Oxycarbonylation palladium catalysts

Another alternative method to produce sebacic acid iavolves a four-step process. First, butadiene [106-99-0] is oxycarbonylated to methyl pentadienoate which is then dimerized, usiag a palladium catalyst, to give a triply unsaturated dimethyl sebacate iatermediate. This unsaturated iatermediate is hydrogenated to dimethyl sebacate which can be hydrolyzed to sebacic acid. Small amounts of branched chain isomers are removed through solvent crystallizations giving sebacic acid purities of greater than 98% (66). 

Pi-A -chloro-di- -(dimethyl hex-2 endioate) di-palladium is the preferred palladium catalyst and was used in the pilot plant studies outlined in Table II. Synthesis is easily accomplished by reaction of dimethyl hex- -endioate with palladium chloride. In actual butadiene oxycarbonylation runs catalyzed... 

The oxycarbonylation of phenol in the presence of a palladium catalyst, a tertiary amine and a manganese cocatalyst at room temperature and atmospheric pressure results in the formation of diphenyl carbonate in good yield (equation 184).453... 

CO, and methanol react in the first step in the presence of cobalt carbonyl catalyst and pyridine [110-86-1] to produce methyl pentenoates. A similar second step, but at lower pressure and higher temperature with rhodium catalyst, produces dimethyl adipate [627-93-0]. This is then hydrolyzed to give adipic acid and methanol (135), which is recovered for recycle. Many variations to this basic process exist. Examples are ARCO s palladium/copper-catalyzed oxycarbonylation process (136—138), and Monsanto s palladium and quinone [106-51-4] process, which uses oxygen to reoxidize the by-product... 

After ARCO patents issued, Stille and coworkers published on butadiene oxycarbonylation(14-16). Palladium was utilized as the oxidative carbonylation catalyst and copper(II) chloride was employed as a stoichiometric reoxidation agent for palladium. Although the desired hex-3 -enedioate is the exclusive product, commercial technology which uses stoichiometric copper is not practical. Once the copper(Il) is consumed, the monoatomic palladium spent catalyst agglomerates affording polymeric palladium which is not easily reoxidized to an active form. 

The adipic acid process we have developed involves butadiene oxidative carbonylation in the presence of methanol, a l, l-dimethoxycyclohexane dehydration agent, and a palladium(ll)/ copper(ll) redox catalyst system (Equation 1.). The reaction sequence includes an oxycarbonylation, hydrogenation and hydrolysis step(17-19). The net result is utilization of butadiene, the elements of synthesis gas, l, -dimethoxycyclohexane and air to give adipic acid, cyclohexanone and methanol. 

The catalytic oxycarbonylation of benzene and naphthalene to benzoic or naphthoic acid in the presence of Wacker-type catalysts has been reported in several patents,376,448 but difficulties in reoxidizing the reduced palladium have inhibited industrial use of this chemistry. 

Recently, Kapitan and Gracza and co-workers have disclosed further oxycarbonylative annulations of unsaturated polyols, either diastereoselective or enantioselective, using chiral palladium(II) complexes. In their initial report, the method was investigated for the kinetic resolution of pent-4-ene-l,3-diols 97 through their asymmetric oxycarbonylative bicyclization and a conversion controlled by the amount of benzoquinone. Besides the chiral ligand, the efficiency depends on the anionic part of the catalyst and the solvent. Under optimum conditions, the lactone 98a was isolated in 29% yield and 62% ee. Similarly, the iyK-diols ( )-97b and ( )-97c provided the corresponding natural... 

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