- Reactions of 2-Iodo- and 1,2-Dihaloadamantanes with Carbanions in DMSO by the SRN1 Mechanism
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The reaction of 2-iodoadamantane (1) with the potassium enolate of acetophenone (2) did not occur in the dark but succeeded under irradiation or in the presence of FeBr2 to give the substitution product 3 in 62% and 88% yields, respectively. The photostimulated reaction was inhibited by p-dinitrobenzene (p-DNB). There was no reaction of 1 with the anion of nitromethane (4) in the dark or under irradiation. However, 4 reacted with 1 in the presence of acetone enolate ion (entrainment reaction) to yield 88% of the substitution product 2-adamantylnitromethane (5). The photostimulated reaction of 1 with anthrone (6), 2-naphthyl methyl ketone (9), and N-acetylthiomorpholine (11) anions afforded the substitution compounds 7 (37%), 10 (32%), and 12 (20%), respectively. There was no reaction of 1-chloro-2-iodoadamantane (13) with 2 in the dark (2 h), but under irradiation (5 min) it yielded 52% of the monosubstitution product α-(1-chloro-2-adamantyl)-acetophenone (14). Under longer irradiation time (3 h), the same yield of 14 (52%) was obtained but the disubstitution product 15 was formed in 45% yield. Product 15 was also formed in the photostimulated reaction of 14 with 2. 2-Chloro-1-iodoadamantane (18) did not react with 2 in the dark (2 h), but the photostimulated reaction yielded the monosubstitution product α-(2-chloro-1-adamantyl)acetophenone (19) in 53% and 15 in 4% yield. Products 14 and 19 are intermediates in the formation of 15 in these reactions. There was a slow dark reaction of 1,2-diiodoadamantane (20) with 4 in the presence of acetone enolate ion to afford the iodomonosubstitution compound 21 (40%) and the disubstitution product 22 (13%). The photostimulated reaction (25 min) gave 21 (48%) and 22 (41%). On the other hand, after 3 h of irradiation, only traces of 21 could be detected (5%) and the product distribution consisted mainly of 22. The iodomonosubstitution product 21 is an intermediate in these reactions.
- Lukach, Andres E.,Rossi, Roberto A.
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- Tris(dimethylamino)silylium ion: Structure and reactivity of a dimeric silaguanidinium
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Although several strategies for the stabilization of silylium ions have been established, "π-stabilization" with directly attached π-donor heteroatoms at silicon has not been developed yet. Hydride abstraction from (Me2N)3SiH generates dicationic [(Me2N)3Si+]2 in solution and in the solid state-constituting the dimer of an elusive silaguanidinium ion. This compound can be synthesized on a gram scale and is compatible with common organic solvents. However, it readily undergoes spontaneous electrophilic silylation of electron-rich aromatic compounds or initiates a catalytic hydro-defluorination reaction.
- Kramer, Nina,Wadepohl, Hubert,Greb, Lutz
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- RITTER REACTIONS. II. REDUCTIVE DEAMIDATION OF N-BRIDGEHEAD AMIDES
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Adamantyl- or homoadamantyl-derived N-bridgehead amides are converted in high yields into hydrocarbon derivatives on prolonged reflux in ethanol and 50percent sulphuric acid (1:1 by volume).This process probably involves AAL1 hydrolysis to the tertiary carbonium ion, followed by hydride abstraction from the ethanol solvent.
- Bishop, Roger,Burgess, Graham
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- Synthesis of several halobisnoradamantane derivatives and their reactivity through the SRN1 mechanism
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Several bridgehead halobisnoradamantane derivatives (5, 7, 10, and 17) were synthesized from tricyclic diester 1 in good yields using standard methods. The reactivity through the SRN1 mechanism of the above compounds and the known halobisethano derivatives 24 and 25a-c was studied. Iodo derivatives 7, 10, and 25a reacted with diphenylphosphide ions in DMSO under irradiation to give the corresponding substitution and reduction products by the SRN1 mechanism, while iodo ketone 17 gave a mixture of the rearranged substitution product 36 and the reduction product 18. Formation of 36 takes place through a 1,5-hydrogen migration of the initially formed radical, a kind of process that has been observed for the first time in the SRN1 propagation steps. The diiodo derivative 24 reacted with diphenylphosphide ions under similar reaction conditions to give the substitution and/or reduction products 32, 31, 27, 25a, and 26. The intramolecular ET reaction in the monosubstitution radical anion 32?- seems to be faster than the intermolecular ET to the substrate, and the monoiodo derivative 25a is a reaction intermediate.
- Camps,Lukach,Rossi
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- Development of a new ultraporous polymer as support in organic synthesis.
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This paper describes the preparation and post-functionalisation of a new polymeric support based on emulsion-derived foams and called polyHIPEs. The remaining pendant vinylic bonds are easily functionalised by a free radical mechanism. The large pores and channels of this material allow an easy access of the reagent in solution toward the grafted species. PolyHIPE-supported thiol, in the presence of an excess of triethylsilane, showed a good activity and selectivity toward reductive cyclisation of 6-bromohex-1-ene and 1-allyloxy-2-bromobenzene.
- Deleuze, Herve,Maillard, Bernard,Mondain-Monval, Olivier
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- Rate study of haloadamantane reduction by samarium diiodide
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Rate constants directly measured by GC/MS-analyzed method for reduction of haloadamantanes by SmI2 in presence of HMPA and H2O were obtained. HMPA exhibits stronger catalytic effect than H2O does. The result of faster reaction rate of 1-bromoadamantane than that of 2-bromoadamantane can be used to confirm the formation of alkyl radical as the rate limiting step of this reduction.
- Lin, Tzuen-Yeuan,Fuh, Ming-Ren,Chen, Yu-Yu
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- Regiochemistry of the photostimulated reaction of the phthalimide anion with 1-iodoadamantane and tert-butylmercury chloride by the SRN1 mechanism
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The photostimulated reaction of the phthalimide anion (1) with 1-iodoadamantane (2) gave 3-(1-adamantyl) phthalimide (3) (12%) and 4-(1-adamantyl) phthalimide (4) (45%), together with the reduction product adamantane (AdH) (21%). The lack of reaction in the dark and inhibition of the photoinduced reaction by p-dinitrobenzene, 1,4-cyclohexadiene, and di-tert-butylnitroxide indicated that 1 reacts with 2 by an SRN1 mechanism. Formation of products 3 and 4 occurs with distonic radical anions as intermediates. The photoinduced reaction of anion 1 with tert-butylmercury chloride (10) affords 4-tert-butylphthalimide (11) as a unique product. By competition experiments toward 1, 1-iodoadamantane was found to be ca. 10 times more reactive than tert-butylmercury chloride.
- Maquieira, Manuel Bajo,Penenory, Alicia B.,Rossi, Roberto A.
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- NATURE OF THE SPECIES RESPONSIBLE FOR THE HIGH ACTIVITY OF RCOX*2AlX3 COMPLEXES IN REACTIONS WITH ALKANES AND CYCLOALKANES
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The reasons for the high reactivity of aprotic organic superacids (AOS) containing an acyl halide and a double molar excess of Lewis acid in reactions with saturated hydrocarbons are studied.The synthesis and spectral properties of two pairs of acyl salts are studied: MstCO+AlBr4- and MstCO+Al2Br7- (Mst = 2,4,6-Me3C6H2) and Ac+SbF6- and Ac+Sb2F11-.Comparison of the reactivities of these salts in cracking of alkanes and isomerization of trimethylenenorbornane demonstrated that the AOS activity is due to generation of acyl salts with a dimeric anion in the slightly polar solutions.Analysis of the 13C NMR spectra suggests that the superacid properties of these salts are due to formation of species containing acyl cations coordinated to the Lewis acid.
- Akhrem, I. S.,Orlinkov, A. V.,Bakhmutov, V. I.,Afanas'eva, L. V.,Vol'pin, M. E.
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- Hypophosphorous acid and its salts: New reagents for radical chain deoxygenation, dehalogenation and deamination
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Thionocarbonates and xanthates of alcohols, bromides, iodides and isonitriles can be transformed to the corresponding hydrocarbons with hypophosphorous acid or its salts in radical chain reactions.
- Barton,Jang,Jaszberenyi
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- Carbene rearrangements, 60. Supramolecular structure-reactivity relationships: Photolysis of a series of aziadamantane@cyclodextrin inclusion complexes in the solid state
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Photolyses of the α-, β- and γ-cyclodextrin complexes of 2-aziadamantane (1) in the solid state afforded markedly different product distributions, as determined by quantitative GC and HPLC analyses. The results are discussed with respect to the structures of the inclusion complexes.
- Krois, Daniel,Brecker, Lothar,Werner, Andreas,Brinker, Udo H.
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- Synthesen von Tricyclo4,8>decan (2-Homobrendan)
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Three different approaches to tricyclo4,8>decane (5) (and derivatives thereof), one of the 19 isomeric hydrocarbons of the 'adamantaneland', are described: 1) Cyclization of properly functionalized bicyclooctanes as 32 (cyclialkylation), 40 + 42 (thermocyclization) and 44 + 45 (photocyclization); 2) Silver(I)-ion catalyzed rearrangement of 5,7- and 5,10-Dehydroprotoadamantane (63 and 64, respectively) yielding tricyclo4,8>dec-2- (39) and -5-ene (59), respectively; 3) Thermal eliminative rearrangement of the 10endo-p-toluenesulfonate and -methanesulfonate of protoadamantane (71 and 72) and protoadamant-4-ene (76 and 77), respectively, yielding tricyclo4,8>dec-2-ene (39) and -2,5-diene (15), respectively.
- Jaeggi, Franz Josef von,Buchs, Peter,Ganter, Camille
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- Synthesis and asymmetric hydrogermylation reactions of dithiogermanium hydrides derived from C2-symmetric dithiols
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Two members of a new class of dithiogermanium hydrides have been prepared in racemic and enantiopure form. Reaction of 2,2′-dithiobinap and 3,3′-bis-trimethylsilyl-2,2′-dithiobinap with tBuGeCl3 followed by reduction provides the corresponding germanium hydrides. Hydrogermylation of methyl methacrylate occurs with low selectivity (10/1) for the latter.
- Curran,Gualtieri
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- ADAMANTANE REARRANGEMENT MECHANISM. 1,2-TRIMETHYLENENORBORNANES
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Unexpected differences in the aluminium bromide-catalyzed rearrangement behavior of 1,2-endo-trimethylenenorbornane (1) and its 1,2-exo-isomer (2) are interpreted.Isotopic labelling studies indicate that reversible abstraction of the tertiary 2-endo hydride in 2 does not occur (Scheme 1).Instead, rearrangement to 6 is favored.The label scrambling in the final product, adamantane (8), is attributed to degenerate isomerization in the protoadamantyl precursor, 7.
- Farcasiu, Malvina,Hagaman, Edward W.,Wenkert, Ernest,Schleyer, Paul von Rague
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- A different behaviour of the phthalimide ion in Srn1 reactions
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The phthalimide anion reacts by the SRN1 mechanism under photostimulation)with different substrates. Whilst with 1-iodonaphthalene only reduction of the naphthyl radical is observed, with 1-iodoadamantane coupling at the carbon instead of at the nitrogen takes place.
- Maquieira, Manuel Bajo,Penenory, Alicia B.,Rossi, Roberto A.
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- Preparation and reactivity of a non-styrenic polymer-supported organotin chloride catalyst
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A new type of macroporous polymer-supported organotin hydride has been prepared by suspension copolymerisation of an allyl ether monomer bearing an organotin moiety with N-phenylmaleimide and 1,1′-(methylenedi-4,1-phenylene)bismaleimide. Several resins were synthesised using different ratios of toluene-N-methylformanilide as the porogen. The swelling characteristics of the resins in different solvents and their specific surface areas were estimated. The organotin chloride-functionalised beads obtained showed good activity and good stability to reduction of bromoadamantane by sodium borohydride. Tin leaching during successive reuses was estimated.
- Chemin, Alexandre,Deleuze, Herve,Maillard, Bernard
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- THE THERMOLYSIS OF 1,1'-BIDIAMANTANE
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The activation parameters for the homolytic cleavage of the central CC-bond in 1.1'-bidiamantane 5 and their comparison with corresponding data for 2.2.3.3-tetramethylbutane 6 together with the strain enthalpies of 5 and 6 are conclusive experimental evidence for the absence of appreciable strain in 1-adamantyl radicals 3.This supports predictions made on the basis of calculations using a recently developed force field for radicals.
- Beckhaus, Hans-Dieter,Flamm, Manuela A.,Ruechardt, Christoph
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- The mechanism for the rearrangement of the adamantyl cation
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The mechanism for the rapid rearrangement of the adamantyl cation (1-yl → 2-yl, or vice versa) in sulfuric acid utilises catalytic adamantane in an intermolecular hydride transfer reaction; a slower rearrangement mechanism involves reversible ring-opening of the adamantyl skeleton, and allows incorporation of high levels of deuterium.
- Adams, David R.,Bailey, Patrick D.,Collier, Ian D.,Leah, Stephen A. H.,Ridyard, Colin
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- CATALYTIC REARRANGEMENT OF TETRAHYDRODICYCLOPENTADIENE TO ADAMANTANE OVER Y-ZEOLITE
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Bifunctional rare-earth exchanged Y zeolite, has the high catalytic activity for the synthesis of adamantane from tetrahydrodicyclopentadiene in the presence of hydrogen and hydrogen chloride, in a fixed bed flow system.The catalyst deactivated by pore plugging with deposited hydrocarbons can be almost completely regenerated by hydrocracking.
- Honna, Kosaku,Sugimoto, Michio,Shimizu, Nobuaki,Karisaki, Konomu
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- Reactions of 1,3-Dihaloadamantanes with Carbanions in DMSO: Ring-Opening Reactions to Bicyclo[3.3.1]nonane Derivatives by the SRN1 Mechanism
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The reactions of 1,3-dihaloadamantanes with various carbanionic nucleophiles were studied. Potassium enolates of acetophenone (2) and pinacolone (10b) and the anion of nitromethane (10a) reacted with 1,3-diiodoadamantane (1a) in DMSO under photostimulation by a free radical chain process to form a 1-iodo monosubstitution product as an intermediate, which undergoes concerted fragmentation to form derivatives of 7-methylidenebicyclo[3.3.1]nonene (3 and 11). This reaction does not occur in the dark at 25 °C, and the photostimulated reaction is partially inhibited by p-dinitrobenzene. 1,3-Dibromoadamantane (1b) and 1-bromo-3-chloroadamantane (1c) also reacted under irradiation with 2, although more sluggish than 1a, also giving the 7-methylidenebicyclo-[3.3.1]nonene derivative 3. When a nucleophile was used without acidic hydrogens in the α-position, such as the enolate ion of isobutyrophenone (16), in order to inhibit the ring opening of adamantane, it reacted under irradiation with 1a to give the products adamantane, 1-iodoadamantane, monosubstituted 17, 1-iodo-monosubstituted 19, and disubstituted 20. Their distribution depended on the experimental conditions. In these reactions, 1-iodoadamantane and 19 were intermediates. For reactions involving the radical anion intermediate of the 1-iodo monosubstitution product, the intermolecular ET to the substrate was observed to be much faster than intramolecular ET to the C-I bond.
- Lukach, Andres E.,Santiago, Ana N.,Rossi, Roberto A.
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- A FACILE SYNTHESIS OF 3,4-HOMOADAMANTANEDIOL VIA THE REACTION OF 1-ADAMANTYL TRIFLATE WITH CARBON MONOXIDE
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The reaction of 1-adamantyl triflate (1) with carbon monoxide and adamantane catalyzed by triflic acid affords 3-hydroxy-4-homoadamantyl 1-adamantanecarboxylate (2) as a major product, which is easily converted to 3,4-homoadamantanediol (5) - a promising starting material for 3,4-bifunctional homoadamantane derivatives.
- Takeuchi, Ken'ichi,Miyazaki, Tadakazu,Kitagawa, Itsuko,Okamoto, Kunio
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- In situ generated, polymer-supported organotin hydrides as clean reducing agents
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Polymer-supported organotin hydrides were generated in-situ from polymer-supported organotin halides and NaBH4. Their reducing ability was monitored by reaction with 1-bromoadamantane. The residual tin pollution was estimated by ICP-MS.
- Dumartin, Gilles,Pourcel, Magali,Delmond, Bernard,Donard, Olivier,Pereyre, Michel
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- Direct Hydrodecarboxylation of Aliphatic Carboxylic Acids: Metal- and Light-Free
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A mild and inexpensive method for direct hydrodecarboxylation of aliphatic carboxylic acids has been developed. The reaction does not require metals, light, or catalysts, rendering the protocol operationally simple, easy to scale, and more sustainable. Crucially, no additional H atom source is required in most cases, while a broad substrate scope and functional group tolerance are observed.
- Burns, David J.,Lee, Ai-Lan,McLean, Euan B.,Mooney, David T.
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supporting information
p. 686 - 691
(2022/01/28)
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- Synthesis of adamantane by ionic liquid-promoted isomerization of tricyclo[5.2.1.02,6]decane and H2SO4-mediated hydroisomerization of pentacyclo[4.4.0.02,4.03,7.08,10]decane
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Adamantane was synthesized by skeletal isomerization of endo- and exo-tricyclo[5.2.1.02,6]-decanes in the presence of ionic liquid [Et3NH]+[Al2Cl7]?—CuSO4. A new method to synthesize adamantane in 75% yield by H2SO4-mediated hydroisomerization of its new precursor, pentacyclo[4.4.0.02,4.03,7.08,10]decane, was developed.
- Aminov,Ramazanov,Khusnutdinov
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p. 102 - 106
(2022/02/17)
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- A Mild, General, Metal-Free Method for Desulfurization of Thiols and Disulfides Induced by Visible-Light
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A visible-light-induced metal-free desulfurization method for thiols and disulfides has been explored. This radical desulfurization features mild conditions, robustness, and excellent functionality compatibility. It was successfully applied not only to the desulfurization of small molecules, but also to peptides.
- Qiu, Wenting,Shi, Shuai,Li, Ruining,Lin, Xianfeng,Rao, Liangming,Sun, Zhankui
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supporting information
p. 1255 - 1258
(2021/05/05)
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- Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
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Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
- Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
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p. 4069 - 4078
(2021/04/06)
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- Exhaustive One-Step Bridgehead Methylation of Adamantane Derivatives with Tetramethylsilane
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A methylation protocol of adamantane derivatives was investigated and optimized using AlCl3 and tetramethylsilane as the methylation agent. Substrates underwent exhaustive methylation of all available bridgehead positions with yields ranging from 62 to 86 %, and up to six methyl groups introduced in one step. Scaling-up of the reaction was demonstrated by performing the >40 gram-scale synthesis of 1,3,5,7-tetramethyladamantane with 62 % yield. For several substrates, rearrangements were observed, as well as cleavage of functional groups or Csp3?Csp2 bonds or even cyclohexyl-adamantyl bonds. Based on mechanistic studies, it is suggested that a reactive methylation complex is formed from tetramethylsilane and AlCl3. X-ray diffraction structures of hexamethylated bis-adamantyls reveal elongation or widening of sp3 carbon bonds between adamantyl moieties to 1.585(3) ? and 125.26(9)° due to repulsive H???H contacts.
- Bonsir, Maxime,Davila, Christian,Geerts, Yves,Kennedy, Alan R.
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supporting information
p. 5227 - 5237
(2021/10/19)
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- A New Protocol for Catalytic Reduction of Alkyl Chlorides Using an Iridium/Bis(benzimidazol-2′-yl)pyridine Catalyst and Triethylsilane
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The reduction of alkyl chlorides using triethylsilane is investigated. Primary, secondary, tertiary, and benzylic C-Cl bonds are effectively converted into C-H bonds using an [IrCl(cod)] 2/2,6-bis(benzimidazol-2′-yl)pyridine catalyst system. This catalyst system is quite simple since the tridentate N-ligand can be easily prepared in one step from commercially available reagents.
- Fukuyama, Takahide,Hamada, Yuki,Ryu, Ilhyong
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p. 3404 - 3408
(2021/07/14)
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- Preparation method of adamantanone
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The invention discloses a preparation method of adamantanone, and relates to the technical field of adamantanone synthesis. The problems that the reaction time is long and the operation process is tedious are solved. The preparation method specifically comprises the following steps: putting raw materials including adamantane, sulfuric acid and trifluoroacetic acid into a batching kettle, and stirring and mixing at 30 DEG C; raising the temperature to 50 DEG C, and introducing nitrogen into the batching kettle; pressing the mixed materials into a reaction tube, and performing standing for 1 minute; pouring the reaction solution on 500g of ice, adding a NaOH aqueous solution which is 7 times the weight of adamantane during cooling, and adjusting the pH value to 9; and extracting by using methylbenzene of which the weight is 3 times that of adamantane. The raw materials are mixed and then heated, nitrogen is introduced, then an oxidation reaction occurs, the retention time and temperatureof reaction liquid in a reaction tube are controlled in the leading-out period, the reaction liquid is extracted through methylbenzene and the NaOH aqueous solution, the extraction liquid is subjected to reduced pressure distillation concentration, cooling, separation and drying treatment, the final product is obtained, the operation process is relatively simple, the reaction is controllable, andthe time is short.
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Paragraph 0033; 0044-0047; 0052; 0063-0066; 0070; 0081-0084;
(2021/04/03)
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- Bipyridinium and Phenanthrolinium Dications for Metal-Free Hydrodefluorination: Distinctive Carbon-Based Reactivity
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The development of novel Lewis acids derived from bipyridinium and phenanthrolinium dications is reported. Calculations of Hydride Ion Affinity (HIA) values indicate high carbon-based Lewis acidity at the ortho and para positions. This arises in part from extensive LUMO delocalization across the aromatic backbones. Species [C10H6R2N2CH2CH2]2+ (R=H [1 a]2+, Me [1 f]2+, tBu [1 g]2+), and [C12H4R4N2CH2CH2]2+ (R=H [2 a]2+, Me [2 b]2+) were prepared and evaluated for use in the initiation of hydrodefluorination (HDF) catalysis. Compound [2 a]2+ proved highly effective towards generating catalytically active silylium cations via Lewis acid-mediated hydride abstraction from silane. This enabled the HDF of a range of aryl- and alkyl- substituted sp3(C?F) bonds under mild conditions. The protocol was also adapted to effect the deuterodefluorination of cis-2,4,6-(CF3)3C6H9. The dications are shown to act as hydride acceptors with the isolation of neutral species C16H14N2 (3 a) and C16H10Me4N2 (3 b) and monocationic species [C14H13N2]+ ([4 a]+) and [C18H21N2]+ ([4 b]+). Experimental and computational data provide further support that the dications are initiators in the generation of silylium cations.
- Burton, Katherine I.,Elser, Iris,Waked, Alexander E.,Wagener, Tobias,Andrews, Ryan J.,Glorius, Frank,Stephan, Douglas W.
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supporting information
p. 11730 - 11737
(2021/07/16)
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- Synthesis and Catalytic Activity of Atrane-type Hard and Soft Lewis Superacids with a Silyl, Germyl, or Stannyl Cationic Center
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The synthesis and isolation of atrane-type molecules 1E+ (E=Si, Ge, or Sn) having a cationic group 14 elemental center are reported. The cations 1E+ act as hard and soft Lewis superacids, which readily interact with various hard and soft Lewis basic substrates. The rigid atrane framework stabilizes the localized positive charge on the elemental center and assists the formation of the well-defined highly coordinated states of 1E+. The cations were applied to the hydrodefluorination, Friedel-Crafts reaction, alkyne cyclization, and carbonyl reduction as Lewis acid catalysts. Most notably, [1Si][ClO4] exhibits unique chemoselectivity that depends on a solvent in the competitive reaction of silyl enol ether with a mixture of benzaldehyde dimethyl acetal and benzaldehyde. Our findings indicate the potential of hard and soft Lewis superacids in organic synthesis.
- Tanaka, Daiki,Konishi, Akihito,Yasuda, Makoto
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supporting information
p. 3118 - 3123
(2021/09/08)
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- Bis(perfluoropinacolato)silane: A Neutral Silane Lewis Superacid Activates Si?F Bonds
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Despite the earth abundance and easy availability of silicon, only few examples of isolable neutral silicon centered Lewis superacids are precedent in the literature. To approach the general drawbacks of limited solubility and unselective deactivation pathways, we introduce a Lewis superacid, based on perfluorinated pinacol substituents. The compound is easily synthesized on a gram-scale as the corresponding acetonitrile mono-adduct 1?(MeCN) and was fully characterized, including single crystal X-ray diffraction analysis (SC-XRD) and state-of-the-art computations. Lewis acidity investigations by the Gutmann-Beckett method and fluoride abstraction experiments indicate a Lewis superacidic nature. The challenging Si?F bond activation of Et3SiF is realized and promising catalytic properties are demonstrated, consolidating the potential applicability of silicon centered Lewis acids in synthetic catalysis.
- Greb, Lutz,Hanusch, Franziska,Inoue, Shigeyoshi,Thorwart, Thadd?us,Tschernuth, Florian S.
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supporting information
p. 25799 - 25803
(2021/11/09)
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- Carbon-Halogen Bond Activation with Powerful Heavy Alkaline Earth Metal Hydrides
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Reaction of [(DIPePBDI)SrH]2 with C6H5X (X=Cl, Br, I) led to hydride-halogenide exchange (DIPePBDI=HC[(Me)CN-2,6-(3-pentyl)phenyl]2). Conversion rates increase with increasing halogen size (FDIPePBDI)SrH]2 with C6H5F was slow and ill-defined but addition of C6H4F2 gave smooth hydride-fluoride exchange. After addition of THF the full range of Sr halogenides was structurally characterized: [(DIPePBDI)SrX ? THF]2 (X=F, Cl, Br, I). Mixtures of AeN“2 and PhSiH3 in situ formed less defined but more robust Ae metal hydride clusters (AexN”yHz, Ae=Ca, Sr, Ba and N“=N(SiMe3)2) which are able to hydrodefluorinate C6H5F. Conversion rates increase with increasing metal size (Ca2/PhSiH3 mixtures also converted SF6 at room temperature to give undefined decomposition products. Addition of Me6Tren to a SrN“2/PhSiH3 led to crystallization of [Sr6N”2H9 ? (Me6Tren)3+][SrN“3?]; Me6Tren=tris[2-(dimethylamino)ethyl]amine). After hydrodefluorination, Sr6N”4F8 ? (Me6Tren)2 was formed and structurally characterized. Dissolution in THF led to cluster growth and the larger cluster Sr16N“8F24 ? (THF)12 is structurally characterized. DFT calculations support that hydrodehalogenation of halobenzenes follows a concerted nucleophilic aromatic substitution mechanism (cSNAr).
- Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Mai, Jonathan,R?sch, Bastian,Wiesinger, Michael
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p. 3731 - 3741
(2021/08/23)
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- Exploiting the radical reactivity of diazaphosphinanes in hydrodehalogenations and cascade cyclizations
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The remarkable reducibility of diazaphosphinanes has been extensively applied in various hydrogenations, based on and yet limited by their well-known hydridic reactivity. Here we exploited their unprecedented radical reactivity to implement hydrodehalogenations and cascade cyclizations originally inaccessible by hydride transfer. These reactions feature a broad substrate scope, high efficiency and simplicity of manipulation. Mechanistic studies suggested a radical chain process in which a phosphinyl radical is generated in a catalytic cycle via hydrogen-atom transfer from diazaphosphinanes. The radical reactivity of diazaphosphinanes disclosed here differs from their well-established hydridic reactivity, and hence, opens a new avenue for diazaphosphinane applications in organic syntheses.
- Cheng, Jin-Pei,Yang, Jin-Dong,Zhang, Jingjing
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p. 4786 - 4790
(2020/06/18)
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- Method for hydrogenolysis of halides
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The invention discloses a method for hydrogenolysis of halides. The invention discloses a preparation method of a compound represented by a formula I. The preparation method comprises the following step: in a polar aprotic solvent, zinc, H2O and a compound represented by a formula II are subjected to a reaction as shown in the specification, wherein X is halogen; Y is -CHRR or R; hydrogenin H2O exists in the form of natural abundance or non-natural abundance. According to the preparation method, halide hydrogenolysis can be simply, conveniently and efficiently achieved through a simple and mild reaction system, and good functional group compatibility and substrate universality are achieved.
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Paragraph 0232; 0242-0244
(2021/01/11)
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- Photoinduced Radical Borylation of Alkyl Bromides Catalyzed by 4-Phenylpyridine
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Utilizing pyridine catalysis, we developed a visible-light-induced transition-metal-free radical borylation reaction of unactivated alkyl bromides that features a broad substrate scope and mild reaction conditions. Mechanistic studies revealed a novel nucleophilic substitution/photoinduced radical formation pathway, which could be utilized to trigger a variety of radical processes.
- Zhang, Li,Wu, Zhong-Qian,Jiao, Lei
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supporting information
p. 2095 - 2099
(2019/12/24)
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- Decyanation method of nitrile organic compound
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The invention provides a decyanation method of a nitrile organic compound. The nitrile organic compound shown in a general formula (1), a sodium reagent, crown ether and a proton donor are subjected to decyanation reaction in an organic solvent I to generate an organic compound shown in a general formula (2). According to the method, a Na/15-crown-5/H2O system is adopted, so that nitrile organic matters can be converted into a decyanation product, and the generation of amine byproducts is inhibited. The new method does not need to use liquid ammonia as a solvent, and is safer and more convenient to operate. The required sodium dispersoid is low in price; and the 15-crown-5 can be recycled and repeatedly used. The method has the advantages of good chemical selectivity, wide substrate application range, good functional group compatibility and the like.
- -
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Paragraph 0099-0102
(2020/02/10)
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- Nitrenium Salts in Lewis Acid Catalysis
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Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen-containing compounds are much rarer. Nitrenium cations are a new family of nitrogen-based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.
- Mehta, Meera,Goicoechea, Jose M.
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supporting information
p. 2715 - 2719
(2020/01/24)
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- ORGANOSILICON ON SOLID OXIDES, AND RELATED COMPLEXES, COMPOSITIONS, METHODS AND SYSTEMS
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Organosilicon Lewis acids supported on activated oxides and metal oxo complexes grafted on the organosilicon Lewis acids as heterogeneous catalysts and the related compositions, methods and systems are described. These organosilicon Lewis acids and the grafted metal oxo complexes catalyze industrially important chemical reactions including, respectively, C—F bond activation and olefin metathesis reactions such as homocoupling and polymerizations.
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Paragraph 0279-0281
(2020/04/09)
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- Bis(perchlorocatecholato)germane: Hard and Soft Lewis Superacid with Unlimited Water Stability
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Previously described Lewis superacids are moisture sensitive and predominantly hard in character—features that severely limit their widespread use in orbital-controlled reactions and under non-inert conditions. Described here are adducts of bis(perchlorocatecholato)germane, the first hard and soft Lewis superacid based on germanium. Remarkably, the synthesis of this compound is performed in water, and the obtained H2O adduct constitutes a strong Br?nsted acid. If applied as an adduct with aprotic donors, it displays excellent activity in a diverse set of Lewis acid catalyzed transformations, covering hydrosilylation, hydrodefluorination, transfer hydrogenation, and carbonyl–olefin metathesis. Given the very straightforward synthetic access from two commercially available precursors, the unlimited water stability and the soft Lewis acidic character, it promotes the transfer of Lewis superacidity into organic synthesis and materials science.
- Greb, Lutz,Roth, Daniel,Wadepohl, Hubert
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supporting information
p. 20930 - 20934
(2020/09/17)
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- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
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The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
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supporting information
p. 11394 - 11398
(2020/05/25)
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- Iron-catalyzed protodehalogenation of alkyl and aryl halides using hydrosilanes
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A simple and efficient iron-catalyzed protodehalogenation of alkyl and aryl halides using phenylhydrosilane is disclosed. The reaction utilizes FeCl3 without the requirement of ligands. Unactivated alkyl and aryl halides were successfully reduced in good yields; sterically hindered tertiary halides were also reduced including the less reactive chlorides. The scalability of this methodology was demonstrated by a gram-scale synthesis with a catalyst loading as low as 0.5 mol%. Notably, disproportionation of phenylsilane leads to diphenylsilane that further reduces the halides. Preliminary mechanistic studies revealed a non-radical pathway and the source of hydrogen is PhSiH3via deuterium labeling studies. Our methodology represents simplicity and provides a good alternative to typical tin, aluminum and boron hydride reagents.
- Pilli, Ramadevi,Balakrishnan, Venkadesh,Chandrasekaran, Revathi,Rasappan, Ramesh
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supporting information
p. 1749 - 1753
(2019/02/20)
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- A Free-Radical Reduction and Cyclization of Alkyl Halides Mediated by FeCl2
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Iron mediated catalytic reactions are of great interest in the field of organic synthesis because they are economic and naturally abundant. However, the use of iron catalyst in the field of free radical cyclization or reduction of alkyl halides remains limited. Here we describe the use of an unprecedented combination of iron and zinc in the reduction and 5-exo-trig radical cyclization of alkyl halides under mild condition in the absence of added ligands or additives. The method is distinguished by its wide scope, functional group tolerance and the use of 1,4-cyclohexadiene as the source of hydrogen, which aids easy purification.
- Pulikottil, Feba Thomas,Pilli, Ramadevi,Murugesan, Vetrivelan,Krishnan, Chandu G.,Rasappan, Ramesh
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p. 2438 - 2442
(2019/04/30)
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- Making JP-10 Superfuel Affordable with a Lignocellulosic Platform Compound
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The synthesis of renewable jet fuel from lignocellulosic platform compounds has drawn a lot of attention in recent years. So far, most work has concentrated on the production of conventional jet fuels. JP-10 is an advanced jet fuel currently obtained from fossil energy. Due to its excellent properties, JP-10 has been widely used in military aircraft. However, the high price and low availability limit its application in civil aviation. Here, we report a new strategy for the synthesis of bio-JP-10 fuel from furfuryl alcohol that is produced on an industrial scale from agricultural and forestry residues. Under the optimized conditions, bio-JP-10 fuel was produced with high overall carbon yields (≈65 %). A preliminary economic analysis indicates that the price of bio-JP-10 fuel can be greatly decreased from ≈7091 US$/ton (by fossil route) to less than 5600 US$/ton using our new strategy. This work makes the practical application of bio-JP-10 fuel forseeable.
- Li, Guangyi,Hou, Baolin,Wang, Aiqin,Xin, Xuliang,Cong, Yu,Wang, Xiaodong,Li, Ning,Zhang, Tao
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supporting information
p. 12154 - 12158
(2019/08/12)
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- Dehydroxymethylation of alcohols enabled by cerium photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/20)
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- Dehydroxymethylation of Alcohols Enabled by Cerium Photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/28)
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- Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
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The general dehalogenation of alkyl halides with zinc using D2O or H2O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.
- Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
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p. 13841 - 13857
(2019/10/17)
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- Reductive Cleavage of Unactivated Carbon-Cyano Bonds under Ammonia-Free Birch Conditions
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A general protocol for the reductive cleavage of unactivated carbon-cyano bonds in aliphatic nitriles has been achieved under single-electron-transfer conditions using Na/15-crown-5/H2O. Electron is supplied by the electride derived from bench-stable sodium dispersions and recoverable 15-crown-5. H2O provides the proton source and suppresses the reduction of aromatic moieties. Compared with the Na/NH3 electride system generated under traditional Birch conditions, this ammonia-free electride system is more practical and features better reactivity and chemoselectivity for the decyanations of a broad range of aliphatic nitriles.
- An, Jie,Ding, Yuxuan,Luo, Shihui,Ma, Lifu
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- Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
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The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
- Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
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supporting information
p. 5599 - 5602
(2019/05/21)
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- Bioinspired Metal-Free Formal Decarbonylation of α-Branched Aliphatic Aldehydes at Ambient Temperature
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A sequence of a Baeyer–Villiger oxidation and a Lewis acid-promoted reduction of the resulting formate with Et3SiH enabled the metal-free formal decarbonylation of tertiary and secondary aliphatic aldehydes. The new methodology mimics the biosynthetic decarbonylation pathway through oxidative C?C bond cleavage rather than the C(O)?H bond activation known from conventional Tsuji–Wilkinson-type reactions. The substrate scope is complementary to existing transition-metal-catalyzed protocols.
- Richter, Sven C.,Oestreich, Martin
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p. 8508 - 8512
(2019/06/04)
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- Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra
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We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.
- Zhang, Dawei,Ronson, Tanya K.,Güryel, Songül,Thoburn, John D.,Wales, David J.,Nitschke, Jonathan R.
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supporting information
p. 14534 - 14538
(2019/10/11)
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- Electron transfer-induced reduction of organic halides with amines
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Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
- Fukuyama, Takahide,Fujita, Yuki,Miyoshi, Hayato,Ryu, Ilhyong,Kao, Shih-Chieh,Wu, Yen-Ku
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supporting information
p. 5582 - 5585
(2018/06/04)
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- Theory and Practice of the Preparation of Adamantylarenes
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Abstract: The adamantylation of diphenyl oxide and phenol with 1-chloro(bromo)adamantanes in a liquid phase has been studied. The reaction has been performed under kinetic control and under the conditions of reaching chemical equilibrium using the following catalysts: Amberlyst 36 Dry, in situ HBr, and AlCl3. The kinetics of isomerization of (1-adamantyl)- and (2-adamantyl)diphenyl oxides has been studied at 333 and 417 K in the presence of AlCl3 and Amberlyst 36 Dry, respectively. The equilibrium of the positional and structural “bridge–bridgehead” isomerization has been studied in the range of 333–523 K. It has been found that high selectivity of the adamantylation of diphenyl oxide or phenol can be achieved in the case of the use of sulfonated cation-exchange resins as a catalyst. In the presence of aluminum halides or HBr, the reaction mixture has been represented by all the possible isomers and adamantane.
- Tarazanov,Shakun,Nesterova,Sarkisova,Naumkin,Nesterov,Repina
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p. 895 - 904
(2018/10/15)
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- Catalysis of Radical Cyclizations from Alkyl Iodides under H2: Evidence for Electron Transfer from [CpV(CO)3H]-
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Radical cyclizations are most often achieved with Bu3SnH in the presence of a radical initiator, but environmental considerations demand that alternative reagents be developed - ones that can serve as a synthetic equivalent to the hydrogen atom. We have revisited [CpV(CO)3H]-, a known replacement for Bu3SnH, and found that it can be used catalytically under H2 in the presence of a base. We have carried out tin-free catalytic radical cyclizations of alkyl iodide substrates. The reactions are atom-efficient, and the conditions are mild, with broad tolerance for functional groups. We have, for example, achieved the first 5-exo radical cyclization involving attack onto a vinyl chloride. We suggest that the radicals are generated by an initial electron transfer.
- Kuo, Jonathan L.,Lorenc, Chris,Abuyuan, Janine M.,Norton, Jack R.
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supporting information
p. 4512 - 4516
(2018/04/10)
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- Thiol-Catalyzed Radical Decyanation of Aliphatic Nitriles with Sodium Borohydride
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Radical decyanation of aliphatic nitriles was achieved in the presence of NaBH4 and a thiol. The reaction proceeds via a radical mechanism involving borane radical anion addition to nitrile to form an iminyl radical, which undergoes carbon-carbon cleavage. Reductive radical addition to acrylonitrile is followed by decyanation to give a two-carbon homologated product in a net radical ethylation reaction.
- Kawamoto, Takuji,Oritani, Kyohei,Curran, Dennis P.,Kamimura, Akio
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supporting information
p. 2084 - 2087
(2018/04/16)
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- Bis(perchlorocatecholato)silane—A Neutral Silicon Lewis Super Acid
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No neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO-CCSD(T)) and experiment (fluoride abstraction from SbF6?). The exceptional affinity towards donors is further demonstrated by, for example, the characterization of an unprecedented SiO4F2 dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.
- Maskey, Rezisha,Sch?dler, Marcel,Legler, Claudia,Greb, Lutz
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supporting information
p. 1717 - 1720
(2018/01/27)
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- Air- and water-stable Lewis acids: Synthesis and reactivity of P-trifluoromethyl electrophilic phosphonium cations
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A new class of electrophilic phosphonium cations (EPCs) containing a -CF3 group attached to the phosphorus(v) center is readily accessible in high yields, via a scalable process. These species are stable to air, water, alcohol and strong Br?nsted acid, even at raised temperatures. Thus, P-CF3 EPCs are more robust than previously reported EPCs containing P-X moieties (X = F, Cl, OR), and despite their reduced Lewis acidity they function as Lewis acid catalysts without requiring anhydrous reaction conditions.
- Fasano,LaFortune,Bayne,Ingleson,Stephan
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supporting information
p. 662 - 665
(2018/02/06)
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- Activation of C?F Bonds by Electrophilic Organosilicon Sites Supported on Sulfated Zirconia
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The reaction of allyltriisopropylsilane with partially dehydroxylated sulfated zirconium oxide (SZO) forms surface organosilicon species. Solid-state NMR studies of the organosilicon functionalized SZO shows that electrophilic [TIPS][SZO] sites are present on the surface, in addition to less reactive TIPS-Ox and SiOx species. The electrophilic [TIPS][SZO] sites are strong Lewis acids from solid-state 31P NMR analysis of triethylphosphine oxide (O=PEt3) contacted materials. [TIPS][SZO] is active in hydrodefluorination reactions in the presence of Et3SiH.
- Culver, Damien B.,Conley, Matthew P.
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supporting information
p. 14902 - 14905
(2018/10/24)
-
- Reevaluation of the Palladium/Carbon-Catalyzed Decarbonylation of Aliphatic Aldehydes
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An improved method for the decarbonylation of aliphatic aldehydes by using a commercially available Pd/C catalyst is described. The reaction conditions are suitable for linear, cyclic, or sterically demanding substrates, as they afford the corresponding alkanes in yields of up to 99%. In addition, this Pd/C-catalyzed method exhibits good functional-group tolerance. A comparison of previously reported methods with the present one showed that the reaction conditions play a crucial role in the outcome of the reaction. The method can also be applied in a two-step reaction sequence for the synthesis of industrially important compounds.
- Ajda?i?, Vladimir,Nikoli?, Andrea,Kerner, Michael,Wipf, Peter,Opsenica, Igor M.
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supporting information
p. 1781 - 1785
(2018/08/12)
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- Interactions of C?F Bonds with Hydridoboranes: Reduction, Borylation and Friedel–Crafts Alkylation
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The stoichiometric reactions of the alkylfluorides 1-fluoroadamantane (Ad-F), fluorocyclohexane (Cy-F), 1-fluoropentane (Pent-F) and benzyl fluorides with secondary boranes pinacolborane (HBpin), catecholborane (HBcat), 9-borabicyclo(3.3.1)nonane (9-BBN)
- Bamford, Karlee L.,Chitnis, Saurabh S.,Qu, Zheng-wang,Stephan, Douglas W.
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supporting information
p. 16014 - 16018
(2018/10/15)
-
- Dual-pathway chain-end modification of RAFT polymers using visible light and metal-free conditions
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We report a metal-free strategy for the chain-end modification of RAFT polymers utilizing visible light. By turning the light source on or off, the reaction pathway in one pot can be switched between either complete desulfurization (hydrogen chain-end) or simple cleavage (thiol chain-end), respectively. The versatility of this process is exemplified by application to a wide range of polymer backbones under mild, quantitative conditions using commercial reagents.
- Discekici, Emre H.,Shankel, Shelby L.,Anastasaki, Athina,Oschmann, Bernd,Lee, In-Hwan,Niu, Jia,McGrath, Alaina J.,Clark, Paul G.,Laitar, David S.,De Alaniz, Javier Read,Hawker, Craig J.,Lunn, David J.
-
supporting information
p. 1888 - 1891
(2017/02/10)
-
- Stannylated Vinylic addition polynorbornene: Probing a reagent for friendly tin-mediated radical processes
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Vinylic addition polynorbornenes (VA-PNB) with stannyl functional groups have been prepared and used in tinmediated radical dehalogenation reactions. The aliphatic and robust scaffold of VA-PNB is well suited for a support in radical processes. VA-PNB-(CH2)nSnHBu2 can be used as a stoichiometric reagent and VA-PNB-(CH2)nSnBu2Cl as a catalyst in the presence of a hydride donor for the reduction of RBr. The mixture KF (aq.)/polymethylhydrosiloxane (PMHS) is the most convenient hydride source to generate VA-PNB-(CH2)nSnHBu2 in situ. Al-though quite popular in this context, boron hydrides, being a source of radicals themselves, are not adequate to correctly evaluate the performance of the anchored organotin group. VAPNB-(CH2)4SnBu2Cl can be recycled and, even if it loses activity upon reuse, it is still useful after ten cycles. The stannylated VAPNB can be separated from the products by simple filtration, and it leads to very low tin contamination (at least 250 times lower than that with use of conventional separation methods).
- García-Loma, Rodrigo,Alb é Niz, Ana C.
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supporting information
p. 4247 - 4254
(2018/08/24)
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- Catalytic Reduction of Alkyl and Aryl Bromides Using Propan-2-ol
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Milstein's complex, (PNN)RuHCl(CO), catalyzes the efficient reduction of aryl and alkyl halides under relatively mild conditions by using propan-2-ol and a base. Sterically hindered tertiary and neopentyl substrates are reduced efficiently, as well as more functionalized aryl and alkyl bromides. The reduction process is proposed to occur by radical abstraction/hydrodehalogenation steps at ruthenium. Our research represents a safer and more sustainable alternative to typical silane, lithium aluminium hydride, and tin-based conditions for these reductions.
- Haibach, Michael C.,Stoltz, Brian M.,Grubbs, Robert H.
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supporting information
p. 15123 - 15126
(2017/11/20)
-
- Initiation in Photoredox C-H Functionalization Reactions. Is Dimsyl Anion a Key Ingredient?
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Previous studies have reported the arylation of unactivated arenes with ArX, base (KOtBu or NaOtBu), and an organic additive at high temperatures. Recently, we showed that this reaction proceeds in the absence of additives at rt but employs UV-vis light. However, details of mechanisms that can use a photoinduced base-promoted homolytic aromatic substitution reaction (photo-BHAS) have remained elusive until now. This work examines different mechanistic routes of the essential electron-transfer step (ET) of this reaction in order to identify a possible path for the formation of 1-adamantyl radicals from 1-haloadamantanes (initiation step). On the basis of photochemical and photophysical experiments and computational studies, we propose an unprecedented initiation step that could also be applied to other ET reactions performed in DMSO. For the first time, it is reported that dimsyl anion, formed from a strong base and DMSO (solvent), is responsible for inducing the initiation by a photo-BHAS process on alkyl halides.
- Budén, María E.,Bardagí, Javier I.,Puiatti, Marcelo,Rossi, Roberto A.
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p. 8325 - 8333
(2017/08/23)
-
- Compounds and methods for the reduction of halogenated hydrocarbons
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The present application relates to methods for the reduction of halogenated hydrocarbons using compounds of Formula (I): wherein the reduction of the halogenated compounds is carried out, for example, under ambient conditions without the need for a transition metal containing co-factor. The present application also relates to methods of recovering precious metals using compounds of Formula (I) that are absorbed onto a support material.
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-
Page/Page column 17
(2017/12/27)
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- Aminopyridine-Borane Complexes as Hydrogen Atom Donor Reagents: Reaction Mechanism and Substrate Selectivity
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Lewis base-borane complexes are shown to be potent hydrogen atom donors in radical chain reduction reactions. Results obtained in 1H, 11B, and 13C NMR measurements and kinetic experiments support a complex reaction mechanism involving the parent borane as well as its initial reaction products as active hydrogen atom donors. Efficient reduction reactions of iodides, bromides, and xanthates in apolar solvents rely on initiator systems generating oxygen-centered radicals under thermal conditions and pyridine-borane complexes carrying solubilizing substituents. In contrast to tin hydride reagents, the pyridine-boranes reduce xanthates faster than the corresponding iodides.
- Barth, Florian,Achrainer, Florian,Pütz, Alexander M.,Zipse, Hendrik
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supporting information
p. 13455 - 13464
(2017/10/05)
-
- 1-Butyl-3-methylimidazol-2-ylidene Borane: A Readily Available, Liquid N-Heterocyclic Carbene Borane Reagent
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1-Butyl-3-methylimidazol-2-ylidene borane has been synthesized directly from two inexpensive commercial reagents: 1-butyl-3-methylimidazolium bromide and sodium borohydride. This NHC-borane reagent is a stable, free-flowing liquid that shows promise for use in radical, ionic, and metal-catalyzed reactions.
- Bolt, Daniel A.,Curran, Dennis P.
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p. 13746 - 13750
(2017/12/26)
-
- Metal-free pincer ligand chemistry polycationic phosphonium Lewis acids
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Oxidation of 2,6-bis(diphenylphosphine)methyl pyridine with MeO3SCF3, yields the dication [2,6-(CH2PMePh2)2C5H3N][CF3SO3]22, while subsequent treatment with two equivalents of [K(THF)n][B(C6F5)4] (n = 1.3-1.5) afforded [2,6-(CH2PMePh2)2C5H3N][B(C6F5)4]23. Analogous treatment using XeF2 afforded 2,6-(CH2PF2Ph2)2C5H3N 4, while subsequent fluoride abstractions afford the corresponding [BF4], [CF3SO3] and [B(C6F5)4] salts, 5-7, respectively. Compound 4 reacts with an excess of MeO3SCF3 to give [2,6-(CH2PF2Ph2)2C5H3N(CH3)][CF3SO3] 8 while subsequent reaction with [Et3Si·2C7H8][B(C6F5)4] gave the related tricationic species, 9. The Lewis acidity of these di- and triphosphonium cations 3, 7 and 9 was examined and their utility as Lewis acid catalysts was assessed in the dimerization of 1,1-diphenylethylene, the hydrodefluorination of 1-fluoroadamantane, and the dehydrocoupling of phenol and silane.
- Szkop, Kevin M.,Stephan, Douglas W.
-
supporting information
p. 3921 - 3928
(2017/03/27)
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- Radical Hydrodeiodination of Aryl, Alkenyl, Alkynyl, and Alkyl Iodides with an Alcoholate as Organic Chain Reductant through Electron Catalysis
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A simple and efficient method for radical hydrodeiodination is reported. The novel approach uses electron catalysis. In situ generated Na-alcoholates are introduced as radical chain reducing reagents and reactions work with O2as cheap initiator. Hydrodeiodination works on aryl, alkenyl, alkynyl iodides and a tert-alkyl iodide also gets reduced applying the method. Albeit less general, the method is also applicable to the reduction of aryl bromides. The novel reagent is successfully used to conduct typical reductive radical cyclization reactions and mechanistic studies are reported.
- Dewanji, Abhishek,Mück-Lichtenfeld, Christian,Studer, Armido
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supporting information
p. 6749 - 6752
(2016/06/09)
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- Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions
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When used with trialkylboranes, catechol derivatives, which are low-cost and low toxicity, are valuable hydrogen atom donors for radical chain reactions involving alkyl iodides and related radical precursors. The system 4-tert-butylcatechol/triethylborane has been used to reduce a series of secondary and tertiary iodides, a xanthate, and a thiohydroxamate ester. Catechol derivatives are right in the optimal kinetic window for synthetic applications, as demonstrated by highly efficient radical cyclizations. Cyclizations leading to the formation of quaternary centers can be performed in an all-at-once process (no slow addition of the hydrogen atom donor) at standard concentrations. The H-donor properties of catechol derivatives can be fine-tuned by changing their substitution pattern. In slow radical cyclization processes, an enhanced ratio of cyclized/uncyclized products was obtained by using 3-methoxycatechol instead of 4-tert-butylcatechol.
- Povie, Guillaume,Ford, Leigh,Pozzi, Davide,Soulard, Valentin,Villa, Giorgio,Renaud, Philippe
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supporting information
p. 11221 - 11225
(2016/10/13)
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- Electrophilic phosphonium cations (EPCs) with perchlorinated-aryl substituents: Towards air-stable phosphorus-based Lewis acid catalysts
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A series of phosphines incorporating (C6Cl5) substituents, Ph2P(C6Cl5) 1, PhP(C6Cl5)22, P(C6Cl5)33 and (C6F5)P(C6Cl5)24 were prepared. In the case of 1, 2 and 4, these were converted to the corresponding aryl-difluorophosphoranes 5-7via reaction with XeF2, whereas reaction of 3 with XeF2 afforded only an inseparable mixture of products. The compounds 5-7 were converted to the fluorophosphonium cations 8-10, whereas the reaction of 3 with Selectfluor afforded (C6Cl5)2POF and (C6Cl5)2. The fluorophosphonium salts showed evidence of improved air stability as well as Lewis acid catalytic activity in hydrodefluorination, hydrosilylation, deoxygenation and dehydrocoupling chemistry.
- Postle, Shawn,Podgorny, Vitali,Stephan, Douglas W.
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p. 14651 - 14657
(2016/10/03)
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