AplicaÃÃes de reagentes quirais de enxofre em catÃlise assimÃtrica e na sÃntese estereosseletiva de cetonas cÃclicas substituÃdas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

This thesis describes the development of new methodologies for the use of chiral sulfur compounds, exploring their ability to transfer chiral information. The first methodology was based on the stereoselective transfer of ligands to α,β- unsaturated ketones mediated by organocuprates in a Michael addition reaction using (SR)- methyl-p-tolyl-sulfoxide as a non-transferable ligand. The addition reaction, however, is not stereoselective. The second part describes the enantioselective addition of allylzinc bromide to aldehydes catalyzed by chiral sulfur compounds acting as Lewis bases. Several parameters like the amount of catalyst, temperature, and solvent were studied. The homoallylic alcohols were obtained in good yields, but in modest enantiomeric excesses. The last part of this thesis describes the study of the addition of aryl groups to (SR)-4- hydroxy-4-[(p-tolylsulfinyl)methyl]-2,5-cyclohexanedione. The 1,4 addition products were obtained in excellent diastereomeric excesses when aryl groups were used in the addition reactions to p-quinol. The methodology was also applied for the stereoselective synthesis of substituted aryl-cyclohexanones and aryl-cyclohexenones, units present in the skeleton of several natural products such as the constituents of Amaryllidaceae family The strategy used was very versatile, once the cyclohexanone derivates were obtained in good yields and good diastereomeric excesses

ASSUNTO(S)

asymmetric catalysis catÃlise assimÃtrica sÃntese estereosseletiva reagentes quirais de enxofre chiral sulfur compounds quimica organica stereoselective synthesis

ACESSO AO ARTIGO

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