One-pot synthesis of pyrano[4,3-b]quinolinones from 2-alkynyl-3-formylquinolines via oxidative 6-endo-dig ring closure

A new regioselective one-pot procedure to synthesize pyranoquinolinones from readily available 2-alkynyl 3-formylquinolines under mild NaClO2/H2O2 conditions in good yields has been explored. This reaction sequence, involving oxidation followed by regioselective electrophilic 6-endo-dig cyclization is more efficient over the traditional Pd(0)-mediated synthesis. When scavenger-free conditions were used, unusual chlorinated furoquinolinone derivatives were obtained.