- Cobalt-catalyzed oxidative cyclization of gem-disubstituted conjugated alkenols
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Aryl gem-disubstituted conjugated alkenols underwent oxidative cyclization affording 2,5,5-trisubstituted tetrahydrofurans in reasonable yields and good diastereoselectivities using the reductive termination variation of the Mukaiyama aerobic oxidative reaction. Under oxidative termination, the same alkenols produced diols and ketonic by-products via the double hydration and beta-scission competing pathways. Furthermore, the differences in alkenol reactivity under the reductive and oxidative termination conditions were investigated.
- Alves, Tania M.F.,Costa, Mateus O.,Bispo, Beatriz A.D.,Pedrosa, Fabiana L.,Ferreira, Marco A.B.
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supporting information
p. 3334 - 3338
(2016/07/11)
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- Synthesis of cycloalkanone-fused cyclopropanes by Au(I)-catalyzed oxidative ene-yne cyclizations
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Au(I)-catalyzed oxidative cyclizations that successfully convert 1,5-ene-ynes and a 1,6-ene-yne to the corresponding cycloalkanone-fused cyclopropanes are described. This Au(I)-catalyzed oxidative cyclization can be effectively applied to various substrat
- Uetake, Yuta,Niwa, Takashi,Nakada, Masahisa
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supporting information
p. 6847 - 6850
(2015/01/09)
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- Enantioselective synthesis of tetrahydrofuran derivatives by sequential henry reaction and iodocyclization of γ,δ-unsaturated alcohols
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A sequential one-pot Cu-catalyzed asymmetric Henry reaction and iodocyclization is disclosed. The transformation provides efficient access to biologically and synthetically useful 2,2,5-trisubstituted tetrahydrofuran derivatives. The combination of Cu(OAc)2·H2O with a novel chiral sulfoxide-Schiff base hybrid ligand under mild reaction conditions tolerates a wide range of 4-substituted γ,δ-unsaturated aldehydes, and the subsequent iodocyclization furnishes the corresponding products in generally high yields with excellent enantioselectivities. The products can be easily converted into amines with excellent diastereo- and enantioselectivities.
- Chen, Li-Yan,Chen, Jia-Rong,Cheng, Hong-Gang,Lu, Liang-Qiu,Xiao, Wen-Jing
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supporting information
p. 4714 - 4719
(2014/08/05)
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- Catalytic asymmetric intramolecular hydroacylation with rhodium/phosphoramidite-alkene ligand complexes
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Give me a P: An asymmetric intramolecular Rh-catalyzed hydroacylation reaction of pent-4-enals for the preparation of functionalized cyclopentanones in good yield and high enantioselectivity is described (see scheme, DCE=dichloroethane). This process uses rhodium complexes featuring novel modular phosphoramidite-alkene ligands and achiral phosphine coligands. Copyright
- Hoffman, Thomas J.,Carreira, Erick M.
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supporting information; experimental part
p. 10670 - 10674
(2011/12/05)
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- Air-tolerant C-C bond formation via organometallic ruthenium catalysis: diverse catalytic pathways involving (C5Me5)Ru or (C5H5)Ru are robust to molecular oxygen
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Ruthenium-catalyzed substitutions of carbon pronucleophiles, various [2+2+2] cycloadditions, and addition of a diazo compound to an alkyne are shown to proceed in the presence of air. Notably diverse catalytic manifolds remain supported under conditions generally regarded as prohibitive. Building on rare reports from the literature we show that a range of organometallic transformations based on reaction intermediates derived from (C5Me5)Ru or (C5H5)Ru moieties are air-compatible.
- Severa, Luká?,Vávra, Jan,Kohoutová, Anna,?í?ková, Martina,?álová, Tereza,Hyvl, Jakub,?aman, David,Pohl, Radek,Adriaenssens, Louis,Teply, Filip
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supporting information; experimental part
p. 4526 - 4528
(2009/12/03)
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- Rhodium-catalyzed intramolecular, anti-Markovnikov hydroamination. Synthesis of 3-arylpiperidines
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The intramolecular anti-Markovnikov hydroamination of 1-(3-aminopropyl)vinylarenes in the presence of a readily available rhodium catalyst to form 3-arylpiperidines is reported. In contrast to intermolecular hydroamination of vinylarenes, which occurred in high yields in the presence of rhodium catalysts containing DPEphos, the intramolecular reaction occurred in high yield in the presence of [Rh(COD)(DPPB)]BF4 as catalyst. Reactants with substituents β to the nitrogen occurred in high yield, and these reactions formed 3,5-disubstituted piperidines with high diastereomeric excess. The regiochemistry of these cyclizations contrasts with the regiochemistry of intramolecular hydroaminations catalyzed by lanthanide complexes, group III metal complexes, and platinum complexes, all of which have been reported to form cyclization products from Markovnikov addition. Copyright
- Takemiya, Akihiro,Hartwig, John F.
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p. 6042 - 6043
(2007/10/03)
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- Synthesis of cyclic peroxides by chemo- and regioselective peroxidation of dienes with Co(II)/O2/Et3SiH
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(Chemical Equation Presented). In the competitive peroxidation of mixtures of two alkenes with Co(II)/O2/Et3SiH, it was found that the relative reactivities of the alkene substrates are influenced by three major factors:. (1) relative stability of the intermediate carbon-centered radical formed by the reaction of the alkene with HCo(III) complex, (2) steric effects around the C=C double bond, and (3) electronic factors associated with the C=C double bond. Consistent with results from simple alkenes, the chemo-and regioselective peroxidation of dienes was also realized. Depending on the diene structure, the product included not only the expected acyclic unsaturated triethylsilyl peroxides but also 1,2-dioxolane and 1,2-dioxane derivatives via intramolecular cyclization of the unsaturated peroxy radical intermediates.
- Tokuyasu, Takahiro,Kunikawa, Shigeki,McCullough, Kevin J.,Masuyama, Araki,Nojima, Masatomo
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p. 251 - 260
(2007/10/03)
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- Mechanistic investigation of a novel vitamin B12-catalyzed carbon-carbon bond forming reaction, the reductive dimerization of arylalkenes
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In the presence of catalytic vitamin B12 and a reducing agent such as Ti(III)citrate or Zn, arylalkenes are dimerized with unusual regioselectivity forming a carbon-carbon bond between the benzylic carbons of each coupling partner. Dimerization products were obtained in good to excellent yields for mono- and 1,1-disubstituted alkenes. Dienes containing one aryl alkene underwent intramolecular cyclization in good yields. However, 1,2-disubstituted and trisubstituted alkenes were unreactive. Mechanistic investigations using radical traps suggest the involvement of benzylic radicals, and the lack of diastereoselectivity in the product distribution is consistent with dimerization of two such reactive intermediates. A strong reducing agent is required for the reaction and fulfills two roles. It returns the Co(II) form of the catalyst generated after the reaction to the active Co(I) state, and by removing Co(II) it also prevents the nonproductive recombination of alkyl radicals with cob(II)alamin. The mechanism of the formation of benzylic radicals from arylalkenes and cob(I)alamin poses an interesting problem. The results with a one-electron transfer probe indicate that radical generation is not likely to involve an electron transfer. Several alternative mechanisms are discussed.
- Shey, Justin,McGinley, Chris M.,McCauley, Kevin M.,Dearth, Anthony S.,Young, Brian T.,Van der Donk, Wilfred A.
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p. 837 - 846
(2007/10/03)
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- Ruthenium-catalysed coupling of allyl alcohol with alkynes: A new route to γ,δ-unsaturated acetals and aldehydes
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γ,δ-Unsaturated acetals and aldehydes have been obtained via a new ruthenium-catalysed coupling of allyl alcohol with alkynes. The branched isomer is regioselectively formed. Comparative studies of catalyst precursors have shown that (C5Me5)Ru(IV) derivatives favours the formation of acetals and that, with (C5Me5)Ru(II) moieties, the reaction can be carried out either in water or without solvent at room temperature.
- Derien,Jan,Dixneuf
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p. 5511 - 5524
(2007/10/03)
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- Asymmetric catalysis. Asymmetric catalytic intramolecular hydroacylation of 4-pentenals using chiral rhodium diphosphine catalysts
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Catalysts of the type [Rh(chiral diphosphine)]+ convert 4-substituted 4-pentenals into the corresponding 3-substituted cyclopentanones with generally high turnover numbers and frequencies at 25 °C. The enantioselectivities of various substituted 4-pentenals with two chiral diphosphines have been explored. It was found that with the binap catalyst, almost complete enantioselectivity is observed for 4-pentenal substrates bearing 4-substituted tertiary substituents and for ester groups. Ketonic substituents give very high enantioselectivities. The mechanism of intramolecular hydroacylation has been explored, and it is suggested that an important consideration for obtaining high turnover frequencies is related to the acyl-alkyl reductive elimination mechanism which is inferred to occur by a process similar to ester hydrolysis. The origin of the enantioselection is discussed in terms of the interactions between the phenyl groups of the phosphine and the substituent of the pentenal.
- Barnhart, Richard W.,Wang, Xianqi,Noheda, Pedro,Bergens, Steven H.,Whelan, John,Bosnich
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p. 1821 - 1830
(2007/10/02)
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- Ruthenium Catalysed Synthesis of Unsaturated Acetals and Aldehydes via C-C Bond Coupling of Alkynes with Allyl Alcohol
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Terminal alkynes and allyl alcohol are coupled, with carbon-carbon bond formation, in the presence of a RuIV(C5Me5) catalyst, to give γ,δ-unsaturated acetals and with 4> or preferentially to produce the branched γ,δ-unsaturated aldehydes.
- Derien, Sylvie,Dixneuf, Pierre H.
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p. 2551 - 2552
(2007/10/02)
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- Asymmetric cyclization reactions. Cyclization of substituted 4-pentenals into cyclopentanone derivatives by Rhodium(I) with chiral ligands
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Asymmetric cyclization of substituted 4-pentenals (Ia,b,c; IIa,b,c,d)by Rh(I) with chiral ligands was tested, and substrate (IId) with a bulkier substituent at C4 underwent more stereoselective cyclization by Rh(I)-((+)-DIPMC) to yield substitu
- Taura,Tanaka,Wu,Funakoshi,Sakai
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p. 4879 - 4888
(2007/10/02)
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- 4- AND 5-Phenyl pentenal acetals
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4- and 5-Phenyl pentenal acetals having the structure: STR1 wherein one of X and Y is phenyl and the other of X and Y is hydrogen and A is the moiety: STR2 WHEREIN Rb and Rb ' are separately the same or different lower alkyl or Rsub
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- Processes for producing 4- and 5-phenyl pentenals
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Described are processes for preparing novel 4- and 5-phenyl-pentenals, lower alkyl and lower alkylene acetals thereof having the structure: STR1 wherein one of X and Y is phenyl and the other of X and Y is hydrogen and A is a moiety selected from the grou
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