Unexpected synthesis of 3,5-diethoxycarbonyl-2-pentafluorophenyl-4-phenyl-7,8,9,10-tetrafluoro-4,5-dihydrobenzo[b]oxacin-6-one

The reaction of ethyl pentafluorobenzoylacetate with benzaldehyde in the presence of a base affords 3,5-diethoxycarbonyl-2-pentafluorophenyl-4-phenyl-7,8,9,10-tetrafluoro-4,5-dihydrobenzo[b]oxacin-6-one in contrast to fluoroalkyl-containing 3-oxo esters yielding 3,5-dialkoxycarbonyl-2,6-dihydroxy-2,6-difluoroalkyl-4-phenyltetrahydropyranes under the same conditions.