- 1-Methyl-1H-tetrazol-5-yl (MT) sulfones in the Julia-Kocienski olefination: Comparison with the PT and the TBT sulfones
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The stability and the stereoselectivity of newly prepared n-pentyl 1-methyl-1H-tetrazol-5-yl (MT) sulfone 1a in the Julia-Kocienski reactions were compared with those of the PT sulfone 1b and the TBT sulfone 1c. The improved stability of the anion derived from the n-pentyl MT sulfone 1a enhanced the efficiency of the olefination reactions and gave higher yields of the product alkenes 3 compared with the PT sulfone 1b. Especially high E-selectivity and high yields were obtained from the reaction with aromatic aldehydes and α,β-unsaturated aldehydes. The selectivity of 1a was not so sensitive to the change of base counter ion compared with the PT sulfone 1b. The reaction of the MT sulfones having either ethyl or a longer alkyl chain also gave E-alkenes selectively in high yields.
- Ando, Kaori,Kawano, Daiki,Takama, Daiki,Semii, Yutaka
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p. 1566 - 1569
(2019/05/22)
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- Copper- and Nickel-Catalyzed Cross-Coupling Reaction of Monofluoroalkenes with Tertiary, Secondary, and Primary Alkyl and Aryl Grignard Reagents
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A highly efficient cross-coupling reaction of monofluoroalkenes with tertiary, secondary, and primary alkyl and aryl Grignard reagents in the presence of a catalytic amount of copper or nickel catalyst, respectively, has been developed. The reactions proceeded smoothly at room temperature, providing (E)-alkene isomers in moderate to high yields. Plausible mechanisms of the Ni-catalyzed coupling reaction of monofluoroalkene with Grignard reagents are suggested.
- Shi, Hongyan,Dai, Wenpeng,Wang, Biyun,Cao, Song
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supporting information
p. 459 - 463
(2018/02/17)
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- A highly efficient and recyclable Pd(PPh3)4/PEG-400 system for Stille cross-coupling reactions of organostannanes with aryl bromides
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Pd(PPh3)4 in PEG-400 is shown to be a highly efficient catalyst for the Stille cross-coupling reactions of various organotin compounds with aryl bromides. The reaction could be conducted at 80 °C using NaOAc as base, yielding a variety of biaryls, alkynes and alkenes in good to excellent yields. The isolation of the products was readily performed by extraction with petroleum ether and the Pd(PPh3)4/PEG-400 system could be easily recycled and reused five times without any significant loss of activity.
- Huang, Xue,Yao, Fang,Wei, Ting,Cai, Mingzhong
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p. 547 - 550
(2017/10/03)
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- The first example of hydrozirconation of alkynes in room temperature ionic liquids
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Hydrozirconation of terminal alkynes in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) at 30 °C gave highly regio- and stereoselectively (E)-vinylzirconium complexes, which underwent a cross-coupling reaction with aryl halides in the presence of Pd(PPh 3)4 to afford (E)-1,2-disubstituted ethenes in good to high yields. Our system not only avoids the use of easily volatile THF or CH2Cl2 as solvent but also solves the basic problem of palladium catalyst reuse.
- Huang, Bin,Wang, Pingping,Hao, Wenyan,Cai, Ming-Zhong
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experimental part
p. 2685 - 2688
(2011/07/09)
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- MCM-41-supported mercapto palladium(O) complex: An efficient and recyclable catalyst for the heterogeneous Stille coupling reaction
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The Stille cross-coupling reaction of organostannanes with aryl halides was achieved in the presence of a catalytic amount of MCM-41-supported mercapto palladium(O) complex (1 mol%) in DMF-H2O (9:1) under air atmosphere in good to high yields. This MCM-41-supported palladium catalyst can be reused at least 10 times without any decrease in activity. Copyright
- Zhao, Hong,Zheng, Guomin,Hao, Wenyan,Cai, Mingzhong
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experimental part
p. 92 - 98
(2010/11/04)
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- MCM-41-supported bidentate phosphine palladium(0) complex as an efficient catalyst for the heterogeneous Stille reaction
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A Stille coupling reaction of organostannanes with organic halides has been developed in the presence of a catalytic amount of MCM-41-supported bidentate phosphine palladium(0) complex (0.5 mol %) in DMF/H2O (9:1) under air atmosphere in high yields. This polymeric palladium catalyst exhibits higher activity than Pd(PPh3)4 and can be reused at least 10 times without any decrease in activity.
- Zhao, Hong,Wang, Yue,Sha, Junchao,Sheng, Shouri,Cai, Mingzhong
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p. 7517 - 7523
(2008/12/20)
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- Additions of organomanganese reagents to conjugated nitroolefins
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Additions of organomanganese reagents to aromatic and aliphatic conjugated nitroolefins were examined for the first time. In most cases reaction proceeded rapidly at -30°C. Unlike Mn reagents lacking β-hydrogens (Me, Ph), which lead to oxidative coupling and reductive dimerisation of nitrostyrenes, benzylmanganese chloride gives 1,4-addition in yields exceeding Grignard or Cu-assisted additions. At 0°C alkyl(Bu, Pr)-manganese reagents undergo an addition-migration-elimination process with nitrostyrenes providing a convenient and stereospecific entry into arylated trans-olefins.
- Namboothiri,Hassner, Alfred
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- Palladium- or Nickel-Catalyzed Reactions of Alkenylmetals with Unsaturated Organic Halides as a Selective Route to Arylated Alkenes and Conjugated Dienes: Scope, Limitations, and Mechanism
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Stereo- and regiodefined alkenylmetals containing Al, Zr, and Zn react with aryl and alkenyl iodides and bromides in the presence of catalytic amounts of Pd or Ni complexes containing phosphine ligands, such as PPh3, to give the corresponding cross-coupled products.Palladium catalysts permit nearly 100 percent stereospecificity in both alkenyl-aryl and alkenyl-alkenyl coupling reactions, whereas nickel catalysts lead to partial stereochemical scrambling in the alkenyl-alkenyl coupling.Although many other metals including Li, Mg, Cd, Hg, B, Si, Sn, Ti, and Ce were also used, the results were inferior to those obtained with Al, Zr, and Zn under the conditions used in the present study.The turnover numbers for the palladium-catalyzed reactions of PhI with (E)-1-octenylmetals containing Al, Zr, and Zn were 2,3, and > 2000 mmol of (E)-1-octenylbenzene (8) per mmol of Pd(PPh3)4 per hour at room temperature, respectively.The stoichiometric reaction of PhPd(PPh3)2I (6) with 1.2 equiv of (E)-1-octenylzinc chloride (7) in a 2:1 mixture of CD2Cl2 and THF was examined in detail.The reaction follows second-order konetics (k2 = 2.9 L/(mol.min) at 0 deg C) to give 8 without the buildup of any intermediate.The results are consistent with a slow formation of 9 via transmetalation followed by its rapid reductive elmination to give 8 and "Pd(PPhe3)2".Addition of PhI to the reaction mixture rapidly gives 6 in 98 percent yield, supporting the plausibility of the proposed oxidative addition step.These results are consistent with the proposed mechanism consisting of oxidative addition of Pd(0) complexes, rate-determining transmetalation involving Pd(II) complexes, and rapid decomposition of diorganopalladium(II) species to produce the coupling products in one or more subsequent steps.The rate-determining transmetalation step provides an explanation for the effect of metals in organometallic reagents used stoichiometrically.
- Negishi, Ei-ichi,Takahashi, Tamotsu,Baba, Shigeru,Horn, David E. Van,Okukado, Nobuhisa
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p. 2393 - 2401
(2007/10/02)
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