Transition metal-catalyzed carbonylation with carbon nucleophiles is one of the most prominent methods to construct ketones, which are highly versatile motifs prevalent in a variety of organic compounds. In comparison to the well-established palladium catalytic system, the nickel-catalyzed carbonylative coupling is much underdeveloped due to the strong binding affinity of CO to nickel. By leveraging easily accessible tert-butyl isocyanide as the CO surrogate, we present a nickel-catalyzed allylic carbonylative coupling with alkyl zinc reagent, allowing for the practical and straightforward preparation of synthetically important β,γunsaturated ketones in a linear-selective fashion with excellent trans-selectivity under mild conditions. Moreover, the undesired polycarbonylation process which is often encountered in palladium chemistry could be completely suppressed. This nickel-based method features excellent functional group tolerance, even including the active aryl iodide functionality to allow the orthogonal derivatization of β,γ-unsaturated ketones. Preliminary mechanistic studies suggest that the reaction proceeds via a π-allylnickel intermediate.
We report herein
a miscellaneous oxindole synthesis bearing an
all-carbon quaternary center, enabled by Pd-catalyzed intramolecular
cyclization followed by multiple intermolecular Heck reactions of
both easily accessible alkene-tethered carbamoyl chlorides and olefins.
This protocol obviates the use of prefunctionalized olefinic reagents,
exhibits excellent functional group tolerance, and features fascinating
reactive versatility.
Chiral ligands play an essential role in transition metal-catalyzed enantioselective transformations, in which chiral oxazoline-based scaffolds are the privileged chiral ligand. Nevertheless, 8-quinolinyl oxazoline (8-Quinox) ligands are underexplored in transition metal-catalyzed asymmetric transformations since their development in 1998. Herein, we report an 8-Quinox ligand promoted Ni-catalyzed enantioselective reductive carbamoyl-alkylation of carbamoyl chloride tethered styrene with unactivated alkyl iodide, providing an expedient access to valuable enantioenriched oxindoles in good results.
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