20893-43-0Relevant articles and documents
Self-Assembled Multilayer-Stabilized Nickel Nanoparticle Catalyst for Ligand-Free Cross-Coupling Reactions: in situ Metal Nanoparticle and Nanospace Simultaneous Organization
Hoshiya, Naoyuki,Fujiki, Katsumasa,Taniguchi, Takahisa,Honma, Tetsuo,Tamenori, Yusuke,Xiao, Mincen,Saito, Nozomi,Yokoyama, Mami,Ishii, Akira,Fujioka, Hiromichi,Shuto, Satoshi,Sato, Yoshihiro,Arisawa, Mitsuhiro
, p. 2449 - 2459 (2016)
We have developed a conceptually and methodologically novel self-assembled multilayer nickel nanoparticle (NP) catalyst – sulfur-modified gold-supported Ni NPs (SANi) – for organic synthesis. The SANi catalyst was easily prepared through a three-step procedure involving simultaneous in situ metal NP and nanospace organization. This unique method does not require any conventional preformed template for immobilizing and stabilizing NPs. SANi catalyzes carbon-carbon bond-forming cross-coupling, Kumada coupling, and Negishi coupling reactions under ligand-free conditions and can be used repeatedly for these reactions. Physical analysis of SANi showed that the active species in these reactions are self-assembled multilayer zerovalent Ni NPs with a size of ～3 nm. (Figure presented.).
Photoredox-Assisted Reductive Cross-Coupling: Mechanistic Insight into Catalytic Aryl-Alkyl Cross-Couplings
Paul, Avishek,Smith, Mark D.,Vannucci, Aaron K.
, p. 1996 - 2003 (2017/02/26)
Here, we describe a photoredox-assisted catalytic system for the direct reductive coupling of two carbon electrophiles. Recent advances have shown that nickel catalysts are active toward the coupling of sp3-carbon electrophiles and that well-controlled, light-driven coupling systems are possible. Our system, composed of a nickel catalyst, an iridium photosensitizer, and an amine electron donor, is capable of coupling halocarbons with high yields. Spectroscopic studies support a mechanism where under visible light irradiation the Ir photosensitizer in conjunction with triethanolamine are capable of reducing a nickel catalyst and activating the catalyst toward cross-coupling of carbon electrophiles. The synthetic methodology developed here operates at low 1 mol % catalyst and photosensitizer loadings. The catalytic system also operates without reaction additives such as inorganic salts or bases. A general and effective sp2-sp3 cross-coupling scheme has been achieved that exhibits tolerance to a wide array of functional groups.
A 'meta effect' in the fragmentation reactions of ionised alkyl phenols and alkyl anisoles
Bouchoux, Guy,Sablier, Michel,Miyakoshi, Tetsuo,Honda, Takashi
scheme or table, p. 539 - 546 (2012/09/22)
The competition between benzylic cleavage (simple bond fission [SBF]) and retro-ene rearrangement (RER) from ionised ortho, meta and para RC 6H4OH and RC6H4OCH3 (R = n-C3H7, n-C4H9, n-C5H11, n-C7H15, n-C9H19, n-C 15H31) is examined. It is observed that the SBF/RER ratio is significantly influenced by the position of the substituent on the aromatic ring. As a rule, phenols and anisoles substituted by an alkyl group in meta position lead to more abundant methylene-2,4-cyclohexadiene cations (RER fragmentation) than their ortho and para homologues. This 'meta effect' is explained on the basis of energetic and kinetic of the two reaction channels. Quantum chemistry computations have been used to provide estimate of the thermochemistry associated with these two fragmentation routes. G3B3 calculation shows that a hydroxy or a methoxy group in the meta position destabilises the SBF and stabilises the RER product ions. Modelling of the SBF/RER intensities ratio has been performed assuming two single reaction rates for both fragmentation processes and computing them within the statistical RRKM formalism in the case of ortho, meta and para butyl phenols. It is clearly demonstrated that, combining thermochemistry and kinetics, the inequality (SBF/RER) metaorthopara holds for the butyl phenols series. It is expected that the 'meta effect' described in this study enables unequivocal identification of meta isomers from ortho and para isomers not only of alkyl phenols and alkyl anisoles but also in other alkyl benzene series. Copyright
