Synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via tandem reactions under transition metal- and additive-free conditions†
A novel method for the synthesis of 3-(2-quinolyl) chromones through a tandem [3+2] cycloaddition/ring-opening/O-arylation from ynones and quinoline N-oxides has been developed. This protocol proceeds under transition metal- and additive-free conditions and can be amplified to the gram level in 91% yield. 3-(1-Isoquinolyl) and 3-(2-pyridyl) chromones are also successfully synthesized using isoquinoline and pyridine N-oxides under basic conditions. Various heteroarene-contaning chromones were afforded in 30–98% yields, which are difficult to be obtained and are compounds of interest in pharmaceutical chemistry and chemical biology.