- Chiral magnesium(II) binaphtholates as cooperative bronsted/lewis acid-base catalysts for the highly enantioselective addition of phosphorus nucleophiles to α,β-unsaturated esters and ketones
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A little cooperation goes a long way: The cooperative Bronsted/Lewis acid-base supramolecular catalysts formed in situ from simple chiral magnesium(II) binaphtholate aqua complexes promoted the highly enantioselective 1,4-hydrophosphinylation of α,β-unsaturated esters with diaryl phosphine oxides and 1,2-hydrophosphonylation of α,β-unsaturated ketones with dialkyl phosphites (see scheme). Copyright
- Hatano, Manabu,Horibe, Takahiro,Ishihara, Kazuaki
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supporting information
p. 4549 - 4553
(2013/06/04)
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- Enantioselective synthesis of 2-arylbicyclo[1.1.0]butane carboxylates
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The rhodium-catalyzed reaction of 2-diazo-5-arylpent-4-enoates can be controlled by the appropriate choice of catalyst and catalyst loading to form either 2-arylbicyclo[1.1.0]butane carboxylates or cyclohexene derivatives. Both products are produced in a
- Qin, Changming,Davies, Huw M. L.
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supporting information
p. 310 - 313
(2013/03/13)
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- Polymer-assisted solution-phase synthesis under combined ultrasound and microwave irradiation: Preparation of α,β-unsaturated esters and carboxylic acids, key intermediates of novel sigma ligands
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The optimal conditions to prepare α,β-unsaturated methyl esters via Wittig reaction combining polymer-assisted solution-phase synthesis (PASPS) methodology and simultaneous ultrasound and microwave irradiation were established. The effects of temperature, solvent, and irradiation time were discussed. Results clearly indicated the superiority of combined ultrasound and microwave-assisted procedure over microwave-assisted methodology. Moreover, an efficient PASPS procedure to prepare α,β-unsaturated carboxylic acids via tandem Wittig olefination and hydrolysis reaction was developed under combined ultrasound and microwave irradiation. Generally, a good conversion of aldehydes to acids was observed. The optimized protocols allowed us to quickly prepare a small collection of either α,β-unsaturated esters or carboxylic acids, key intermediates for the drug-discovery process of new sigma ligands. Copyright Taylor & Francis Group, LLC.
- Rossi,Urbano,Baraglia, A. Carnevale,Serra,Bergamelli,Iannelli,Azzolina,Collina
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experimental part
p. 3254 - 3262
(2011/03/18)
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- Sequential cross-metathesis/phosphorus-based olefination: stereoselective synthesis of 2,4-dienoates
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A variety of stereodefined 2,4-dienoates have been prepared in a stereoselective manner by sequencing olefin cross-metathesis (CM) with phosphorus-based olefination reactions (Wittig and Horner-Wadsworth-Emmons) in good yield using commercially available reagents.
- Paul, Tapas,Andrade, Rodrigo B.
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p. 5367 - 5370
(2008/02/10)
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- Water is an efficient medium for Wittig reactions employing stabilized ylides and aldehydes
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Water is demonstrated to be an excellent medium for the Wittig reaction employing stabilized ylides and aldehydes. Although the solubility in water appears to be an unimportant characteristic in achieving good chemical yields and E/Z-ratios, the rate of W
- Dambacher, Jesse,Zhao, Wen,El-Batta, Amer,Anness, Robert,Jiang, Changchun,Bergdahl, Mikael
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p. 4473 - 4477
(2007/10/03)
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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 study on the Z-selective Horner-Wadsworth-Emmons (HWE) reaction of methyl diarylphosphonoacetates
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Experimental and theoretical studies were conducted to explore the Z-selectivities in the Horner-Wadsworth-Emmons (HWE) reaction employing several methyl diarylphosphonoacetates (3, 4, 5 and 6) and aldehydes. The Z-selectivity depended upon the reaction conditions such as the bases, reaction temperature, and the aromatic substituents on the phosphorus atoms but the almost phosphonoacetates used in the present study showed Z-selectivity in the reactions with both aromatic and aliphatic aldehydes. While the phosphonoacetate (3) with bis(2,4-difluorophenyl)phosphono group showed the highest Z-selectivity in all reaction conditions employed, decrease of the selectivity was observed in the case of some phosphonoacetates with diarylphosphono groups. These experimental results and the theoretical studies calculated by AM1 or 3-21G* ab initio methods suggested that the steric effect in the transition states of the addition steps was important rather than the electronic effect. A different aspect of the reaction courses between the Wittig and HWE reactions in the present computational chemistry was also described.
- Kokin, Keisuke,Iitake, Ken-Ichro,Takaguchi, Yutaka,Aoyama, Hiromu,Hayashi, Sadao,Motoyoshiya, Jiro
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- A NEW METHOD FOR CARBON-CARBON DOUBLE BOND FORMATION PROMOTED BY TRI-n-BUTYLPHOSPHINE AND ZINC
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A new method for the carbon-carbon double bond formation by the reaction of aldehydes with methyl bromoacetate promoted by tri-n-butylphosphine and zinc has been described.
- Shen, Yanchang,Xin, Yuankang,Zhao, Jianhua
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p. 6119 - 6120
(2007/10/02)
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