The inability to observe Cope rearrangment at elevated temperatures for diethyl a- allylphenylmal~ nate~ does not extend to the analogous systems resulting from replacement of the benzene ring by 2-and 3-thiophene nuclei. Thermal rearrangement of diethyl a-allyl-2- thienylmalonate (5) at 250-260 OC for 12 h produces the expected Cope rearrangement product diethyl (3-allyl-2-thieny1) malonate (6)(49%) accompanied by ethyl 6-carboeth- ...