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Highly diastereoselective hydrogenations leading to ß-hydroxy ∂-lactones in hydroxy-protected form. A modified view of ∂-lactone conformations.

Brandänge, S; Färnbäck, M; Leijonmarck, H and Sundin, Anders LU (2003) In Journal of the American Chemical Society 125(39). p.11942-11955
Abstract
Enol MEM ethers 4 and 15 and the corresponding enol acetates were hydrogenated over Pd/C with very high (>99%) diastereoselectivity to saturated -lactones. A stereochemical generalization can be formulated thus: trans-5,6-disubstituted 1-oxa-3-cyclohexen-2-ones (e.g. 14 and 15) are hydrogenated over Pd with high selectivity from the side trans to the C(6)-substituent. A mechanistic rationalization of the stereochemical outcome in the Pd-catalyzed hydrogenation of this as well as other types of substituted ,-unsaturated -lactones is presented. An analysis of X-ray crystallographic data for 67 compounds demonstrated a great conformational diversity of the saturated -lactone ring. Besides, ab initio calculations (HF/6-31G*) indicated a... (More)
Enol MEM ethers 4 and 15 and the corresponding enol acetates were hydrogenated over Pd/C with very high (>99%) diastereoselectivity to saturated -lactones. A stereochemical generalization can be formulated thus: trans-5,6-disubstituted 1-oxa-3-cyclohexen-2-ones (e.g. 14 and 15) are hydrogenated over Pd with high selectivity from the side trans to the C(6)-substituent. A mechanistic rationalization of the stereochemical outcome in the Pd-catalyzed hydrogenation of this as well as other types of substituted ,-unsaturated -lactones is presented. An analysis of X-ray crystallographic data for 67 compounds demonstrated a great conformational diversity of the saturated -lactone ring. Besides, ab initio calculations (HF/6-31G*) indicated a very high conformational mobility. Thus, the lowest calculated transition state for the conversion of the half-chair, most stable, conformer of -valerolactone to the boat-type conformer lies only 1.93 kcal/mol above the former. Beside these two conformers, also chair, envelope and skew conformations are accessible; all lie less than 2 kcal/mol above the half-chair. The previous conformational paradigm comprising only boat and half-chair types is incomplete (Less)
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Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
125
issue
39
pages
11942 - 11955
publisher
The American Chemical Society
external identifiers
  • wos:000185578500045
  • scopus:0141508976
ISSN
1520-5126
DOI
language
English
LU publication?
yes
id
854a06dd-0b73-43c7-b00b-7d3ff77e8194 (old id 127912)
date added to LUP
2007-07-10 09:24:18
date last changed
2018-05-29 11:25:19
@article{854a06dd-0b73-43c7-b00b-7d3ff77e8194,
  abstract     = {Enol MEM ethers 4 and 15 and the corresponding enol acetates were hydrogenated over Pd/C with very high (>99%) diastereoselectivity to saturated -lactones. A stereochemical generalization can be formulated thus: trans-5,6-disubstituted 1-oxa-3-cyclohexen-2-ones (e.g. 14 and 15) are hydrogenated over Pd with high selectivity from the side trans to the C(6)-substituent. A mechanistic rationalization of the stereochemical outcome in the Pd-catalyzed hydrogenation of this as well as other types of substituted ,-unsaturated -lactones is presented. An analysis of X-ray crystallographic data for 67 compounds demonstrated a great conformational diversity of the saturated -lactone ring. Besides, ab initio calculations (HF/6-31G*) indicated a very high conformational mobility. Thus, the lowest calculated transition state for the conversion of the half-chair, most stable, conformer of -valerolactone to the boat-type conformer lies only 1.93 kcal/mol above the former. Beside these two conformers, also chair, envelope and skew conformations are accessible; all lie less than 2 kcal/mol above the half-chair. The previous conformational paradigm comprising only boat and half-chair types is incomplete},
  author       = {Brandänge, S and Färnbäck, M and Leijonmarck, H and Sundin, Anders},
  issn         = {1520-5126},
  language     = {eng},
  number       = {39},
  pages        = {11942--11955},
  publisher    = {The American Chemical Society},
  series       = {Journal of the American Chemical Society},
  title        = {Highly diastereoselective hydrogenations leading to ß-hydroxy ∂-lactones in hydroxy-protected form. A modified view of ∂-lactone conformations.},
  url          = {http://dx.doi.org/},
  volume       = {125},
  year         = {2003},
}