Application of hydroxyproline derivatives in enantioselective α-amination reactions in organic and aqueous environments: a structure-activity relationship study

Gurka, András A.; Szőri, Kornél; Szőri, Milán; Bartók, Mihály; London, Gábor

doi:10.1007/s11224-016-0873-z

Cited by 3 publications

(1 citation statement)

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“…Another evidence of the universal character of the proposed mechanism and its applicability to all enamine-based asymmetric organocatalytic reactions is the observed inversion of enantioselectivity in the l-hydroxyproline derivative-catalyzed asymmetric α-amination reaction by changing the pH of aqueous solution [7], where the different transition states and therefore the stereochemical outcome of the reaction can be easily explained with the proposed mechanism.…”

Section: Resultsmentioning

confidence: 85%

New Mechanistic Approach in the Enamine-Based Asymmetric Organocatalysis

Gurka

2021

Preprint

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During the course of my research in asymmetric organocatalysis the inversion of enantioselectivity was observed in the asymmetric aldol reactions of acetone with different aldehydes catalyzed by amphiphilic proline derivatives in aqueous media varying only achiral components. It was not possible to explain the explored dual stereocontrol with the existing models, therefore I proposed a new mechanism for asymmetric aldol reactions catalyzed by l-amino acid derivatives in aqueous media and explained the explored phenomenon of inversion of enantioselectivity with different structures of micelle-stabilized transition state described as a metal-free version of the Zimmermann-Traxler model with explicit participation of a water molecule. Contrary to the existing models, according to the proposed mechanism the formation of new bonds proceeds directly in the transition state stabilized by a water molecule without the additional step of product iminium ion hydrolysis. The proposed mechanism has universal character, it is consistent with experimental results and general theoretical conceptions and it is applicable to all enamine-based asymmetric organocatalytic reactions carried out not only in aqueous, but in organic media as well, because the initial step of catalytic cycle, which involves the formation of an enamine from the carbonyl compound and proline (derivative), liberates one water molecule.

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Section: Resultsmentioning

confidence: 85%