- Synthesis of piperazine-1,4-dipropanoic acid Di(1,2,2,6,6-pentamethyl-4-piperidine)yl ester as a photostabilizer
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A new type hindered amine light stabilizer (HALS) has been synthesized. The derivatives of piperazine and piperidine have been combined via the transesterification reaction. Effects of such variables as molar ratio, catalyst dosage, reaction time, and temperature were studied and optimized. The structures of all products were elucidated by FT-IR spectroscopy and NMR spectrometry.
- Xiao, Feng,Zhou, Yuanlin,Yang, Wenbin
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- Vanadyl(IV) acetate: An efficient, reusable heterogenous catalyst for Aza-Michael reaction under solvent-free conditions
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Vanadyl(IV) acetate [VO(OAc)2] efficiently catalyzes the conjugate addition of aliphatic, aromatic amines to α,β-unsaturated carbonyl compounds in solvent-free media at room temperature to afford corresponding amino compounds in good to excellent yields. The catalyst can be recovered and reused for further cycles. Copyright Taylor & Francis Group, LLC.
- Trivedi, Rajiv,Lalitha,Roy, Sarabindu
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p. 3556 - 3566
(2008/12/23)
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- Silicon carbide passive heating elements in microwave-assisted organic synthesis
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Microwave-assisted organic synthesis in nonpolar solvents is investigated utilizing cylinders of sintered silicon carbide (SiC)-a chemically inert and strongly microwave absorbing material-as passive heating elements (PHEs). These heating inserts absorb microwave energy and subsequently transfer the generated thermal energy via conduction phenomena to the reaction mixture. The use of passive heating elements allows otherwise microwave transparent or poorly absorbing solvents such as hexane, carbon tetrachloride, tetrahydrofuran, dioxane, or toluene to be effectively heated to temperatures far above their boiling points (200-250 °C) under sealed vessel microwave conditions. This opens up the possibility to perform microwave synthesis in unpolar solvent environments as demonstrated successfully for several organic transformations, such as Claisen rearrangements, Diels-Alder reactions, Michael additions, N-alkylations, and Dimroth rearrangements. This noninvasive technique is a particularly valuable tool in cases where other options to increase the microwave absorbance of the reaction medium, such as the addition of ionic liquids as heating aids, are not feasible due to an incompatibility of the ionic liquid with a particular substrate. The SiC heating elements are thermally and chemically resistant to 1500 °C and compatible with any solvent or reagent.
- Kremsner, Jennifer M.,Kappe, C. Oliver
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p. 4651 - 4658
(2007/10/03)
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- Cellulose-supported copper(0) catalyst for aza-Michael addition
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Cellulose-supported copper(0) efficiently catalyzes the aza-Michael reaction of N-nucleophiles, such as amines and imidazoles with α,β-unsaturated compounds to produce the corresponding β-amino compounds and N-substituted imidazoles in excellent yields. The reactions are facile and the recovered catalyst is used for several cycles with consistent activity. Georg Thieme Verlag Stuttgart.
- Reddy, K. Rajender,Kumar, Nadakudity S.
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p. 2246 - 2250
(2007/10/03)
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- Cu(acac)2 immobilized in ionic liquids: A recoverable and reusable catalytic system for aza-Michael reactions
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Copper(II) acetylacetonate immobilized in ionic liquids efficiently catalyzes the aza-Michael reaction of amines with α,β-unsaturated carbonyl compounds to produce the corresponding β-amino carbonyl compounds with great alacrity in excellent yields. The reactions are far more facile than those reported earlier. The recovered ionic liquid phase containing the copper catalyst can be reused for several cycles with consistent activity.
- Kantam, M. Lakshmi,Neeraja,Kavita,Neelima,Chaudhuri, Mihir K.,Hussain, Sahid
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p. 763 - 766
(2007/10/03)
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- Chemoselective Michael type addition of aliphatic amines to α,β-ethylenic compounds using bismuth triflate catalyst
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Catalytic amounts of bismuth triflate efficiently catalyse the conjugate addition of aliphatic amines to α,β-ethylenic compounds in acetonitrile under mild conditions. The reaction is chemoselective, as aromatic amines do not participate in the reaction. Further, the catalyst can be easily recovered and reused.
- Varala, Ravi,Alam, M. Mujahid,Adapa, Srinivas R.
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p. 720 - 722
(2007/10/03)
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