- Morphology-Tuned Activity of Ru/Nb2O5 Catalysts for Ketone Reductive Amination
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Amines are important compounds in natural products and medicines. Specifically, cyclopentylamine is one of the value-added chemicals widely used in the production of pesticides, cosmetics and medicines. In this work, three Ru/Nb2O5 catalysts with different Nb2O5 morphologies were used in the reductive amination of cyclopentanone under mild reaction conditions (90 °C, 2 MPa H2), among which 1 %Ru/Nb2O5?L catalyst exhibits best performance with the yield of cyclopentylamine reaching 84 %. This catalytic system is stable and has not significant deactivation even after 5 runs in the durability test. In addition, this catalyst can be extended to a series of aldehydes/ketones. Further comprehensive characterizations (XPS analysis and CO-adsorption DRIFT) reveal that the electronic effect of Ru species can be ruled out; instead, the activity of the catalyst is strongly influenced by the geometric effect. Layered Nb2O5 material possesses the highest surface area, resulting in the highest Ru dispersion, and therefore shows the highest catalytic activity. The in-situ DRIFT-MS technique was also used to reveal and understand the reaction mechanism. It is found that Ru species play a key role in activating carbonyl groups. This study illustrates a promising application of Ru/Nb2O5-Layer catalyst in the synthesis of amine and provides an understanding to the reaction mechanism.
- Guo, Wanjun,Tong, Tao,Liu, Xiaohui,Guo, Yong,Wang, Yanqin
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p. 4130 - 4138
(2019/05/24)
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- The dutch resolution variant of the classical resolution of racemates by formation of diastereomeric salts: Family behaviour in nucleation inhibition
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The resolution of racemates through their diastereomeric salts can be positively affected by the addition of small amounts of suitable nucleation inhibitors. This discovery is a logical extension of "Dutch Resolution", in which equimolar amounts of resolving agents that are members of the same family (i.e., structurally related) are used. We conducted a systematic search for nucleation inhibitors of the resolving agent 1-phenylethylamine. A wide range of amines that bear possible family resemblances to 1-phenylethylamine was investigated. It was found that (R)-1-phenylbutylamine is a good inhibitor of (R)-1-phenylethylamine. Results of turbidity measurements showed that, for the model case of mandelic acid resolution, the chief effect of this inhibitor was to widen the metastable zone for the more soluble diastereomer. This observation is in accordance with previous experience. Further scouting for possible family members revealed a wide variation in the effectiveness of inhibitors, dependent on their structure. By far the most effective inhibitors are bifunctional 1-phenylethylamine and/or 1-phenylbutylamine analogues. The effect of racemic inhibitors was found to approach that of enantiomerically pure inhibitors of the same absolute configuration of the 1-phenylethylamine used for resolution. The most effective inhibitors were tested for the resolution of a structural variety of racemates, and were shown to be broadly applicable.
- Dalmolen, Jan,Tiemersma-Wegman, Theodora D.,Nieuwenhuijzen, Jose W.,Van Der Sluis, Marcel,Van Echten, Erik,Vries, Ton R.,Kaptein, Bernard,Broxterman, Quirinius B.,Kellogg, Richard M.
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p. 5619 - 5624
(2007/10/03)
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- Stereospecific fragmentation of 3-dimethylaminocyclohexanols upon electron impact ionization
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Stereoisomeric cis- and trans-1-butyl-3-dimethylaminocyclohexanols have been previously reported to exhibit different electron impact (EI) mass spectra. The m/z 100 [C6H14N]+ ion is obtained only from the cis-isomer. The results of a collision-induced dissociation study are inconsistent with the previously proposed protonated dimethylaminocyclobutane structure (ion a) and suggest the N,N-dimethyl-1-butaneimmonium (CH3CH2CH2CH=N+(CH3)2) structure (ion b) for this ion. The mechanistic pathway proposed for this highly stereospecific process involves initial hydrogen migration from the hydroxy group to the radical site at the charged amino group as the stereospecific step, this being possible only for the cis-amino alcohol. The EI mass spectra of the corresponding stereoisomeric methyl ethers exhibit preferential elimination of formaldehyde from the cis-isomer, which is explained by initial hydrogen migration from the methoxy group to the N atom. The unsubstituted cis- and trans-1-methoxy-3-dimethylaminocyclohexanes do not show any stereospecificity in their behavior under EI.
- Vais,Mandelbaum
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p. 750 - 754
(2007/10/03)
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- Atroposelectivity in the reactions of ortholithiated aromatic tertiary amides with aldehydes
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The products of the addition of ortholithiated N,N-dialkylnaphthamides to aldehydes are pairs of stable, diastereoisomeric atropisomers, formed with selectivities of up to 90:10 in favour of the syn-atropisomer.
- Bowles, Peter,Clayden, Jonathan,Helliwell, Madeleine,McCarthy, Catherine,Tomkinson, Matthew,Westlund, Neil
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p. 2607 - 2616
(2007/10/03)
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- Very Soluble and Photostable Perylene Fluorescent Dyes
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The synthesis of perylene dyes 2 with two terminal alkyl groups is described.Long-chain alkyl groups do not increase, but diminish solubility.Cycloalkyl substituents give a minimum of solubility with medium sized rings and a maximum with the cyclotetradecyl derivative (2p).Very high solubility in organic solvents is attained by substitution with secondary alkyl residues having two long chains.One of them, the dye with the 1-hexylheptyl substituent (2v), exhibits a solubility of more than 100g/l in most solvents, a fluorescent quantum yield of about 100 percent, and a very high photostability, thus making it suitable for special applications.
- Demming, Stefan,Langhals, Heinz
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p. 225 - 230
(2007/10/02)
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- Catalyst system for amine transalkylation
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In the transalkylation of tertiary amines, unexpected higher yields are achieved requiring substantially less catalyst and much shorter reaction times at lower reaction temperatures using a homogeneous catalyst in the presence of an alcohol solvent and carbon monoxide. The process may be exemplified by reacting triethylamine and tripropylamine in the presence of a homogeneous triosmiumdodecacarbonyl catalyst, ethanol, and carbon monoxide to prepare diethylpropylamine and ethyldipropylamine.
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