01810nas a2200253 4500008004100000022001400041245021300055210006900268260007700337300001400414520076600428653001401194653001601208653003601224653001401260653003601274653001401310100002401324700002001348700001701368700001801385700002101403856013201424 2010 eng d a1434-193X00aCombined experimental and density functional theory study on the Pd-mediated cycloisomerization of o-alkynylnitrobenzenes - synthesis of isatogens and their evaluation as modulators of ROS-mediated cell death0 aCombined experimental and density functional theory study on the aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcNOV a5955-59663 a

Highly selective cycloisomerization of o-alkynylnitrobenzenes, leading to isatogens, has been achieved by employment of a Pd-II complex. This reaction is very general and functional-group-tolerant. The possible mechanism of this reaction was investigated with the help of DFT calculations. Three possible pathways - namely, the addition of the nitro group either in (i) 5-exo-dig or (ii) 6-endo-dig mode and (iii) halopalladation - and subsequent intramolecular events have been considered and studied in detail. These investigations revealed that pathway (i) is the favored route to isatogen formation. A preliminary screening of the available isatogens reveals the 2-alkylisatogens to be novel ROS scavengers capable of inhibiting cellular necroptosis.

10aAnthranil10acyclization10aDensity functional calculations10aisatogens10aNitro-alkyne cycloisomerization10aPalladium1 aRamana, Chepuri, V.1 aPatel, Pitambar1 aVanka, Kumar1 aMiao, Benchun1 aDegterev, Alexei uhttps://library.ncl.res.in/content/combined-experimental-and-density-functional-theory-study-pd-mediated-cycloisomerization-o-001734nas a2200217 4500008004100000022001400041245011900055210006900174260007700243300001400320520087400334653002601208653003601234653002801270653001401298653001301312100001901325700002701344700001701371856012801388 2014 eng d a1434-194800aNature of the active site in ziegler-natta olefin polymerization catalysis systems - a computational investigation0 aNature of the active site in zieglernatta olefin polymerization  aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcOCT a5063-50763 a

Pull quantum chemical calculations with density functional theory (DET) show that a principal role of donors in Ziegler-Nana (ZN) oh-din polymerization catalysts is to coordinate to the metal center at the active sites on the MgCl2 surface. Thereby, the behavior of the catalyst is modulated to favor insertion over termination and, thus, polymerization occurs. This is shown to be true for a range of different donors. The calculations indicate that active sites that feature anionic chloride ligands at the titanium center (the conventional model for the active site) would lead to lower-molecular-weight riolymers. If an -OC2H5 group were present instead of a chloride ligand, the active site would much more effectively produce long chain polymers. Therefore, the current work provides important new insights into the nature of the ZN polymerization process.

10aAlkene polymerization10aDensity functional calculations10aheterogeneous catalysis10aInsertion10aPolymers1 aKumawat, Jugal1 aGupta, Virendra, Kumar1 aVanka, Kumar uhttps://library.ncl.res.in/content/nature-active-site-ziegler-natta-olefin-polymerization-catalysis-systems-computational-001843nas a2200229 4500008004100000022001400041245009900055210006900154260007500223300001400298490000600312520101500318653001501333653001301348653003601361653002201397653001301419100001901432700002701451700001701478856011801495 2016 eng d a1867-388000aEffect of donors on the activation mechanism in ziegler-natta catalysis: a computational study0 aEffect of donors on the activation mechanism in zieglernatta cat aPOSTFACH 101161, 69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcMAY a1809-18180 v83 a

Full quantum chemical calculations, using density functional theory (DFT), have been conducted to explain the effect of donors on the ``activation mechanism'' in the Ziegler-Natta (Z-N) catalyst system. In the activation mechanism, the inactive (TiCl4)-Cl-IV catalyst converts into the active (TiCl2Et)-Cl-III catalyst with the help of the AlEt3 present in the system. The donors that have been considered in this study are: ethyl benzoate (eb), two representative diether cases, a phthalate donor, and a silyl ester donor. The results indicate that eb and the diether donor cases donor have a negative effect on the barriers for the activation mechanism. However, the eb donor can be displaced from the MgCl2 surface by AlEt3, which matches experimental observations. For the phthalate, silyl ester and TiCl3-OC4H8Cl cases, the results indicate that a significant induction period would be present in Z-N systems employing such donors or having such a catalytic center, before catalysis could commence.

10aAlkylation10aaluminum10aDensity functional calculations10asurface chemistry10atitanium1 aKumawat, Jugal1 aGupta, Virendra, Kumar1 aVanka, Kumar uhttps://library.ncl.res.in/content/effect-donors-activation-mechanism-ziegler-natta-catalysis-computational-study02085nas a2200253 4500008004100000022001400041245013600055210006900191260000900260300001400269490000700283520119800290653001401488653001501502653002001517653001901537653003601556100002201592700001901614700002501633700001701658700002401675856013201699 2017 eng d a0947-653900aElectronic control on linear versus branched alkylation of 2-/3-aroylbenzofurans with acrylates: combined DFT and synthetic studies0 aElectronic control on linear versus branched alkylation of 23aro cJUN  a7570-75810 v233 a

Investigations on the factors that govern unusual branched alkylation of 2-aroylbenzofurans with acrylates by Ru-catalyzed carbonyl-directed C-H activation has been carried out by calculating the kinetics associated with the two key steps-the coordination of the acrylate with the intermediate ruthenacycle and the subsequent migratory insertion reaction-studied with the help of DFT calculations. Eight possible orientations for each mode of alkylation have been considered for the calculations. From these calculations, it has been understood that there is a synergistic operation of the steric and electronic effects favoring the branched alkylation. Further DFT investigations on the alkylation of the isomeric 3-aroylbenzofurans indicated a preference for the linear alkylation and this has been verified experimentally. Overall, the observed/calculated complementary selectivity in the alkylation of 2-/3-aroylbenzofurans with acrylates reveals that the substrate-dependent charge distribution of the Ru-C bond in the intermediate ruthenacycle is an important determining factor and thus the current work opens up a new domain of substrate design for controlling regioselectivity.

10aacrylates10aAlkylation10aaroylbenzofuran10aC-H activation10aDensity functional calculations1 aSrinivas, Kolluru1 aDangat, Yuvraj1 aKommagalla, Yadagiri1 aVanka, Kumar1 aRamana, Chepuri, V. uhttps://library.ncl.res.in/content/electronic-control-linear-versus-branched-alkylation-2-3-aroylbenzofurans-acrylates-combined01733nas a2200241 4500008004100000022001400041245012100055210006900176260000800245300001400253490000700267520090400274653001701178653001401195653002001209653003601229653002601265100001901291700001701310700001701327700001901344856012801363 2018 eng d a0947-653900aBeyond hydrofunctionalisation: a well-defined calcium compound catalysed mild and efficient carbonyl cyanosilylation0 aBeyond hydrofunctionalisation a welldefined calcium compound cat cJAN a1269-12730 v243 a

Organocalcium compounds have been reported as efficient catalysts for various transformations, for cases in which one of the substrates contained an E-H (E=B, N, Si, P) bond. Here, we look at the possibility of employing an organocalcium compound for a transformation in which none of the precursors has a polar E-H bond. This study demonstrates the utilization of a well-defined amidinatocalcium iodide, [PhC(NiPr)(2)CaI] (1) for cyanosilylation of a variety of aldehydes and ketones with Me3SiCN under ambient conditions without the need of any co-catalyst. The reaction mechanism involves a weak adduct formation between 1 and Me3SiCN leading to the activation of the Si-C bond, which subsequently undergoes sigma-bond metathesis with a C=O moiety. Such a mechanistic pathway is unprecedented in alkaline earth metal chemistry. Experimental and computational studies support the mechanism.

10aCa catalysis10acarbonyls10acyanosilylation10aDensity functional calculations10atransition-metal free1 aYadav, Sandeep1 aDixit, Ruchi1 aVanka, Kumar1 aSen, Sakya, S. uhttps://library.ncl.res.in/content/beyond-hydrofunctionalisation-well-defined-calcium-compound-catalysed-mild-and-efficient02326nas a2200229 4500008004100000022001400041245012600055210006900181260000800250300001400258490000700272520151300279653001901792653003601811653001901847653002001866653002401886100002101910700002101931700001701952856012701969 2021 eng d a1439-423500aComputational insights into the role of external and local electric fields in macrocyclic chemical and biological systems0 aComputational insights into the role of external and local elect cDEC a2484-24920 v223 aThe investigation of the role of the electric field in systems of widespread interest employing computational techniques is an emerging area of research. The outcome of applying an oriented external electric field (OEEF) on the geometric and electronic properties of the chemically unique pi-conjugated cyclic carbon ring compounds has been explored with density functional theory (DFT). Distinct changes in the structural and electronic features of such ring compounds are observed upon the application of OEEFs. Importantly, the calculations indicate that a mixed aliphatic-aromatic conjugated ring converts from a singlet to a triplet after the application of an OEEF, suggesting potential applications in optoelectronics for such molecules, without the need for photochemically induced change in the spin state. Furthermore, the influence of built-in local electric fields (LEFs) present in naturally occurring macrocyclic systems such as valinomycin has also been explored. Static and ab initio molecular dynamics (AIMD) calculations indicate that LEFs are the primary driving factor in determining the energetically favoured position of counter anions such as chloride (Cl-) in the potassium (K+) and sodium (Na+) coordinated valinomycin macrocycle structures: they exist inside the cage in the case of K+ sequestration by valinomycin and outside for Na+. This divergence has been proposed to be the determining factor for the selectivity of the valinomycin macrocycle for binding a K+ cation over Na+.10acounter anions10aDensity functional calculations10aelectric field10aion selectivity10amacrocyclic systems1 aMukherjee, Anagh1 aGhule, Siddharth1 aVanka, Kumar uhttps://library.ncl.res.in/content/computational-insights-role-external-and-local-electric-fields-macrocyclic-chemical-and02013nas a2200217 4500008004100000022001400041245011600055210006900171260000800240300001500248490000700263520120100270653003601471653002301507653002901530653002001559653002401579100002501603700001701628856015001645 2023 eng d a1861-472800a"Weak" C-H•••S interaction drives enantioselectivity in cinchona alkaloid complex catalyzed thiocyanation0 aWeak CH S interaction drives enantioselectivity in cinchona alka cJUL ae2023003210 v183 a

The great success of asymmetric organocatalysis has made it one of the most important advancements made in chemistry in the past two decades. A significant achievement in this context is the asymmetric organocatalysis of the thiocyanation reaction. In the current study, computational studies with density functional theory have been done in order to understand an interesting experimental finding: the reversal of enantioselectivity from R to S when the electrophile is changed from beta-keto ester to oxindole for the thiocyanation reaction with the cinchona alkaloid complex catalyst. The calculations reveal an unusual fact - the principal reason for the reversal is the presence of the C-H center dot center dot center dot S noncovalent interaction, which is present only in the major transition states in each of the two nucleophile cases. Only recently has it been realized that the supposedly weak C-H center dot center dot center dot S noncovalent interaction has the properties of a hydrogen bond, and the fact that this interaction is the cause of enantioselectivity has relevance, because of the large number of asymmetric transformations involving the sulphur heteroatom.

10aDensity functional calculations10aEnantioselectivity10anoncovalent interactions10aorganocatalysis10areaction mechanisms1 aBanerjee, Subhrashis1 aVanka, Kumar uhttps://library.ncl.res.in/content/weak-c-h%E2%80%A2%E2%80%A2%E2%80%A2s-interaction-drives-enantioselectivity-cinchona-alkaloid-complex-catalyzed