Abstract
(Chemical Equation Presented) The relative gas-phase energetics of several low-lying isomers of 1,7-dioxaspiro[5.5]undecane and 1,7,9-trioxadispiro[5.1.5. 3]hexadecane have been calculated with second-order Møller-Plesset perturbation theory and basis sets as large as aug-cc-pVQZ. Relative energies in THF, dichloromethane, acetone, and DMSO have been estimated with corrections from polarized continuum model calculations at the B3LYP/6-311+G(d) level. In the most stable conformation of 1,7-dioxaspiro[5.5]undecane, both rings adopt chair conformations, and both oxygens are axially disposed (2A). It is more than 2 kcal mol-1 more stable than all the other conformers. In agreement with previous work, the "twist-boat" trans isomer (3A) is the most stable isomer of 1,7,9-trioxadispiro[5.1.5.3]hexadecane. However, in contrast to this earlier study, an "all-chair" conformation (3B) is found to be the most stable cis isomer of 1,7,9-trioxadispiro[5.1.5.3]hexadecane (ΔE ≈ 0.5 kcal mol-1 in acetone and DMSO). Gauge-independent atomic orbital computations at the B3LYP/6-311+G(d) level indicate that this is the only cis isomer with 13C NMR chemical shifts that are qualitatively consistent with the experimental spectra. © 2006 American Chemical Society.
Recommended Citation
A. J. Weldon and G. S. Tschumper, "Energetics of Oxaspirocycle Prototypes: 1,7-Dioxaspiro[5.5]undecane and 1,7,9-Trioxadispiro[5.1.5.3]hexadecane," Journal of Organic Chemistry, vol. 71, no. 24, pp. 9212 - 9216, American Chemical Society, Nov 2006.
The definitive version is available at https://doi.org/10.1021/jo061689e
Department(s)
Chemistry
International Standard Serial Number (ISSN)
0022-3263
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2024 American Chemical Society, All rights reserved.
Publication Date
24 Nov 2006
PubMed ID
17109550
