An Assembly of Pyrano[3,2‐b]indol‐2‐ones via NHC‐Catalyzed [3 + 3] Annulation of Indolin‐3‐ones with Ynals†.

Comprehensive Summary: We report herein an unprecedented N‐heterocyclic carbene‐catalyzed formal [3 + 3] annulation of ynals with N‐Ts indolin‐3‐ones under the oxidation condition affording the functionalized pyrano[3,2‐b]indol‐2‐ones. The alkynyl acylazoliums via the combination of a carbene with ynals in the presence of oxidate proved to be the important intermediates for the success of this transformation. This method features a broad substrate scope and mild conditions, including axially chiral skeletons with suitable substitutions. [ABSTRACT FROM AUTHOR]