A practical and improved synthetic route for the scalable synthesis of homohalichondrin B has been developed. Formation of the highly stereoselective [6,6]-spiroskeleton system through a convergent Ni/Zr-mediated ketone coupling, followed by acid-promoted spiroketalization, simplified the route considerably. Higher coupling efficiency was achieved by fine-tuning the Ni/Ni (1:50) catalyst loadings with an equimolar (1:1) mixture of coupling partners.
View Article and Find Full Text PDFThe Suzuki-Miyaura and Buchwald-Hartwig coupling reactions are widely used to form carbon-carbon (C-C) and carbon-nitrogen (C-N) bonds, respectively. We report the incorporation of a formal nitrene insertion process into the Suzuki-Miyaura reaction, altering the products from C-C-linked biaryls to C-N-C-linked diaryl amines and thereby joining the Suzuki-Miyaura and Buchwald-Hartwig coupling pathways to the same starting-material classes. A combination of a bulky ancillary phosphine ligand on palladium and a commercially available amination reagent enables efficient reactivity across aryl halides and pseudohalides, boronic acids and esters, and many functional groups and heterocycles.
View Article and Find Full Text PDFA direct synthesis of ketones by the nickel-catalyzed deaminative cross-coupling of alkylpyridinium salts with thiopyridine esters has been reported. The reaction works well for both primary and secondary amines. This approach affords a highly valuable vista for the facile synthesis of ketones from easily accessible feedstock chemicals.
View Article and Find Full Text PDFOrg Biomol Chem
November 2021
A short and enantioselective synthesis of the 19--BE-43547 A chiral framework has been achieved in a high yield. The challenging key C15 tertiary stereocenter was derived from D-glucose. The synthetic strategy involves a Julia-Kocienski olefination to install the lipophilic side chain.
View Article and Find Full Text PDFA novel insertion reaction of N-tosylacetimidates and N-tosylacetimidamides onto arynes via a benzocyclobutene intermediate followed by ring cleavage is developed to afford o-benzylbenzoic acid derivatives in good yields. Interestingly, the use of cyclic 2-sulfonyliminoindolines provided two distinct products such as azepanimines via [2 + 2] cycloaddition and indolamines via protonation based on solvent medium.
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