- Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage
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A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished.
- Fujita, Ken-Ichi,Wada, Tomokatsu,Shiraishi, Takumi
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supporting information
p. 10886 - 10889
(2017/08/30)
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- Iridium-catalyzed condensation of amines and vicinal diols to substituted piperazines
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A straightforward procedure is described for the synthesis of piperazines from amines and 1,2-diols. The heterocyclization is catalyzed by [Cp*IrCl2]2 and sodium hydrogen carbonate and can be achieved with either toluene or water as solvent. The transformation does not require any stoichiometric additives and only produces water as the byproduct. The reaction can be performed between a 1,2-diamine and a 1,2-diol or by a double condensation between a primary alkylamine and a 1,2-diol. At least one substituent is required on the piperazine ring to achieve the cyclization in good yield. The mechanism is believed to involve dehydrogenation of the 1,2-diol to the α-hydroxy aldehyde, which condenses with the amine to form the α-hydroxy imine. The latter rearranges to the corresponding α-amino carbonyl compound, which then reacts with another amine followed by reduction of the resulting imine. Piperazines are prepared by [Cp*IrCl 2]2-catalyzed heterocyclization of 1,2-diols with either 1,2-diamines or primary alkylamines. The reaction is performed in toluene or water and requires no stoichiometric additive. The key step in the mechanism is believed to be the isomerization of an α-hydroxy imine to the corresponding α-amino carbonyl compound. Copyright
- Lorentz-Petersen, Linda L. R.,Nordstrom, Lars Ulrik,Madsen, Robert
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p. 6752 - 6759
(2013/01/15)
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- Electromagnetic actuator
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An electromagnetic actuator comprising a fixed magnetic pole (11) applied with an electromagnetic coil (14), and a movable magnetic pole (20) provided in the insertion hole (12) of the fixed magnetic pole movably in the axial direction. The movable magnetic pole is provided with a projecting portion (22) tapered along its moving direction, a recessed taper portion (13) corresponding to the projecting taper portion of the movable magnetic pole is formed at the insertion hole of the fixed magnetic pole, and a tubular auxiliary magnetic pole (40) extending in the axial direction from the opening end of the recessed taper portion is provided continuously to the fixed magnetic pole.
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- Enantioconvergent synthesis of (-)-(2R,5S)-1-allyl-2,5-dimethylpiperazine, an intermediate to δ-opioid receptor ligands
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A convenient, high-yield enantioconvergent synthesis of (-)-1-allyl-(2S,5R)-dimethylpiperazine from trans-2,5-dimethylpiperazine has been developed. This compound is an important intermediate in the synthesis of Δ-opioid receptor ligands. The process allows for the laboratory preparation of 100 g quantities of this enantiomerically pure diamine without chromatography. The key steps in the sequence were an efficient optical resolution using relatively inexpensive resolving agents, followed by interconversion of the unwanted (+)-enantiomer into the desired (-)-enantiomer.
- Janetka, James W.,Furness, M. Scott,Zhang, Xiaoyan,Coop, Andrew,Folk, John E.,Mattson, Mariena V.,Jacobson, Arthur E.,Rice, Kenner C.
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p. 3976 - 3980
(2007/10/03)
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- Process for preparing Cis-2,6-dimethylpiperazine
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This invention relates to a process for the selective preparation of cis-2,6-dimethylpiperazine by reacting (i) a diisopropanolamine mixture comprising compounds having the formulas HN(CH2CH(OH)CH3)2, HN(CH(CH3)CH2OH)2, and HN(CH(CH3)CH2OH)(CH2CH(OH)CH3) or (ii) 1,2-diaminopropane with ammonia and hydrogen in the presence of a hydrogenation catalyst.
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- Reduction of Heterocycles with Nickel-Aluminum Alloy
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Pyrazines, pyridazines, isoxazoles, oxazole, 4-methylpyrimidine, and indole are reduced by nickel-aluminum alloy in potassium hydroxide solution.The reaction is simple to carry out and does not require special apparatus or hydrogen atmospheres.The products were the fully hydrogenated species although benzene rings were not attacked. 4-Methylpyrimidine gave 1,3-diaminobutane and oxazole gave 2-(methylamino)ethanol.It was found that the reaction frequently exhibited an induction period.
- Lunn, George
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p. 1043 - 1046
(2007/10/02)
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