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Origin of the “endo rule” in Diels–Alder reactions
Author(s) -
Fernández Israel,
Bickelhaupt F. Matthias
Publication year - 2013
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.23500
Subject(s) - cyclopentadiene , maleic anhydride , steric effects , selectivity , chemistry , diels–alder reaction , transition state , density functional theory , computational chemistry , stereochemistry , organic chemistry , polymer , catalysis , copolymer
Detailed density functional theory calculations definitively rationalize the preference for the endo cycloadduct (also known as endo rule) in text‐book thermal Diels–Alder reactions involving maleic anhydride and cyclopentadiene or butadiene. This selectivity is mainly caused by an unfavorable steric arrangement in the transition‐state region of the exo pathway which translates into a more destabilizing activation strain. In contrast with the widely accepted, orbital‐interaction‐based explanation for the endo rule, it is found that neither the orbital interactions nor the total interaction between the deformed reactants contributes to the endo selectivity. © 2013 Wiley Periodicals, Inc.