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Enantioconvergent Negishi Cross-Couplings of Racemic Secondary Organozinc Reagents to Access Privileged Scaffolds: A Combined Experimental and Theoretical Study.
Angew Chem Int Ed Engl
December 2024
Institute of Organic Chemistry, University of Vienna, Währinger Str. 38, 1090, Vienna, Austria.
An enantioconvergent palladium-catalyzed Negishi cross-coupling with racemic secondary organozinc reagents has been developed, enabling access to enantioenriched 1,1-diarylalkane motifs in high yields and enantioselectivities. Computational data indicates that the racemization of organozinc compounds most likely occurs through a bridged bimolecular mechanism.
View Article and Find Full Text PDFCalculation-assisted regioselective functionalization of the imidazo[1,2-]pyrazine scaffold zinc and magnesium organometallic intermediates.
Chem Sci
October 2023
Department Chemie, Ludwig-Maximilians-Universität München Butenandtstrasse 5-13, Haus F 81377 München Germany
Straightforward calculations such as determinations of p values and N-basicities have allowed the development of a set of organometallic reactions for the regioselective functionalization of the underexplored fused N-heterocycle imidazo[1,2-]pyrazine. Thus, regioselective metalations of 6-chloroimidazo[1,2-]pyrazine using TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl) such as TMPMgCl·LiCl and TMPZn·2MgCl·2LiCl provided Zn- and Mg-intermediates, that after quenching with various electrophiles gave access to polyfunctionalized imidazopyrazine heterocycles. Additionally, the use of TMPZn·2MgCl·2LiCl as base for the first metalation allowed an alternative regioselective metalation.
View Article and Find Full Text PDFAtroposelective Ni -Catalyzed Cross-Coupling Reactions Enable a Deeper Understanding of Negishi Couplings: Isolation and Application of Solid Aryl Higher-Order Zincates.
Chemistry
December 2023
Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, Haus F, 81377, München, Germany.
The Negishi cross-coupling reactions involves the application of organozinc reagents and is a highly versatile reaction in synthetic organic chemistry. The transmetallation step plays a pivotal role in the mechanism of these types of cross-coupling reactions. In this study, mechanistic investigations are presented indicating that higher-order zincates are the transmetallating active species in Pd- and Ni-catalyzed Negishi cross-coupling reactions.
View Article and Find Full Text PDFSalt-stabilized alkylzinc pivalates: versatile reagents for cobalt-catalyzed selective 1,2-dialkylation.
Chem Sci
August 2023
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University Suzhou 215123 China
The construction of Csp-Csp bonds through Negishi-type reactions using alkylzinc reagents as the pronucleophiles is of great importance for the synthesis of pharmaceuticals and agrochemicals. However, the use of air and moisture sensitive solutions of conventional alkylzinc halides, which show unsatisfying reactivity and limitation of generality in twofold Csp-Csp cross-couplings, still represents drawbacks. We herein report the first preparation of solid and salt-stabilized alkylzinc pivalates by OPiv-coordination, which exhibit enhanced stability and a distinct advantage of reacting well in cobalt-catalyzed difluoroalkylation-alkylation of dienoates, thus achieving the modular and site-selective installation of CF- and Csp-groups across double bonds in a stereoretentive manifold.
View Article and Find Full Text PDFSimplified Preparation of ppm Pd-Containing Nanoparticles as Catalysts for Chemistry in Water.
ACS Catal
March 2023
Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106, United States.
A protocol has been developed that not only simplifies the preparation of nanoparticles (NPs) containing ppm levels of ligated palladium that affect heterogeneous catalysis but also ensures that they afford products of cross-couplings reproducibly due to the freshly prepared nature of each reagent. Four different types of couplings are studied: Suzuki-Miyaura, Sonogashira, Mizoroki-Heck, and Negishi reactions, all performed under mild aqueous micellar conditions. The simplified process relies on the initial formation of stable, storable Pd- and ligand-free NPs, to which is then added the appropriate amount of Pd(OAc) and ligand-matched to the desired type of coupling, in water.
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