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71.
Catalytic hydrogenation of the corresponding tetrahydrophosphinine oxides afforded the title compounds (4-6) as exclusive or major diastereomers the stereostructure and conformation of which were evaluated by stereospecific 3J couplings, as well as HF/6-31G* ab initio calculations. 相似文献
72.
Attila Makó áron Sz?ll?sy Gy?rgy Keglevich Dóra K. Menyhárd Péter Bakó László T?ke 《Monatshefte für Chemie / Chemical Monthly》2008,40(3):525-535
New chiral monoaza-15-crown-5 compounds anellated to methyl-4,6-O-(1-naphthyl)methylene-α-d-glucopyranoside (2a–2b), to methyl-4,6-O-isopropylidene-α-d-glucopyranoside (3a–3b) and to methyl-α-d-glucopyranoside (4a–4b) have been synthesized. Several representatives of these crown ethers showed significant asymmetric induction as chiral phase
transfer catalysts, among them 2a proved to be the most efficient one inducing 90% ee in the Michael addition of 2-nitropropane to chalcone, 48% ee in the Darzens condensation of phenacyl-chloride with benzaldehyde and 89% ee in the epoxidation of chalcone with tert-butyl hydroperoxide. The catalytic results were compared with those obtained earlier with macrocycles 1a–1b incorporating a 4,6-O- benzylidene protecting moiety. It occurred that the enantioselectivity is influenced to a great extent by the substituents
on the C(4) and C(6) atoms of the monosaccharide. Lower enantioselectivities were obtained in the reactions of the chalcone
analogues in the presence of catalyst 2a than in the case of the proper chalcone. 相似文献
73.
Zoltán Baán Attila Potor Agnieszka Cwik Zoltán Hell György Keglevich Zoltán Finta 《合成通讯》2013,43(10):1601-1609
A new Pd/MgLa mixed oxide and the known Pd/MgAl hydrotalcite catalysts were applied and recycled successfully in catalytic transfer hydrogenation reactions in ionic liquids. Some α,β‐unsaturated carboxylic acid derivatives were hydrogenated in excellent yields. The catalysts were recycled without significant loss of activity. Besides that, a number of halogenated aromatic compounds were dehalogenated under similar catalytic transfer conditions. 相似文献
74.
László Kollár Zsolt Csók György Keglevich 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract The synthesis of planarizcd phospholes showing considerable elcctron delocabtion haw been described.1–3 We now rcport our findings on their complex forming ability with platinum. 相似文献
75.
76.
Rita Kovcs Alajos Grün Orsolya Nmeth Sndor Garadnay Istvn Greiner Gyrgy Keglevich 《Heteroatom Chemistry》2014,25(3):186-193
The synthesis of pamidronic acid and sodium pamidronate dihydrate from β‐alanine and P‐reagents (phosphorus trichloride and phosphorous acid) was investigated at 75°C in different solvents, and the preparation was optimized. In sulfolane, the use of 2 equiv of phosphorus trichloride and phosphorous acid was found the optimum to lead to pamidronic acid in a yield of 63%. In methanesulfonic acid, 3.2 equiv of phosphorus trichloride was necessary without any phosphorous acid to give pamidronate dihydrate in the best yield (57%) after hydrolysis and pH adjustment. In the first case, the P‐nucleophile may be (HO)2P–O–PCl–O–P(OH)2 or (HO)2P–O–PCl2, whereas in the second case, the P‐reactant is probable Cl2P–O–S(O)2Me. It can be said that the mechanism proposed for the formation of pamidronic acid is highly influenced by the solvent used, as it determines the necessary P‐reagent(s). Our results promote the “on purpose” planning of the synthesis of dronates. 相似文献
77.
To further broaden the methods for the heterogeneous phase alkylation of CH acidic compounds, the dialkylation of diethyl ethoxycarbonylmethylphosphonate was studied in the presence of Cs2CO3 under microwave and solvent‐free conditions. It was found that after repeating the alkylations by the addition of newer portions of the alkylating agent and the base on a few occasions, the dialkylation was quite efficient. Even dialkyl derivatives with different alkyl groups could be synthesized. The presence of a phase‐transfer catalyst was harmful, as prevented the formation of the dialkyl products. 相似文献
78.
The phospha‐Mannich condensation of benzaldehyde, n‐propylamine, and diethyl phosphite carried out at 80°C in acetonitrile takes place via the imine (PhCN Pr) intermediate as suggested by in situ FT‐IR spectroscopy. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:599–604, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20676 相似文献
79.
It is well-known that phosphinic acids do not undergo direct esterifications with alcohols under thermal conditions. However, the esterifications take place under microwave (MW) irradiation due to the beneficial effect of MW. As a comparison, maximum 12-15% conversions were observed on traditional heating. It was proved experimentally that the MW-assisted esterifications are not reversible under the conditions applied that may be the consequence of the hydrophobic medium established by the long chain alcohol/phosphinic ester. Neither the thermodynamic, nor the kinetic data obtained by high level quantum chemical calculations justify the direct esterification of phosphinic acids under thermal conditions. The thermodynamic data show that there is no driving force for the reactions under discussion. As a consequence of the relatively high values of activation enthalpy (102-161 kJ mol(-1)), these esterifications are controlled kinetically. Comparing the energetics of the esterification of phosphinic acids and the preparative results obtained under MW conditions, one can see the potential of the MW technique in the synthesis of phosphinates. During our study, a series of new cyclic phosphinates with lipophilic alkyl groups was synthesized. 相似文献
80.
Gyrgy Keglevich Judit Dvorszki Viktria Ujj Krisztina Ludnyi 《Heteroatom Chemistry》2010,21(4):271-277
Optically active 1‐alkoxy‐ and 1‐amino‐3‐phospholene oxides were synthesized by the reaction of the corresponding 1‐chloro‐3‐phospholene oxides with (1R,2S,5R)‐(–)menthol and (S)‐(–)‐α‐phenylethylamine. The 3‐methyl‐3‐phospholene oxides were subjected to dichlorocyclopropanation under liquid–liquid phase transfer catalytic conditions to afford the 3‐phosphabicyclo[3.1.0]hexane 3‐oxides as a mixture of four diastereomers. Thermolysis of the menthyl‐phosphabicyclohexane oxides led to the corresponding 1,2‐dihydrophosphinine oxide as a diastereomeric mixture of two double‐bond isomers. As a result of additional steps, the dichlorocarbene addition reaction of the 1‐menthyl‐3,4‐dimethyl‐3‐phospholene oxide resulted in eventually, the formation of a 4‐dichloromethylene‐1,4‐dihydrophosphinine oxide. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:271–277, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20599 相似文献