Browsing by Author "Montecinos, Rodrigo"

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    Experimental and theoretical physicochemical study of a new dispirocompound: 4′-(4-fluorophenyl)-2′,7-dimethyl-1,4-dihydro-3H-dispiro[cyclopent[b]indol-2,5′-[1,2]oxazinan-6′3"-indolin]-2",3-dione
    (2021) Satheeshkumar, Rajendran; Montecinos, Rodrigo; Vera, Ariesny; Prasad, Karnam Jayarampillai Rajendra; Kaminsky, Werner; Salas, Cristian O.
    We present Et3N mediated synthesis of a novel dispirocompound from 5-methyl-2-(4'-fluorophenylidine)-1-oxo-1,2,3,8-tetrahydrocyclopent[b]indole, isatin, and sarcosine through 1,3-dipolar cycloaddition reaction. The crystal structure of synthesised compound, 4'-(4-fluorophenyl)-2',7-dimethyl-1,4-dihydro-3H-dispiro[cyclopent[b]indol-2,5'-[1,2]oxazinan-6',3 ''-indolinl-2 '',3-dione is reported. FT-IR, H-1 and C-13 NMR chemical shifts as measured and calculated using B3LYP method with the 6-311G(d,p) basis set in gas phase were found in good agreement. The optimized geometry of the dispirocompound was compared with experimental XRD values. DFT calculations of the molecular electrostatic potential (MEP), Non-covalent interactions and Hirshfeld Surface analysis, Non-linear optical (NLO) properties and frontier molecular orbitals (FMO) identified chemically active sites of the dispirocompound responsible for its chemical reactivity. (C) 2020 Elsevier B.V. All rights reserved.
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    Nucleofugality hierarchy, in the aminolysis reaction of 4-cyanophenyl 4-nitrophenyl carbonate and thionocarbonate. Experimental and theoretical study
    (2021) Montecinos, Rodrigo; Aliaga, Margarita E.; Pavez, Paulina; Cornejo, Patricio; Santos, Jose G.
    Nucleophilic substitution reactions of the title compounds have been investigated with a series of secondary alicyclic amines in several solvents. The solvent, amine, and electrophilic group effects on kinetics, mechanism and nucleofugality hierarchy are discussed from experimental and theoretical studies. These studies show the mechanistic dependence on the solvent polarity; the theoretical results indicate that the relative polarization of the reactive centres (C=O and C=S) and the stabilization of the nucleofuges are the main factors in the control of the product distribution.
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    Supramolecular kinetic effects by pillararenes: the synergism between spatiotemporal and preorganization concepts in decarboxylation reactions†
    (2021) Vieira Silveira, Eduardo; Montecinos, Rodrigo; Scorsin, Leandro; Garcia-Rio, Luis; Medeiros, Michelle; Nascimento, Vanessa; Nome, Faruk; Affeldt, Ricardo F.; Micke, Gustavo A.
    A study about spontaneous decarboxylation reactions of 3-carboxy-1,2-benzisoxazole (CBI) nitrated derivatives (6-NitroCBI and 5,6-DinitroCBI) compared with supramolecular kinetic effects promoted by two cationic pillararenes (P5A and P6A) has been carried out and brings contributions to advance current theories related to supramolecular and enzymatic catalysis/inhibition. A higher energy barrier to spontaneous hydrolysis of 6-NitroCBI relative to that of 5,6-DinitroCBI (Delta Delta G(double dagger) = 2.98 kcal mol(-1)) was determined experimentally, however similar transitions states were observed for both substrates. The host-guest complexes generated catalytic effects up to 7.1-fold on k(obs), except for 6-NitroCBI subset of P5A which is the only system that presented unprecedent inhibitory kinetic effects. The data (kinetics, H-1 NMR titration and molecular dynamic simulations) elucidated the kinetic effects of the four complexes as a result of their geometries, more specifically, by modifying 3 main factors: (1) number of hydrogen bonds between solvent and carboxyl groups of the CBIs, (2) polarization of the O-N bond of the isoxazole ring and (3) reduction of the inductive effect of NO2 groups by field effects. The data from the present study encourage the use of both spatiotemporal and preorganization theories during interpretations related to supramolecular and enzymatic catalysis.
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    The effect of the electrophilic group on the hierarchy of nucleofuges in the aminolysis reactions of thiol- and dithiocarbonates with secondary alicyclic amines: A kinetic and theoretical study
    (2019) Montecinos, Rodrigo; Gazitua, Marcela; Santos, Jose G.
    The aminolysis reactions of O-(4-nitrophenyl) S-aryl dithiocarbonates with different secondary alicyclic amines (SAA) lead to the formation of different 4-nitrophenyl:S-aryl ratios (56:44 and 47:53 for benzenethiol and 4-chlorobenzenethiol, respectively). For the corresponding thiolcarbonates, 4-nitrophenol was the lone product, evidencing the effect of the electrophile moiety on the nucleofugacity hierarchy. The kinetic results show that in the mechanism there are two tetrahedral intermediates: one zwitterionic (T-+/-) and one anionic (T-). As model reactions, the reactions of O-(4-nitrophenyl) S-phenyl thiol- and dithiocarbonates with morpholine were theoretically examined using DFT methods. Theoretical calculations were performed using a continuous solvation model in the absence and presence of one and two explicit water molecules. The microsolvation of T- by one explicit water molecule was predicted as having O-(4-nitrophenyl):S-phenyl distributions of 52:48 and 98:2 for dithiocarbonates and thiolcarbonates, respectively. These results have allowed us to establish that processes such as microsolvation, electronic distribution and the structure of the reactive centers participate in the departure of the leaving groups in the thiolcarbonate and dithiocarbonate aminolysis, although the preferential solvation of these centers seems to have a predominant role in the nucleofuge hierarchy.