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 degrees C and of 6-arylethynylphenanthridines when performed at 80 degrees C.