scholarly journals Bioinspired Polymer-Bound Organocatalysts for Direct Asymmetric Aldol Reaction: Experimental and Computational Studies

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 398
Author(s):  
Ganhong Du ◽  
Jun Ling ◽  
Fangyu Hu ◽  
Keyuan Liu ◽  
Long Ye ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Aldol Reaction ◽  
Catalytic Efficiency ◽  
Aromatic Aldehydes ◽  
Relative Energy ◽  
Catalyst Loading ◽  
Polymer Backbone ◽  
Asymmetric Aldol ◽  
Tertiary Amide ◽  
Asymmetric Aldol Reaction

A series of poly(2-oxazoline) (POX) derivatives bearing prolinamide pendants were designed as organocatalysts and evaluated in the direct asymmetric aldol reaction between aromatic aldehydes and cyclic ketones. The structural variation of the alkyl spacer connecting the polymer backbone with the catalytic unit was applied so as to deduce structure–performance relationships combined with comparable experiments from model catalysts. Results showed that the POX-bound prolinamides can promote the aldol reaction more effectively as compared to their small-molecular and non-POX-bound analogs. The catalyst P3 containing the pyrrolidine moiety closer to the tertiary amide backbone exhibited the overall best catalytic efficiency, affording anti-products in 84% yield with 89% ee in the representative aldol addition of cyclohexanone to 4-nitrobenzaldehyde at a 10 mol.% catalyst loading. Furthermore, the influence of trifluoroacetic acid as an additive on the asymmetric transformation was investigated. Theoretical calculations revealed that the protonation of the aldehyde carbonyl group switched the activation mode of the aldol acceptor through hydrogen bond interactions, thereby changing the relative energy barrier of the enamine/aldehyde reaction transition states, which accounted well for the significant improvement in the enantioselectivity of the acidic additives observed experimentally.

scholarly journals Chiral Thiazolidine based Organocatalysts: Synthesis and Application in Asymmetric Aldol Reactions

2020 ◽  
Vol 17 (5) ◽  
pp. 372-380
Author(s):  
Ana Rita G. Félix ◽  
Pedro R.D. Simões ◽  
Francisco J.P.M. Sousa ◽  
M. Elisa Silva Serra ◽  
Dina Murtinho
Keyword(s):  
Reaction Time ◽  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Aldol Reactions ◽  
Catalyst Loading ◽  
Reaction Parameters ◽  
Asymmetric Aldol ◽  
Asymmetric Aldol Reaction

Several novel chiral organocatalysts derived from thiazolidines containing amide and thioureia functionalities were synthesized in good yields. These organocatalysts were tested in the asymmetric aldol reaction of acetone with p-nitrobenzaldehyde. Reaction parameters such as reaction time, catalyst loading and solvent were optimized. Products with conversions up to 84% and enantiomeric ratios (er) up to 84.5:15.5 (R:S) were obtained. The effect of several chiral and non-chiral additives on the reactivity and selectivity of the reaction was also evaluated. The reaction was extended to other aromatic aldehydes with the best organocatalyst and when p-bromobenzaldehyde was used, an er of 94.5:5.5 (R:S) was obtained.

(S,S,S)-Perhydroindolic Acid: Efficient Catalyst for Direct Asymmetric Aldol Reaction from Aromatic Aldehydes.

ChemInform ◽  
2007 ◽  
Vol 38 (3) ◽  
Author(s):  
Xiaoping Tang ◽  
Benoit Liegault ◽  
Jean-Luc Renaud ◽  
Christian Bruneau
Keyword(s):  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Efficient Catalyst ◽  
Asymmetric Aldol ◽  
Asymmetric Aldol Reaction

scholarly journals Synthesis of New Di- and Triamides as Potential Organocatalysts for Asymmetric Aldol Reaction in Water

2020 ◽  
Vol 67 (4) ◽  
pp. 1014-1023
Author(s):  
Elif Keskin ◽  
Cigdem Yolacan ◽  
Feray Aydogan
Keyword(s):  
Benzoic Acid ◽  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Reaction Conditions ◽  
Asymmetric Aldol ◽  
Co Catalyst ◽  
Aliphatic Ketones ◽  
Asymmetric Aldol Reaction ◽  
Reaction In Water

New di- or triamide organocatalysts derived from (L)-proline were synthesized and successfully used in the direct asymmetric aldol reaction of aliphatic ketones and aromatic aldehydes in water at 0 °C in the presence of benzoic acid as co-catalyst. (S)-methyl-2-((S)-3-hydroxy-2-((S)-3-pyrrolidine-2-carboxamido)propanamido)-3-phenylpropanoate (7c) as organocatalyst showed best results under these reaction conditions, and good diastereoselectivities (up to 99%), enantioselectivities (up to 98%) and yields (up to 91%) were observed.

Pro-Phe derivatives as organocatalysts in asymmetric aldol reaction

2020 ◽  
Vol 17 ◽  
Author(s):  
Merve Karaoglu ◽  
Feray Aydogan ◽  
Cigdem Yolacan
Keyword(s):  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Biologically Active ◽  
Asymmetric Aldol ◽  
Catalytic Activities ◽  
Bond Forming ◽  
Nitrobenzoic Acid ◽  
Aliphatic Ketones ◽  
Asymmetric Aldol Reaction ◽  
Optically Pure

: The aldol reaction which is the most important one among the C-C bond forming reactions, is widely used by synthetic organic chemists to obtain β-hydroxycarbonyl compounds which are important starting components for biologically active compounds in optically pure form. In this research, five Pro-Phe derivatives were synthesized by simple amidation reactions and characterized by their spectral data. Their catalytic activities in asymmetric aldol reaction were investigated. The catalytic activity studies were performed with aliphatic ketones and various aromatic aldehydes. Especially, (S)-methyl 3-mercapto-2-((S)-3-phenyl-2-((S)-pyrrolidine-2-carboxamido)propanamido)propanoate showed good catalytic activities in water at 0 oC in the presence of p-nitrobenzoic acid cocatalyst. The enantioselectivities were upto 90.4%, the diastereomeric ratios were upto 97/3 and yields were 99%. The results showed that these organocatalysts were promising organocatalysts for aldol reaction. Besides, this catalyst showed its best catalytic activities in water which is also important contribution to green chemistry requirements.

scholarly journals Enantiodivergent Aldol Condensation in the Presence of Aziridine/Acid/Water Systems

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 930 ◽  
Author(s):  
Adam Marek Pieczonka ◽  
Lena Marciniak ◽  
Michał Rachwalski ◽  
Stanisław Leśniak
Keyword(s):  
Aldol Condensation ◽  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Water Systems ◽  
Acid Water ◽  
Asymmetric Aldol ◽  
Asymmetric Aldol Reaction ◽  
Chiral Imines ◽  
Very High

A series of novel chiral imines was synthesized from corresponding aldehydes and 1-(2-aminoalkyl)aziridines with good chemical yields. Such imines were tested as catalysts in the direct asymmetric aldol reaction between aromatic aldehydes and acetone/cyclohexanone in the presence of catalytic amounts of water and an acidic additive. The corresponding aldol products were formed in excellent yields and with very high enantioselectivities (98% and 99% ee, respectively).

The smallest organocatalyst in highly enantioselective direct aldol reaction in wet solvent-free conditions

RSC Advances ◽  
2014 ◽  
Vol 4 (46) ◽  
pp. 24311-24315 ◽  
Author(s):  
Sudipto Bhowmick ◽  
Sunita S. Kunte ◽  
Kartick C. Bhowmick
Keyword(s):  
Amino Acid ◽  
Room Temperature ◽  
Aldol Reaction ◽  
Aromatic Aldehydes ◽  
Solvent Free ◽  
Natural Amino Acid ◽  
Asymmetric Aldol ◽  
Direct Aldol Reaction ◽  
Solvent Free Conditions ◽  
Asymmetric Aldol Reaction

The catalytic efficacy of the smallest organocatalyst, l-proline hydrazide, prepared from a cheaply available natural amino acid, such as l-proline, was studied for the direct asymmetric aldol reaction of various ketones with aromatic aldehydes at room temperature in the presence of several acid additives.

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