- Synthesis of chiral 2,3-disubstituted 1,4-diazabicyclo[2.2.2]octane derivatives
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Racemic 2,3-diaryl-1,4-diazabicyclo[2.2.2]octane (DABCO) derivatives are synthesized from the readily accessible piperazines in 50-64% yield by cyclization using ethylene bromide, triethylamine, and KI at 80 °C. The enantiomerically enriched 2,3-diphenylpiperazine and the 2,3-bis(1-naphthyl)piperazine derivatives are prepared by a resolution method using commercially available optically active acids, yielding the corresponding DABCO derivatives in 51-64% yield with up to 99% ee. This mild cyclization can also be applied to enantiopure camphanyldiamine derivatives, and the products are obtained in 72-86% yields.
- Periasamy, Mariappan,Edukondalu, Athukuri,Reddy, Polimera Obula
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p. 3651 - 3655
(2015/04/22)
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- YbCl3-catalyzed one-pot synthesis of dihydropyrazines, piperazines, and pyrazines
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A simple and efficient synthetic approach to dihydropyrazines via YbCl 3-catalyzed reaction of α-hydroxyketones with diamines under mild conditions was developed. The corresponding 2,3-subsitituted piperazines and pyrazines were obtained through tandem conversion of dihydropyrazines with good yields.
- Fan, Liyan,Chen, Wen,Qian, Changtao
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supporting information
p. 231 - 234
(2013/02/23)
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- Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation
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Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.
- Periasamy, Mariappan,Sanjeevakumar, Nalluri,Dalai, Manasi,Gurubrahamam, Ramani,Reddy, Polimera Obula
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supporting information; experimental part
p. 2932 - 2935
(2012/08/28)
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- A new Yb3+-catalyzed pinacol and imine-coupling reaction
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Ytterbium triflate, Yb(OTf)3, catalyzes the intermolecular reductive homocouplings of imines, aldehydes, and ketones at loadings of 5 mol % in the presence of Mg and Me3SiCl to give isolated yields of up to 95%. Diastereoselectivity of up to 4/96 (dl/meso) is achieved for aromatic aldehydes, up to 100% dl for aliphatic aldehydes, and 100% dl for an intramolecular imine coupling.
- Aspinall, Helen C.,Greeves, Nicholas,Hin, Shane Lo Fan
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experimental part
p. 1558 - 1561
(2010/06/13)
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- A bifunctional PdVMgO solid catalyst for the one-pot selective N-monoalkylation of amines with alcohols
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It has been found that a bifunctional metal Pd/base (MgO) catalyst performs the selective monoalkylation of amines with alcohols. The reaction goes through a series of consecutive steps in a cascade mode that involves: 1) the abstraction of hydrogen from the alcohol that produces the metal hydride and the carbonyl compound; 2) condensation of the carbonyl with the amine to give an imine, and 3) hydrogenation of the imine with the surface hydrogen atoms from the metal hydride. Based on isotopic and spectroscopic studies and on the rate of each elementary step, a global reaction mechanism has been proposed. The controlling step of the process is the hydride transfer from the metal to the imine. By changing the crystallite size of the Pd, it is demonstrated that this is a structure-sensitive reaction, whereas the competing processes that lead to subproducts are not. On these bases, a highly selective catalyst has been obtained with Pd crystallite size below 2.5 nm in diameter. The high efficiency of the catalytic system has allowed us to extend the process to the one-pot synthesis of piperazines.
- Corma, Avelino,Rodenas, Tania,Sabater, Maria J.
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supporting information; experimental part
p. 254 - 260
(2010/03/26)
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- New chiral titanium complexes for enantioselective reductive cyclizations of diimines to trans-2,3-diarylpiperazines
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Enantioselective intramolecular reductive coupling of diimines by chiral titanium complexes, prepared using a titanium(IV) reagent and hemisalen ligands derived from chiral β-amino alcohols, gives trans-2,3-diarylpiperazines in up to 97% ee.
- Vairaprakash, Pothiappan,Periasamy, Mariappan
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p. 1233 - 1236
(2008/09/17)
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- A simple method of synthesis of (±)-2,3-diarylpiperazines and a novel method of resolution of (±)-2,3-diphenylpiperazine
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Intramolecular reductive coupling of diimines in the presence of Zn/Ti(OiPr)2Cl2 gives the corresponding (±)-2,3-diarylpiperazines in 73-83% yields with dl/meso ratio >99%: 1%. The (±)-2,3-diphenylpiperazine obtained in t
- Vairaprakash, Pothiappan,Periasamy, Mariappan
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p. 3636 - 3638
(2007/10/03)
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- A facile synthesis of vicinal diamines promoted by low-valent niobium: Preparation of chiral octahydrobiisoquinolines and their application to catalytic asymmetric synthesis
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An efficient homocoupling of imines to give vicinal diamines promoted by low-valent niobium, generated by treatment of NbCl5 with zinc powder, is described. The desired products were obtained in good to excellent yields. Dihydroisoquinoline derivatives also gave the coupling products with good diastereoselectivities (D,L/meso). Optical resolution of the racemic octahydrobiisoquinolines was achieved and their complexes with Cu1 used in the catalytic asymmetric oxidative coupling of β-naphthols. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Arai, Shigeru,Takita, Satoshi,Nishida, Atsushi
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p. 5262 - 5267
(2007/10/03)
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- Diastereoselective synthesis of piperazines by manganese-mediated reductive cyclization.
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A simple and effective synthesis of trans aryl-substituted piperazines using a Bronsted acid and manganese(0) is described. [reaction: see text]
- Mercer, Gregory J,Sigman, Matthew S
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p. 1591 - 1594
(2007/10/03)
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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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- Generation of 2-azaallyl anions by the transmetalation of N-(trialkylstannyl)methanimines. Pyrrolidine synthesis by [3 + 2] cycloadditions with alkenes
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Treatment of N-(trimethylstannyl)methanimines or N-(tri-n-butylstannyl)methanimines with methyllithium or n-butyllithium, respectively, affords 2-azaallyl anions by tin-lithium exchange. These anions undergo intermolecular or intramolecular [π4s + π2s] cycloadditions with alkenes and alkynes to generate pyrrolidines or pyrrolines after quenching with water or other electrophiles. The tin-lithium exchange method allows unstabilized 2-azaallyl anions to be generated for the first time. The lifetime of the anions is limited by a competing intermolecular side reaction. Therefore, relatively reactive alkenes and alkynes must be used, such as stilbene, styrenes, enynes, diphenylacetylene, vinyl sulfides, vinyl selenides, and vinyl silanes. The latter three types of anionophiles afford functionalized cycloadducts which may be transformed into more useful pyrrolidines by reduction, elimination, or oxidation. A synthesis of the alkaloid (±)-mesembrane was accomplished using an intramolecular 2-azaallyl anion cycloaddition.
- Pearson, William H.,Szura, Daniel P.,Postich, Michael J.
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p. 1329 - 1345
(2007/10/02)
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- Electroorganic Chemistry. 129. Electroreductive Synthesis of Chiral Piperazines and Enantioselective Addition of Diethylzinc to Aldehydes in the Presence of the Chiral Piperazines
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Electroreduction of diimines, prepared from 1,2-diamines and aromatic aldehydes, in acidic media gave intramolecularly coupled products, 2,3-diarylpiperazines, stereoselectively.Chiral tri- and tetrasubstituted piperazines were synthesized effectively fro
- Shono, Tatsuya,Kise, Naoki,Shirakawa, Eiji,Matsumoto, Hideshi,Okazaki, Eiichi
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p. 3063 - 3067
(2007/10/02)
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- Deprotonation de N-oxydes d'amines aliphatiques: schema reactionnel general et nouvelle synthese de pyrrolidines
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Amine oxides, 1, 5, 10, 15, 21, 23, when treated by lithium diisopropylamide undergo deprotonation.Monodeprotonation gives rise either to secondary amines and benzaldehyde resulting from the hydrolysis of an intermediate immonium (I) or to hydroxylamines via a Stevens-like rearrangement observed for the first time on an amine oxide.Double deprotonation gives an immonium ylid (Y) which, depending upon the structure of the initial tertiary amine yields either "head to head" piperazines (biradical-like behavior of (DD)) or aziridines.The immonium ylid (Y5) derived from trimethylamine oxide, whose formation and reactivity are reported for the first time, has remarkable property of undergoing cycloaddition reactions with unactivated olefins, leading to a new and efficient synthesis of various pyrrolidines.
- Beugelmans, Rene,Benadjila-Iguertsira, Leila,Chastanet, Jacqueline,Negron, Guillermo,Roussi, Georges
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p. 725 - 734
(2007/10/02)
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