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Search Results (3)

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Keywords = dienamine

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33 pages, 6716 KiB  
Review
Asymmetric Dual Enamine Catalysis/Hydrogen Bonding Activation
by Efraím Reyes, Liher Prieto, Uxue Uria, Luisa Carrillo and Jose L. Vicario
Catalysts 2023, 13(7), 1091; https://doi.org/10.3390/catal13071091 - 11 Jul 2023
Cited by 2 | Viewed by 3185
Abstract
Asymmetric enamine base activation of carbonyl compounds is a well-known and widely used strategy for providing functionalization of organic compounds in an efficient way. The use of solely organic substances, which in most cases are commercially available primary or secondary amines that are [...] Read more.
Asymmetric enamine base activation of carbonyl compounds is a well-known and widely used strategy for providing functionalization of organic compounds in an efficient way. The use of solely organic substances, which in most cases are commercially available primary or secondary amines that are easy to obtain, avoids the use of hazardous substances or metal traces, making this type of catalysis a highly convenient methodology from a sustainable point of view. In many cases, the reactivity or the stereoselectivity obtained is far from being a practical and advantageous strategy; this can be improved by using a hydrogen bonding co-catalyst that can help during the activation of one species or by using a bifunctional catalyst that can direct the approximation of reagents during the reaction outcome. In this review, we describe the most efficient methodologies that make use of a dual activation of reagents for performing α-functionalization (enamine activation) or remote functionalization (such as dienamine or trienamine activation) of carbonyl compounds. Full article
(This article belongs to the Special Issue New Trends in Asymmetric Catalysis: Green and Sustainable Catalysts)
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8 pages, 2709 KiB  
Article
Effects of Water Addition on a Catalytic Fluorination of Dienamine
by Daiki Kuraoku, Tsunaki Yonamine, Genta Koja, Norio Yoshida, Satoru Arimitsu and Masahiro Higashi
Molecules 2019, 24(19), 3428; https://doi.org/10.3390/molecules24193428 - 21 Sep 2019
Cited by 6 | Viewed by 3027
Abstract
We investigate the effects of water addition on a highly stereocontrolled fluorination of dienamine generated by α-branched enals and 6′-hydroxy-9-amino-9-deoxy-epi-quinidine with N-fluorobenzenesulfonimide (NFSI) in the presence of Brønsted acid both experimentally and theoretically. It is experimentally found that water addition [...] Read more.
We investigate the effects of water addition on a highly stereocontrolled fluorination of dienamine generated by α-branched enals and 6′-hydroxy-9-amino-9-deoxy-epi-quinidine with N-fluorobenzenesulfonimide (NFSI) in the presence of Brønsted acid both experimentally and theoretically. It is experimentally found that water addition to organic solvent significantly shortens the reaction time whereas excessive water addition decreases the enantiomeric excess. The results calculated with three-dimensional reference interaction site model self-consistent field (3D-RISM-SCF) method are in good agreement with the experimental ones. It is revealed that the shortness of reaction time is caused by the reactant destabilization and that the decrease in enantiomeric excess is due to the difference of hydration free energy between two transition states. Full article
(This article belongs to the Special Issue Fabulous Fluorine in Organic and Medicinal Chemistry)
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26 pages, 797 KiB  
Review
Enantioselective, Organocatalytic Morita-Baylis-Hillman and Aza-Morita-Baylis-Hillman Reactions: Stereochemical Issues
by Javier Mansilla and José M. Saá
Molecules 2010, 15(2), 709-734; https://doi.org/10.3390/molecules15020709 - 1 Feb 2010
Cited by 94 | Viewed by 14775
Abstract
Conscious of the importance that stereochemical issues may have on the design of efficient organocatalyts for both Morita-Baylis-Hillman and aza-Morita-Baylis-Hillman reaction we have analyzed them in this minireview. The so-called standard reactions involve “naked” enolates which therefore should lead to the syn adducts [...] Read more.
Conscious of the importance that stereochemical issues may have on the design of efficient organocatalyts for both Morita-Baylis-Hillman and aza-Morita-Baylis-Hillman reaction we have analyzed them in this minireview. The so-called standard reactions involve “naked” enolates which therefore should lead to the syn adducts as the major products, irrespective of the E, Z stereochemistry of the enolate. Accordingly, provided the second step is rate determining step, the design of successful bifunctional or polyfunctional catalysts has to consider the geometrical requirements imposed by the transition structures of the second step of these reactions. On the other hand, MBH and aza-MBH reactions co-catalyzed by (S)-proline and a secondary or tertiary amine (co-catalyst) involve the aldol-type condensation of either a 3-amino-substituted enamine, dienamine, or both, depending on the cases. A Zimmerman-Traxler mechanism defines the stereochemical issues regarding these co-catalyzed condensations which parallel those of the well established (S)-proline catalyzed aldol-like reactions. Full article
(This article belongs to the Special Issue Baylis-Hillman Reaction and Related Processes)
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