Cyclopentadiene compounds, tethered to an a,@ unsaturated ester functionality, have been prepared by the direct alkylation of the corresponding iodide or tosylate with cyclopentadienylmagnesium chloride. For example,~ O-CH, CH~ C (CH,)~ CH= CHCO~ C (CH~)~ reacted with cyclopentadienylmagnesium chloride at 0" C to yield the alkylated cyclopentadiene, which on heating at 75" C underwent a Diels-Alder reaction to give an ...