81828-87-7Relevant academic research and scientific papers
Synthesis and characterization of an isopropylBippyPhos precatalyst
Coffey, Steven B.,Bernhardson, David J.,Wright, Stephen W.
, (2021/12/17)
A review of our high throughput reaction screening data revealed that BippyPhos was frequently associated with successful outcomes in Buchwald – Hartwig amination reactions. A barrier to the wider use of this ligand, particularly among those performing sm
Importance of Two-Electron Processes in Fe-Catalyzed Aryl-(hetero)aryl Cross-Couplings: Evidence of Fe0/FeIICouple Implication
Wowk, Vincent,Rousseau, Lidie,Lefèvre, Guillaume
supporting information, p. 3253 - 3266 (2021/10/12)
We demonstrate in this work that two drastically distinct mechanisms can be involved in aryl-(hetero)aryl Fe-mediated cross-couplings between Grignard reagents and organic halides, depending on the nature of the latter. (Hetero)aryl electrophiles, which easily undergo one-electron reduction, can be involved in a FeII/FeIII coupling sequence featuring an in situ generated organoiron(II) species, akin to their aliphatic analogues. On the other hand, less easily reduced substrates can be activated by transient Fe0 species formed by the reduction of the precatalyst. In this case, the coupling mechanism relies on two-electron elementary steps involving the Fe0/FeII redox couple and proceeds by an oxidative addition/reductive elimination sequence. Hammett analysis shows that both those elementary steps are faster for electrophiles substituted by electron-withdrawing groups. The two mechanisms discussed herein can be involved concomitantly for electrophiles displaying an average oxidative power. Attesting to the feasibility of the aforementioned bielectronic mechanism, high-spin organoiron(II) intermediates formed by two-electron oxidative addition onto (hetero)aryl halides in catalytically relevant conditions were also characterized for the first time. Those results are sustained by paramagnetic 1H NMR, kinetics monitoring, and density functional theory (DFT) calculations.
Dehydrogenative etherification homocoupling of heterocyclic N-oxides
Zhang, Dong,Qiao, Kai,Yuan, Xin,Zheng, Mingwei,Fang, Zheng,Wan, Li,Guo, Kai
supporting information, p. 1752 - 1756 (2018/04/10)
A novel approach was developed for the dehydrogenative etherification homocoupling of heterocyclic N-oxides in the presence of silver oxide and PyBroP. Various substrates were well tolerated and the desired products were obtained in moderate to good yields. Generally, this reaction features excellent functional group compatibility, broad substrate scope and good regioselectivity.
Blue-light-promoted carbon-carbon double bond isomerization and its application in the syntheses of quinolines
Chen, Xinzheng,Qiu, Shuxian,Wang, Sasa,Wang, Huifei,Zhai, Hongbin
, p. 6349 - 6352 (2017/08/10)
A blue-light-promoted carbon-carbon double bond isomerization in the absence of any photoredox catalyst is reported. It provides rapid access to a series of quinolines in good to excellent yields under simple aerobic conditions. The protocol is direct, catalyst-free and operationally convenient.
Regioselective Chlorination of Quinoline N-Oxides and Isoquinoline N-Oxides Using PPh3/Cl3CCN
Qiao, Kai,Wan, Li,Sun, Xiaoning,Zhang, Kai,Zhu, Ning,Li, Xin,Guo, Kai
, p. 1606 - 1611 (2016/04/05)
A novel method for the regioselective C2-chlorination of heterocyclic N-oxides has been developed. PPh3/Cl3CCN were used as chlorinating reagents and the desired N-heterocyclic chlorides were obtained smoothly in satisfactory yields. The reactions proceeded in a highly efficient and selective manner across a broad range of substrates demonstrating excellent functional group tolerance. In addition, this chlorination reaction can be used for the modification of N-heterocyclic scaffolds of appealing ligands and pharmaceuticals.
Kumada-Tamao-Corriu coupling of heteroaromatic chlorides and aryl ethers catalyzed by (IPr)Ni(allyl)Cl
Iglesias, Maria Jose,Prieto, Auxiliadora,Nicasio, M. Carmen
supporting information, p. 4318 - 4321 (2012/10/29)
The complex (IPr)Ni(allyl)Cl (IPr = 1,3-bis(2,6-diisopropylphenyl) imidazolidene) catalyzes the cross-coupling reactions of heteroaromatic chlorides with aryl Grignard reagents. Catalyst loadings as low as 0.1 mol % have been used to afford the products in excellent yields. This nickel-based catalytic system also promotes the activation of the CAr-O bond of anisoles in the Kumada-Tamao-Corriu reaction under fairly mild conditions.
Highly selective biaryl cross-coupling reactions between aryl halides and aryl Grignard reagents: A new catalyst combination of N-heterocyclic carbenes and iron, cobalt, and nickel fluorides
Hatakeyama, Takuji,Hashimoto, Sigma,Ishizuka, Kentaro,Nakamura, Masaharu
supporting information; experimental part, p. 11949 - 11963 (2009/12/08)
Combinations of N-heterocyclic carbenes (NHCs) and fluoride salts of the iron-group metals (Fe, Co, and Ni) have been shown to be excellent catalysts for the cross-coupling reactions of aryl Grignard reagents (Ar1MgBr) with aryl and heteroaryl halides (Ar2X) to give unsymmetrical biaryls (Ar1-Ar2). Iron fluorides in combination with SIPr, a saturated NHC ligand, catalyze the biaryl cross-coupling between various aryl chlorides and aryl Grignard reagents in high yield and high selectivity. On the other hand, cobalt and nickel fluorides in combination with IPr, an unsaturated NHC ligand, exhibit interesting complementary reactivity in the coupling of aryl bromides or iodides; in contrast, with these substrates the iron catalysts show a lower selectivity. The formation of homocoupling byproducts is suppressed markedly to less than 5% in most cases by choosing the appropriate metal fluoride/NHC combination. The present catalyst combinations offer several synthetic advantages over existing methods: practical synthesis of a broad range of unsymmetrical biaryls without the use of palladium catalysts and phosphine ligands. On the basis of stoichiometric control experiments and theoretical studies, the origin of the unique catalytic effect of the fluoride counterion can be ascribed to the formation of a higher-valent heteroleptic metalate [Ar1MF2]MgBr as the key intermediate in our proposed catalytic cycle. First, stoichiometric control experiments revealed the stark differences in chemical reactivity between the metal fluorides and metal chlorides. Second, DFT calculations indicate that the initial reduction of di- or trivalent metal fluoride in the wake of transmetalation with PhMgCl is energetically unfavorable and that formation of a divalent heteroleptic metalate complex, [PhMF2]MgCl (M ) Fe, Co, Ni), is dominant in the metal fluoride system. The heteroleptic ate-complex serves as a key reactive intermediate, which undergoes oxidative addition with PhCl and releases the biaryl cross-coupling product Ph-Ph with reasonable energy barriers. The present crosscoupling reaction catalyzed by iron-group metal fluorides and an NHC ligand provides a highly selective and practical method for the synthesis of unsymmetrical biaryls as well as the opportunity to gain new mechanistic insights into the metal-catalyzed cross-coupling reactions.
Iron-catalyzed selective biaryl coupling: Remarkable suppression of homocoupling by the fluoride anion
Hatakeyama, Takuji,Nakamura, Masaharu
, p. 9844 - 9845 (2008/03/12)
In the presence of iron(III) fluoride and 1,3-bis(2,6-di-i-propylphenyl)imidazolinium chloride, aryl magnesium bromides react with aryl chlorides to give the corresponding cross-coupling products, unsymmetrical biaryls, in good to excellent yields. Copyright
Cobalt-catalyzed cross-coupling reactions of heterocyclic chlorides with arylmagnesium halides and of polyfunctionalized arylcopper reagents with aryl bromides, chlorides, fluorides and tosylates
Korn, Tobias J.,Schade, Matthias A.,Cheemala, Murthy N.,Wirth, Stefan,Guevara, Simon A.,Cahiez, Gerard,Knochel, Paul
, p. 3547 - 3574 (2008/03/14)
A range of aromatic organocopper or organomagnesium compounds undergo smooth cross-coupling reactions with aryl bromides, chlorides, fluorides and tosylates, leading to polyfunctionalized aromatics or heterocycles in the presence of cobalt salts (5-7.5 mol%) as catalysts. Very mild reaction conditions are needed and, in the case of cross-coupling with organocopper compounds, Bu4NI (1 equiv) and 4-fluorostyrene (20 mol%) are essential as promoters for successful couplings. Georg Thieme Verlag Stuttgart.
