ALDOL CONDENSATIONS OVER LAYERED DOUBLE HYDROXIDES

This work focuses on utilization of layered double hydroxides for aldol condensation of campholenic aldehyde with propanal or butanal. The influence of reaction conditions (Mg: Al molar ratio and conditions of LDHs activation) on reaction course were studied in order to produce aldehydes 2-methyl-4-(2,2,3-trimethylcyclopent3- en-1-yl) but-2-enal and 2-ethyl-4-(2,2,3-trimethylcyclopent-3-en-1-yl) but-2-enal. Campholenic aldehyde was prepared by alpha-pinene oxide isomerization with ZnBr2 (total conversion, 89% selectivity to campholenic aldehyde, 70 degrees C, toluene). Layered double hydroxides (LDHs) with Mg: Al molar ratio ranging 2: 1 - 3 : 1 were characterized by various techniques (AAS, XRF). It was found, that catalysts were inactive in campholenic aldehyde and propanal (butanal) condensation under tested reaction conditions. Only auto-condensation products of propanal and butanal occurred in the reaction mixture (up to 79%).