885677-91-8Relevant academic research and scientific papers
Squaramide-Linked Chloramphenicol Base Hybrid Catalysts for the Asymmetric Michael Addition of 2,3-Dihydrobenzofuran-2-carboxylates to Nitroolefins
Yan, Linjie,Huang, Guanxin,Wang, Haifeng,Xiong, Fangjun,Peng, Haihui,Chen, Fener
, p. 99 - 103 (2018/01/17)
An array of hybrid catalysts incorporating a chloramphenicol base moiety linked to another chiral scaffold through a squaramide linker were developed and successfully used in the Michael addition of 2,3-dihydrobenzofuran-2-carboxylates to nitroolefins. Control experiments suggested that the hybrid catalysts were more reactive than nonhybridized bifunctional catalysts, and matching of the chirality between the two scaffolds was crucial for high reactivity and stereoselectivity. These hybrid organocatalysts could be used with a variety of substrates. At a 0.5 mol-% catalyst loading, a range of 2,3-dihydrobenzofuran-2-carboxylates derivatives bearing quaternary and tertiary stereogenic centers were obtained in high yields (up to 98 %) with excellent enantioselectivities (up to 99 % ee) and moderate diastereoselectivities (up to 8:92 dr).
Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: Possible route to the 4-methylpregabalin core structure
Vargová, Denisa,Baran, Rastislav,?ebesta, Radovan
, p. 553 - 559 (2018/03/21)
Chiral derivatives of γ-aminobutyric acid are widely used as medicines and can be obtained by organocatalytic Michael additions. We show here the stereoselective synthesis of 4-methylpregabalin stereoisomers using a Michael addition of dimethyl malonate to a racemic nitroalkene. The key step of the synthesis operates as a kinetic resolution with a chiral squaramide catalyst. Furthermore, specific organocatalysts can provide respective stereoisomers of the key Michael adduct in up to 99:1 er.
Trans -1,2-Diaminocyclohexane-based sulfonamides as effective hydrogen-bonding organocatalysts for asymmetric Michael-hemiacetalization reaction
Dajek, Maciej,Kowalczyk, Rafa?,Boratyński, Przemys?aw J.
, p. 4358 - 4363 (2018/09/11)
An easily attainable bifunctional monosulfonamide derivative of DACH was an effective catalyst for Michael addition-hemiacetalization reactions, providing products with ees exceeding 99% under optimized conditions. High enantioselectivities were achieved with just 0.2% mol catalyst loading. The sulfonamide outperformed analogous thiourea and squaramide-based organocatalysts.
Development of Chiral, Bifunctional Thiosquaramides: Enantioselective Michael Additions of Barbituric Acids to Nitroalkenes
Rombola, Michael,Sumaria, Chintan S.,Montgomery, Thomas D.,Rawal, Viresh H.
, p. 5297 - 5300 (2017/04/27)
We report a general method for the synthesis of chiral thiosquaramides, a class of bifunctional catalysts not previously described in the literature. Thiosquaramides are found to be more acidic and significantly more soluble in nonpolar solvents than their oxosquaramide counterparts, and they are excellent catalysts for the unreported, enantioselective conjugate addition reaction of the barbituric acid pharmacaphore to nitroalkenes, delivering the chiral barbiturate derivatives in high yields and high enantioselectivities, even with catalyst loadings as low as 0.05 mol%.
Kinetic Resolution of 5-Substituted Oxazinones with Bifunctional Chiral Base/Squaramide Organocatalysts
Er?ksüz, Serap,Neud?rfl, J?rg M.,Berkessel, Albrecht
, p. 1278 - 1281 (2017/06/27)
5-Substituted oxazinones provide N-protected β 2 -amino acid esters upon alcoholytic ring opening. Thus far, this access to enantiopure β 2 -amino acids has been restricted to the use of enzymes (hydrolases) as catalysts for the kine
Organocatalytic Enantioselective Vinylogous Aldol Reaction of Allyl Aryl Ketones to Activated Acyclic Ketones
Jing, Zhenzhong,Bai, Xiangbin,Chen, Wenchao,Zhang, Gao,Zhu, Bo,Jiang, Zhiyong
supporting information, p. 260 - 263 (2016/02/03)
The first catalytic asymmetric vinylogous aldol reaction of activated allyls to activated acyclic ketones is disclosed. A variety of activated acyclic ketones, such as trifluoromethyl ketones, α-ketoesters, and α-keto phosphonates, were found to be involved forming diverse γ-selective aldol adducts with high enantioselectivities (up to >99% ee). The method provides an effective, general strategy to access valuable chiral electron-withdrawing group-substituted tertiary hydroxyl-based carboxylic acids.
Enantioselective Mannich reaction of β-keto esters with aromatic and aliphatic imines using a cooperatively assisted bifunctional catalyst
Neuvonen, Antti J.,Pihko, Petri M.
supporting information, p. 5152 - 5155 (2015/01/08)
An efficient urea-enhanced thiourea catalyst enables the enantioselective Mannich reaction between β-keto esters and N-Boc-protected imines under mild conditions and minimal catalyst loading (1-3 mol %). Aliphatic and aromatic substituents are tolerated on both reaction partners, affording the products in good enantiomeric purity. The corresponding β-amino ketones can readily be accessed via decarboxylation without loss of enantiomeric purity.
Enantioselective Michael addition of 1,3-dicarbonyl compounds to a nitroalkene catalyzed by chiral squaramides-a key step in the synthesis of pregabalin
Baran, Rastislav,Veverkova, Eva,Skvorcova, Andrea,Sebesta, Radovan
, p. 7705 - 7711 (2013/11/06)
Asymmetric organocatalytic 1,4-additions provide access to a large number of biologically relevant compounds. Chiral squaramides efficiently catalyse enantioselective Michael addition of 1,3-dicarbonyl compounds to aliphatic nitroalkenes. The resulting γ-
Design and development of bioinspired guanine-based organic catalyst for asymmetric catalysis
Suez, Gal,Bloch, Victoria,Nisnevich, Gennady,Gandelman, Mark
, p. 2118 - 2122 (2012/06/01)
Design, preparation, and studies of a family of new organic catalysts are presented. The design of the catalysts is inspired by the ability of DNA nucleobases to develop precise and explicit hydrogen bonds. We have shown that this phenomenon can be used to create a useful organic catalyst that demonstrates a recognition pattern similar to those of common organic substrates. A selected bifunctional catalyst based on a guanine structure has been shown to catalyze the conjugate addition of 1,3-dicarbonyl compounds to various nitroalkenes, providing the products in good yields and enantioselectivities.
Squaramide-catalyzed enantioselective michael addition of diphenyl phosphite to nitroalkenes
Zhu, Ye,Malerich, Jeremiah P.,Rawal, Viresh H.
supporting information; experimental part, p. 153 - 156 (2010/03/30)
chemical equation presented Michael's a square: An easily prepared squaramide catalyst that promotes the highly enantioselective Michael addition reaction of diphenyl phosphite to a range of nitroalkenes is described. This method leads to chiral β-nitro phosphonates, which are precursors to biologically active β-amino phosphonic acids.
