5325-97-3Relevant articles and documents
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Durland,Adkins
, (1938)
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Intramolecular Cobalt-Mediated Cycloaddition of Linear Enediynes. A Useful Synthetic Entry into Cobalt-Protected Tricyclic Dienes and Their Synthetic Elaboration
Sternberg, Ethan D.,Vollhardt, K. Peter C.
, p. 1564 - 1573 (1984)
CpCo(CO)2 undergoes reaction with the linear α,δ,ω-enediynes 4, 10, 18, 22 and 25 to give the CpCo-complexed tricyclic dienes 5, 11, 19, 20, 23, 24, 26, and possibly 27.The free ligands may be obtained in good yield by oxidative demetalation.Treatment of the dienylsilane 12 with bromine gave the desilylated aromatic 13, whereas reaction with m-chloroperbenzoic acid furnished the dienol 14 and α-trimethylsilyl β,γ-enone 15.The latter rearranged to the desilylated α,β-enone 17 with acid.Some mechanistic discussion is presented concerned with the course of the cobalt-mediated cyclization reaction.Hydride abstraction from 11 resulted in the cation 28 which underwent unexpected nucleophilic addition to both ligands, in addition to deprotonation to benzene complex 32 and the free aromatic ligand 31.
Catalyzed transfer hydrogenation by 2-propanol for highly selective PAHs reduction
Philippov,Chibiryaev,Martyanov
, p. 15 - 22 (2020/07/15)
Catalytic hydrogenation of mono-, di- and trinuclear aromatic compounds has been studied under hydrogen transfer conditions at 150 °C and 82 °C in 2-PrOH as a hydrogen donor and with Raney nickel as a catalyst. In contrast to conjugated or condensed aromatic rings, isolated ones demonstrated low reactivity in transfer hydrogenation (TH) that can be used to increase the hydrogenation selectivity of the reaction. So, naphthalene and biphenyl are partially hydrogenated into tetralin and cyclohexylbenzene, respectively, with excellent conversion (≥ 96 %) and selectivity (≥ 98 %) for 5–6 h at 82 °C. Increasing the reaction temperature to 150 °C results expectedly in the hydrogenation of second aromatic ring, which occurs slowly enough. Only 8 % of decaline and 42 % of dicyclohexyl, correspondingly, were obtained after 5 h at 150 °C. At the same time, TH of trinuclear anthracene and phenanthrene at 150 °C resulted in the formation of deeper hydrogenated octahydro-anthracenes and -phenanthrenes, respectively.
Ligand-enabled and magnesium-activated hydrogenation with earth-abundant cobalt catalysts
Han, Bo,Jiao, Hongmei,Ma, Haojie,Wang, Jijiang,Zhang, Miaomiao,Zhang, Yuqi
, p. 39934 - 39939 (2021/12/31)
Replacing expensive noble metals like Pt, Pd, Ir, Ru, and Rh with inexpensive earth-abundant metals like cobalt (Co) is attracting wider research interest in catalysis. Cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. Herein, we describe a hydrogenation method for polycyclic aromatic hydrocarbons (PAHs) and olefins with a magnesium-activated earth-abundant Co catalyst. When diketimine was used as a ligand, simple and inexpensive metal salts of CoBr2in combination with magnesium showed high catalytic activity in the site-selective hydrogenation of challenging PAHs under mild conditions. Co-catalyzed hydrogenation enabled the reduction of two side aromatics of PAHs. A wide range of PAHs can be hydrogenated in a site-selective manner, which provides a cost-effective, clean, and selective strategy to prepare partially reduced polycyclic hydrocarbon motifs that are otherwise difficult to prepare by common methods. The use of well-defined diketimine-ligated Co complexes as precatalysts for selective hydrogenation of PAHs and olefins is also demonstrated.
