2-Substituted-2,3-dihydro-1 H -quinolin-4-ones via acid-catalyzed tandem rupe rearrangement-donnelly-farrell ring closure of 2-(3′-hydroxypropynyl) anilines

A range of 2-substituted 2,3-dihydro-1H-quinolin-4-ones have been synthesized from anilines by a two-step process involving Sonogashira coupling with a propargyl alcohol then acid-catalyzed cyclization of the resulting 2-(3′-hydroxypropynyl)anilines. The cyclization reaction appears to proceed via regioselective rearrangement of the propargyl alcohol to an α,β-unsaturated ketone (Rupe rearrangement) and then 6-endo-trig ring closure (Donnelly-Farrell cyclization). The isolation of the α,β-unsaturated ketone intermediate in one example supports this pathway.