Current Organic Synthesis - Volume 18, Issue 8, 2021

Background: Topological index is a numerical molecular descriptor that plays an important role in structure-property/structure-activity modeling. A large number of works on multiplicative degree based indices have been developed. However, no attention is paid to investigating their chemical significance. Investigation of the chemical importance of such indices is needed. The computation of topological indices for different chemical structures and networks is a current topic of interest in mathematical chemistry. Objective: The objective of the present work is to examine the usefulness of the multiplicative degree based indices in quantitative structure property/activity relationship modeling. In addition, we intend to compute the indices for some anti-COVID-19 chemicals. Materials and Methods: The regression analysis for octane data set is performed using MATLAB and Excel to check the predictability of the indices. The sensitivity test is conducted to examine the isomer discrimination ability. To study the indices for chemical structures preventing COVID-19, different combinatorial computation methods are utilized. Results and Discussion: The regression models governing the structural dependence of different properties and activities are derived. The supremacy of the indices as useful molecular descriptors compared to some well-known and most used descriptors is established. Explicit expressions of the indices for hydroxychloroquine, remdesivir (GS-5734) and theaflavin are obtained. Conclusion: As the indices are shown to have remarkable efficiency in quantitative structure property/activity relationship modeling and isomer discrimination, the outcomes can predict different properties and activities of the chemicals under consideration.

Introduction: A graph is supposed to be regular if all vertices have equal degree, otherwise irregular. Materials and Methods: Polycyclic aromatic hydrocarbons are important combusting material and considered as a class of carcinogens. These polycyclic aromatic hydrocarbons play an important role in graphitisation of medical science. A topological index is a function that assigns a numerical value to a (molecular) graph that predicts various physical, chemical, biological, thermodynamical and structural properties of (molecular) graphs. An irregular index is a topological index that measures the irregularity of atoms with respect to their bonding for the chemical compounds which are involved in the under studying graphs. Results and Discussion: In this paper, we will compute an analysis of distance based irregular indices of polycyclic aromatic hydrocarbons. A comparison among the obtained indices with the help of their numerical values and the 3D presentations is also included. The efficient and steady indices of polycyclic aromatic hydrocarbons are addressed in the form of their irregularities. Conclusion: Connection based study of the molecular graphs is more suitable than the degree based irregularity indices.

A topological descriptor is a mathematical illustration of a molecular construction that relates particular physicochemical properties of primary molecular structure as well as its mathematical depiction. Topological co-indices are usually applied for quantitative structure action relationships (QSAR) and quantitative structure property relationships (QSPR). Topological co-indices are topological descriptor which consider the noncontiguous vertex set. In this study, we studyied some of the accompanied renowned topological co-indices: the 1st and 2nd Zagreb co-indices, the 1st and 2nd multiplicative Zagreb co-indices, and the F-coindex. By applying structure based examinations and deductions, we discuss the earlier stated co-indices of few synthetic atomic structures that are frequently used in clinical, synthetic, and material designing

Azaarenes are unique scaffolds that are frequently found in pharmaceuticals. Herein we have summarized the recent synthetic available methods in C–H functionalization of methylazaarenes from 2010 to 2020. Multiple approaches involving halogenation, alkylation via different methods, alkenylation, oxidative functionalization, and cyclization of the methylazaarenes will be discussed in this review.

Nitrogen-containing heterocycles attract the attention of chemists due to their multifarious activities. Amongst all, pyrimidine plays a central role and exhibits a broad spectrum of biological activities. Literature is replete with various aspects of synthetic development in the chemistry of pyrimidine for a wide array of applications. It aroused our interest to compile various novel and efficient synthetic approaches towards the synthesis of pyrimidine and its derivatives. Pyrimidine derivatives are broadly useful as therapeutic agents, owing to their high degree of structural diversity. They have been recorded to possess a diverse range of therapeutic activities viz. anticancer, anti-inflammatory, anti-HIV etc.

β-Ketodithioesters (KDEs) are versatile building blocks for the rapid construction of various heterocyclic compounds. Quite a good number of successful reactions based on KDEs have been developed in the past decade for the construction of heterocyclic skeletons under mild conditions. This review covers the new CC/ X bond formation and annulation reactions of KDEs with dielectrophilic or dinucleophilic reagents. Multicomponent reactions using KDEs to construct various heterocycles are also the major contents in this review. Objective: The aim of this review is to bring a fresh perspective on the application of KDEs in organic synthesis covering from 2013 to 2020. Conclusion: From this review, it has been cleared that KDEs have been the object of numerous studies on its use in heterocyclic synthesis. The presence of different functional groups on this synthon permits the incorporation of C-C/X sources into the final targets, which is the significant property of KDEs.

Background: Privileged scaffolds are of high importance for molecules containing the pyrazole subunit due to their broad spectrum of pharmacological activities. For this reason, a method that is more efficient needs to be developed for the preparation of pyrazole derivatives. Objective: The purpose of this study was the optimisation of the conventional synthesis of the pyrazole ring and the oxidation of phenyl-1H-pyrazole-4-carbaldehyde to phenyl-1H-pyrazole-4-carboxylic acid through Microwave- Assisted Organic Synthesis (MAOS). Methods: We performed a comparison between conventional synthesis and conventional synthesis with microwave heating using the synthesis method of pyrazole ring described by Finar and Godfrey and for the oxidation of phenyl-1H-pyrazole-4-carbaldehyde, the method described by Shriner and Kleiderer was used. Results: MAOS reduces the reaction time to obtain all compounds compared to conventional heating. At a temperature of 60°C, 5 minutes of reaction time, and power of 50 W, the yield of phenyl-1H-pyrazoles (3a-m) compounds was in the range of 91 - 98% using MAOS, which is better than conventional heating (72 - 90%, 75ºC, 2 hours). An improvement in the yield for the oxidation reaction was also achieved with MAOS. The compounds (5a-m) were obtained with yields ranging from 62 - 92% (80ºC, 2 minutes, 150 W), while the yields with conventional heating were in the range of 48 - 85% (80ºC, 1 hour). The 26 compounds were achieved through an easy work-up procedure with no chromatographic separation. The pure products were characterised by the spectral data obtained from IR, MS, ¹H and ¹³C NMR or HSQC/HMBC techniques. Conclusion: The advantages of MAOS include short reaction time and increased yield, due to which it is an attractive option for pyrazole compounds synthesis.

Aim: The study aimed to synthesize chromeno-pyrazolo[1,2-b]phthalazine-6,9,14(7H)-trione analogs with the help of silica-supported bismuth nitrate catalyst. Background: Nitrogen-containing heterocyclic compounds are widespread, and their applications to pharmaceuticals, agrochemicals, and functional materials are becoming more and more important. Pyrazoles are an important class of compounds for new drug development, as they are the core structure of numerous biologically active compounds, including blockbuster drugs such as celecoxib, viagra, pyrazofurine, and many others. Similarly, heterocycles containing a phthalazine moiety are of current interest due to their pharmacological and biological activities; for example, pyrazolo[1,2-b]phthalazinedione is described as an anti-inflammatory, analgesic, antihypoxic, and antipyretic agent. Objective: In continuation of our ongoing investigation for the synthesis of efficient and simple approaches for the preparation of heterogeneous catalysts, herein we wish to disclose a highly efficient, simple, and one-pot synthesis of chromeno-pyrazolo-phthalazine derivatives via a one-pot multi-component reaction between 4- hydroxycoumarin, aromatic/heterocyclic aldehydes and 2,3-dihydro-1,4-phthalazinedione using silica-supported bismuth nitrate as an inexpensive, environmentally friendly and reusable catalyst under solvent-free conditions. Materials and Methods: Microanalytical data (C, H, and N) were collected on Carlo Erba analyzer model 1108. The microwave synthesis was performed in Anton Paar, Monowave 300 microwave synthesizer. Melting points were measured in open glass capillaries in the Kofler apparatus and are uncorrected. Spectroscopic data were obtained using the following instruments: Fourier transform infrared spectra (KBr discs, 4000-400 cm^-1) by Shimadzu IR-408 Perkin-Elmer 1800 instrument; ¹H NMR and ¹³C NMR spectra by Bruker Avance-II 400 MHz using DMSO-d6 as a solvent containing TMS as the internal standard. Mass spectra were set down on a JEOL D-300 mass spectrometer. Results: In continuation of our ongoing studies to synthesize heterocyclic and pharmaceutical compounds by mild, facile, and efficient protocols, herein we wish to report our experimental results of the synthesis of chromeno- pyrazolo-phthalazine derivatives under solvent-free condition derivatives, using various aromatic/heterocyclic aldehydes in the presence of silica-supported bismuth nitrate catalyst. The prepared catalyst was characterized by various physical and chemical techniques. Conclusion: We have demonstrated an efficient reaction path for the synthesis of new aryl and heteroaryl chromeno-pyrazolo[1,2-b]phthalazine-6,9,14(7H)-trione by one-pot three-component condensation of aryl/ heteroaryl aldehydes, 2,3-dihydro-1,4-phthalazinedione and 4-hydroxy coumarin using silica-supported bismuth nitrate (SSBN) under microwave irradiation. The scheme not only offers the use of microwave at low temperatures and significant yield of products but also affords mild reaction conditions, without harmful solvent, shorter reaction times, high purity, operational simplicity, and easy workup.