Intramolecular Hetero‐Diels–Alder Reactions of Oxadienes: Influence of Substituents of the Tether on the Diastereoselectivity

Abstract

How do substituents on the chain of 1 influence the stereosclectivity of the intramolecular hetero-Diels-Alder reaction? This question was followed up by exact analysis of the product composition of the reactions of 1 a and its methyl analogues 1 b–e with 2 to give 3a–e. It emerged that “steric” and “conformational” effects in the chair-shaped transition structure must be differentiated and that the equatorial position of the methyl group is more strongly favored in the transition structures leading to 3c, d than in methylcyclohexane. R = H (a), α-Me (b), β-Me (c), γ-Me (d), δ-Me (e).