- Photoinduced and Thermal Isomerization Processes for Bis-Oxonols: Rotor Volume, Stereochemical and Viscosity Effects
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Four bis-oxonols have been synthesized which possess different alkyl substituents appended to the thiobarbiturate subunit.The nature of the alkyl substituent affects the photophysical properties of the dye in solution since it modulates the rate of rotation of the thiobarbiturate subunit around one of the double bonds in the connecting trimethine bridge.Rates of light-induced (trans to cis) and thermal (cis to trans) isomerization processes have been measured for one of the dyes in protic (i.e. alkanols) and aprotic solvents at various temperatures.These rates, together with activation energies derived from Arrhenius plots, are discussed in terms of the hydrogen bonding and stereochemical properties of the solvent.The thermal step is very sensitive to the stereochemistry of the solvent while the light-induced process is controlled mostly by the size of the rotor and the solvent viscosity.The overall effects may be explained, at least in a qualitative sense, in terms of the medium-enhanced barrier model.
- Benniston, Andrew C.,Harriman, Anthony
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- Rapid and highly efficient synthesis of thioureas in biocompatible basic choline hydroxide
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A straightforward and convenient synthesis of symmetrical thiourea derivatives by the reaction of primary amines and carbon disulfide in biocompatible basic choline hydroxide is presented. A variety of biologically important thiourea derivatives can be obtained in good to excellent yields without a tedious work-up under mild reaction conditions. A series of primary aliphatic and aromatic amines with different substituted functional groups have been converted to thiourea derivatives under milder reaction conditions and short reaction times.
- Azizi, Najmedin,Farhadi, Elham
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p. 548 - 554
(2017/09/27)
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- A highly efficient one-pot method for the synthesis of thioureas and 2-imino-4-thiazolidinones under microwave conditions
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A one-pot synthesis of symmetrical and unsymmetrical substituted thioureas and 2-imino-4-thiazolidinones from simple starting materials under microwave irradiation and solventless conditions without base additives is presented. Various di- and trisubstituted thioureas are obtained in good yields in a few minutes. The sequential, three-component, one-pot synthesis of 2-imino-4-thiazolidinone derivatives is also studied, with satisfactory results obtained.
- Chau, Chi-Min,Chuan, Tzu-Jung,Liu, Kuan-Miao
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p. 1276 - 1282
(2014/01/06)
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- A simple route for the synthesis of symmetrical thiourea derivatives and amidinium cations by reaction between isocyanides, amines and carbon disulfide
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Reaction between primary amines and CS2 promoted by alkyl isocyanides in ethanol as solvent provides a simple and efficient route for the synthesis of symmetrical thiourea derivatives. The reaction of secondary amines with carbon disulfide and alkyl isocyanides afforded new amidinium cations in good yields.
- Anary-Abbasinejad, Mohammad,Karimi, Nadia,Mehrabi, Hossein,Ranjbar-Karimi, Reza
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p. 653 - 659
(2013/02/22)
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- A concise synthesis of substituted thiourea derivatives in aqueous medium
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(Figure Presented) An efficient method for the synthesis of symmetrical and unsymmetrical substituted thiourea derivatives by means of simple condensation between available building blocks such as amines and carbon disulfide in aqueous medium is presented. This protocol works smoothly with aliphatic primary amines to afford various di- and trisubstituted thiourea derivatives. The present method is also useful in synthesizing various substituted 2-mercapto imidazole heterocycles. This method proceeds through a xanthate (amino dithiol deivative) intermediate, unlike isothiocyanate as in an earlier known method.
- Maddani, Mahagundappa R.,Prabhu, Kandikere R.
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supporting information; experimental part
p. 2327 - 2332
(2010/07/02)
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- Anion-templated assembly of pseudorotaxanes: Importance of anion template, strength of ion-pair thread association, and macrocycle ring size
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A wide range of pseudorotaxane assemblies containing positively charged pyridinium, pyridinium nicotinamide, imidazolium, benzimidazolium and guanidinium threading components, and macrocyclic isophthalamide polyether ligands have been prepared using a general anion templation procedure. In noncompetitive solvent media, coupling halide anion recognition by a macrocyclic ligand with ion-pairing between the halide anion and a strongly associated cation provides the driving force for interpenetration. Extensive solution 1H NMR binding studies, thermodynamic investigations, and single-crystal X-ray structure determinations reveal that the nature of the halide anion template, strength of the ion-pairing between the anion template and the cationic threading component, and to a lesser extent favorable second sphere π-π aromatic stacking interactions between the positively charged threading component and macrocyclic ligand, together with macrocyclic ring size, affect the efficacy of pseudorotaxane formation.
- Sambrook, Mark R.,Beer, Paul D.,Wisner, James A.,Paul, Rowena L.,Cowley, Andrew R.,Szemes, Fridrich,Drew, Michael G. B.
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p. 2292 - 2302
(2007/10/03)
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