- Grignard allylic substitution reaction catalyzed by 1,2,3-triazol-5-ylidene magnesium complexes
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Allylic chlorides and phosphates reacted with alkyl-Grignard reagent in an SN2′-selective manner in the presence of a catalytic amount of 1,2,3-triazol-5-ylidenes to provide α-branched alkenes. Copyright
- Nomura, Ryosuke,Tsuchiya, Yuji,Ishikawa, Hiroyuki,Okamoto, Sentaro
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p. 1360 - 1363
(2013/05/08)
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- Copper-catalyzed regioselective allylic substitution reactions with indium organometallics
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The first nucleophilic allylic substitution reactions of triorganoindium compounds with allylic halides and phosphates are reported. The reactions of trialkyl- and triarylindium reagents with cinnamyl and geranyl halides and phosphates, with the aid of co
- Rodriguez, David,Sestelo, Jose Perez,Sarandeses, Luis A.
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p. 2518 - 2520
(2007/10/03)
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- ortho-Chelating Arenethiolatocopper(I) Complexes as Versatile Catalysts in the Regioselective Cross-Coupling of Allylic Derivatives with nBuMgI - An Example of Reversed Reactivity of Leaving Groups
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The regioselectivity in the arenethiolactocopper(I)-catalyzed cross-coupling reaction of allylic substrates was studied.It was found that allylic acetates gave highly γ-selective reactions in Et2O at 0 deg C with slow addition of the Grignard reagent, whereas α-selective reactions were obtained in THF at -30 deg C with fast addition of the Grignard reagent.It is proposed that the formation of an intermediate in Et2O, in which the allylic acetate coordinates in a bidentate fashion to the arenethiolatocopper(I) catalyst, dramatically increases the reactivity of the leaving group and results in excellent γ-selectivity.The remarkable observation that an allylic acetate can be made more reactive than an allylic chloride by using the arenethiolatocopper(I) catalyst 1a supports the theory of a bidentate coordination of the substrate to the catalyst through its double bond and acetate oxygen. - Keywords: allylic substrates . carbon-carbon coupling . catalysis . copper compounds
- Persson, Eva S. M.,Klaveren, Mayra van,Grove, David M.,Baeckvall, Jan E.,Koten, Gerard van
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p. 351 - 359
(2007/10/03)
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- Regiocontrol in Copper-Catalyzed Cross Coupling of Allylic Chlorides with Aryl Grignard Reagents
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The regioselectivity of copper-catalyzed reactions of allylic chlorides with aryl Grignard reagents was studied by variation of addition time of Grignard reagent, temperature, and amount of catalyst.It was found that slow addition of the Grignard reagent, increased temperature, and increased amount of catalyst favors formation of γ-product.Investigation of preformed organocopper species "Ar2CuMgBr" and "ArCu(X)MgBr" showed a striking difference in regioselectivity between the two reagents, the latter giving about 90percent γ-selectivity and the former being nonregioselective.It was found that for "ArCu(X)MgBr" the γ-selectivity increased with the electronegativity of the halide X (I Br Cl).
- Baeckvall, Jan-E.,Persson, Eva S. M.,Bombrun, Agnes
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p. 4126 - 4130
(2007/10/02)
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- Copper-catalyzed reactions of organotitanium reagents. Highly selective SN2′-allylation and conjugate addition
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In the presence of a catalytic amount of CuI·ILiCl, alkyltitanium (RTi(O-I-Pr)3) and titanate reagents (RnTi(O-i-Pr)5-nLi) undergo highly selective SN2′-alkylation reactions with allylic chlorides and allylic diethylphosphates in high yields. The regioselectivity of the reaction is as high as 99.8%. The reaction proceeds with excellent anti-stereoselectivity with respect to the nucleophile and the leaving group, and exhibits high 1,2-anti-diastereoselectivity with a δ-chiral allylic chloride. The catalytic copper reagent is also a mild agent to transfer an alkyl group to an enone in the presence of Me3SiCl. The alkyltitanium-based catalytic reagent selectively reacts with an allylic phosphate rather than with an enone, while in the presence of a silicon activator, it reacts preferentially with the enone rather than with the phosphate. 1H NMR studies on a mixture of Me2CuLi and TiCl(O-i-Pr)3 provided information on reagent composition.
- Arai, Masayuki,Lipshutz, Bruce H.,Nakamura, Eiichi
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p. 5709 - 5718
(2007/10/02)
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- Copper-Catalyzed Reactions of Organotitanium Reagents. Highly SN2'- and Anti-Selective and Diastereo- and Chemoselective Alkylation of Allylic Chlorides and Phosphates
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Organotitanium reagents undergo Cu(I)-catalyzed SN2' substitution reactions with allylic chlorides and phosphates in a regio-, stereo-, and chemoselective manner: in the presence of Me3SiCl or Me3SiOSO2CF3, they undergo preferential conjugate addition to enones.
- Arai, Masayuki,Nakamura, Eiichi,Lipshutz, Bruce H.
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p. 5489 - 5491
(2007/10/02)
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- COPPER- AND NICKEL-CATALYSIS IN SN2'- AND SN2-REGIOSELECTIVE ALLYLATION OF ORGANOZINC REAGENTS
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Allylation of organozinc reagents in the presence of a copper catalyst takes place in a highly SN2'-selective manner, whereas that in the presence of a nickel catalyst occurs with excellent SN2-selectivity.
- Sekiya, Kouichi,Nakamura, Eiichi
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p. 5155 - 5156
(2007/10/02)
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