- Synthesis of new 3,4-disubstituted pyrrolidines as thromboxane A2/prostaglandin H2 (TP) receptor antagonists
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The synthesis and TP-receptor antagonistic activity of a series of 3,4-disubstituted pyrrolidines is described. The sulfonamide 1h was the most potent TP-receptor antagonist in this series with a pA2 value of 9.5 in isolated guinea pig trachea.
- Dubuffet, Thierry,Muller, Olivier,Simonet, Serge S.,Descombes, Jean-Jacques,Laubie, Michel,Verbeuren, Tony J.,Lavielle, Gilbert
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- Diastereoselective Synthesis of trans-2,3-Diaryl(heteroaryl)-3,6-dihydropyrans by an Allylboration/Ring-Closing-Metathesis Sequence
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trans-2,3-Diaryl(heteroaryl)-dihydropyrans were synthesized by an allylboration/ring-closing-metathesis sequence, using allylboranes formed in situ from the corresponding allylic alcohols. Aryl(heteroaryl) substituents were thus installed diastereoselectively onto dihydropyran rings in a trans fashion. These disubstituted dihydropyrans were further transformed into monosaccharide-like tetrahydropyrans.
- Nocquet, Pierre-Antoine,Corbu, Andrei,Meerpoel, Lieven,Stansfield, Ian,Berthelot, Didier,Angibaud, Patrick,Cossy, Janine
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supporting information
p. 3343 - 3354
(2017/06/29)
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- Microwave-Assisted Synthesis of Phenylpropanoids and Coumarins: Total Synthesis of Osthol
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Herein we describe a one-pot microwave-assisted method for the synthesis of cinnamic acid and coumarin derivatives. The synthesis begins with an aldehyde synthon, and the chosen reaction conditions determine whether a cinnamic acid or coumarin derivative is formed. A regioselective Claisen rearrangement was also efficiently incorporated into the synthetic sequence to further increase the complexity of the product. Notably, this approach provides high product yields and selectivities without the need of a phenol protecting group.
- Konrádová, Daniela,Kozubíková, Hana,Dole?al, Karel,Pospí?il, Ji?í
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supporting information
p. 5204 - 5213
(2017/09/29)
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- Phospholane-catalyzed wittig reaction
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We identified 2-phenylisophosphindoline 2-oxide as a suitable and potentially tunable catalyst for the catalytic Wittig reaction of aldehydes with activated organohalides. This catalyst was obtained by a straightforward two-step synthesis. Trimethoxysilane proved to be an efficient reducing agent for the in situ generation and regeneration of the catalyst from the corresponding phosphane oxide. Sodium carbonate was identified as a suitable base for the transformation. It is noteworthy that the particle size of the sodium carbonate had a tremendous effect on the outcome of the reaction. Under the optimized reaction conditions, 23 aldehydes were converted into the corresponding alkenes in high isolated yields of up to 88%. Moreover, an asymmetric catalytic Wittig reaction was performed for the desymmetrization of a prochiral diketone.
- Werner, Thomas,Hoffmann, Marcel,Deshmukh, Sunetra
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p. 3286 - 3295
(2015/05/20)
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- Scope and Limitation of the Microwave-Assisted Catalytic Wittig Reaction
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We have developed a microwave-assisted catalytic Wittig reaction. In this paper, we give full account of the scope and limitations of this reaction. A screening of various commercially available phosphine oxides as precatalysts revealed Bu3P=O to be the most promising candidate. We tested 10 silanes for the in situ reduction of the phosphine oxide to generate Bu3P as the actual catalyst. Different epoxides were tested as masked bases. In this context, cyclohexene oxide as well as butylene oxide proved to be suitable. The reaction could be carried out at 125 C, but higher yields and E/Z selectivities were obtained at 150 °C. Under the optimised reaction conditions, more than 40 examples for the conversion of various aldehydes into the corresponding alkenes are reported. The products were obtained in yields of up to 88 with high E selectivities. Moreover, we also describe the further screening of several chiral phosphines as catalysts for the microwave-assisted enantioselective catalytic Wittig reaction. The scope and limitations of the microwave-assisted catalytic Wittig reaction have been evaluated with respect to the catalyst, silane, solvent, reaction conditions, and substrates.
- Hoffmann, Marcel,Deshmukh, Sunetra,Werner, Thomas
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p. 4532 - 4543
(2015/07/27)
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- Mild synthesis of mesoporous silica supported ruthenium nanoparticles as heterogeneous catalysts in oxidative Wittig coupling reactions
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A new efficient approach for the in situ synthesis of anchored ruthenium nanoparticles (RuNP) in three different kinds of mesoporous silica materials, MCM-41, SBA-15 and HMS, has been developed. Solids have been synthesized under very mild conditions from RuCl3·H2O salt reduced in one hour at room temperature in the mesoporous silicas previously grafted with aminopropyltriethoxysilane (APTES). Well-dispersed ruthenium nanoparticles, with an average size of 3 nm, anchored into the silica network by the APTES were obtained. These materials, with a molar ratio of Si/Ru = 40, were found to be catalytically active and selective in the alcohol oxidation-Wittig olefination. Interestingly, while the reaction occurs from the alcohol, control experiments suggest that the aldehyde (the common Wittig substrate) is not involved. The Royal Society of Chemistry.
- Carrillo, Adela I.,Schmidt, Luciana C.,Marin, M. Luisa,Scaiano, Juan C.
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supporting information
p. 435 - 440
(2014/02/14)
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- Templating photodimerization of trans-cinnamic acid esters with a water-soluble Pd nanocage
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A water-soluble octahedral Pd nanocage acting as a reaction vessel templates the photodimerization of substituted trans-cinnamic acid methyl esters in water. Irradiation of the host-guest complexes of trans-cinnamic acid methyl esters with the Pd nanocage resulted in selective formation of a syn head-head dimer in addition to the corresponding cis isomer. These results suggest that the guest molecules are preoriented in a selective fashion with the hydrophilic ester group facing water and the hydrophobic aryl group tucked within the cavity of the host. Such an orientation occurs at the hydrophobic-hydrophilic interface between the nanocage exterior and interior. Weak intermolecular C-H-π and π-π interactions between the host and the guest(s) are likely to be responsible for the lack of mobility of the reactant olefins during their short excited-state lifetime.
- Karthikeyan,Ramamurthy
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p. 452 - 458
(2007/10/03)
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- Wittig reactions in water media employing stabilized ylides with aldehydes. Synthesis of α,β-unsaturated esters from mixing aldehydes, α-bromoesters, and Ph3P in aqueous NaHCO3
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(Chemical Equation Presented) Water is demonstrated to be an effective medium for the Wittig reaction over a wide range of stabilized ylides and aldehydes. Despite sometimes poor solubility of the reactants, good chemical yields normally ranging from 80 to 98% and high E-selectivities (up to 99%) are achieved, and the rate of the reactions in water is unexpectedly accelerated. The efficiency of water as a medium in the Wittig reaction is compared to conventional organic solvents ranging from carbon tetrachloride to methanol. The aqueous Wittig reaction works best when large hydrophobic entities are present, such as aromatic, heterocyclic aromatic carboxaldehydes, and long-chain aliphatic aldehydes with triphenylphosphoranes. The E/Z-isomeric ratio of the Wittig products appears dependent on the electron-accepting/donating capacity and the location of the substituents present in the aromatic ring. The effect of additives, such as benzoic acid, LiCl, and sodium dodecyl sulfate (SDS), on the Wittig reaction has been explored. The Wittig reaction can also be conducted in the presence of acidic entities, such as phenols and carboxylic acids. In addition, large α-substituents in the aliphatic aldehydes do not jeopardize the reaction. It is also demonstrated that hydrates of aldehydes can be used directly in the aqueous Wittig reaction as substrates. The scope of the aqueous Wittig reaction is extended to 24 examples of one-pot mixtures of Ph3P, α-bromoesters, and aldehydes in sodium bicarbonate solution (at 20°C for 40 min to 3 h) to provide Wittig products of up to 99% yield and up to 98% E-selectivity. Since water is inexpensive, extremely easy to handle, and represents no environmental concerns, it should be considered a possible medium for new organic reactions.
- El-Batta, Amer,Jiang, Changchun,Zhao, Wen,Anness, Robert,Cooksy, Andrew L.,Bergdahl, Mikael
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p. 5244 - 5259
(2008/02/07)
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- Diastereoselective method of preparing olefins by means of the horner-wadsworthemmons reaction, comprising the addition of a tris-(polyoxaalkyl)-amine sequestering agent
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The invention relates to a process for the diastereoselective preparation of olefins via the Homer-Wadsworth-Emmons reaction, which consists in reacting at low temperature a phosphonate with a carbonyl derivative in the presence of a base in a suitable solvent, characterized in that a tris(polyoxaalkyl)amine sequestering reagent of formula (I): N—[CHR1—CHR2—O—(CHR3—CHR4—O)n—R5]3 (I), wherein: n is an integer between 0 and 10; R1, R2, R3 and R4 may be identical or different, and represent a hydrogen atom or an alkyl radical containing from 1 to 4 carbon atoms; R5 represents a hydrogen atom, an alkyl or cycloalkyl radical containing up to 12 carbon atoms, a phenyl radical or a radical of formula —CμH2μ-Φ, or CmH2m+1-Φ-, with m being an integer between 1 and 12 and Φ being a phenyl radical; is added in an amount that is sufficient to increase the diastereoselectivity of the olefin.
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Page/Page column 5-6
(2010/11/08)
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- New and efficient conditions for the Z-selective synthesis of unsaturated esters by the Horner-Wadsworth-Emmons olefination
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The Horner-Wadsworth-Emmons reaction of both 1 (Still's reagent) and 2 (Ando's reagent) with aldehydes was studied. Tris[2-(2-methoxyethoxy)ethyl]amine (TDA-1) was shown to be an efficient additive when the reaction was performed in THF at -78°C. Selectivities close to 95% were obtained in the condensation of 1 with aromatic aldehydes. The use of a 5-fold excess of 18C6 in this reaction had already been reported. However, we have defined conditions in which only catalytic amounts are required.
- Touchard, Fran?ois P.
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p. 5519 - 5523
(2007/10/03)
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- A catalytic asymmetric synthesis of chiral glycidic acid derivatives through chiral dioxirane-mediated catalytic asymmetric epoxidation of cinnamic acid derivatives
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A novel and practical asymmetric synthesis of chiral glycidic acid derivatives involving methyl (2R,3S)-3-(4-methoxyphenyl)glycidate ((2R,3S)-2a), a key intermediate for diltiazem hydrochloride (1), was developed. Treatment of methyl (E)-4-methoxycinnamate ((E)-3a) with chiral dioxirane, generated in situ from a catalytic amount (5 mol %) of an 11-membered C2-symmetric binaphthyl ketone (R)-7a, provided (2R,3S)-2a in 92% yield and 80% ee. Other cinnamic acid esters and amides were epoxidized by the use of the same procedure to give the corresponding chiral glycidic acid derivatives with up to 95% yield and 92% ee. Higher enantioselectivities in the asymmetric epoxidation of (E)-cinnamates than that of (E)-stilbene derivatives were observed and were proposed to be attributed to a dipole-dipole repulsion between oxygen atoms of an ester group in the cinnamates and those of the lactone moieties in the binaphthyl dioxirane.
- Imashiro, Ritsuo,Seki, Masahiko
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p. 4216 - 4226
(2007/10/03)
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- MECHANISM OF DECARBALKOXYLATION OF ARYLMETHYLENE-PROPANEDIOIC ACID DIMETHYL ESTERS
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The decarbalkoxylation in DMSO-NaX-H2O, of some arylmethylene propanedioic acid dimethyl esters is studied.Both the relative rates of the para (R = NO2, H, CH3, OCH3) and the ortho substituted aryl derivatives, together with the stereochemical outcome, support a preliminary nucleophilic attack by water followed by decarboxylative elimination.
- Bernard, Angela M.,Cerioni, Giovanni,Piras, Pier Paolo
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p. 3929 - 3940
(2007/10/02)
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- STEREOCHEMISTRY OF DECARBALKOXYLATION OF ARYLMETHYLENE-PROPANEDIOIC ACIDS DIMETHYL ESTERS
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Halide ions increase the rate of decarbalkoxylation of arylmethylene-propanedioic acids dimethyl esters.
- Bernard, Angela M.,Piras, P. Paolo,Serra, Adriana
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p. 4391 - 4392
(2007/10/02)
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- A Facile Ring-opening of Coumarins: Synthesis of Furopinnarin
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A facile synthesis of furopinnarin through ring-opening of coumarin is achieved in high yield.The ring opening has been successfully applied on a number of coumarins and furocoumarins to generalise the reaction.
- Kaul, S. K.,Sehgal, C. K.,Taneja, S. C.,Dhar, K. L.,Atal, C. K.
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p. 472 - 474
(2007/10/02)
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