- Stereospecific Alkene Aziridination Using a Bifunctional Amino-Reagent: An Aza-Prilezhaev Reaction
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In situ deprotection (TFA) of O-Ts activated N-Boc hydroxylamines triggers intramolecular aziridination of N-tethered alkenes to provide complex N-heterocyclic ring systems. Synthetic and computational studies corroborate a diastereospecific aza-Prilezhaev-type mechanism. The feasibility of related intermolecular alkene aziridinations is also demonstrated.
- Farndon, Joshua J.,Young, Tom A.,Bower, John F.
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supporting information
p. 17846 - 17850
(2019/01/04)
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- Solvent- and temperature-dependent functionalisation of enantioenriched aziridines
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A highly stereo- and regioselective functionalisation of chiral non-racemic aziridines is reported. By starting from a parent enantioenriched aziridine and finely tuning the reaction conditions, it is possible to address the regio- and stereoselectivity of the lithiation/electrophile trapping sequence, thereby allowing the preparation of highly enantioenriched functionalised aziridines. From chiral N-alkyl trans-2,3-diphenylaziridines (S,S)-1 a,b, two differently configured chiral aziridinyllithiums could be generated (trans-1 a,b-Li in toluene and cis-1 a,b-Li in THF), thus disclosing a solvent-dependent reactivity that is useful for the synthesis of chiral tri-substituted aziridines with different stereochemistry. In contrast, chiral aziridine (S,S)-1 c showed a temperature-dependent reactivity to give chiral ortho-lithiated aziridine 1 c-ortho-Li at -78 °C and α-lithiated aziridine 1 c-α-Li at 0 °C. Both lithiated intermediates react with electrophiles to give enantioenriched ortho- and α-functionalised aziridines. The reaction of all the lithiated aziridines with carbonyl compounds furnished useful chiral hydroxyalkylated derivatives, the stereochemistry of which was ascertained by X-ray and NMR spectroscopic analysis. The usefulness of chiral non-racemic functionalised aziridines has been demonstrated by reductive ring-opening reactions furnishing chiral amines that bear quaternary stereogenic centres and chiral 1,2-, 1,3- and 1,5-aminoalcohols. It is remarkable that the solvent-dependent reactivity observed with (S,S)-1 a,b permits the preparation of both the enantiomers of amines (11 and ent-11) and 1,2-aminoalcohols (13 and ent-13) starting from the same parent aziridine. Interestingly, for the first time, a configurationally stable chiral α-lithiated aziridine (1 c-α-Li) has been generated at 0 °C. In addition, ortho- hydroxyalkylated aziridines have been easily converted into chiral aminoalkyl phthalans, which are useful building blocks in medicinal chemistry.
- De Ceglie, Maria Carolina,Musio, Biagia,Affortunato, Francesco,Moliterni, Anna,Altomare, Angela,Florio, Saverio,Luisi, Renzo
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scheme or table
p. 286 - 296
(2011/02/27)
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- Experimental and theoretical investigations for the regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxazolidin-2-ones
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The regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxazolidin-2-ones takes place in good yield. However, the cis configuration at C2 and C3 in monocyclic aziridines is a limiting factor for this transformation
- Testa, Luisa,Akssira, Mohamed,Zaballos-García, Elena,Arroyo, Pau,Domingo, Luis R.,Sepúlveda-Arques, Jose
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p. 677 - 683
(2007/10/03)
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- Stereoselective synthesis of δ-lactones from 5-oxoalkanals via one-pot sequential acetalization, tishchenko reaction, and lactonization by cooperative catalysis of samarium ion and mercaptan
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By the synergistic catalysis of samarium ion and mercaptan, a series of 5-oxoalkanals was converted to (substituted) δ-lactones in efficient and stereoselective manners. This one-pot procedure comprises a sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis of optically active δ-lactones. This study also demonstrates the synthesis of two insect pheromones, (2S,5R)-2-methylhexanolide and (R)-hexadecanolide, as examples of a new protocol for asymmetric reduction of long-chain aliphatic ketones.
- Hsu,Fang
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p. 8573 - 8584
(2007/10/03)
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- Aminosulf(ox)ides as Ligands for Iridium(I)-Catalyzed Asymmetric Transfer Hydrogenation
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A new class of efficient catalysts was developed for the asymmetric transfer hydrogenation of unsymmetrical ketones. A series of chiral N,S-chelates (6-22) was synthesized to serve as ligands in the iridium(I)-catalyzed reduction of ketones. Both formic a
- Petra, Danielle G. I.,Kamer, Paul C. J.,Spek, Anthony L.,Schoemaker, Hans E.,Van Leeuwen, Piet W. N. M.
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p. 3010 - 3017
(2007/10/03)
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- ENANTIOMERICALLY PURE β-AMINO SULFIDES AND β-AMINO THIOLS FROM EPHEDRINE
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Ephedrine and pseudoephedrine are converted by means of a Mitsunobu reaction to respectively trans- and cis-aziridines, which can be ring-opened at the benzylic center with inversion of configuration by thiols and thiol acids.The trans-aziridine from ephe
- Poelert, Martin A.,Hof, Robert P.,Peper, Nathalie C. M. W.,Kellogg, Richard M.
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p. 461 - 476
(2007/10/02)
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- CHIRAL BICYCLIC SPIROPHOSPHORANES IN AN ARBUZOV-TYPE REACTION
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The reaction of 2-hydroxy-5-nitro-benzyl halides with three chiral five-or six-membered oxaphosphacycloalkanes has been studied.In each case, a 31P NMR analysis shows the formation of resonance signals in the phosphorane region but these phosphoranes are usually unstable.However both enantiomers of the 2-phenyl-1,3,2-oxazaphospholidine give chiral bicyclic spirophosphoranes which have been characterized by 31P and 1H NMR and high resolution mass spectroscopies.
- Acher, Francine,Juge, Sylvain,Wakselman, Michel
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p. 3721 - 3728
(2007/10/02)
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- The Preparation and Properties of some Chiral Fluoromethylphosphonates, Phosphonothioates, and Phosphonamidothioates
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Enantiomerically pure dialkyl di- and mono-fluoromethylphosphonates are prepared by fluorination of the unsubstituted phophonate anions.The corresponding fluoromethylphosphonothioates and thioic acids are prepared using (-)-ephedrine as a chiral template and the thioic acids are converted, via the chloridates, into the phosphoramidothioates.Treatment of O-ethyl S-methyl difluoromethylphosphonothioate with methoxide results in P-S bond cleavage with retention of configuration.In the corresponding monofluoromethylphosphonothioate and in S-methyl P-difluoromethyl-NN-dimethylphosphonamidothioate the reaction occurs with predominant inversion of configuration.Ethoxide-promoted endocyclic P-N bond cleavage in 2-difluoromethyl-1,3,2-oxazaphospholidine-2-thiones can occur with retention of configuration at phosphorus.
- Hall, C. Richard,Inch, Thomas D.,Williams, Nancy E.
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p. 233 - 237
(2007/10/02)
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- Reactions of Metal Complexes with Small Rings, XI. Ring Opening of Aziridines by Metal Carbonyl Hydrides; β-Aminoacyl Chelate Complexes of Manganese, Molybdenum, Tungsten and Cobalt
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The metal carbonyl hydrides HM(CO)3(?-C5H5) (M = Mo, W), HMn(CO4)L, HCo(CO)3L (L = CO, PPh3) react with aziridines by protonation of aziridine, nucleophilic attack of the corresponding carbonyl metallate and CO insertion to give the β-aminoacyl complexes
- Danzer, Wolfgang,Hoefer, Roland,Menzel, Hartmut,Olgemoeller, Bernhard,Beck, Wolfgang
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p. 167 - 179
(2007/10/02)
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- 1,3,2-Oxazaphospholidine-2-thiones from (+)-Norephedrine: Stereospecific Ring Opening, Possibly by an Elimination-Addition Mechanism
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1,3,2-Oxazaphospholidine-2-thiones derived from (+)-norephedrine react with alkoxide to give a product of kinetic control, formed by endocyclic P-O cleavage with inversion of configuration, and one of thermodynamic control, formed by endocyclic P-N cleavage also with inversion of configuration.It is suggested that the product of kinetic control is formed by an elimination-addition process involving a metaphosphorimidate intermediate, and that of thermodynamic control by a mechanism involving nucleophilic attack opposite endocyclic nitrogen.
- Hall, C.Richard,Inch, Thomas D.,Williams, Nancy E.
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p. 639 - 644
(2007/10/02)
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- 1,3,2-Thiazaphospholidin-2-ones Derived From Ephedrine. Preparation and Stereochemistry of Ring-opening Reactions
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1,3,2-thiazaphospholidin-2-ones are prepared by rearrangement of the corresponding 1,3,2-oxazaphospholidine-2-thiones.In both the phosphono- and phosphoro-series treatment with alkoxide results in P-N bond cleavage with inversion of configuration, while treatment with Grignard reagents results in P-S bond cleavage with retention of configuration.The products are consistent with a mechanism which involves initial nucleophilic attack opposite endocyclic nitrogen.
- Hall, C. Richard,Williams, Nancy E.
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p. 2746 - 2750
(2007/10/02)
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