Browsing by Subject "DFT CALCULATIONS"

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    Accessing polysubstituted oxazolidines, pyrrolidines and imidazolidines by regioselective [3+2] annulations of ketenimines with donor-acceptor oxiranes and aziridines
    (Royal Society of Chemistry, 2018-05-09) Alajarín, Mateo; Banon, David; Egea, Adrian; Marin-Luna, Marta; Orenes, Raul A.; Vidal, Angel; Química Orgánica
    Efficient [3 + 2] annulations of N-aryl-C,C-diphenyl ketenimines with metallo-carbonyl and metallo-azomethine ylides, generated via the respective Yb(OTf)3 and Y(OTf)3 promoted carbon–carbon bond heterolysis of donor–acceptor oxiranes and aziridines, have been accomplished. These reactions proceeded under mild conditions and supplied a general methodology for the regioselective construction of structurally complex oxazolidines and pyrrolidines. Moreover, heating neat mixtures of N-aryl-C,C-diphenyl ketenimines and diethyl aziridine-2,3-dicarboxylates led to imidazolidine derivatives. A computational study concluded in stepwise mechanisms for these [3 + 2] annulations, also shedding light on their regioselectivity, concerning which of the two cumulated double bonds of the ketenimine becomes involved in the reaction with the ylide.
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    Chemodivergent Conversion of Ketenimines Bearing Cyclic Dithioacetalic Units into Isoquinoline-1-thiones or Quinolin-4-ones as a Function of the Acetalic Ring Size
    (2019-06-21) Alajarín, Mateo; Marin-Luna, Marta; Sanchez-Andrada, Pilar; Vidal, Angel; Química Orgánica
    C-Alkoxycarbonyl-C-phenyl-N-aryl ketenimines bearing 1,3-dithiolan-2-yl or 1,3-dithian-2-yl substituents at ortho position of the C-phenyl ring, respectively, transform into isoquino-line-1-thiones and quinolin-4-ones under thermal treatment in toluene solution. The formation of isoquinolinethiones involves a rare degradation of the 1,3-dithiolane ring, whereas, in contrast, the 1,3-dithiane ring remains intact during the reaction course leading to quinolin-4-ones. Computational density functional theory results support that the kinetically favorable mechanism for the formation of isoquinoline-l-thiones proceeds through a [1,5]-hydride shift/6 pi-electrocyclization cascade, followed by a thiirane extrusion process. Alternative mechanistic paths showing interesting electronic reorganization processes have been also scrutinized but resulted not competitive on energetic grounds.
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    Exploring the Conversion of Macrocyclic 2,2 '-Biaryl Bis(thioureas) into Cyclic Monothioureas: An Experimental and Computational Investigation
    (American Chemical Society, 2018-10-23) Alajarín, Mateo; Lopez-Leonardo, Carmen; Orenes, Raul A.; Pastor Vivero, Aurelia; Sanchez-Andrada, Pilar; Vidal, Angel; Química Orgánica
    Macrocyclic bis(thioureas) derived from 2,2’-biphenyl and binaphthyl skeletons have been synthesized by reaction of 2,2’-diaminobiaryl and 2,2’-bis(isothiocyanato)biaryl derivatives. The splitting of these bis(thioureas) into two units of the respective cyclic monothioureas has been monitored by NMR, shedding some light on the factors that control these processes. Additionally, a computational study revealed up to three mechanistic paths for the conversion of the 2,2’-biphenyl-derived bis(thiourea) into the corresponding monothiourea. The proposed mechanisms account for the participation of a molecule of water as an efficient proton-switch, as well as for different classes of putative intermediates. The computational study also supports the ability of the thiourea group to participate in a plethora of processes, such as prototropic equilibria, sigmatropic shifts, heteroene and retro-heteroene reactions, and cis-trans isomerizations.