- Transition-Metal-Free Oxidative Cross-Coupling of Tetraarylborates to Biaryls Using Organic Oxidants
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Readily prepared tetraarylborates undergo selective (cross)-coupling through oxidation with Bobbitt's salt to give symmetric and unsymmetric biaryls. The organic oxoammonium salt can be used either as a stoichiometric oxidant or as a catalyst in combination with in situ generated NO2 and molecular oxygen as the terminal oxidant. For selected cases, oxidative coupling is also possible with NO2/O2 without any additional nitroxide-based cocatalyst. Transition-metal-free catalytic oxidative ligand cross-coupling of tetraarylborates is unprecedented and the introduced method provides access to various biaryl and heterobiaryl systems.
- Gerleve, Carolin,Studer, Armido
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supporting information
p. 15468 - 15473
(2020/05/06)
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- Iodine-catalyzed synthesis of N,N'-chelate organoboron aminoquinolate
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We disclose a novel method for the synthesis of fluorescent N,N'-chelate organoboron compounds in high efficiency by treatment of aminoquinolates with NaBAr4/ R'COOH in the presence of an iodine catalyst. These compounds display high air and thermal stability. A possible catalytic mechanism based on the results of control experiments has been proposed. Fluorescence quantum yield of 3b is up to 0.79 in dichloromethane.
- Qiu, Renhua,Yang, Tianbao,Cao, Xin,Zhang, Xing-Xing,Ou, Yifeng,Au, Chak-Tong,Yin, Shuang-Feng
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p. 12430 - 12443
(2020/11/10)
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- Palladium-Assisted "Aromatic Metamorphosis" of Dibenzothiophenes into Triphenylenes
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Abstract Two new palladium-catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4-chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium-catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular SN2 reaction to form a teraryl sulfonium salt, and 4) palladium-catalyzed intramolecular C-S/C-H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor-made fashion in satisfactory overall yields. A change of heart: The invention of two palladium-catalyzed arylation reactions of organosulfur compounds enabled the transformation of dibenzothiophenes into triphenylenes and thus a fundamental change in the core aromatic structure (see scheme). Both symmetrical and unsymmetrical triphenylenes were synthesized in a tailor-made fashion in satisfactory overall yield.
- Vasu, Dhananjayan,Yorimitsu, Hideki,Osuka, Atsuhiro
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supporting information
p. 7162 - 7166
(2015/06/08)
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- Base-free palladium-catalyzed cross-coupling of arylsulfonium salts with sodium tetraarylborates
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Palladium-catalyzed cross-coupling reactions of arylsulfonium salts with sodium tetraarylborates were found to proceed smoothly without recourse to an additional base, providing a new, reliable route to biaryls from organosulfur compounds.
- Osuka, Atsuhiro,Vasu, Dhananjayan,Yorimitsu, Hideki
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p. 3286 - 3291
(2020/10/20)
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- An Umpolung Approach to Alkene Carboamination: Palladium Catalyzed 1,2-Amino-Acylation, -Carboxylation, -Arylation, -Vinylation, and -Alkynylation
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Conventional approaches to Pd-catalyzed alkene 1,2-carboamination rely upon the combination of a nucleophilic nitrogen-based component and an internal C-based or external oxidant. In this study, we outline an umpolung approach, which is triggered by oxidative initiation at an electrophilic N-based component and employs "standard" organometallic nucleophiles to introduce the new carbon-based fragment. Specifically, oxidative addition of a Pd(0)-catalyst into the N-O bond of O-pentafluorobenzoyl oxime esters generates imino-Pd(II) intermediates, which undergo 5-exo cyclization with sterically diverse alkenes. The resultant alkyl-Pd(II) intermediates are intercepted by organometallic nucleophiles or alcohols, under carbonylative or noncarbonylative conditions, to provide 1,2-carboamination products. This approach provides, for the first time, a unified strategy for achieving alkene 1,2-amino-acylation, -carboxylation, -arylation, -vinylation, and -alkynylation. For carbonylative processes, orchestrated protodecarboxylation of the pentafluorobenzoate leaving group underpins reaction efficiency. This process is likely a key feature in related Narasaka-Heck cyclizations and accounts for the efficacy of O-pentafluorobenzoyl oxime esters in aza-Heck reactions of this type. (Chemical Equation Presented).
- Faulkner, Adele,Scott, James S.,Bower, John F.
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supporting information
p. 7224 - 7230
(2015/06/25)
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- Ligand-free, atom-efficient Suzuki-Miyaura type cross-coupling reactions at room temperature
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The atom-efficient cross-coupling reaction of sodium tetraarylborates with aryl iodides and bromides was reported. The reaction can be performed directly using a catalytic system composed of palladium chloride, sodium carbonate and methanol (PdCl2/Na2CO3/MeOH) under heat-free conditions at room temperature in an open air conditions. The reactions carried out in an atom-efficient way as 4 equiv of aryl halides coupled effectively with 1 equiv of sodium tetraarylborates to furnish 4 equiv of the corresponding functionalized biaryls in good to excellent yields.
- Zhou, Wen-Jun,Wang, Ke-Hu,Wang, Jin-Xian,Gao, Zhi-Rong
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experimental part
p. 7633 - 7641
(2010/12/19)
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- Sodium tetraarylborates as effective nucleophiles in rhodium/diene- catalyzed 1,4-addition to β,β-disubstituted α,β-unsaturated ketones: Catalytic asymmetric construction of quaternary carbon stereocenters
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(Chemical Equation Presented) A rhodium-catalyzed 1,4-addition of sodium tetraarylborates to β,β-disubstituted α,β-unsaturated ketones is described. Highly efficient asymmetric catalysis has also been achieved by employing a readily available chiral diene
- Shintani, Ryo,Tsutsumi, Yosuke,Nagaosa, Makoto,Nishimura, Takahiro,Hayashi, Tamio
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supporting information; experimental part
p. 13588 - 13589
(2009/12/31)
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