Cerium (IV) ammonium nitrate as an efficient catalyst for oxidation of alkyl malonates into ketomalonates by dioxygen

Abstract

The synthesis of diethyl ketomalonate via direct oxidation of diethyl malonate by pure oxygen or even using air, in the presence of cerium ammonium nitrate (CAN) used in catalytic amount is reported. The efficiency of this new catalytic system toward this reaction is compared to the previously described Co III-Mn III catalyst. Thus, when (NH 4) 2Ce(NO 3) 6 was used, oxidation occurred in acetic acid-acetonitrile medium ( 1 1 v/v) under oxygen flow at moderate temperature (50–70°C) and with excellent selectivity (> 90%). In contrast, the Co Mn catalyst required higher temperature (80–120°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 substrate is degraded into CO 2 and H 2O. Moreover, with CAN system, an appreciable yield could be obtained under air flow (or even only by stirring under air) whilst with Co Mn , under the same conditions, the conversion was very low. Finally the separation of CAN from reaction products and solvents at the end of the reaction and its reuse could be facilitated by coating CAN on porous silica. This supported CAN SiO 2 system exhibited in its first use the same activity as free CAN and in its second use about 70% of the initial value.