- Alkylation of Allylic Derivatives. 9. On the Stereochemistry of Alkylation of Acyclic Allylic Alcohols by the Murahashi Method
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The stereochemistry of alkylation of optically active trans-α-methyl-γ-phenylallyl alcohol (3-OH) by the Murahashi procdeure has been investigated.Alkylation with n-butyllithium results in almost exclusive syn γ-alkylation.With methyllithium, syn γ-alkylation also predominates.The syn stereochemistry in this acyclic system is opposite from that observed earlier in cyclic systems.Mechanistic implications of this reversal of stereochemistry are discussed.
- Goering, Harlan L.,Tseng, Chung Chyi
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- Nickel-Catalyzed Denitrated Coupling Reaction of Nitroalkenes with Aliphatic and Aromatic Alkenes
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A simple and practical denitrated coupling reaction of nitroalkenes with various alkenes using a nickel catalyst and triethoxysilane [(EtO)3SiH] as reducing agent was achieved. Under mild reaction conditions, both aliphatic and aromatic alkenes could react with nitroalkenes to obtain a series of olefins with different functional groups in satisfactory yields under an air atmosphere, which were previously difficult or impossible to access. (Figure presented.).
- Zhang, Na,Quan, Zheng-Jun,Wang, Xi-Cun
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supporting information
p. 3179 - 3183
(2016/10/21)
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- Peroxide promoted tunable decarboxylative alkylation of cinnamic acids to form alkenes or ketones under metal-free conditions
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A tunable decarboxylative alkylation of cinnamic acids with alkanes was developed to form alkenes or ketones under transition metal-free conditions. In the presence of DTBP or DTBP/TBHP, the reaction gave alkenes and ketones respectively via a radical mechanism in moderate to good yields. This journal is
- Ji, Jing,Liu, Ping,Sun, Peipei
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supporting information
p. 7546 - 7549
(2015/05/04)
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- Copper catalyzed direct alkenylation of simple alkanes with styrenes
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A novel Cu-catalyzed direct alkenylation of simple alkanes with styrenes was described. In the presence of a catalytic amount of Cu(OTf)2, a diverse range of alkenes undergo coupling with cycloalkanes to produce (E)-alkyl alkenes. This transformation is proposed to proceed via a radical process. This journal is the Partner Organisations 2014.
- Zhu, Yefeng,Wei, Yunyang
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p. 2379 - 2382
(2014/05/20)
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- Synthesis of (S)-imperanene by using allylic substitution
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(Chemical Equation Presented) Synthesis of (S)-imperanene (1) was studied by using copper-assisted allylic substitution of ArCH=CHCH(L)CH2Ar (L: leaving group) and (i-PrO)Me2SiCH2MgCl. Preliminary substitution between PhCH=CHCH(L)Me (L = AcO, PivO, MeOCO2, (2-Py)CO2) and Bu copper reagents derived from BuMgX (X = Br, Cl) and CuBr·Me2S or CuCl in 1:1-40:1 ratios suggested acetate 28 as the best substrate. To prepare 28, kinetic resolution of racemic (E)-TMSCH=CHCH(OH)CH2Ar2 (Ar2 = (p-TBSO)(m-MeO)C6H3) carried out by using the asymmetric epoxidation with (-)-DIPT afforded the corresponding epoxy alcohol and (S)-allylic alcohol. After separation by chromatography, these products were converted to (S,E)-Bu3SnCH=CHCH(OH)CH2Ar2, which upon palladium-catalyzed coupling with Ar2-I followed by acetylation gave 28 (95-98% ee). Substitution of 28 with (i-PrO)Me 2SiCH2MgCl and CuBr·Me2S in a 4:1 ratio at 0°C proceeded cleanly to produce 29 with 100% inversion in 92% yield. Finally, Tamao oxidation furnished 1.
- Takashima, Yuji,Kobayashi, Yuichi
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scheme or table
p. 5920 - 5926
(2009/12/26)
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- Alkylation of Allylic Derivatives. 11. Copper(I)-Catalyzed Cross Coupling of Allylic Carboxylates with Grignard Reagents
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Reactions of allylic carboxylates with Grignard reagents containing catalytic amounts (1-10 mol percent) of cuprous salts give high yields of cross-coupled products.With alkyl Grignard reagents, regiochemistry can be controlled by choice of cuprous salt.With cuprous halides, little regiospecificity is observed.There is a small excess of γ-coupling in unbiased systems such as 5-methyl-2-cyclohexenyl (1), 2-cyclohexenyl (3), and β-phenylallyl (5) carboxylates.With CuCN, complete regiospecificity (exclusive γ-coupling) is observed with all alkyl Grignard reagents in unbiased systems, and with n-butylmagnesium halide >97percent γ-coupling results with α-methyl-γ-phenylallyl pivalate (7-OPiv) which is biased in favour of coupling at the α-position.In sharp contrast to alkyl Grignard reagents, phenyl and vinyl Grignard reagents containing CuCN show no regiospecificity.
- Tseng, Chung Chyi,Paisley, Steven D.,Goering, Harlan L.
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p. 2884 - 2891
(2007/10/02)
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- Alkylation of Allylic Derivates. 4. On the Mechanism of Alkylation of Allylic N-Phenylcarbamates with Lithium Dialkylcuprates
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Alkylation of allylic N-phenylcarbamates by deprotonation, complexation with CuI in THF, and addition of 1 equiv of RLi results in syn γ-alkylation in both cyclic and acyclic systems.This procedure gives higher stereo- and regiospecificity than when allylic N-phenylcarbamates are reacted with 3 equiv of etheral LiCuR2.A mechanism is presented which incorporates an intramolecular oxidative addition leading to a ?-allyl complex (3) which undergoes reductive elimination to give the syn γ-alkylation product.
- Goering, Harlan L.,Kantner, Steven S.,Tseng, Chung Chyi
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p. 715 - 721
(2007/10/02)
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- Alkylation of Allylic Derivatives. 3. The Regiochemistry of Alkylation of the Isomeric trans-α,γ-Methylphenylallyl Acetates with Lithium Dialkyleuprates
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Alkylation of the isomeric trans-α,γ-methylphenylallyl acetates (1-OAc and 2-OAc) with lithium dimethylcuprate or di-n-butylcuprate is regioselective but not regiospecific.Both isomers give essentially the same product mixture which contains 95percent of the trans conjugated alkylation product (3).The starting acetates do not rearrange under the conditions for these reactions.These results show that the isomeric acetate give the same product-forming intermediate(s).Presumably the key intermediate that is common to the two isomers is a ?-allyl copper(III).
- Goering, Harlan N.,Seitz, Earl P.,Tseng, Chung Chyi
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p. 5304 - 5308
(2007/10/02)
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