Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition
نویسندگان
چکیده
Chiral metal catalysts have been widely applied to asymmetric transformations. However, the electronic structure of the catalyst and how it contributes to the activation of the substrate is seldom investigated. Here, we report an empirical approach for providing insights into the catalytic activation process in the distorted Ni(II)-catalysed asymmetric [3+2] cycloaddition of α-ketoesters. We quantitatively characterize the bonding nature of the catalyst by means of electron density distribution analysis, showing that the distortion around the Ni(II) centre makes the dz2 orbital partially 'naked', wherein the labile acetate ligand is coordinated with electrostatic interaction. The electron-deficient dz2 orbital and the acetate act together to deprotonate the α-ketoester, generating the (Λ)-Ni(II)-enolate. The solid and solution state analyses, together with theoretical calculations, strongly link the electronic structure of the centrochiral octahedral Ni(II) complex and its catalytic activity, depicting a cooperative mechanism of enolate binding and outer sphere hydrogen-bonding activation.
منابع مشابه
An Efficient and One-pot Procedure for the Synthesis of Chiral Isoxazolidine via Catalytic Highly Enantioselective 1,3-dipolar cycloaddition
Synthesis of enantiomerically pure isoxazolidine via an asymmetric 1,3- dipolar cycloaddition reaction of nitrone with electron-deficient dipolarophile was described. The process occurs at room temperature in aqueous ethanol as a green solvent and in the presence of a bidendate bis(imine)–Cu(II)triflate complex as catalyst. The reaction mechanism is discussed on the basis of the assignment of t...
متن کاملThree-component procedure for the synthesis of new chiral spirooxindolopyrrolizidines via catalytic highly enantioselective 1,3-dipolar cycloaddition
The catalytic highly regio-, diastereo-, and enantioselective synthesis of a small library of spiropyrrolizidineoxindolesvia a four-component 1,3-dipolar cycloaddition reaction of azomethine ylides, derived from isatin, with electron-deficient dipolarophilewas described. The process occurs at room temperature in aqueous ethanol as a green solvent and in the presence of a bidendatebis(imine)–Cu(...
متن کاملEfficient Synthesis of Nickel(II) Complex Supported on Fe3O4@SiO2 Nanoparticles as a New and Facile Catalyst for Various Multicomponent Reactions
In the present work, we have planned a new magnetically recoverable nanocatalyst. The obtained nanocatalyst designated as Fe3O4@SiO2@DOPisatin-Ni (II) was characterized by FTIR, XRD, SEM, EDAX, VSM, AAS and TGA techniques. It was found that Fe3O4@SiO2@DOPisatin-Ni (II) successfully catalyses the synthesis of 2,3-dihydroquinazolin-4(1H)-ones, polyhydroquinoline and 5-substituted 1H-tetrazoles in...
متن کاملStructure and Chromotropic Properties of 2-Picolylamine-Ni(II) Complex
A symmetric complex [NiL2(H2O)2]Cl2, where L = 2-picolylamine was synthesized and characterized by spectroscopic and structural methods. Single crystal X-ray studies reveal that the Ni(II) center located in a pseudo-octahedral N4O2 environment with bidentate ligands L positioned in basal and two water molecules in the apical position. The complex is solvatochromic, ionochromic and thermochromic...
متن کاملRegioselectivie Synthesis of New Spiro-Oxindolopyrrolidines via a Three-Component Asymmetric 1,3-Dipolar Cycloaddition Reaction of Azomethine Ylides aAnd Chiral Menthyl Cinnamate
An efficient, one-pot, four-component procedure for the synthesis of a small library of new chiral spiro- oxindolopyrrolidines with high regio-, diastereo- (>99:1 dr), and enantioselectivity (up to 80% ee) is described. In this process, the regio- and stereochemical 1,3-dipolar cycloaddition of azomethine ylides, which were generated insitu by the reaction of isatin derivatives and sarcosin,wit...
متن کامل