A Facile Synthesis of Furotropone Derivatives by an Application of Claisen Rearrangement

Abstract

The reaction of 1,4-dichloro-a-2-butene with dipotassium salt of 5-hydroxytropolone i n presence of 18-crown-6-ether afforded 544-chlorotrans-2-butenyloxy) tropolone and 2,5-di (4-chloro-trans-2-butenyloxy )--tropone which were transformed into furotropone derivatives by dehydrochlorination under the conditions of Clairen rearrangement.Recently, we have found that several 2-(2-alkenyloxy) tropones can be prepared by a mild condensation of naked tropolonate anion, generated in crown-ether-containing benzene solutions, with corresponding allylhalides!'