Diels-Alder reactions of polyfluorinated 2,4-cyclohexadienones with alpha-and beta-fluorostyrenes

Thermal reactions of polyfluorinated 2,4-cyclohexadienones bearing an addit ional electron withdrawing group at carbon 3 with alpha- and beta-fluorosty renes yield mixtures of diastereomeric Diels-Alder products. Presuming a co ncerted process, these reactions proceed as [4+2]cycloadditions with invers e electron demand. In contrast, a polyfluorinated 2,4-cyclohexadienone with a methoxy group in the three-position shows no reaction with either alpha- or beta-fluorostyrene, but does undergo rearrangement to give a polyfluori nated 2,5-cyclohexadienone. 4-Fluorooct-4-en-3-one is inert to all polyfluo rinated 2,4-cyclohexadienones. (C) 1999 Elsevier Science S.A. All rights re served.