Novel Solvent Promoted Synthesis of Furo[3,2‐c]pyridines from 3‐Alkynyl‐4‐pyrones: Synergy of a 4‐Pyrone and an α‐Alkynyl Enone Fragments

Furo[3,2‐ c ]pyridines are an important class of heterocyclic compounds, both in medicine and in materials science. In this work, we present a novel strategy for the synthesis of furo[3,2‐ c ]pyridines from 3‐alkynyl‐4‐pyrones and ammonium acetate. The reaction proceeds at room temperature in hexafluoroisopropyl alcohol without a catalyst in 35%–84% yield. The mildness of conditions is allowed by mutual activation of the 3‐alkynyl‐4‐pyrone fragments. A wide range of substrates was synthesized using Sonogashira coupling with 3‐bromo‐4‐pyrones bearing electron‐withdrawing groups. The developed method is the first example of a tandem formation of both cycles in the furo[3,2‐ c ]pyridine framework. Hydration of 3‐alkynyl‐4‐pyrones to polysubstituted furans and some chemical transformations of the main products were also studied.