The nickel-catalyzed double carboxylation of internal alkynes employing carbon dioxide (CO2) has been developed. The reactions proceed under CO2 (1 atm) at room temperature in the presence of a nickel catalyst, Zn powder as a reducing reagent, and MgBr2 as an indispensable additive. Various internal alkynes could be converted to the corresponding maleic anhydrides in good to high yields. DFT calculations disclosed the indispensable role of MgBr2 in the second CO2 insertion.

A helium plasma is produced by electron-cyclotron resonance heating in a cusp-configuration magnetic field. Several neutral helium lines are found polarized in the direction perpendicular to the magnetic field; the maximum polarization degree exceeds 10%. The polarization degree and intensity of the emission lines yield, respectively, the alignment and population of the upper levels. The population-alignment collisional-radiative model is developed, and the experimental result is interpreted in terms of an anisotropic electron velocity distribution; it is of a Saturn-type with the central thermal component of 14 eV and the 'ring' component displaced by 9.2 eV from the central component. The relative number of 'ring' electrons is 40%.

Nickel-Catalyzed Double Carboxylation of Alkynes Employing Carbon Dioxide.-The Ni-catalyzed double carboxylation of internal alkynes with CO 2, affording highly versatile maleic anhydrides as products is reported. The reactions proceed selectively under CO 2 at 1 atm and room temperature in the presence of Zn powder as a reducing reagent and MgBr 2 as an indispensable additive. The key to the success of the present reaction is the generation of the Ni (I) metallacycle intermediate and the participation of MgBr 2 in facilitating the second carboxylation. It should be noted that the crucial roles of MgBr2 in the one-electron reduction and the second CO2 insertion into the Ni(I)-C bond are firstly recognized. -(FUJIHARA, T.; HORIMOTO, Y.; MIZOE, T.; SAYYED, F. B.; TANI, Y.; TERAO, J.; SAKAKI, S.; TSUJI*, Y.; Org. Lett. 16 (2014) 18, 4960-4963, http://dx.