their reactivity in [2+2+2] cycloaddition reactions compared with highly active [CpCo(H2CCHSiMe3)2] (1). Whereas 1 is an excellent precursor for the synthesis of [CpCo(olefin)(phosphite)] complexes (2 a–f), [CpCo(phosphite)2] complexes (3 a–e) were prepared photochemically from [CpCo(cod)]. The complexes were evaluated in the cyclotrimerization reaction of diynes with nitriles yielding pyridines. For
Various alkynes reacted with allyl tosylates in the presence of palladium catalysts, giving polysubstituted benzenes with good to high regioselectivity. Pentasubstituted and trisubstituted benzenes were readily prepared by reaction of internal alkynes and terminal alkynes, respectively. The combination of allyl alcohols and p-toluenesulfonic anhydride could be utilized in place of isolated allyl tosylates. The cyclization of diynes with allyl tosylate afforded bicyclic compounds containing an aromatic ring.
Unprecedented Double C−C Bond Cleavage of a Cyclopentadienyl Ligand
Double C-C bond cleavage of a cyclopentadienyl ligand proceeded to titanacyclopentadienes when 2 equiv of nitriles were added and the resulting two-carbon unit and three-carbon unit were converted into a benzene derivative and a pyridine derivative, respectively, in one-pot.
Ren, Shenyong; Igarashi, Eri; Nakajima, Kiyohiko, Journal of the American Chemical Society, 2009, vol. 131, p. 7492 - 7493