Cobalt-Catalyzed Formal [4+2] Cycloaddition of α,α′-Dichloro-<i>ortho</i>-Xylenes with Alkynes
作者:Kimihiro Komeyama、Yuji Okamoto、Ken Takaki
DOI:10.1002/anie.201406807
日期:2014.10.13
A formal [4+2] cycloaddition of α,α′‐dichloro‐ortho‐xylenes with various alkynes has been developed using a low‐valent cobalt catalyst. The transformation has a wide substrate scope and high functional‐group tolerance and led to 1,4‐dihydronaphthalenes. The formed cycloadducts were easily aromatized with MnO2 under air. A mechanistic investigation suggests that the transformation proceeds through a
Cobalt-catalyzed alkyne cyclotrimerization and crossed [2 + 2 + 2] cycloadditions are developed in a plug flow reactor. The protocol generally uses 5 mol % of Co2(CO)8 and is scalable at least at multigram scale. Efficient and scalable use of Co2(CO)8 for crossed reactions of diynes and alkynes has hardly any precedent.
Cyclotrimerisation catalytique d'alcynes par des complexes du nickel formés “in situ”
作者:P. Alphonse、F. Moyen、P. Mazerolles
DOI:10.1016/0022-328x(88)80249-3
日期:1988.5
Catalytic cyclotrimerization of acetylenic compounds by transient complexes formed in the reduction of nickelhalides by magnesium, occurs with many alkynes; however, this cyclization is hindered when bulky groups are close neighbors of the triple bond or when acceptor groups are in the α position with respect to the unsaturated carbon. On the other hand, the yield of trimer increases to become quantitative
Solvent-Free Synthesis of 2-Pyrones from Alkynes and Carbon Dioxide Catalyzed by Ni(1,5-cyclooctadiene)<sub>2</sub>/Trialkylphosphine Catalysts
作者:Ikuko Mitani、Yasuhisa Kishimoto
DOI:10.1055/s-2005-872266
日期:——
Solvent-free, efficient, and mild 2-pyrone synthesis by the cycloaddition of alkynes with CO2 has been achieved under compressed CO2 with a Ni(cod)2/P(C4H9)3 or Ni(cod)2/P(C8H17)3 catalyst; both high yields (up to 98%) and selectivities (up to 99%) are attained. One attractive aspect of these catalysts is their high efficiency at low CO2 pressures (4 MPa). The applicability of this reaction to a broad range of alkyne substrates and the ease of handling the phosphine ligands are additional merits of the present new catalytic systems in comparison to the previously reported Ni(cod)2/P(CH3)3 catalyst in supercritical CO2.