Synthesis of New 1‐Hydroxyindole‐2‐Carboxylates and Mechanistic Studies on Reaction Pathways

Synthesis of new 1‐hydroxyindole‐2‐carboxylates 1 and mechanistic studies on the reaction pathways were described. The substrates 2 , prepared through two‐step synthetic sequences, were treated with nucleophiles in the presence of SnCl 2  · 2H 2 O to obtain compounds 1 . In particular, the mechanistic studies led to a significant finding that reactions with thiol nucleophiles occur through a newly proposed pathway (path B: 1,4‐addition followed by reduction/condensation) rather than through a previously assumed pathway (path A: reduction/condensation followed by 1,5‐addition). Further mechanistic investigations revealed steric effects of o ‐substituents in 2 governing the ratio of products ( 1i / 7 ).