- Palladium(I) Carbonyl Cation-Catalyzed Carbonylation of Olefins and Alcohols in Concentrated Sulfuric Acid
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A new palladium catalyst was found to exhibit high catalytic activity for carbonylation of olefins and alcohols. cyclo-Bis(μ-carbonyl)dipalladium(I) cation (1) with bridging CO ligands is formed by reductive carbonylation of palladium sulfate, PdSO4, in concentrated H2SO4. When an olefin or alcohol is added, complex 1 changes to a new complex (2) with terminal CO ligands, and tertiary carboxylic acids are obtained in high yields at room temperature and atmospheric pressure of CO. IR and 13C NMR studies suggest that complex 2 may be tentatively formulated to be [Pd2(CO)2]2+, in which the terminal CO ligands are chemically equivalent. Complex 1 is a catalyst precursor, and complex 2 functions as an active species for the carbonylation of olefins and alcohols. The catalytic behavior of the palladium carbonyl catalyst supports the recently proposed reaction mechanism involving an olefin-metal-CO complex as an intermediate for the catalytic carbonylation of olefins and alcohols in strongly acidic solution.
- Xu, Qiang,Souma, Yoshie,Umezawa, Junya,Tanaka, Mutsuo,Nakatani, Hisako
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- Palladium-catalyzed 2-pyridylmethyl-directed β-C(sp3)–H activation and cyclization of aliphatic amides with gem-dibromoolefins: A rapid access to γ-lactams
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The direct Pd-catalyzed β-C(sp3)–H activation and cyclization of aliphatic amides bearing a removable 2-pyridylmethyl directing group with gem-dibromoolefins is described for the first time to construct a variety of γ-lactams. The resulting products with Z- and E-configurations can be easily separated and purified after the reaction, demonstrating the effectiveness and applicability of the method herein developed.
- Zhou, Danni,Wang, Chunxia,Li, Mingliang,Long, Zheng,Lan, Jingbo
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supporting information
p. 191 - 193
(2017/11/17)
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- Method for the Production of Mixtures Containing Tertiary Isononanoic Acids Based on 2-Ethylhexanol
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A process for producing a mixture comprising tertiary isononanoic acids proceeding from 2-ethylhexanol is characterized in that 2-ethylhexanol is (a) reacted at a temperature of 0° C. to 40° C. with a mixture of concentrated formic acid and a concentrated Br?nsted acid, wherein 2 to 10 mol of formic acid are used per mole of 2-ethylhexanol and the concentrated Br?nsted acid is used in an amount that corresponds to 6 to 90 mol of protons per mole of 2-ethylhexanol. The resulting reaction mixture from step (a) is subsequently (b) brought into contact with water, and the mixture comprising tertiary isononanoic acids formed according to step b) is removed.
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Paragraph 0038
(2017/07/14)
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- Nickel-catalyzed directed sulfenylation of sp2 and sp3 C-H bonds
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Directed sulfenylation of both sp2 and sp3 C-H bonds was achieved through nickel catalyzed directed C-S bond formation, giving the desired product in good to excellent yield (up to 90%). Other metal cations, including Cu, Fe, Pd, Rh, Ru and Co, gave almost no reaction under identical conditions, which highlighted the unique reactivity of this Ni system.
- Ye, Xiaohan,Petersen, Jeffrey L.,Shi, Xiaodong
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supporting information
p. 7863 - 7866
(2015/05/13)
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- Sulfoximine assisted Pd(II)-catalyzed bromination and chlorination of primary β-C(sp3)-H bond
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S-Methyl-S-2-pyridyl-sulfoximine (MPyS) directed bromination and chlorination of the 1°-β-C(sp3)-H bond of MPyS-N-amides is realized under the influence of N-Br/Cl-phthalimides and a Pd(II)-catalyst. The sequential halogenation and acetoxylation of α-dimethyl MPyS-N-amides constructs highly functionalized α-trisubstituted aliphatic acid derivatives. The MPyS directing group is cleaved from the halogenated products and recovered. (Chemical Equation Presented).
- Rit, Raja K.,Yadav, M. Ramu,Ghosh, Koushik,Shankar, Majji,Sahoo, Akhila K.
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supporting information
p. 5258 - 5261
(2015/01/09)
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- A New Gold Catalyst: Formation of Gold(I) Carbonyl, [Au(CO)n]+ (n = 1, 2), in Sulfuric Acid and Its Application to Carbonylation of Olefins
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A new gold catalyst, [Au(CO)n]+ (n = 1, 2), was synthesized by using a facile method from commercial gold(III) oxide, Au2O3, in concentrated H2SO4, which exhibits high catalytic activity for carbonylation of olefins. The gold monocarbonyl [Au(CO)]+ (1) and dicarbonyl [Au(CO)2]+ (2) cations coexist in H2SO4 solution, the former of which is much more stable than the latter. Both of the carbonyls show IR spectra of vCO (2194, 2208 cm-1) higher than that of free CO (2143 cm-1), indicating nonclassical (σ-only) gold-CO bonding. The gold carbonyl complexes coexisting in the concd H2SO4 solution exhibit a single resonance in the 13C NMR spectrum at 171 ppm at ambient temperature and pressure, reflecting rapid CO exchange between 1 (164 ppm) and 2 (175 ppm). The nonclassical gold(I) carbonyl solution worked as an excellent catalyst, with which olefins reacted with CO to give tert-carboxylic acids in good yields at room temperature and atmospheric pressure. The gold(I) dicarbonyl cation 2 was found to function as an active species for the carbonylation. An olefin-gold(I)-carbonyl complex was proposed as a possible intermediate in the metal carbonyl-catalyzed carbonylation in the strongly acidic medium.
- Xu, Qiang,Imamura, Yuki,Fujiwara, Masahiro,Souma, Yoshie
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p. 1594 - 1598
(2007/10/03)
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- C-C Cleavage of Ionized Carboxylic Acids as Reversal of Additions of Alkyl Radicals to Protonated α,β-Unsaturated Acids. - On the Role of Enol Cation Radicals as Reactive Intermediates in Isomerization/Dissociation Reactions in the Gas Phase
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Metastable molecular ions of pivalic acid (5) and 2-methylbutanoic acid (8) decompose unimolecularly via methyl loss, thereby specifically generating protonated crotonic acid (5 -> 6) and protonated methacrylic acid (8 -> 7), respectively.The investigation of 13C and 2H labelled isotopomers of 5 and 8 together with MNDO calculations of parts of the potential energy surface of 8 reveals that C-C cleavage requires the presence of enol cation radicals of the general structure 1 as reactive intermediates.Cation radicals of carboxylic acids in which the radical centre is not adjacent to the protonated carboxylic function, as for example in 3, do not serve as actual precursors for the C-C cleavage; instead, isomerization to 1 is required.The fact that enol cation radicals, i.e. 1, 13 and 14, are of essential importance in the splitting of C-C bonds of ionized carboxylic acids is a direct consequence of the fact that these dissociations can be viewed as the reversal of addition of (nucleophilic) alkyl radicals to protonated α,β-unsaturated acids, which proceeds preferentially via enol cation radical intermediates.
- Weiske, Thomas,Halim, Herman,Schwarz, Helmut
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p. 495 - 509
(2007/10/02)
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