- Enantioconvergent alkylation of ketones with racemic secondary alcohols: Via hydrogen borrowing catalysis
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An enantioconvergent method for the alkylation of o-disubstituted aryl ketones with racemic secondary alcohols is described. This process is mediated by a commercially available iridium catalyst and proceeds via hydrogen borrowing catalysis. The highly enantioenriched β-substituted ketone products were readily cleaved to a wide range of functional groups via retro-Friedel-Crafts acylation.
- Cheang, Daniella M. J.,Armstrong, Roly J.,Akhtar, Wasim M.,Donohoe, Timothy J.
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supporting information
p. 3543 - 3546
(2020/04/03)
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- Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes
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A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 8511 - 8514
(2015/11/27)
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- Enabling catalytic ketone hydrogenation by frustrated lewis pairs
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Hydrogenation of alkyl and aryl ketones using H2 is catalytically achieved in 18 examples using 5 mol % B(C6F5)3 in an ethereal solvent. In these cases the borane and ether behave as a frustrated Lewis pair to activate H2 and effect the reduction.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 15809 - 15812
(2015/02/19)
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- Efficient transfer hydrogenation reaction Catalyzed by a dearomatized PN3P ruthenium pincer complex under base-free Conditions
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A dearomatized complex [RuH(PN3P)(CO)] (PN3PN, N′-bis(di-tert-butylphosphino)-2,6-diaminopyridine) (3) was prepared by reaction of the aromatic complex [RuH(Cl)(PN3P)(CO)] (2) with t-BuOK in THF. Further treatment of 3 with formic acid led to the formation of a rearomatized complex (4). These new complexes were fully characterized and the molecular structure of complex 4 was further confirmed by X-ray crystallography. In complex 4, a distorted square-pyramidal geometry around the ruthenium center was observed, with the CO ligand trans to the pyridinic nitrogen atom and the hydride located in the apical position. The dearomatized complex 3 displays efficient catalytic activity for hydrogen transfer of ketones in isopropanol.
- He, Li-Peng,Chen, Tao,Xue, Dong-Xu,Eddaoudi, Mohamed,Huang, Kuo-Wei
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experimental part
p. 202 - 206
(2012/03/26)
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- Screening method for the evaluation of asymmetric catalysts for the reduction of aliphatic ketones
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ATH reductions of aliphatic ketones in water catalyzed by ruthenium coordinated by prolinamide ligands produce alcohols with moderate enantiomeric excesses in most cases. A set of seven aliphatic ketones is proposed for a rapid evaluation of the enantioselectivity of catalysts by one-pot multi-substrates reduction. The screening of a library of prolinamides shows that according to the structure of the ketones different ligands give the best asymmetric inductions.
- Boukachabia, Mourad,Zeror, Saoussen,Collin, Jacqueline,Fiaud, Jean-Claude,Zouioueche, Louisa Aribi
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supporting information; experimental part
p. 1485 - 1489
(2011/05/16)
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- IMPROVED METHOD FOR THE PREPARATION OF ENANTIOMERICALLY ENRICHED SECONDARY ALCOHOLS BY THE ADDITION OF ORGANOALUMINIUM REAGENTS TO CARBONYL COMPOUNDS
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A process for converting a carbonyl group within a substrate to a chiral alcohol moiety comprising reacting the carbonyl containing substrate with an organoaluminium reagent in the presence of a Group 5-12 transition metal based catalyst which is complexed with a chiral ligand; novel chiral ligands and organoluminium reagents, a chiral ligand or organoaluminium reagent for use in the process.
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Page/Page column 37-38
(2008/06/13)
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- Hydroboartion. 62. Monoisopinocampheylborane, an Excellent Chiral Hydroborating Agent for Trans-Disubstituted and Trisubstituted Alkenes. Evidenece for a Strong Steric Dependence in Such Asymmetric Hydroborations
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Monoisopinocampheylborane (IpcBH2), the first monoalkylborane chiral hydroborating agent, is capable of reacting with olefins of varying stuctural and steric requiments to produce, in most cases, clean dialkylboranes.IpcBH2 achieves the asymmetric hydroboration of trans-disubstituted and trisubstituted olefins with exceptionally high asymmetric induction.The product alcohols, produced by oxidation of the intermediate organoboranes, exhibit enantiomeric purities in the range of 53-100percent ee and reveal the same absolute configuration.Enantiomeric purities of the products increase with increasing steric requirements of the alkyl or phenyl substituent in the trans-disubstituted or trisubstituted alkene.
- Brown, Herbert C.,Jadhav, Prabhakar K.,Mandal, Arun K.
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p. 5074 - 5083
(2007/10/02)
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- Studies on the Autoxidation of Branched-chain Olefins. I. Autoxidation of 2-Methylalk-1-enes and 2-Methylalk-2-enes
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The products of the autoxidation of 2-methylpent-1-ene, 2-methylpent-2-ene, 2-methylhex-1-ene, 2-methylhex-2-ene, 2,4,4-trimethylpent-1-ene, and 2,4,4-trimethylpent-2-ene were analyzed by gas chromatography.The identification of the products corresponding to the individual peaks was possible by comparison with authentic substances or by preparative gaschromatographic separation and n.m.r.-spectroscopy of the isolated samples.In this way not only the epoxides and the products of the oxidative cleavage of the C=C double bond but also the allylic alcohols formed by LiAlH4-reduction of the oxidation mixtures could be identified and analyzed.From the results the compositions of the original oxidation mixtures were calculated.
- Bilas, W.,Hoebold, W.,Pritzkow, W.
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p. 125 - 141
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 14. Alkyl Shifts from Secondary to Primary Carbon Atoms
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Alkyl shifts from secondary to primary carbon atoms have been induced by the nitrous acid deamination of suitable amines (4, 22, 39, 51); they include sequential rearrangements (-CH3,CH3 and -CH3,H).Predominant although incomplete inversion at the migration origin has been observed (Me 70percent, Et 62-64percent, nPr 65percent, iPr 64percent, tBu 55percent).Our results require the intervention of open secondary carbocations which may be preceded by less stable bridged intermediates.
- Kirmse, Wolfgang,Guenther, Bernd-Rainer,Knist, Johannes,Kratz, Sigrid,Loosen, Karin,et al.
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p. 2127 - 2139
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 12. Alkyl Shifts between Secondary Carbon Atoms
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Several optically active, β-branched alkylamines have been synthesized from amino acids.The corresponding amines were obtained from isobutyraldehyde and 2-methylbutanal (37), respectively.The stereochemistry at the terminus of 1,2-methyl shifts has been elucidated in the nitrous acid deaminations of 4 and 21.Predominant, although incomplete inversion at the migration terminus is consistent with conformational control rather than neighboring group participation.The deamination of 31 involves a degenerate 1,2-ethyl shift and a nondegenerate 1,2-methyl shift, the reverse holds for 44.Complete inversion at the origin of the methyl migrations and the absence of subsequent retrogressive H shifts strongly support the intermediacy of methyl-bridged carbocations.Partial racemization at the origin of the ethyl migrations has been traced to proton shifts within ethyl-bridged intermediates.Rearranged open cations contribute significantly to the overall reaction if micelles are produced by self-aggregation of the alkylammonium ions.
- Kirmse, Wolfgang,Prolingheuer, Ernst-Christoph
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p. 104 - 128
(2007/10/02)
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