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|Type:||Artigo de periódico|
|Title:||Concerning The Application Of The1h Nmr Abx Analysis For Assignment Of Stereochemistry To Aldols Deriving From Aldehydes Lacking β-branches|
Salles Jr. A.G.
|Abstract:||Attempts to apply the 1H NMR ABX method for assignment of stereochemistry of β-hydroxy ketones to aldols 4-10 deriving from α-methyl aldehydes lacking β-branches reveals that the presence of a β-branch in the aldehyde reaction partner is necessary so that the average chemical environment of Ha and Hb is different for the Felkin and anti-Felkin aldols (see conformational pairs A/B and C/D, respectively). When the chiral α-methyl aldehyde lacks a β-branch, as in the case of the aldehyde precursors to 4-10, the conformational energies of E and F (for the Felkin β-hydroxy ketone derivatives), and conformers G and H for the anti-Felkin aldols, are too close in energy (within each pair), such that the average chemical and magnetic environments of Ha and Hb in the two diastereomers cannot be easily distinguished. This analysis provides a rational basis for application of the 1H NMR ABX pattern analysis to other β-hydroxy ketone derivatives. © 2005 American Chemical Society.|
|Citation:||Journal Of Organic Chemistry. , v. 70, n. 25, p. 10461 - 10465, 2005.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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