156039-16-6Relevant articles and documents
Asymmetric aldol reactions catalyzed by tryptophan in water
Jiang, Zhaoqin,Liang, Zhian,Wu, Xiaoyu,Lu, Yixin
, p. 2801 - 2803 (2006)
Tryptophan was shown to be able to catalyze direct aldol reactions between various cyclic ketones and aromatic aldehydes in water with high enantioselectivity. The Royal Society of Chemistry 2006.
Electrosteric activation by using ion-tagged prolines: A combined experimental and computational investigation
Bottoni, Andrea,Lombardo, Marco,Miscione, Gian Pietro,Montroni, Elisa,Quintavalla, Arianna,Trombini, Claudio
, p. 2913 - 2924 (2013)
We have recently proposed the empirical concept of electrosteric activation to explain the improved catalytic performances observed for a series of ion-tagged catalysts compared to the parent tag-free structures. Here, the results of a combined experimental and computational investigation on the asymmetric aldol reaction between cyclohexanone and benzaldehyde, catalyzed by a family of tag-free and ionic-tagged prolines, are presented. Whereas diastereo- and enantioselectivities remain very high in all cases examined, the ion-tagged catalyst cis-4-(2-(3-methyl-imidazol-3-ium-1-yl)acetoxy)-proline bistriflimide, cis-7, displays a remarkably high activity compared to its tagged trans analogue and to the tag-free catalysts cis and trans-4-(2-phenylacetoxy)-proline 8. A computational investigation of ion-tagged and tag-free model systems shows that the transition state involving cis-7 is stabilized by a complex interplay of hydrogen bonds (in particular, those involving the counter ion oxygen atoms and the hydrogen atoms of the ionic tag), π-stacking interactions involving the aldehyde phenyl ring, and similar π interactions between the proline carboxyl group and the imidazole ring. The overall effect of these interactions accounts for the observed enhanced activity. Stack attack! The asymmetric aldol reaction between cyclohexanone and benzaldehyde in the presence of tagged 4-hydroxy-prolines is modeled to elucidate the empirical concept of electrosteric activation, introduced to account for the much higher activity of cis-ion-tagged prolines. A complex interplay of hydrogen bonds and π-stacking interactions is found to give rise to the observed enhanced activity.
Exploring “Through-Bond” Proximity between the Ion Tag and Reaction Site of an Imidazolium-Proline Catalyst for the Direct Asymmetric Aldol Reaction
Bhati, Meeta,Upadhyay, Shruti,Easwar, Srinivasan
, p. 1788 - 1793 (2017)
The incorporation of an imidazolium moiety at the C-4 position of proline, cis to its COOH group, enabled an interesting study of the effect of through-bond proximity of the ion tag to the reaction site in an enamine-mediated direct asymmetric aldol react
Direct asymmetric aldol reaction co-catalyzed by l-proline and isothiouronium salts
Cho, Eun,Kim, Taek Hyeon
, p. 6470 - 6473 (2014)
An efficient, simple, and highly selective protocol for the direct asymmetric aldol reaction between cyclohexanone and aromatic aldehydes using l-proline as a chiral catalyst is reported. Catalytic amounts of achiral isothiouronium iodide salt 1d have bee
L-proline diamides with an axially chiral binaphthylene backbone as efficient organocatalysts for direct asymmetric aldol reactions: The effect of acetic acid
Ma, Guang-Ning,Zhang, Yun-Peng,Shi, Min
, p. 197 - 208 (2007)
A series of L-proline diamides derived from optically active 1,1′-binaphthyl-2,2′-diamines have been synthesized in good yields and their catalytic abilities as organocatalysts in direct asymmetric aldol reactions have been evaluated. Among these organo-c
Direct catalytic asymmetric aldol reactions on chiral catalysts assembled in the interface of emulsion droplets
Zhong, Lin,Gao, Qiang,Gao, Jinbo,Xiao, Jianliang,Li, Can
, p. 360 - 364 (2007)
An amphiphilic proline-based organocatalyst was assembled on the interface of water and oil, resulting in a W/O emulsion. The chiral catalyst in emulsion significantly enhances the reactivity and stereoselectivity of the direct asymmetric aldol reactions,
Rational design of mimetic peptides based on aldo-ketoreductase enzyme as asymmetric organocatalysts in aldol reactions
Bayat, Saadi,Tejo, Bimo A.,Abdulmalek, Emilia,Salleh, Abu Bakar,Normi, Yahaya M.,Abdul Rahman, Mohd Basyaruddin
, p. 38859 - 38868 (2014)
Peptides as a kind of important chiral scaffold are broadly identified for their obvious advantages, diverse structures and accessibility. Based on promiscuous aldo-keto-reductase enzymes, several mimetic peptides were designed which were synthesized and
Enantioselective Aldol Reactions in Water by a Proline-Derived Cryptand and Fixation of CO2 by Its Exocyclic Co(II) Complex
De, Dinesh,Bhattacharyya, Aditya,Bharadwaj, Parimal K.
, p. 11443 - 11449 (2017)
The secondary amine donors present in the bridges of a laterally nonsymmetric oxa-aza cryptand have been derivatized with l-proline to obtain the chiral cryptand L. The cryptand L efficiently catalyzed aldol reactions in water with up to 75% ee. On reacting with Co(II) perchlorate in the presence of KSCN, L readily formed the trinuclear complex {[Co3(L)2(NCS)6]·(15CH3CN)(5acetone)(6H2O)} (1). The complex 1 in combination with the cocatalyst tetrabutylammonium bromide (TBAB) formed an efficient catalytic system in the synthesis of cyclic carbonates from CO2 and epoxides at room temperature and atmospheric pressure.
trans-4-hydroxy-L-proline hydrazide-trifluoroacetic acid as highly stereoselective organocatalyst for the asymmetric direct aldol reaction of cyclohexanone
Cheng, Chuanling,Wei, Siyu,Sun, Jian
, p. 2419 - 2422 (2006)
Protonated N′-benzyl-N′-L-prolyl-trans-4-hydroxy-L-proline hydrazide has been found to be superior to the L-proline hydrazide counterpart as the catalyst for the asymmetric aldol reaction of cyclohexanone and aromatic aldehydes, resulting in excellent dia
Protonated arginine and lysine as catalysts for the direct asymmetric aldol reaction in ionic liquids
Lombardo, Marco,Easwar, Srinivasan,Pasi, Filippo,Trombini, Claudio,Dhavale, Dilip D.
, p. 9203 - 9207 (2008)
Side chain protonation of basic α-amino acids with Br?nsted acids provides new effective catalysts for the direct asymmetric aldol reaction of cyclic ketones with aromatic aldehydes in ionic liquids and DMSO. Increased yields are obtained in N-butyl N-met
