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Catalytic Enantioselective Synthesis of 1,4-(Hetero) Dicarbonyl Compounds through α-Carbonyl Umpolung.
J Am Chem Soc
January 2025
Institute of Organic Chemistry, University of Leipzig, 04103 Leipzig, Germany.
The enantioselective synthesis of 1,4-dicarbonyl compounds continues to pose a significant challenge in organic synthesis, and a catalytic process which generates two adjacent stereogenic centers with full stereochemical control is lacking until now. The 1,4-relationship of the functional groups requires an Umpolung strategy as one of the α-carbonyl positions has to be inverted into an electrophilic center to react with a normal enolate. We report herein the highly enantio- and diastereoselective addition of silyl ketene acetals toward electrophilic 1-azaallyl cations to furnish chiral 4-hydrazonoesters, which are masked 1,4-dicarbonyl compounds.
View Article and Find Full Text PDFCatalytic Enantioselective Nucleophilic Amination of α-Halo Carbonyl Compounds with Free Amines.
J Am Chem Soc
January 2025
Department of Chemistry and the Hong Kong Branch of Chinese National Engineering Research Centre for Tissue Restoration & Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China.
Catalytic enantioselective substitution of the readily available racemic α-halo carbonyl compounds by nitrogen nucleophiles represents one of the most convenient and direct approaches to access enantioenriched α-amino carbonyl compounds. Distinct from the two available strategies involving radicals and enolate ions, herein we have developed a new protocol featuring an electronically opposite way to weaken/cleave the carbon-halogen bond. A suitable chiral anion-based catalyst enables effective asymmetric control over the key positively charged intermediates.
View Article and Find Full Text PDFHeteroaryl-Directed Iridium-Catalyzed Enantioselective C-H Alkenylations of Secondary Alcohols.
J Am Chem Soc
January 2025
Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom.
Under iridium-catalyzed conditions, 2-aza-aryl-substituted secondary alcohols undergo C(sp)-H addition reactions to alkynes to provide alkenylated tertiary alcohols. The processes occur with very high regio- and enantioselectivity. An analogous addition to styrene is shown to provide a prototype C(sp)-H alkylation process.
View Article and Find Full Text PDFOrigins of the substituent effects in the aldol condensation of axially chiral thiohydantoins: a computational study.
Org Biomol Chem
December 2024
Department of Chemistry, Bogazici University, Bebek, Istanbul 34342, Turkey.
Aldol reactions are one of the most fundamental organic reactions involving the formation of carbon-carbon bonds that are commonly used in the synthesis of complex molecules through the condensation of an enol or enolate with a carbonyl group. The aldol reaction of thiohydantoin derivatives with benzaldehyde starts with hydrogen removal from C5 by lithium diisopropylamide (LDA) to form the enolate. Benzaldehyde adds to the enolate either at the less or more hindered site.
View Article and Find Full Text PDFCopper(I)-Catalyzed Enantioselective α-Alkylation of 2-Acylimidazoles.
J Am Chem Soc
December 2024
Key Laboratory of Fluorine and Nitrogen Chemistry and Advanced Materials, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
Catalytic asymmetric α-alkylation of simple carboxylic acid derivatives is a challenging issue due to the difficulties in achieving high catalytic efficiency and controlling the enantioselectivity. Herein, by using a copper(I)-()-DTBM-SEGPHOS complex as a catalyst and 2-acylimidazoles as pronucleophiles, a general method for the catalytic asymmetric α-alkylation of simple carboxylic acid derivatives is accomplished. Various alkyl electrophiles, including allyl bromides, benzyl bromides, propargyl bromide, and unactivated alkyl sulfonates, serve as efficient alkylation reagents.
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