Origin of the “endo rule” in Diels–Alder reactions |
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| Authors: | Israel Fernández F Matthias Bickelhaupt |
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| Affiliation: | 1. Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, Madrid, Spain;2. Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, and Institute for Molecules and Materials (IMM), Radboud University Nijmegen, The Netherlands |
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| Abstract: | 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. |
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| Keywords: | activation strain model cycloaddition Diels Alder reaction endo rule density functional theory calculations reactivity |
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