Journal of the Brazilian Chemical Society
versión impresa ISSN 0103-5053
PILLI, Ronaldo A. y RIATTO, Valéria B.. Stereoselective addition of chiral titanium enolates to 5-substituted five-membered oxocarbenium ions. J. Braz. Chem. Soc. [online]. 2008, vol.19, n.3, pp. 583-599. ISSN 0103-5053. http://dx.doi.org/10.1590/S0103-50532008000300030.
The sterochemical outcome of the addition of chiral titanium enolates to g-lactols derived from (S)-glutamic acid were examined. When 5-substituted g-lactols were treated with chiral titanium enolates of N-acetyl-, N-propionyl-, N-bromoacetyl- and N-phenylacetyl oxazolidin-2-ones, only two diastereoisomers were obtained, revealing complete facial control by the chiral titanium enolate while the oxocarbenium ion facial discrimination was dependent on the nature of the enolate R3 substituent. After desilylation with aqueous HF/CH3CN, LiBH4 reduction allowed the efficient preparation of the corresponding trans-2,5-disubstituted tetrahydrofuran diols and recovery of the chiral auxiliary.
Palabras llave : oxocarbenium ions; chiral titanium enolates; trans-2,5-disubstituted tetrahydrofurans.