- Urea-Catalyzed Vinyl Carbocation Formation Enables Mild Functionalization of Unactivated C-H Bonds
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Herein we report the 3,5-bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C-H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C-H insertion and Friedel-Crafts re
- Bagdasarian, Alex L.,Popov, Stasik,Wigman, Benjamin,Wei, Wenjing,Lee, Woojin,Nelson, Hosea M.
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- Zinc Powder Catalysed Formylation and Urealation of Amines Using CO2 as a C1 Building Block?
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Transformation of CO2 into valuable organic compounds catalysed by cheap and biocompatible metal catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of amines with CO2 and (EtO)3SiH under solvent free condition. Using 2 molpercent zinc powder as the catalyst, a series of secondary amines, both the aromatic ones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines were used as the substrates, the reactions produce urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic activity. The analysis on the reactants/products mixture after filtering out the zinc powder showed the zinc concentration in the mixture is low to 1 ppm. The pathways for the formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.
- Du, Chongyang,Chen, Yaofeng
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p. 1057 - 1064
(2020/06/30)
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- Ortho-substituent effects on diphenylurea packing motifs
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Hydrogen bonding between urea groups is a widely used motif in crystal engineering and supramolecular chemistry studies. In an effort to discern how the steric and electronic properties of substituents affect the molecular conformation and crystal packing
- Solomos, Marina A.,Watts, Taylor A.,Swift, Jennifer A.
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p. 5065 - 5072
(2018/03/01)
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- Synthesis of functionalized carbamates through a palladium-catalyzed reductive carbonylation of substituted nitrobenzenes
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The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1,10-phenanthroline)2(triilate}2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. The selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion of the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid functions. VCH Verlagsgesellschaft mbH.
- Wchman, Petra,Borst, Leo,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
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- REARRANGEMENT OF N-(TRIFLUOROMETHYL)ANTHRANILOYL FLUORIDE TO 2-(TRIFLUOROMETHYL)ANILINE - KINETIC AND MECHANISTIC OBSERVATIONS
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Pseudo first order rate constants for the rearrangement of N-(trifluoromethyl)anthraniloyl fluoride (2) to N-carbamoyl fluoride (3) in anhydrous HF have been determined.Increasing HF levels accelerate this process, but increasing KF concentrations retard the reaction.An ionic species has been proposed as the intermediate in the suggested mechanism.Further reaction of 3 with HF proceeded to give 2-(trifluoromethyl)aniline hydrofluoride (4) via an unprecedented expulsion of carbonyl fluoride.
- Lin, Henry C.,Cotter, Byron R.,Bieron, Joseph F.,Krishnamurti, Ramesh
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p. 107 - 116
(2007/10/02)
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