1255928-97-2Relevant articles and documents
Combining organocatalysis with photoorganocatalysis: photocatalytic hydroacylation of asymmetric organocatalytic Michael addition products
Schiza, Andriana,Spiliopoulou, Nikoleta,Shahu, Adelajda,Kokotos, Christoforos G.
, p. 18844 - 18849 (2018)
Organocatalysis and photoorganocatalysis are two areas of synthetic methodology that have found wide applications in organic synthesis. Herein, we report a combination of these two stategies, taking advantage of an organocatalytic Michael addition of α,α-disubstituted aldehydes to maleimides as the first step and a photocatalytic hydroacylation of diisopropyl azodicarboxylate as the second step. Employing an amino acid as the organocatalyst for the asymmetric organocatalytic part and an organic molecule as the photocatalyst, the combination of these two strategies led to the desired products. A number of alkyl- and aryl-substituted maleimides were successfully employed, while the protocol can be used on α,α-disubstituted aldehydes leading to products in moderate to high yields (44-84%) and excellent enantioselectivities (98-100% ee).
Calixarene-based chiral primary amine thiourea promoted highly enantioselective asymmetric Michael reactions of α,α-disubstituted aldehydes with maleimides
Durmaz, Mustafa,Sirit, Abdulkadir
, p. 1443 - 1448 (2013/12/04)
Calix[4]arene based chiral bifunctional thiourea-primary amines have been shown to act as effective catalysts for the Michael addition of aldehydes to maleimides for the first time. The corresponding adducts were generally obtained preferentially in (R)-
Noncovalent bifunctional organocatalysts: Powerful tools for contiguous quaternary-tertiary stereogenic carbon formation, scope, and origin of enantioselectivity
Nugent, Thomas C.,Sadiq, Abdul,Bibi, Ahtaram,Heine, Thomas,Zeonjuk, Lei Liu,Vankova, Nina,Bassil, Bassem S.
supporting information; experimental part, p. 4088 - 4098 (2012/06/01)
Relying on the assembly of commercially available catalyst building blocks, highly stereocontrolled quaternary carbon (all carbon substituted) formation has been achieved with unmatched substrate diversity. For example, the in situ assembly of a tricomponent catalyst system allows α-branched aldehyde addition to nitroalkene or maleimide electrophiles (Michael products), while addition to an α-iminoester affords Mannich reaction products. Very good yields are observed and for fifteen of the eighteen examples 96-99 % ee is observed. Using racemic α-branched aldehydes, two contiguous (quaternary-tertiary) stereogenic centers can be formed in high diastereo- and enantiomeric excess (eight examples) via an efficient in situ dynamic kinetic resolution, solving a known shortcoming for maleimide electrophiles in particular. The method is of practical value, requiring only 1.2 equiv of the aldehyde, a 5.0 mol % loading of each catalyst component, for example, O-tBu-L-threonine (O-tBu-L-Thr), sulfamide, DMAP or O-tBu-L-Thr, KOH, and room temperature reactions. As a highlight, the first demonstration of ethylisovaleraldehyde (7) addition is disclosed, providing the most congested quaternary stereogenic carbon containing succinimide product (8) known to date. Finally, mechanistic insight, via DFT calculations, support a noncovalent assembly of the catalyst components into a bifunctional catalyst, correctly predict two levels of product stereoselectivity, and suggest the origin of the tricomponent catalyst system's exceptionality: an alternative hydrogen bond motif for the donor-acceptor pair than currently suggested for non-assembled catalysts. Noncovalent by nature: Commercially available building blocks allow in situ formation of bifunctional organocatalysts for the enantioselective formation of quaternary carbons (see scheme). This new catalyst approach is general in nature and the catalyst platform is readily adaptable. Copyright
A highly efficient asymmetric Michael addition of α,α- disubstituted aldehydes to maleimides catalyzed by primary amine thiourea salt
Yu, Feng,Jin, Zhichao,Huang, Huicai,Ye, Tingting,Liang, Xinmiao,Ye, Jinxing
experimental part, p. 4767 - 4774 (2010/11/20)
The first highly efficient Michael addition of challenging α,α-disubstituted aldehydes to maleimides catalyzed by a simple bifunctional primary amine thiourea catalyst/benzoic acid system has been successfully developed to generate quaternary carbon cente
