Fluoroaryl containing β,β′-dioxoesters in the synthesis of fluorobenzopyran-4(2)-ones

Fluoroaryl containing β,β′-dioxoesters and their copper(II) chelates have been prepared by acylation of ethyl acetoacetate with 2,6-dimethoxy-3,4,5-trifluorobenzoyl, 2-methoxy-3,4,5,6-tetrafluorobenzoyl and pentafluorobenzoyl chlorides. Cyclization of these β,β′-dioxoesters leads to formation of substituted fluorochromones. Depending on conditions, 2-methyl-5-methoxy-6,7,8-trifluoro-3-ethoxycarbonylchromone hydrolyzed to 5-hydroxy-2-methyl-6,7,8-trifluorochromone or 5-hydroxy-2-methyl-6,7,8-trifluorochromone-3-carboxylic acid. The same chromone reacts with morpholine to form a seven-substituted product and ammonium hydroxide to give 3-iminoacetyl-4-hydroxy-5-methoxy-6,7,8-trifluorocoumarin. Hydrolysis of the latter affords 3-acetyl-4-hydroxy-5-methoxy-6,7,8-trifluorocoumarin. Ethyl-2-(2,6-dimethoxy-3,4,5-trifluorobenzoyl)-3-oxobutanoates undergoes ketone-splitting to 1-(2,6-dimethoxy-3,4,5-trifluorophenyl)-1,3-butandione.