Indolylmethanols as C4 Synthons for the Asymmetric Synthesis of Indole‐Fused Spiro Compounds

Comprehensive Summary A novel asymmetric [4+2] cycloaddition of indolylmethanols with aurones via chiral phosphoric acid (CPA) catalysis has been established. Enantioenriched indole‐fused spiro compounds were obtained in good yields (60%–89%) with excellent diastereoselectivities (up to >19 : 1 dr) and enantioselectivities (83%–99% ee) with broad substrate scope. This approach not only enabled the first catalytic asymmetric [4+2] cycloaddition of 3‐methyl‐2‐indolylmethanols, but also represented different reactivity from traditional indolylmethanol chemistry. In this reaction, 3‐methyl‐2‐indolylmethanols behaved as C4 synthons rather than C3 synthons.