- Ring Expansion Fluorination of Unactivated Cyclopropanes Mediated by a New Monofluoroiodane(III) Reagent
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Herein, we report a new strategy for carbon?carbon bond scission and intramolecular ring expansion fluorination of unactivated cyclopropanes, which was accomplished with a new hypervalent fluoroiodane(III) reagent 1. This novel method delivers medicinally relevant 4-fully substituted fluoropiperidines in moderate to high yields with excellent regio- and diastereoselectivity. Reagent 1, which has an N-acetylbenziodazole framework, was readily synthesized via three steps in 76 % overall yield and was characterized by NMR spectroscopy and X-ray crystallography. Owing to the presence of a secondary I???O bonding interaction between the λ3-iodane atom and the carbonyl oxygen of the acetyl group of the N-acetylbenziodazole framework, 1 has excellent stability and can be stored at ambient temperature for 6 months without any detectable decomposition. Density functional theory calculations and experimental studies showed that the reaction proceeds via a carbocation intermediate that readily combines with a fluoride ion to generate the product.
- Chen, Ze,Du, Feng-Huan,Hu, Ze-Nan,Jia, Meng-Cheng,Ren, Jing,Zhang, Chi
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supporting information
p. 24171 - 24178
(2021/10/08)
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- Catalyst-Free Visible-Light-Mediated Iodoamination of Olefins and Synthetic Applications
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Herein we report a catalyst- and metal-free visible-light-mediated protocol enabling the iodoamination of miscellaneous olefins. This protocol is characterized by high yields under environmentally benign reaction conditions utilizing commercially available substrates and a green and biodegradable solvent. Furthermore, the protocol allows for late-stage functionalization of bioactive molecules and can be scaled to gram quantities of product, which offers manifold possibilities for further transformations, including morpholine, piperidine, pyrrolidine, and aziridine synthesis.
- Engl, Sebastian,Reiser, Oliver
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supporting information
p. 5581 - 5586
(2021/07/26)
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- Asymmetric Synthesis of β2-Aryl Amino Acids through Pd-Catalyzed Enantiospecific and Regioselective Ring-Opening Suzuki–Miyaura Arylation of Aziridine-2-carboxylates
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A Pd-catalyzed enantiospecific and regioselective ring-opening Suzuki–Miyaura arylation of aziridine-2-carboxylates was developed. The cross-coupling allows for the asymmetric preparation of enantioenriched β2-aryl amino acids, starting from co
- Takeda, Youhei,Matsuno, Tetsuya,Sharma, Akhilesh K.,Sameera,Minakata, Satoshi
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supporting information
p. 10226 - 10231
(2019/07/18)
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- Synthesis, Characterization, and Reactivity of an Ethynyl Benziodoxolone (EBX)-Acetonitrile Complex
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The synthesis of a crystalline ethynyl-1,2-benziodoxol-3(1H)-one (EBX)-acetonitrile complex is described. EBX has been widely used as an active species for a variety of reactions; however, its high instability has so far prevented its isolation. The EBX-acetonitrile is self-assembled into a double-layered honeycomb structure through weak hypervalent iodine secondary interactions and hydrogen bonding. The N-ethynylation of a variety of sulfonamides using the EBX-acetonitrile complex as a substrate under mild conditions is also described.
- Yudasaka, Masaharu,Shimbo, Daisuke,Maruyama, Toshifumi,Tada, Norihiro,Itoh, Akichika
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p. 1098 - 1102
(2019/05/16)
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- Mechanistic Insight into Palladium-Catalyzed Cycloisomerization: A Combined Experimental and Theoretical Study
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The cycloisomerization of enynes catalyzed by Pd(OAc)2 and bis-benzylidene ethylenediamine (bbeda) is a landmark methodology in transition-metal-catalyzed cycloisomerization. However, the mechanistic pathway by which this reaction proceeds has remained unclear for several decades. Here we describe mechanistic investigations into this reaction using enynamides, which deliver azacycles with high regio- and stereocontrol. Extensive 1H NMR spectroscopic studies and isotope effects support a palladium(II) hydride-mediated pathway and reveal crucial roles of bbeda, water, and the precise nature of the Pd(OAc)2 pre-catalyst. Computational studies support these mechanistic findings and lead to a clear picture of the origins of the high stereocontrol that can be achieved in this transformation, as well as suggesting a novel mechanism by which hydrometalation proceeds.
- Mekareeya, Aroonroj,Walker, P. Ross,Couce-Rios, Almudena,Campbell, Craig D.,Steven, Alan,Paton, Robert S.,Anderson, Edward A.
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supporting information
p. 10104 - 10114
(2017/08/03)
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- Sulfonyl Azides as Precursors in Ligand-Free Palladium-Catalyzed Synthesis of Sulfonyl Carbamates and Sulfonyl Ureas and Synthesis of Sulfonamides
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(Chemical Equation Presented). An efficient synthesis of sulfonyl carbamates and sulfonyl ureas from sulfonyl azides employing a palladium-catalyzed carbonylation protocol has been developed. Using a two-chamber system, sulfonyl azides, PdCl2, and CO gas, released ex situ from Mo(CO)6, were assembled to generate sulfonyl isocyanates in situ, and alcohols and aryl amines were exploited as nucleophiles to afford a broad range of sulfonyl carbamates and sulfonyl ureas. A protocol for the direct formation of substituted sulfonamides from sulfonyl azides and amines via nucleophilic substitution was also developed.
- Chow, Shiao Y.,Stevens, Marc Y.,Odell, Luke R.
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p. 2681 - 2691
(2016/04/26)
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- Carbon dioxide as a reversible amine-protecting agent in selective Michael additions and acylations
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Carbon dioxide can be used as a temporary protecting group for amines. A carbamic acid is formed reversibly when CO2 is bubbled through a solution of a sufficiently basic primary amine at room temperature and atmospheric pressure. This reaction is employed for the protection of the amine functionality in several reactions at room temperature where inter- or intramolecular selectivity is desired. The concept is demonstrated for the selective Michael additions to methyl acrylate of a normally less reactive sulfonamide in the presence of a strong amine nucleophile, or of a cyclic secondary amine in the presence of an aliphatic primary amine, or of a β-ketoester in the presence of amines. The selective acylation of an alcohol in the presence of an amine can be achieved under a CO2 atmosphere as well.
- Peeters, Annelies,Ameloot, Rob,De Vos, Dirk E.
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p. 1550 - 1557
(2013/09/24)
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- 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-promoted efficient and versatile aza-Michael addition
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A convenient and versatile method was developed for aza-Michael addition using a substoichiometric amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Various nitrogen nucleophiles were efficiently introduced to α,β-unsaturated carbonyl compounds employing 0.5 equiv of DBU. Furthermore, other heteroatomic nucleophiles could also be introduced successfully under the same reaction conditions.
- Yeom, Chang-Eun,Kim, Mi Jeong,Kim, B. Moon
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p. 904 - 909
(2007/10/03)
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- Titanium tetraiodide mediated reductive opening of aziridines, leading to the aldol and mannich-type reactions
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Reductive ring-opening of N-tosylazirindes was readily carried out with titanium tetraiodide to form the titanium enolates, which in turn were subjected to addition reaction with aldehydes or imines to give aldol or Mannich-type products in good yields.
- Shimizu, Makoto,Kurokawa, Hiroshi,Nishiura, Shuji
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- Reductive opening of aziridines with polymethylhydrosiloxane
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Regio and chemoselective reductive opening of aziridines is achieved using catalytic palladium on charcoal and polymethylhydrosiloxane (PMHS) as a soluble hydrogen source.
- Chandrasekhar,Ahmed, Moinuddin
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p. 9325 - 9327
(2007/10/03)
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