Abstract
The reaction of acrolein with ethanol yielded ethyl acrylate (EA), propionaldehyde diethyl-acetal (PAEt2), acrolein diethylacetal (AcEt2), β-ethoxypropionaldehyde (EP) and its acetal (AcEt3) in the presence of complexes such as RuCl2 (C12H18), RuCl3·3H2O, [RhGl (C8H14) 2] 2, [RhCl (C2H4) 2] 2, RhCl (PPh3) 3 and IrCl (CO) (PPh3) 2. Among them, RuCl2 (C12H18) was the most effective catalyst for the formation of EA, but the yield of which was ca. 10%. Ethyl propionate as well as EA was formed with increase of the reaction temperature. The presence of oxygen in the reaction catalyzed by RuCl2 (C12H18) increased the yields of the products.
In these reactions, the yields of EA, PAEt2, EP and AcEt3 increased gradually, while the yield of AcEt2 at first increased and then levelled down. These results indicated the following reaction scheme :
On the other hand, the formation of EA proceeded through an acyl-type complex formed by the oxidative addition of acrolein to the metals, followed by the attack of ethanol. Hydrogen atoms formed in this reaction might be transferred to acrolein to give PAEt2 by the reaction with ethanol.
Use of propionaldehyde in place of acrolein afforded ethyl propionate, but its yield was very low as compared with that of EA derived from acrolein.
