Practical Synthesis of Phenanthrid­inones by Palladium-Catalyzed One-Pot C–C and C–N Coupling Reaction: Extending the Substrate Scope to o-Chlorobenzamides
A highly efficient construction of phenanthridinone derivatives from o-halobenzamides was developed by using a phosphine-free palladium catalyst in N,N-dimethylacetamide. The domino reaction proceeds through a sequential C–C and C–N bond-formation process in one pot. This protocol exhibits broad substrate scope and affords a series of phenanthridinones in up to 93 % yield. Importantly, the protocol could also be applied for the less reactive o-chlorobenzamides. The approach constitutes the first example of the synthesis of phenanthridinones from this kind of substrate. Moreover, the success of a gram-scale reaction demonstrated that this operationally simple process is scalable.