Hyperconjugative Interactions in Bicyclo[2.2.1]heptane Derivatives. Effects on the Diels-Alder Reactivity of the s-cis-Butadiene Group of 2, 3-Dimethylidene-norbornanes

✍ Scribed by Michèle Hardy; Pierre-Alain Carrupt; Pierre Vogel

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: German
• Weight: 859 KB
• Volume: 59
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19760590529

✦ Synopsis

Abstract

Chemical and spectroscopic properties of the s‐cis‐butadiene chromophore in 2, 3‐dimethylidene‐norbornane can be modified without direct substitution of the diene moiety. Introduction of an etheral bridge for the H~2~C(7) bridge (2, 4, 6) and/or introduction of a double bond (5, 6) or of an exo‐epoxide ring (3,4) for the H~2~C(5)–H~2~C(6) bridge causes rate decreases in the Diels‐Alder cycloaddition with dimethyl acetylenedicarboxylate. The differences of reactivity observed between the dienes 1–6 are briefly discussed. Variation of the ability of the puckered cyclopentane ring of the bicyclo[2.2.1]heptane skeleton to hyperconjugate with the adjacent π‐system is offered as a possible rationalization of the electronic effects.