01982nas a2200241 4500008004100000022001400041245010800055210006900163260000800232300001400240490000600254520113500260653001801395653003001413653001301443653002501456653002301481653003301504653003401537100002501571700001701596856012701613 2018 eng d a2155-543500aB(C6F5)(3): catalyst or initiator? insights from computational studies into surrogate silicon chemistry0 aBC6F53 catalyst or initiator insights from computational studies cJUL a6163-61760 v83 a

One of the most promising recent developments in catalysis has been the use of the metal-free Lewis acid B(C6F5)(3) as a catalyst for a range of different chemical transformations. Perhaps the most impressive achievement in this regard is the recently accomplished in situ generation of SiH4 from surrogates (Simonneau and Oestreich, Nat. Chem., 2015,7, 816). However, what the current computational work, with density functional theory, reveals is that this process, in addition to being catalyzed by B(C6F5)(3), is also significantly dominated by a series of autocatalytic reactions. The results are further corroborated by the use of the energetic span model, which shows that the turnover frequency is higher for the newly proposed autocatalytic pathway in comparison to the conventional B(C6F5)(3)-catalyzed pathway. The current work therefore provides interesting new insights into surrogate silicon chemistry. But, more importantly, the current studies indicate that B(C6F5)(3) is likely to function more as an initiator rather than a pure catalyst in many metal-free transformations that have been reported to date.

10aautocatalysis10aDensity functional theory10aion-pair10aLewis acid catalysis10areaction mechanism10asurrogate silicone chemistry10atris(pentafluorophenyl)borane1 aBanerjee, Subhrashis1 aVanka, Kumar uhttps://library.ncl.res.in/content/bc6f53-catalyst-or-initiator-insights-computational-studies-surrogate-silicon-chemistry01733nas 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-efficient01990nas a2200205 4500008004100000022001400041245015200055210007200207260000900279300001600288490000600304520119700310100002501507700002401532700002101556700001701577700002601594700002201620856014201642 2024 eng d a2470-134300aBronsted acid-promoted cyclodimerization of α,β-unsaturated γ-ketoesters: construction of fused pyrano-ketal-lactones and γ-ylidene-butenolides0 aBronsted acidpromoted cyclodimerization of αβunsaturated γketoes cAPR  a19859-198780 v93 a

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.

1 aVinodkumar, Ramavath1 aNakate, Ashwini, K.1 aSharma, Himanshu1 aVanka, Kumar1 aKrishna, Gamidi, Rama1 aKontham, Ravindar uhttps://library.ncl.res.in/content/bronsted-acid-promoted-cyclodimerization-%CE%B1%CE%B2-unsaturated-%CE%B3-ketoesters-construction-fused01776nas a2200217 4500008004100000022001400041245017200055210007000227260000900297300001400306490000700320520092900327100002701256700003301283700002101316700002401337700001801361700001701379700002501396856013701421 2024 eng d a1477-052000aBrønsted acid- and Ni(ii)-catalyzed C-H oxidation/rearrangement of cyclotriveratrylenes (CTVs) to cyclic and acyclic quinones as potential anti-cancer agents0 aBrønsted acid and Nisciisccatalyzed CH oxidationrearrangement of cJAN  a1038-10460 v223 a

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.

1 aDarole, Ratanamala, S.1 aChoudhary, Shailendra, Singh1 aSharma, Himanshu1 aMali, Bhupendra, P.1 aGopu, Booblan1 aVanka, Kumar1 aSenthilkumar, Beeran uhttps://library.ncl.res.in/content/br%C3%B8nsted-acid-and-niii-catalyzed-c-h-oxidationrearrangement-cyclotriveratrylenes-ctvs-cyclic02259nas a2200277 4500008004100000245015100041210006900192260000800261300001600269490000600285520129900291653001801590653002801608653000801636653002001644653003001664653002401694100002001718700001901738700001801757700002101775700001701796700001701813700002001830856013101850 2025 eng d00aBioinspired synthesis of bridged isochromane fused pyrazoles by a silver catalyzed cascade reaction and its application for antibacterial activity0 aBioinspired synthesis of bridged isochromane fused pyrazoles by  cAUG a4184–41950 v53 a

A stereoselective silver catalyzed one pot vinylogous aldol addition followed by a cascade [4+2] cycloaddition reaction of α-arylidene pyrazolinones to in situ generated isochromenylium ions has been developed, which provides an unprecedented bridged [2.2.2] [3.3.1] pentacyclic [5-6-6-6-6] skeleton consisting of an isochroman, chroman, and a pyrazole unit in one molecule with good to high yields as a single diastereomer. This method offers mild reaction conditions, wide substrate compatibility, excellent scalability and easy derivatization. A DFT study was carried out to clarify the reaction mechanism. It was exciting to observe that the unprecedented bridged isochromans synthesized here have shown excellent selectivity toward Gram-positive and Gram-negative bacteria. We demonstrate that while some structures are broad spectrum antibacterial there are two distinct structures that can be explored for selective activity.

10aAntibacterial10aBridged [2.2.2] [3.3.1]10aROS10aStereoselective10aVinylogous aldol addition10a[4+2] cycloaddition1 aSingh, Bhuvnesh1 aTewari, Shreya1 aKaur, Manleen1 aSharma, Himanshu1 aVanka, Kumar1 aSingh, Neetu1 aSingh, Ravi, P. uhttps://library.ncl.res.in/content/bioinspired-synthesis-bridged-isochromane-fused-pyrazoles-silver-catalyzed-cascade-reaction