Regio‐ and Stereoselective Intramolecular Protocol to Access Dihydropyrano[3,4‐ <i>b</i> ]indol‐1(3 <i>H</i> )‐ones via a Tandem C‐3 Propargylation/Cycloisomerization

Herein, a novel and efficient one‐pot synthetic strategy is reported, enabling the regio‐ and stereoselective formation of dihydropyrano[3,4‐ b ]indol‐1(3 H )‐ones via a tandem C‐3 propargylation followed by cycloisomerization of indole‐substituted propargylic esters. This organic transformation proceeds through an unprecedented selective C‐3 propargylation facilitated by Lewis acid catalysis, leading to a pivotal C‐3 propargylated indole‐2‐carboxylic acid and a subsequent gold‐catalyzed Z‐selective cycloisomerization to afford the pyrano indolone derivatives. In this atom‐economic protocol, one new CC and CO bonds are formed.