Twisted Push-Pull Alkenes Bearing Geminal Cyclicdiamino and Difluoroaryl Substituents

The systematic combination of N-heterocyclic olefins (NHOs) with fluoroarenes resulted in twisted push-pull alkenes. These alkenes carry electron-donating cyclicdiamino substituents and two electron-withdrawing fluoroaryl substituents in the geminal positions. The synthetic method can be extended to a variety of substituted push-pull alkenes by varying the NHO as well as the fluoroarenes. Solid-state molecular structures of these molecules reveal a notable elongation of the central C-C bond and a twisted geometry in the alkene motif. Absorption properties were investigated with UV-vis spectroscopy. The redox properties of the twisted push-pull alkenes were probed with electrochemistry as well as UV-vis/NIR and EPR spectroelectrochemistry, while the electronic structures were computationally evaluated and validated.Fil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Universitat Stuttgart; AlemaniaFil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Pal, Sudip. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Universität Stuttgart; AlemaniaFil: Chandrasekhar, Vadapalli. Indian Institute Of Technology Kanpur; IndiaFil: Jana, Anukul. Tata Institute Of Fundamental Research, Hyderabad; Indi

Activation of Aromatic C‐F Bonds by a N‐Heterocyclic Olefin (NHO)

A N-heterocyclic olefin (NHO), a terminal alkeneselectively activates aromatic C-F bonds without the need of anyadditional catalyst. As a result, a straightforward methodology wasdeveloped for the formation of different fluoroaryl substituted alkenesin which the central carbon-carbon double bond is in a twistedgeometry.Fil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Freie Universität Berlin.; AlemaniaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Sarkar, Arighna. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Freie Universität Berlin.; AlemaniaFil: Mote, Kaustubh R.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandrasekhar, Vadapalli. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Jana, Anukul. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Cross-Dehydrocoupling of SiH/NH and Heterofunctionalization Reactions Mediated by Alkali, AlkalineEarth and Early Transition Metal Complexes

Finding molecules which are able to catalyse the reaction between others is an important contribution of molecular chemists to increase the efficiency of chemical reactions. The atom economical reactions or approaches have provided significant challenge to the communities of organometallic chemists and synthetic organic chemists. The term atom economy is conversion efficiency of a reaction process in terms of all atoms involved. In an ideal chemical process the amount of staring materials are equal to the amount of products generated and no atom is wasted. Recent developments like high raw material cost and increased sensitivity to environmental concerns have made atom economical approaches more popular. Chemistry of alkaline-earth metals are less developed and they are often termed as “sleeping beauties” compared to magnesium chemistry. Among the alkaline-earth metals (Mg, Ca, Sr and Ba), magnesium being exceptional which was extensively studied by Grignard, who established the organomagnesium reagent plays a significant role in the synthetic organic and inorganic chemistry. In the recent years, the chemistry of heavier alkaline-earth metals was wellestablished and complexes of the alkaline-earth metals were employed in various catalytic applications such as ring-opening polymerization of various cyclic esters, polymerization of styrene and dienes, and also atom economical reaction, cross-dehydrocoupling of silanes and amines, Hydroelementation (such as hydroamination, hydrophosphination, hydrosilylation and hydroboration) reactions of alkenes and alkynes. In my thesis work, I have mainly focused on the syntheses and structural characterization of well-defined homo- and heteroleptic alkaline-earth and early transition (group IV) metal complexes supported by novel bulky bis-iminopyrrolyl, phosphinanilido-imine chalcogenides, boranes and 1,4-diaza1,3-butadiene (DAD) ligands in their coordination sphere as multi-dentate chelating ligands. All newly prepared heteroleptic metal complexes were used as active precatalysts in atom economical reactions such as cross-dehydrocoupling of silanes with amine and hydroelementation (hydroamination, hydrophosphination and hydrosilylation) reactions

Efficient and chemoselective hydroboration of organic nitriles promoted by TiIV catalyst supported by unsymmetrical acenaphthenequinonediimine ligand

We report the synthesis, characterization, and utilization of a titanium (IV) complex [(η5-C5H5){L}TiCl2] (1) supported by a monoanionic ligand (L), N-(2, 6-diisopropyl)acenaphthenequinonediimido, as a molecular pre-catalyst for the hydroboration of nitriles. The unsymmetrical N-silylated N-(2, 6-diisopropyl)-N-(trimethylsilyl)-acenaphthenequinonediimine ligand (LSiMe3) was obtained upon the completion of a one-pot reaction between N-(2, 6-diisopropyl)iminoacenaphthenone and lithium hexamethyldisilazide in the presence of trimethylsilyl chloride in 1:1:1 M ratio at room temperature. The reaction of LSiMe3 with { η5-(C5H5)TiCl3) in equal proportion (1:1) at 60 °C afforded the titanium complex [(η5-C5H5){L}TiCl2] (1) in good yield. The molecular structures of the N-silyl ligand (LSiMe3) and Ti(IV) complex 1 were established by single-crystal X-ray analysis. Complex 1 was tested as a pre-catalyst for hydroboration of nitriles with pinacolborane (HBpin) and catecholborane (HBcat) to afford diboryl amines at ambient temperature. Titanium complex 1 exhibited high conversion, superior selectivity, and broad functional group tolerance during hydroboration of nitriles with both HBpin and HBcat under mild conditions

Aluminium alkyl complexes supported by imino-phosphanamide ligand as precursors for catalytic guanylation reactions of carbodiimides

Herein, we report the synthesis, characterisation, and application of three aluminium alkyl complexes, [κ2-{NHIRP(Ph)NDipp}AlMe2] (R = Dipp (2a), Mes (2b); tBu (2c), Dipp = 2,6-diisopropylphenyl, Mes = mesityl, and tBu = tert-butyl), supported by unsymmetrical imino-phosphanamide [NHIRP(Ph)NDipp]- [R = Dipp (1a), Mes (1b), tBu (1c)] ligands as molecular precursors for the catalytic synthesis of guanidines using carbodiimides and primary amines. All the imino-phosphanamide ligands 1a, 1b and 1c were prepared in good yield from the corresponding N-heterocyclic imine (NHI) with phenylchloro-2,6-diisopropylphenylphosphanamine, PhP(Cl)NHDipp. The aluminium alkyl complexes 2a, 2b and 2c were obtained in good yield upon completion of the reaction between trimethyl aluminium and the protic ligands 1a, 1b and 1c in a 1:1 molar ratio in toluene via the elimination of methane, respectively. The molecular structures of the protic ligands 1b and 1c and the aluminium complexes 2a, 2b and 2c were established via single-crystal X-ray diffraction analysis. Complexes 2a, 2b and 2c were tested as pre-catalysts for the hydroamination/guanylation reaction of carbodiimides with aryl amines to afford guanidines at ambient temperature. All the aluminium complexes exhibited a high conversion with 1.5 mol% catalyst loading and broad substrate scope with a wide functional group tolerance during the guanylation reaction. We also proposed the most plausible mechanism, involving the formation of catalytically active three-coordinate Al species as the active pre-catalyst. © 2022 The Royal Society of Chemistry

Hydroamination of isocyanates and isothiocyanates by alkaline earth metal initiators supported by a bulky iminopyrrolyl ligand

A series of new heteroleptic alkaline earth (Ae) metal complexes of general formula [{(Ph2CHN-CH)2C4H2N}AeI(THF)3] {Ae = Ca (2), Sr (3), and Ba (4)} were synthesizedviasalt metathesis by reacting potassium salt of ligand1-K[{(Ph2CHN-CH)2C4H2N}K(THF)2] with anhydrous alkaline earth metal diiodides (AeI2). The homoleptic calcium and barium complexes [{(Ph2CHN-CH)2C4H2N}2Ae] [Ae = Ca (5), Ba (6)] were prepared by treating metal bis-hexamethyldisilazide [Ae{N(SiMe3)2}2(THF)2] with the protic ligand1-H[(Ph2CH-N-CH)2C4H2NH] in a 1:2 molar ratio. Calcium complex5was used as an active pre-catalyst for the addition of N-H bond of arylamines across the heterocumulenes such as phenylisocyanate (PhNCO) and phenylisothiocyanate (PhNCS) under neat conditions, and up to 99% yields of the corresponding urea and thiourea derivatives were obtained

Rigid N3O2-Pentadentate Ligand-Assisted Octacoordinate Mononuclear Ln(III) Complexes: Syntheses, Characterization, and Slow Magnetization Relaxation

International audienceA series of air-stable mononuclear octacoordinate Ln(III) complexes, [(L)Ln(TPPO)3]OTf (Ln = Y (1·Y); Gd (1·Gd); Tb (1·Tb); Dy (1·Dy); Ho (1·Ho); and Er (1·Er)) and [(L)Ln(TPPO)(NO3)] (Ln = Y (2·Y) and Dy (2·Dy)), are synthesized employing a rigid N3O2-pentadentate chelating ligand as the basis ligand and meridional ancillary ligands (where H2L = 2,6-diacetylpyridine bis-benzoylhydrazone, TPPO = triphenylphosphine oxide, and OTf– = trifluoromethanesulfonate). All the complexes are synthesized under aerobic conditions and characterized comprehensively by spectroscopic and X-ray crystallographic techniques. Magnetic property investigation on the polycrystalline solid samples of 1·Ln (Ln = Gd, Tb, Dy, Ho, and Er) and 2·Dy are reported. A field-induced single-molecule magnet behavior was observed for the Dy derivatives. 1·Dy exhibits the highest effective energy barrier of magnetization reversal, Ueff/kB = 47 K under Hdc = 1 kOe among the complexes presented herein