- On the mechanism of cytochrome P450-catalyzed oxidations: Reaction of a new enzyme model with a radical clock
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trans-2-Phenyl-methylcyclopropane was oxidized using PhIO and a P450 enzyme model carrying a SO3- ligand coordinating to iron. Analysis of the product distribution revealed a ratio of 9:1 of the non-rearranged cyclopropyl methanol 18
- Sbaragli, Laura,Woggon, Wolf-D.
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Read Online
- Radical clock substrate probes and kinetic isotope effect studies of the hydroxylation of hydrocarbons by methane monooxygenase
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Four mechanistic probes, trans-2-phenylmethylcyclopropane (1), 2,2-diphenylmethylcyclopropane (2), trans-1,2-dimethylcyclopropane (3), and bicyclo[2.1.0]pentane (4), were used as substrates to investigate the possible formation of radical intermediates in
- Liu, Katherine E.,Johnson, Cathy C.,Newcomb, Martin,Lippard, Stephen J.
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Read Online
- Erratum: Cu-Catalyzed Three-Component Carboamination of Alkenes (J. Am. Chem. Soc. (2018) 140:1 (58?61) DOI: 10.1021/jacs.7b10529)
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Pages 59 and 60. We have identified an error in the structural analysis of compounds presented in our publication detailing. (Table presented).
- Gockel, Samuel N.,Buchanan, Travis L.,Hull, Kami L.
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supporting information
p. 6019 - 6020
(2021/05/13)
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- Donor-Acceptor Bicyclopropyls as 1,6-Zwitterionic Intermediates: Synthesis and Reactions with 4-Phenyl-1,2,4-triazoline-3,5-dione and Terminal Acetylenes
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The bicyclopropyl system activated by incorporation of donor and acceptor groups in the presence of Lewis acids was used as a synthetic equivalent of 1,6-zwitterions. Opening of both cyclopropane rings in 2′-aryl-1,1′-bicyclopropyl-2,2-dicarboxylates (D-A bicyclopropyl, ABCDs) in the presence of GaI3 + Bu4N+GaI4- results in 5-iodo-5-arylpent-2-enylmalonates as products of HI formal 1,6-addition to the bicyclopropyl system. The use of GaCl3 or GaBr3 as a Lewis acid and terminal aryl or alkyl acetylenes as 1,6-zwitterion interceptors allows the alkyl substituent to be grown to give the corresponding acyclic 7-chloro(bromo)-hepta-2,6-dienylmalonates. The reaction of ABCDs with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) catalyzed by Yb(OTf)3 also results in the opening of both cyclopropane rings. The reaction products are tetrahydropyridazine derivatives - (7,9-dioxo-1,6,8-triazabicyclo[4.3.0]non-3-en-2-ylmethyl)malonates - containing one more PTAD moiety in the malonyl group.
- Potapov, Konstantin V.,Denisov, Dmitry A.,Glushkova, Valeriia V.,Novikov, Roman A.,Tomilov, Yury V.
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p. 15562 - 15576
(2020/11/30)
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- Metal-free domino Cloke-Wilson rearrangement-hydration-dimerization of cyclopropane carbaldehydes: A facile access to oxybis(2-aryltetrahydrofuran) derivatives
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In this work, we have demonstrated a metal-free transformation of cyclopropane carbaldehydes to oxybis(2-aryltetrahydrofuran) derivatives via a domino Cloke-Wilson rearrangement-hydration-dimerization sequence. Commercially inexpensive p-toluene sulfonic acid (PTSA) was used as a Br?nsted acid catalyst, and reactions were conducted in an open-flask. Detection of reaction intermediates were carried to get an insight into the reaction pathway.
- Banerjee, Prabal,Dey, Raghunath,Rajput, Shruti
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- Regioselective Br?nsted Acid-Catalyzed Annulation of Cyclopropane Aldehydes with N′-Aryl Anthranil Hydrazides: Domino Construction of Tetrahydropyrrolo[1,2- a]quinazolin-5(1 H)ones
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A highly regioselective synthesis of tetrahydropyrrolo[1,2-a]quinazolin-5(1H)one derivatives was achieved by reacting cyclopropane aldehydes with N′-aryl anthranil hydrazides in the presence of p-toluene sulfonic acid (PTSA). The transformation involves domino imine formation and intramolecular cyclization to form 2-arylcyclopropyl-2,3-dihydroquinolin-4(1H)-one, followed by nucleophilic ring opening of the cyclopropyl ring to form desired tetrahydropyrrolo[1,2-a]quinazolin-5(1H)one in good to excellent yield with complete regioselectivity. This protocol tolerates a great variety of functional groups and thus provides a simple and step-efficient method for pyrroloquinazolinone synthesis.
- Banerjee, Prabal,Kaur, Navpreet,Singh, Priyanka
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p. 3393 - 3406
(2020/03/23)
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- Accessing dihydro-1,2-oxazine via cloke-wilson-type annulation of cyclopropyl carbonyls: application toward the diastereoselective synthesis of pyrrolo[1,2- b][1,2]oxazine
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A convenient additive-free synthesis of dihydro-4H-1,2-oxazines via a Cloke-Wilson-type ring expansion of the aryl-substituted cyclopropane carbaldehydes with the hydroxylamine salt is introduced. Comparatively less active cyclopropyl ketones also follow a similar protocol if supplemented by catalytic p-toluene sulfonic acid monohydrate. The transformation is performed in an open-to-air flask as it shows negligible sensitivity toward air/moisture. Dihydro-4H-1,2-oxazines when subjected to cycloaddition with the cyclopropane diester afford a trouble-free formulation of the valued hexahydro-2H-pyrrolo[1,2-b][1,2]oxazine derivatives. A cascade one-pot variant of this two-step strategy offers a comparable overall yield of the final product.
- Banerjee, Prabal,Kumar, Pankaj,Kumar, Rakesh
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p. 6535 - 6550
(2020/06/09)
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- Enantioselective Remote C(sp3)-H Cyanation via Dual Photoredox and Copper Catalysis
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The remote C(sp3)-H cyanation of carboxamides has been described by merging photoredox and copper catalysis in a site-selective and enantiocontrolled manner. The protocol is the integration of photoinduced and nitrogen-centered radical-mediated intermolecular hydrogen atom transfer with chiral copper-complex-catalyzed radical cyanation. This strategy gives enantio-enriched cyanated amides in high yields.
- Chen, Hui,Jin, Weiwei,Yu, Shouyun
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supporting information
p. 5910 - 5914
(2020/08/12)
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- A Vinyl Cyclopropane Ring Expansion and Iridium-Catalyzed Hydrogen Borrowing Cascade
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A vinyl cyclopropane rearrangement embedded in an iridium-catalyzed hydrogen borrowing reaction enabled the formation of substituted stereo-defined cyclopentanes from Ph* methyl ketone and cyclopropyl alcohols. Mechanistic studies provide evidence for the ring-expansion reaction being the result of a cascade based on oxidation of the cyclopropyl alcohols, followed by aldol condensation with the pentamethyl phenyl-substituted ketone to form an enone containing the vinyl cyclopropane. Subsequent single electron transfer (SET) to this system initiates a rearrangement, and the catalytic cycle is completed by reduction of the new enone. This process allows for the efficient formation of diversely substituted cyclopentanes as well as the construction of complex bicyclic carbon skeletons containing up to four contiguous stereocentres, all with high diastereoselectivity.
- Cheong, Choon Boon,Christensen, Kirsten E.,Donohoe, Timothy J.,Frost, James R.,Wübbolt, Simon
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supporting information
p. 11339 - 11344
(2020/05/25)
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- Cooperative NHC and Photoredox Catalysis for the Synthesis of β-Trifluoromethylated Alkyl Aryl Ketones
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Despite the great potential of radical chemistry in organic synthesis, N-heterocyclic carbene (NHC)-catalyzed reactions involving radical intermediates are not well explored. This communication reports the three-component coupling of aroyl fluorides, styrenes and the Langlois reagent (CF3SO2Na) to give various β-trifluoromethylated alkyl aryl ketones with good functional group tolerance in moderate to high yields by cooperative photoredox/NHC catalysis. The alkene acyltrifluoromethylation proceeds via radical/radical cross coupling of ketyl radicals with benzylic C-radicals. The ketyl radicals are generated via SET reduction of in situ formed acylazolium ions whereas the benzylic radicals derive from trifluoromethyl radical addition onto styrenes.
- D?ben, Nadine,Meng, Qing-Yuan,Studer, Armido
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supporting information
p. 19956 - 19960
(2020/09/04)
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- 5,6,7,8-Tetrahydro-1,6-naphthyridine Derivatives as Potent HIV-1-Integrase-Allosteric-Site Inhibitors
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A series of 5,6,7,8-tetrahydro-1,6-naphthyridine derivatives targeting the allosteric lens-epithelium-derived-growth-factor-p75 (LEDGF/p75)-binding site on HIV-1 integrase, an attractive target for antiviral chemotherapy, was prepared and screened for activity against HIV-1 infection in cell culture. Small molecules that bind within the LEDGF/p75-binding site promote aberrant multimerization of the integrase enzyme and are of significant interest as HIV-1-replication inhibitors. Structure-activity-relationship studies and rat pharmacokinetic studies of lead compounds are presented.
- Peese, Kevin M.,Allard, Christopher W.,Connolly, Timothy,Johnson, Barry L.,Li, Chen,Patel, Manoj,Sorensen, Margaret E.,Walker, Michael A.,Meanwell, Nicholas A.,McAuliffe, Brian,Minassian, Beatrice,Krystal, Mark,Parker, Dawn D.,Lewis, Hal A.,Kish, Kevin,Zhang, Ping,Nolte, Robert T.,Simmermacher, Jean,Jenkins, Susan,Cianci, Christopher,Naidu, B. Narasimhulu
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p. 1348 - 1361
(2019/02/24)
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- Metal-Free Ring Opening Cyclization of Cyclopropane Carbaldehydes and N-Benzyl Anilines: An Eco-Friendly Access to Functionalized Benzo[b]azepine Derivatives
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Herein, we report a p-toluenesulfonic acid (PTSA) initiated mild and user-friendly ring opening/domino ring opening cyclization reaction (depends on substituent present in N-benzyl aniline) of cyclopropane carbaldehyde and N-benzyl aniline towards the formation of substituted 4-amino butanal/2,3-dihydro-1H-benzo[b]azepine. The product dihydro-1H-benzo[b]azepine was also converted into the corresponding tetrahydro-1H-benzo[b]azepine. (Figure presented.).
- Dey, Raghunath,Banerjee, Prabal
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p. 2849 - 2854
(2019/04/26)
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- Synthesis of Photosensitive Cyclopropane-Containing Polymers
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New cyclopropyl methacrylate monomers were prepared, their radical polymerization was performed, and the composition and structure of the polymers obtained, containing reactive UV-sensitive fragments, were determined. Experiments on photochemical cross-li
- Guliyev,Rzayeva,Guliyev
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p. 1215 - 1222
(2019/11/03)
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- Enantioselective Copper-Catalyzed 1,5-Cyanotrifluoromethylation of Vinylcyclopropanes
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A copper-catalyzed enantioselective 1,5-cyanotrifluoromethylation of vinylcyclopropanes has been developed using a radical relay strategy. This asymmetric reaction has demonstrated high enantioselective control, broad substrate scope, and mild conditions. Initiated by the in situ generated CF3 radical from Togni's reagent, this method offers a new solution for remote enantioselective bifunctionalization of alkenes and thus provides a straightforward way for the synthesis of chiral CF3-containing internal alkenylnitriles.
- Zhang, Zi-Qi,Meng, Xiang-Yu,Sheng, Jie,Lan, Quan,Wang, Xi-Sheng
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supporting information
p. 8256 - 8260
(2019/10/16)
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- Asymmetric Reductive Carbocyclization Using Engineered Ene Reductases
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Ene reductases from the Old Yellow Enzyme (OYE) family reduce the C=C double bond in α,β-unsaturated compounds bearing an electron-withdrawing group, for example, a carbonyl group. This asymmetric reduction has been exploited for biocatalysis. Going beyond its canonical function, we show that members of this enzyme family can also catalyze the formation of C?C bonds. α,β-Unsaturated aldehydes and ketones containing an additional electrophilic group undergo reductive cyclization. Mechanistically, the two-electron-reduced enzyme cofactor FMN delivers a hydride to generate an enolate intermediate, which reacts with the internal electrophile. Single-site replacement of a crucial Tyr residue with a non-protic Phe or Trp favored the cyclization over the natural reduction reaction. The new transformation enabled the enantioselective synthesis of chiral cyclopropanes in up to >99 % ee.
- Heckenbichler, Kathrin,Schweiger, Anna,Brandner, Lea Alexandra,Binter, Alexandra,Toplak, Marina,Macheroux, Peter,Gruber, Karl,Breinbauer, Rolf
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supporting information
p. 7240 - 7244
(2018/06/15)
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- Lewis Acid Catalyzed Annulation of Cyclopropane Carbaldehydes and Aryl Hydrazines: Construction of Tetrahydropyridazines and Application Toward a One-Pot Synthesis of Hexahydropyrrolo[1,2- b]pyridazines
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In this report, a facile synthesis of tetrahydropyridazines via a Lewis acid catalyzed annulation reaction of cyclopropane carbaldehydes and aryl hydrazines has been demonstrated. Moreover, the generated tetrahydropyridazine further participated in a cycloaddition reaction with donor-acceptor cyclopropanes to furnish hexahydropyrrolo[1,2-b]pyridazines. We also performed these two steps in one pot in a consecutive manner. In addition, a monodecarboxylation reaction of hexahydropyrrolo[1,2-b]pyridazine was achieved with a good yield.
- Dey, Raghunath,Kumar, Pankaj,Banerjee, Prabal
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p. 5438 - 5449
(2018/05/28)
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- Exploitation of Cyclopropane Carbaldehydes to Prins Cyclization: Quick Access to (E)-Hexahydrooxonine and Octahydrocyclopenta[ b]pyran
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A single-step TiX4-mediated Prins-type cyclization of cyclopropane carbaldehydes with 3-buten-1-ol for the highly stereoselective construction of relatively strained (E)-hexahydrooxonines is reported. Switching the alcohol to 3-butyn-1-ol prompted a similar route, augmented by another cyclization within a nine-membered ring to afford a bicyclized product (4,4-dihalo-5-aryloctahydrocyclopenta[b]pyran). Easy transformation of the resulting geminal dihalide to a vinyl halide and a ketone further supplemented the substance of this approach.
- Kumar, Pankaj,Dey, Raghunath,Banerjee, Prabal
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p. 5163 - 5166
(2018/09/13)
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- Cu-Catalyzed Three-Component Carboamination of Alkenes
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Copper-catalyzed intermolecular carboamination of alkenes with α-halocarbonyls and amines is presented with 42 examples. Electron rich, electron poor, and internal styrenes, as well as α-olefins, are functionalized with α-halocarbonyls and aryl or aliphat
- Gockel, Samuel N.,Buchanan, Travis L.,Hull, Kami L.
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supporting information
p. 58 - 61
(2018/01/17)
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- A Stereoconvergent Cyclopropanation Reaction of Styrenes
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The first stereoconvergent cyclopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol en route to trans-cyclopropanes regardless of whether E- or Z-styrene substrates were utilized.
- del Hoyo, Ana M.,Herraiz, Ana G.,Suero, Marcos G.
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supporting information
p. 1610 - 1613
(2017/02/05)
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- Copper-Catalyzed Alkylation of Nitroalkanes with α-Bromonitriles: Synthesis of β-Cyanonitroalkanes
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Copper catalysis now enables the efficient C-alkylation of nitroalkanes with α-bromonitriles. Using a simple and inexpensive catalyst, this process provides access to β-cyanonitroalkanes. The method is highly tolerant of various functional groups and substitution patterns. These functionally dense products serve as orthogonally masked 1,3-diamines, which can be revealed selectively for access to differentially substituted diamines. These products can also be exploited for the formation of complex cyanoalkenes and 5-aminoisoxazoles.
- Shimkin, Kirk W.,Gildner, Peter G.,Watson, Donald A.
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p. 988 - 991
(2016/03/15)
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- Improved zinc-catalyzed simmons-smith reaction: Access to various 1,2,3-trisubstituted cyclopropanes
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The Simmons-Smith reaction of zinc carbenoids with alkenes is a powerful method to access cyclopropanes containing various substitution patterns. This work exploits the high reactivity of aryldiazomethanes toward zinc halides to generate aryl-substituted carbenoids catalytically. These carbenoids are able to cyclopropanate various alkenes diastereoselectively, including unfunctionalized substrates such as styrenes. The zinc catalyst can be modified to tolerate the use of free allylic alcohols.
- Levesque, Eric,Goudreau, Sebastien R.,Charette, Andre B.
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supporting information
p. 1490 - 1493
(2014/04/03)
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- Copper-catalyzed regio- and stereoselective intermolecular three-component oxyarylation of allenes
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A copper(II)-catalyzed intermolecular three-component oxyarylation of allenes using arylboronic acids as a carbon source and TEMPO as an oxygen source is described. The reaction proceeded under mild conditions with high regio- and stereoselectivity and functional group tolerance. A plausible reaction mechanism is proposed, involving carbocupration of allenes, homolysis of the intervening allylcopper(II), and a radical TEMPO trap.
- Itoh, Taisuke,Shimizu, Yohei,Kanai, Motomu
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supporting information
p. 2736 - 2739
(2014/06/09)
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- Practical methods for the synthesis of trifluoromethylated alkynes: Oxidative trifluoromethylation of copper acetylides and alkynes
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Two practical and complementary methods are reported for the synthesis of trifluoromethylated alkynes. The first one, a mix-and-stir process, is based on the oxidative trifluoromethylation of readily available and bench-stable copper acetylides while the second one, which displays a broad substrate scope and has several advantages over existing procedures, is based on the oxidative copper-catalyzed direct trifluoromethylation of terminal alkynes. Both reactions provide user-friendly processes for the synthesis of trifluoromethylated acetylenes which can be easily obtained from readily available starting materials.
- Tresse, Cedric,Guissart, Celine,Schweizer, Stephane,Bouhoute, Yassine,Chany, Anne-Caroline,Goddard, Mary-Lorene,Blanchard, Nicolas,Evano, Gwilherm
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supporting information
p. 2051 - 2060
(2014/07/07)
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- Mechanism of alcohol oxidation mediated by copper(II) and nitroxyl radicals
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2,2′-Bipyridine-ligated copper complexes, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are highly effective catalysts for aerobic alcohol oxidation. Considerable uncertainty and debate exist over the mechanism of alcohol oxidation mediated by CuII and TEMPO. Here, we report experimental and density functional theory (DFT) computational studies that distinguish among numerous previously proposed mechanistic pathways. Oxidation of various classes of radical-probe substrates shows that long-lived radicals are not formed in the reaction. DFT computational studies support this conclusion. A bimolecular pathway involving hydrogen-atom-transfer from a CuII-alkoxide to a nitroxyl radical is higher in energy than hydrogen transfer from a CuII-alkoxide to a coordinated nitroxyl species. The data presented here reconcile a collection of diverse and seemingly contradictory experimental and computational data reported previously in the literature. The resulting Oppenauer-like reaction pathway further explains experimental trends in the relative reactivity of different classes of alcohols (benzylic versus aliphatic and primary versus secondary), as well as the different reactivity observed between TEMPO and bicyclic nitroxyls, such as ABNO (ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl).
- Ryland, Bradford L.,McCann, Scott D.,Brunold, Thomas C.,Stahl, Shannon S.
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supporting information
p. 12166 - 12173
(2014/12/09)
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- Dehydrogenative α-oxygenation of ethers with an iron catalyst
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Selective α-oxidation of ethers under aerobic conditions is a long-pursued transformation; however, a green and efficient catalytic version of this reaction remains challenging. Herein, we report a new family of iron catalysts capable of promoting chemoselective α-oxidation of a range of ethers with excellent mass balance and high turnover numbers under 1 atm of O2 with no need for any additives. Unlike metalloenzymes and related biomimetics, the catalyst produces H2 as the only byproduct. Mechanistic investigations provide evidence for an unexpected two-step reaction pathway, which involves dehydrogenative incorporation of O2 into the ether to give a peroxobisether intermediate followed by cleavage of the peroxy bond to form two ester molecules, releasing stoichiometric H2 gas in each step. The operational simplicity and environmental friendliness of this methodology affords a useful alternative for performing oxidation, while the unique ability of the catalyst in oxygenating a substrate via dehydrogenation points to a new direction for understanding metalloenzymes and designing new biomimetic catalysts.
- Gonzalez-De-Castro, Angela,Robertson, Craig M.,Xiao, Jianliang
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supporting information
p. 8350 - 8360
(2014/06/24)
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- Aryl-substituted cyclopropyl acetylenes as sensitive mechanistic probes in the gold-catalyzed hydration of alkynes. comparison to the Ag(I)-, Hg(II)-, and Fe(III)-catalyzed processes
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The gold-catalyzed hydration of 2-phenyl- or 2,2-diphenylcyclopropyl acetylene, sensitive probes to trace the formation of vinyl carbocations, provides exclusively the corresponding cyclopropyl methyl ketones. On the other hand, in the Ag(I)- or Fe(III)-c
- Velegraki, Georgia,Stratakis, Manolis
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supporting information
p. 8880 - 8884
(2013/09/24)
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- General and efficient α-oxygenation of carbonyl compounds by TEMPO induced by single-electron-transfer oxidation of their enolates
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A generally applicable method for the synthesis of protected α-oxygenated carbonyl compounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N-O bond cleavage to α-hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2-diols or O-protected amino alcohols. The oxygenation of enolates proves to be the most general and effective methodology for the synthesis of O-protected α-oxy carbonyl compounds and nitriles A. The scope and limitations of the electron-transfer-induced radical coupling reaction with TEMPO are presented. The reaction pathways are outlined. Methods for the deprotection to α-hydroxy carbonyl compounds B are provided and discussed. Copyright
- Dinca, Emanuela,Hartmann, Philip,Smrcek, Jakub,Dix, Ina,Jones, Peter G.,Jahn, Ullrich
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supporting information
p. 4461 - 4482
(2012/10/30)
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- Synthesis of highly functionalized cyclohexenone rings: Rhodium-catalyzed 1,3-acyloxy migration and subsequent [5+1] cycloaddition
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Lead Rh-ole: Highly substituted cyclohexenones were prepared from cyclopropyl-substituted propargyl esters by using a [{Rh(CO)2Cl} 2] catalyst. This metal catalyst promoted the 1,3-acyloxy migration of propargyl esters and a subsequent [5+1] cycloaddition of the resulting allenylcyclopropanes in the presence of CO with high regioselectivity.
- Shu, Dongxu,Li, Xiaoxun,Zhang, Min,Robichaux, Patrick J.,Tang, Weiping
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supporting information; scheme or table
p. 1346 - 1349
(2011/04/22)
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- Photocycloaddition of biscyclopropyl alkenes to C60: An unprecedented approach toward cis-1 tricyclic-fused fullerenes
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A novel, simple, and entirely regioselective tandem cycloaddition of biscyclopropyl-substituted alkenes to [60]fullerene has been revealed. This reaction affords cis-1 tricyclic-fused organofullerenes bearing the hitherto elusive 5-4-5 fused tricyclic ring system.
- Tzirakis, Manolis D.,Alberti, Mariza N.,Orfanopoulos, Michael
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supporting information; experimental part
p. 3364 - 3367
(2011/09/12)
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- Copper-catalyzed direct alkenylation of N-iminopyridinium ylides
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(Figure Presented) A versatile Cu-catalyzed direct C-H alkenylation of N-iminopyridinium ylides, compatible with several different copper sources (including a penny), provides a powerful and inexpensive method for the synthesis of functionalized pyridine derivatives. Chemoselective functionalization of halide-containing compounds allows the synthesis of alkenyl pyridines containing reactive tethers for further functionalization
- Mousseau, James J.,Bull, James A.,Charette, Andre B.
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supporting information; experimental part
p. 1115 - 1118
(2010/05/17)
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- Gold(l)-catalyzed ring expansions of unactivated alkynylcyclopropanes to (E)-2-alkylidenecyclobutanamines in the presence of sulfonamides
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(Chemical Equation Presented) The ring expansion of cyclopropane derivatives provides a powerful method to construct synthetically useful four-membered carbocycles. Herein, a new type of gold(l)-catalyzed ring expansion of an unactivated alkynylcyclopropane/sulfonamide trapping strategy to (E)-2-alkylidenecyclobutanamines was described. The reaction tolerates a range of aryl and alkyl substituents with moderate to good yields.
- Ye, Siyu,Yu, Zhi-Xiang
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supporting information; experimental part
p. 804 - 807
(2010/04/06)
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- SmI2-mediated reductive cross-coupling reactions of -cyclopropyl nitrones
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Three new α-cyclopropyl nitrones have been synthesized as mechanistic probes for reductive cross-coupling reactions of nitrones. The α-cyclopropylcarbinyl radical intermediate formed by single electron transfer from SmI2 to these nitrones is no
- Burchak, Olga N.,Masson, Geraldine,Py, Sandrine
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scheme or table
p. 1623 - 1626
(2010/09/05)
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- In situ generation of zinc carbenoids from diazo compounds and zinc salts: Asymmetric synthesis of 1,2,3-substituted cyclopropanes
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(Chemical Equation Presented) The first enantioselective cyclopropanation of alkenes using zinc carbenoids generated in situ from diazo compounds and zinc salts is reported. This new method allows the highly enantioand diastereoselective synthesis of 1,2,
- Goudreau, Sebastien R.,Charette, Andre B.
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supporting information; experimental part
p. 15633 - 15635
(2010/01/29)
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- Mechanistic studies on au(I)-catalyzed [3,3]-sigmatropic rearrangements using cyclopropane probes
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A comparative study of the Au(I)-catalyzed [3,3]-sigmatropic rearrangement of propargylic esters and propargyl vinyl ethers is described. Stereochemically defined cyclopropanes are employed as mechanistic probes to provide new synthetic and theoretical data concerning the reversibility of this type of rearrangement. Factors controlling the structure-reactivity relationship of Au(I)-coordinated allenes have been examined, therebyallowing for controlled access to orthogonal reactivity.
- Mauleon, Pablo,Krinsky, Jamin L.,Toste, F. Dean
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supporting information; experimental part
p. 4513 - 4520
(2009/09/30)
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- Cyclopropanation with dibromomethane under grignard and barbier conditions
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Tertiary Grignard reagents and dibromomethane efficiently cyclopropanate allylic (and certain homoallylic) magnesium and lithium alcoholates at ambient temperature in ether solvents. Lithium (homo)allyl alcoholates are directly cyclopropanated with magnes
- Brunner, Gerhard,Eberhard, Laura,Oetiker, Juerg,Schroeder, Fridtjof
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scheme or table
p. 3708 - 3718
(2010/04/02)
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- Acyl radical reactions in fullerene chemistry: Direct acylation of [60]fullerene through an efficient decatungstate-photomediated approach
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A versatile and highly efficient photochemical methodology for the direct acylation of C60 has been developed. This approach utilizesa wide variety of acyl radicals derived from aldehydes through a hydrog en atom abstraction process mediated by
- Tzirakis, Manolis D.,Orfanopoulos, Michael
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supporting information; body text
p. 4063 - 4069
(2009/09/05)
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- Tandem cyclopropanation with dibromomethane under Grignard conditions
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(Chemical Equation Presented) Tertiary Grignard reagents and dibromomethane efficiently cyclopropanate allylic (and certain homoallylic) magnesium and lithium alcoholates at ambient temperature in ether solvents. Lithium (homo)allyl alcoholates are directly cyclopropanated with magnesium and CH 2Br2 under Barbier conditions at higher temperatures. The reaction rates depend on the substitution pattern of the (homo)allylic alcoholates and on the counterion with lithium giving best results. Good to excellent syn-selectivities are obtained from α-substituted substrates, which are in accord with a staggered Houk model. In tandem reactions, cyclopropyl carbinols are obtained from allyloxylithium or -magnesium intermediates, generated in situ by alkylation of conjugated aldehydes, ketones, and esters as well as from allyl carboxylates or vinyloxiranes. Using this methodology, numerous fragrance ingredients and their precursors were efficiently converted to the corresponding cyclopropyl carbinols.
- Brunner, Gerhard,Eberhard, Laura,Oetiker, Juerg,Schroeder, Fridtjof
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p. 7543 - 7554
(2008/12/22)
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- SUBSTITUTED HETEROCYCLIC DERIVATIVES AND THEIR PHARMACEUTICAL USE AND COMPOSITIONS
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Compounds of the general Formula I, wherein X1, X2, X3, X4, X5, X6, X7, R1, R2, R4, R5, R6, R7, R8, R9, R10, Y1, n, m, p and q are defined as above, their preparation and their use as antimicrobial agents.
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(2008/12/08)
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- Thermal C2-C6 cyclization of enyne-allenes. Experimental evidence for a stepwise mechanism and for an unusual thermal silyl shift
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Enyne-allenes 4a-c bearing various cyclopropyl systems as radical clock reporter groups at the allene terminus have been synthesized and subjected to thermal C2-C6 cyclization. The ratio of ene versus formal Diels-Alder products could be rationalized on the basis of steric effects. Only the thermolysis of 4c, equipped with the fast diphenylcyclopropylcarbinyl radical clock, afforded a 1,3-butadienyl benzofulvene clearly formed via cyclopropyl ring opening. This finding provides unambiguous evidence for a stepwise mechanism of the C2-C6 cyclization making it possible to suggest a lifetime for the intermediate diradical of > 1 × 10-10 s (at 170 °C). An interesting corollary was the isolation of an unexpected silyl shift product in the thermolysis of all three enyne-allenes that allows explanation of the loss of the TIPS group in some of the Diels-Alder products. For a full understanding of the mechanism, silyl and hydrogen shift processes were interrogated using DFT.
- Schmittel, Michael,Mahajan, Atul A.,Bucher, Goetz,Bats, Jan W.
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p. 2166 - 2173
(2007/10/03)
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- Generation of oxynitrenes and confirmation of their triplet ground states
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New sulfoximine- and phenanthrene-based photochemical precursors to oxynitrenes have been developed. These precursors have been used to examine the chemistry and spectroscopy of oxynitrenes. The first EPR spectra of oxynitrenes are reported and are consistent with their triplet ground states. Additional support for the triplet ground state of oxynitrenes is provided by trapping and reactivity studies, nanosecond time-resolved IR investigations, and computational studies.
- Wasylenko, Walter A.,Kebede, Naod,Showalter, Brett M.,Matsunaga, Nikita,Miceli, Alexander P.,Liu, Yonglin,Ryzhkov, Lev R.,Hadad, Christopher M.,Toscano, John P.
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p. 13142 - 13150
(2008/03/11)
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- Superbase-promoted rearrangement of oxiranes to cyclopropanes
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Aryl- and alkenyl substituted oxiranes, when submitted to treatment with superbasic reagents, undergo a highly regio- and stereoselective rearrangement leading to cyclopropylmethanol derivatives. The process can also be applied to mono- and dihydroxy subs
- Mordini, Alessandro,Peruzzi, Daniela,Russo, Francesco,Valacchi, Michela,Reginato, Gianna,Brandi, Alberto
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p. 3349 - 3360
(2007/10/03)
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- Products from solvolysis reactions that form (2-phenylcyclopropyl)carbinyl cations
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Products from solvolytic reactions that form the (2-phenylcyclopropyl) carbinyl cation were determined. The majority of products (> 98%) derived from the 1-phenyl-3-butenyl cation, consistent with reports by Wiberg and co-workers. Small amounts of products derived from the 1-phenyl-1- cyclopropylmethyl cation also were found; these products were previously predicted to be formed from reactions of the title cation. Although the 1-phenyl-1-cyclopropylmethyl cation is considerably more stable than the 1-phenyl-3-butenyl cation, it is not kinetically accessible under a variety of solvolytic conditions. Copyright
- Chandrasena, R. Esala P.,Aebisher, David,Newcomb, Martin
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p. 974 - 977
(2007/10/03)
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- Vanadium-catalyzed asymmetric oxidation of α-hydroxy esters using molecular oxygen as stoichiometric oxidant
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A vanadium-catalyzed method for the oxidative kinetic resolution of α-hydroxyesters, using oxygen as the terminal oxidant, is described. The catalyst is generated in situ from vanadium(V) tri-iso-propoxyoxide in combination with a tridentate ligand derived from 3,5-di-tert-butylsalicylaldehyde and (S)-tert-leucinol. The reaction allows for the enantioselective synthesis of both aromatic and aliphatic secondary alcohols, including those containing olefins and alkynes. Copyright
- Radosevich, Alexander T.,Musich, Christine,Toste, F. Dean
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p. 1090 - 1091
(2007/10/03)
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- A Novel Class of Tunable Zinc Reagents (RXZnCH2Y) for Efficient Cyclopropanation of Olefins
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A class of zinc reagents (RXZnCH2Y) generated with an appropriate organozinc is very effective for the cyclopropanation of olefins. The reactivity and selectivity of these reagents can be regulated by tuning the electronic and steric nature of the RX group on Zn. A reasonable level of enantioselectivity was obtained for the cyclopropanation of unfunctionalized olefins when a chiral (iodomethyl)zinc species was used, providing a valuable approach for the asymmetric cyclopropanation of unfunctionalized olefins.
- Lorenz, Jon C.,Long, Jiang,Yang, Zhiqiang,Xue, Song,Xie, Yinong,Shi, Yian
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p. 327 - 334
(2007/10/03)
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- Construction of a cis-Cyclopropane via Reductive Radical Decarboxylation. Enantioselective Synthesis of cis- and trans-1-Arylpiperazyl-2-phenylcyclopropanes Designed as Antidopaminergic Agents
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(1S,2S)-, (1S,2R)-, and (1R,2S)-1-(2,4-Dimethylphenyl)piperazyl-2-phenylcyclopropane (2a, 3, and ent-3, respectively), which were designed as conformationally restricted analogues of haloperidol (1), a clinically effective antipsychotic agent, were synthe
- Yamaguchi, Kazuya,Kazuta, Yuji,Abe, Hiroshi,Matsuda, Akira,Shuto, Satoshi
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p. 9255 - 9262
(2007/10/03)
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- Kinetic Enzymatic Resolution of Cyclopropane Derivatives
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The kinetic enzymatic resolution of various cyclopropane derivatives was systematically investigated. The study focused on synthetically useful cyclopropylmethanols (e.g., 18a/j or 19a/j) as well as some rarely investigated cyclopropanols (e.g., 24/25 or 27). The combination of enantioselective catalytic or diastereoselective synthesis of enantiomerically enriched compounds with enzymatic approaches ultimately led to the most convenient route to enantiomerically pure starting materials. Again, this was especially proven for the synthesis of cyclopropanols 18a/j and 19a/j. Key to the successful investigation was to rigorously establish an analytical tool for the analysis of enantiomeric composition of reaction mixtures.
- Pietruszka, Joerg,Rieche, Anja C. M.,Wilhelm, Thorsten,Witt, Andreas
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p. 1273 - 1286
(2007/10/03)
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- Mechanistic Studies of the Addition of Carbonyl Compounds to Tetramesityldigermene
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The mechanism of the addition of carbonyl compounds to digermenes was investigated by examining the reaction between tetramesityldigermene and two mechanistic probes: trans-2-phenylcyclopropane carbaldehyde and trans,trans-2-methoxy-3-phenylcyclopropane c
- Samuel, Mini S.,Baines, Kim M.
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p. 12702 - 12703
(2007/10/03)
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- Stability, reactivity, solution, and solid-state structure of halomethylzinc alkoxides
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In this paper, we report our findings regarding the development of a Lewis acid-catalyzed cyclopropanation of allylic alcohols with bis(iodomethyl)zinc. Iodomethylzinc alkoxides can be formed by treatment of an alcohol with bis(iodomethyl)zinc. These species are not prone to undergo cyclopropanation at low temperature but the addition of a Lewis acid in catalytic amounts induces the cyclopropanation reaction. Using this procedure, we demonstrated that the Lewis acid-catalyzed pathway significantly overwhelms the uncatalyzed one. This paper describes fundamental issues regarding the preparation and stability of halomethyl zinc alkoxides in solution as well as their aggregation state in solution and solid-state structures. Furthermore, the competition reaction between the inter- vs intramolecular cyclopropanation will be studied. Finally, we will discuss the possible activation pathways to explain the Lewis acid activation of halomethylzinc alkoxides. These findings provided new insights on the reactivity of ROZnCH2I and established the groundwork for the elaboration of an enantioselective version of the reaction.
- Charette,Molinaro,Brochu
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p. 12160 - 12167
(2007/10/03)
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- Probing the radical mechanism of galactose oxidase using an ultrafast radical probe
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Processing of trans-2-phenylcyclopropylmethanols 5 and 6 by the monocopper/tyrosine radical enzyme galactose oxidase led to mechanism-based inactivation with a partition ratio, (k(cat) + k(inact))/k(inact), of approximately 1 and a primary deuterium isoto
- Turner, B. Elizabeth,Branchaud, Bruce P.
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p. 3341 - 3346
(2007/10/03)
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- Synthesis and HPLC-analysis of N-(2-phenyl-cyclopropyl)-substituted chain elongated nucleoside analogues
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A novel class of nucleoside analogues containing adenine, uracil, thymine and 5-fluorouracil as the heterocyclic moieties have been prepared from 2-phenylcyclopropane carboxylic acid. These compounds showed weak antitumor activity. The resolution of the r
- Csuk, Rene,Kern, Anja,Mohr, Kristina
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p. 1463 - 1468
(2007/10/03)
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- Exploring new reactive species for cyclopropanation
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An organozinc species RXZnCH2I generated by reacting Zn(CH2I)2 with RXH was found to be an efficient reagent for the cyclopropanation of olefins at room temperature. A 50.7% ee was obtained for the cyclopropanation of trans-β-methylstyrene when a chiral alcohol was used.
- Yang, Zhiqiang,Lorenz, Jon C.,Shi, Yian
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p. 8621 - 8624
(2007/10/03)
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