The Copper‐Catalyzed [4 + 1] Annulation of Ethynyl Methylene Cyclic Carbamates With Various Activated Methylene Compounds to Construct Spiro‐Cyclopentane Derivatives

ABSTRACT Novel copper‐catalyzed [4 + 1] annulation synthesizes spiro‐cyclopentanes using bis‐electrophilic Cu‐aminoallyl cations (from EMCCs) and activated methylene dinucleophiles. The methodology exhibits broad substrate scope, accommodating EMCCs with electron‐donating/withdrawing aryl groups /alkyl chains, and various activated methylene partners, providing a versatile alternative to construct spiro‐cyclopentane via conventional [3 + 2] cycloadditions.