- Blue LED Irradiation of Iodonium Ylides Gives Diradical Intermediates for Efficient Metal-free Cyclopropanation with Alkenes
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A facile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and β-dicarbonyl-derived iodonium ylides are irradiated with light from blue LEDs. This metal-free synthesis gives cyclopropanes in yields
- Chidley, Tristan,Jameel, Islam,Rizwan, Shafa,Peixoto, Philippe A.,Pouységu, Laurent,Quideau, Stéphane,Hopkins, W. Scott,Murphy, Graham K.
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supporting information
p. 16959 - 16965
(2019/11/11)
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- Difluoro methylation reagent, preparation method and application thereof (by machine translation)
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The present invention discloses a two-trifluoromethylation of the reagent, preparation method and application thereof. The invention [...] methylation reagent preparation process is simple, high yield; and the reagent can be a more moderate, high-efficiently the sulfonic acid, alcohol, carbonyl and on the α carbon atom of the difluoromethyl. (by machine translation)
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Paragraph 0125; 0126; 0127
(2017/10/23)
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- Generation of Aryl Radicals through Reduction of Hypervalent Iodine(III) Compounds with TEMPONa: Radical Alkene Oxyarylation
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A novel method for selective generation of aryl radicals from diaryliodonium salts and iodanylidene malonates with sodium 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPONa) as a single-electron transfer (SET) reducing reagent is described. In the presence of various alkenes, aryl radicals formed after SET-reduction of hypervalent iodine compounds undergo alkene addition and the adduct radicals that are thus generated are efficiently trapped by the concomitantly generated TEMPO radical to eventually afford oxyarylated products in moderate to very good yields. The efficiency of aryl radical generation of various iodine(III) reagents is studied and the generation of an iodanylidene malonate aryl radical is also investigated by computational methods.
- Hartmann, Marcel,Li, Yi,Mück-Lichtenfeld, Christian,Studer, Armido
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p. 3485 - 3490
(2016/03/05)
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- Nucleophilicity Parameters of Stabilized Iodonium Ylides for Characterizing Their Synthetic Potential
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Kinetics and mechanisms of the reactions of the β-dicarbonyl-substituted iodonium ylides 1(a-d) with several π-conjugated carbenium and iminium ions have been investigated. All reactions proceed with rate-determining attack of the electrophile at the nucleophilic carbon center of the ylides to give iodonium ions, which rapidly expel iodobenzene and undergo different subsequent reactions. The second-order rate constants k2 for the reactions of the iodonium ylides with benzhydrylium ions correlate linearly with the electrophilicity parameters E of the benzhydrylium ions and thus follow the linear free energy relationship log k(20 °C) = sN(N + E) (eq 1), where electrophiles are characterized by one parameter (E), while nucleophiles are characterized by two parameters: the nucleophilicity N and the susceptibility sN. The nucleophilicity parameters 4 + at the carbanionic center of Meldrum's acid or dimedone, respectively, reduces the nucleophilicity by approximately 10 orders of magnitude. The iodonium ylides 1(a-d) thus have nucleophilicities similar to those of pyrroles, indoles, and silylated enol ethers and, therefore, should be suitable substrates in iminium-activated reactions. Good agreement of the measured rate constant for the cyclopropanation of the imidazolidinone-derived iminium ion 10a with the iodonium ylide 1a with the rate constant calculated by eq 1 suggests a stepwise mechanism in which the initial nucleophilic attack of the iodonium ylide at the iminium ion is rate-determining. The reaction of cinnamaldehyde with iodonium ylide 1a catalyzed by (5S)-5-benzyl-2,2,3-trimethyl-imidazolidin-4-one (11a, MacMillan's first-generation catalyst) gives the corresponding cyclopropane with an enantiomeric ratio of 70/30 and, thus, provides proof of principle that iodonium ylides are suitable substrates for iminium-activated cyclopropanations.
- Chelli, Saloua,Troshin, Konstantin,Mayer, Peter,Lakhdar, Sami,Ofial, Armin R.,Mayr, Herbert
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p. 10304 - 10313
(2016/09/03)
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- Simplified synthesis of aryliodonium ylides by a one-pot procedure
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A simplified synthesis of iodonium ylides was developed by the one-pot synthesis of phenyliodonium-(5-[2,2-dimethyl-1,3-dioxane-4,6-dione]) ylide as a model system. Such ylides are excellent precursors for nucleophilic no-carrier-added 18F-fluorination of even non-activated arenes. The suitability of the one-pot method is exemplified for several electron rich iodonium ylides. Further, the syntheses of 2-, 3- and 4-bromophenyliodonium-(5- [2,2-dimethyl-1,3-dioxane-4,6-dione]) ylide, and 4-iodophenyliodonium-(5-[2,2- dimethyl-1,3-dioxane-4,6-dione]) ylide, two novel precursors for 4-[ 18F]fluoro-1-halobenzene, are reported.
- Cardinale, Jens,Ermert, Johannes
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supporting information
p. 2067 - 2069
(2013/04/23)
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- General method for the synthesis of phenyliodonium ylides from malonate esters: Easy access to 1,1-cyclopropane diesters
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(Chemical Equation Presented) A general method to access phenyliodonium ylides from malonates has been developed. These ylides provide easy access to a variety of useful 1,1-cyclopropane diesters using rhodium or copper catalysis. Moreover, the iodonium ylide of dimethyl malonate was obtained in 78% yield using improved conditions that involve a simple filtration step to isolate the desired product. This ylide was shown to be a safer and convenient alternative to the corresponding diazo compound and a very efficient way to 1,1-cyclopropane diesters when used with a catalytic amount of Rh2(esp)2.
- Goudreau, Sébastien R.,Marcoux, David,Charette, André B.
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supporting information; experimental part
p. 470 - 473
(2009/04/10)
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- Rhodium(II)-catalyzed olefin cyclopropanation with the phenyliodonium ylide derived from Meldrum's acid
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The phenyliodonium ylide 3a derived from Meldrum's acid reacts with olefins in the presence of Rh(II) carboxylate catalysts to afford cyclopropanes. The reaction is stereospecific. Enantioselectivities of up to 63% have been observed for the cyclopropanation of pent-1-ene. No 1,3-cycloadducts are formed between 3a and polarized olefins such as furan or 2,3-dihydrofuran.
- Mueller, Paul,Allenbach, Yves,Robert, Estelle
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p. 779 - 785
(2007/10/03)
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