Lingli Han

Bio: Lingli Han is an academic researcher from Qufu Normal University. The author has contributed to research in topics: Steric effects & Regioselectivity. The author has an hindex of 6, co-authored 19 publications receiving 112 citations.

Theoretical investigation of the impact of ligands on the regiodivergent Rh-catalyzed hydrothiolation of allyl amines

Abstract: The reaction mechanisms of the Rh-catalyzed regiodivergent hydrothiolation of allyl amines have been theoretically investigated with the aid of density functional theory (DFT) calculations. The impact of ligands on the regioselectivity was rationalized. The origin of the regioselectivity involved in these reactions was probed by investigating the electronic and steric effects. The regioselectivity is derived from the stability of related intermediates. Among them, the steric effect plays an important role in controlling the regioselectivity. The origin of the regioselectivity could also be interpreted through the electronic effect on the corresponding transition states.

Mechanistic insight into the C7-selective C–H functionalization of N-acyl indole catalyzed by a rhodium complex: a theoretical study

Abstract: Herein, the reaction mechanisms for the rhodium-catalyzed regioselective C7-functionalization of N-acyl indole are theoretically investigated by employing density functional theory (DFT) calculations. The role of the additive AgNTf2 in enhancing the reactivity and selectivity for the C7–H functionalization of N-acyl indole is clarified by calculations. The origins of the effect of the substituent group at the 6-position of N-acyl indole on the regioselectivity are explored by analyzing the electron and steric effects. The 7-olefination product is preferred for the H-substituted substrate (reaction A), which is attributed to the greater nucleophilicity of the C7 atom in comparison to that of the C2 atom. This facilitates the subsequent electrophilic attack of the Rh center. In reaction B with the CF3-substituted substrate, the 2-olefination product is preferred over the 7-olefination product mainly because of the stronger steric effects in TS2(C7)F compared with that in TS2(C2)F.

Mechanistic insight into the selective cyclization of arylnitrones to indolines via Rh(III) catalyst: a theoretical study

Abstract: A density functional theory (DFT) study was performed to understand detailed mechanisms for the Rh(III)-catalyzed coupling reaction of phenylnitrone with diphenylacetylene in different reaction conditions. The reaction proceeds via five sequential steps, including arene C–H activation, alkyne insertion, oxygen atom transfer (OAT), protonolysis, and C–C bond coupling. Among the five steps, protonolysis is the rate- and diastereoselectivity-determining step. Furthermore, the effect of pivalic acid additive, solvent, and center metal of the catalyst on the diastereoselectivity and yields is investigated. The experimental observations in different conditions can be interpreted reasonably by our calculations.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Computational Studies of Carboxylate-Assisted C-H Activation and Functionalization at Group 8-10 Transition Metal Centers

Abstract: Computational studies on carboxylate-assisted C–H activation and functionalization at group 8–10 transition metal centers are reviewed This Review is organized by metal and will cover work published from late 2009 until mid-2016 A brief overview of computational work prior to 2010 is also provided, and this outlines the understanding of carboxylate-assisted C–H activation in terms of the “ambiphilic metal–ligand assistance” (AMLA) and “concerted metalation deprotonation” (CMD) concepts Computational studies are then surveyed in terms of the nature of the C–H bond being activated (C(sp2)–H or C(sp3)–H), the nature of the process involved (intramolecular with a directing group or intermolecular), and the context (stoichiometric C–H activation or within a variety of catalytic processes) This Review aims to emphasize the connection between computation and experiment and to highlight the contribution of computational chemistry to our understanding of catalytic C–H functionalization based on carboxylate-ass

Metal-catalyzed regiodivergent organic reactions

Abstract: Metal-catalyzed regiodivergent reactions allow control over regioselectivity in the synthesis of a wide range of organic products. Starting from the same material, it is possible to prepare different regioisomers just by appropriately choosing the catalyst or by modifying the reaction conditions. Therefore, these regiodivergent methodologies should be included as the key factor in the concept of efficiency and atom economy in synthetic organic chemistry. The synthetic potential of this subject has been demonstrated mainly in addition reactions to unsaturated carbon–carbon bonds, allylic and propargylic nucleophilic substitutions, C–H activation reactions, cross-couplings, and intramolecular or intermolecular cyclizations. This review article overviews the development and rationalization of regiodivergence in these fundamental reactions in the last 15 years.

Catalytic Hydrothiolation: Counterion-Controlled Regioselectivity.

Abstract: In this Article, we expand upon the catalytic hydrothiolation of 1,3-dienes to afford either allylic or homoallylic sulfides with high regiocontrol. Mechanistic studies support a pathway in which regioselectivity is dictated by the choice of counterion associated with the Rh center. Non-coordinating counterions, such as SbF6-, allow for η4-diene coordination to Rh complexes and result in allylic sulfides. In contrast, coordinating counterions, such as Cl-, favor neutral Rh complexes in which the diene binds η2 to afford homoallylic sulfides. We propose mechanisms that rationalize a fractional dependence on thiol for the 1,2-Markovnikov hydrothiolation while accounting for an inverse dependence on thiol in the 3,4- anti-Markovnikov pathway. Through the hydrothiolation of an essential oil (β-farnesene), we achieve the first enantioselective synthesis of (-)-agelasidine A.