- Cross β-alkylation of primary alcohols catalysed by DMF-stabilized iridium nanoparticles
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A simple method for the cross β-alkylation of linear alcohols with benzyl alcohols in the presence of DMF-stabilized iridium nanoparticles was developed. The nanoparticles were prepared in one-step and thoroughly characterized. Furthermore, the optimum reaction conditions have a wide substrate scope and excellent product selectivity.
- Kobayashi, Masaki,Yamaguchi, Hiroki,Suzuki, Takeyuki,Obora, Yasushi
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supporting information
p. 1950 - 1954
(2021/03/16)
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- Cross β-arylmethylation of alcohols catalysed by recyclable Ti-Pd alloys not requiring pre-activation
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Ti-Pd alloy catalysts were developed for the cross β-arylmethylation between arylmethylalcohols and different primary alcohols via a hydrogen autotransfer mechanism. The alloy catalysts could be reused multiple times without the need for pre-activation. Analysis of the reaction solution by inductively coupled plasma atomic absorption spectroscopy indicated that only a minimal amount of Ti and no Pd was leached from the catalyst.
- Utsunomiya, Masayoshi,Kondo, Ryota,Oshima, Toshinori,Safumi, Masatoshi,Suzuki, Takeyuki,Obora, Yasushi
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supporting information
p. 5139 - 5142
(2021/05/31)
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- Hydrogen borrowing catalysis using 1° and 2° alcohols: Investigation and scope leading to α and β branched products
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The alkylation of a variety of ketones using 1° or 2° alcohols under hydrogen borrowing catalysis is described. Initial research focused on the α-alkylation of cyclopropyl ketones with higher 1° alcohols (i.e. larger than MeOH), leading to the formation of α-branched products. Our search for additional substrates with which to explore this chemistry led us to discover that di-ortho-substituted aryl ketones were also privileged scaffolds, with Ph? (C6Me5) ketones being the optimal choice. Further investigations revealed that this motif was crucial for alkylation with 2° alcohols forming β-branched products, which also provided an opportunity to study diastereoselective and intramolecular hydrogen borrowing processes.
- Frost, James R.,Cheong, Choon Boon,Akhtar, Wasim M.,Caputo, Dimitri F.J.,Christensen, Kirsten E.,Stevenson, Neil G.,Donohoe, Timothy J.
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- Synthesis and olfactory evaluation of optically active β-alkyl substituted γ-lactones and whiskey lactone analogues
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Optically active β-alkyl substituted γ-lactones and whiskey lactone analogues were synthesized, and the odor properties were evaluated. During the preparation of the chiral intermediates, we found good reaction conditions for the highly enantioselective esterification of 3-arylmethyl-2-methyl-1-propanols to kinetically resolve them. The results of the olfactory evaluations of the synthesized lactones revealed that the alkyl groups on the γ-lactone rings played an important role for the odor profiles.
- Kato, Daiki,Kawasaki, Masashi,Morita, Yuko,Okada, Takuya,Tanaka, Yasuo,Toyooka, Naoki
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- Enantioselective Formal α-Methylation and α-Benzylation of Aldehydes by Means of Photo-organocatalysis
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Detailed herein is the photochemical organocatalytic enantioselective α-alkylation of aldehydes with (phenylsulfonyl)alkyl iodides. The chemistry relies on the direct photoexcitation of enamines to trigger the formation of reactive carbon-centered radicals from iodosulfones, while the ground-state chiral enamines provide effective stereochemical control over the radical trapping process. The phenylsulfonyl moiety, acting as a redox auxiliary group, facilitates the generation of radicals. In addition, it can eventually be removed under mild reducing conditions to reveal methyl and benzyl groups.
- Filippini, Giacomo,Silvi, Mattia,Melchiorre, Paolo
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supporting information
p. 4447 - 4451
(2017/04/13)
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- Strategic Application and Transformation of ortho-Disubstituted Phenyl and Cyclopropyl Ketones to Expand the Scope of Hydrogen Borrowing Catalysis
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The application of an iridium-catalyzed hydrogen borrowing process to enable the formation of α-branched ketones with higher alcohols is described. In order to facilitate this reaction, ortho-disubstituted phenyl and cyclopropyl ketones were recognized as crucial structural motifs for C-C bond formation. Having optimized the key catalysis step, the ortho-disubstituted phenyl products could be further manipulated by a retro-Friedel-Crafts acylation reaction to produce synthetically useful carboxylic acid derivatives. In contrast, the cyclopropyl ketones underwent homoconjugate addition with several nucleophiles to provide further functionalized branched ketone products.
- Frost, James R.,Cheong, Choon Boon,Akhtar, Wasim M.,Caputo, Dimitri F. J.,Stevenson, Neil G.,Donohoe, Timothy J.
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p. 15664 - 15667
(2016/01/09)
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- Pseudoephenamine: A practical chiral auxiliary for asymmetric synthesis
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Unrestricted: Pseudoephenamine is introduced as a versatile chiral auxiliary and an alternative to pseudoephedrine in asymmetric synthesis. It is free from regulatory restrictions and leads to remarkable stereocontrol in alkylation reactions, especially in those that form quaternary carbon centers. Amides derived from pseudoephenamine exhibit a high propensity to be crystalline substances, and provide sharp, well-defined signals in NMR spectra. Copyright
- Morales, Marvin R.,Mellem, Kevin T.,Myers, Andrew G.
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supporting information; experimental part
p. 4568 - 4571
(2012/06/30)
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- Discrete iron complexes for the selective catalytic reduction of aromatic, aliphatic, and α,β-unsaturated aldehydes under water-gas shift conditions
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Iron-catalyzed reductions: Selective iron-catalyzed reduction of aldehydes with hydrogen generated in situ by the water-gas shift reaction is presented (see scheme). The generality and selectivity of this mild procedure are demonstrated by the efficient reduction of various aromatic, aliphatic and α,β-unsaturated aldehydes.
- Tlili, Anis,Schranck, Johannes,Neumann, Helfried,Beller, Matthias
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p. 15935 - 15939
(2013/02/21)
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- Evaluation of (+)-sparteine-like diamines for asymmetric synthesis
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Three new (+)-sparteine-like diamines were prepared from (-)-cytisine and evaluated as sparteine surrogates in the α-lithiation rearrangement of cyclooctene oxide and the palladium(II)/diamine catalyzed oxidative kinetic resolution of 1-indanol. The new diamines exhibited opposite enantioselectivity to that observed with (-)-sparteine but increasing the steric hindrance of the N-alkyl group beyond N-Et had a detrimental effect on enantioselectivity. The optimal N-Me diamine was evaluated with much success in five other (-)-sparteine-mediated processes involving different metals (lithium, magnesium, and copper) and different types of reaction mechanisms.
- Dearden, Michael J.,McGrath, Matthew J.,O'Brien, Peter
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p. 5789 - 5792
(2007/10/03)
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- Application of A Recyclable Pseudoephedrine Resin in Asymmetric Alkylations on Solid Phase
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A pseudoephedrine resin has been successfully employed in asymmetric alkylations on solid phase. Immobilized pseudoephedrine amides are conveniently prepared by the one-step attachment of pseudoephedrine to Merrifield resin through the hydroxyl group and subsequent acylation on nitrogen. Deprotonation and alkylation of the resin-bound amides proceeds smoothly. Ketones and alcohols are cleaved from the resin in high enantiomeric excess and moderate to good overall yield. The parallel, asymmetric solid-phase synthesis of a small library of chiral ketones and alcohols has been carried out to illustrate the utility of the approach. Finally, the pseudoephedrine resin can be conveniently recycled and utilized with no significant loss in the yield or enantiomeric excess of the products.
- Hutchison, Panee C.,Heightman, Tom D.,Procter, David J.
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p. 790 - 801
(2007/10/03)
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- Diastereoselective electrophilic substitution of γ-oxy-substituted benzyllithiums
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Reductive lithiation of diastereoisomeric mixtures of 4-aryl-5-methyl-1,3-dioxanes occurs with epimerization at the benzylic centre. Reaction of intermediate organometals with alkyl halides or CO2 afforded 2-methyl-3-substituted-3-phenylpropan-1-ols, or the corresponding lactones, with satisfactory yields and satisfactory to high diastereoselectivities. Observed diastereoselectivities strongly depend on the substitution pattern of starting materials.
- Arrica, Maria A,Azzena, Ugo,Pilo, Luciano,Piras, Elisabetta
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p. 5137 - 5139
(2007/10/03)
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- An easy access to enantio-enriched α-substituted aldehydes by carbolithiation of β-phenyl or β-silyl-α,β-ethylenic aldehydes, protected with the monolithioamide of a chiral diamine
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Lithium amide derived from N,N,N′-trimethyl-1,2-diphenylethanediamine converts cinnamaldehyde to a lithium alkoxyamide which undergoes a regio- and stereoselective carbolithiation upon addition of various organolithiums. Subsequent hydrolysis or trapping with MeI delivers α-mono-, or α,β-disubstituted 3-phenylpropanals with e.e.s of 76-96%. Extension to a silylated α-enal is possible.
- Brémand, Nathalie,Mangeney, Pierre,Normant, Jean F.
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p. 1883 - 1885
(2007/10/03)
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- Allyl alcohols and organocerium reagents, II. - Mechanism and extensibility of the reaction
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Alkylcerium reagents add to the multiple bonds of allyl and propargyl alcohols in good yields and under mild conditions. The double bond can be reduced with lithium aluminum hydride in the presence of cerium trichloride. The regiochemistry of the attack depends on electronic factors.
- Bartoli, Giuseppe,Bellucci, M. Cristina,Bosco, Marcella,Dalpozzo, Renato,De Nino, Antonio,Sambri, Letizia,Tagarelli, Antonio
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- Regioselective addition of nbutyllithium on secondary cinnamyl amides: 'Michael' versus 'contra-Michael' process
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Lithiated secondary cinnamyl amides undergo a preferred 'contra-Michael' addition of nbutyllithium, complexed with (-)sparteine, in a non polar solvent.
- Bremand, Nathalie,Marek, Ilan,Normant, Jean F.
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p. 3379 - 3382
(2007/10/03)
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- Enantioselective carbometalation of cinnamyl derivatives: New access to chiral disubstituted cyclopropanes - Configurational stability of benzylic organozinc halides
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A stoichiometric or catalytic amount of (-)-sparteine can serve asa promoter for the enantioselective carbolithiation of cinnamyl derivatives by primary and secondary organolithium compounds. The enantiofacial choice of the addition reaction is dependent on the stereochemistry of the initial double bond. The resulting benzylic organolithium compounds can be derivatized to a linear phenylated chain that bears two contiguous stereogenic centers with given configurations. The use of the dimethyl acetal of the (E)-cinnamyl alcohol allows the highest enantioselective carbolithiation and by simply warming the reaction mixture to room temperature, the resulting benzylic organo-lithium intermediate undergoes a 1,3-elimination to give the chiral disubstituted cyclopropane in high enantiomeric excess (90-95% ee). Another significant finding is the observation that the Li-Zn transmetalation in a benzylic species occurs with inversion of configuration, and the corresponding acyclic benzylic zinc halides have observable configurational stability at - 30°C.
- Norsikian, Stephanie,Marek, Ilan,Klein, Sophie,Poisson, Jean F.,Normant, Jean F.
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p. 2055 - 2068
(2007/10/03)
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- Pseudoephedrine as a practical chiral auxiliary for the synthesis of highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones
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The use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis is described in full. Both enantiomers of pseudoephedrine are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides. In the presence of lithium chloride, the enolates of the corresponding pseudoephedrine amides undergo highly diastereoselective alkylations with a wide range of alkyl halides to afford α-substituted products in high yields. These products can then be transformed in a single operation into highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones.
- Myers, Andrew G.,Yang, Bryant H.,Chen, Hou,McKinstry, Lydia,Kopecky, David J.,Gleason, James L.
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p. 6496 - 6511
(2007/10/03)
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- Lithium amidotrihydroborate, a powerful new reductant. Transformation of tertiary amides to primary alcohols
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Lithium amidotrihydroborate (LiH2NBH3, LAB) is a new and highly nucleophilic reducing agent that is easily prepared by deprotonation of the commercial reagent borane-ammonia complex (H2NBH3) with n-BuLi in tetrahydrofuran (THF) at 0°C. LAB is found to be a superior reagent for the transformation of tertiary amides into the corresponding primary alcohols.
- Myers, Andrew G.,Yang, Bryant H.,Kopecky, David J.
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p. 3623 - 3626
(2007/10/03)
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- Enantioselective aldol chemistry via alkyl enol ethers. Scope of the Lewis acid catalyzed condensation of optically active trimethylsilyl and methyl 2-[(E)-1-alkenyloxy]ethanoates with acetals
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Optically active, mono- and disubstituted trimethylsilyl 2-[(E)-1-alkenyloxy]ethanoates of the type RR1CH = CHOCHR2CO2SiMe3 (R = Me, PhCH2, n-Bu, MeO2CCMe2CH2, PhSCHs
- Faunce, James A.,Grisso, Bryan A.,Mackenzie, Peter B.
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p. 3418 - 3426
(2007/10/02)
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- THE ATE COMPLEXES OF ALUMINIUM. REACTIVITY AND STEREOSELECTIVITY WITH RESPECT TO EPOXIDES AND CARBONYL COMPOUNDS. CATALYTIC ACTIVATION BY SALTS OF TRANSITION METALS
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When used in non-coordinating solvents (hydrocarbons) NaAlEt4 and LiAlnBu4 are good alkylation agents for epoxides.The presence of catalytic quantities of transition-metal salts, particularly NiCl2 or NiBr2, greatly accelerate the reactions, making them possible within a reasonable time in the case of disubstituted epoxides such as cyclohexene oxide, 2-3 epoxybutane, 1 phenyl-2,3-epoxybutane.In the case of aliphatic epoxides, dialkylmagnesium, NaAlEt4 and LiAlnBu4 lead mainly to alkylation of the least substituted carbon of the epoxide ring; while in the case of epoxides with C-O bond in the benzyl position, it is this carbon that is alkylated.The reaction always proceeds by total inversion of the configuration of the carbon in the epoxide ring, namely the site of the alkylation. NaAlEt4 is also good agent for alkylating carbonyl compounds when used in solvents of low basicity such as diethylether, or in totally non-coordinating solvents such as the hydrocarbons.The yields of the alcohol are greatly improved by using catalytic quantities of NiCl2.The behaviour of NaAlEt4 with 2-phenylpropanol is quite remarkable: in diethylether NaAl-Et4 gives predominantly the pair of enantiomers predicted by Cram's rule and with greater stereoselectivity than if EtMgBr was used, while in pentane the reaction is no longer stereoselective.Finally, with a cyclic ketone, 4-t-butylcyclohexanone, NaAlEt4 in diethylether and in hexane in the presence of NiCl2 gives predominantly the equatorial alcohol resulting from an axial attack, which is generally not favoured at all.
- Boireau, G.,Abenhaim, D.,Henry-Basch, E.
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p. 3061 - 3070
(2007/10/02)
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