Dayaker G.,CNRS Chemistry Institute of Rennes |
Tilly D.,CNRS Chemistry Institute of Rennes |
Chevallier F.,CNRS Chemistry Institute of Rennes |
Hilmersson G.,Campus Scientifique de Beaulieu |
And 3 more authors.
European Journal of Organic Chemistry | Year: 2012
Enantioselective deprotonative metalations of substituted ferrocenes using mixed lithium-metal bases are described. Using N,N- diisopropylferrocenecarboxamide as substrate, magnesium, iron, cobalt, zinc, and cadmium were tested as metals in bis[(S)-1-phenylethyl]amido-based combinations; after interception of the metalated species with iodine, very high enantiomeric excess (96%) but low yield was obtained with cobalt, whereas zinc and cadmium only gave 27 and 30 % ee, respectively, but in excellent yields. The small alkyl groups methyl and ethyl were identified as particularly suitable in the reaction using the putative dialkyl bis[(S)-1-phenylethyl]amido-based lithium and dilithium zincates. The dimethyl dilithium zincate was selected for a study of dependency on the temperature, reaction time, and amount of base. Increased enantioselectivities with temperature, reaction time, and amount of base were noted (ee = 86 % at 0 °C after 2 h, 2 equiv. of base). The best result using methyl ferrocenecarboxylate as substrate was observed without alkyl ligand. Enantioselective deprotonative metalations of N,N- diisopropylferrocenecarboxamide and methylferrocenecarboxylate using mixed lithium-metal bases are described (metal = Mg, Fe, Co, Zn, Cd). © 2012 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Labii T.,University of Mentouri Constantine |
Ceretti M.,Campus Scientifique de Beaulieu |
Boubertakh A.,University of Mentouri Constantine |
Paulus W.,Campus Scientifique de Beaulieu |
Hamamda S.,University of Mentouri Constantine
Journal of Thermal Analysis and Calorimetry | Year: 2013
CaFeO2.5±δ single crystal was obtained after different steps of mechanical and thermal treatment and finally a crystallization in an image furnace. We performed dilatometric tests of this material according to the three crystallographic directions of the network, from ambient to 1,473 K, accompanied by DSC and TG tests. The tests performed on a single crystal CaFeO2.5 confirmed the transitions already observed by other authors. For the first time, a dilatometric anomaly has been observed at 1,308 K. It has the highest intensity of all the anomalies observed and appears only along the b crystallographic direction reflecting a change of state of CaFeO2.5 at high temperature. This anomaly was confirmed using DSC and TG analysis. Moreover, this study confirmed the important dilatometric anisotropy of the material. © 2012 Akadémiai Kiadó, Budapest, Hungary.