Lewis acid catalyzed nenitzescu indole synthesis

Abstract

A novel method for Lewis acid catalyzed Nenitzescu indole syntheses of 5‐hydroxyindoles bearing different substituents in positions 1 )Alk, Bn, Ar), 2 )Me, Et, Ph), and 3 )COOEt, COMe, CONHPh) as well as tricyclic derivatives are reported. The method is simple, rapid, efficient, and allows preparation of hydroxyindoles from 1,4‐benzoquinone and enamines in good to excellent yields with the use of low‐polar solvents in the presence of weak Lewis acids catalysts. The formation of 5‐hydroxyindoles under such mild conditions is explained in terms of a non‐redox mechanism.

Preparation and Application of Solid, Salt‐Stabilized Zinc Amide Enolates with Enhanced Air and Moisture Stability

“…Addition of 2 b to 4‐methoxybenzonitrile ( 13 ) gave an intermediate that reacted with benzylamine in an addition–elimination process, providing the unsaturated 3‐amino‐substituted N ‐morpholino amide 14 in 56 % yield. Treatment of 14 with benzoquinone in the presence of ZnCl 2 (10 mol %) provided the expected indole 15 in 78 % yield in a Nenitzescu reaction . The structure of 15 was confirmed by X‐ray analysis .…”

“…Tr eatment of 14 with benzoquinone in the presence of ZnCl 2 (10 mol %) provided the expected indole 15 in 78 %yield in aNenitzescu reaction. [22] Thes tructure of 15 was confirmed by X-ray analysis. [23] Methylation of the phenolic hydroxy group of 15 with MeI in the presence of K 2 CO 3 afforded the methylated indole derivative 16 in 94 %y ield.…”

Solid Organozinc Pivalates: A New Class of Zinc Organometallics with Greatly Enhanced Air- and Moisture-Stability

“…Finally, these new zinc enolates have proved to be very useful for the preparation of a potent anti-breast cancer candidate 40 by using an addition of 39a to a benzonitrile followed by a Nenitzescu reaction. 50 The N-morpjholino amide 41 was converted into an aldehyde function by using CpZr(H)Cl (Scheme 19).…”

Nenitzescu 5‐Hydroxyindole Synthesis

“…Velezheva and coworkers described the Lewis acidcatalyzed Nenitzescu indolization using zinc iodide in dichloromethane (Scheme 9, equation 1 and 43-45) [23], later improved to the use of zinc chloride (equations 2, 3) [24]. These workers also propose a face-to-face sandwich electron-transfer complex that mediates the oxidation-reduction step (equation 1).…”