- Decarbonylation of phenylacetic acids by high valent transition metal halides
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Triphenylacetic acid underwent unusual decarbonylation when allowed to react with a series of halides of group 4-6 metals in their highest oxidation state, in dichloromethane at ambient temperature. Thus, the reaction of CPh3COOH with MoCl5, in 1:1 molar ratio, afforded the trityl salt [CPh3][MoOCl4], 1, in 79% yield, while the 1:2 reaction of CPh3COOH with NbF5 afforded [CPh3][NbF6], 2, in 70% yield, NbOF3 being the metal co-product. CPh3COOH reacted with NbCl5, TiF4 and WOCl4 to give mixtures of compounds, however the cation [CPh3]+ was NMR identified in each case. [CPh3][NbCl6], 3, was isolated from NbCl5 and CPh3COCl, prior to being generated from CPh3COOH and PCl5. The reaction of CPh3COOH with TiCl4 was non-selective, and the salt [CPh3][Ti2Cl8(μ-κ2-O2CCPh3)], 4, was obtained in 18% yield. The decarbonylation reactions of CMePh2COCl and CMe2PhCOCl by means of NbCl5 led to the indanes 5a-b, which were isolated in 79-97% yields after hydrolysis of the mixtures and subsequent alumina filtration of the organic phases. The reactions of CH(Ph)2COOH with NbCl5 and WCl6 afforded NbCl4(OOCCHPh2), 6, and CHPh2COCl, respectively, as the prevalent species. CPh2(CH2CH2Br)COOH did not undergo CO release when allowed to interact with WCl6, instead selective intramolecular condensation to C(Ph)2C(O)OCH2CH2, 7, occurred. MeCCCOOH underwent hydrochlorination by WCl6 to give MeC(Cl)CHCOOH, 8, in 72% yield. All the products were fully characterized by elemental analysis, IR and multinuclear NMR spectroscopy. In addition, the solid state structures of 1, 2, 4, 7, and 8 were elucidated by X-ray diffraction.
- Bartalucci, Niccolò,Marchetti, Fabio,Zacchini, Stefano,Pampaloni, Guido
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p. 5725 - 5734
(2019/05/10)
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- Synthesis of β,β-disubstituted γ-butyrolactones by chemo-selective oxidation of 1,4-diols and γ-hydroxy olefins with rucl3/NaIO4
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Substituted γ-butyrolactones represent an important group of structural fragments commonly found in natural products, receptor ligands, and drug molecules. Interest in preparing a library of substituted γ-butyrolactones and finding that limited routes to β-substituted lactones exist, led to the development of an efficient approach for the synthesis of β,β-disubstituted γ-butyrolactones. Readily prepared substituted 1,4-diols and γ-hydroxy olefins were treated with the -RuCl3/NaIO4 oxidation system to provide the target β,β-disubstituted γ-butyrolactones in modest to good yields. The reaction goes through a lactol intermediate that was isolated and characterized for selected compounds. The approach supplies an efficient and versatile method for the synthesis of these important heterocyclic structures. Importantly, the present work is the first report that demonstrates the ability of RuCl3/NaIO4 to selectively oxidize primary hydroxyl groups in the presence of secondary alcohols to prepare lactones in good yields.
- Gao, Rong,Fan, Rong,Canney, Daniel J.
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p. 661 - 665
(2015/03/14)
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- Thermal rearrangement of phenyl-substituted ketene ethylene acetals
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Thermal rearrangement of mono-, di-, and triphenyl-substituted ketene ethylene acetals was studied. Pyrolysis of all of these acetals provided phenyl-substituted tetrahydro-2-furanones as a major product. The more phenyl groups substitute on the ketene acetal skeleton, the lower reaction temperature was required for the rearrangement. In the cases of the diphenylketene acetals at high temperatures, fragmentation products, such as fluorene and benzophenone, probably derived from dipheylcarbene via diphenylketene, were observed.
- Oda, Mitsunori,Morimoto, Kazuo,Thanh, Nguyen Chung,Ohta, Reina,Kuroda, Shigeyasu
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p. 1673 - 1680
(2007/10/03)
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- Control of Product in the Reaction of Tributyltin ω-Haloalkoxide (n-Bu3SnO(CH2)nX) with Diphenylketene
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The reaction of tributyltin ω-haloalkoxide with diphenylketene gave cyclic ketene acetals and/or lactones, and the ratio of these products were controled by the number of methylene groups and by the addition of Lewis base in the reaction system.Moreover, the direct cycloaddition of diphenylketene with cyclic ethers proceeded in high yields, catalyzed by organotin halide-Lewis base complexes.
- Shibata, Ikuya,Baba, Akio,Matsuda, Haruo
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p. 4000 - 4002
(2007/10/02)
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- Regioselectivity in Nickel(II)-Mediated Oxidations of Diols
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Oxidations of 2- and 4-substituted 1,4-butanediols to their corresponding γ-butyrolactones by the combination of molecular bromine and nickel(II) alkanoate occur with a high degree of regioselectivity.The influence of the alkanoate ligand, of substituents at the 2-position of 1,4-butanediols, and of solvent on oxidation regiocontrol is examined, and comparison of regioselectivity in diol oxidations is made with representative conventional oxidative methods.Regiocontrol in nickel(II)-mediated reactions is proposed to be derived from steric constraints for oxidativehydrogen transfer to the alkanoate ligand of nickel(II) in the diol-associated complex.Alternate use of cobalt(II) alkanoates provides regiocontrol in diol oxidations that is comparable or superior to that obtained with nickel(II) alkanoates in bromine oxidations.
- Doyle, Michael P.,Dow, Robert L.,Bagheri, Vahid,Patrie, William, J.
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p. 476 - 480
(2007/10/02)
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- Reversal of Regioselectivity in the Reduction of gem-Disubstituted Cyclic Carboxylic Acid Anhydrides
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The regioselective partial reduction of gem-disubstituted cyclic carboxylic acid anhydrides to the corresponding γ-lactones with LiAlH4 or NaBH4 is almost completely reversed when potassium tri-s-butylborohydride is used as the reducing agent.
- Morand, Peter,Salvator, Judith,Kayser, Margaret M.
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p. 458 - 459
(2007/10/02)
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- STERIC SELECTIVITY IN OXIDATION OF DIOLS
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Oxidations of 2,2-disubstituted-1,4-butenediols by the combination of nickel(II) bromide and benzoyl peroxide and by trityl tetrafluoroborate produce β,β-disubstituted-γ-butyrolactones with exceptional selectivity.
- Doyle, Michael P.,Dow, Robert L.,Bagheri, Vahid,Patrie, William J.
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p. 2795 - 2798
(2007/10/02)
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