Synthesis of N‐Hydroxyindole Derivatives via Pd‐Catalyzed Electrophilic Cyclization

Abstract

A synthetic protocol for the synthesis of C2‐substituted N‐hydroxyindoles has been developed which consists of Sonogashira coupling, partial reduction of the nitro group, and Larock cyclization. This protocol features superior generality and efficiency over conventional alternatives.

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

“…The requisite N -hydroxyindole derivatives were synthesized according to the literature. 20 Particularly, for the C2-substituted N -hydroxyindoles used in this study, a sequence comprising Sonogashira coupling of o -halonitrobenzenes, partial reduction into hydroxylamines, and Larock-type cyclization, were found general. 20 d With an N -carboxyindole 1a and 3,5-dimethoxyphenol 2a as prototypical substrates, we set out to explore the possibility of a non-metal catalyzed C–H/C–H coupling, employing various Brønsted acids (entries 1–6, Table 1 ).…”