Current Organic Synthesis - Volume 17, Issue 8, 2020

In recent years, hybrid systems are gaining considerable attention owing to their various biological applications in drug development. Generally, hybrid molecules are constructed from different molecular entities to generate a new functional molecule with improved biological activities. There already exist a large number of naturally occurring hybrid molecules based on both non-steroid and steroid frameworks synthesized by nature through mixed biosynthetic pathways such as, a) integration of the different biosynthetic pathways or b) Carbon- Carbon bond formation between different components derived through different biosynthetic pathways. Multicomponent reactions are a great way to generate efficient libraries of hybrid compounds with high diversity. Throughout the scientific history, the most common factors developing technologies are less energy consumption and avoiding the use of hazardous reagents. In this case, microwave energy plays a vital role in chemical transformations since it involves two very essential criteria of synthesis, minimizing energy consumption required for heating and time required for the reaction. This review summarizes the use of microwave energy in the synthesis of steroidal and non-steroidal hybrid molecules and the use of multicomponent reactions.

Rose Oxide is a monoterpene along with cyclic ether used in fragrance to produce rosy notes, in general, there are 4 stereoisomeric structures of the Rose Oxide, which the cis-configured Rose Oxide has a very unique and strong note in perfumery. In this review, several approaches were reported on account of the Rose Oxide applied in perfumery from 1864 to 2019 via quantitative and qualitative approaches.

Polycyclic aromatic hydrocarbons (PAHs) are aromatic compounds with two or more fused benzene rings in their structural configurations. PAHs do not contain heteroatoms and substituents on the ring system. PAHs containing up to four rings are called light PAHs while those that contain more than four rings are considered as heavy PAHs. Heavy PAHs are more stable and more toxic than the light PAHs. Generally, the increase in the size and angularity of a PAH molecule results in an increase in hydrophobicity and electrochemical stability. Ring linkage patterns in PAHs may occur in such a way that the tertiary carbon atoms are centers of two or three interlinked rings. The examples of PAHs are naphthalene, anthracene, phenanthrene, acenaphthylene, acenaphthene, fluorene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, etc. PAHs can be produced either naturally or anthropogenically and have toxic properties. Due to the health risk posed by their exposure, there is a need to control the release of PAHs through air quality management. Refinery industries are required to monitor and regulate their discharges. There is an urgent need for the considerable efforts to be applied in the field of research to degrade and monitor potentially hazardous substances to control, predict and avoid negative effects of PAHs pollution.

Background: Aza-steroids are an important class of compounds because of their numerous biological activities. The hetero steroids have different hydrogen bonding ability and hydrophobicity in comparison to steroids. Materials and Methods: Microwave-induced synthesis of a novel type of hybrid hetero-steroid amine conjugates, following Ugi-four component reactions of steroidal amines with alanine and valine methyl esters as amino acid residues is described. Specifically, hetero-steroid-amino acid conjugate based on D-ring fused hetero steroidal amine, hetero-steroid-amino acid conjugate based on A-ring hetero steroidal amine, and hetero-steroidamino acid conjugate based on B-ring hetero steroidal amine are synthesized. Results and Discussion: The yield of the products under microwave-induced process was considerably higher than that obtained by the conventional method. In contrast to the conventional method for the synthesis of these molecules, microwave-induced method has several advantages. Conclusion: These include rapid reaction, a superior yield of the product, minimum side reaction, and economical microwave-induced process.

Aims: synthesis of pyrano[c-2,3]chromens with Ionic Liquid catalyst with simple method. Background: Synthesis of pyrano[c]coumarins has a special place in the structure due to two bioactive compounds in its structure and attracts a great deal of attention in this research work, it has been attempted to attach chromatically valuable skeletons to them and synthesize the pyrano [c] coumarines, which can potentially have high biological properties. For this purpose, electrophilic β-ketoester ringing in the presence of ionic liquid catalysts was used. While optimizing the catalyst recovery, it is possible to synthesize several coumarine pyrano[ c]derivatives with high yield. Objective: This paper describes an efficient procedure for the multi-component reaction of aromatic aldehydes, 4,4,4-Trifluoro-1-phenyl-1,3-butanedione and 4-hydroxycoumarinwhich catalyzed by Ioniq liquid (OlmDSA), at room temperature. This catalyst was synthesized with new simple procedure. This protocol has advantages of simplicity, mild condition and high yield. Materials and Methods: After formation of a new stain corresponding to the alkene intermediate, 4-hydroxy coumarin (1 mM) was added. The reaction was progressed by thin layer chromatography in a 1: 2 ratio solvent containing ethyl acetate and hexane. The reaction mixture was then stirred for one hour. After the reaction was complete, the catalyst was first removed by washing. Ethanol was then added to the reaction residue and washed and finally filtered. The residual solid on the filter paper after drying was considered as the product and was taken to confirm. its structure, melting point and spectra. The following is a general overview of the reaction. Results and Discussion: In addition to the advantages mentioned for this tri-component reaction, the conservation of the coumarin ring is very important in this research design because it is formed in many of the reported open reactions and phenolic ring. Conclusion: The benefits of this work include simple reaction steps, review of reaction progress by TLC chromatography, simple separation of the catalyst by washing and reuse for three times without any reduction in yield and high reaction yield.

Introduction: We developed a simple, fast and new method for the Fries rearrangement of aryl esters. Materials and Methods: 4-Hydroxy pyridinium triflate functionalized silica is a very efficient, reusable and economically available catalyst for the Fries rearrangement in solvent-free condition and under microwave irradiation. Results and Discussion: Also, a notable selectivity was observed in the presence of 4-hydroxy pyridinium triflate functionalized silica. Conclusion: Selectivity, shorter reaction time, high yield, and easy work-up are advantages of this synthetic method.

Aim and Objective: According to the literature survey, pyrazole is a unique template that is associated with several biological activities. This article highlighted the research work of many researchers reported in the literature for synthesis and different pharmacological activities of the pyrazole nucleus. In the present work, pyrazol- 3-one 1 was reacted with cyanoacetic acid hydrazide and elemental sulfur to afford the corresponding thieno[3,2-c]pyrazol-6-carbohydrazide 3 derivatives. The latter compound reacted with some electrophilic reagents such as DMF-DMA, triethylorthoformate, arylidenemalononitriles and chalcones under neat conditions to give substituted oxadiazole and pyrazole, respectively. The treatment of compound 3 with active methylene reagents such as acetylacetone, diethylmalonate, ethyl acetoacetate and ethyl cyanoacetate under suitable conditions afforded pyrazole derivatives 10, 11, 13, and 15, respectively. Novel pyrazolothienopyrimidine 27 and 30 were prepared from precursor 26 with carbon disulfide and triethylorthoformate, respectively. The chemical structures of the newly synthesized compounds were established by elemental and spectral analyses including IR, and 1HNMR in addition to 13C-NMR and mass spectra. Materials and Methods: A novel substituted pyrazole, pyrimidine and pyrazolothienopyrimidine were obtained via Gewald synthesis of thiophene and fused thiophene and Mannich reactions of 5-amino-3-phenyl-1Hthieno[ 3,2-c]pyrazole-6-carbohydrazide. Results and Discussion: A series of some newly azoles and azines were prepared via reaction of thieno[3,2- c]pyrazol-6-carbohydrazide derivative 3 as starting material with some electrophilic and nucleophilic reagents. The structures of target compounds were established by elemental analyses and spectral data. Conclusion: Pyrazole is a unique template that is associated with several biological activities. This article highlighted the research work of many researchers reported in the literature for synthesis and different pharmacological activities of the pyrazole nucleus. In the current investigation, we have developed new and efficient methods for the synthesis of thieno[3,2-c]pyrazol-6-carbohydrazide derivatives. In addition, we have explored the preparative potential of these substances as intermediates for the synthesis of substituted pyrazoles and fused pyrazoles 10-30, respectively.

Aim and objective: Isoxazole is an active core found in many drugs. The aim of this work was to synthesize bis-isoxazoline compounds and to analyze the effect of linker chain length on biological activities. Material and Methods: A simple, convenient, and efficient method for the conversion of bischalcones to new bis(4,5-dihydroisoxazole) derivatives was developed by using hydroxylamine hydrochloride under basic medium. Synthesized moieties were also evaluated for their antimicrobial potencies and DNA photocleavage assay. Results and Discussion: The synthesized compounds were more active than their chalcone precursors and the long-chain linkers (4e&4f) were more potent in antimicrobial, as well as in DNA photocleavage activity. Conclusion: It was found that many of the tested bischalcones and bis-isoxazolines exhibited moderate to significant antimicrobial activity against various strains. Furthermore, the present study also provides significant information and interesting outcomes regarding cyclization, increasing the length of linker chains, and their effects on the DNA photocleavage and antimicrobial activities.

Thiamine hydrochloride is reported to be a highly competent promoter for the synthesis of bis(indolyl)methanes under solvent free conditions using microwave irradiation and ultrasonicator heating in aqueous media. Vitamin B1 is an economical, non-toxic, nonflammable and water soluble green organocatalyst. Moreover, the simple approach, easily operational, short reaction time, high yield and using a little quantity of thiamine hydrochloride makes this method an alternative approach. Present protocol is a simple and eco-friendly approach for the synthesis of bis(indolyl)methanes under microwave and ultrasonicator conditions.

A novel process for the preparation of acetone is reported by gas-phase oxidation of propylene in the presence of H2 and O2 with Au supported TS-1 catalyst (Au/TS-1). By elevating the reaction temperature to 280 oC, Au/TS-1 catalyzes 11.6% propylene generating acetone with 70.6% selectivity, and 8.2% acetone in onepass yield. Acetone is originated from propylene oxide isomerization, which is mainly attributed to the surface of the Lewis base and high reaction temperature. Furthermore, small Au nanoparticle size promotes the reaction.