Patil RD, Pratihar S. Ruthenium(II)-Catalyzed Hydrogenation and Tandem (De)Hydrogenation
via Metal-Ligand Cooperation: Base- and Solvent-Assisted Switchable Selectivity.
J Org Chem 2024;
89:1361-1378. [PMID:
36283058 DOI:
10.1021/acs.joc.2c01965]
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Abstract
A versatile, selective, solvent (methanol vs ethanol)- and base (potassium vs lithium carbonate)-assisted switchable synthesis of saturated ketone and α-methyl saturated ketone from α,β-unsaturated ketone is developed. Mechanistic aspects, evaluated from spectroscopic studies, in situ monitoring of the reaction progress, control studies, and labeling studies, further indicate the involvement of a tandem dehydrogenation-condensation-hydrogenation sequence in the reaction, in which the interconvertible coordination mode (imino N → Ru and amido N-Ru) of coordinated imidazole with Ru(II)-para-cymene is crucial, without which the efficiency and selectivity of the catalyst are completely lost. The catalyst demonstrates good efficiency, selectivity, and functional group tolerance and displays a broad scope (69 examples) for monomethylation and hydrogenation of unsaturated chalcones, double methylation of ketones, and N-methylation of amines.
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