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

michel — Sun, 30 Nov 2014 13:27:40 +0000

H. Goossens, J.M. Winne, S. Wouters, L. Hermosilla, P. J. De Clercq, M. Waroquier, V. Van Speybroeck, S. Catak

Journal of Organic Chemistry

80 (5) 2609-2620

2015

Abstract

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 [Chem. Soc. Rev. 2009], 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 [Tet. Lett. 1968]. 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 a 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, whereas calculated reaction barriers for a concerted [1,5] sigmatropic alkyl group shift were found to be higher in energy. However, the stepwise 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.

DOI

http://dx.doi.org/10.1021/jo5027639

Private attachment

15_JOC_xxxx_HGoossens.pdf

Thermal Equilibration of Endiandric Acids and the [1,5] Sigmatropic Shift in Bicyclo[4.2.0]octa-2,4-dienes

lore — Wed, 07 Jan 2015 11:28:19 +0000

H. Goossens, J. Winne, S. Wouters, P. J. De Clercq, M. Waroquier, V. Van Speybroeck, S. Catak

ISBN/ISSN:

Talk

Conference / event / venue

MOLCHEM2014

Istanbul, Turkey

Friday, 19 December, 2014

Abstract (private)

MOLCHEM2014-Saron Catak-1.pdf

Center for Molecular Modeling - P. J. De Clercq