Formal [3+2] Annulation of Copper‐Allenylidenes with 3‐Oxo‐3‐Arylpropanenitriles: Synthesis of Tetrasubstituted Furans.

The copper‐catalyzed decarboxylative [3+2] annulation of ethynyl benzoxazinanones with 3‐oxo‐3‐arylpropanenitriles has been developed, producing tetrasubstituted furan derivatives in moderate to high yield. This reaction was generally compatible with a wide range of substrates. Notably, the intermediate copper‐allenylidenes worked as a C2 synthon in the cycloaddition reaction. [ABSTRACT FROM AUTHOR]