Synthesis of Phosphinines from Co^II-Catalyzed [2+2+2] Cycloaddition Reactions

The CoII-catalyzed [2+2+2] cycloaddition of functionalized diynes and phosphaalkynes resulting in the formation an array structurally interesting phosphinines is reported. A combination 1,2-bis(diphenylphosphino)benzene (dppbenz) CoI2 turned out to be most suitable active catalyst system under microwave reaction conditions. Chemoselective cyclizations presence nitriles have been observed, a number carbonyl functionalities are tolerated as well. can successfully conducted with 1:1 ratio phosphaalkyne/diyne substrate. Model reactions benzonitrile diyne demonstrated that CoII catalysts bisphosphines prefer carbocyclization, while reduction lower oxidation states promotes heterocyclization corresponding pyridine. mechanism comprising state for cyclotrimerization process proposed rationalized based on control experiments theoretical calculations.