- Menthylamine synthesis via gold-catalyzed hydrogenation of menthone oxime
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In the current work gold nanoparticles supported on oxides (MgO, Al2O3, ZrO2, TiO2) were used for menthylamine synthesis via menthone oxime hydrogenation. An increase of the gold nanoparticles size and application of metal oxides with a strong basic character such as magnesia favored deoximation to menthone. Au/Al2O3 catalyst with the gold nanoparticles size of 2.0 nm afforded high catalytic activity and selectivity to menthylamine. The reaction kinetics including stereoselectivity to the reaction products and recyclability of the catalyst was studied using Au/Al2O3 in the temperature range 90?110 °C under hydrogen pressure of 5.5–7.5 bar. The catalytic behavior was influenced by the solvent nature, with higher selectivity to desired amine achieved using methanol. The reaction rate was pressure independent, while has first order with respect to menthone oxime concentration. Stereoselectivity to menthylamines and menthones was independent on the reaction temperature and the hydrogen pressure.
- Demidova, Yu. S.,Mozhaitsev, E. S.,Murzin, D. Yu.,Nefedov, A. A.,Salakhutdinov, N. F.,Saraev, A. A.,Simakov, A.,Simakova, I. L.,Suslov, E. V.,Volcho, K. P.
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- Synthesis of Previously Inaccessible Derivatives of 1,4,7-Tri-R-1,4,7-Triazacyclononane, Including Chiral Examples, and a Rapid Synthesis of the HCl Salts of H3tacn and H4dtne
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The synthesis of 1,4-di-tert-butyl-7-R-1,4,7-triazacyclononane (tBu2Rtacn) derivatives through a “crab-like” cyclization is reported. The tert-butyl groups were cleavable with concentrated hydrochloric acid, allowing for a facile and convenient synthesis of the HCl salt of H3tacn and the most direct route to its industrially relevant binucleating N-ethylene bridged derivative, H4dtne. In addition, the synthesis of chiral tacn derivatives with both one and two stereocenters in non-annulet, alpha-N positions is reported.
- Pickel, Thomas C.,Karahalis, Gregory J.,Buru, Cassandra T.,Bacsa, John,Scarborough, Christopher C.
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p. 6876 - 6889
(2019/01/04)
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- Triiodide-Mediated δ-Amination of Secondary C?H Bonds
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The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)-mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2-mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide-mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates.
- Wappes, Ethan A.,Fosu, Stacy C.,Chopko, Trevor C.,Nagib, David A.
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p. 9974 - 9978
(2016/08/16)
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- Diastereoselective desymmetrization of diarylphosphinous acid-borane amides under Birch reduction
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Treatment of diarylphosphinous acid-borane amides possessing chiral amido functionality with an alkali metal solution in liquid ammonia induced a preferential dearomatization of one aryl substituent at phosphorus leading to the formation of non-equimolar amounts of diastereomers. Diastereoselectivity of dearomatization depends strongly on the structure of a chiral auxiliary.
- Stankevi?, Marek
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p. 6082 - 6102
(2015/06/08)
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- Efficient resolution of menthylamine with inexpensive (r,r)-tartaric acid by dielectrically controlled resolution (DCR)
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A practical procedure for the resolution of menthylamine 2 with (R,R)-tartaric acid [(R,R)-3] as resolving agent is presented. Variation of the solvent system allows both enantiomers of 2 to be selectively crystallized. Performing the resolution in methanol containing 6 % water leads to (-)-2·(R,R)-3·MeOH. The other, less-soluble diastereomeric salt is obtained by applying a solvent system consisting of methanol with 19 % water with a yield of 14 %. Subsequent basic workup with aqueous sodium hydroxide gave the free menthylamine compounds. Further workup of the mother liquors and an additional recrystallization step allowed the (-)-2·(R,R)-3·MeOH salt to be obtained in an overall yield of 22 %; the other salt (+)-2·(R,R)-3·MeOH·H2O was obtained in 23 % yield. This is another important example of the dielectrically controlled resolution of an interesting amine by using inexpensive (R,R)-tartaric acid as resolving agent. With the same inexpensive resolving agent, (R,R)-tartaric acid, both antipodes of menthylamine can be selectively crystallized as diastereomeric salts. The concentration of water determines which salt is formed. In a few simple resolution steps, good yields and high enantiomeric excess can be achieved. Copyright
- Schmitt, Magdalena,Schollmeyer, Dieter,Waldvogel, Siegfried R.
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p. 1007 - 1012
(2014/03/21)
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- Synthesis of C 1-symmetric chiral secondary diamines and their applications in the asymmetric copper(II)-catalyzed Henry (Nitroaldol) reactions
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A small library of C1-symmetric chiral diamines (L1-L9) was constructed via condensing exo-(-)-bornylamine or (+)-(1S,2S,5R)-menthylamine with various Cbz-protected amino acids. Among them, ligand L1/CuCl 2?2H2O complex (2.5 mol %) shows outstanding catalytic efficiency for Henry reaction between a variety of aldehydes and nitroalkanes to afford the expected products in high yields (up to 98%) with excellent enantioselectivities (up to 99%) and moderate to good diastereoselectivities (up to 90:10). This process is air-and moisture tolerant and has been applied to the synthesis of (S)-2-amino-1-(3,4-dimethoxyphenyl) ethanol (9), a key intermediate for (S)-epinephrine and (S)-norepinephrine. On the basis of HRMS and X-ray diffraction analysis of the L1/CuCl2 complex, a transition-state model was proposed to explain the origin of asymmetric induction. The low catalyst loading, excellent yields and enantioselectivities, inexpensive copper salt, and mild reaction conditions make our catalytic system to be practically useful.
- Zhou, Yirong,Dong, Junfang,Zhang, Fanglin,Gong, Yuefa
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experimental part
p. 588 - 600
(2011/03/20)
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- Efficient and stereodivergent electrochemical synthesis of optically pure menthylamines
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The cathode directs the way to the epimeric menthylamines. The reduction of menthone oxime on a Hg cathode generates (-)-menthylamine as the major product, whereas a Pb cathode gives access to (+)-neomenthylamine (see scheme). Insitu decoration of the Pb cathode by small amounts of additives results in clean and quantitative conversions. Furthermore, Pb corrosion is completely prevented in this practical method. Copyright
- Kulisch, Joern,Nieger, Martin,Stecker, Florian,Fischer, Andreas,Waldvogel, Siegfried R.
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p. 5564 - 5567
(2011/07/30)
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- Practical synthesis of optically pure menthylamines starting from racemic neomenthol
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A reliable and scalable route to racemic and highly enantiomerically enriched menthylamines exploits the technical product rac-neomenthol as the starting material. The elaborated protocol is based on nucleophilic substitution of the hydroxy moiety by azide. Subsequent reduction and resolution with tartaric acid provides the desired optically enriched menthylamines.
- Welschoff, Nina,Waldvogel, Siegfried R.
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experimental part
p. 3596 - 3601
(2010/12/19)
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- ELECTROCHEMICAL PRODUCTION OF STERICALLY HINDERED AMINES
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The present invention relates to a process for preparing an amine, which comprises the step cathodic reduction of a corresponding oxime derivative of the general formula (I) where R is C1-6-alkyl or C2-6-alkenyl which is optionally substituted by one or more substituents selected independently from the group consisting of phenyl, O—C1-6-alkyl, NH—C1-6-alkyl, N(C1-6-alkyl)2, OH and NH2;R1 is H; C1-6-alkyl or C(O)—C1-6-alkyl and A is a 5-, 6- or 7-membered hydrocarbon ring which is saturated or has a double bond and in which at least one CH2 group may, if appropriate, be replaced by —O—, —S— —NH—, —N═ or —N(C1-6-alkyl)- and which may optionally be substituted by one or more further substituents selected independently from the group consisting of phenyl, C1-6-alkyl, O—C1-6-alkyl, NH—C1-6-alkyl, N(C1-6-alkyl)2, OH and NH2; wherein, based on the ring carbon bearing the substituent R, the oxime derivative has an excess of the R or S form of at least 10%.
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Page/Page column 4
(2009/10/18)
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- Efficient transformation of azides to primary amines using the mild and easily accessible CeCl3·;7H2O/NaI system
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(Chemical Equation Presented) Because of the nitrogen functionality, the azido group plays an important role in the synthesis of amines, and numerous reduction methods of azides to primary amines are reported. Recent reports have highlighted the capability of NaI as a useful reagent for this transformation when it is used in combination with a Lewis acid promoter. However, these methods often suffer from harsh reaction conditions; for this reason, the development of a simple and efficient protocol using NaI in presence of inexpensive and readily available cerium salts Lewis acids would extend the scope of this organic transformation. In continuation of our interest on the use of the CeCl3·7H2O/NaI system, in this paper we report how azides undergo reduction by NaI in the presence of CeCl 3·7H2O in refluxing acetonitrile under neutral conditions to produce the corresponding primary amines. The rate and yield of the reaction are considerably improved by employing this microwave-assisted procedure, and this may be of value for the preparation of densely functionalized molecules having biological and pharmaceutical activities.
- Bartoli, Giuseppe,Di Antonio, Giustino,Giovannini, Riccardo,Giuli, Sandra,Lanari, Silvia,Paoletti, Melissa,Marcantoni, Enrico
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p. 1919 - 1924
(2008/09/18)
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- Biomimetic Polyene Cyclizations. Asymmetric Induction during the Acid-Catalyzed Cyclization of Chiral Imines
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This paper reports the details of a basic study showing that an imino function is suitable to initiate acid-catalyzed cyclizations of polyenes, affording high yields of cyclized products.The additional advantage of such a function is to introduce very easily a chirality on the polyene skeleton by the way of a chiral group linked to nitrogen.The extent of asymmetric induction by a chiral phenethyl group on nitrogen is from 36percent to 65percent, according to the monocyclic or bicyclic nature of the substrate.
- Demailly, Gilles,Solladie, Guy
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p. 3102 - 3108
(2007/10/02)
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