A Room-Temperature Synthesis of 3-Methylidene-2,3-dihydro-4-quinolones from o -Aniliopropargy Alcohols and Aldehydes

Abstract Through a room-temperature reaction between o-anilinopropargyl alcohols and aldehydes, various 3-methylidene-2,3-dihydro-4-quinolones were synthesized with 3 mol % TfOH as a catalyst. This transformation likely proceeds via acetalization of the aldehyde with CH(OCH3)3, acetal-intercepted Meyer–Schuster rearrangement, 1,3-migration, intramolecular conjugated addition, and departure of the methoxy group. Acetalization reagent CH(OCH3)3 should play multiple roles. The reaction uses 3 mol % catalyst loading, accommodates diverse substituents, and gives high yield, making it a practical alternative for the synthesis of 3-methylidene-2,3-dihydro-4-quinolones.