Victor Mark

Integrity of alkene stereochemistry in the Diels—Alder reaction

Abstract The Diels—Alder reaction of hexachlorocyclopentadiene and α-methylstyrene produces both exo -phenyl and endo -phenyl adducts, with the latter in preponderance. A deuterium label at the β position of the alkene provides a probe for determining whether the vicinal stereochemical relationship between groups on the alkene is retained in the adducts. From the alkene labeled 77.6±2.3% E and 22.4±2.3% Z was produced the major ( endo -phenyl) isomer with 79.4±1.1% exo-d and 20.6±1.1% endo-d and the minor ( exo -phenyl) isomer with 78.9±0.5% endo-d and 21.1±0.5% exo-d . Thus both adducts are produced with complete retention of alkene stereochemistry.