Peptidomimetic organocatalysts: efficient Michael addition of ketones onto nitroolefins with very low catalyst loading

Chandrasekhar, Srivari; Kumar, Chintakunta Praveen; Kumar, Togapur Pavan; Haribabu, Kothapalli; Jagadeesh, B.; Lakshmi, Jerripothula K.; Mainkar, Prathama S.

doi:10.1039/c4ra04165h

Cited by 25 publications

(12 citation statements)

References 95 publications

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“…70 A significantly lower catalyst loading (0.05 mol%) was reported by Mainkar for the model reaction between cyclohexanone and nitrostyrene ( Table 1 reaction 8b). 71 Using organocatalyst 26 with a peptide bond surrogate triazole connecting a pyrrolidine group to an amino amide, they achieved a moderate yield (70%) whereas enantioselectivities were excellent. 71…”

Section: Enamine Catalysismentioning

confidence: 99%

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Organocatalysis in aqueous media

2019

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Section: Enamine Catalysismentioning

confidence: 99%

“…71 Using organocatalyst 26 with a peptide bond surrogate triazole connecting a pyrrolidine group to an amino amide, they achieved a moderate yield (70%) whereas enantioselectivities were excellent. 71…”

Section: Enamine Catalysismentioning

confidence: 99%

Organocatalysis in aqueous media

2019

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“…Especially, the asymmetric Michael addition is very widely used and viable strategy for the carbon–carbon (C–C) bond formation . Organo‐catalyzed asymmetric Michael addition reactions have been developed recently and attracted significant attention in the area of asymmetric synthesis because of their prospective applications . This reaction represents one of the most efficient pathways for the C–C bond formation in synthetic organic chemistry.…”

Section: Methodsmentioning

confidence: 99%

“…The transition state TS A was found to have the lowest energy barrier, even in the absence of an acid additive. The earlier theoretical reports are in favor of TS A with other organic catalysts, supporting the reliability of the present simulation results . Figure S1 of the Supporting information compares the activation energies of the four transition states.…”

Section: Methodsmentioning

confidence: 99%

Chiral Pyrrolidine‐Pyrazole Catalyzed Enantioselective Michael Addition: a Mechanistic Study by Computational Methods

Chitumalla

Togapur

Jang

2016

Bulletin Korean Chem Soc

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Asymmetric synthesis to provide enantiomerically pure compounds is a promising research area in the field of organic chemistry. Especially, the asymmetric Michael addition is very widely used and viable strategy for the carbon-carbon (C-C) bond formation. 1,2 Organo-catalyzed asymmetric Michael addition reactions have been developed recently and attracted significant attention in the area of asymmetric synthesis because of their prospective applications. 3 This reaction represents one of the most efficient pathways for the C-C bond formation in synthetic organic chemistry. Many proline derivatives, such as proline-triazole, 4 pyrrolidinepyridine, 5 pyrrolidine-sulfonamide, 6 and pyrrolidine-pyrazole 7 have been employed as efficient organocatalysts for asymmetric Michael addition. These organic catalysts are applied not only to the Michael addition reactions, but also to the other reactions, such as Aldol reactions, and Domino process. A large number of cyclic ketones and nitroolefins as Michael donors and Michael acceptors, respectively were used in this process, which proceeds with very good enantioselectivity and diastereoselectivity. 7 In the present computational mechanistic study, cyclohexanone (1) and trans-β-nitrostyrene (2) were chosen as Michael donor and Michael acceptor, respectively. Achiral (S)-pyrrolidine-pyrazole (3) catalyst, which has shown excellent catalytic cycle in the Michael addition of carbonyl compounds to various nitroolefins with very good enantio-and diastereoselectivities (up to 99% ee), was chosen as the organic catalyst. The reaction between cyclohexanone (1) and transβ-nitrostyrene (2) yielded the Michael adduct (4) (Scheme 1).Four possible transition geometries related to the C-C bond forming step of the reaction (vide supra) were investigated by employing the density functional theory (DFT), both in the presence and absence of an acid additive. Insights on the diastereo-and enantio-selectivities in the formation of Michael adduct were gained by the transition state analysis. This reaction proceeds through a mechanism involving the initial formation of an enamine between the cyclohexanone and pyrrolidine-pyrazole catalyst with the simultaneous loss of one water molecule. As the enamine formation and the hydrolysis of the Michael adduct (Figure 1) are rapid and have no effect on the rate and stereoselectivity of the reaction, 8 this study focused on the transition states involved in the rate-limiting C-C bond formation step, the nucleophilic attack of the enamine on trans-β-nitrostyrene. Figure 1 presents the mechanism of this reaction from the earlier reports 7 .The two transition states arising from the approach of trans-β-nitrostyrene to the diastereotopical Re and Si faces of the anti-enamine are represented as TS A , and TS B , respectively. Similarly, the other two transition states are formed with syn-enamine and represented as TS C , and TS D . The formation of four transition states and corresponding products are shown in the Scheme 2.The structures of the transition stat...

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“…The introduction of a heterocyclic linkage between the pyrrolidine ring and the unit bearing an additional stereogenic center has been tested to study if the new rigid backbone conformation provided by the heterocycle would enhance the stereoselectivity ( Figure 11 ). Thus, catalyst 56 [ 84 ], 57a , b [ 85 ] have been used in the reaction between ketones and aryl nitroolefins under different reaction conditions, providing adducts of type 46 in good results. Lower yields and enantioselectivities were found when acetone was used as pro-nucleophile.…”

Section: Carbon Nucleophilesmentioning

confidence: 99%

Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

et al. 2017

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The asymmetric conjugate addition of carbon and heteroatom nucleophiles to nitroalkenes is a very interesting tool for the construction of highly functionalized synthetic building blocks. Thanks to the rapid development of asymmetric organocatalysis, significant progress has been made during the last years in achieving efficiently this process, concerning chiral organocatalysts, substrates and reaction conditions. This review surveys the advances in asymmetric organocatalytic conjugate addition reactions to α,β-unsaturated nitroalkenes developed between 2013 and early 2017.

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Peptidomimetic organocatalysts: efficient Michael addition of ketones onto nitroolefins with very low catalyst loading

Abstract: KUMAR, C. P.; KUMAR, T. P.; HARIBABU, K.; JAGADEESH, B.; LAKSHMI, J. K.; MAINKAR, P. S.; RSC Adv. 4 (2014) 57, 30325-30331, http://dx.doi.org/10.1039/C4RA04165H ; Div. Nat. Prod. Chem., Indian Inst. Chem. Technol., Hyderabad 500 007, India; Eng.) -L. Grundl 07-085

Cited by 25 publications

References 95 publications

Organocatalysis in aqueous media

Organocatalysis in aqueous media

Chiral Pyrrolidine‐Pyrazole Catalyzed Enantioselective Michael Addition: a Mechanistic Study by Computational Methods

Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

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