نتایج جستجو برای: organocatalyst

تعداد نتایج: 407  

Journal: :Chemistry, an Asian journal 2007
Shu-Li You

By utilizing Hantzsch esters as the hydrogen source, asymmetric transfer hydrogenation of C=C, C=N, and C=O is realized in the presence of an organocatalyst or a metal-ligand complex, thus affording versatile chiral building blocks in high yields with excellent enantioselectivities under mild conditions. A detailed discussion of recent findings and an assessment of this biomimetic approach are ...

2018
Aitor Urosa Ignacio E Tobal Ángela P de la Granja M Carmen Capitán R F Moro Isidro S Marcos Narciso M Garrido Francisca Sanz Emilio Calle David Díez

A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potentia...

Journal: :European Journal of Organic Chemistry 2021

Self-assembling minimalistic peptides embedded with an organocatalytic moiety were designed. By controlling the formation of fibrils via external intervention, it was shown that activation is accelerated when organocatalyst in its supramolecular state. The effect catalysis demonstrated a Michael benchmark reaction.

Journal: :Chemical communications 2018
Pablo Martínez-Pardo Gonzalo Blay M Carmen Muñoz José R Pedro Amparo Sanz-Marco Carlos Vila

A multicatalytic approach that combines a bifunctional Brønsted base-squaramide organocatalyst and Ag+ as Lewis acid has been applied in the reaction of unactivated ketones with tert-butyl isocyanoacetate to give chiral oxazolines bearing a quaternary stereocenter. The formal [3+2] cycloaddition provided high yields of the corresponding cis-oxazolines with good diastereoselectivity and excellen...

Journal: :Journal of the American Chemical Society 2004
Stephanie S Sohn Evelyn L Rosen Jeffrey W Bode

N-Heterocyclic carbenes, prepared in situ from diarylimidazolium salts, serve as highly effective catalysts for the generation of reactive homoenolates from alpha,beta-unsaturated aldehydes. The catalyst-bound homoenolate reacts with electrophilic aldehydes leading, via the key intermediacy of an activated carboxylate, to gamma-butyrolactones in good yields and stereoselectivities. Importantly,...

Journal: :Molecules 2015
Fernando Auria-Luna Eugenia Marqués-López Somayeh Mohammadi Roghayeh Heiran Raquel P Herrera

Herein, we report our preliminary results concerning the first promising asymmetric synthesis of highly functionalized 2-oxospiro-[indole-3,4'-(1',4'-dihydropyridine)] via the reaction of an enamine with isatylidene malononitrile derivatives in the presence of a chiral base organocatalyst. The moderate, but promising, enantioselectivity observed (30%-58% ee (enantiomeric excess)) opens the door...

Journal: :Chemical communications 2012
Tyler A Davis Michael W Danneman Jeffrey N Johnston

The first enantioselective synthesis of a potent GlyT1 inhibitor is described. A 3-nitroazetidine donor is used in an enantioselective aza-Henry reaction catalyzed by a bis(amidine)-triflic acid salt organocatalyst, delivering the key intermediate with 92% ee. This adduct is reductively denitrated and converted to the target through a short sequence, thereby allowing assignment of the absolute ...

Journal: :Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan 2010
Kenichi Murai

This review describes the first method to prepare imidazolines from aldehydes and 1,2-diamines by condensation and successive oxidation using NBS in one-pot operation. The reaction proceeds under mild conditions and can be applied to various aromatic and aliphatic aldehydes and 1,2-diamines. The utility of this method is also demonstrated in the total synthesis of spongotine A and the preparati...

Journal: :Journal of the American Chemical Society 2010
Hui-Wen Shih Mark N Vander Wal Rebecca L Grange David W C MacMillan

The first enantioselective aldehyde α-benzylation using electron-deficient aryl and heteroaryl substrates has been accomplished. The productive merger of a chiral imidazolidinone organocatalyst and a commercially available iridium photoredox catalyst in the presence of household fluorescent light directly affords the desired homobenzylic stereogenicity in good to excellent yield and enantiosele...

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