The syntheses of new 2,3-disubstituted 4-chloro-1-hydroxyindoles were described. The conjugate nitro ketoester was reacted with various thiol and alcohol nucleophiles by the action of stannous chloride dihydrate through the unique processes of reduction of nitro group, intramolecular condensation, and addition of nucleophiles in one pot, to provide multisubstituted 1-hydroxyindoles. The reactions with thiol nucleophiles provided better results than those with alcohols, and, in particular, secondary and tertiary thiols provided best yields.

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 SnCl2 · 2H2O 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).

The syntheses of new 3-[(alkylthio)methyl]-1-hydroxy-2-phenylindoles are presented. The substrates, obtained by efficient three-step synthesis, were treated with various thiol nucleophiles in the presence of SnCl2·2H2O to provide target compounds, through the consecutive processes of reduction, condensation, and addition in one pot. The mechanistic studies on reaction pathways and the involved intermediates are described.

Synthesis of new, highly substituted, and hindered 1‐hydroxyindole‐2‐carboxylates was achieved through a unique pathway of reduction, condensation, and addition reactions in one pot.

Synthesis of New Highly Substituted and Hindered 1-Hydroxyindole-2-carboxylates. -On treatment with aliphatic alcohols, thiols, or thiocarboxylates, the reductive cyclization of substrates (II) or (VI) in the presence of tin(II) chloride affords the title compounds in good to modest yields. -(PARK, Y. K.; KIM, H.; LEE*, S. H.; Bull. Korean Chem. Soc. 37 (2016) 1, 82-90, http://dx.