Synthesis of α-phenylseleno-α,β-unsaturated esters by Wittig-type reactions. Studies on the Diels–Alder reaction

Ethyl α-phenylseleno-α,β-unsaturated esters were prepared by the reaction of tri-ethyl phosphonoacetate anion and ethoxycarbonyl(phenylselenenyl)methylidene(triphenyl)phosphorane with aliphatic and aromatic aldehydes. The α-phenylseleno unsaturated esters were obtained as mixtures of E/Z-isomers in medium to good yields and in moderate yields, respectively. α-Phenylselenenyl acrylate was used as dienophile in a Diels–Alder reaction. On reaction with isoprene only the para isomer was obtained while reaction with cyclopentadiene gave a 1:1 mixture of exo/endo isomers in good yield.