18908-74-2Relevant articles and documents
Catalyst activation, deactivation, and degradation in palladium-mediated negishi cross-coupling reactions
B?ck, Katharina,Feil, Julia E.,Karaghiosoff, Konstantin,Koszinowski, Konrad
, p. 5548 - 5560 (2015)
Pd-mediated Negishi cross-coupling reactions were studied by a combination of kinetic measurements, electrospray-ionization (ESI) mass spectrometry, 31P NMR and UV/Vis spectroscopy. The kinetic measurements point to a rate-determining oxidative addition. Surprisingly, this step seems to involve not only the Pd catalyst and the aryl halide substrate, but also the organozinc reagent. In this context, the ESI-mass spectrometric observation of heterobimetallic Pd-Zn complexes [L2PdZnR]+ (L=S-PHOS, R=Bu, Ph, Bn) is particularly revealing. The inferred presence of these and related neutral complexes with a direct Pd-Zn interaction in solution explains how the organozinc reagent can modulate the reactivity of the Pd catalyst. Previous theoretical calculations by Gonzlez-Prez et al. (Organometallics 2012, 31, 2053) suggest that the complexation by the organozinc reagent lowers the activity of the Pd catalyst. Presumably, a similar effect also causes the rate decrease observed upon addition of ZnBr2. In contrast, added LiBr apparently counteracts the formation of Pd-Zn complexes and restores the high activity of the Pd catalyst. At longer reaction times, deactivation processes due to degradation of the S-PHOS ligand and aggregation of the Pd catalyst come into play, thus further contributing to the appreciable complexity of the title reaction. Catalytic complexity: The Pd catalyst used in Negishi cross-coupling reactions shows an unexpected heterogeneity and complexity. Among the various species observed in solution, heterobimetallic Pd-Zn complexes are of particular interest (see figure). These species also seem key to understanding the kinetics of Negishi cross-coupling reactions. S-PHOS=2-dicyclohexylphosphino-2,6-dimethoxybiphenyl.
Photo-Ni-Dual-Catalytic C(sp2)-C(sp3) Cross-Coupling Reactions with Mesoporous Graphitic Carbon Nitride as a Heterogeneous Organic Semiconductor Photocatalyst
Antonietti, Markus,Ghosh, Indrajit,K?nig, Burkhard,Khamrai, Jagadish,Savateev, Aleksandr
, p. 3526 - 3532 (2020/04/09)
The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp2)-C(sp3) cross-co
Super electron donor-mediated reductive desulfurization reactions
Nozawa-Kumada, Kanako,Ito, Shungo,Noguchi, Koto,Shigeno, Masanori,Kondo, Yoshinori
, p. 12968 - 12971 (2019/11/05)
The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
Construction of Di(hetero)arylmethanes Through Pd-Catalyzed Direct Dehydroxylative Cross-Coupling of Benzylic Alcohols and Aryl Boronic Acids Mediated by Sulfuryl Fluoride (SO2F2)
Zhao, Chuang,Zha, Gao-Feng,Fang, Wan-Yin,Rakesh,Qin, Hua-Li
supporting information, p. 1801 - 1807 (2019/02/07)
A practical Pd-catalyzed direct dehydroxylative coupling of (hetero)benzylic alcohols with (hetero)arylboronic acids for the constructions of di(hetero)arylmethane derivatives under SO2F2 was described. This new method provided a strategically distinct approach to di(hetero)arylmethane derivatives from readily available and abundant benzylic alcohols under mild condition.
Cobalt-Catalyzed Formation of Functionalized Diarylmethanes from Benzylmesylates and Aryl Halides
Reddy, Bhoomireddy Rajendra Prasad,Chowdhury, Sushobhan,Auffrant, Audrey,Gosmini, Corinne
supporting information, p. 3026 - 3029 (2018/08/24)
A simple cobalt-catalyzed reductive coupling protocol allowing the synthesis of functionalized diarylmethanes from benzyl mesylate is described. The possibility to directly use the benzyl alcohol as a result of a two-step reaction is also presented. This method tolerates a variety of functional groups. A benzyl radical is likely involved. (Figure presented.).
Mechanochemical Activation of Zinc and Application to Negishi Cross-Coupling
Cao, Qun,Howard, Joseph L.,Wheatley, Emilie,Browne, Duncan L.
, p. 11339 - 11343 (2018/08/28)
A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross-coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp3)–C(sp2) and C(sp2)–C(sp2) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.
Visible-Light-Induced Nickel-Catalyzed Negishi Cross-Couplings by Exogenous-Photosensitizer-Free Photocatalysis
Abdiaj, Irini,Fontana, Alberto,Gomez, M. Victoria,de la Hoz, Antonio,Alcázar, Jesús
supporting information, p. 8473 - 8477 (2018/04/30)
The merging of photoredox and transition-metal catalysis has become one of the most attractive approaches for carbon–carbon bond formation. Such reactions require the use of two organo-transition-metal species, one of which acts as a photosensitizer and t
Expanding the limit of Pd-catalyzed decarboxylative benzylations
Kong, Duanyang,Moon, Patrick J.,Qian, Wenyu,Lundgren, Rylan J.
supporting information, p. 6835 - 6838 (2018/06/26)
The Pd-catalyzed decarboxylative cross-coupling of electron-deficient aryl acetates with aryl bromides is reported. The method widens the scope of benzylic partners that can undergo efficient reactivity from highly activated nitrophenylacetates established previously, to a diverse series of substrates bearing modestly stabilizing groups, allowing direct access to functionalized diarylmethanes. Mechanistic studies support the role of dienolates as key intermediates in the coupling process.
Transition-Metal-Free Suzuki-Type Cross-Coupling Reaction of Benzyl Halides and Boronic Acids via 1,2-Metalate Shift
He, Zhiqi,Song, Feifei,Sun, Huan,Huang, Yong
supporting information, p. 2693 - 2699 (2018/02/28)
Cross-coupling of organoboron compounds with electrophiles (Suzuki-Miyaura reaction) has greatly advanced C-C bond formation and has been well received in medicinal chemistry. During the past 50 years, transition metals have played a central role throughout the catalytic cycle of this important transformation. In this process, chemoselectivity among multiple carbon-halogen bonds is a common challenge. In particular, selective oxidative addition of transition metals to alkyl halides rather than aryl halides is difficult due to unfavorable transition states and bond strengths. We describe a new approach that uses a single organic sulfide catalyst to activate both C(sp3) halides and arylboronic acids via a zwitterionic boron "ate" intermediate. This "ate" species undergoes a 1,2-metalate shift to afford Suzuki coupling products using benzyl chlorides and arylboronic acids. Various diaryl methane analogues can be prepared, including those with complex and biologically active motifs. The reactions proceed under transition-metal-free conditions, and C(sp2) halides, including aryl bromides and iodides, are unaffected. The orthogonal chemoselectivity is demonstrated in the streamlined synthesis of highly functionalized diaryl methane scaffolds using multi-halogenated substrates. Preliminary mechanistic experiments suggest both the sulfonium salt and the sulfur ylide are involved in the reaction, with the formation of sulfonium salt being the slowest step in the overall catalytic cycle.
One-pot borylation/Suzuki-Miyaura sp2-sp3 cross-coupling
Whitaker, Luke,Harb, Hassan Y.,Pulis, Alexander P.
, p. 9364 - 9367 (2017/08/23)
We describe the first one-pot borylation/Suzuki-Miyaura sp2-sp3 cross-coupling between readily available aryl (pseudo)halides and activated alkyl chlorides. This method streamlines the synthesis of diaryl methanes, α-aryl carbonyls and allyl aryl compounds, substructures that are commonly found in life changing drug molecules.
