Palladium‐Catalyzed Reaction of MBH Acetates and Terminal Alkynes: Cascade Synthesis of Phenanthridine and 6‐Arylethynylphenanthridine

We have described the palladium‐catalyzed regioselective cascade synthesis of phenanthridines and 6‐arylethynylphenanthridines in good to excellent yields from a reaction between Morita–Baylis–Hillman (MBH) acetates and terminal alkynes. These cascade reactions are temperature controlled and favor the formation of phenanthridines when conducted at 50 °C and of 6‐arylethynylphenanthridines when performed at 80 °C. A palladium‐catalyzed cascade reaction of Morita–Baylis–Hillman (MBH) acetates and terminal alkynes was developed. This regioselective synthetic approach is temperature controlled and favors the formation of phenanthridines when conducted at a lower temperature and 6‐arylethynylphenanthridines when performed at a higher temperature.