Cobalt(I)-Catalyzed [2+2] and [3+2] Cycloaddition Reactions between Alkylidenecyclopropanes and Alkynes

Alkylidenecyclopropanes (ACPs) are highly-strained but thermally-stable structures that can undergo a multitude of different reactions with the assistance of transition metal catalysts, especially cycloaddition reactions toward the synthesis of carbocycles and heterocycles. However, the majority of reported reactions utilize harsh conditions such as high temperature or other high-energy compounds. ACP reactivity has seldom been explored under cationic cobalt(I)-catalyzed systems. Here, we report two novel cobalt(I)-catalyzed cycloaddition reactions between ACPs and alkynes: (i) an enantioselective [2+2] cycloaddition that yields uncommon spiro[2.3]hex-4-ene motif up to 80% yield and up to 96% ee; and (ii) a [3+2] cycloaddition that yields alkylidenecyclopent-1-ene structures between 20-60% yield. Both reactions are performed under ambient conditions.U.S. National Institute of Health (R01 GM108762 to TVR)U.S. National Science Foundation (CHE-1362095 and CHE-1900141 to TVR)No embargoAcademic Major: Chemistr