Buchwald-Hartwig versus Microwave-Assisted Amination of Chloroquinolines: En Route to the Pyoverdin Chromophore

The reaction of 2-chloro-6,7-dimethoxy-3-nitroquinoline with a series of amines and aminoalkanoates under basic microwave-mediated conditions and under Buchwald-Hartwig amination conditions is reported. The microwave irradiation favored the reaction with amines, resulting in yields of up to 80%, whereas amino acid functionalization gave yields comparable to those of Buchwald-Hartwig amination. tert-Butyl (2R)-4-[(6,7-dimethoxy-3-nitroquinolin-2-yl)amino]-2-hydroxybutanoate was successfully cyclized to the pyoverdin chromophore, a subunit of siderophores.