Protonação diastereosseletiva de alquil-aril cetenos na síntese de intermediários para a preparação de piretróides

Abstract

The increasing knowledge about the chemistry of synthetic pyrethroids resulted in the development of new, more selective, more effectives insecticides, which are inparallel less harmful to the environment. One know compound is esfenvalerate, which had strong impact on the coming up of modern insecticides. The activity of these molecules depends on asymmetric centers with defined configurations. In this work a synthetic route for the preparation of potent precursor for pyrethroids, the 2-(4'- chlorophenyl)-3-methylbutirate pantolactonyl ester via diastereoselective addition of R-(-)-pantolactone to phenylisopropylketene is presented (diastereoisomeric ratio 70:30). Studies to examine factors wich have influence on the stereoselectivity of this reactions have been performed. The aim of the preparation of these derivates was to open the possibility to use this route for the application in the synthesis for interesting biological molecules like the preparation of esfenvalerate analogous.