Abstract

[2+2+2] Cycloadditions of heterocumulenes and nitriles represent an efficient, atom-economical method of synthesizing heterocycles and, to a lesser extent, carbocycles. Cycloadditions of heterocumulenes including isocyanates, carbodiimides, carbon dioxide, carbon disulfide, ketenes, as well as nitriles are explored. The heterocumulene is typically coupled with an alkyne or diyne, forming 6-membered heterocycles, although multiple heterocumulenes are sometimes incorporated. The reactions are generally catalyzed by late-transition-metal catalysts, albeit nucleophilic catalysts and early-transition metals are sometimes used.