Iodine-catalysed stereomutation of chiral 1,4-dialkylbutadienes

Abstract

The iodine-catalysed (Z)–(E)-stereomutation of some optically active 1,4-dialkylbutadienes has been studied in heptane between 25 and 60 °C. The isomerisation rate depends on the substituents of the diene moiety. When it occurs, the isomerisation of (E,Z)- and (E,E)-dienes is reversible under the experimental conditions adopted, whereas (Z,Z)-dienes do not isomerise at all. The stereomutation of (E,Z)-(3S,8S)-3,8-dimethyldeca-4,6-diene to the corresponding (E,E)-isomer occurs without racemisation of the chiral centres and follows first-order kinetics. The data obtained are discussed briefly in the light of the mechanisms generally accepted.