- Room-Temperature Benzylic Alkylation of Benzylic Carbonates: Improvement of Palladium Catalyst and Mechanistic Study
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The palladium catalyst for the nucleophilic substitution of benzyl carbonates was improved by using 1,1′-bis(diisopropylphosphino)ferrocene (DiPrPF) as the ligand. The [Pd(η3-C3H5)(cod)]BF4-DiPrPF catalyst allows the benzylic substitution with soft carbanions to proceed even at 30 °C, affording the desired products in high yields (up to 99% yield). Thermally unstable pyridylmethyl esters are employable as the electrophilic substrates for the benzylic alkylation with the improved catalyst. Furthermore, we investigated the mechanism of the catalytic benzylic alkylation by means of DiPrPF ligand. The palladium(0) complex bearing DiPrPF activates the benzylic C-O bond to form the (benzyl)palladium(II) intermediate at room temperature. The coordination mode of the benzyl ligand would be equilibrium between the η1- and η3-manner. The nucleophile would preferentially react with the η3-benzyl ligand to give the desired product.
- Kuwano, Ryoichi,Yokogi, Masashi,Sakai, Ken,Masaoka, Shigeyuki,Miura, Takashi,Won, Sungyong
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p. 1568 - 1579
(2019/09/04)
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- Cleavage of C–C and C–O Bonds to Form C–C Bonds: Direct Cross-Coupling between Acetylenic Alcohols and Benzylic Carbonates
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A palladium-catalyzed cross-coupling reaction between C(sp) and C(sp3) centers was achieved in excellent yields via C–C bond cleavage and C–O bond cleavage. This procedure uses relatively stable acetylenic alcohols as reactants instead of unsta
- Mi, Zhiyuan,Tang, Jiahao,Guan, Zhipeng,Shi, Wei,Chen, Hao
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supporting information
p. 4479 - 4482
(2018/09/10)
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- Palladium-catalyzed benzylic substitution of benzyl carbonates with phosphorus nucleophiles
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A wide range of benzyl carbonates reacted with dimethyl phosphonate or diphenylphosphine oxide in the presence of the palladium catalyst, [Pd(η3-allyl)Cl]2DPEphos, to give dimethyl benzylphosphonates and benzyldiphenylphosphine oxides in high yields. The catalytic phosphonylation was applied to the one-pot synthesis of alkenes from the benzyl esters.
- Makida, Yusuke,Usui, Kazumi,Ueno, Satoshi,Kuwano, Ryoichi
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supporting information
p. 1814 - 1817
(2017/11/23)
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- A general Pd-catalyzed α- And γ-benzylation of aldehydes for the formation of quaternary centers
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A palladium-catalyzed benzylation of α-branched aldehydes has been developed using benzyl methyl carbonates. The method gives access to congested quaternary centers in the vicinity of one of the most sensitive carbonyl functionalities and displays unprecedented generality with respect to both coupling partners. Evidence for the direct involvement of a Pd-η3-benzyl intermediate is provided. Extension of this strategy to the γ-benzylation of α,β-unsaturated aldehydes is further demonstrated.
- Franzoni, Ivan,Guénée, Laure,Mazet, Clément
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supporting information
p. 6338 - 6343
(2015/06/08)
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- An easy base-assisted synthesis of unsymmetrical carbonates from alcohols with dimethyl carbonate
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A simple and convenient base-mediated synthesis of asymmetrical carbonates from alcohols with dimethyl carbonate is described. The reaction is remarkably influenced by the strength of the base employed and potassium t-butoxide was found to be best promote
- Kumar, Subodh,Jain, Suman L.
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p. 791 - 795
(2014/05/20)
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- Non-symmetrical dialkyl carbonate synthesis promoted by 1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride
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An efficient synthesis of non-symmetrical dialkyl carbonates promoted by 1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride ionic liquid as a reaction medium is described. The ionic liquid can easily be recovered and reused several times without sig
- Kumar, Subodh,Jain, Suman L.
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supporting information
p. 3057 - 3061
(2013/10/01)
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- Palladium-catalyzed direct benzylation of azoles with benzyl carbonates
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"Chemical Equation Presented" The direct aromatic sp2 C-H benzylation of azole compounds with benzyl carbonates proceeds efficiently in the presence of a Pd2(dba)3/dppp catalyst system and KaOAc as a base to afford the corresponding diarylmethanes in good yields. In addition, the same palladium catalyst enables the direct benzylic sp3 C-H benzylation with the second benzyl carbonates without employing any external base.
- Mukai, Tomoya,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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supporting information; experimental part
p. 1360 - 1363
(2010/05/19)
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- Radicals from fragmentation of benzyloxymethoxycarbenes in solution
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2-Benzyloxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazolines, including the parent as well as p-substituted analogues, undergo thermolysis at 100°C in benzene to afford a mixture of products. Two primary fragmentations of the oxadiazolines were identified. The major pathway involves 1,3-dipolar cycloreversion to N2 and the corresponding carbonyl ylides. The latter dissociate to acetone and the corresponding benzyloxy(methoxy)carbenes, which undergo fragmentation to ArCH2 and MeOCO radical pairs that recombine to afford methyl arylacetates. Carbene dimers were not observed, showing that the fragmentation process is faster than carbene dimerization. A second fragmentation pathway observed for the oxadiazolines is an alternative cycloreversion to the corresponding benzyl methyl carbonate and 2- diazopropane. Products from diazopropane included acetone azine and, in some instances, traces of propene.
- Merkley, Nadine,El-Saidi, Manal,Warkentin, John
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p. 356 - 361
(2007/10/03)
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