Current Organocatalysis - Volume 6, Issue 3, 2019

An up-to-date short review of the chalcone methodologies is presented, which is the most interesting and beneficial for choosing the desired protocol to synthesize suitable derivatives of chalcones. Chalcones are fluorescent, stable compounds which contribute to the synthesis of various pharmacologically important heterocyclic structure-based derivatives. Chalcone has displayed a remarkable curative efficiency to cure several diseases. Several schemes and methodologies have been reported for employing different catalysts and reagents. The development of improved methodologies of α, β-unsaturated carbonyl compounds is still on going. In this review, synthetic methodologies and their recent modification in designing new methods with efficient, economical, eco-friendly and high yield are discussed.

‘Polysilanes’ is an important class of inorganic polymers having Si-Si σ-conjugation along the backbone. They exhibit extraordinary electronic and photophysical properties and find suitable optoelectronics applications. They are typically synthesized by Wurtz coupling reaction of dichlorodialkylsilane or dichlorodiphenylsilane or dichloroalkylphenylsilane and their combinations under drastic reaction conditions by using sodium dispersion in boiling toluene. In such a drastic condition, no functional groups sustain with polysilane polymer. In order to achieve such functional materials, researchers have been interested in synthesizing functional polysilane with a different functional group like a chiral group, azobenzene containing chromophore and other heteroatoms in their main chain or side chain. Therefore, it is a very challenging task to synthesize polysilanes having effective functionality integrated with their structures. However, the modern technological demand of materials leads to efforts to obtain polymers having functional and multifunctional activity in a single material. In this review article, we cover the synthesis of polysilane with functional activity via pre-polymerization and post-polymerization with a functional group.

Background: In recent years, photoredox catalysis using eosin Y has gained considerable significance in organic chemistry. It is evolving as a powerful approach in modern organic synthesis for the activation of small molecules. Objective: The use of organic dyes to convert visible light into chemical energy by involving a single-electron transfer with organic substrates has innumerable applications. Method and Results: The present strategy is the first example of visible light promoted, aerobic, oxidative cyclization of chromeno[4,3-b]chromenes and hexahydro-1H-xanthenes via the formation of C–O and C–C bonds to afford excellent yield of the products in a simple one-pot operation under mild reaction conditions. Conclusion: The major advantages of the present methodology include short reaction time, cost effectiveness, easy work-up, broad substrate scope and high atom economy.

Background: Multicomponent reactions involve the simultaneous reaction of three or more components which deliver the product that incorporates the elements of all starting materials. A combination of multicomponent reaction and green solvents like water and the use of nonconventional energy sources like microwave or ultrasonication are important features of ideal green synthesis. Therefore, the design of a new multicomponent reaction and improvement of an already known multicomponent reaction with a green procedure has attracted the attention of the scientific community. Isoxazole derivatives are well known for their biological activities such as antifungal, analgesic, antitumor, antioxidant, antimicrobial, COX-2 inhibitory, anti-inflammatory, antiviral, and antimycobacterial. Objective: To develop a green methodology for the synthesis of 4H-isoxazol-5-ones derivatives. Result: Itaconic acid was used as a green catalyst for the synthesis of 4H-isoxazol-5-ones derivatives under conventional as well as ultrasound irradiation technique. Ultrasound irradiation condition requires less time for the completion of the reaction and also the yields were better. Methods: We have reported Itaconic acid as a green homogenous organocatalyst under ultrasound irradiation for the synthesis of 4H-isoxazol-5-ones derivatives. Conclusion: In conclusion, we have developed a green methodology for the synthesis of 4Hisoxazol- 5-ones derivatives. Itaconic acid is used as an organocatalyst which is biodegradable and nonhazardous. Water is used as a green solvent. Ultrasonication is used as a non-conventional green energy source. Ambient reaction conditions are used to carry out transformation for multicomponent reaction. Metal-free, mineral acid-free synthesis are key features of the present protocol.

Background: In recent years, green organic transformation has become a challenge for a chemist in areas like social sector, health, and environment. Literature survey revealed that a nano magnetite supported heterogeneous catalysis is an emergent field with huge application in chemical synthesis. Objective: In the present article, the aim was to develop a simple and facile method to carry organic reaction under benign media. So, the focus was on the synthesis of nano-magnetite supported molybdenum catalyst and its application in β-enaminones synthesis. Methods: Magnetically recyclable heterogeneous ferrite-molybdenum catalyst was prepared by simple impregnation method. The synthesized nanocatalyst Fe-Mo was well analysed by spectroscopic techniques like X-ray diffraction analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, field-emission gun scanning electron microscopy and vibrating-sample magnetometry. The functionalized nanocatalyst Fe-Mo was employed in the synthesis of β-enaminones under solvent free condition. Results: The competency of synthesized nanocatalyst-Fe-Mo was observed to be good for the synthesis of β-enaminones derivatives under microwave irradiation and gave excellent yield (86-96%) of the product. The catalyst was recycled for more than five consecutive runs without significant loss in its activity. Conclusion: In the present research article, synthesis of highly active, magnetically recyclable Fe- Mo nanocatalyst was obtained from easily available precursor. The MNP was stable under investigated conditions and effective in β-enaminones synthesis. The simple eco-friendly method, low catalyst loading, short transformation time, and reusability of the catalyst thoroughly follow the sustainable protocol.

Background: Dihydropyrano [3, 2-c]chromenes and their derivatives have great attention for scientists. They have different activities such as biological properties, spasmolytic, diuretic, anticoagulant, anti-cancer, and anti-anaphylactic activity. For these vary biological activities, chromene derivatives have made significant for further progress in medicinal and organic synthesis studies. So, in view of the importance of chromenes, we aimed to synthesis of 3, 4-dihydropyrano [3, 2-c] chromene derivatives. ZIF@ZnTiO3nanocomposite as organocatalyst was used. Results: An effective and applicable technique was used for preparation of 3, 4-dihydropyrano [3, 2- c] chromene derivatives. Dihydropyrano [c] chromenederivatives were prepared by using ZIF@ZnTiO3compositeas a recyclable catalyst. One-pot three-component reaction of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin was done for synthesis of dihydropyrano [c] chromenederivatives over composite catalyst with excellent yields. The as prepared dihydropyrano [c] chromenederivatives were measured by melting point, FTIR, 1H NMR, and 13C NMR. The nano catalyst could be recycled several times. Methods: A novel nano catalyst of MOF containing Mn2+ ions and 2- methyl imidazole (ZIF) and zinctitanate (ZIF@ZnTiO3) composite was prepared. The synthesized organocatalyst was studied for preparation of 3, 4-dihydropyrano [3, 2-c] chromene derivatives. One-pot three-component reaction of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin was done for synthesis of dihydropyrano [c] chromene derivatives over composite catalyst with excellent yields. The reaction was optimized. Conclusion: The organocatalyst composite of consist of ZIF and zinctitanate was prepared. The ZIF@ZnTiO3 was used as catalyst for synthesis of 3, 4-dihydropyrano [3, 2-c] chromene derivatives via one-pot three-component condensations of aromatic aldehydes,malononitrile, and 4 hydroxycoumarin. The results of melting point, FTIR, 1H NMR, 13C NMR also confirmed the formation of high yield of 3, 4-dihydropyrano [3, 2-c] chromene derivatives at short time. The appealing properties of this method are environmentally friendly, mild reaction conditions (low reaction time and high yields of pure products), easy work up and recyclability of reaction catalyst.

Background: Synthesis of acridinedione derivatives via one-pot multi-component approaches using highly active and reusable Pd/AlO(OH) heterogenous catalyst was studied. This process provided a convenient method to obtain various acridinediones with potential biological activities. The reactions were performed in mild conditions such as low temperature and short reaction time with desirable yields. Methods: Commercially available Pd/AlO(OH) nanoparticles characterized by XRD and SEM methods were afforded for the synthesis of acridinedione derivatives with high yields. Crude products were analyzed by GC and 1H NMR. The reactions were completed within 1h at 40°C by the assistance of ultrasound system. Results: Optimization of reaction conditions is of critical case for successful synthesis. Solvent, temperature, time and amount of catalyst were studied. At the end of the experiments, the synthesis of 1 mmol of acridinedione was optimized by using 25 mg of Pd/AlO(OH) NPs, 3 ml of DMF for 60 min at 40°C in the ultrasound system. An experimental work to check the reusability of the catalyst was also studied. Pd/Al(O)OH catalyst in the first run was higher than that of the reused catalyst in the fifth run. ICP-OES analyses showed palladium leaching into the reaction medium was only 1.1% which is negligible. Nanocatalyst employed a high activity and good reusability. Conclusion: A convenient and versatile method was developed for the synthesis of acridinediones in a mild condition with absolute conversion and high yield using ultrasound system in the presence of nanocatalyst.