahydropyranylation of different types of alcohols and phenols at ambient temperature in moderate to excellent yields. Notably, selective monoprotection of diols can be achieved chemoselectively. Furthermore, the catalyst could be recovered and reused if necessary.
- Varala, Ravi,Adapa, Srinivas R.
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p. 1174 - 1179
(2007/10/03)
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- A convenient multigram synthesis of highly enantioenriched methyl 3-silylglycidates
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A multigram scale synthesis of the four stereoisomers of methyl 3-silylglycidates (epoxysilanes) with high enantiopurity is described. Key reactions include a Sharpless asymmetric epoxidation (SAE) of a trans-vinylsilane and an enzymatic resolution of a r
- Lowe, Jason T.,Youngsaye, Willmen,Panek, James S.
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p. 3639 - 3642
(2007/10/03)
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- Rhodium-catalyzed asymmetric synthesis of indanones: Development of a new "axially chiral" bisphosphine ligand
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A rhodium-catalyzed asymmetric isomerization of racemic α-arylpropargyl alcohols to β-chiral indanones has been developed. High enantioselectivity has been realized by the use of a newly developed axially chiral bisphosphine ligand. This ligand is unique
- Shintani, Ryo,Yashio, Keiji,Nakamura, Tomoaki,Okamoto, Kazuhiro,Shimada, Toyoshi,Hayashi, Tamio
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p. 2772 - 2773
(2007/10/03)
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- Total synthesis of Japanese Hop Ether using an efficient intramolecular Pauson-Khand reaction
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The naturally occurring monoterpene Japanese Hop Ether has been synthesised in 14 steps in an overall yield of 29%. The key step of the synthesis, an intramolecular Pauson-Khand reaction, has been shown to proceed in good to excellent yield under mild N-oxide promotion conditions and with complete retention of alkene stereochemistry (for both cis- and trans-alkenes) in the product cyclopentenone. Georg Thieme Verlag Stuttgart.
- Caldwell, John J.,Cameron, Iain D.,Christie, Steven D. R.,Hay, Alastair M.,Johnstone, Craig,Kerr, William J.,Murray, Anthony
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p. 3293 - 3296
(2007/10/03)
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- Synthesis of disparlure analogues, using resolution on microcrystalline cellulose triacetate-I
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The gypsy moth, Lymantria dispar, uses a chiral epoxide, (+)-(7R,8S)-2-methyl-7,8-epoxyoctadecane, (+)-disparlure, as its main sex attractant. The moths can detect both enantiomers of disparlure and respond differently to each one. In an effort to understand the structure-activity relationships of the gypsy moth olfactory system, we prepared the analogues of (+)- and (-)-disparlure. The key intermediate in route to the analogues was 2-epoxytridecan-1-ol. Herein we report the resolution of 2-epoxytridecan-1-yl esters on microcrystalline cellulose triacetate and the synthesis of 5-oxa and (5Z)-ene analogues of (+)- and (-)-disparlure. An effort to make 5-aza analogues resulted in the formation of anti-5-(1-hydroxy-1-undecyl)-3-(3-methylbutyl) oxazolidin-2-one. The analogues were tested for their electroantennogram responses and for their ability to bind to pheromone-binding protein 1 (PBP1). We found that the 5-oxa analogues gave strong responses and that the antenna and the PBP1 no longer distinguish the enantiomers of the 5-oxa analogues. The analogues all bound the PBP1 with similar affinity to (-)-disparlure.
- Inkster, James A. H.,Ling, Ivy,Honson, Nicolette S.,Jacquet, Loic,Gries, Regine,Plettner, Erika
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p. 3773 - 3784
(2007/10/03)
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- Mild and efficient tetrahydropyranylation of alcohols and dehydropyranylation of THP ethers catalyzed by ferric perchlorate
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A simple, mild and efficient method for tetrahydropyranylation and dehydropyranylation of alcohols in the presence of ferric perchlorate are described.
- Heravi, Majid M.,Behbahani, Farahnaz K.,Oskooie, Hossien A.,Shoar, Rahim Hekmat
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p. 2543 - 2545
(2007/10/03)
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- Bronsted acidic ionic liquids: Fast, mild, and efficient catalysts for solvent-free tetrahydropyranylation of alcohols
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Bronsted acidic ionic liquids as efficient and reusable catalysts for the protection of alcohols as tetrahydropyranyl (THP) ethers under solvent-free conditions at room temperature was investigated. Good to excellent yields were obtained at a faster rate over [BMIm][HSO4] or [BMIm][H2PO4]. Copyright Taylor & Francis, Inc.
- Duan, Zhiying,Gu, Yanlong,Deng, Youquan
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p. 1939 - 1945
(2007/10/03)
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- Silylstannylation of allenes and silylstannylation-cyclization of allenynes. Synthesis of highly functionalized allylstannanes and carbocyclic and heterocyclic compounds
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Catalyzed by Pd(0), trialkylsilyltrialkylstannane (R3Si- SnR′3) reagents undergo highly selective additions to 1,2-dien-7-ynes and 1,2-dien-8-ynes to give 2-vinylalkylidenecyclopentanes with silicon and tin substituents on the double bonds. Similar additions of distannanes and borostannanes show that the reactions with silylstannanes are superior in terms of ease of handling of the bifunctional reagents and the isolation of the products after the reaction. The chemo- and regioselectivities are controlled by the enhanced reactivity of the allene unit, while the (Z)-geometry of the exocyclic stannylvinylidene is a consequence of the syn-carbometalation and subsequent reductive elimination from Pd with retention of configuration at the vinyl carbon. Synthesis of highly functionalized pyrrolidines and indolizidines and the reluctance of certain kinds of allenynes and silicon-tin reagents to undergo the cyclization illustrate the scope and limitations of the reaction. Based on the isolation of intermediates, a mechanism for the formation of the cyclic compounds is proposed. Model transition states to explain the stereoselectivity in cyclization of substituted allenynes are provided. Further elaboration using the vinyltin and vinylsilane moieties should lead to highly functionalized carbocyclic and heterocyclic compounds. Under similar conditions, addition of silylstannanes to highly functionalized allenes gives E-allylstannanes with high stereoselectivity. Functional groups such as THP- and silyl-ethers, lactones, β- and γ-lactams, α,β-unsaturated esters, olefins, and substituted acetylenes are tolerated under the reaction conditions.
- Kumareswaran, Ramaiah,Shin, Seunghoon,Gallou, Isabelle,RajanBabu
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p. 7157 - 7170
(2007/10/03)
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- SO3H-functionalized silica for acetalization of carbonyl compounds with methanol and tetrahydropyranylation of alcohols
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Sulfonic acid group-functionalized amorphous silica acts as a highly effective and reusable catalyst for acetalization of various carbonyl compounds with methanol and tetrahydropyranylation of alcohols.
- Shimizu, Ken-Ichi,Hayashi, Eidai,Hatamachi, Tsuyoshi,Kodama, Tatsuya,Kitayama, Yoshie
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p. 5135 - 5138
(2007/10/03)
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- CCK-1 RECEPTOR MODULATORS
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There are provided by the present invention certain pyrazole based CCK-1 receptor modulators.
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- N-(4-substituted phenyl)-anthranilic acid hydroxamate esters
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The present invention relates to oxygenated esters of 4-substituted-phenylamino benzhydroxamic acid derivatives, pharmaceutical compositions and methods of use thereof.
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- Synthesis of Ceramide Mimics with a Pseudo Cyclic Framework
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We have designed and synthesized ceramide mimics with a pseudo cyclic framework that can be converted to 'dimeric' sphingomyelins and glycosphingolipids for potential components of artificial rafts. These molecules are characterized by the presence of (i) two hydrophilic head groups, (ii) a covalently bonded hydrocarbon chain, and (iii) two untethered alkyl chains. Self-assembling of a ceramide mimic into nanorods is briefly discussed.
- Suzuki, Hikokazu,Mori, Michiko,Shibakami, Motonari
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p. 2163 - 2166
(2007/10/03)
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- Preparation, structure, and unique thermal [2 + 2], [4 + 2], and [3 + 2] cycloaddition reactions of 4-vinylideneoxazolidin-2-one
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The terminal allene Cα=Cβ bonds of 4-vinylidene-2-oxazolidinone (2) readily undergo [2 + 2] cycloaddition with a wide variety of terminal alkynes, alkenes, and 1,3-dienes irrespective of their electronic nature under strictly thermal activation conditions (70-100°C) and provide 3-substituted (Z)-methylenecyclobutenes 6, 3-substituted methylenecyclobutanes 7 and 8, and 3-vinylmethylenecyclobutanes 9, respectively, in good to excellent yields. Alkenes react with 2 with complete retention of configuration. The [2 + 2] cycloaddition is concluded to proceed via a concerted [(π2s + π2s)allene + π2s] Hueckel transition state on the basis of experimental evidences and quantum mechanical methods. Some highly polarized enones and nitrile oxide, on the other hand, react with 2 selectively at the internal C4=Cα double bonds and give spiro compounds 10 and 11, respectively. The bent allene bonds (173-176°) and the unique reactivity associated with 2 are attributed to a low-lying LUMO (Cα=Cβ) that is substantiated by a through-space σ*(N-SO2)-π*(Cα= Cβ) orbital interaction.
- Horino, Yoshikazu,Kimura, Masanari,Tanaka, Shuji,Okajima, Toshiya,Tamaru, Yoshinao
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p. 2419 - 2438
(2007/10/03)
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