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We describe the nickel-catalyzed hydrocarboxylation of ynamides with CO 2 and H 2 O to afford a variety of α-amino-α,β-unsaturated esters with high regioselectivities. Selective α-carboxylation of ynamide with this catalytic protocol is unexpected in view of the electronic bias of ynamide and is in sharp contrast to our previous study in which a stoichiometric amount of Ni(0) was used to form a β-carboxylated product exclusively. We revealed that this unexpected C−C bond formation was induced by the combination of Zn and MgBr 2 .Homogeneous nickel catalysis has emerged in the past few decades as a highly efficient tool for organic synthesis.1 The intrinsic chemical properties of some nickel catalysts to construct a C−C bond have been applied to incorporation of CO 2 , which is an abundant, non-toxic and renewable carbon source. 2 Especially, reactions using compounds bearing a C−C double bond or triple bond as a coupling partner of CO 2 enable transformation of these building blocks into carboxylic acid derivatives without prefunctionalization such as halogenation or metalation. [3][4][5] Since all carbons constituting an unsaturated bond are potentially reactive, controlling the regioselectivity is a common concern of these promising reactions employing CO 2 . Recently, Martin's group has developed regioselective hydrocarboxylation of alkyl aryl acetylenes with CO 2 employing alcohol as a proton source. 4f They speculated that an equilibrium would exist between two possible nickelalactones derived from alkyne and CO 2 and that steric repulsion between an alkyl group and alcohol would be a key factor for preferential formation of carboxylic acid A behind B (Scheme 1). Their proposed mechanism let us assume another strategy for nickel-catalyzed regioselective hydrocarboxylation of a C−C triple bond with CO 2 in which the selectivity would be engendered by taking advantage of an electronic factor. Herein, we report a nickel-catalyzed regioselective hydrocarboxylation of ynamide, which is known to have an electronic bias on the C−C triple bond, by use of H 2 O and CO 2 .6 Consequently, we observed an interesting selectivity switching triggered by additives. Scheme 2. Our previous work: Nickel-mediated hydrocarboxylation of ynamide with CO2We previously described a nickel-mediated regioselective synthesis of functionalized β-amino-α,β-unsaturated esters from ynamides 1 and CO 2 .7 The selectivity was controlled by a regioselective oxidative cyclization step in which a negative β-carbon of an ynamide forms a C−C bond with CO 2 on Ni(0) (Scheme 2). The resulting β-carboxylated products were shown to be precursors of enantio-enriched β-amino acid derivatives by conducting Rh-catalyzed asymmetric hydrogenation. As a next step, we commenced to develop a regioselective catalytic hydrocarboxylation of ynamides. Recently, Sakaki and Tsuji et al. reported a nickel-catalyzed double carboxylation of alkyne by the use of CO 2 in the presence of Zn/MgBr 2 as reducing agents. 4g We applied their reaction conditions to catalytic ...

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CO 2 electrochemical reduction (CO 2 ER) activity is known to be influenced by electrode materials. In this study, we report the fabrication of a copper-nickel-modified boron-doped diamond (CuNi-BDD) electrode using wet chemical seeding and electrodeposition. Annealing was performed to improve the stability of the modified electrode during electrolysis. Characterization of the modified BDD electrodes shows successful deposition without damage to the surface of the BDD support material. CO 2 ER was conducted with the CuNi-BDD electrode, which produces various important products including methanol, formic acid, CO, and CH 4 . Additionally, a different applied potential affected the product distribution. CO 2 ER was also conducted on the surfaces of Cu-BDD and Ni-BDD electrodes for comparison.