Despite advances in methods for the decarbonylation of aldehydes, the decarbonylation of ketones has been met with limited success because this process requires the activation of two inert carbon-carbon bonds. All of the decarbonylation reactions of simple unstrained ketones reported to date require the addition of a stoichiometric rhodium complex. We report herein the nickel/N-heterocyclic carbene-mediated decarbonylation of simple diaryl ketones. This reaction shows unique acceleration effects based on the presence of both electron-donating and electron-withdrawing groups.
Herein,
we describe a new catalytic approach to accessing aromatic
amines from an abundant feedstock, namely phenols. The most reliable
catalytic method for converting phenols to aromatic amines uses an
activating group, such as a trifluoromethane sulfonyl group. However,
this activating group is eliminated as a leaving group during the
amination process, resulting in significant waste. Our nickel-catalyzed
decarboxylation reaction of aryl carbamates forms aromatic amines
with carbon dioxide as the only byproduct. As this amination proceeds
in the absence of free amines, a range of functionalities, including
a formyl group, are compatible. A bisphosphine ligand immobilized
on a polystyrene support (PS-DPPBz) is key to the success of this
reaction, generating a catalytic species that is significantly more
active than simple nonsupported variants.
Nickel-catalyzed cross-coupling of methoxyarenes with trimethylaluminum is described. The use of 1,3-dicyclohexylimidazol-2-ylidene as a ligand and NaOtBu as a base promotes the methylation of anisole derivatives via the cleavage of normally unreactive aryl carbon–oxygen bonds.
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