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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
Author(s) -
Hardy Michèle,
Carrupt PierreAlain,
Vogel Pierre
Publication year - 1976
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19760590529
Subject(s) - chemistry , bicyclic molecule , norbornane , reactivity (psychology) , diene , moiety , cycloaddition , epoxide , stereochemistry , cyclopentane , medicinal chemistry , heptane , double bond , ring (chemistry) , organic chemistry , medicine , natural rubber , alternative medicine , pathology , catalysis
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.