Ene-hydrazide from Enol Triflate for the Regioselective Fischer Indole Synthesis

Abstract

Ene-hydrazide prepared from enol triflate undergoes a Fischer indolization reaction to give the corresponding indole with complete regioselectivity. The starting enol triflate is readily accessed in regiochemically defined form from the ketone precursor via various well-established methods. This new protocol was successfully applied to the synthesis of desbromoarborescidine A, a natural beta-carboline alkaloid, difficult to prepare with conventional Fischer indole synthesis.