01843nas 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<p>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.</p>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<p>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.</p>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-combined