Use of chiral alfa-oxigenated aldehydes in the Morita-Baylis-Hillman reaction : studies toward the optmization of reaction conditions and synthesis of bioactive compounds / Uso de aldeidos quirais alfa-oxigenados na reação de Morita-Baylis-Hillman : estudos visando otimização das condições reacionais e sintese de compostos bioativos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In this work, we describe the utilization of ultrasound and ionic liquid in Morita-Baylis-Hillman reactions, with chiral aldehydes bearing oxygen at the a-carbonyl position. Due to the long reaction times normally observed in the Morita-Baylis-Hillman reaction, a-oxigenated chiral aldehydes can be racemized in the reaction, directly impacting on the diastereoselectivity of the reaction. Ultrasound as well as ionic liquid drastically accelerated the reaction rate with several aldehydes, in comparison to data described earlier in the literature. The a-carbonyl oxygen was protected with different protecting groups and the correct choice of these groups was important for the success of the reaction. Sugar derived aldehydes were efficient substrates in the reaction, leading to the formation of adducts with good diastereoisomeric excesses in some cases. Interestingly, the association of ultrasound and ionic liquid led to a lower yield, which can be related with the destruction of the well defined supramolecular structure of the ionic liquid on the presence of ultrasound radiation. This hypothesis was reinforced after carrying out some reaction using the same association (ultrasound + ionic liquid) at 0º C. Under this experimental conditions we observed an excellent yield with short reaction time. Searching to map the influence of each one of these factors (ultrasound, ionic liquid and temperature) in the Morita-Baylis-Hillman reaction, a chemometric study was carried out varying simultaneously these three factors. The utilization of ionic liquid at 0º C, as much as in the ultrasound presence as under agitation, was the best condition to the Morita-Baylis-Hillman reaction. In this way, several aliphatic and aromatic aldehydes were tested utilizing this condition, conducting to good results, in some cases superior to those already described in the literature. Finally, an alfa-methylene-gamma-butyrolactone was prepared, which has a potent biological activity. Studies toward the preparation of polyoxamic acid and the miriocin polar fragment were also realized in this work.

ASSUNTO(S)

ultrasonografia morita-baylis-hillman diastereoselectivity ultrasound liquido ionico ionic liquid diastereosseletividade

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