CERIUM(IV) AMMONIUM-NITRATE AS AN EFFICIENT CATALYST FOR OXIDATION OFALKYL MALONATES INTO KETOMALONATES BY DIOXYGEN

The synthesis of diethyl ketomalonate via direct oxidation of diethyl malonate by pure oxygen or even using air, in the presence of cerium a mmonium nitrate (CAN) used in catalytic amount is reported. The effici ency of this new catalytic system toward this reaction is compared to the previously described Co-III-Mn-III catalyst. Thus, when (NH4)(2)Ce (NO3)(6) was used, oxidation occurred in acetic acid-acetonitrile medi um (1/1 v/v) under oxygen flow at moderate temperature (50-70 degrees C) and with excellent selectivity (>90%). In contrast, the Co/Mn catal yst required higher temperature (80-120 degrees C) and the selectivity for the desired product drastically decreased with conversion. Under the latter conditions, a great part of the reaction products and/or su bstrate is degraded into CO2 and H2O. Moreover, with CAN system, an ap preciable yield could be obtained under air flow (or even only by stir ring under air) whilst with Co/Mn, under the same conditions, the conv ersion was very low. Finally the separation of CAN from reaction produ cts and solvents at the end of the reaction and its reuse could be fac ilitated by coating CAN on porous silica. This supported CAN/SiO2 syst em exhibited in its first use the same activity as Gee CAN and in its second use about 70% of the initial value. (C) 1997 Elsevier Science B .V.