Efficient palladium catalyzed bis-alkoxycarbonylation of olefins for the synthesis of useful succinic acid derivatives

Succinic acid is an important intermediate for the production of commodity chemicals and the world market potential of its derivatives is estimated to be around 270.000 t/year. Above all, succinates find applications in various industrial fields, such as cosmetics, agricultural chemistry, food industry and material science. In this context, based on our knowledge on the carbonylation reactions of unsaturated substrates, we have recently developed an efficient, low-cost and one-pot methodology for the synthesis of succinic acid derivatives. In particular, we were able to carry out the bis-alkoxycarbonylation of olefins using palladium/aryl ?-diimine complexes as catalysts, obtaining succinates in high yields and selectivities, under mild reaction conditions. The reaction proceeds utilizing p-benzoquinone as oxidant and p-TSA as additive, in the presence of an alcohol, which acts both as a solvent and as nucleophile, under 4 bar of carbon monoxide at 20°C. The most active catalysts are easily formed in situ by mixing Pd(TFA)2 and the nitrogen ligands 1a or 1b, in THF. This process has also been successfully applied to particularly low-reactive olefins, such as 1,2-disubstituted olefins,[3] including unsaturated fatty acid methyl esters, or acrylic esters and acrylic amides. Interestingly, when internal olefins are utilized, the process turned out to be diastereospecific and no Pd-catalyzed isomerization of the double bond has been observed. Our studies, in addition to providing a complete library of succinates, allowed us to highlight some relevant aspects of the catalytic cycle of the bis-alkoxycarbonylation reaction, through mechanistic investigations carried out with ab-initio calculations. Here, our latest results on the bis-alkoxycarbonylation process will be presented.