Research progress on transition-metal-free C–N bonds cleavage of amides in the synthesis of ketones

Amides compounds have a wide range of application, and many transforming strategies have been reported. Transition metals-catalyzed non-decarbonylative cross-coupling reaction of amides has gained considerable attention due to low cost, high efficiency, and good compatibility of functional groups. The reactions have following disadvantages due to the inherent nature of catalytic system: expensive catalysts, complex ligands, cocatalysts and trace metals residues. The transition-metal-free amide activation strategies for synthesis of ketones avoid the above problems with high efficiency and simple treatment. From the perspective of sustainable development, the development of amide activation strategy without transition metals has great significance. In this paper, the synthesis of ketones by C–N bond cleavage of amides without transition metals were reviewed. The main contents as follows: (1) synthesis of ketones by direct addition of alkali metal/alkaline-earth metal reagents to amides; (2) the Brønsted base-promoted non-decarbonylative cross-coupling reaction of amides and alkanes with activated groups; (3) synthesis of ketones by cleavage of amide C–N bond based on activation strategy; (4) acid-promoted Friedel-Crafts acylation reaction of amide; (5) Lewis acid-promoted the non-decarbonylative cross-coupling reaction between amide and alkyl ketone. This review provides inspiration for the subsequent development of economic and green amide activation reaction.