- Generating cis-aza-diaryl and triaryl ethers via organoBr?nsted acid catalysed aza-Darzens chemistry
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We report the efficient combination of SNAr and organic Br?nsted acid catalysis protocols for the construction of cis-aziridine-derived biaryl and triaryl ethers. Using aza-Darzens chemistry mono-cis-aziridine-biaryl and bis-(cis-aziridine)-triaryl ethers have been generated; these motifs have significant potential as easily synthesised, functionalised precursors of a glycopeptide backbone.
- Bew, Sean P.,Coles, Simon J.,Pitak, Mateusz B.,Klooster, Wim T.,Ashford, Polly-Anna,Zdorichenko, Victor
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- Diastereoselective synthesis of (2R,4S,5S)-(+)-5-(2,2-Dichloroacetamido)- 4-(4-nitrophenyl)-2-aryl-1,3-dioxanes
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(2R,4S,5S)-(+)-5-(2,2-Dichloroacetamido)-4-(4-nitrophenyl) -2-aryl-1,3-dioxanes 3-8 were synthesized with high diastereoselectivity and good yields. The structures of acetals were determined and the configurations were confirmed by 2D-NMR (NOESY) and X-ray crystallographic analysis.
- Jun,Jun,Shaorong,Hua,Quanyuan,Hansheng,Xianming
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- Chiral Br?nsted Acid-Catalyzed Asymmetric Synthesis of N-Aryl-cis-aziridine Carboxylate Esters
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We report a multi-component asymmetric Br?nsted acid-catalyzed aza-Darzens reaction which is not limited to specific aromatic or heterocyclic aldehydes. Incorporating alkyl diazoacetates and, important for high ee's, ortho-tert-butoxyaniline our optimized reaction (i.e. solvent, temperature and catalyst study) affords excellent yields (61–98 %) and mostly >90 % optically active cis-aziridines. (+)-Chloramphenicol was generated in 4 steps from commercial starting materials. A tentative mechanism is outlined.
- Bew, Sean P.,Liddle, John,Hughes, David L.,Pesce, Paolo,Thurston, Sean M.
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p. 5322 - 5326
(2017/04/27)
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- Synthesis of Some Selectively N-Protected (1S,2S)-p-Nitrophenylserinol-Based Diamino-1,3-dioxanes and Tripodands
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The unconventional methodology for the non-epimerizable cycloacetalization of optically active (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diol (p-nitrophenylserinol) (condensed H2SO4 96% as solvent and catalyst, i.e., sulfuric transacetalization) producing (2R,4S,5S) diamino-1,3-dioxanes was enlarged by the use of N-protected forms of 2,2-dimethoxyethylamine (DMEA, aminoacetaldehyde dimethylacetal). Conversely, N-protected derivatives of p-nitrophenylserinol were successfully cyclocondensed with DMEA in the same sulfuric conditions. N-Functionalization of DMEA upon treatment with trimesic acid trichloride and cyanuric chloride yielded the corresponding triple amide and melamine, respectively. Their adapted sulfuric transacetalization in triplicate in reaction with arylserinols (aryl: phenyl, p-nitrophenyl) afforded a new series of optically active tripodands.
- Nagy, Iulia,Moldovan, Oana,Popa, Flavia,Lameiras, Pedro,Morar, Cristina,Sacalis, Carmen,Darabantu, Mircea
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p. 2319 - 2330
(2015/10/12)
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- Oxidant controlled regio- and stereodivergent azidohydroxylation of alkenes via I2 catalysis
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A novel, I2 catalyzed regio- and stereodivergent vicinal azidohydroxylation of alkenes leading to 1,2-azidoalcohols in high yields (up to 92%) and excellent dr (up to 98%) has been developed. This unprecedented transformation employs NaN3 and DMF as N- and O-nucleophiles respectively. The role of DMF as the O-source in the reaction has been unequivocally proven by 18O labelling studies.
- Prasad,Reddi,Sudalai
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p. 10276 - 10279
(2015/06/25)
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- Enantioselective synthesis of (-)-chloramphenicol via silver-catalysed asymmetric isocyanoacetate aldol reaction
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The highly enantio- and diastereoselective aldol reaction of isocyanoacetates catalysed by Ag2O and cinchona-derived amino phosphines applied to the synthesis of (-)- and (+)-chloramphenicol is described. The concise synthesis showcases the utility of this catalytic asymmetric methodology for the preparation of bioactive compounds possessing α-amino-β-hydroxy motifs.
- Franchino, Allegra,Jakubec, Pavol,Dixon, Darren J.
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- Direct synthesis of β-hydroxy-α-amino acids via diastereoselective decarboxylative aldol reaction
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A straightforward metal-free synthesis of anti-β-hydroxy-α-amino acids is described. The organic base-mediated decarboxylative aldol reaction of cheap, readily available α-amidohemimalonates with various aldehydes afforded under very mild conditions anti-β-hydroxy-α-amido esters in high yields and complete diastereoselectivity. Simple one-pot subsequent transformations enabled the corresponding anti-β-hydroxy-α-amino acids or in a few examples their syn diastereomers to be obtained directly using epimerization conditions.
- Singjunla, Yuttapong,Baudoux, Jeroime,Rouden, Jacques
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p. 5770 - 5773
(2013/12/04)
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- Synthesis of dendrimer-type chiral stationary phases based on the selector of (1S,2R)-(+)-2-amino-1,2-diphenylethanol derivate and their enantioseparation evaluation by HPLC
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In our recent work, a series of dendritic chiral stationary phases (CSPs) were synthesized, in which the chiral selector was L-2-(p-toluenesulfonamido)-3- phenylpropionyl chloride (selector I), and the CSP derived from three-generation dendrimer showed the best separation ability. To further investigate the influence of the structures of dendrimer and chiral selector on enantioseparation ability, in this work, another series CSPs (CSPs 1-4) were prepared by immobilizing (1S,2R)-1,2-diphenyl-2-(3-phenylureido)ethyl 4-isocyanatophenylcarbamate (selector II) on one- to four-generation dendrimers that were prepared in previous work. CSPs 1 and 4 demonstrated the equivalent enantioseparation ability. CSPs 2 and 3 showed the best and poorest enantioseparation ability respectively. Basically, these two series of CSPs exhibited the equivalent enantioseparation ability although the chiral selectors were different. Considering the enantioseparation ability of the CSP derived from aminated silica gel and selector II is much better than that of the one derived from aminated silica gel and selector I, it is believed that the dendrimer conformation essentially impacts enantioseparation.
- He, Bao-Jiang,Yin, Chuan-Qi,Li, Shi-Rong,Bai, Zheng-Wu
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experimental part
p. 69 - 76
(2010/09/09)
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- Organocatalytic aziridine synthesis using F+ salts
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This paper describes a unique application of the fluoronium cation (F +) as an organocatalyst for mediating the reaction between N-substituted imines and ethyl diazoacetate affording excellent yields of N-substituted aziridines.
- Bew, Sean P.,Fairhurst, Shirley A.,Hughes, David L.,Legentil, Laurent,Liddle, John,Pesce, Paolo,Nigudkar, Sanket,Wilson, Martin A.
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supporting information; experimental part
p. 4552 - 4555
(2009/12/05)
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- Synthesis of chloramphenicol via a new intermediate 4-para-nitrophenyl- 5-formamido-1,3-dioxane
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4-Phenyl-5-amino-1,3-dioxane 4, obtained from β-bromo styrene 2 was protected as formamido derivative 5. Nitration of 5 followed by regioselective acylative cleavage of the nitro product 12 gave N-formyl-N- acetyl hemiacetal diacetate 16, which on sequential base and acid hydrolysis followed by dichloroacetylation gave chloramphenicol 1.
- Hazra, Braja G.,Pore, Vandana S.,Maybhate, Shailaja P.
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p. 1857 - 1864
(2007/10/03)
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- REGIOSELECTIVE ACYLATIVE CLEAVAGE OF CYCLIC FORMAL OF CHLORAMPHENICOL
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The amide 6 has been synthesised by reacting the amine 3 with dichloroketene in situ.This amide 6 on nitration gave formal 7, which when reacted with acetic anhydride and p-toluene sulfonic acid underwent regioselective cleavage of the dioxane ring to furnish the hemiacetal 11.This on treatment with methanol-water-ammonia yielded chloramphenicol 2.
- Hazra, B. G.,Pore, V. S.,Maybhate, S. P.,Natekar, M. V.,Rao, A. S.
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p. 1763 - 1770
(2007/10/02)
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