- Controllable Intramolecular Unactivated C(sp3)-H Amination and Oxygenation of Carbamates
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Dual catalyst-controlled intramolecular unactivated C(sp3)-H amination and oxygenation of carbamates merging visible-light photocatalysis and earth-abundant transition metal catalysis have been reported. Useful amino alcohol and diol derivatives could be selectively obtained from readily available tertiary alcohol derivatives. The possible mechanisms have been proposed via a 1,5-HAT process followed by Lewis acid-controlled cyclization. The nickel and zinc catalysts inhibit the formation of oxygenation and amination products, respectively. An interesting phenomenon of chirality transfer is also observed.
- Guo, Qihang,Ren, Xiang,Lu, Zhan
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p. 880 - 884
(2019/05/16)
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- Structures and Reactivities of Sodiated Evans Enolates: Role of Solvation and Mixed Aggregation on the Stereochemistry and Mechanism of Alkylations
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Oxazolidinone-based sodiated enolates (Evans enolates) were generated using sodium diisopropylamide (NaDA) or sodium hexamethyldisilazide (NaHMDS) in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA), (R,R)-trans-N,N,N′,N′-tetramethylcyclohexanediamine [(R,R)-TMCDA], or (S,S)-TMCDA. 13C NMR spectroscopic analysis in conjunction with the method of continuous variations (MCV), x-ray crystallography, and density functional theory (DFT) computations revealed the enolates to be octahedral bis-diamine-chelated monomers. Rate and computational studies of an alkylation with allyl bromide implicate a bis-diamine-chelated-monomer-based transition structure. The sodiated Evans enolates form mixed dimers with NaHMDS, NaDA, or sodium 2,6-di-tert-butylphenolate, the reactivities of which are examined. Stereoselective quaternizations, aldol additions, and azaaldol additions are described.
- Zhang, Zirong,Collum, David B.
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supporting information
p. 388 - 401
(2019/01/04)
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- SmI2-promoted intra- and intermolecular C-C bond formation with chiral N-acyl oxazolidinones
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The suitability of chiral oxazolidinones in the SmI2-mediated C-C bond generation between the imide functionality of an N-acyl oxazolidinone unit and an olefinic radical acceptor, in both inter- and intramolecular reactions, was investigated. It was shown that the products from an Evans asymmetric alkylation can undergo direct carbon-carbon bond formation with an acrylamide providing chiral acyclic ketones in reasonable yields. These examples represent the first transformation of such N-acyl oxazolidinones where this chiral auxiliary is removed under the conditions for ketone formation. 5-exo-trig Cyclization studies were also undertaken with the same type of substrates, providing trans-2,5-disubstituted cyclopentanones in yields of approx. 50%. However, attempts to cyclize heteroatom-containing equivalents were less rewarding.
- Taaning, Rolf H.,Thim, Laura,Karaffa, Jacob,Campa?a, Araceli G.,Hansen, Anna-Mette,Skrydstrup, Troels
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experimental part
p. 11884 - 11895
(2009/04/07)
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- Synthesis of enantiomerically pure divinyl- and diallylcarbinols
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Acylated oxazolidinones and bornane sultams can be cleaved to divinyl- and diallylcarbinols by treatment with vinyl- or allylmetal compounds. For the preparation of divinylcarbinols, acylated bornane sultams are the starting materials of choice, while for the preparation of diallylcarbinols acylated oxazolidinones and bornane sultams work equally well.
- Schmidt, Bernd,Wildemann, Holger
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p. 1050 - 1060
(2007/10/03)
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- The application of 1H nuclear magnetic resonance spectroscopy for the determination of the absolute configuration of chiral carboxylic acids
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A modification of a model, described by Mosher allows a correlation to be made between the absolute configuration of a range of simple chiral carboxylic acids with the corresponding nmr chemical shifts of their esters derived from (S)-methyl mandelate.
- Tyrrell, Elizabeth,Tsang, Michael W. H.,Skinner, George A.,Fawcett, John
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p. 9841 - 9852
(2007/10/03)
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