Regiodivergent Annulation of Alkynyl Indoles To Construct Spiro-pseudoindoxyl and Tetrahydro-β-carbolines

Abstract

Regiodivergent annulations of 3-phenoxy alkynyl indoles have been developed and tuned by protective groups through gold catalysis. With electron-donating protective groups, the substrate followed a C3-selective annulation and gave structurally interesting tetrahydro-β-carboline derivatives possessing potential bioactivity. Using electron-withdrawing protective groups, the substrate underwent a C2-selective annulation and afforded the structurally useful spiro-pseudoindoxyl found in natural indole alkaloids. Notably, an interesting and unusual 1, 2-migration of the phenoxy group was found in the C3-selective process.