Synthesis of fused-tricyclic indole derivatives through an acid-promoted skeletal rearrangement
摘要:
We developed a novel method for synthesizing fused-tricyclic indole derivatives with a 3-aminomethyl indole motif through a reaction cascade involving ipso-Friedel-Crafts alkylation of phenols, rearomatization of the spirocyclohexadienone unit, and iso-Pictet-Spengler reaction. Using TFA as an acid promoter, six-, seven-, and eight-membered ring-fused indoles were obtained in 31-99% yield. (C) 2014 Elsevier Ltd. All rights reserved.
An acid-promoted novel skeletal rearrangement is described. Using trifluoroacetic acid as the acid promoter, an intramolecular ipso-Friedel-Crafts-type addition of phenols to 3-alkylidene indolenium cations, formation of iminium cations through rearomatization of the spirocyclohexadienone units, and intramolecular Pictet-Spengler reaction proceeded sequentially, producing tricyclic indole derivatives