Superacid-catalyzed tandem Meyer–Schuster rearrangement/intramolecular hydroamination of o-anilinopropargyl alcohols for the synthesis of 2,3-dihydro-4(1H)-quinolones

A TfOH-catalyzed synthesis of 2,3-dihydro-4(1H)-quinolones from o-anilinopropargyl alcohols was developed. Studies of N-protecting groups and substituents in phenyl rings showed that diverse groups could be applied. By controlling the catalyst loading, o-anilinopropargyl alcohols underwent the expected transformation smoothly to produce N-protected or N-deprotected 2,3-dihydro-4 (1H)-quinolones in good yields. This transformation probably involved a tandem Meyer–Schuster rearrangement/intramolecular hydroamination reaction process.