A computational study of the Diels-Alder reaction of ethyl-S-lactyl acrylate and cyclopentadiene: Origins of stereoselectivity

Snezhana M. Bakalova, António Gil Santos

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

The eight diastereoisomeric transition structures of the Diels-Alder addition of ethyl-S-lactyl acrylate and cyclopentadiene have been investigated in the gas phase and in solution by HF, MP2, and density functional theory (B3LYP and B3PW91) methods with the 6-31G(d,p) basis set. At all levels of theory used, the s-cis transition structures are more stable than the s-trans ones. The contribution of the s-trans transition structures increases in solution and, although still small, has to be taken in consideration for correct prediction of stereoselectivity. Diastereofacial selectivity is interpreted in terms of electrostatic (weak hydrogen bonding) C=O⋯H(C) interactions between the carbonyl group(s) of the dienophile and cyclopentadiene in the energetically favored transition structures. Endo/exo reaction selectivity is attributed to positive orbital interactions between the diene and the acrylate carbonyl oxygen in the endo s-cis transition structures. Ab initio methods reproduce well the experimentally observed trends in both endo/exo and diastereofacial selectivity. Density functional calculations in the gas phase correctly reproduce the observed trends in diastereofacial selectivity but single-point MP2 calculations are necessary to reproduce the experimental trend in endo/exo selectivity.

Original languageEnglish
Pages (from-to)8475-8481
Number of pages7
JournalJournal of Organic Chemistry
Volume69
Issue number24
DOIs
Publication statusPublished - 26 Nov 2004

Keywords

  • Carbonyls
  • Organic compounds
  • Selectivity
  • Mathematical methods
  • Stereoselectivity

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