This minireview provides a survey of the various synthetic approaches to chiral ansa-metallocenes of Ti, Zr, and Hf containing a carbon-based bridge. The individual strategies to install substitution patterns at either the cyclopentadienyl framework or the bridging unit are highlighted with focus on the progress made towards a direct preparation of single complex stereoisomers. The review further includes the discussion of potential problems such as the formation of undesired diastereomers, the threat of racemization of enantiopure material, and synthetic challenges originating from the synthesis, purification, and isolation of the target complexes. The review has been written with the goal in mind to facilitate the design and synthesis of new chiral ansa-metallocene derivatives for emerging research areas in asymmetric catalysis and organometallic chemistry.
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http://dx.doi.org/10.1002/chem.201901505 | DOI Listing |
J Am Chem Soc
January 2025
Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, United States.
The development of catalytic methods for the synthesis of enantiopure saturated heterocycles has been a long-standing challenge in asymmetric catalysis. We describe the first highly enantioselective palladium-catalyzed βC(sp)-H arylation and olefination of lactams for the preparation of various chiral N-heterocycles bearing quaternary carbon centers. The presence of strongly electron-withdrawing groups on the chiral bifunctional MPAThio ligand is crucial to the reactivity of weakly coordinating lactams.
View Article and Find Full Text PDFJ 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 PDFMini Rev Med Chem
January 2025
Department of Physiology and Pharmacology Vittorio Erspamer, Sapienza University of Rome, 00161, Rome, Italy.
Currently, the synthesis of bioactive sulfonamides using amino acid as a starting reagent has become an area of research interest in organic chemistry. Over the years, an amine-sulfonyl chloride reaction has been adopted as a common step in traditional sulfonamide synthetic methods. However, recent developments have shown amino acids to be better precursors than amines in the synthesis of sulfonamides.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
A concise and convergent synthesis of the isosteroidal alkaloids veratramine and 20--veratramine has been accomplished. A Horner-Wadsworth-Emmons olefination joins two chiral building blocks of approximately equal complexity and a transition-metal catalyzed intramolecular Diels-Alder cycloaddition-aromatization cascade constructs the tetrasubstituted arene. Other key steps include a highly diastereoselective crotylation of an -sulfonyl iminium ion and an Eschenmoser fragmentation.
View Article and Find Full Text PDFBeilstein J Org Chem
January 2025
Department of Organic Chemistry, Faculty of Natural Science, Comenius University Bratislava, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia.
Axial chirality is present in a variety of naturally occurring compounds, and is becoming increasingly relevant also in medicine. Many axially chiral compounds are important as catalysts in asymmetric catalysis or have chiroptical properties. This review overviews recent progress in the synthesis of axially chiral compounds via asymmetric organocatalysis.
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