Browsing by Author "Malakar, Chandi C."

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A cascade A3 coupling strategy towards the regioselective synthesis of ?-carboline N-fused pyrrole derivatives with pyridine tethers
(Royal Society of Chemistry, 2022-12-01T00:00:00) Vaishali, None; Malakar, Chandi C.; Singh, Virender
A potential three component reaction strategy has been devised to generate nature inspired ?-carboline N-fused pyrroles containing pyridine tethers. These scaffolds were afforded in high yields via a one-pot cascade regioselective reaction of diverse Kumujian C, 2-aminopyridines and alkyne derivatives under Cu(ii)-catalysis. A library of 32 novel indolizino[8,7-b]indole derivatives with pyridine tethers has been developed. The current protocol offers excellent regioselectivity, high atom-economy and significant structural diversity. � 2023 The Royal Society of Chemistry.
Copper catalysed regioselective synthesis of pyrimidine substituted Indolizino[8,7-b]indole derivatives via cascade A3 annulation
(Elsevier Ltd, 2023-07-08T00:00:00) Kumar, Sunit; Kumar, Rakesh; Malakar, Chandi C.; Singh, Virender
Cu(II) salt has been found to be an efficient catalyst for the regioselective synthesis of a series of novel indolizino [8,7-b]indole derivatives with pyrimidine tethers via three-component annulation of 1-formyl-9H-?-carbolines (Kumujian C), 2-amino-pyrimidines and terminal alkynes. The reactions proceeds through Cu-catalysed A3-coupling followed by intramolecular cyclisation in a cascade manner. The scope of strategy has been exemplified with a library of biologically interesting 25 indolizino [8,7-b]indoles with pyrimidine tethers which mimics several natural products. � 2023 Elsevier Ltd
Copper-Catalyzed C(sp3)? Functionalization and Annulation of 2-Bromoaryl Oximes with Active Methylene Compounds towards Synthesis of Isoquinoline N-Oxides
(John Wiley and Sons Inc, 2023-06-09T00:00:00) Patel, Chandresh K.; Gujjarappa, Raghuram; Kant, Kamal; Ghanta, Susanta; Singh, Virender; Kabi, Arup K.; Al-Zaqri, Nabil; Malakar, Chandi C.
The established process proceeds through copper (II)-catalyzed C(sp3)? functionalization of ?-diketones/?-ketoesters with 2-bromobenzaldehyde oximes followed by the intramolecular cyclization of in situ generated acylated intermediates to deliver isoquinoline N-oxides. The copper(II) acetate catalyzed C?H functionalization showed maximum efficacy at 60 �C in methanol/toluene as solvent. The described reaction conditions were applicable over a wide range of substrates with a variety of functional groups to yield isoquinoline N-oxides in yields up to 85%. The developed approach was further elucidated by means of control experiments and DFT calculations. � 2023 Wiley-VCH GmbH.
Cu(II)-Catalysed Azide-Alkyne Cycloaddition Reaction towards Synthesis of ?-Carboline C1-Tethered 1,2,3-Triazole Derivatives
(John Wiley and Sons Inc, 2021-04-27T00:00:00) Kumar, Sunit; Malakar, Chandi C.; Singh, Virender
Indole and ?-carboline alkaloids exhibit diverse range of significant pharmacological properties as reflected by their contribution in drug-discovery. We have described the synthesis of hybrid molecules containing ?-carboline C1-linked 1,2,3-triazoles in moderate to good yields. The developed transformation was realized by using Cu(II)-catalysed click-reaction of diverse alkynes with in-situ derived rarely explored ?-carboline tethered aliphatic azides. These molecular hybrids also exhibited excellent fluorescence properties. � 2021 Wiley-VCH GmbH
DABCO Mediated Sulfur Activation-Intramolecular De-Nitration Strategy for the Synthesis of Novel Dihydrothiochromeno[4,3-c]pyrazoles
(John Wiley and Sons Inc, 2023-07-24T00:00:00) Deepika; Paul, Avijit K.; Malakar, Chandi C.; Bansal, Ajay; Singh, Virender
A facile and highly efficient metal-free approach has been unfolded for the synthesis of novel dihydrothiochromeno[4,3-c]pyrazoles using elemental sulfur as a powerful sulfurating reagent. This method includes sp2 C?H functionalization followed by sp2 C?NO2 group displacement using elemental sulfur as an odourless sulfur source activated by DABCO in DMSO. Using the developed synthetic strategy, a library of 29 novel dihydrothiochromeno[4,3-c]pyrazoles, incorporating two pharmacologically important scaffolds has been synthesized in 52�76% yield with a broad substrate scope. A sensible mechanistic proposal has been projected based on control experiments. � 2023 Wiley-VCH GmbH.
Efficient approach towards the polysubstituted 4h-pyran hybrid quinolone derivatives and subsequent copper-catalyzed hydroxylation of haloarenes
(Japan Institute of Heterocyclic Chemistry, 2021-03-16T00:00:00) Kumar, Vipin; Singh, Dharmender; Gujjarappa, Raghuram; Malakar, Chandi C.; Singh, Virender
A proficient and feasible approach towards polysubstituted quinolone conjugated 4H-pyrans has been elucidated. The illustrated phenomenon concern with the base-mediated multicomponent reaction and subsequent copper-catalyzed hydroxylation of C-X bond emerging in an amide functionality. The developed reaction conditions showcased considerable substrate scope and functional group tolerance by giving the desired products in good yields. � 2021 Japan Institute of Heterocyclic Chemistry. All rights reserved.
An efficient metal-free and catalyst-free C�S/C�O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides
(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2023-03-02T00:00:00) Sharma, Shubham; Singh, Dharmender; Kumar, Sunit; Vaishali; Jamra, Rahul; Banyal, Naveen; Deepika; Malakar, Chandi C.; Singh, Virender
An operationally simple and metal-free approach is described for the synthesis of pyrazole-tethered thioamide and amide conjugates. The thioamides were generated by employing a three-component reaction of diverse pyrazole C-3/4/5 carbaldehydes, secondary amines, and elemental sulfur in a single synthetic operation. The advantages of this developed protocol refer to the broad substrate scope, metal-free and easy to perform reaction conditions. Moreover, the pyrazole C-3/5-linked amide conjugates were also synthesized via an oxidative amination of pyrazole carbaldehydes and 2-aminopyridines using hydrogen peroxide as an oxidant. � 2023 Sharma et al.
KI-assisted Sulfur Activation/Insertion/Denitration Strategy towards Dual C?S Bond Formation for One-pot Synthesis of ?-Carboline-tethered 2-Acylbenzothiophenes
(John Wiley and Sons Inc, 2021-12-13T00:00:00) Singh, Manpreet; Jamra., Rahul; Paul, Avijit K.; Malakar, Chandi C.; Singh, Virender
A simple and efficient KI promoted sulfur activation-insertion/de-nitration strategy has been developed for the synthesis of ?-carboline C1 tethered 2-acylbenzothiophenes via one-pot assembly of 1-acetyl ?-carbolines (an alkaloid based scaffold), 2-nirobenzaldehydes and elemental sulfur. This expeditious reaction proceeds through the formation of ?-carboline linked nitro-chalcones followed by embodiment of elemental sulfur to generate the multifunctional ?-carboline linked benzothiophene derivatives. The highlighted features of this efficient methodology are transition metal-free conditions, use of inexpensive and non-toxic catalyst, easy procedure, short reaction time, and broad substrate scope with good yields. The scope of this protocol has been extended for the synthesis of a range of novel compounds with significant diversity. � 2021 Wiley-VCH GmbH
Metal- and Hazardous Reagent-Free Transamidation Process: the NH2OH?HCl Promoted N-Formylation and N-Acylation Reaction under Solvent-Less Conditions
(Taylor and Francis Ltd., 2023-09-14T00:00:00) Devi, Elangbam Pinky; Kant, Kamal; Kaldhi, Dhananjaya; Ghanta, Susanta; Sengupta, Ragini; Al-Zaqri, Nabil; Singh, Virender; Malakar, Chandi C.
An efficient transamidation process has been described under solvent-less conditions. The transformation has been accomplished by employing NH2OH?HCl as a reagent and amines as substrates. The developed method is achieved in the absence of metals and hazardous reagents. A series of amines were explored to obtain the N-formylation and N-acylation reactions with excellent yields (81-96%) of products. The DFT analysis was also performed, which provides a clear understanding of the described N-formylation process. The postulated mechanism is well supported by the control experiments. � 2023 Taylor & Francis Group, LLC.
An Overview on Biological Activities of 1,2,3-Triazole Derivatives
(Springer Nature, 2022-03-07T00:00:00) Kabi, Arup K.; Sravani, Sattu; Gujjarappa, Raghuram; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Among the nitrogen-embedded heterocycles, 1,2,3-triazoles derivatives are widely explored and earned considerable attraction in pharmaceutical industry and academics. 1,2,3-Triazoles have attracted significant consideration during the last few years due to widespread implementation in synthetic organic chemistry, drug discovery process, supramolecular chemistry, chemical biology, polymer chemistry, fluorescent imaging as well as materials chemistry. Even though absent in nature, these N-heterocycles have a wide spectrum of medicinal applications against several malignant cells, microorganisms, viruses and their preclusive actions are resistant to various enzymes. Moreover, 1,2,3-triazoles-based scaffolds have been extensively immersed as a linker and a functional moiety, mainly owing to the fact that their processing simplicity, orthogonality development and attractive �Click� properties. This chapter highlights the recent developments on diversified biological efficiencies of 1,2,3-triazoles and their approach in the progress of novel bioactive as well as pharmacoactive entities in future. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Overview on Biological Activities of Imidazole Derivatives
(Springer Nature, 2022-03-07T00:00:00) Gujjarappa, Raghuram; Kabi, Arup K.; Sravani, Sattu; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Velayutham, Ravichandiran; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Imidazole and its derivatives are one of the most important and widely used heterocycles in medicinal chemistry, natural products, and synthetic chemicals. Because of the imidazole ring's unique structural features, imidazole derivatives may easily attach to a wide range of enzymes and receptors via a number of weak interactions, demonstrating a wide range of biological and pharmacological effects. Several imidazole derivatives have been widely used in the clinic to treat a wide range of illnesses, suggesting their enormous potential for further research. In the realm of medicinal chemistry, this chapter presents a comprehensive summary of current findings in imidazole derivatives as anti-inflammatory, anticancer, antiviral, antibacterial, and other therapeutic agents. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
An Overview on Biological Activities of Oxazole, Isoxazoles and 1,2,4-Oxadiazoles Derivatives
(Springer Nature, 2022-03-07T00:00:00) Gujjarappa, Raghuram; Sravani, Sattu; Kabi, Arup K.; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Heterocyclic compounds containing the oxazole, isoxazole and oxadiazoles rings have received significant consideration as they perform like a link between life sciences and chemical sciences. In the past few years, the efficacy of these heterocyclic nuclei as synthetic intermediates for the development of novel chemical entities in medicinal and pharmaceutical chemistry has enhanced worldwide. Moreover, the importance of N-heterocycles from a medicinal point of view is due to their readily binding ability with biological systems such as various enzymes and receptors via numerous non-covalent interactions. Globally, similar research of finding Oxazole-based derivatives as potent medicinal drug candidates is an active topic which includes; oxazoles, isoxazoles, oxadiazoles, benzoxazoles, oxazolines, oxazolidinones, etc., in the study. Prominently, plenty of oxazole-based molecular scaffolds as active pharmacophores have been used against various diseases, which has shown their importance for the development as potential pharmaceutical agents. This chapter thoroughly highlights the current developments and researches involving; oxazole, isoxazole and oxadiazole-based compounds as clinical candidates, including anticancer, antibacterial, antiviral, antifungal, anti-inflammatory and antitubercular, antidiabetic as well as other biological activities. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Overview on Biological Activities of Pyrazole Derivatives
(Springer Nature, 2022-03-07T00:00:00) Kabi, Arup K.; Sravani, Sattu; Gujjarappa, Raghuram; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Pyrazoles are appraised as medicinally significant heterocyclic nuclei that exhibit a widespread spectrum of biological properties. The existence of pyrazole derivatives as pharmacophore in distinct remedial divisions like the antipsychotic CDPPB, an effective anti-inflammatory, celecoxib; difenamizole, an analgesic, rimonabant; the anti-obesity drug, the antidepressant agent fezolamide and betazole, a H2-receptor agonist have ascertained medicinal potentiality of this scaffold. In this regard, pyrazole, one of the most powerful pharmacophores, has been an important topic of research for the scientist around the globe. This chapter draws special attention to the various pharmacological and biological potentiality as well several studies on the pharmacological potency of pyrazole scaffolds emerged by various research groups all over the world are described. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
An Overview on Biological Activity of Benzimidazole Derivatives
(Springer Nature, 2022-03-07T00:00:00) Kabi, Arup K.; Sravani, Sattu; Gujjarappa, Raghuram; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Benzimidazole moiety plays a key role in variety of heterocyclic scaffolds which derive the biological functioning of essential molecules. Because of the skeletal resemblance with the naturally appearing nucleotides, benzimidazole and its analogues exhibited numerous medicinal and pharmacological performances. They are appraised as the auspicious class of bioactive molecules which endorse diverse actions like antiprotozoal, antimicrobial, antimalarial, anti-helminthic, anti-inflammatory, anti-mycobacterial, antiviral, and antiparasitic. Moreover, benzimidazole has recognized paramount responses in current years and is an enormously important pharmacophoric heterocyclic moieties in recent drug innovations and medicinal chemistry. This chapter will be beneficial for the researchers working in the fields of medicinal chemistry in visualizing the diverse pharmacological activities of benzimidazole derivatives in developing a SAR on benzimidazole drugs. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
An Overview on Biological Evaluation of Tetrazole Derivatives
(Springer Nature, 2022-03-07T00:00:00) Kabi, Arup K.; Sravani, Sattu; Gujjarappa, Raghuram; Garg, Aakriti; Vodnala, Nagaraju; Tyagi, Ujjawal; Kaldhi, Dhananjaya; Velayutham, Ravichandiran; Singh, Virender; Gupta, Sreya; Malakar, Chandi C.
Tetrazoles are distinguished by a five-membered, doubly unsaturated ring which consists of four nitrogen and one carbon atom with a molecular formula CN4H2, which have a wide range of medicinal activity and potential role in biosciences. Interest in tetrazole chemistry in recent decades has been increasing rapidly because of diverse biological and pharmaceutical applications, mostly due to the diversity of this N-heterocyclic moiety in medicinal chemistry. This moiety offers a more appreciative pharmacokinetic profile and plays the role of metabolically stable substitute for carboxylic acid functional group as well as exhibits a broad range of biological effects such as analgesic, antibacterial, anticancer, anti-inflammatory, antidiabetic, antifungal, antitubercular and antihyperlipidemic activities. This chapter highlights the unique features of the potential possible role of tetrazole derivatives and summarizes biological and pharmacological activities. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
P(III)-Mediated Cascade C-N/C-S Bond Formation: A Protocol towards the Synthesis of N,S-Heterocycles and Spiro Compounds
(Wiley-VCH Verlag, 2020-11-20T00:00:00) Polina, Saibabu; Putta, V. P. Rama Kishore; Gujjarappa, Raghuram; Singh, Virender; Pujar, Prasad Pralhad; Malakar, Chandi C.
A P(III)-mediated entry towards construction of C?N/C?S bond has been devised. The developed heterocyclization method was exercised for the synthesis of a diverse range of N,S-heterocycles and related spiro molecules. P(NMe2)3 revealed the maximum efficacies under the aerobic reaction conditions and a spectrum of bis-nucleophiles, and isothiocyanates were tolerated well to serve the access of manifold immense molecules. (Figure presented.). � 2020 Wiley-VCH GmbH
Potassium tert-Butoxide-Mediated Synthesis of 2-Aminoquinolines from Alkylnitriles and 2-Aminobenzaldehyde Derivatives
(John Wiley and Sons Inc, 2022-12-08T00:00:00) Kishore, Pendyala Satya; Gujjarappa, Raghuram; Putta, V. P. Rama Kishore; Polina, Saibabu; Singh, Virender; Malakar, Chandi C.; Pujar, Prasad Pralhad
KOtBu mediates the reaction between 2-amino arylcarbaldehydes and benzyl/alkyl cyanides toward the expeditious formation of 2-aminoquinolines under transition-metal-free conditions. The described transformation proceeds through in-situ generated enimine intermediate from benzyl/alkyl cyanides under KOtBu-mediated reaction conditions. The substituted 2-aminoquinolines were realized in excellent yields at room temperature and shorter reaction time. The designed process exhibits operational simplicity and broad functional group tolerance in delivering the products of high significance. � 2022 Wiley-VCH GmbH.
Synthesis and Characterization of Novel Pd@rGO?CuFe2O4 Magnetic Nanoparticles: A Recyclable Catalyst for C?C Coupling Reaction in Biomass-Derived Organic Solvent
(John Wiley and Sons Inc, 2023-10-06T00:00:00) Teli, Yaqoob A.; Reetu, Reetu; Singh, Priyanka Gurdev; Patel, Mayur Jagdishbhai; Dash, Sonali; Paine, Snehangshu; Prabhakar, Poornachandra Shamanna; Singh, Virender; Keremane, Kavya S.; Al-Zaqri, Nabil; Mukherjee, Kalisadhan; Dutta, Saikat; Malakar, Chandi C.
Development of new, cost effective, stable heterogeneous catalyst for the organic transformations is an important thematic area of research. Present work describes the development of new Pd@rGO?CuFe2O4 catalyst and demonstrates its effectiveness for Suzuki-Miyaura type coupling reactions. The additional advantage of this reaction is its feasibility using biomass-derived solvent like ?-Valerolactone (GVL) in aqueous media. The catalyst is prepared hydrothermally and characterized using XRD, FESEM, EDX, and XPS analysis. The catalyst exhibits excellent activity and recyclability (up to six times) in the C?C coupling reaction to deliver the corresponding biaryl molecules in yields up to 90 %. High efficiency for the conversion of nitriles to amides is also revealed by the prepared catalyst. � 2023 Wiley-VCH GmbH.
Synthesis of pyrazolo[4,3-c]quinolines and the C-C bond cleavage during reductive cyclization
(Japan Institute of Heterocyclic Chemistry, 2021-02-26T00:00:00) Devi, Nisha; Gupta, Antriksh; Gujjarappa, Raghuram; Malakar, Chandi C.; Singh, Virender
An efficient synthesis of o-nitrophenyl tethered pyrazole-4-carbaldehydes was achieved via Vilsmeier-Haack formylation of hydrazone derivatives which were subjected to Claisen-Schmidt condensation and Morita-Baylis-Hillman (MBH) reaction with various methyl ketones and activated alkenes respectively to generate the corresponding chalcones and MBH adducts. However, successive Fe-mediated reductive cyclization was followed by an unusual C-C bond cleavage which afforded the pyrazolo[4,3-c]quinolines devoid of diverse substituents at C-4 position. � 2021 The Japan Institute of Heterocyclic Chemistry.
Transition-Metal-Free Cascade C-N Bond Formation: An Effective Strategy for the Synthesis of ?-Carboline N-Fused Imidazolium Acetates and Estimation of their Light-Emitting Properties
(Georg Thieme Verlag, 2023-08-08T00:00:00) Singh, Manpreet; Vaishali, Vaishali; Deepika, Deepika; Jyoti, Jyoti; Sharma, Shubham; Banyal, Naveen; Kumar, Prashant; Budhalakoti, Bharti; Malakar, Chandi C.; Singh, Virender
A simple, efficient, and practical metal-free protocol has been devised to synthesize imidazopyrido[3,4-b]indole-based fluorophores decorated with carbazole/ F-carboline/pyridine scaffolds via three consecutive C.N bond formations in a single operation. A wide range of aromatic amines (2-aminopyridines, 3-aminocarbazole, and anilines) were successfully applied to synthesize the complex imidazolium ions. The significant features of this strategy include high efficiency, mild and environmentally benign reaction conditions, no chromatographic purification, and broad substrate scope with excellent yields of the isolated products. Moreover, excellent photophysical properties (up to 85%) were exhibited by these fluorophores. � 2022 Georg Thieme Verlag. All rights reserved.