Absbactz 4-O.w-2-cyclopentenyl acetate has been shown to behave as a conjunciive reagent for Tandem Diels-Alder Reaction under CJwninum chloriak catalysis. This m&odologyrqwentsamildand -chboparion ofhydrqtkwwnes. Snuciure analysisoftheleaclionproductsbyNMRspectnwcopyi?dircussed Development of methods for the synthesis of polycarbocyclic compounds by efficient, short routes is an interesting challenge and provides useful ground for the testing of new synthetic strategies. Continuing our study on the Die&Alder reaction of cycloalkenones2, we investigated on a new approach to rapidly synthesize polycarbocyclic molecules by multiple Diels-Alder methodology? We observed that under AlCl3 catalysis, the primary cycloadducts, obtained by reaction of 4-oxo-2-cyclopentenyl acetate (1)4 with cyclic or acyclic dienes, elimiuated acetic acid quickly and then, the new enone generated in situ, underwent a subsequent cycloaddition leading to hydrofluorenones. While our study was iu progress, ZwanerMq et al.5 published an interesting paper on the Lewis acid catalyzed [4+2] cycloadditions of acetoxy ketone 1. lkse authors reported that when the reaction was performed under AlC13 catalysis, acetic acid was cl&mated from the primary cycloadducts, thus showing that 4-oxo-2-cyclopentenyl acetate (1) behaved as a synthetic equivalent of cyclopentadienone6. However, they did not mention any product obtained by Tandem Diels-Alder reaction. We report herein that 4-0x0-2-cyclopentenyl acetate @-acetyl-2-cyclopenten-l-one) (1) behaves as a conjunctive reagent for a mild, efficient one-pot Taudem Diels-Alder React& thus providing promising prospect for building up hydrofbuuenones rapidly. Since acetoxy ketone 1 is available in (+) and (-) forms', this method provides a convenient entry to optkally active substituted hydrofluommmes which are useful intermediates8 for the synthesis of biologically imeres@ compounds such as gibbe&bns, Dhomostemids, nordikrpenoids and HPA analogues. The results of the study of the AlC!13 catalyxed cycloadditions of 4-oxo-2-cyclopentenyl acetate (1) with 1,3-butadiene, 2,3ðyl-1,3-butadiene, (E)piperylene, O_l-methoxy-1,3-butadiene and cyclopemadiene are herein reported l991,56,4499. a) The overall reaction yields refer to the isolated compounds. b) The pictorialization of the racfmic compounds is based on an arbitrary choice of absolute collfi8urations.