Journal article

Publication year: 2009

Pages: 13387-13398

Journal: Journal of the American Chemical Society

Volume number: 131

Issue number: 37

DOI Link: https://doi.org/10.1021/ja903914r

Publisher: American Chemical Society

Abstract: 
Unusual and novel polycyclic cyclooctatrienes, fenestradienes, and fenestrenes form readily from trienynes depending on the structure of the starting trienynes and the reaction conditions. The experimentally observed high torquoselectivities and complete diastereoselectivities ofthe 8π-electrocyclization products have been thoroughly studied using density functional computations at B3PW91/6-31G(d,p). The different P- and M-helicaltopologies for the Möbius aromatic transition structures are the originof the observed torquoselectivities in the cyclooctatrienes. The P-helical topologies direct the newly formed single bonds into a favorable equatorial position of the neighboring cycloalkane moieties (X = ring size) that retain their most stable conformation. The M-helical transition structures lead to an axial connection for the smaller rings (X = 4−6) and an equatorialconnection for the seven- and eight-membered cycloalkanes. This leads to unfavorable conformations for the larger cycloalkane moieties. Experiments and computations show that for trienynes involving small neighboring cycloalkane groups (X = 4−6) M-helical topology is preferred toward cyclooctatrienes and in the following the corresponding fenestradienes can be formed as kinetic or even thermodynamic products; they convert to their more stable cyclooctatriene valence isomers derived from P-helical transitionstructures at higher temperatures. For larger cycloalkane moieties withmore conformational flexibility only cyclooctatrienes with torquoselectivities derived from P-helical transition structures form.

Harvard Citation style: Hulot, C., Amiri, S., Blond, G., Schreiner, P. and Suffert, J. (2009) Understanding the Torquoselectivity in 8π-Electrocyclic Cascade Reactions: Synthesis of Fenestradienes versus Cyclooctatrienes, Journal of the American Chemical Society, 131(37), pp. 13387-13398. https://doi.org/10.1021/ja903914r

APA Citation style: Hulot, C., Amiri, S., Blond, G., Schreiner, P., & Suffert, J. (2009). Understanding the Torquoselectivity in 8π-Electrocyclic Cascade Reactions: Synthesis of Fenestradienes versus Cyclooctatrienes. Journal of the American Chemical Society. 131(37), 13387-13398. https://doi.org/10.1021/ja903914r