A Versatile Cobalt Catalyst for Secondary and Tertiary Amide Synthesis from Various Carboxylic Acid Derivatives

A wide range of carboxylic acid derivatives including aldoximes, aldehydes, nitriles, primary amides, and carboxylic acid esters were reacted with various amines to form secondary and tertiary amides from a single cobalt catalyst. CoCl2/PPh3 was revealed as a universal, efficient catalyst for secondary or tertiary amide synthesis from a variety of starting materials. A two-step mechanism for the secondary amide synthesis from aldoximes was proposed and the substrate scope was intensively investigated. This study informs us about the reactivity of the cobalt catalyst with regards to carboxylic acid derivatives, along with the functional group tolerance of the substrates.