One-pot iron chloride-catalyzed sustainable syntheses of quinolines from amino acids, alkyl lactate and arylamine†

An iron(III)- and oxygen-promoted one-pot method for the efficient syntheses of quinolines from amino acids, alkyl lactate, and arylamine was carried out. The efficient tandem cyclization of the three components begins with the breaking of the amino acids' C–C and C–N bonds and the lactate's O–H bond, followed by sequential condensation and coupling to form new C–N and C–C bonds. The reaction is based on biomass-based amino acids and alkyl lactate, using earth-abundant metals as catalysts and oxygen as the oxidizer, without adding additional solvents; renewable aldehydes are generated and the reuse of alkyl lactate is realized, which is remarkable for its green and sustainable characteristics. More than 40 quinolines were synthesized in isolated yields of up to 75%. This one-pot, multi-step synthesis method significantly shortens the life cycle of the biomass-based conversion process. This study demonstrates the promise of biomass conversion in sustainable organic synthesis and lays the foundation for the sustainable conversion of small biomolecules in vitro and bio-based feedstocks into high-value-added chemicals.