Synthesis and reactions of 3‐aroyl derivatives of 4‐hydroxy‐2‐quinolones and 4‐hydroxycoumarin

Abstract

Abstract 3‐Aroyl‐4‐hydroxy‐2‐quinolones 4 and 11 can be synthesized starting with 1 or 9 via Fries rearrangement of the corresponding esters 3 and 10 , catalyzed by potassium cyanide and 18‐crown‐6. A one pot procedure is presented in which the esters do not need to be isolated. Reduction of the aryl ketones 4 and 11 with zinc dust leads to the benzyl derivatives 5 and 12 . Reaction of the aryl ketones 4 and 11 with hydroxylamine and subsequent heating of the crude product leads via thermal Beckmann rearrangement and dehydration to oxazoloquinolones 7 and 14 . 2‐Aroyloxypyrido[1,2‐ a ]pyrimidin‐4‐ones 17 and 20 could not be converted to the corresponding ketones by Fries rearrangement.