Synthesis of Dimethyl Malonate by Mean of Vapor-phase Carbonylation of Methyl Chloroacetate -Vapor-phase Carbonylation of Halogenated Organic Compounds. III.-

Abstract

The vapor-phase carbonylation of methyl chloroacetate (MCA) with carbon monoxide in the presence of methanol was carried out in order to investigate the catalysis of metal halide supAported on the carrier appropriate for the formation of dimethyl malonate (DMM).
Activated charcoal seemed to be suitable for the carrier with rhodium(III) chloride, while methyl methoxyacetate and methyl glycolate were formed in significant amounts on use of active aluminium oxide. The conversion of MCA into DMM increased with increasing th e surface area of activated charcoal with a few exceptions.
The metal chloride capable of forming carbonyl compo u nds was supported on the activated charcoal and was examined for the carbonylation of MCA into DMM. Cobalt(II) chloride, rhodium(III) chloride, palladium(II) chloride, iridium(III) chloride, iridium(IV) chloride and pulatinum(IV) chloride were found to be active for the carboylation. In particuler, rhodium(III) cuhoride was excellent in the reactivity and selectivity. The amount of methylacetate varied widely depending on metal chlorides supported on activated charcoal. It was not possible to suppose all methyl acetate is formed by the release of carbon dioxide from methylhydrogen malonate. It could be assumed that MCA reacted directly with methan ol to convert into methyl acetate and methyl chloride.
Among the rhodium compounds the electronegative substituent group bonded to the rhodiumcontributed to a increase in the reactivity. Metal iodies enhanced remarkably the reactivit of rhodium(III) chloride supported on activated charcoal . The reactivity of promoter was found in the following order : NaI>LiI>KI>BaI₂>CsI>CoI₂>RbI>CaI₂. It was reasonable to speculate that rhodium(III) chloride iodide might be formed by replacing the chlorine of rhodium(III) chloride with iodine partly and preferable to carbonylation of MCA into DMM.