- Substrate-directed stereoselectivity in vicinal diamine-catalyzed synthesis of warfarin
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A new mechanism involving a diimine intermediate is proposed for vicinal diamine-catalyzed synthesis of warfarin. Decreasing the NCCN dihedral angle by varying the diamine results in an increase in the enantioselectivity of warfarin synthesis.
- Kim, Hyunwoo,Yen, Cindy,Preston, Philippa,Chin, Jik
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Read Online
- Cobalt-Catalyzed Radical Hydroamination of Alkenes with N-Fluorobenzenesulfonimides
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An efficient and general radical hydroamination of alkenes using Co(salen) as catalyst, N-fluorobenzenesulfonimide (NFSI) and its analogues as both nitrogen source and oxidant was successfully disclosed. A variety of alkenes, including aliphatic alkenes, styrenes, α, β-unsaturated esters, amides, acids, as well as enones, were all compatible to provide desired amination products. Mechanistic experiments suggest that the reaction underwent a metal-hydride-mediated hydrogen atom transfer (HAT) with alkene, followed by a pivotal catalyst controlled SN2-like pathway between in situ generated organocobalt(IV) species and nitrogen-based nucleophiles. Moreover, by virtue of modified chiral cobalt(II)-salen catalyst, an unprecedented asymmetric version was also achieved with good to excellent level of enantiocontrol. This novel asymmetric radical C?N bond construction opens a new door for the challenging asymmetric radical hydrofunctionalization.
- Lv, Guowei,Meng, Qi,Qin, Tao,Xiong, Tao,Zhang, Ge,Zhang, Qian
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supporting information
p. 25949 - 25957
(2021/11/01)
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- Diboron glycol ester as well as preparation method, intermediate and application thereof
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The invention discloses diboron glycol ester as well as a preparation method, an intermediate and application thereof. The diboron glycol ester can be used for inducing reductive coupling reaction with imine as a substrate, and the substrate can be obtained by reaction of aldehyde and ammonia and is very easy to obtain and quite low in cost. The product can be separated from a reaction system onlyby acid-base operation without column chromatography purification, and the post-treatment mode is convenient and easy to operate. The yield of the obtained product is high, and protective group operation is not needed. The diboron glycol ester has chirality, the stereoselectivity of the reductive coupling reaction is generally excellent, and 99% ee chiral diamine can be obtained only through simple recrystallization. The diboron glycol ester can be obtained by reacting diol with diboron glycol ester, the diol is convenient to prepare and easy to amplify, the diol can be recycled from a reaction solution through simple acid-base operation, the recovery rate reaches 95%, and the preparation cost is further saved.
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Paragraph 0130-0135; 0248-0252
(2020/08/02)
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- Enantioselective Reductive Coupling of Imines Templated by Chiral Diboron
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We herein report a general, practical, and highly efficient method for asymmetric synthesis of a wide range of chiral vicinal diamines via reductive coupling of imines templated by chiral diboron. The protocol features high enantioselectivity and stereospecificity, mild reaction conditions, simple operating procedures, use of readily available starting materials, and a broad substrate scope. The method signifies the generality of diboron-enabled [3,3]-sigmatropic rearrangement.
- Chen, Dongping,Li, Kaidi,Tang, Wenjun,Xu, Guangqing,Xu, Ronghua,Zhou, Mingkang
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supporting information
p. 10337 - 10342
(2020/07/04)
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- A New, Short, and Stereocontrolled Synthesis of C2-Symmetric 1,2-Diamines
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The previously unknown 5-spirocyclohexylisoimidazole has been made efficiently and simply by reaction of ammonia, glyoxal hydrate, and cyclohexanone. It is a very useful precursor for the diastereocontrolled synthesis of many C2-symmetric 1,2-diamines, a class which is important for the generation of a variety of C2-symmetric reagents and catalysts for enantioselective synthesis.
- Vemula, Rajender,Wilde, Nathan C.,Goreti, Rajendar,Corey
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supporting information
p. 3883 - 3886
(2017/07/26)
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- Synergistic copper-TEMPO catalysis of intermolecular vicinal diamination of styrenes
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A copper-catalyzed, 2,2,6,6-tetramethyl piperidine N-oxy radical-assisted intermolecular diamination of styrenes with N-fluorobenzenesulfonimide has been developed. The current protocol proved amenable to a diverse array of styrenes via cascade radical addition to readily afford synthetically useful aromatic vicinal diamines with exclusive diastereoselectivity.
- Weng, Shiue-Shien,Hsieh, Kun-Yi,Zeng, Zih-Jian,Zhang, Jia-Wei
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p. 670 - 673
(2017/01/25)
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- Enantio- and Diastereoselective Nitro-Mannich Reaction of α-Aryl Nitromethanes with Amidosulfones Catalyzed by Phase-Transfer Catalysts
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A high-yield, highly diastereo- and enantioselective nitro-Mannich reaction of α-aryl nitromethanes with amidosulfones catalyzed by a novel chiral phase-transfer catalyst, bearing multiple H-bonding donors, derived from quinine was developed. A variety of α-aryl nitromethanes and amidosulfones were investigated; and the corresponding products were obtained in excellent yields with excellent diastereo- and enantioselectivities (up to 99% yield, > 99:1 dr and >99% ee). As a demonstration of synthetic utility, the resulting β-nitroamines could be converted to corresponding meso-symmetric and optically pure unsymmetric anti-1,2-diarylethylenediamines.
- Lu, Ning,Li, Ruxu,Wei, Zhonglin,Cao, Jungang,Liang, Dapeng,Lin, Yingjie,Duan, Haifeng
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p. 4668 - 4676
(2017/05/12)
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- Triptycene-Based Chiral and meso-N-Heterocyclic Carbene Ligands and Metal Complexes
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Based on 1-amino-4-hydroxy-triptycene, new saturated and unsaturated triptycene-NHC (N-heterocyclic carbene) ligands were synthesized from glyoxal-derived diimines. The respective carbenes were converted into metal complexes [(NHC)MX] (M=Cu, Ag, Au; X=Cl, Br) and [(NHC)MCl(cod)] (M=Rh, Ir; cod=1,5-cyclooctadiene) in good yields. The new azolium salts and metal complexes suffer from limited solubility in common organic solvents. Consequently, the introduction of solubilizing groups (such as 2-ethylhexyl or 1-hexyl by O-alkylation) is essential to render the complexes soluble. The triptycene unit infers special steric properties onto the metal complexes that enable the steric shielding of selected areas close to the metal center. Next, chiral and meso-triptycene based N-heterocyclic carbene ligands were prepared. The key step in the synthesis of the chiral ligand is the Buchwald–Hartwig amination of 1-bromo-4-butoxy-triptycene with (1S,2S)-1,2-diphenyl-1,2-diaminoethane, followed by cyclization to the azolinium salt with HC(OEt)3. The analogous reaction with meso-1,2-diphenyl-1,2-diaminoethane provides the respective meso-azolinium salt. Both the chiral and meso-azolinium salts were converted into metal complexes including [(NHC)AuCl], [(NHC)RhCl(cod)], [(NHC)IrCl(cod)], and [(NHC)PdCl(allyl)]. An in situ prepared chiral copper complex was tested in the enantioselective borylation of α,β-unsaturated esters and found to give an excellent enantiomeric ratio (er close to 90:10).
- Savka, Roman,Bergmann, Marvin,Kanai, Yuki,Foro, Sabine,Plenio, Herbert
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p. 9667 - 9675
(2016/07/14)
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- Direct catalytic asymmetric mannich-type reaction of benzyl isocyanide: Stereoselective synthesis of 1,2-diarylethylenediamines
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A direct catalytic asymmetric Mannich-type reaction of benzyl isocyanide using a CuI catalyst and N-(diphenylthiophosphinoyl)imines was developed. The simultaneous activation strategy by soft-soft interaction was the key to promote the reaction using a weakly acidic pronucleophile, benzyl isocyanide. The spontaneous cyclization of the Mannich adduct afforded the corresponding enantioenriched imidazolines, which could be precursors for a variety of 1,2-diarylethylenediamines. Enantioenriched 4,5-diarylimidazolines were directly accessed by catalytic asymmetric C-C bond-forming reaction of benzyl isocyanide and N-(thiophosphinoyl)aldimines. The imidazolines were readily transformed into enantioenriched 1,2-diarylethylenediamines.
- Tamura, Keiji,Kumagai, Naoya,Shibasaki, Masakatsu
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supporting information
p. 3026 - 3031
(2015/05/13)
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- Lipase-catalyzed desymmetrization of meso-1,2-diaryl-1,2-diaminoethanes
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The synthesis and enzyme-catalyzed desymmetrization of meso-1,2-diaryl-1,2- diaminoethanes have been investigated. A family of aromatic meso-1,2-diamines, containing different substitution patterns in the aromatic ring, was first prepared and then desymmetrized enantioselectively using lipases as biocatalysts. Selective alkoxycarbonylation of one of the amino groups was achieved using allyl carbonates, isolating the corresponding allyl monocarbamates with moderate to high enantiomeric excess at 45 C. Candida antarctica lipase types A (CAL-A) and B (CAL-B) displayed the best activities and stereopreferences, with a dramatic influence being observed depending on the diamine structure. Non substituted and para-substituted aryldiamines led to the formation of allyl carbamates with good enantiomeric excess, using CAL-A for the less hindered substrates and CAL-B for the more hindered ones. On the other hand meta- and ortho-derivatives afforded low or negligible conversions and selectivities, respectively.
- Mendez-Sanchez, Daniel,Rios-Lombardia, Nicolas,Garcia-Granda, Santiago,Montejo-Bernardo, Jose,Fernandez-Gonzalez, Alfonso,Gotor, Vicente,Gotor-Fernandez, Vicente
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p. 381 - 386
(2014/04/03)
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- Dual catalyst system for asymmetric alternating copolymerization of carbon dioxide and cyclohexene oxide with chiral aluminum complexes: Lewis base as catalyst activator and lewis acid as monomer activator
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Optically active aluminum complexes such as Schiff base, binuclear β-ketoiminate, and bisprolinol complexes were found to promote asymmetric alternating copolymerizations of carbon dioxide and cyclohexene oxide. The aluminum Schiff base complexes-tetraethylammonium acetate afforded isotactic poly(cyclohexene carbonate)s with low enantioselectivities. Lewis bases having two coordinating sites were utilized to enhance activity and selectivity based on the binuclear structure of the aluminum β-ketoiminate clarified by X-ray crystallography. [2gAlMe]2-bulky bisimidazole produced the alternating copolymer with high enantioselectivity (62% ee). The polymerization is considered to preferentially proceed at more crowded, enantioselective site owing to coordination of bulky Lewis bases to aluminums in less enantioselective sites. 32AlMe-2-picoline also exhibited a high enantioselectivity (67% ee). Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) was applied to perform faster and more enantioselective copolymerizations at low temperature (82% ee). The asymmetric copolymerizations were found to be significantly dependent on size of epoxide, temperature, and kind/amount of activators.
- Nishioka, Kiyoshi,Goto, Hidetoshi,Sugimoto, Hiroshi
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p. 8172 - 8192
(2013/01/15)
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- Enantioseparation of 1-arylethanols via a supramolecular chiral host consisting of N-(2-naphthoyl)-l-aspartic acid and an achiral diamine
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A supramolecular chiral host consisting of N-(2-naphthoyl)-l-aspartic acid (L-1) and meso-1,2-diphenylethylenediamine (2) is effective in enantioseparation of 1-arylethanols (up to 96% ee with 100% inclusion ratio). Here we report three different methods to prepare the inclusion crystals and discuss the chiral recognition mechanism on the basis of X-ray crystallography results.
- Kodama, Koichi,Kanno, Ayaka,Sekine, Eriko,Hirose, Takuji
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experimental part
p. 1877 - 1882
(2012/04/23)
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- A synthesis of the pseudopterosin A-F aglycone
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The synthesis of the pseudopterosin A-F aglycone from 3-methylcatechol features (a) the use of asymmetric Ireland-Claisen and aryl Claisen rearrangements to install three of the four stereocentres present in the molecule and (b) an A→AB→ABC annulation strategy using ring-closing metathesis and cationic cyclisation reactions as the key steps.
- Cooksey, John P.,Kocienski, Philip J.,Schmidt, Arndt W.,Snaddon, Thomas N.,Kilner, Colin A.
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supporting information
p. 2779 - 2785,7
(2020/07/31)
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- Design, synthesis, and biological evaluation of imidazoline derivatives as p53-MDM2 binding inhibitors
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Three series of novel imidazoline derivatives were designed, synthesized, and evaluated for their p53-MDM2 binding inhibitory activities, and anti-proliferation activities against PC3, A549, KB, and HCT116 cancer cell lines. Five of the tested compounds showed enhanced p53-MDM2 binding inhibitory potency and anti-proliferation activities in comparison with that of Nutlin-1. Flow cytometric analysis indicated that compound 7c, one of the most potent p53-MDM2 binding inhibitors with a Ki value of 0.6 μM, showed its ability to arrest cell cycle progression.
- Hu, Chunqi,Li, Xin,Wang, Weisi,Zhang, Lei,Tao, Lulu,Dong, Xiaowu,Sheng, Rong,Yang, Bo,Hu, Yongzhou
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p. 5454 - 5461
(2011/10/30)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 62
(2010/12/31)
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- Optical monitoring of gases with cholesteric liquid crystals
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A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The concept is demonstrated for monitoring carbon dioxide via reversible carbamate formation and for oxygen using the irreversible oxidation of a chiral dithiol to a disulfide. Monitoring of CO2 was achieved by doping a commercial cholesteric liquid crystalline mixture (E7) with 1.6% mol of the 1:1 complex of an optically pure diamine with a TADDOL derivative. Upon exposure to carbon dioxide, the reflection band of a thin film of the mixture shifted from 637 to 495 nm as a consequence of dissociation of the complex after carbamate formation of the diamine. An O2 monitor was obtained by doping E7 with a chiral binaphthyl dithiol derivative and a nonresponsive codopant. The reflection band of the oxygen monitor film changed from 542 to 600 nm, due to the conformational change accompanying oxidation of the dithiol to disulfide. These monitoring mechanisms hold promise for application In smart packaging, where carbon dioxide and oxygen are of special interest because of their roles in food preservation.
- Han, Yang,Pacheco, Katherine,Bastiaansen, Cees W.M.,Broer, Dirk J.,Sijbesma, Rint P.
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body text
p. 2961 - 2967
(2010/05/01)
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- Chiral recognition based on enantioselectively aggregation-induced emission
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(Figure Presented) Novel chiral AIE compounds bearing a tartaric acid group were synthesized. They selectively aggregated with one enantiomer of a number of chiral amines, such that one enantiomer led to strong fluorescence and another enantiomer showed no or only weak fluorescence. This was used for the quantitative analysis of enantiomeric composition.
- Zheng, Yan-Song,Hu, Yu-Jian
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scheme or table
p. 5660 - 5663
(2009/12/26)
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- Homogeneous asymmetric hydrogenation catalyst
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Provide that a useful catalyst for homogeneous hydrogenation, particularly a catalyst for homogeneous asymmetric hydrogenation for hydrogenation, particularly asymmetric hydrogenation, which is obtainable with comparative ease and is excellent in economically and workability, and a process for producing a hydrogenated compound of an unsaturated compound, particularly an optically active compound using said catalyst with a high yield and optical purity.
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- Stereospecific diaza-cope rearrangement driven by steric strain
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(Chemical Equation Presented) Bucklingunder the strain: Steric strain was used to drive the diaza-Cope rearrangement to completion (see scheme) with a high degree of stereospecificity (>99.5% ee), as evidenced by chiral-phase HPLC and crystal data. There is good agreement between the experimental and computational values for the rate and equilibrium constants for the rearrangement.
- Kim, Hyunwoo,Nguyen, Yen,Lough, Alan J.,Chin, Jik
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scheme or table
p. 8678 - 8681
(2009/05/15)
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- Titanium(IV)(salen) and yanadium(V)(salen) complexes derived from C 2- and C1-symmetric diamines for asymmetric cyanohydrin synthesis
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Titanium and vanadium salen complexes have been prepared from C 2- and C1-symmetric acyclic diamines. All of the complexes catalysed the asymmetric addition of trimethylsilyl cyanide to benzaldehyde and the sense of asymmetric induction was determined by the nature of the substituents. The vanadium complex of a valine-derived diamine gave good results with a range of aromatic and aliphatic aldehydes. Georg Thieme Verlag Stuttgart.
- Belokon', Yuri N.,Hunt, Jamie,North, Michael
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scheme or table
p. 2150 - 2154
(2009/05/07)
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- A convenient preparation of enantiomerically pure (+)-(1R,2R)- and (-)-(1S,2S)-1,2-diamino-1,2-diphenylethanes
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A gram-scale preparation of (1S,2S)- and (1R,2R)-1,2-diamino-1,2- diphenylethanes, (1S,2S)-1 and (1R,2R)-1, is reported via (±)-iso-amarine 4. Strategically, the activation of (±)-iso-amarine 4 for hydrolysis to the required diamines and enantiomeric resolution is achieved simultaneously by formation of two separable diastereoisomeric N-acylamidines 5 and 6 derived from direct DCC-mediated coupling of (±)-iso-amarine 4 with (R)-acetylmandelic acid. iso-Amarine 4 is conveniently obtained from amarine 3, and a one-pot synthesis of the latter is reported from benzaldehyde and hexamethyldisilazane as catalysed by benzoic acid.
- Braddock, D. Christopher,Redmond, Joanna M.,Hermitage, Stephen A.,White, Andrew J. P.
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p. 911 - 916
(2007/10/03)
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- Highly diastereoselective and enantioselective addition of organometallic reagents to a chiral C2-symmetrical bisimine
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An efficient and straightforward method has been developed for the preparation of enantiomerically enriched C2-symmetrical vicinal diamines via the addition of organometallic reagents to a chiral bisimine, which gives access to a variety of optically pure aromatic and aliphatic C 2-symmetrical vicinal diamines in high yields. The 'Cram-Davis' open transition state model is proposed to rationalize the observed stereoselectivities for the addition of organolithium reagents to the bisimine. Georg Thieme Verlag Stuttgart.
- Sun, Xiaoxia,Wang, Shuangjun,Sun, Shangjin,Zhu, Jin,Deng, Jingen
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p. 2776 - 2780
(2007/10/03)
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- Efficient resolution of N-Boc-7-azabicyclo[2.2.1]hept-5-en-2-one: Formal syntheses of natural epibatidine and its enantiomer
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The efficient resolution of racemic N-Boc-7-azabicyclo[2.2.1]hept-5-en-2- one (±)-2 via aminal formation with (R,R)-1,2-diphenylethylenediamine 4 is reported. Acidic hydrolysis furnishes the enantiomeric ketones (+)-2 and (-)-2 that were transformed into 7-azabicyclo[2.2.1]heptan-2-one (-)-3 and (+)-3. The process constitutes a formal synthesis of (+)- and (-)-epibatidine.
- Moreno-Vargas, Antonio J.,Vogel, Pierre
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p. 3173 - 3176
(2007/10/03)
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- Reductive coupling of aromatic oxims and azines to 1,2-diamines using Zn-MsOH or Zn-TiCl4
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The reduction of aromatic aldoxims and azines with Zn in the presence of MsOH or TiCl4 afforded N,N′-unsubstituted 1,2-diamines in one-step. The reductive coupling with Zn-MsOH gave meso 1,2-diamines selectively, whereas dl 1,2-diamines were fo
- Kise, Naoki,Ueda, Nasuo
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p. 2365 - 2368
(2007/10/03)
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- Stereoselective ring opening reactions
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The present invention relates to a process for stereoselective or regioselective chemical synthesis which generally comprises reacting a nucleophile and a chiral or prochiral cyclic substrate in the presence of a non-racemic chiral catalyst to produce a stereoisomerically or regioselectively enriched product.
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- Efficient N-N bond cleavage of chiral trisubstituted hydrazines with BH3·THF
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Cleavage of the N-N bond of chiral trisubstituted hydrazines 1 with excess BH3·THF complex gives the corresponding optically active amines 2 in moderate to excellent yields and with high enantiomeric purity. This racemization and epimerization free cleavage procedure is compatible with functionalities sensitive to reductive cleavage conditions.
- Enders, Dieter,Lochtman, René,Meiers, Michaela,Müller, Stephan,Lazny, Ryszard
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p. 1182 - 1184
(2007/10/03)
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- Organic chemistry: Preparative synthesis of the Corey chiral controller for enantioselective dihydroxylation of olefins
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A five-step synthesis of both enantiomers of 1,2-di(2,4,6-trimethylbenzylamino)-1,2-diphenylethane, i.e., Corey (R,R)- and (S,S)-controllers for enantioselective dihydroxylation of olefins by osmium tetroxide, starting from α,α'-diphenylglyoxime, has been developed. The key operations in the synthesis are the optical resolution of intermediate rac-1,2-diamino-1,2-diphenylethane into two enantiomers using only (R,R)-tartaric acid and the subsequent enhancement of the enantiomeric purity to >98% by crystallizations of the corresponding Schiff's bis-bases. Analysis of the enantiomeric purity of the controllers can be easily performed using 1H NMR spectra of their salts with (R)-α-methoxy-α-(trifluoromethyl)phenylacetic acid (Mosher R-acid).
- Lapitskaya,Pivnitsky
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- A simplified synthesis of (±)-1,2-Diphenyl-1,2-diaminoethane (1) from benzaldehyde and ammonia. Revision of the structures of the long-known intermediates 'hydrobenzamide' and 'amarine'
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A new pathway for the simple, stereocontrolled and economical synthesis of (±)-1 from benzaldehyde is described. The structures of two intermediates (Scheme 1) have been revised to those shown in Scheme 2.
- Corey,Kuehnle, Florian N. M.
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p. 8631 - 8634
(2007/10/03)
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- Stereoselective ring opening reactions
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The present invention relates a process for stereoselective or regioselective chemical synthesis which generally comprises reacting a nucleophile and a chiral or prochiral cyclic substrate in the presence of a non-racemic chiral catalyst to produce a steroisomerically or regioselectively enriched product.
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- Synthesis of Nitrogen-Containing Macrocycles with Reductive Intramolecular Coupling of Aromatic Diimines
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Reductive intramolecular coupling of aromatic diimines is an effective method for the synthesis of a variety of nitrogen-containing macrocycles. 1,4-Diazacrown ethers 3 were effectively synthesized by intramolecular coupling of bis(imino ethers) 9 promoted by electroreduction (method A) or chemical reduction with zinc powder (method B) in the presence of methanesulfonic acid.In spite of the formation of macrocycles, the yields of 3 were relatively high.This can be explained by the formation of proton-bridged intermediates 14, in which intramolecular hydrogen bonds are formed between hydrogen and oxygen atoms of diiminium salts.Method B was more effective in the formation of 1,4-diaza-12-crown-4 derivatives 3 (n = 1) due to the template effect of Zn(2+).Optically active macrocyclic bislactones 4 were synthesized stereoselectively by reductive intramolecular coupling of bis(imino esters) 20 with zinc powder (method B).The high stereoselectivity is explained by considering proton-bridged intermediate 23.The resultant compounds 4 were transformed to optically active 1,2-diarylethylenediamines 7.Various sizes of macrocyclic bislactams 5 were synthesized by reductive intramolecular coupling of bis(imino amides) 26 with zinc powder (method B).Reduction of 5 gave the corresponding macrocyclic polyamines 6.
- Kise, Naoki,Oike, Hideaki,Okazaki, Eiichi,Yoshimoto, Masami,Shono, Tatsuya
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p. 3980 - 3992
(2007/10/02)
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- Convenient Routes to Symmetrical Benzils and Chiral 1,2-Diaryl-1,2-diaminoethanes, Useful Controllers and Probes for Enantioselective Synthesis
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Pathways for the diastereoselective preparation of chiral 1,2-diaryl-1,2-diaminoethanes from ArCOOH, ArCHO or ArBr are described.
- Corey, E. J.,Lee, Duck-Hyung,Sarshar, Sepehr
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- Stereocontrol in the reduction of 1,2-diimine with an oxazaborolidine catalyst. Highly stereoselective preparation of (R,R)-1,2-diphenylethylenediamine
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Highly enantioselective reduction of 1,2-bis(p-methoxyphenylimino)-1,2-diphenylethane was conducted even with 0.5 mol% of new oxazaborolidine derived from L-threonine and a stoichiometric amount of BH3·THF to give 1,2-diphenylethylenediamine derivative in excellent enantiomeric purity. The subsequent deprotection of nitrogen atoms afforded (R,R)-1,2-diphenylethylenediamine in enantiomerically pure form.
- Shimizu, Makoto,Kamei, Mie,Fujisawa, Tamotsu
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p. 8607 - 8610
(2007/10/02)
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- Epimerization-Crystallization Method in Optical Resolution of 2,2'-Dihydroxy-1,1'-binaphthyl, and Kinetic Study
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Optical resolution of 2,2'-dihydroxy-1,1'-binaphthyl (1) with (R,R)-1,2-cyclohexanediamine (2) in toluene yielded optically pure (R)-1 in a yield of 160percent based on the theoretical amount of the enantiomer contained in the racemate by selective crystallization of a less soluble complex, (R)-1*(R,R)-2, and epimerization of more soluble complex, (S)-1*(R,R)-2.Also optically pure (S)-1 was obtained with the same enantiomer of the resolving agent, (R,R)-2, in a yield of 154percent. (R,R)-1,2-Diphenyl-1,2-ethanediamine (3) was a suitable resolving agent for both 1 and 6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl.Kinetic study indicated that the reversible first-order rate constants for the epimerizations of (S)-1*(R,R)-2 and (S)-1*(R,R)-3 were larger than that for the racemization of (S)-1.The activation energy and frequency factor for the epimerization of (S)-1*(R,R)-2 were 109 kJ mol-1 K-1 and 3E10 s-1, respectively, and those for (S)-1*(R,R)-3 were 96 kJ mol-1 and 1E8 s-1, while those for the racemization of (S)-1 were 85 kJ mol-1 K-1 and 9E5 s-1, respectively.
- Kawashima, Masatoshi,Hirata, Reiko
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p. 2002 - 2005
(2007/10/02)
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- A novel method for stereoselective synthesis of (1R,2R)-diarylethylenediamines by reductive intramolecular coupling of aromatic diimines
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Reduction with zinc has been found to be an effective method for selective synthesis of (1R,2R)-diarylethylenediamines from the corresponding chiral aromatic diimines through their intramolecular coupling.
- Shono, Tatsuya,Kise, Naoki,Oike, Hideaki,Yoshimoto, Masami,Okazaki, Eiichi
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p. 5559 - 5562
(2007/10/02)
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- Stereochemical Studies of N,N'-Diacetyl-N,N'-dimethyl-1,2-diamino-1,2-diphenylethanes and their Mono- and Di-thio Analogues by NMR and CD Spectroscopy and by Molecular Mechanics Calculations
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The R*,R* and R*,S* diastereomers of N,N'-diacetyl-N,N'dimethyl-1,2-diamino-1,2-diphenylethane and their mono- and di-thio analogues (1-6) have been studied by 1H and 13C NMR spectroscopy and by empirical force-field calculations (MMP2-85).The NMR spectral data (chemical shifts, coupling constants and NOE) clearly show that all compounds exist in the anti conformation with the Z,Z configuration for the (thio)amide groups.The same result is obtained by the force-field calculations.Four of the compounds (2, 3, 4 and 6) are chiral and have been resolved into enantiomers by chromatography on triacetylcellulose.The CD spectra of the first eluted enantiomers of 4 and 6 could be reasonably well reproduced by calculations based on minimum energy geometries for the S,S enantiomers, whereas no agreement could be reached for 2 and 3.This agrees with the results of the force-field calculations, which predict one predominant conformer for each of 4 and 6, but significant amounts of two rotamers (both anti ZZ) for each of 2 and 3.
- Chiara, Jose Luis,Petrova, Rumyana,Simeonov, Mario,Spassov, Stefan L.,Khan, Agha Zul-Quarnain,Sandstroem, Jan
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p. 555 - 562
(2007/10/02)
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- An efficient and practical route to enantiomerically pure (+)-(1R,2R)- and (-)-(1S,2S)-1,2-diphenylethane-1,2-diamines
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The synthesis of the title compounds is easily achieved by the asymmetric Sharpless dihydroxylation of trans-stilbene to the corresponding enantiomerically pure diols. The conversion of the diols to the di-p-toluenesulfonates and subsequent reaction with sodium azide affords the diazides, which are reduced by lithium aluminum hydride to the optically pure 1,2-diamines.
- Pini,Iuliano,Rosini,Salvadori
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p. 1023 - 1024
(2007/10/02)
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- 208. Aminierende reduktive Kupplung aromatischer Aldehyde mit niedervalenten Titan-Reagenzien zu 1,2-Diarylethylendiaminen
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In a novel McMurry-type one-pot reaction, aromatic aldehydes and secondary amines are coupled to give the N,N,N',N'-tetralkyl-1,2-diarylethylendiamines 1-22 (Table 3).To this end, a lithium dialkylamide is added to an aromatic aldehyde to give the adduct B which is then treated with 1 equiv. of TiCl4 to yield a coloured suspension of a reagent synthetically equivalent to a iminium salt (C/D in Scheme 4).After treatment with a low-valent Ti reagent which is prepared by reduction of TiCl4 with either K or, preferably, Mg, the coupling products are isolated in 23 to 81 percent yield as a 1:1 mixture of the diastereoisomers (meso- and rac-form).These are separated either by chromatography or by crystallization and characterized.
- Betschart, Claudia,Seebach, Dieter
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p. 2215 - 2231
(2007/10/02)
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- Improved Optical Resolution of (+/-)-1,2-Diphenylethylenediamine
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(+/-)-1,2-Diphenylethylenediamine (DPEDA) was efficiently resolved by the fractional crystallization of its diastereomeric salts with optically active mandelic acid. 1H-NMR spectrum of N-monoacylated DPEDA with an optically active derivatizing agent showed that DPEDA thus obtained was optically pure.
- Saigo, Kazuhiko,Kubota, Naomi,Takebayashi, Shoko,Hasegawa, Masaki
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p. 931 - 932
(2007/10/02)
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- ASYMMETRIC REDUCTION OF ACETOPHENONE WITH CHIRAL REAGENTS FROM LITHIUM TETRAHYDROALUMINATE AND CHIRAL 1,2-DIOL OR DIAMINE AS STUDIED BY ALUMINUM-27 NUCLEAR MAGNETIC RESONANCE
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Asymmetric reduction of acetophenone with chiral reagents from lithium tetrahydroaluminate and (1S,2S)-1,2-diphenylethanediol or (1S,2S)-N,N'-diethyl-1,2-diphenylethanediamine in the presence or absence of added ethanol is studied by aluminum-27 NMR spectroscopy.
- Yamashita, Junzo,Tomiyama, Shigemi,Hashimoto, Harukichi,Kitahara, Keiichi,Sato, Hisao
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p. 749 - 752
(2007/10/02)
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- Thermal Rearrangements and Nucleophilic Ring Cleavage of cis-2,3-Dihydro-2,3-diphenyl-1H-1,4-diazepines
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Thermolysis of cis-2,3-dihydro-2,3-diphenyl-1H-1,4-diazepine (c2a) at 150 deg C in 5>bromobenzene solution affords quantitatively 2,3-diphenylpyridine (4a) via ring contraction and loss of one mole of ammonia.In striking contrast, on heating a 5>bromobenzene solution of cis-2,3-dihydro-2,3,6-triphenyl-1H-1,4-diazepine (c2b) to 140 deg C loss of C7H8 occurs resulting in the formation of 2,5-diphenylpyrimidine (5b) in 70percent yield.Mechanisms are proposed in order to rationalize these surprising ring contractions.Piperidine in methanol cleaved the ring of c2a*H+ producing meso-1,2-diphenyl-1,2-ethanediamine (12) and 1,3-dipiperidinopropenylium perchlorate (13).
- Quast, Helmut,Seidenspinner, Hubert-Matthias,Stawitz, Josef
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p. 1230 - 1236
(2007/10/02)
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