Possibility of [1,5] Sigmatropic Shifts in Bicyclo[4.2.0]octa-2,4-dienes

The thermal equilibration of the methyl esters of endiandric acids D and E was subject to a computational study. An electrocyclic pathway via an electrocyclic ring opening followed by a ring flip and a subsequent electrocyclization proposed by Nicolaou [ Nicolaou K. C. ; Chen J. S. Chem. Soc. Rev. 2...

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Published inJournal of organic chemistry Vol. 80; no. 5; pp. 2609 - 2620
Main Authors Goossens, Hannelore, Winne, Johan M, Wouters, Sebastian, Hermosilla, Laura, De Clercq, Pierre J, Waroquier, Michel, Van Speybroeck, Veronique, Catak, Saron
Format Journal Article
LanguageEnglish
Published WASHINGTON American Chemical Society 06.03.2015
Amer Chemical Soc
Subjects
Alkenes - chemistry
Bridged Bicyclo Compounds - chemistry
Chemistry
Chemistry, Organic
esters
Molecular Structure
organic chemistry
Physical Sciences
Science & Technology
temperature
Thermodynamics
DENSITY FUNCTIONALS
ORGANIC-SYNTHESIS
MOLECULAR-ORBITAL METHODS
STEREOCONTROLLED TOTAL-SYNTHESIS
DIELS-ALDER REACTION
AB-INITIO
PERICYCLIC-REACTIONS
ENDIANDRIC ACID CASCADE
WALK REARRANGEMENT
2ND-ORDER PERTURBATION-THEORY
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Summary:The thermal equilibration of the methyl esters of endiandric acids D and E was subject to a computational study. An electrocyclic pathway via an electrocyclic ring opening followed by a ring flip and a subsequent electrocyclization proposed by Nicolaou [ Nicolaou K. C. ; Chen J. S. Chem. Soc. Rev. 2009, 38, 2993 ], was computationally explored. The free-energy barrier for this electrocyclic route was shown to be very close to the bicyclo[4.2.0]octa-2,4-diene reported by Huisgen [ Huisgen R. ; Boche G. ; Dahmen A. ; Hechtl W. Tetrahedron Lett. 1968, 5215 ]. Furthermore, the possibility of a [1,5] sigmatropic alkyl group shift of bicyclo[4.2.0]octa-2,4-diene systems at high temperatures was explored in a combined computational and experimental study. Calculated reaction barriers for an open-shell singlet biradical-mediated stepwise [1,5] sigmatropic alkyl group shift were shown to be comparable with the reaction barriers for the bicyclo[4.1.0]hepta-2,4-diene (norcaradiene) walk rearrangement. However, the stepwise sigmatropic pathway is suggested to only be feasible for appropriately substituted compounds. Experiments conducted on a deuterated analogous diol derivative confirmed the calculated (large) differences in barriers between electrocyclic and sigmatropic pathways.
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ISSN:0022-3263
1520-6904
1520-6904
DOI:10.1021/jo5027639