Theoretical investigation on donor–acceptor interaction between a carbonyl compound and an <i>N</i>,<i>N</i>′-dioxide–Sc(<scp>iii</scp>) complex

Su, Zhishan; He, Weiying; Wang, Junming; Zuo, Yini; Hu, Changwei

doi:10.1039/c7ra12258f

Cited by 5 publications

(6 citation statements)

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“…The mechanism of cycloaddition between an alkynone (R1) and a cyclic enol silyl ether (R2) mediated by a chiral N,N ′-dioxide-Zn(II) complex (CAT) was further studied at the same theoretical level. On the basis of the X-ray crystal structure of the N,N ′-dioxide-Zn(II) , complex and our previous works, − a hexacoordinate Zn(II) complex was considered to be an active species. We first focused on the Zn(II) complex containing a chiral N,N ′-dioxide ligand L2 with two CH 2 groups in the linkage (see Scheme , m = 1), which was reported in experiments .…”

Section: Resultssupporting

confidence: 85%

“…Our previous studies indicated that a counterion could coordinate to the metal center of a chiral N , N ′-dioxide-metal complex, stabilizing the active species, adjusting the Lewis acidity of the metal center, and even taking part in reactions . The positive effect of the counterion NTf 2 – in alkenylsilylation reactions was also studied by Xia and co-workers. , To understand the role of the counterion NTf 2 – in [2 + 2] cycloaddition reactions, we also optimized the geometry of a pentacoordinate Zn(II) complex without an NTf 2 – anion (L2-COM-P).…”

Section: Resultsmentioning

confidence: 99%

“…Role of Counterion NTf 2 − . Our previous studies indicated that a counterion could coordinate to the metal center of a chiral N,N′-dioxide-metal complex, stabilizing the active species, 38 adjusting the Lewis acidity of the metal center, 39 and even taking part in reactions. 43 The positive effect of the counterion NTf 2 − in alkenylsilylation reactions was also studied by Xia and co-workers.…”

Section: Mechanism Of the Catalytic Reactionmentioning

confidence: 99%

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Theoretical Study on Asymmetric [2 + 2] Cycloaddition of an Alkynone with a Cyclic Enol Silyl Ether Catalyzed by a Chiral N,N′-Dioxide-Zn(II) Complex

Meng

Zuo

et al. 2019

Organometallics

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The reaction mechanism and enantioselectivity of the asymmetric [2 + 2] cycloaddition between an alkynone (R1) and a cyclic enol silyl ether (R2) were studied theoretically by the DFT method at the B3LYP-D3(BJ)/6-311G**(CH2Cl2,SMD)//B3LYP-D3(BJ)/def2-SVP(CH2Cl2,SMD) theoretical level. The noncatalytic reaction occurred via a stepwise mechanism. The first C–C bond was constructed by coupling two pseudo radical centers generated at the most nucleophilic C2 atom in the cyclic enol silyl ether and the most electrophilic terminal Cβ atom in the alkynone, which was responsible for the regioselectivity of the reaction. The counterion NTf2 – could stabilize the Zn(II) complex by coordinating to the center metal, forming a high-reactivity hexacoordinate Zn(II)-complex intermediate. The bulky CF3 group in the NTf2 – ion adjusted the blocking effect of o-iPr in aniline of the ligand toward the reactive site (that is, the Cβ atom in the alkynone) and induced the si face of the cyclic enol silyl ether to approach the alkynone from its less hindered re face, achieving a high enanotioselectivity of products. The Pauli repulsion between the Zn(II)-associated moiety and cyclic enol silyl ether fragment was the main contributor to the stereodifference of the two competing pathways in chiral N,N′-dioxide-Zn(II)-catalyzed [2 + 2] cycloaddition. The unfavorable steric repulsion between the o-iPr group of aniline in the ligand and tert-butyldimethylsilyl (TBS) in the cyclic enol silyl ether along the re face path translated into a more destabilizing ΔE Pauli value, leading to the predominant cycloaddition product (P-RR) observed in experiments. Variation of the linkage and chiral backbone could affect the repulsion among the o-iPr in the ligand, the counterion NTf2 –, and substrates, leading to different stereochemical outcomes. These results are in good agreement with experimental observations.

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Mechanism Of the Catalytic Reactionmentioning

confidence: 99%

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Theoretical Study on Asymmetric [2 + 2] Cycloaddition of an Alkynone with a Cyclic Enol Silyl Ether Catalyzed by a Chiral N,N′-Dioxide-Zn(II) Complex

Meng

Zuo

et al. 2019

Organometallics

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“…X-ray structural analysis and our previous calculations indicate that chiral N , N ′-dioxide ligand interacts with Sc 3+ metal center, forming a tetracoodinate-Sc(III) complex (CAT) with “pocketlike” chiral environment. − The chalcone substrate and counteranion OTf – from metal salt Sc(OTf) 3 could interact with the central metal Sc 3+ ion of tetradentate-Sc(III) catalyst simultaneously, forming a hexacoordinate chiral N , N ′-dioxide–Sc(III) complex (L-COM) b . Considering that there exist two possible conformations ( s - cis and s - trans ) for free chalcone substrate, s - cis -chalcone and s- trans -chalcone as well as that their corresponding Sc(III) complexes were optimized first. As shown in Table S1 of the Supporting Information (SI), s - cis -chalcone is more stable than s - trans -chalcone by 2.1 kcal mol –1 .…”

Section: Resultsmentioning

confidence: 98%

Mechanism and Origins of Stereoinduction in an Asymmetric Friedel–Crafts Alkylation Reaction of Chalcone Catalyzed by Chiral N,N′-Dioxide–Sc(III) Complex

et al. 2018

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The mechanism and selectivity of the asymmetric Friedel-Crafts (F-C) alkylation reaction between indole and chalcone catalyzed by chiral N, N'-dioxide-Sc(III) complexes were investigated at the M06/6-311+G(d,p)//M06/[LANL2DZ,6-31G(d)](SMD,CHCl) level. The reaction occurred via a three-step mechanism: (i) the C-C bond formation by interacting the most mucleophilic C center of indole with the most electrophilic C center of chalcone; (ii) the abstraction of the proton at the C atom of indole by counterion OTf; (iii) proton transfer from HOTf to the C atom of chalcone, generating the F-C alkylation product. The reaction preferred to occur along the favorable re-face attack pathway, producing the dominant R-product. The turnover frequency (TOF) of catalysis was predicted to be 1.59 × 10 s, with a rate constant of K( T) = 1.58 × 10 exp(-29057/ RT) dm·mol·s over the temperature range of 248-368 K. Activation strain model (ASM) and energy decomposition analysis (EDA), as well as noncovalent interaction (NCI) analysis, for the stereocontrolling transition state revealed that the substituent attached to the N atom of the amide subunits as well as the amino acid backbone of ligand played important roles in chiral inductivity. The benzyl group with structural flexibility tended to form strong π-π stacking with substrate as well as the terminal phenyl group of chalcone, stabilizing re-face attack transition state.

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“…It is interesting to note that, HOMO‐LUMO energy gap depicts a major stability index [56] . The applications of frontier molecular orbital afford helpful information towards donor acceptor interaction, in which molecular properties has been accociated with molecular orbital energies whereas orbital densities pinpoint atomic properties [57] . As a result, when HOMO and LUMO orbitals reach the maximum overlap, the chemical reaction takes place as claimed by frontier electron reactivity theory [58] .…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Optical and Electrochemical Properties of Novel Formazan Analogs Incorporated Fluorene Moiety

Guesmi

2023

ChemistrySelect

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A series of novel formazan analogs 4 a–e, having MeO, Me, Cl, NO2 at para/meta‐position in 1‐phenyl ring was synthesized by treatment of 9‐fluorenone hydrazone 2 with a series of the hydrazonoyl chlorides 3 a–e. The molecular structure elucidation of all newly synthesized formazans was achieved by using elemental analyses as well as spectroscopic tools. The substituent and solvatochromic effects of formazan derivatives in seventeen solvents with different chemical and physical properties were investigated by absorption spectroscopy. A small band shift is obtained in the absorption maxima as a function of solvent, displaying a less sensitivity of compounds 4 a–e to solvent polarity. A noticeable variation in the absorption maxima (λmax) values was observed by modifying the electronic characteristic and positions of the substituents. Furthermore, the electrochemical properties were adressed by cyclic voltammetry measurements, and the influence of electron‐donating and withdrawing nature of the substituents on electrochemical properties of formazan derivatives has been studied. In addition, computational studies on the formazan structures were performed using B3LYP functional in DFT method at the 6‐31G(d,p) basis set, and the energy values related to their frontier orbitals (HOMO,LUMO) were estimated. A variety of reactivity descriptors, namely, ionization potential (IP), electron affinity (EA), hardness (η), softness (S), chemical potential (μ), electronegativity (χ) and electrophilicity index (ω) have been determined via energies values of HOMO and LUMO. The experimental data and theoretical results showed a good correlation.

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Theoretical investigation on donor–acceptor interaction between a carbonyl compound and an N,N′-dioxide–Sc(iii) complex

Abstract: The counterion and substituent on amide of the N,N′-dioxide ligand could affect electrostatic energy (ΔVelstat) as well as orbital energy (ΔEorb) between CH2O and Sc(iii)-based catalyst, adjusting the Lewis acidity of the metal centre.

Cited by 5 publications

References 56 publications

Theoretical Study on Asymmetric [2 + 2] Cycloaddition of an Alkynone with a Cyclic Enol Silyl Ether Catalyzed by a Chiral N,N′-Dioxide-Zn(II) Complex

Theoretical Study on Asymmetric [2 + 2] Cycloaddition of an Alkynone with a Cyclic Enol Silyl Ether Catalyzed by a Chiral N,N′-Dioxide-Zn(II) Complex

Mechanism and Origins of Stereoinduction in an Asymmetric Friedel–Crafts Alkylation Reaction of Chalcone Catalyzed by Chiral N,N′-Dioxide–Sc(III) Complex

Synthesis, Optical and Electrochemical Properties of Novel Formazan Analogs Incorporated Fluorene Moiety

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