Resumo

MORALES-NAVA, Rosmarbel; RAMIREZ-SOLIS, Alejandro  e  FERNANDEZ-ZERTUCHE, Mario. NMR and Theoretical Studies on the Conformational Preferences of Some Non-metal Coordinated N-Enoyl Systems Attached to Common Chiral Auxilaries. J. Mex. Chem. Soc [online]. 2014, vol.58, n.2, pp.89-94. ISSN 1870-249X.

We report a systematic study of a series of N-enoyl systems attached to common oxazolidin-2-ones, oxazolidine-2-thiones and thiazolidine-2-thiones chiral auxiliaries in order to determine the most stable conformation of these compounds. ¹H NMR studies show an anti-s-cis structure as the most stable conformation for these series of compounds. Density Functional Theory geometry optimizations and vibrational analysis using the B3LYP exchange-correlation functional with the standard 6-31G** basis sets were done, including solvent effects (chloroform and toluene). Gibbs free energy differences show that the anti-s-cis structures are the most stable conformers lying, on average, ca. 6 kcal/mol lower in energy than the syn-s-cis conformers, widely used to explain the structure and reactivity of N-enoyl systems.

Palavras-chave : Enoyl systems; conformational preferences; chiral auxiliaries; NMR shifts.

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