- Enantioselective Isothiourea-Catalysed Michael-Michael-Lactonisation Cascade Reaction for the Synthesis of δ-Lactones and 1,2,3,4-Substituted Cyclopentanes
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This manuscript describes the application of α,β-unsaturated acyl ammonium intermediates in a Michael-Michael-lactonisation cascade process to furnish δ-lactones. Generation of α,β-unsaturated acyl ammonium intermediates was achieved upon addition of isothiourea catalyst HyperBTM into α,β-unsaturated acid chlorides. Subsequent reaction with enone-malonates gave access to δ-lactones in 20-64% yield, 72.5:27.5 to 95:5 er and 81:19 to >95:5 dr. Additionally, application of a ring-opening protocol yielded 1,2,3,4-substituted cyclopentanes in 28-77% yield, 76:24 to 98:2 er and 86:14 to >95:5 dr. Interestingly, the highest er was observed at high reaction temperatures, with 70°C proving optimal. This effect was investigated by conducting an Eyring analysis, which indicated that differential activation entropy rather than differential activation enthalpy is responsible for enantiodiscrimination in this process.
- Robinson, Emily R. T.,Frost, Aileen B.,Elías-Rodríguez, Pilar,Smith, Andrew D.
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p. 409 - 423
(2016/12/24)
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- Regio- and diastereoselective copper(I)-catalyzed allylic substitution of δ-hydroxy allylic chlorides by a silicon nucleophile
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A perfectly γ-selective copper(I)-catalyzed allylic substitution of protected δ-hydroxy allylic chlorides with a silicon nucleophile generated by Si-B bond activation provides diastereoselective access to β-hydroxy α-chiral allylic silanes with an anti re
- Hazra, Chinmoy K.,Irran, Elisabeth,Oestreich, Martin
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supporting information
p. 4903 - 4908
(2013/08/23)
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- Synthesis of cyclic N-tosyliminocarbonates by Lewis acid catalyzed allylic substitution of trichloroacetimidates
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Allylic trichloroacetimidates bearing a δ-N-tosylcarbamoyloxy group were prepared in two steps from the corresponding diols, and their Bronsted and Lewis acid catalyzed cyclization reactions were investigated. It was found that N-tosylcarbamates derived from secondary and tertiary alcohols bearing alkyl substituents undergo a chemoselective allylic alkylation to give N-tosyliminocarbonates in good isolated yields. In turn, aryl-substituted substrates tend to give oxazolines by abstraction of the carbamate functionality. The cyclization of N-tosylcarbamates derived from secondary alcohols preferentially give trans-iminocarbonates. However, the trans selectivity varied and depended on the substitution pattern, configuration of the substrate, and the catalyst. A high trans selectivity could be achieved from (E) substrates by using TMSOTf as the catalyst. The synthetic utility of iminocarbonates was demonstrated by transforming them into 1,2-diols and cyclic carbonates as well as into N-tosyloxazolidinones by a halide ion-induced rearrangement. Copyright
- Grigorjeva, Liene,Jirgensons, Aigars
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p. 5307 - 5316
(2012/10/30)
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- Gold-catalyzed [3+2] cycloaddition/hydrolytic Michael addition/retro-aldol reactions of propargylic esters tethered to cyclohexadienones
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A golden dance! A series of symmetric and nonsymmetric propargylic esters tethered to cyclohexadienones were found to undergo the title reaction sequence under mild reaction conditions through gold catalysis. The product cyclohexenones or cyclohexanones having a γ-quaternary center arise from simultaneous multiatom transpositions with complete stereochemical control. Copyright
- Cai, Shunyou,Liu, Zheng,Zhang, Weibin,Zhao, Xinyang,Wang, David Zhigang
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p. 11133 - 11137
(2012/02/02)
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- Lewis acid catalyzed intramolecular allylic substitution of bis(trichloroacetimidates): A versatile approach to racemic unsaturated amino acids
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Lewis acid catalyzed cyclization of trichloroacetimidates derived from 1,4-butenediols and 1,5-butenediols was achieved to give 4-vinyl oxazolines and 4-vinyloxazines in good to excellent yields. The cyclization products were transformed to protected unsaturated α- and β-amino acids, thus demonstrating the novel approach to access these important classes of compounds. Lewis acid catalyzed cyclization of allylic bis(trichloroacetimidates) (n = 1, 2) provides 4-vinyloxazolines and 4-vinyloxazines. The products of cyclization weredemonstrated to be versatile intermediates for the synthesis of unsaturated α- and β-amino acids. Copyright
- Grigorjeva, Liene,Jirgensons, Aigars
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p. 2421 - 2425
(2011/06/10)
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- Regiocontrol in Pd-catalyzed allylic substitution with P,N-ligand
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A racemic ligand, (±)-N-[2-(diphenylphosphino)naphthyl]-2- (pyrrolidinylmethyl)piperidine, has been found to exhibit better regioselectivity than the racemic Pfaltz ligand, BINAP and dppp in the palladium-catalyzed regioselective allylic substitution with
- Kondo, Kazuhiro,Kazuta, Kumiko,Saitoh, Atsushi,Murakami, Yasuoki
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- Epoxidation and cyclopropanation of 2-silyl-3-alkenols. A study of 1,2-asymmetric induction
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Epoxidation and cyclopropanation of 2-silyl-3-alkenols have been shown to occur with high 1,2-stereocontrol through substrate directable reactions. Both syn and anti epoxides are thus available from E and Z-allylsilanes. This contrasts with the results usually observed for allylsilanes lacking a coordinating group.
- Landais, Yannick,Parra-Rapado, Liliana
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p. 1205 - 1208
(2007/10/03)
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- ASSESSMENT OF BUTENE-1,4-DIOLS AS STARTING MATERIALS FOR THE PREPARATION OF ?-ALLYLTRICARBONYLIRON COMPLEXES
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This work assesses the use of butene-1,4-diols as starting materials for the synthesis of ?-allyltricarbonyliron lactone complexes.It has been shown that substituents, and the use of Lewis acids, mainly ZnBr2, in reactions with Fe2(CO)9 in benzene under ultrasonic conditions or in THF, greatly influence the yield and the product distribution.
- Bates, Roderick W.,Diez-Martin, David,Kerr, William J.,Knight, Julian G.,Ley, Steven V.,Sakellaridis, Anna
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p. 4063 - 4082
(2007/10/02)
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