FLUORINATED ACETYLENES .9. REACTION OF FURAN WITH THE PHENYLETHANOATE ESTERS DERIVED FROM TRIFLUOROPROPYNYL SECONDARY ALCOHOLS

The thermal reaction of furan with the ester CF3C = CCHMeO2CCH2Ph (2a) (1.1:1 molar ratio) at 100-degrees-C gives a mixture of Diets-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 isomers arising from exo-addition to the least substituted double bond in the 1:1 adducts and the complete stereochemistry of both diastereomers has been established by X-ray crystallography; the 3:1 adducts are formed analogously by exo-addition to the 2:1 adducts. It is calculated that the 1:1 adduct diastereomers are initially formed in the ratio c. 55:45. Similarly, reaction of furan with the ester CF3C = CCHPhO2CCH2Ph (2b) (c. 1.5:1 molar ratio) affords as major products the corresponding 1:1 (10) (44%) and 2:1 (11) (38%) adducts (each as two diastereomers).