A supported Fe/Ru catalyzed three-component relay reaction through a hydrogen borrowing strategy: conversion of crude α-hydroxy acids into valuable N-heterocycles†

Abstract

We developed an Fe–Ru/γ-Al₂O₃ relay catalyst to promote the multi-component reaction of biomass derived α-hydroxy acids and 2,5-dimethoxytetrahydrofuran with 2-nitroaromatic amines, enabling the synthesis of quinoxalines from inexpensive starting materials in one step. In this strategy, α-hydroxy acids displayed multifunctional roles as a hydrogen source, carbon synthon, and acidic additive. Notably, industrial grade lactic acid and mixed α-hydroxy acids extracted from fruits could be directly used and converted into a normalized quinoxaline product. Significantly, practical synthesis from glucose or fruits and successive transformation into a twisted-intramolecular charge transfer (TICT) based luminogen were accomplished nicely. Mechanistic studies showed that the equilibrium of the dehydrogenation step was promoted through tandem hydrogenation and cyclization reactions. Our work demonstrates the feasibility of chemical transformation of crude bio-based α-hydroxy acids into N-heterocycles and opens the way to provide high-value luminescent materials from biomass.