Abstract The thermal reaction of furan with the ester CF 3 C CCHMeO 2 CCH 2 Ph (2a)(1.1: 1 molarratio) at 100 C gives a mixture of Diels-Alder 1: 1 (3)(51%), 2: 1 (4)(20%) and 3: 1 (5)(5%) adducts (each as two diastereomers). The 2: 1 adducts are the exo-endo