- Novel α-amino acid-derived phase-transfer catalyst application to a highly enantio- and diastereoselective nitro-Mannich reaction
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New quaternary ammonium types of bifunctional asymmetric phase-transfer catalysts bearing multiple hydrogen-bonding donors derived from α-amino acids were readily prepared and found to be highly efficient in the asymmetric nitro-Mannich reactions of amidosulfones. Very broad substrate generality was observed, and the products were achieved in high enantio-/diastereoselectivities (90->99.9% ee, 90:10 to 92:8 dr). Compared with previous reports, the enantioselectivity of aliphatic amidosulfones has been improved to a high level (91-93% ee).
- Liu, Yuxin,Wei, Zhonglin,Leu, Yu,Cao, Jungang,Liang, Dapeng,Lin, Yingjie,Duan, Haifeng
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p. 9234 - 9242
(2017/11/14)
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- Palladium-Catalyzed Modular Synthesis of Substituted Piperazines and Related Nitrogen Heterocycles
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We report here a novel method for the modular synthesis of highly substituted piperazines and related bis-nitrogen heterocycles via a palladium-catalyzed cyclization reaction. The process couples two of the carbons of a propargyl unit with various diamine components to provide nitrogen heterocycles in generally good to excellent yields and high regio- and stereochemical control. (Chemical Equation Presented).
- Montgomery, Thomas D.,Rawal, Viresh H.
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supporting information
p. 740 - 743
(2016/03/01)
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- Enantioselective aza-Henry reaction for the synthesis of (S)-levamisole using efficient recyclable chiral Cu(II)-amino alcohol derived complexes
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Chiral Cu(II) complexes were generated in situ by the interaction of aminoalcohol based ligands L1-L6 derived from (1R,2S)-(-)-2-aminodiphenylethanol, (1R,2S)-1-amino-2,3-dihydro-1H-inden-2-ol, (R or S)-valinol and (S)-2-amino-1,1-diphenylpropan-1-ol with 4-tert-butyl-2,6-diformylphenol and screened for aza-Henry reaction of a variety of aromatic, aliphatic N-tosylaldimine and aromatic N-benzenesulfonamide aldimine in toluene at RT. Excellent enantioselectivity, diastereoselectivity (99%) of β-nitro-N-tosylaldamine with good yield (80%) was achieved in case of complex L2-Cu(II) with low catalyst loading. The enantio-pure aza-Henry product obtained was straightforwardly transformed into the enantioenriched chiral vicinal diamine (ee; 96%) with good yield in successive two steps and was further used for the synthesis of (S)-levamisole (an anthelminthic agent). The catalytic system worked well up to five cycles with retention of enantioselectivity.
- Choudhary, Manoj K.,Tak, Rajkumar,Kureshy, Rukhsana I.,Ansari, Amamudin,Khan, Noor-Ul H.,Abdi, Sayed H.R.,Bajaj, Hari C.
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- Chiral Cu(ii)-amino alcohol based complexes for asymmetric aza-Henry reaction of N-Ts imines
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A series of chiral dimeric ligands 1A-C, 2A-B, 3A-B and 4A derived from (S)/(R) 1,1′-bi(2-naphthol)-bis-aldehyde/piperazine-bis-aldehyde and various aminoalcohols viz., (1R,2S)-(-)-2-aminodiphenylethanol, (1S,2R)-(-)-2-aminodiphenylethanol, (1R,2S)-1-amino-2,3-dihydro-1H-inden-2-ol and (R)-valinol were synthesized. In situ generated complexes 1A-C-, 2A-B-, 3A-B-, 4A-Cu(ii)/Cu(i) of dimeric chiral ligands with different copper salts were used as catalysts for the asymmetric aza-Henry reaction of a variety of N-tosylimines as substrates with different nitroalkanes at RT to afford good yields of aza-Henry products (80% with respect to the imines) with excellent enantioselectivity (ee > 99%) in 24 h with nitromethane and high syn selective products with excellent enantioselectivity with nitroethane. The dimeric chiral Cu(ii) complex 1A-Cu(ii) retained its performance at the gram level and was expediently recycled for a number of times. The enantio-pure aza-Henry product was further used for the synthesis of (S)-levamisole (an anthelminthic agent) in good yield and ee in three steps. The Royal Society of Chemistry.
- Choudhary, Manoj K.,Das, Anjan,Kureshy, Rukhsana I.,Kumar, Manish,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
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p. 548 - 555
(2014/02/14)
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- Oxazoline-based organocatalyst for enantioselective strecker reactions: A protocol for the synthesis of levamisole
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A chiral oxazoline-based or-ganocatalyst has been found to efficiently catalyze asymmetric Strecker reactions of various aromatic and aliphatic N-benzhydrylimines with trime-thylsilyl cyanide (TMSCN) as a cyanide source at -20°C to give α-aminoni-triles in high yield (96%) with excellent chiral induction (up to 98% ee). DFT calculations have been performed to rationalize the enantioselective formation of the product with the organo-catalyst in these reactions. The organo-catalyst has been characterized by single-crystal X-ray diffraction analysis, as well as by other analytical methods. This protocol has been extended to the synthesis of the pharmaceutically important drug molecule levamisole in high yield and with high enantioselectivity.
- Sadhukhan, Arghya,Sahu, Debashis,Ganguly, Bishwajit,Khan, Noor-Ul H.,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Suresh,Bajaj, Hari C.
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supporting information
p. 14224 - 14232
(2013/11/06)
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- Novel bifunctional thiourea-ammonium salt catalysts derived from amino acids: Application to highly enantio- and diastereoselective aza-Henry reaction
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The development of new efficient and easily accessible catalysts has been one of the focuses in asymmetric phase-transfer catalysis. In this paper, a novel class of chiral bifunctional thiourea-ammonium phase-transfer catalysts were synthesized from commercially available α-amino acids. The structural modularity of these catalysts permits facile tunings to achieve optimum results, which was demonstrated in catalyzing the aza-Henry reaction with excellent enantioselectivities (up to 99.5% ee) and diastereoselectivities (up to >25:1 dr).
- Wang, Hong-Yu,Chai, Zhuo,Zhao, Gang
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p. 5104 - 5111
(2013/06/27)
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- Enantioselective metal-free diamination of styrenes
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Metal-free and asymmetric: The first enantioselective diamination of styrenes simply requires a chiral hypervalent iodine(III) reagent as an oxidant and bismesylimide as a nitrogen source (see scheme, Ms=methanesulfonyl). The reaction proceeds under mild conditions and with high enantiomeric excess.
- Roeben, Caren,Souto, Jose A.,Gonzalez, Yolanda,Lishchynskyi, Anton,Muniz, Kilian
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supporting information; scheme or table
p. 9478 - 9482
(2011/11/06)
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- Synthesis of optically active imidazolines, azapenams, dioxocyclams, and bis-dioxocyclams
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Optically active 4-methyl-4-carbomethoxy-Δ2-imidazoline was efficiently synthesized on a multigram scale. Photolysis with (methoxymethylcarbene)chromium complex produced the optically active azapenam in good yield and with high stereoselectivity. Acid-catalyzed dimerization followed by reduction produced the corresponding optically active dioxocyclam in good yield. Using a bis-carbene complex, an optically active bis-dioxocyclam was produced in excellent yield.
- Hsiao, Yi,Hegedus, Louis S.
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p. 3586 - 3591
(2007/10/03)
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- Enantioselective catalytic reductions of ketones with new four membered oxazaborolidines: Application to (S)-tetramisole
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Enantioselective catalytic reduction of ketones with both the enantiomers of new four membered oxazaborolidines is described.
- Rama Rao,Gurjar,Kaiwar
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p. 859 - 862
(2007/10/02)
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- Benzo[1,8]naphthyridine derivatives, their preparation and compositions containing them
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New benzo[b][1,8]naphthyridine derivatives of general formula (I), in which R1 is a hydrogen atom or a hydroxyl or alkyl radical, R2 is a hydrogen atom or an alkyl, fluoroalkyl, cycloalkyl (3 to 6 C), alkyloxy or alkylamino radical, R3 is a phenyl or phenylalkyl radical substituted with one or more halogen atoms or alkyl, cycloalkyl (3 to 6 C), alkyloxy, cyano, amino, alkylamino, dialkylamino, alkyloxyalkyl, hydroxyalkyl, hydroxyalkyloxy, methylenedioxy, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl radicals, or R3 is a heterocyclic radical, and R4 is a hydrogen atom or a fluorine atom, the alkyl radicals (1 to 4 C) being linear or branched, their salts, their preparation and compositions containing them. These new products are useful as antimicrobials, or in the treatment of AIDS. STR1
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