Bis-Alkoxycarbonylation of Acrylic Esters and Amides for the Synthesis of 2-Alkoxycarbonyl or 2-Carbamoyl Succinates

The first example of the bis-alkoxycarbonylation of acrylic esters and acrylic amides, leading to differently substituted 1,1,2-ethanetricarboxylate compounds and 2-carbamoylsuccinates respectively, is reported. The catalyst is formed in situ by mixing Pd(TFA)2 (TFA=trifluoroacetate) and the ligand bis(2,6-dimethylphenyl)butane-2,3-diimine. The reaction, that proceeds using p-benzoquinone as oxidant and p-toluenesulfonic acid as additive, has been applied to variously substituted electron-poor alkenes, employing different alcohols as nucleophiles, under very mild reaction conditions (4 bar of carbon monoxide at 20 °C). Remarkably, this catalytic system is able to promote the carbonylation of both the β- and the generally unreactive α-positions of acrylic esters and amides, allowing the formation of bis-alkoxycarbonylated products in good to excellent yields (up to 98%). The trend of reactivity, observed with the different electron-deficient olefins, has been rationalized on the basis of the proposed catalytic cycle and DFT calculations.