Higher enantioselectivities in thiourea-catalyzed Michael additions under solvent-free conditions

Hestericová, Martina; Šebesta, Radovan

doi:10.1016/j.tet.2013.12.029

Cited by 39 publications

(15 citation statements)

References 60 publications

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“…As the hydrogen bonds are particularly sensitive to the solvent, the application of ball-milling could be the route to increase their strength and, in consequence, the effectiveness of catalysis involving hydrogen-bonding. [25] An additional effect exerted on reaction kinetics stems from heating by friction. These features of milling appeared relevant to the studied Michael addition of nitromethane to en-ynone A1.…”

Section: Resultsmentioning

confidence: 99%

Applications of Thermal Activation, Ball‐milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides

et al. 2019

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Stereoselective addition of nitromethane to conjugated en-ynones was performed through the application of chiral squaramides. Three non-classical approaches to promote the addition reaction were tested, including activation of the nucleophile by inorganic base in a biphasic aqueous system, thermal activation, and ball-milling. Hydrogen-bonding catalysis was effective in all these methods, providing 1,4addition products in high yields and stereoselectivities of up to 98% requiring 1-5 mol% of Cinchona alkaloid squaramide.

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Section: Resultsmentioning

confidence: 99%

Applications of Thermal Activation, Ball‐milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides

et al. 2019

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“…In 2014, Sebesta and co‐worker examined Michael addition with different commercially available or synthesized bifunctional hydrogen‐bonding catalysts based on thioureas and squaramides include Jacobsen‐ and Takemoto‐catalysts . Michael addition of indole or dimethyl malonate to trans‐nitrostyrene as a model reaction was carried out in different conditions such as vibrational ball mill, dry stirring and solution (CH 2 Cl 2 ) using 20 mol % of the corresponding bifunctional organocatalyst (Scheme ).…”

Section: Solvent‐free Reactions In Asymmetric Catalysismentioning

confidence: 99%

“…In 2014, Sebesta and co-worker examined Michael addition with different commercially available or synthesized bifunctional hydrogen-bonding catalysts based on thioureas and squaramides include Jacobsen-and Takemoto-catalysts. [78] Michael addition of indole or dimethyl malonate to trans-nitrostyrene as a model reaction was carried out in different conditions such as vibrational ball mill, dry stirring and solution (CH 2 Cl 2 ) using 20 mol % of the corresponding bifunctional organocatalyst (Scheme 56). Interestingly, the obtained results revealed that the solvent-free conditions by use of all organocatalysts led to higher enantioselectivities for the corresponding product and enantiomeric ratio decreased in solution condition due to disrupting of hydrogen-bonding between catalyst and reactants.…”

Section: Asymmetric Michael Reactionmentioning

confidence: 99%

Recent Advances in Solvent‐Free Asymmetric Catalysis

2019

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It is well‐known that solvent is one of the most important factors that affect chemical reactions. This factor is more noticeable and impressive in the asymmetric reactions where the effective interaction of reactants and the creation of a uniform chiral environment is necessary. Nevertheless, when reactions are carried out in the absence of solvent, some privileged advantages such as easy work up, short reaction time, lack of waste solvents, and following the green chemistry principles, are appeared. Therefore, according to the importance of asymmetric synthesis and green chemistry, solvent‐free asymmetric catalysis can act as a considerable and necessary subject in synthetic chemistry. In this review, we have a survey on the solvent‐free asymmetric synthesis by the use of either homogeneous or heterogeneous chiral catalysts.

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“…In particular, evaluation was reported of several chiral thiourea-containing cinchonas, binaphthyls, and squaramides and bis-thioureas as organocatalysts under solvent-free conditions using LAG to obtain enantioenriched Michael adducts (Scheme 4.8). 39 Reaction yields were significantly improved relative to the reactions carried out in solution.…”

Section: Asymmetric Michael Additionmentioning

confidence: 99%

“…Asymmetric Michael addition organocatalyzed by cinchona and L-Binam-thioureas 10 and 11 in a ball-mill 39. …”

mentioning

confidence: 99%

CHAPTER 4. Asymmetric Organocatalytic Reactions under Ball Milling

Machuca¹,

Juaristi²

2014

Green Chemistry Series

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Higher enantioselectivities in thiourea-catalyzed Michael additions under solvent-free conditions

Cited by 39 publications

References 60 publications

Applications of Thermal Activation, Ball‐milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides

Applications of Thermal Activation, Ball‐milling and Aqueous Medium in Stereoselective Michael Addition of Nitromethane to Enynones Catalyzed by Chiral Squaramides

Recent Advances in Solvent‐Free Asymmetric Catalysis

CHAPTER 4. Asymmetric Organocatalytic Reactions under Ball Milling

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