@article {48405, title = {Silver dependent enantiodivergent gold(i) catalysed asymmetric intramolecular hydroamination of alkenes: a theoretical study}, journal = {Catalysts}, volume = {12}, year = {2022}, month = {NOV}, pages = {1392}, type = {Article}, abstract = {

We report a theoretical study of the first silver-dependent enantiodivergent gold-catalysed reaction. The combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate catalyses the asymmetric intramolecular hydroamination of alkenes and affords both enantiomers of the products by applying a simple solvent change from toluene to methanol. A gold-silver chloride adduct that occurs only in methanol appears to control the enantioinversion. If one gold atom coordinates and activates the alkene moiety, the other gold is included in an adduct with silver chloride, which coordinates a methanol solvent molecule and further interacts with the amine function. If the use of toluene implies free anions and affords (S)-enantiomer, methanol allows a proximal interaction with the amine, leads to an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and results in the (R)-enantiomer.

}, keywords = {alkene, enantiodivergent catalysis, Gold, hydroamination, Silver}, doi = {10.3390/catal12111392}, author = {Dixit, Ruchi and Sharma, Himanshu and Agbossou-Niedercorn, Francine and Vanka, Kumar and Michon, Christophe} } @article {48051, title = {Tridentate NacNac stabilized tin and nickel complexes: access to a monomeric nickel hydride and its catalytic application}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {OCT}, pages = {17370-17377}, type = {Article}, abstract = {

The transmetalation reaction of picolyl-supported tridentate nacnac germylene monochloride [2,6-iPr2-C6H3NC-(Me)CHC(Me)NH(CH2py)]GeCl (1) (py = pyridine) with SnCl2 results in an analogous stannylene chloride (2). The three -coordinated stannylenium cation [{2,6-iPr2-C6H3NC(Me)CHC-(Me)NH(CH2py)}Sn]+ with SnCl3- as a counteranion (3) has been generated through the abstraction of chloride ligand from 2 using an additional equivalent of SnCl2. Instead of forming a donor-acceptor complex, 2 undergoes a facile redox trans-metalation reaction with Ni(COD)2 (COD = cyclooctadiene) and CuCl to afford analogous nickel and copper complexes [2,6-iPr2-C6H3NC(Me)CHC(Me)NH(CH2py)]MCl [M = Ni (4) and Cu (5)]. The reactions of 4 with potassium tri-sec-butylborohydride (commonly known as K-selectride) and AgSbF6 provide access to monomeric Ni(II) hydride, [2,6-iPr2-C6H3NC(Me)CHC(Me)NH(CH2py)]NiH (6) and a Ni(II) cation, [{2,6-iPr2- C6H3NC(Me)CHC(Me)NH(CH2py)}Ni][SbF6] (7), respectively. 6 was found to be an effective catalyst for the hydroboration of amides.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c03227}, author = {Pahar, Sanjukta and Sharma, Vishal and Mahata, Biplab and George, Christy P. and Sharma, Himanshu and Vanka, Kumar and Sen, Sakya S.} } @article {48032, title = {Well-defined calcium compound catalyzes trimerization of arylisocyanates into 1,3,5-triarylisocyanurates}, journal = {ChemCatChem}, volume = {14}, year = {2022}, month = {JUN }, pages = {e202101788}, type = {Article}, abstract = {

We report the synthesis of a calcium complex (2) bearing a tetradentate monoanionic ligand with a diaminoethane core and phenolate and pyridine peripheral donors. Single crystal X-ray studies on 2 revealed that LiI was also co-crystallized, leading to a four-membered ring with four different elements. 2 was found to be an efficient catalyst for the cyclotrimerization of a variety of aromatic isocyanates under mild conditions.

}, keywords = {calcium, Cyclotrimerization, Isocyanurates, Tetradentate ligand}, issn = {1867-3880}, doi = {10.1002/cctc.202101788}, author = {Kumar, Rohit and Sharma, Vishal and Jain, Shailja and Sharma, Himanshu and Vanka, Kumar and Sen, Sakya S.} } @article {48687, title = {On the competition between six-membered and five-membered NHC towards alane centered ring expansion}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {JUL}, pages = {8540-8543}, type = {Article}, abstract = {

The combination of 6-SIDipp center dot AlH3 (1) and 5-IDipp resulted in the ring expansion of 6-NHC, while the five-membered NHC remained unchanged, which was subsequently explained by DFT studies. Besides, the substitution chemistry of 1 was also studied with TMSOTf and I-2, which gave rise to the substitution of a hydride by triflate or iodide ligands.

}, issn = {1359-7345}, doi = {10.1039/d3cc02063k}, author = {Balayan, Kajal and Sharma, Himanshu and Vanka, Kumar and Ravindranathan, Sapna and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {48283, title = {Computational insights into the iron-catalyze d magnesium-me diate d hydroformylation of alkynes}, journal = {Journal of Organometallic Chemistry}, volume = {986}, year = {2023}, month = {FEB}, pages = {122621}, type = {Article}, abstract = {

Iron is one of the most abundant transition metals in the earth{\textquoteright}s crust. It has attracted a lot of attention due to its low toxicity, bio-compatibility, and high natural abundance. Iron-catalyzed hydroamination, hydroalkoxylation, hydrocarboxylation, hydrosilylation, hydroboration, hydrophosphination, hydromagnesiation, and carbonylation reactions have therefore been developed over the past decades. However, despite many experimental and theoretical studies, a complete mechanistic understanding of iron-catalyzed hydrofunctionalisation at the molecular level has not yet been achieved. In this work, through density functional theory (DFT) calculations, we have shown the most feasible path for the hydroformylation of alkynes for an experimentally studied system. We have looked at the iron salt as a precatalyst without any external donor ligand, and the calculations revealed that hydrometalation followed by beta-hydride elimination was favorable over the direct migration of the beta-hydrogen to carbon. Furthermore, our calculations show that the solvent plays an important role in the hydromagnesiation reaction. Furthermore, we have employed an explicit solvent model, where the attachment of one molecule of solvent to the iron center was seen to stabilize the transition states significantly.(c) 2023 Elsevier B.V. All rights reserved.

}, keywords = {Computational study, Ethylene Assisted Catalysis, EtMgBr Assistance, Explicit Role of Solvent, Hydroformylation, Iron Catalyst}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2023.122621}, author = {Sharma, Himanshu and Tewari, Tanuja and Chikkali, Samir H. and Vanka, Kumar} } @article {48472, title = {Rivaroxaban eutectics with improved solubility, dissolution rates, bioavailability and stability}, journal = {Crystengcomm}, volume = {25}, year = {2023}, month = {JUN }, pages = {3253-3263}, type = {Article}, abstract = {

Rivaroxaban (RXB) is a direct factor Xa inhibitor used for the treatment of deep vein thrombosis (DVT, a blood clot in the leg) and pulmonary embolism (PE, a blood clot in the lung) and to prevent blood clots in atrial fibrillation following hip or knee surgery. However, RXB suffers from poor solubility that hinders its broader application. Although its cocrystals are reported for solubility enhancement, the methodology used to prepare multi-component crystals is complex. Also, it uses hazardous solvents to develop cocrystals. We have prepared eutectics of RXB with caffeic acid (CAA), coumaric acid (CA), fumaric acid (FA), succinic acid (SA), mandelic acid (MA) and trimesic acid (TA) and analyzed them using hot stage microscopy (HSM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and fourier transform infrared spectroscopy (FTIR) techniques. The saturation solubility and dissolution rate profiles were also obtained to investigate the effect of eutectics on these parameters. Amongst all the coformers tested, coformers CAA, CA, and FA showed significant enhancement in the solubility of RXB. The powder dissolution rate of the eutectics showed considerable enhancement compared to that of RXB. In vivo pharmacokinetic study was carried out for RXB-CAA, RXB-CA and RXB-FA in rats and compared with RXB, which showed 1.5 and 1.4 times enhancement in relative bioavailability for RXB-CAA and RXB-CA, respectively. Stability studies were carried out as per ICH guidelines for all the eutectics, which revealed excellent stability over six months under accelerated (40 degrees C and 75\%) conditions and twelve months under long-term (30 degrees C and 60\% RH) conditions. The DFT studies carried out using the B3LYP/TZVP level of theory revealed higher Gibbs free interaction energy (Delta G(int)) for homosynthons (drugMIDLINE HORIZONTAL ELLIPSISdrug and coformerMIDLINE HORIZONTAL ELLIPSIScoformer) than heterosynthons (drugMIDLINE HORIZONTAL ELLIPSIScoformer).

}, doi = {10.1039/d3ce00261f}, author = {Shaligram, Parth S. and George, Christy P. and Sharma, Himanshu and Mahadik, Kakasaheb R. and Patil, Sharvil and Vanka, Kumar and Arulmozhi, S. and Gonnade, Rajesh G.} } @article {49024, title = {Bronsted acid-promoted cyclodimerization of α,β-unsaturated γ-ketoesters: construction of fused pyrano-ketal-lactones and γ-ylidene-butenolides}, journal = {ACS Omega}, volume = {9}, year = {2024}, month = {APR }, pages = {19859-19878}, type = {Article}, abstract = {

Unprecedented MsOH-promoted diastereoselective cascade dimerization and intramolecular lactonization of readily accessible alpha,beta-unsaturated gamma-ketoesters are presented. The results obtained in this work, control experiments, and density functional theory (DFT) calculations suggested that the initial enolization and E to Z isomerization/equilibration of olefin (C=C) of substrate alpha,beta-unsaturated gamma-ketoesters give a Z-isomer preferentially over an E-isomer. Subsequently, the Z-isomer undergoes intermolecular annulation with alpha,beta-unsaturated gamma-ketoesters via domino Michael addition/ketalization/lactonization steps to furnish fused tetracyclic pyrano-ketal-lactone. However, the Z-isomer prefers intramolecular trans-esterification in a competing pathway and gives bicyclic gamma-ylidene-butenolide. The key features of this work include simple Br \& oslash;nsted acid catalysis, the formation of three bonds, two rings, and three contiguous stereogenic centers in a single step, DFT calculations, and the assignment of relative stereochemistry through X-ray diffraction (XRD) and two-dimensional (2D) nuclear magnetic resonance (NMR) analyses.

}, issn = {2470-1343}, doi = {10.1021/acsomega.3c08873}, author = {Vinodkumar, Ramavath and Nakate, Ashwini K. and Sharma, Himanshu and Vanka, Kumar and Rama Krishna, Gamidi and Kontham, Ravindar} } @article {49092, title = {Br{\o}nsted acid- and Ni(ii)-catalyzed C-H oxidation/rearrangement of cyclotriveratrylenes (CTVs) to cyclic and acyclic quinones as potential anti-cancer agents}, journal = {Organic and biomolecular chemistry}, volume = {22}, year = {2024}, month = {JAN }, pages = {1038-1046}, type = {Article}, abstract = {

This paper describes a simple and practical protocol for the direct synthesis of acyclic and cyclic quinone derivatives via an acid-promoted nickel(ii)-catalyzed inner rim C-H oxidation of cyclotriveratrylene (CTV) and its analogues. The cyclic quinone derivatives resulted from trimethoxy-cyclotriveratrylene (TCTV) through C-C bond formation via intramolecular ipso substitution followed by subsequent anionic rearrangement containing stereo-vicinal quaternary centers. The DFT calculations strongly support the experimental findings and reveal the role of Bronsted acids in the C-H bond activation of CTV. All the newly synthesized compounds were screened for their in vitro anti-cancer activity using colorimetric SRB assay analysis. Among them, compounds 3a, 3d, 3h, 4a, 4b, 4c and 4e exhibited moderate anticancer activity against A549, HCT-116, PC-3, MDA-MB-231, HEK-293 and SW620 human cancer cell lines.

}, issn = {1477-0520}, doi = {10.1039/d3ob01428b}, author = {Darole, Ratanamala S. and Choudhary, Shailendra Singh and Sharma, Himanshu and Mali, Bhupendra P. and Gopu, Booblan and Vanka, Kumar and Senthilkumar, Beeran} } @article {49280, title = {In silico discovery of a neutral 2π aromatic silicon aluminum compound}, journal = {Organometallics}, volume = {43}, year = {2024}, month = {JUL}, pages = {1583-1592}, type = {Article}, abstract = {

The recently developed ab initio nanoreactor (AINR) approach to identifying reaction intermediates and pathways without the necessity of experimental input has been employed in the current work to locate new cyclic silicon-based structures that have the potential to display aromaticity. Using this approach, we have identified many cyclic silicon-based molecules that have been experimentally reported over the past three decades. More importantly, the current work showcases an interesting new molecule that has been discovered through this approach: a four-membered cyclic compound of silicon and aluminum that displays significant 2 pi aromaticity and is capable of the activation of important small molecules such as ammonia.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.4c00151}, author = {Sharma, Himanshu and Vanka, Kumar} } @article {49017, title = {Iron-catalyzed (E)-selective hydrosilylation of alkynes: scope and mechanistic insights}, journal = {Catalysis Science and Technology}, volume = {14}, year = {2024}, month = {MAY}, type = {Article}, abstract = {

Iron-catalyzed hydrosilylation of internal alkynes has been rarely reported. Even in these rare cases, additives have been used for the success of the reaction, which often creates a problem for the functional group tolerance of the reaction. Herein, we report an additive-free iron-catalyzed (E)-selective hydrosilylation of internal alkynes in the presence of a phosphine ligand. A low-valent Fe(0) complex [Fe(CO)(3)(BDA)] {[Fe-1]} catalyzed the hydrosilylation of alkynes at 60 to 120 degrees C, exhibited a broad substrate (24 substrates) scope and tolerated different functional groups. The synthetic utility of the reaction was demonstrated by a gram scale experiment, preparing alkenes, and by chemo-selective hydrosilylation. The modus operandi of the reaction has been investigated by i) homogeneity test, ii) radical trapping experiments, iii) X-ray photoelectron spectroscopy, and iv) by preparing a Fe(II) complex as catalyst control. These mechanistic investigations revealed a two-electron pathway for the hydrosilylation of alkynes. In addition, kinetic investigations were undertaken to shed light on the rates of the reaction. Kinetic studies suggest the absence of an induction period, and the reaction is first order with respect to the concentration of iron catalyst [Fe-1] and zeroth order with respect to the substrate (alkyne). The Hammett plot suggests that strongly electron-withdrawing groups on the alkyne favour the hydrosilylation reaction. Meanwhile Eyring analysis suggests that the rate-determining step likely involves an associative pathway. Based on the findings of the mechanistic and kinetic investigation, a plausible Chalk-Harrod-type mechanism is likely to be operative. The proposed mechanism is substantiated by computational investigations, which suggested that the Chalk-Harrod mechanism is kinetically more favored by 15.8 kcal mol(-1) over the modified Chalk-Harrod mechanism.

}, issn = {2044-4753}, doi = {10.1039/d3cy01775c}, author = {Sen, Anirban and Tewari, Tanuja and Kumar, Rohit and Vinod, C. P. and Sharma, Himanshu and Vanka, Kumar and Chikkali, Samir H.} } @article {49429, title = {Rational monomer design for the synthesis of conjugated polymers by direct heteroarylation polymerization}, journal = {ACS Polymers Au}, volume = {4}, year = {2024}, month = {JUL}, pages = {449{\textendash}459}, type = {Article}, abstract = {

This study focuses on the design concepts that contribute to the C{\textendash}H activation in bithiophene-flanked monomers incorporating naphthalene diimide (NDI), perylene diimide (PDI), and fluorene (FLU) and their polymerization by direct heteroarylation. Density functional theory (DFT) calculations reveal distinct energy requirements for C{\textendash}H bond abstraction, which is dictated by the electron-withdrawing strength of the central aromatic core flanked by bithiophene. These provide insights into the reactivity of each monomer for C{\textendash}H bond activation. Proton NMR spectroscopic experimental results confirm the favorable energetic profiles predicted by DFT, with NDI- and PDI-flanked monomers exhibiting lower energy requirements than fluorene-flanked monomers. Successful polymer synthesis is demonstrated for NDI and PDI, while the fluorene-flanked monomer shows challenges due to its higher energy demands.

}, doi = {https://doi.org/10.1021/acspolymersau.4c00050}, author = {Kakde, Navnath R. and Sharma, Himanshu and Dalvi, Nitin V. and Vanka, Kumar and Asha, S. K} } @article {49089, title = {Size matters: computational insights into the crowning of noble gas trioxides}, journal = {Inorganic Chemistry}, volume = {63}, year = {2024}, month = {FEB}, pages = {4099-4107}, type = {Article}, abstract = {

In pursuit of enhancing the stability of the highly explosive and shock-sensitive compound XeO3, we performed quantum chemical calculations to investigate its possible complexation with electron-rich crown ethers, including 9-crown-3, 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7, as well as their thio analogues. Furthermore, we expanded our study to other noble gas trioxides (NgO(3)), namely, KrO3 and ArO3. The basis set superposition error (BSSE) corrected interaction energies for these adducts range from -13.0 kcal/mol to -48.2 kcal/mol, which is notably high for sigma-hole-mediated noncovalent interactions. The formation of these adducts was observed to be more favorable with the increase in the ring size of the crowns and less favorable while going from XeO3 to ArO3. A comprehensive analysis by various computational tools such as the mapping of the electrostatic potential (ESP), Wiberg bond indices (WBIs), Bader{\textquoteright}s theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, noncovalent interaction (NCI) plots, and energy decomposition analysis (EDA) revealed that the C-H center dot center dot center dot O interactions, as well as dispersion interactions, play a pivotal role in stabilizing adducts involving larger crowns. A noteworthy outcome of our study is the revelation of a coordination number of 9 for xenon in the complex formed between XeO3 and the thio analogue of 18-crown-6, which is higher than the largest number reported to date.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.3c03782}, author = {Dash, Soumya Ranjan and Sharma, Himanshu and Tiwari, Mrityunjay K. and Greb, Lutz and Vanka, Kumar} } @article {49279, title = {Uncovering diverse reactivity of NHCs withdiazoalkane: C-H activation}, journal = {Chemical Science}, volume = {15}, year = {2024}, month = {NOV}, pages = {18387-18394}, type = {Article}, abstract = {

N-heterocyclic carbenes (NHCs) have attracted significant attention due to their strong sigma-donating capabilities, as well as their transition-metal-like reactivity towards small molecules. However, their interaction with diazoalkanes remains understudied. In this manuscript, we explore the reactivity of a series of stable carbenes, encompassing a wide range of electronic properties, with Me3SiCHN2. 5-SIPr activates the C-H bond of Me3SiCHN2, resulting in the formation of a novel diazo derivative (1), while carbenes such as 5-IPr, 6-SIPr, and diamido carbene yield N-heterocyclic methylenehydrazine derivatives (3, 4, and 8). The reaction of Me3SiCHN2 with 5-ItBu unexpectedly leads to the formation of a triazole ring linked with the imidazole moiety via a CC double bond (6) alongside the azine product (7). Substituting the diazoalkane with diazoester consistently yields azine derivatives (9-12 and 14). Only in the case of 5-ItBu, an imidazolium salt with tetrazenide anion (13) was obtained as a side product. The reaction of 4 with HCl resulted in the desilylprotonation to form a salt, 5a, which undergoes deprotonation upon using bases such as Et3N and KHMDS to form N-heterocyclic methylene hydrazine, 5. Theoretical calculations have been conducted to elucidate the diverse mechanisms underlying product formation.

}, issn = {2041-6520}, doi = {10.1039/d4sc05740f}, author = {Balayan, Kajal and Sharma, Himanshu and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {49381, title = {Unravelling the prebiotic origins of the simplest α-ketoacids in cometary ices: a computational investigation}, journal = {CHEMICAL COMMUNICATIONS}, volume = {60}, year = {2024}, month = {OCT }, pages = {11283-11286}, type = {Journal Article}, keywords = {GLYOXYLATE, Hydrocarbons, Metabolism, Precursors}, issn = {1359-7345}, doi = {10.1039/d4cc03074e}, author = {Dash, Soumya Ranjan and Pandya, Rinu and Singh, Geetika and Sharma, Himanshu and Das, Tamal and Haldar, Hritwik and Hotha, Srinivas and Vanka, Kumar} }