Copper‐Catalyzed Synthesis of C‐2 Substituted Indolin‐3‐Ones and Indolin‐3‐One [4+2] Cycloadducts Through Azide‐Tethered Iodonium Ylides

In recent years iodonium ylides have gained popularity as versatile metallocarbene precursors, functioning as alternatives to sensitive and potentially toxic diazo compounds. However, their application in metallocarbene‐mediated heterocycle construction has been limited. Herein, we describe a strategy for the synthesis of C‐2 substituted indolin‐3‐ones using azide‐tethered iodonium ylides as metallocarbene precursors under copper catalysis. The formation of an electrophilic C‐acylimine intermediate allows the addition of a broad spectrum of nucleophiles, as well as electron‐rich and unactivated dienes, furnishing highly substituted indolin‐3‐ones and indolen‐3‐one [4+2] cycloadducts. The remarkably short reaction times, high yields, mild conditions, and scalability render this methodology attractive for the synthesis of new scaffolds in drug discovery.