نتایج جستجو برای: organocatalyst
تعداد نتایج: 407 فیلتر نتایج به سال:
A novel pyrrolidine-based chiral phosphoproline is an effective bifunctional organocatalyst for the asymmetric Michael addition of ketones to nitroolefins giving high levels of diastereo- and enantio-selectivities (up to > 99 : 1 dr and 96% ee). anti-SR Transition state has the lowest barrier which controls the stereoselectivity, in agreement with experimental results.
PEP and aldolase mimicry is the key for a direct organocatalytic entry to precursors of ulosonic acids, biomolecules of enormous importance in biology, chemistry and medicine; in the key aldol reaction the dimethylacetal of pyruvic aldehyde is used as phosphoenolpyruvate (PEP) equivalent and the amino acid proline functions as an organocatalyst, imitating the enzyme.
The synthesis of a second-generation [6]-helicenoidal DMAP organocatalyst is reported. The synthesis is reliant upon a highly diastereoselective Rh-catalysed [2 + 2 + 2] triyne cycloisomerization, using an existing stereocentre to control the sense of forming helicity. Taken together, a scalable (>1 g), resolution-free entry to a helical DMAP with the capacity for subsequent functionalization, ...
We discovered a novel organocatalysed multicomponent domino Knoevenagel-aza-Michael-cyclocondensation reaction leading to an unprecedented straightforward synthesis of 1,5-diazabicyclo[3.3.0]octane-2,6-diones. The specific capability of the (DHQ)2PHAL organocatalyst in this process was also highlighted to eventually furnish the corresponding bicyclopyrazolidinones with up to 96 : 4 er.
Disclosed herein are structures designed to incorporate pyrrolidine, which is a privileged organocatalyst structure, and bipyridine, among the most widely used metal ligands. Robust scalable synthetic routes five such compounds have been established. These novel may be useful in metal-organic cooperative catalyzed transformations, or as organocatalysts
An efficient asymmetric synthesis of 11-β-HSD inhibitor 1 has been accomplished in five linear steps and 53% overall yield, starting from the readily available 3-chloro-1-phenylpropan-1-one. The key feature of the synthesis includes an asymmetric methallylation of 3-chloro-1-phenylpropan-1-one catalyzed by the highly effective organocatalyst (S)-3,3'-F2-BINOL under solvent-free and metal-free c...
To map out the efficient organocatalyst requirements in the Michael addition of 1,3-dicarbonyl indane compounds to nitrostyrenes, a dozen different amino organocatalysts containing a p-toluenesulfonyl group (Ts) have been evaluated; excellent enantio-selectivities (up to er 92:8) were obtained with a primary amine-based Ts-DPEN catalyst and a plausible catalytic reaction mechanism was proposed ...
A highly enantio- and diastereoselective sulfa-Michael addition of thioacetic acid to α,β-disubstituted nitroalkenes catalysed by a chiral squaramide organocatalyst has been described. This organocatalytic reaction at an extremely low catalyst loading (0.2 mol%) furnished synthetically useful β-nitro sulfides in excellent yields with good diastereoselectivities and high enantioselectivities (up...
A novel organocatalyst was developed that effectively catalyzed the reactions of unprotected or protected dihydroxyacetone with a variety of aldehydes to provide syn-aldol products with good yields and ee values up to >99%. Significantly, this amide catalyst was effective with a variety of nonaromatic aldehyde acceptors that had proven difficult in the presence of other catalysts. Reactions of ...
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