The First Metallacyclopentadiene(Alkyne) Complexes and Their Discrete Isomerization to η4-Bound Arenes: The Missing Link in the Prevalent Mechanism of Transition Metal Catalyzed Alkyne Cyclotrimerizations, as Exemplified by Cyclopentadienylcobalt
1,2,3,4-Tetraethynylbenzene as a Template for Cobalt-Catalyzed Alkyne Cocyclizations: Synthesis of 2,3,8,9-Tetrakis(trimethylsilyl) Angular [3]Phenylene and Bent [5]Phenylene (Benzo[1′′,2′′:3,4;3′′,4′′:3′,4′]dicyclobuta[1,2-<i>b</i>:1′,2′-<i>b</i>′]bisbiphenylene)
An approach to the synthesis of bent phenylenes is described, which features 1,2,3,4-tetraethynylbenzene as starting material. Application of this synthon in CpCo-catalyzed alkyne cocyclizations allows the total synthesis of bent [5]phenylene, the seventh isomer of the family of twelve [5]phenylenes to be isolated.
Activated Phenacenes from Phenylenes by Nickel-Catalyzed Alkyne Cycloadditions
作者:Zhenhua Gu、Gregory B. Boursalian、Vincent Gandon、Robin Padilla、Hao Shen、Tatiana V. Timofeeva、Paul Tongwa、K. Peter C. Vollhardt、Andrey A. Yakovenko
DOI:10.1002/anie.201103428
日期:2011.9.26
Going zigzag, helical, or in‐between: Angular phenylenes show a propensity for adding alkynesfrom the bay region in processes catalyzed by [Ni(cod)(PMe3)2] (see scheme). These transformations generate novel strain‐ and electronically activatedphenacenes. Mechanistic studies in conjunction with DFT calculations (R=Ph) provide a plausible mechanistic picture.