Synthesis of 5-Methylindole-4,7-quinone through a New Construction of the Functionalized Indole Ring Based on the Allene-mediated Electrocyclic Reaction Involving the Pyrrole [b]-Bond

Abstract

A new synthesis of an indole ring based on an electrocyclic reaction of a 2-alkenyl-3-allenylpyrrole intermediate generating from 2ethenyl-3-propargylpyrrole was established.A synthesis of 5-methylindole-4,7-quinone (1) was completed in seven steps from the 4-oxygenated 5methylindole (13a).It was demonstrated that the structure of natural product (1), isolated from Dropella fragum, is not at least 5-methylindole-4,7quinone (1).