- Skeletal editing through direct nitrogen deletion of secondary amines
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Synthetic chemistry aims to build up molecular complexity from simple feedstocks1. However, the ability to exert precise changes that manipulate the connectivity of the molecular skeleton itself remains limited, despite possessing substantial potential to expand the accessible chemical space2,3. Here we report a reaction that ‘deletes’ nitrogen from organic molecules. We show that N-pivaloyloxy-N-alkoxyamides, a subclass of anomeric amides, promote the intermolecular activation of secondary aliphatic amines to yield intramolecular carbon–carbon coupling products. Mechanistic experiments indicate that the reactions proceed via isodiazene intermediates that extrude the nitrogen atom as dinitrogen, producing short-lived diradicals that rapidly couple to form the new carbon–carbon bond. The reaction shows broad functional-group tolerance, which enables the translation of routine amine synthesis protocols into a strategy for carbon–carbon bond constructions and ring syntheses. This is highlighted by the use of this reaction in the syntheses and skeletal editing of bioactive compounds.
- Kennedy, Sean H.,Dherange, Balu D.,Berger, Kathleen J.,Levin, Mark D.
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p. 223 - 227
(2021/05/19)
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- Chemoselective Hydrogenation of Alkynes to (Z) -Alkenes Using an Air-Stable Base Metal Catalyst
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A highly selective hydrogenation of alkynes using an air-stable and readily available manganese catalyst has been achieved. The reaction proceeds under mild reaction conditions and tolerates various functional groups, resulting in (Z)-alkenes and allylic alcohols in high yields. Mechanistic experiments suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperativity.
- Zubar, Viktoriia,Sklyaruk, Jan,Brzozowska, Aleksandra,Rueping, Magnus
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supporting information
p. 5423 - 5428
(2020/07/24)
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- "bulky-Yet-Flexible" α-Diimine Palladium-Catalyzed Reductive Heck Cross-Coupling: Highly Anti-Markovnikov-Selective Hydroarylation of Alkene in Air
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To pursue a highly regioselective and efficient reductive Heck reaction, a series of moisture-and air-stable α-diimine palladium precatalysts were rationally designed, readily synthesized, and fully characterized. The relationship between the structures of the palladium complexes and the catalytic properties was investigated. It was revealed that the"bulky-yet-flexible"palladium complexes allowed highly anti-Markovnikov-selective hydroarylation of alkenes with (hetero)aryl bromides under aerobic conditions. Further synthetic application of the present protocol could provide rapid and straightforward access to functional and biologically active molecules.
- Yang, Xu-Wen,Li, Dong-Hui,Song, A-Xiang,Liu, Feng-Shou
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p. 11750 - 11765
(2020/10/23)
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- Celite-Polyaniline supported palladium catalyst for chemoselective hydrogenation reactions
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Polyaniline coated on particles of celite is used as support to load palladium catalyst. This heterogenized Celite?PANI?Pd system, is used as an efficient catalyst for chemoselective hydrogenation reactions. The catalyst is characterized by usual spectral, analytical techniques and studied for hydrogenation reactions at ambient conditions. The mild reaction conditions allow the control over the reactions and excellent selectivity is achieved in number of conversions. Hydrogenation of a carbon–carbon double bond was favored over other polar π-bond systems, while labile functional groups such as benzyl ether, benzyl esters, cyano, nitro and halogen remained unaffected. Primary amines were converted to N,N-dimethyl amines with formaldehyde, the double bond of coumarin was selectively hydrogenated without opening of the lactone functionality.
- Patel, Heta A.,Rawat, Maitreyee,Patel, Arun L.,Bedekar, Ashutosh V.
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- Using alcohols as simple H2-equivalents for copper-catalysed transfer semihydrogenations of alkynes
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Copper(i)/N-heterocyclic carbene complexes enable a transfer semihydrogenation of alkynes employing simple and readily available alcohols such as isopropanol. The practical overall protocol circumvents the use of commonly employed high pressure equipment when using dihydrogen (H2) on the one hand, and avoids the generation of stoichiometric silicon-based waste on the other hand, when hydrosilanes are used as terminal reductants.
- Kaicharla, Trinadh,Zimmermann, Birte M.,Oestreich, Martin,Teichert, Johannes F.
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supporting information
p. 13410 - 13413
(2019/11/14)
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- Nickel-catalyzed anti-Markovnikov hydroarylation of alkenes
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We have developed a nickel-catalyzed hydroarylation of alkenes using aryl halides as coupling partners. Excellent anti-Markovnikov selectivity is achieved with aryl-substituted alkenes and enol ethers. We also show that hydroarylation occurs with alkyl substituted alkenes to yield linear products. Preliminary examination of the reaction mechanism suggests irreversible hydrometallation as the selectivity determining step of the hydroarylation.
- Nguyen, Julia,Chong, Andrea,Lalic, Gojko
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p. 3231 - 3236
(2019/03/21)
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- An N-heterocyclic carbene ligand promotes highly selective alkyne semihydrogenation with copper nanoparticles supported on passivated silica
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We report a surface organometallic route that generates copper nanoparticles (NPs) on a silica support while simultaneously passivating the silica surface with trimethylsiloxy groups. The material is active for the catalytic semihydrogenation of phenylalkyl-, dialkyl- and diaryl-alkynes and displays high chemo- and stereoselectivity at full alkyne conversion to corresponding (Z)-olefins in the presence of an N-heterocyclic carbene (NHC) ligand. Solid-state NMR spectroscopy using the NHC ligand 13C-labeled at the carbenic carbon reveals a genuine coordination of the carbene to Cu NPs. The presence of distinct Cu surface environments and the coordination of the NHC to specific Cu sites likely account for the increased selectivity.
- Kaeffer, Nicolas,Liu, Hsueh-Ju,Lo, Hung-Kun,Fedorov, Alexey,Copéret, Christophe
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p. 5366 - 5371
(2018/06/27)
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- Copper-catalyzed cross-coupling of aryl-, primary alkyl-, and secondary alkylboranes with heteroaryl bromides
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A method for the Cu-catalyzed cross-coupling of both aryl and alkylboranes with aryl bromides is described. The method employs an inexpensive Cu-catalyst and functions for a variety of heterocyclic as well as electron deficient aryl bromides. In addition, aryl iodides of varying substitution patterns and electronic properties work well.
- Bergmann, Allison M.,Oldham, Adam M.,You, Wei,Brown, M. Kevin
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supporting information
p. 5381 - 5384
(2018/06/01)
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- Stable Zero-Valent Nickel Nanoparticles in Glycerol: Synthesis and Applications in Selective Hydrogenations
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Small (mean diameter, ca. 1.2 nm) and well-dispersed zero-valent nickel nanoparticles (NiNPs) stabilized by cinchona-based alkaloids and TPPTS (tris(3-sulfophenyl)phosphine trisodium salt), were synthesized from the organometallic precursor [Ni(cod)2] in neat glycerol under hydrogen pressure. NiNPs were fully characterized ((HR)-TEM, EDX, XPS, XRD, IR, magnetization), both at solid state and directly from the corresponding colloidal solutions in glycerol due to its negligible vapour pressure. NiNPs dispersed in glycerol were applied in hydrogenation reactions, in particular in semihydrogenation of alkynes to give (Z)-alkenes under satisfactory conditions (3 bar H2, 1 mol% Ni, 100 °C), showing remarkable activity and selectivity. The catalytic phase was recycled at least ten times without loss of activity, affording in each case metal-free organic products. Other functional groups such as nitro, nitrile and formyl groups were efficiently hydrogenated to the corresponding anilines, benzylamines and benzylalcohols respectively (77–95% yields). (Figure presented.).
- Reina, Antonio,Favier, Isabelle,Pradel, Christian,Gómez, Montserrat
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supporting information
p. 3544 - 3552
(2018/08/01)
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- Copper-Catalyzed Radical Reductive Arylation of Styrenes with Aryl Iodides Mediated by Zinc in Water
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A copper/aniline catalyst system enables the radical arylation of styrenes using aryl iodides mediated by zinc in water. This transformation provides an efficient synthetic methodology for the convenient synthesis of diarylethane.
- Zhou, Feng,Hu, Xiaoyun,Zhang, Wanying,Li, Chao-Jun
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supporting information
p. 7416 - 7422
(2018/05/14)
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- Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI2
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An efficient E-selective semihydrogenation of internal alkynes was developed under low dihydrogen pressure and low reaction temperature from commercially available reagents: Cl2Pd(PPh3)2, Zn0, and ZnI2. Kinetic studies and control experiments underline the significant role of ZnI2 in this process under H2 atmosphere, establishing that the transformation involves syn-hydrogenation followed by isomerization. This simple and easy-to-handle system provides a route to E-alkenes under mild conditions.
- Maazaoui, Radhouan,Abderrahim, Raoudha,Chemla, Fabrice,Ferreira, Franck,Perez-Luna, Alejandro,Jackowski, Olivier
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supporting information
p. 7544 - 7549
(2019/01/03)
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- Harnessing Alkyl Amines as Electrophiles for Nickel-Catalyzed Cross Couplings via C-N Bond Activation
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We developed a strategy to harness alkyl amines as alkylating agents via C-N bond activation. This Suzuki-Miyaura cross coupling of alkylpyridinium salts, readily formed from primary amines, is the first example of a metal-catalyzed cross coupling via C-N bond activation of an amine with an unactivated alkyl group. This reaction enjoys broad scope and functional group tolerance. Primary and secondary alkyl groups can be installed. Preliminary studies suggest a NiI/NiIII catalytic cycle.
- Basch, Corey H.,Liao, Jennie,Xu, Jianyu,Piane, Jacob J.,Watson, Mary P.
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p. 5313 - 5316
(2017/04/27)
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- Deoxygenation of carbonyl compounds using an alcohol as an efficient reducing agent catalyzed by oxo-rhenium complexes
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This work describes the first methodology for the deoxygenation of carbonyl compounds using an alcohol as a green solvent/reducing agent catalyzed by oxo-rhenium complexes. The system 3-pentanol/ReOCl3(SMe2)(OPPh3) was successfully employed in the deoxygenation of several aryl ketones to the corresponding alkenes and also in the deoxygenation of aryl aldehydes to alkanes with moderate to excellent yields. The catalyst ReOCl3(SMe2)(OPPh3) can also be used in several catalytic cycles with good activity.
- Bernardo, Joana R.,Fernandes, Ana C.
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supporting information
p. 2675 - 2681
(2016/05/24)
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- Plasma synthesis of oxidized graphene foam supporting Pd nanoparticles as a new catalyst for one-pot synthesis of dibenzyls
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We have developed an environmentally-friendly method for the synthesis of Pd nanoparticle (Pd NPs) decorated different graphene supports, and the morphology and structure of the hybrids are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and elemental mappings. Four hybrid materials based on graphene foam (GF), oxidized graphene foam (OGF), graphene oxide (GO) and reduced graphene oxide (RGO) have been used to catalyze Heck coupling reactions, and the effect of support on the activity of the hybrid material has been studied. Our results have revealed that Pd NP decorated OGF (Pd/OGF) is the most active catalyst, showing better performance than the commercial Pd/C catalyst. More importantly, the Pd/OGF catalyst has been successfully used for one-pot synthesis of dibenzyls with different aryl bromides and olefins, which has simplified the separation and purification process and realized a green organic synthesis process. This journal is
- Ren, Liang,Yang, Fan,Wang, Chunxia,Li, Yongfeng,Liu, Hailing,Tu, Zhiqiang,Zhang, Liqiang,Liu, Zhichang,Gao, Jinsen,Xu, Chunming
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p. 63048 - 63054
(2015/02/19)
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- Iron pincer complex catalyzed, environmentally benign, E-selective semi-hydrogenation of alkynes
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Ironing out hydrogenation: For the first time, an iron catalyst provided chemo- and stereo-selective semi-hydrogenation of alkynes to E-alkenes. This efficient, atom-economical reaction is catalyzed by a novel acridine-based PNP iron pincer catalyst and exhibits excellent functional group tolerance under mild, neutral, environmentally benign reaction conditions. Copyright
- Srimani, Dipankar,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 14131 - 14134
(2014/01/06)
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- Functional group tolerant Kumada-Corriu-Tamao coupling of nonactivated alkyl halides with aryl and heteroaryl nucleophiles: Catalysis by a nickel pincer complex permits the coupling of functionalized Grignard reagents
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A nickel(II) pincer complex [(MeNN2)NiCl] (1) catalyzes Kumada-Corriu-Tamao cross coupling of nonactivated alkyl halides with aryl and heteroaryl Grignard reagents. The coupling of octyl bromide with phenylmagnesium chloride was used as a test reaction. Using 3 mol % of 1 as the precatalyst and THF as the solvent, and in the presence of a catalytic amount of TMEDA, the coupling product was obtained in a high yield. The reaction conditions could be applied to cross coupling of other primary and secondary alkyl bromides and iodides. The coupling is tolerant to a wide range of functional groups. Therefore, alkyl halides containing ester, amide, ether, thioether, alcohol, pyrrole, indole, furan, nitrile, conjugated enone, and aryl halide moieties were coupled to give high isolated yields of products in which these units stay intact. For the coupling of ester-containing substrates, O-TMEDA is a better additive than TMEDA. The reaction protocol proves to be efficient for the coupling of Knochel-type functionalized Grignard reagents. Thus aryl Grignard reagents containing electron-deficient and/or sensitive ester, nitrile, amide, and CF3 substituents could be successfully coupled to nonactivated and functionalized alkyl iodides. The catalysis is also efficient for the coupling of alkyl iodides with functionalized heteroaryl Grignard reagents, giving rise to pyridine-, thiophene-, pyrazole-, furan-containing molecules with additional functionalities. Concerning the mechanism of the catalysis, [(MeNN2)Ni-(hetero)Ar] was identified as an intermediate, and the activation of alkyl halides was found to take place through a radical-rebound process.
- Vechorkin, Oleg,Proust, Valerie,Hu, Xile
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supporting information; experimental part
p. 9756 - 9766
(2011/03/19)
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- Efficient heterogeneously palladium-catalysed synthesis of stilbenes and bibenzyls
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An alternative heterogeneously palladium catalysed procedure for the synthesis of functional stilbenes and bibenzyls is reported. Starting from aryl bromides and using simple commercially available Pd/C catalyst at a low catalytic rate (1 mol%), stilbenes are obtained with 30-100% GC-yields and bibenzyls are produced in a one-pot fashion with 27-100% GC-yields. The procedure showed, however, some limitations when applied to strongly deactivated aryl bromides that could be in some extent overcome by using corresponding iodo derivatives.
- Cusati, Giuseppe,Wedig, Anja,Djakovitch, Laurent
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scheme or table
p. 77 - 81
(2010/04/23)
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- Highly selective palladium-catalyzed oxidative Csp2-Csp 3 cross-coupling of arylzinc and alkylindium reagents through double transmetallation
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Using desyl chloride (2-chloro-1,2-diphenylethanone) as the oxidant, the palladium-catalyzed reaction of arylzinc with alkylindium reagents occurred smoothly in a highly selective manner to afford the products in 57-90% yields. Preliminary kinetic data in
- Jin, Liqun,Zhao, Yingsheng,Zhu, Lizheng,Zhang, Heng,Lei, Aiwen
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supporting information; experimental part
p. 630 - 634
(2009/11/30)
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- Palladium-catalyzed heck coupling-hydrogenation: Highly efficient one-pot synthesis of dibenzyls and alkyl phenyl esters
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An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters via sequential Heck coupling and hydrogenation of the alkenyl double bond in one pot with a single recyclable catalyst under mild conditions has been realised. The catalyst was recovered by simple filteration and reused for several cycles with consistent activity.
- Kantam, M. Lakshmi,Chakravarti, Rajashree,Chintareddy, Venkat Reddy,Sreedhar,Bhargava, Suresh
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supporting information; experimental part
p. 2544 - 2550
(2009/08/14)
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- Stereoselective debromination and selective reduction of vic-dibromides with nickel boride
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A simple procedure is reported for the stereoselective debromination of vic-dibromides with nickel boride at ambient temperature. Debromination with concomitant reduction of vic-dibromides to give dihydro products in a one-pot reaction is also reported. α,β-Dibromoketones can also be converted to their corresponding alcohols.
- Khurana, Jitender M.,Kandpal, Bhaskar M.,Kukreja, Gagan,Sharma, Purnima
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p. 1019 - 1023
(2007/10/03)
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- New One-pot Cross-coupling Reaction between Grignard Reagents and Alkoxymethyldiphenylphosphonium Iodides in situ-Formed from Alcohols, Chlorodiphenylphosphine and Iodomethane
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A new one-pot cross-coupling reaction between Grignard reagents and alkoxymethyldiphenylphosphonium iodides, which were in situ-formed from nBuLi-treated alcohols, chlorodiphenylphosphine and iodomethane, proceeded smoothly to afford the corresponding coupling products in good to high yields.
- Shintou, Taichi,Kikuchi, Wataru,Mukaiyama, Teruaki
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p. 676 - 677
(2007/10/03)
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- Cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides
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The cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides has been successfully achieved using PdCl2(dppf)·CH2Cl2 in the presence of potassium carbonate to provide the corresponding Su
- Molander, Gary A.,Yun, Chang-Soo
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p. 1465 - 1470
(2007/10/03)
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- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
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- Micellar Systems as ''Supercages'' for Reactions of Geminate Radical Pairs. Magnetic Effects
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The photochemistry of dibenzyl ketone (DBK) and other molecules capable of producing benzyl radicals and substituted benzyl radicals has been investigated in micellar systems.The cage effect (percent of unscavengeable radical pairs produced by photolysis) was measured under a variety of conditions, and the results are compared with those obtained in homogeneous organic solvents.For example, parameters such as mean occupancy of ketone, detergent type and concentration, O2 concentration, additives, temperature, applied magnetic field, and pressure have been varied and investigated as to their influence on the magnitude of cage effect.In addition to modifying its environment, structural modification of the DBK by incorporation of 2H and 13C isotopes, hydrophobic groups, and heavy atoms was performed to investigate the impact of these variations on the cage effect in micellar systems.Isotopic substitution of 2H or 13C leads to results on both the quantum yields for reactions and on the percent cage that were consistent with expectations of magnetic isotope effects.Hydrophobic groups substituted in the 4-position of DBK were found to cause a substantial increase in the cage effect and yet retain the magnetic-field-dependent character found in the parent DBK.Incorporation of Br in the 4-position of DBK was found to enhance the cage effect but at the same time cause the cage effect to become magnetic field independent.Substitution of α-naphthyl for phenyl in DBK also produced magnetic-field-independent behavior, in addition to a dramatic decrease in the efficiency of photolysis.
- Turro, Nicholas J.,Weed, Gregory C.
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p. 1861 - 1868
(2007/10/02)
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- Chemistry of the tert-Butyl Radical: Polar Character, ρ Value for Reaction with Toluenes, and the Effect of Radical Polarity on the Ration of Benzylic Hydrogen Abstraction to Addition to Aromatic Rings
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We have reexamined the reactions of tert-butyl radicals with toluenes and have obtained a ρ value of 0.49 +/- 0.04 at 80 deg C.The new, independent system involves the quantification of all of the principal products from the reaction of tert-butyl radicals with mixtures of toluene and substituted toluene.Five major products contain benzyl fragments and are formed in significant yields: two symmetrical bibenzyls, the cross bibenzyl, and the two neopentylbenzenes that result from combination of tert-butyl and the two benzyl radicals.Attack on the side chain is a major reaction of free tert-butyl radicals and is the only significant reaction that they undergo other than cage and termination reactions. tert-Butyl radicals do not add to the ring of toluenes.Data on the relative rates of addition to benzenes and hydrogen abstraction from toluenes are collected for a series of radicals including hydrogen atoms; methyl, isopropyl, and tert-butyl radicals; and p-nitrophenyl, p-bromophenyl, and phenyl radicals.The data demonstrate that more electrophilic radicals have a larger tendency to add to rings whereas more nucleophilic radicals have a larger tendency to abstract benzylic hydrogens.
- Pryor, William A.,Tang, Felicia Y.,Tang, Robert H.,Church, Daniel F.
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p. 2885 - 2891
(2007/10/02)
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