Cobalt-Mediated η5-Pentadienyl/Alkyne [5 + 2] Cycloaddition Reactions: Substitution Effects, Bicyclic Synthesis, and Photochemical η4-Cycloheptadiene Demetalation

Recent development on the [5+2] cycloadditions and their application in natural product synthesis

The recent developments on the [5+2] cycloadditions and their application in the synthesis of complex natural products are discussed.

Ynol Ethers as Ketene Equivalents in Rhodium-Catalyzed Intermolecular [5 + 2] Cycloaddition Reactions

The previously unexplored metal-catalyzed [5 + 2] cycloadditions of vinylcyclopropanes (VCPs) and electron-rich alkynes (ynol ethers) have been found to provide a highly efficient, direct route to dioxygenated seven-membered rings, a common feature of numerous natural and non-natural targets and building blocks for synthesis. The reactions proceed in high yield at room temperature and tolerate a broad range of functionalities. Substituted VCPs were found to react with high regioselectivity.

Crystal structure of bis-(η2-ethyl-ene)(η5-penta-methyl-cyclo-penta-dien-yl)cobalt

The title compound, [Co(C10H15)(C2H4)2], was prepared by Na/Hg reduction of [Co2(C10H15)2(μ-Cl)2] in THF under an ethyl-ene atmosphere and crystallized from pentane at 193 K. The Co-C(olefin) bonds have an average length of 2.022 (2) Å, while the Co-C(penta-dien-yl) bonds average 2.103 (19) Å. The olefin C=C bonds are 1.410 (1) Å. The dihedral angle between the planes defined by the cyclo-penta-dienyl ligand and the two olefin ligands is 0.25 (12)°. In the crystal, mol-ecules are linked into chains by C-H⋯π inter-actions.