1212469-34-5Relevant articles and documents
Densely substituted l -proline esters as catalysts for asymmetric michael additions of ketones to nitroalkenes
Ruiz-Olalla, Andrea,Retamosa, María De Gracia,Cossío, Fernando P.
, p. 5588 - 5599 (2015)
Homochiral methyl 4-aminopyrrolidine-2-carboxylates are readily obtained by means of asymmetric (3 + 2) cycloadditions between azomethine ylides and nitroalkenes, followed by catalytic hydrogenation of the intermediate 4-nitro cycloadducts. These 4-aminopyrrolidine-2-carboxylate esters belong to the l-series of natural amino acids and catalyze asymmetric Michael additions of ketones to nitroalkenes. However, the enantioselectivity observed with these novel unnatural organocatalysts is opposite to that obtained with l-proline. Since both 4-nitro and 4-amino l-proline esters are efficient organocatalysts of aldol reactions, these results permit to modulate asymmetric quimioselective aldol and conjugate addition reactions.
Sugar-based pyrrolidine as a highly enantioselective organocatalyst for asymmetric michael addition of ketones to nitrostyrenes
Wang, Lei,Liu, Jie,Miao, Tao,Zhou, Wei,Li, Pinhua,Ren, Kai,Zhang, Xiuli
, p. 2571 - 2578 (2010)
A modular sugar-based pyrrolidine (3) was prepared and was found to be a highly enantioselective organocatalyst for the asymmetric Michael addition of ketones to nitrostyrenes. In the presence of 10 mol% of 3, a pyrrolidine unit anchored to a natural D-gl
Pyrrolidine-pyridinium based organocatalysts for highly enantioselective Michael addition of cyclohexanone to nitroalkenes
Xu, Dan-Qian,Wang, Bing-Tao,Luo, Shu-Ping,Yue, Hua-Dong,Wang, Li-Ping,Xu, Zhen-Yuan
, p. 1788 - 1794 (2007)
A novel class of pyrrolidine-pyridinium based organocatalysts has been developed and demonstrated to efficiently catalyze the asymmetric Michael addition reactions of unmodified cyclohexanone to nitroalkenes in the ionic liquid BMImBF4 with up
Comparison of different polymer- and silica-supported 9-amino-9-deoxy-epi-quinines as recyclable organocatalysts
Porta, Riccardo,Coccia, Francesca,Annunziata, Rita,Puglisi, Alessandra
, p. 1490 - 1499 (2015)
9-Amino-9-deoxy-epi-quinine, properly modified by suitable linkers, was anchored on highly cross-linked polystyrene, poly(ethylene glycol), and silica. The resulting species were characterized by NMR spectroscopy and tested as supported organocatalysts in the reaction between isobutyric aldehyde and trans-β-nitrostyrene. Polystyrene- and poly(ethylene glycol)-supported catalysts outperformed their nonsupported counterpart affording the desired product in high yield and ee (>90 % ee). Silica-supported catalysts proved to be less efficient in terms of both chemical yield and enantioselectivity. Polystyrene- and poly(ethylene glycol)-supported 9-amino-9-deoxy-epi-quinine were then used in the same reaction with different substrates, leading to the desired products in high yield and ee, as well as in three other reactions operating with different mechanism. An investigation of the recyclability of the polystyrene- and poly(ethylene glycol)-supported systems showed that these could be recovered and recycled with no loss of stereochemical activity but with a marked erosion of chemical efficiency occurring at the fifth reaction cycle. This was ascribed to chemical degradation of the alkaloid occurring during the reaction.
Chiral Pyrrolidine Bridged Polyhedral Oligomeric Silsesquioxanes as Heterogeneous Catalysts for Asymmetric Michael Additions
Luanphaisarnnont, Torsak,Hanprasit, Sasikarn,Somjit, Vetiga,Ervithayasuporn, Vuthichai
, p. 779 - 786 (2018)
Abstract: A chiral pyrrolidine bridged polyhedral oligomeric silsesquioxane (SQ) was synthesized, characterized, and used as an effective heterogeneous catalyst. The synthesis involves two simple steps: nucleophilic substitution between benzylchloride fun
Catalytic asymmetric synthesis of chiral covalent organic frameworks from prochiral monomers for heterogeneous asymmetric catalysis
Dong, Yu-Bin,Wang, Jian-Cheng,Kan, Xuan,Shang, Jin-Yan,Qiao, Hua
, p. 16915 - 16920 (2020)
Direct synthesis, postsynthetic modification, and chiral induction have been recognized as three powerful methods to synthesize chiral covalent organic frameworks (CCOFs). However, catalytic asymmetric methodology, as the most important and effective synt
Remarkable enhancement of nucleophilicity of tin enolates toward nitro-or cyanoalkenes by tetrabutylammonium halides
Yasuda, Makoto,Ohigashi, Noriyuki,Baba, Akio
, p. 1266 - 1267 (2000)
The reaction of tin enolates with nitroalkenes was effectively catalyzed by tetrabutylammonium bromide (Bu4NBr) to give γ-nitroketones. When the substituted tin enolates at the β-carbon in the olefinic moiety were used, the diastereoselective a
An effective bifunctional thiourea catalyst for highly enantio- and diastereoselective Michael addition of cyclohexanone to nitroolefins
Cao, Yi-Ju,Lu, Hai-Hua,Lai, Yuan-Yuan,Lu, Liang-Qiu,Xiao, Wen-Jing
, p. 3795 - 3800 (2006)
A series of new tunable and bifunctional thiourea catalysts have been synthesized and their catalytic activities are evaluated in the direct Michael addition of cyclohexanone to nitroolefins. High isolated yields (up to 97%), enantioselectivities (up to 9
Prolinol tert-butyldiphenylsilyl ether as organocatalyst for the asymmetric michael addition of cyclohexanone to nitroolefins
Liu, Fengying,Wang, Shiwen,Wang, Ning,Peng, Yungui
, p. 2415 - 2419 (2007)
The direct Michael additions of cyclohexanone to nitroolefins catalyzed by prolinol tert-butyldiphenylsilyl ether were conducted successfully in good yields (up to 99%) and high stereo-selectivities (up to 98:2 diastereomeric ratio and 95% enantiomeric ex
The carbamate esters as organocatalysts in asymmetric Michael addition reactions in aqueous media: When pyrrolidine backbone surpasses 1,2- diaminocyclohexane
Mondal, Anirban,Bhowmick, Kartick C.
, p. 320 - 331 (2018)
A pyrrolidine ring containing carbamate ester, pyrrolidine-2-ylmethyl-carbamic acid isobutyl ester has been synthesized. The newly developed pyrrolidine ring containing carbamate ester surpassed 1,2- diaminocyclohexane derived carbamate ester in asymmetri