Copper-catalyzed oxidative amination and allylic amination of alkenes

Enamines and enamides are useful synthetic intermediates and common components of bioactive compounds. A new protocol for their direct synthesis by a net alkene C-H amination and allylic amination by using catalytic Cu ^II in the presence of MnO₂ is reported. Reactions between N-aryl sulfonamides and vinyl arenes furnish enamides, allylic amines, indoles, benzothiazine dioxides, and dibenzazepines directly and efficiently. Control experiments further showed that MnO₂ alone can promote the reaction in the absence of a copper salt, albeit with lower efficiency. Mechanistic probes support the involvement of nitrogen-radical intermediates. This method is ideal for the synthesis of enamides from 1,1-disubstituted vinyl arenes, which are uncommon substrates in existing oxidative amination protocols. A new protocol for the direct synthesis of enamides and allylic amines by oxidative N-H/C-H coupling of N-sulfonylanilines with vinylarenes is presented. The reaction works in both inter- and intramolecular modes and is catalyzed by copper salts by using MnO₂ as the stoichiometric oxidant (see scheme). Nitrogen heterocycles including indoles, benzothiazine dioxides, and dibenzazepines can be formed.