The Chemistry of 1-Hydroxyindole Derivatives: Nucleophilic Substitution Reactions on Indole Nucleus

γ-Carbolines and their hydrogenated derivatives. 1. Aromatic γ-carbolines: methods of synthesis, chemical and biological properties (review)

“…2-Ethoxy-3H-indole, which is in tautomeric equilibrium with 2-ethoxy-1H-indole, is capable of reacting with a series of CH-acids (e.g., malononitrile) and provides the basis for the production of 4-cyano-γ-carboline derivatives [45]. An extremely interesting method for the synthesis of γ-carbolines was proposed on the basis of 3-formyl-1-methoxyindole (12) [46], which has the ability to enter into substitution with nucleophilic agents with the formation of 2-substituted 3-formylindoles [47]. When compound 14 is boiled with ammonium acetate in alcohols for several hours a mixture of carbolines 15 and 16 is formed.…”

Synthesis of 3-arylated indolines from dearomatization of indoles

“…Somei deployed a S N Ar reaction with 1-fluoro-2,4-dinitrobenzene 77 to trigger this sequence which is limited to electron-poor fluorobenzene derivatives. 21 In order to expand the scope of arylating agents to achieve the O-arylation of N-hydroxyindoles, our group evaluated several metal-catalyzed methods such as Chan-Lam, Buchwald and Ullmann couplings without success. Eventually, the use of diaryliodoniumtriflate 81a as electrophilic aryl reagent in the presence of potassium carbonate was successful to achieve the transition metal-free O-arylation of 80 and allowed us to obtain 44% of benzofuro [2,3-b] …”

Ortho-selective C–H arylation of phenols with N-carboxyindoles under Brønsted acid- or Cu(i)-catalysis

“…In continuation of our interest in aliphatic Umpolung chemistry based on N–O bond redox, 16 we turned our attention to the aromatic Umpolung by way of N -hydroxyindoles which was pioneered by Somei and coworkers. 17 Somei and others disclosed C3-arylation of indoles via [3,3]-sigmatropic rearrangement of N -carboxyindoles 18 that were accessed by nucleophilic aromatic substitution (S N Ar) 18 a , b or by the O -arylation of N -hydroxyindoles with biaryliodonium salt. 18 c S N 2′ substitution N -hydroxyindoles with indoles and pyrroles was also demonstrated ( Scheme 1B ).…”