Derivatives of Alkyl 2-Hydroxy-3-oxocyclopent-1-enecarboxylates and Intermolecular [4+2] Cycloadditions of Cyclopentadienones Prepared Therefrom

Some derivatives of alkyl 2-hydroxy-3-oxocyclopent-1-enecarboxylates have been synthesized and their reactivity as progenitors of cyclopentadienones for intermolecular [4+2]-cycloaddition reactions has been evaluated. It was found that the derivative containing a phosphate ester leaving group gave better yields in the cycloaddition reaction among the derivatives studied. The yields of the cycloaddition reactions were moderate, perhaps due side reactions not leading to the reactive intermediate cyclopentadienone.