Diastereofacial selectivity in Diels–Alder reactions of buta-1,3-dienes having stereogenic allylic heteroatom substituents at the C-2 position

Diels–Alder reactions of ten 2-substituted buta-1,3-dienes 1a–j with N-phenylmaleimide were examined under various conditions, demonstrating that an allylic heteroatom substiuent at the C-2 position exerts significant directing effect on diastereofacial selection and also that the diastereofacial selectivity can be enhanced by use of 5 mol dm–3 LiClO4–Et2O as a reaction medium.