A new catalytic method for the denitrogenative transannulation/cyclopropanation of in‐situ‐generated 2‐(diazomethyl)pyridines is described using a cobalt‐catalyzed radical‐activation mechanism. The ...method takes advantage of the inherent properties of a CoIII‐carbene radical intermediate and is the first report of denitrogenative transannulation/cyclopropanation by a radical‐activation mechanism, which is supported by various control experiments. The synthetic benefits of the metalloradical approach are showcased with a short total synthesis of (±)‐monomorine.
Denitrogenative transannulation/cyclopropanation of in‐situ‐generated 2‐(diazomethyl)pyridine is presented, which involves a cobalt‐catalyzed radical‐activation mechanism. A cobalt(II)‐metalloradical undergoes radical addition to alkynes during denitrogenative transannulation, or to alkenes during cyclopropanation, forming indolizines and cyclopropanes, respectively
A concept for intramolecular denitrogenative C(sp3)–H amination of 1,2,3,4-tetrazoles bearing unactivated primary, secondary, and tertiary C–H bonds is discovered. This catalytic amination follows ...an unprecedented metalloradical activation mechanism. The utility of the method is showcased with the short synthesis of a bioactive molecule. Moreover, an initial effort has been embarked on for the enantioselective C(sp3)–H amination through the catalyst design. Collectively, this study underlines the development of C(sp3)–H bond functionalization chemistry that should find wide application in the context of drug discovery and natural product synthesis.
An efficient strategy for the intramolecular denitrogenative transannulation/C(sp2)–H amination of 1,2,3,4-tetrazoles bearing C8-substituted arenes, heteroarenes, and alkenes is described. The ...process involves the generation of the metal–nitrene intermediate from tetrazole by the combination of Cp*IrCl22 and AgSbF6. It has been shown that the reaction proceeds via an unprecedented electrocyclization process. The method has been successfully applied for the synthesis of a diverse array of α-carbolines and 7-azaindoles.
•Cover in depth survey on sensor, feature, score and decision level fusion in multibiometrics.•In sensor level fusion several works are pointed out based on multi-sample, multi-sensor and ...multi-modal.•In feature level fusion several works are pointed out based on multi-algorithm and multi-modal.•In score level fusion several works are pointed out based on multi-algorithm and multi-modal.•In decision level fusion several works are pointed out based on multi-algorithm and multi-modal.
The unimodal biometric based system faced several inherent problems like lack of uniqueness, intra-class variation, non-universality, noisy data (presence of dirt on the sensor), restricted degree of freedom, unacceptable error rate, failure-to-enroll and spoofing attack. Multibiometric is one of the best choices to overcome these problems. Multibiometric fusion plays an important role to enhance the overall performance of the system, in which two or more individual biometric are combined together to form a better performance system. The proper use of fusion strategy is very important in the multibiometric system because it can affect the overall performance and accuracy level of the systems. In designing a multibiometric based system we can use various methods and fusion strategies to combine information from multiple sources. This paper is an in-depth study on multibiometric (multimodal, multialgorithm, multi-sample, multi-sensor and multi-instance) fusion strategy and its different applications. In addition, this paper also discusses the different methodology used in a fusion process (Sensor, Feature, Score, Decision, Rank) of multibiometric systems from last three decades and examines the methods used, to explore their successes and failure.
A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the ...traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.
1,2,3,4: A unique intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by employing a catalytic amount of Fe(TPP)Cl and Zn dust. This reaction precludes the traditional click reaction between organic azides and alkynes.
A general catalytic method using a Mn‐porphyrin‐based catalytic system is reported that enables two different reactions (click reaction and denitrogenative annulation) and affords two different ...classes of nitrogen heterocycles, 1,5‐disubstituted 1,2,3‐triazoles (with a pyridyl motif) and 1,2,4‐triazolo‐pyridines. Mechanistic investigations suggest that although the click reaction likely proceeds through an ionic mechanism, which is different from the traditional click reaction, the denitrogenative annulation reaction likely proceeds via an electrophilic metallonitrene intermediate rather than a metalloradical intermediate. Collectively, this method is highly efficient and offers several advantages over other methods. For example, this method excludes a multi‐step synthesis of the N‐heterocyclic molecules described and produces only environmentally benign N2 gas a by‐product.
A Mn‐porphyrin‐based catalytic method that enables access to two different classes of nitrogen heterocycles is reported. Mechanistic investigations found that a 1,3‐cycloaddition click reaction occurs directly via the Mn‐bound complex, whereas denitrogenative annulation proceeds through an Mn‐N complex. The reported method is compatible with a wide range of substrates for both reactions.
A catalytic system for intermolecular benzylic C(sp3)–H amination is developed utilizing 1,2,3,4-tetrazole as a nitrene precursor via iron catalysis. This method enables direct installation of ...2-aminopyridine into the benzylic and heterobenzylic position. The method selectively aminates 2° benzylic C(sp3)–H bond over the 3° and 1° benzylic C(sp3)–H bonds. Experimental studies reveal that the C(sp3)–H amination undergoes via the formation of a benzylic radical intermediate. This study reports the discovery of new method for 2-pyridine substituted benzylamine synthesis using inexpensive, biocompatible base metal catalysis that should have wide application in the context of medicinal chemistry and drug discovery.
Rubia cordifolia L. is a widely used traditional medicine in the Indian sub-continent and Eastern Asia. In the present study, the aqueous leaf extract of the R. Cordifolia was used to fabricate ...silver nanoparticles (RC@AgNPs), following a green synthesis approach. Effect of temperature (60 °C), pH (8), as well the concentration of leaf extract (2 ml) and silver nitrate (2 mM) were optimized for the synthesis of stable RC@AgNPs. The phytofabrication of nanosilver was validated by UV-visible spectral analysis, which displayed a distinctive surface plasmon resonance peak at 432 nm. The effective functional molecules as capping and stabilizing agents, and responsible for the conversion of Ag
to nanosilver (Ag
) were identified using the FTIR spectra. The spherical RC@AgNPs with an average size of ~ 20.98 nm, crystalline nature, and 61% elemental composition were revealed by TEM, SEM, XRD, and. EDX. Biogenic RC@AgNPs displayed a remarkable anticancer activity against B16F10 (melanoma) and A431 (carcinoma) cell lines with respective IC
of 36.63 and 54.09 µg/mL, respectively. Besides, RC@AgNPs showed strong antifungal activity against aflatoxigenic Aspergillus flavus, DNA-binding properties, and DPPH and ABTS free radical inhibition. The presented research provides a potential therapeutic agent to be utilized in various biomedical applications.
Composite materials are emerging as a vital entity for the sustainable development of both humans and the environment. Polylactic acid (PLA) has been recognized as a potential polymer candidate with ...attractive characteristics for applications in both the engineering and medical sectors. Hence, the present article throws lights on the essential physical and mechanical properties of PLA that can be beneficial for the development of composites, biocomposites, films, porous gels, and so on. The article discusses various processes that can be utilized in the fabrication of PLA-based composites. In a later section, we have a detailed discourse on the various composites and nanocomposites-based PLA along with the properties’ comparisons, discussing our investigation on the effects of various fibers, fillers, and nanofillers on the mechanical, thermal, and wear properties of PLA. Lastly, the various applications in which PLA is used extensively are discussed in detail.
