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321.
The synthesis and liquid crystalline properties of novel achiral amides (Ia–g, IIa–g and IVa,b), achiral Schiff's bases (IIIa–g and Va–g), chiral amides (VI, VII) and chiral Schiff's bases (VIII–XI) incorporating a 1,3,4-oxadiazole ring are reported. All amides of the series I and II display an enantiotropic smectic A phase. The amide IVa,b did not show mesomorphic properties. Amides of the series Ia–g and IIa–g contain a flexible n-tetradecylthio chain, the other terminal substituent is an n-alkoxy chain and n-alkyl chain, respectively (n?=?4–10) and the 1,3,4-oxadiazole is in the terminal rigid core. Amides Ia–g have broader mesomorphic range and higher thermal stability than the corresponding amides IIa–g. Amides IVa,d contain the 1,3,4-oxadiazole ring in the centre of the rigid core and two flexible alkoxy chains as flexible terminal substituents. Thus, the mesomorphic properties are favoured if 1,3,4-oxadiazole is shifted to a terminal position of the rigid core. Schiff's bases IIIa–g display an enantiotropic dimorphism smectic C–smectic A. Schiff's bases IIIa–g have a broader mesomorphic range than the analogous amides Ia–g. Schiff's bases Va–g exhibit a dimorphism smectic A–nematic, and in contrast to this the analogous amide IVa,b did not show mesomorphism. The chiral amides VI and VII and chiral Schiff's bases X and XI did not show mesomorphic properties and only the chiral Schiff's bases VIII and IX display a chiral smectic C phase in a short mesomorphic range. A density functional theory theoretical study at the B3LYP/6–311++G(d,p) level was performed in order to analyse the structural features that must be related with the mesomorphic behaviour of the reported compounds. 相似文献
322.
Augusto Rivera Juan Francisco León Jasmin Rivera Eva Cecilia Parra Jindra Purmova Eleuterio Burgueño-Tapia 《合成通讯》2013,43(11):2029-2040
A one-step synthesis of 2t-substituted-1r,3c-bis(2′-hydroxy-5′- substituted-benzyl)-imidazolidines from 1,3-bis(2′-hydroxy-5′-substituted-benzyl)-imidazolidines and aromatic aldehydes is reported. The relative stereochemistry of the five-membered ring was evident from 1H NMR measurements combined with MMX calculations. 相似文献
323.
Regioselective reaction of lithium diene-and triene-diolates 1 and 2 with O-diphenylphosphinyl hydroxylamine affords unsaturated α-amino acids 3 and 4. Addition to DEAD leads selectively to γ-hydrazino unsaturated acids 5 and 6. 相似文献
324.
A Boron Dipyrromethene (BODIPY)‐Based CuII–Bipyridine Complex for Highly Selective NO Detection 下载免费PDF全文
L. Alberto Juárez Dr. Andrea Barba‐Bon Prof. Ana M. Costero Prof. Ramón Martínez‐Máñez Dr. Félix Sancenón Prof. Margarita Parra Dr. Pablo Gaviña Dr. M. Carmen Terencio Prof. M. José Alcaraz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15486-15490
A BODIPY‐containing CuII–bipyridine complex for the simple selective fluorogenic detection of NO in air and in live cells is reported. The detection mechanism is based on NO‐promoted CuII to CuI reduction, followed by demetallation of the complex, which results in the clearly enhanced emission of the boron dipyrromethene (BODIPY) unit. 相似文献
325.
Eva Sánchez Moulay L. Hbid Rafael Bravo de la Parra 《Journal of Evolution Equations》2014,14(3):603-616
In this paper, we propose a model for the dynamics of a physiologically structured population of individuals whose life cycle is divided into two stages: the first stage is structured by the weight, while the second one is structured by the age, the exit from the first stage occurring when a threshold weight is attained. The model originates in a complex one dealing with a fish population and covers a large class of situations encompassing two-stage life histories with a different structuring variable for each state, one of its key features being that the maturation process is determined in terms of a weight threshold to be reached by individuals in the first stage. Mathematically, the model is based on the classical Lotka–MacKendrick linear model, which is reduced to a delayed renewal equation including a constant delay that can be viewed as the time spent by individuals in the first stage to reach the weight threshold. The influence of the growth rate and the maturation threshold on the long-term behavior of solutions is analyzed using Laplace transform methods. 相似文献
326.
Blends of poly (3-hydroxybutyrate) (PHB) with poly (ethylene glycol) (PEG), (PHB/PEG), in different proportions of 100/0, 98/2, 95/5, 90/10, 80/20 and 60/40 wt%, respectively, were investigated for their thermal properties (using differential scanning calorimetry and thermogravimetric analysis), tensile properties, water vapor transmission rate, enzymatic biodegradation (using light microscopy) and mass retention. The addition of plasticizer did not alter the thermal stability of the blends, although an increase in the PEG content reduced the tensile strength and increased the elongation at break of pure PHB. 相似文献