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.
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.
Abstract To date, degraded mangrove ecosystem restoration accomplished worldwide primarily aligns towards rehabilitation with monotypic plantations, while ecological restoration principles are rarely ...followed in these interventions. However, researchers admit that most of these initiatives' success rate is not appreciable often. An integrative framework of ecological restoration for degraded mangroves where site-specific observations could be scientifically rationalized, with co-located reference pristine mangroves as the target ecosystem to achieve is currently distinctively lacking. Through this experimental scale study, we studied the suitability of site-specific strategies to ecologically restore degraded mangrove patches vis-à-vis the conventional mono-species plantations in a highly vulnerable mangrove ecosystem in Indian Sundarbans. This comprehensive restoration framework was trialed in small discrete degraded mangrove patches spanning ~ 65 ha. Site-specific key restoration components applied are statistically validated through RDA analyses and Bayesian t-tests. 25 quantifiable metrics evaluate the restoration success of a ~ 3 ha degraded mangrove patch with Ridgeline distribution, Kolmogorov–Smirnov (K-S) tests, and Mahalanobis Distance (D 2 ) measure to prove the site’s near-equivalence to pristine reference in multiple ecosystem attributes. This restoration intervention irrevocably establishes the greater potential of this framework in the recovery of ecosystem functions and self-sustenance compared to that of predominant monoculture practices for vulnerable mangroves.
Controlling sickle cell disease: The need of the hour Kumar, Ravindra; Chandraker, Sandip Kumar; Das, Aparup
Clinical epidemiology and global health,
May-June 2023, 2023-05-00, 2023-05-01, Letnik:
21
Journal Article
The present work deals with the study of chemical synthesis of tetrabutylammonium hexanitrate Ce(III)
(
TBA
3
Ce(NO
3
)
6
) derived from ammonium cerium (IV) nitrate,
syn
-2-pyridinealdoxime, ...tetrabutylammonium bromide in 6:9:4 stoichiometric ratio and a mixture of acetic acid and water (10/30, v/v) in a single pot reaction. The structure of the TBA
3
Ce(NO
3
)
6
is characterized using FTIR, UV–Visible and Single X-ray Crystallography technique. Its crystal structure and BVS calculation confirm the oxidation state of cerium ion. The complex TBA
3
Ce(NO
3
)
6
consists of central metal atom cerium (III) ion, which was bound to six nitrate moieties through the coordinate bond with an oxygen atom and the whole moiety is surrounded by three tetrabutylammonium anions and formulates a salt structure. The symmetry point group of complex TBA
3
Ce(NO
3
)
6
is
P
2
1
/
n
(14). From optical measurement, we have calculated the band gap energy of TBA
3
Ce(NO
3
)
6
(4.3 eV), which indicates the complex has semiconductor properties. We have also reported the binding ability of TBA
3
Ce(NO
3
)
6
with CT-DNA through intercalation mode, and the binding constant (
K
b
) is found to be 1.182 × 10
3
M
−1
. The cytotoxicity effect and chromosomal aberration in
Allium cepa
L. root tip cells confirmed the complex's biological activity. Density Function Theory (DFT) is finding out the theoretical evidence of structural and electronic parameters of the complex (by using cif) such as ionization potential (I), electron affinity (A), HOMO–LUMO energy gap, hardness (
η
) and softness (
σ
). The E
HOMO
, E
LUMO
, hardness (
η
), softness (
σ
) and dipole moment (
µ)
are − 3.442 eV, − 2.231 eV, 1.211 eV, 0.603 eV, 1.657 eV
−1
, and 3.830 Debye.
Graphical abstract
Introduction Biological nitrogen fixation (BNF), an unparalleled metabolic novelty among living microorganisms on earth, globally contributes ~88-101 Tg N year −1 to natural ecosystems, ~56% sourced ...from symbiotic BNF while ~22-45% derived from free-living nitrogen fixers (FLNF). The success of symbiotic BNF is largely dependent on its interaction with host-plant, however ubiquitous environmental heterotrophic FLNFs face many limitations in their immediate ecological niches to sustain unhindered BNF. The autotrophic FLNFs like cyanobacteria and oceanic heterotrophic diazotrophs have been well studied about their contrivances acclimated/adapted by these organisms to outwit the environmental constraints for functional diazotrophy. However, FLNF heterotrophs face more adversity in executing BNF under stressful estuarine/marine/aquatic habitats. Methods In this study a large-scale cultivation-dependent investigation was accomplished with 190 NCBI accessioned and 45 non-accessioned heterotrophic FLNF cultivable bacterial isolates (total 235) from halophilic estuarine intertidal mangrove niches of Indian Sundarbans, a Ramsar site and UNESCO proclaimed World Heritage Site. Assuming ~1% culturability of the microbial community, the respective niches were also studied for representing actual bacterial diversity via cultivation-independent next-generation sequencing of V3-V4 rRNA regions. Results Both the studies revealed a higher abundance of culturable Gammaproteobacteria followed by Firmicutes, the majority of 235 FLNFs studied belonging to these two classes. The FLNFs displayed comparable selection potential in media for free nitrogen fixers and iron-oxidizing bacteria, linking diazotrophy with iron oxidation, siderophore production, phosphorus solubilization, phosphorus uptake and accumulation as well as denitrification. Discussion This observation validated the hypothesis that under extreme estuarine mangrove niches, diazotrophs are naturally selected as a specialized multidimensional entity, to expedite BNF and survive. Earlier metagenome data from mangrove niches demonstrated a microbial metabolic coupling among C, N, P, S, and Fe cycling in mangrove sediments, as an adaptive trait, evident with the co-abundant respective functional genes, which corroborates our findings in cultivation mode for multiple interrelated metabolic potential facilitating BNF in a challenging intertidal mangrove environment.
