Current Organic Chemistry - Volume 21, Issue 11, 2017

Coumarin derivatives play an important role in many different biomedical and technological applications. As “privileged” scaffolds, coumarin derivatives display interesting biological and important optoelectronic properties. The practical significance of coumarin molecules has encouraged extensive efforts toward their synthesis. Although classical methods, such as the Perkin, Pechmann and Knoevenagel reactions for the synthesis of a wide variety of substituted coumarins, are still actively used, these methods suffer several limitations. Nowadays, alternative new efficient syntheses of coumarin derivatives are constantly evolving and being of considerable interest. The hydroarylation reaction of alkynes, using transition metals catalysts, is considered one of the most prospective tools for rapid accessing to coumarin scaffolds in an efficient and atom-economical manner. This coumarin construction could be achieved through inter- or intramolecular reactions of respective phenols and alkynes or aryl alkynoates. The present review mainly covers recent studies on new methods for the synthesis of coumarin derivatives via alkenylation of phenols with alkynes, aryl alkynoates and related reagents or direct functionalization of alkynoates. The information provided should furnish a fresh insight for organic chemists in the design of novel molecules that contain the coumarin skeletons.

This review deals with the synthesis of unnatural and natural 2(5H)-furanone derivatives featuring bromine atoms on the heterocyclic ring and/or brominated substituents, which have been described in the literature since 1951 up to February 2016. The review has been organized on the basis of six classes of brominated furanone derivatives that were synthesized: i) 2(5H)-furanone derivatives with one bromine atom on the heterocyclic ring; ii) 2(5H)-furanone derivatives with two bromine atoms on the heterocyclic ring; iii) 2(5H)-furanone derivatives featuring one bromine atom on the heterocyclic ring and monobrominated substituents; iv) 2(5H)- furanone derivatives featuring one bromine atom on the heterocyclic ring and dibrominated substituents; v) 2(5H)-furanone derivatives with monobrominated substituents; and vi) 2(5H)-furanones featuring dibrominated substituents. Where possible, experimental details of the syntheses have been reported. Furthermore, the biological properties of the target compounds, including their mutagenic, cytotoxic, enzymatic, anti-inflammatory and photosynthetic inhibitory activities have been summarized, paying particular attention on the compounds that have demonstrated antimicrobial properties via inhibition of quorum sensing and biofilm formation.

To meet the increasingly stringent fuel emission regulations, deep desulfurization of fuel oil is becoming a hot issue in the field of catalysis. However, the requirement of ultra-low sulfur diesel fuel production can hardly be fulfilled economically by conventional hydrodesulfurization. This is because some aromatic sulfurcontaining compounds, especially the thiophene compounds, cannot be removed effectively by the conventional method. In view of this, many new alternative desulfurization methods have been developed in recent years. Among these new methods, the oxidative desulfurization is regarded as the most promising one, since it can highly effectively remove the thiophene compounds such as benzothiophene, dibenzothiophene, and 4,6- dimethyldibenzothiophene, which is difficult to be reduced by hydrodesulfurization. Furthermore, the oxidative desulfurization can be carried out under mild conditions, making it more applicable industrially. In the oxidative desulfurization of fuel oil, the thiophene compounds are oxidized to their corresponding sulfoxides or sulfones by the suitable oxidants (H2O2, organic peroxide acid, O2, and air), and the sulfoxides or sulfones will subsequently be removed by adsorption or extraction. The oxidation of thiophene compounds is a key step in the whole process and the organic oxidation reaction is identified to occur in the presence of appropriate catalysts. Therefore, the catalysts play an important role in the oxidative desulfurization. In this review, recent advances in new catalysts for oxidative desulfurization of fuel oil will be addressed, with an emphasis on the innovative and functional materials used to catalyze the process.

Background: Nanomaterials based on porphyrin has attracted attention for significant research due to their potential applications in diverse fields such as optoelectronic devices, catalysis, light harvesting devices, controlled-release drug delivery. The self assembly method is an effective protocol for the fabrication of nanomaterials. Objective: We synthesised an unsymmetrical porphyrin 5,10-bis(4-hydroxyphenyl)-15,20-bis(4-pyridyl) porphyrin, decorated with hydroxyl and pyridyl functional group which assist in supramolecular self assembly. Method: We used two different methods, surfactant assisted method and vaporization-condensationrecrystallization method for the self assembly of our new unsymmetrical porphyrin bearing hydrogen bonding motifs. The nanoaggregates obtained by these two different methods were well characterized by different spectroscopic techniques such as UV-visible spectra, fluorescence emission spectroscopy, scanning electron microscopy and X-ray diffraction. Results: A new unsymmetrical porphyrin was synthesized and used for the formation of different nanoaggregates. The surfactant assisted method results in fabrication of nanoboats while VCR method leads to the formation of well ordered nanospindles. Both the nanoboats and nanospindles were formed by virtue of the cooperation of the non-covalent interactions such as hydrogen bonding and ππ interactions. Conclusion: The vaporization-condensation-recrystallization method forms highly crystalline nanospindles as it induces re-crystallization based self-assemblies using externally provided thermal energy, and avoids the need for solvent molecules while surfactant assisted method requires the solvent as well external stabilizer.