Gao K, Yoshikai N * Nanyang Technology University, Singapore, Singapore
Cobalt-Catalyzed Ortho Alkylation of Aromatic Imines with Primary and Secondary Alkyl Halides.
J. Am. Chem. Soc. 2013;
135: 9279-9282
Key words
cobalt - alkylation - Grignard reagents
Significance
A novel method for the direct ortho-alkylation of aromatic imines has been disclosed. 10 mol% of cobalt(II) bromide (CoBr2) in combination with an N-heterocyclic carbene (NHC) ligand catalyzes the reaction of an alkyl halide with the aromatic imine to deliver the corresponding ortho-alkylated ketones after acidic work-up.
Comment
The activation of the alkyl halide is proposed to occur through single-electron transfer from a cobalt species to generate an alkyl radical. Recombination of the cobalt and the radical centers may cause the C–C bond formation.
