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Constantinos D. Diakoumakos John A. Mikroyannidis Christoforos A. Krontiras Michael N. Pisanias 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1915-1921
New thermosetting resins were prepared from the reaction of 1,4-bis(2,2-dicyanovinyl)benzene with aromatic diamines in varying molar ratios. The thermal stability of these resins was correlated with their composition and the curing conditions. They were stable in N2 up to 370–448°C and afforded anaerobic char yields of 73–84% at 800°C after curing at 300°C for 20–60 h. The temperature dependence of the electrical resistivity of all resins pyrolyzed at 700°C for 15 h was studied in the temperature range from ?173–327°C (100–600 K). The results showed that at room temperature the unpyrolyzed polymers have insulating properties, whereas a dramatic decrease in the electrical resistivity is observed following pyrolysis. The temperature dependence of the electrical resistivity suggests that all of the materials studied have semiconducting properties. The observed electrical conductivity is thermally activated with activation energies ranging from 0.03–0.06 eV. © 1994 John Wiley & Sons, Inc. 相似文献
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Among the various Michael additions, the enantioselective reaction between cyclic ketones and nitrodienes has received little attention in comparison to the corresponding reaction with nitroolefins. A bifunctional organocatalyst consisting of the pyrrolidine moiety and a thioxotetrahydropyrimidinone ring successfully catalyzed this asymmetric transformation. The products of the reaction between various ketones and nitrodienes were obtained in high yields (up to 96%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99:1% er). 相似文献
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2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides
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Dimitris Limnios Dr. Christoforos G. Kokotos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):559-563
A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N‐oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2‐Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high‐to‐quantitative yields utilizing 10 mol % of the catalyst and H2O2 as the oxidant. 相似文献
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Kokotos CG Limnios D Triggidou D Trifonidou M Kokotos G 《Organic & biomolecular chemistry》2011,9(9):3386-3395
The synthesis of novel organocatalysts consisting of a pyrrolidine moiety and a thiohydantoin or a thioxotetrahydropyrimidinone ring is described. The compound combining the pyrrolidine with the thioxotetrahydropyrimidinone was found to be a highly effective catalyst for the Michael reaction. Low catalyst loadings (1-2.5%) can be employed leading to quantitative yields and excellent stereoselectivities in the reaction between cyclic ketones and nitroolefins. 相似文献
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One‐Pot Synthesis of O‐Allylhydroxylamines through the Organocatalytic Oxidation of Tertiary Allylic Amines Followed by a [2,3]‐Meisenheimer Rearrangement
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Alexis Theodorou Dr. Dimitris Limnios Prof. Dr. Christoforos G. Kokotos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5238-5241
A cheap, green, and highly efficient one‐pot method for the synthesis of O‐protected allylic alcohols is described. By utilizing 2,2,2‐trifluoroacetophenone as the organocatalyst and H2O2 as the oxidant, a variety of allylic amine N‐oxides were synthesized, which upon heating are converted to the final products through a [2,3]‐Meisenheimer rearrangement. 相似文献
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Panagiota Revelou Christoforos G. Kokotos Panagiota Moutevelis-Minakakis 《Tetrahedron》2012,68(42):8732-8738
Among the various versions of the aldol reaction, the enantioselective reaction between cyclic ketones and aldehydes constitutes a typical reaction model for the evaluation of novel organocatalysts. A multifunctional organocatalyst consisting of a prolinamide moiety, a gem diamine unit and a urea group was successfully employed in this asymmetric transformation. The products of the reaction between various ketones and aldehydes were obtained in high yields (up to 98%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99% ee). 相似文献
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Kokotos CG 《The Journal of organic chemistry》2012,77(2):1131-1135
A systematic study to evaluate the ability of various organocatalysts to catalyze the aldol reaction between acetone and 2,2,2-trifluoromethyl-1-phenylethanone was undertaken. Benchmark organocatalysts failed to catalyze this reaction. However, a prolinamide-thiourea consisting of (S)-prolinamide, (1S,2S)-diphenylethylenediamine, and (S)-di-tert butyl aspartate proved to be an efficient catalyst, providing tertiary alcohols as the products of the reaction between ketones and perfluoroalkyl ketones in high to quantitative yields and high enantioselectivities (up 81% ee) at a catalyst loading of 2 mol %. 相似文献
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Nikolaos F. Nikitas Mary K. Apostolopoulou Elpida Skolia Anna Tsoukaki Prof. Dr. Christoforos G. Kokotos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(29):7915-7922
A cheap, facile and metal-free photochemical protocol for the activation of aromatic aldehydes has been developed. Utilizing thioxanthen-9-one as the photocatalyst and cheap household lamps as the light source, a variety of aromatic aldehydes have been activated and subsequently converted in a one-pot reaction into amides, hydroxamic acids and esters in good to high yields. The applicability of this method was highlighted in the synthesis of Moclobemide, a drug against depression and social anxiety. Extended and detailed mechanistic studies have been conducted, in order to determine a plausible mechanism for the reaction. 相似文献
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Combining prolinamides with 2-pyrrolidinone: Novel organocatalysts for the asymmetric aldol reaction
Ismini Vlasserou Maria Sfetsa Dimitrios-Triantafyllos Gerokonstantis Christoforos G. Kokotos Panagiota Moutevelis-Minakakis 《Tetrahedron》2018,74(19):2338-2349
Peptides and especially prolinamides have been identified as excellent organocatalysts for the aldol reaction. The combination of prolinamides with derivatives bearing the 2-pyrrolidinone scaffold, deriving from pyroglutamic acid, led to the identification of novel organocatalysts for the intermolecular asymmetric aldol reaction. The new hybrids were tested both in organic and aqueous media. Among the compounds tested, 22 afforded the best results in petroleum ether, while 25 afforded the products in brine in high yields and selectivities. Then, various ketones and aldehydes were utilized and the products of the aldol reaction were obtained in high yields (up to 100%) with excellent diastereo- (up to 97:3 dr) and enantioselectivities (up to 99% ee). 相似文献