Design of Robust Organosuperbases and Anion Receptors by Combination of Azine Heterocycle Skeleton and Phosphazene Motif

Khademloo, Elham; Saeidian, Hamid; Mirjafary, Zohreh; Aliabad, Javad Mokhtari

doi:10.1002/slct.201803958

Cited by 9 publications

(4 citation statements)

References 38 publications

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“…The addition of one or two substituents such as Me, NR 2 , and N=A(NR 2 ) n at the C atoms of the cyclopropene ring in the parent systems I.1 and II.1 ( Figure 1 ), influences the distribution of all labile n- and π-electrons in monosubstituted ( I.2-I.7 and II.2-II.7 ) and unsymmetrically disubstituted derivatives ( I.8-I.11 and II.8-II.11 ) investigated in this work, as in the symmetrically disubstituted derivatives ( I.12-I.17 and II.12-II.17 ) already studied in Part I [ 9 ]. The pushing effects of the amino, guanidino, and phosphazeno groups have been documented for other π-electron N-bases, their structures and thermochemical properties (particularly for imines) [ 1 , 2 , 4 , 5 , 31 , 32 , 33 ]. In the case of nitriles with the methylenecyclopropene and cyclopropenimine transmitters, the pushing effects of NR 2 and N=A(NR 2 ) n can be qualitatively illustrated by various resonance structures that can be written for their neutral and protonated forms ( Schemes S2 and S3 in SM ).…”

Section: Resultsmentioning

confidence: 99%

Nitriles with High Gas-Phase Basicity—Part II Transmission of the Push–Pull Effect through Methylenecyclopropene and Cyclopropenimine Scaffolds Intercalated between Different Electron Donor(s) and the Cyano N-Protonation Site

et al. 2022

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This work extends our earlier quantum chemical studies on the gas-phase basicity of very strong N-bases to two series of nitriles containing the methylenecyclopropene and cyclopropenimine scaffolds with dissymmetrical substitution by one or two electron-donating substituents such as Me, NR2, N=C (NR2)2, and N=P (NR2)3, the last three being strong donors. For a proper prediction of their gas-phase base properties, all potential isomeric phenomena and reasonable potential protonation sites are considered to avoid possible inconsistencies when evaluating the energetic parameters and associated protonation or deprotonation equilibria B + H+ = BH+. More than 250 new isomeric structures for neutral and protonated forms are analyzed. The stable structures are selected and the favored ones identified. The microscopic (kinetic) gas-phase basicity parameters (PA and GB) corresponding to N sites (cyano and imino in the cyclopropenimine or in the substituents) in each isomer are calculated. The macroscopic (thermodynamic) PAs and GBs, referring to the isomeric mixtures of favored isomers, are also estimated. The total (pushing) substituent effects are analyzed for monosubstituted and disubstituted derivatives containing two identical or two different substituents. Electron delocalization is examined in the two π–π conjugated transmitters, the methylenecyclopropene and cyclopropenimine scaffolds. The aromatic character of the three-membered ring is also discussed.

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Section: Resultsmentioning

confidence: 99%

Nitriles with High Gas-Phase Basicity—Part II Transmission of the Push–Pull Effect through Methylenecyclopropene and Cyclopropenimine Scaffolds Intercalated between Different Electron Donor(s) and the Cyano N-Protonation Site

et al. 2022

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“…Very recently, bifunctional (thio)urea-phosphazene catalysts were used in ROP of d,l-LA, δVL, and εCL [192]. Note that quantum chemical methods were successfully applied for the design of novel phosphazene catalysts in terms of Brønsted basicity [193,194]. We believe that DFT modeling could also be usefully extended to phosphazene-catalyzed ROP of different substrates.…”

Section: Phosphazenes: a Regrettable Lacuna In Dft Modelingmentioning

confidence: 99%

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Nifant’ev

Ivchenko

2019

Polymers

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Organocatalysis is highly efficient in the ring-opening polymerization (ROP) of cyclic esters. A variety of initiators broaden the areas of organocatalysis in polymerization of different monomers, such as lactones, cyclic carbonates, lactides or gycolides, ethylene phosphates and phosphonates, and others. The mechanisms of organocatalytic ROP are at least as diverse as the mechanisms of coordination ROP; the study of these mechanisms is critical in ensuring the polymer compositions and architectures. The use of density functional theory (DFT) methods for comparative modeling and visualization of organocatalytic ROP pathways, in line with experimental proof of the structures of the reaction intermediates, make it possible to establish these mechanisms. In the present review, which continues and complements our recent manuscript that focused on DFT modeling of coordination ROP, we summarized the results of DFT modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification. 4 of 49 were found to be polymerizable due to strain in the ester group. In addition, the predominance of high-energy coiled conformations in linear homopolymers the formed from PDO, εCL and GL was proportionately less than extended conformations, in comparison to the inactive monomer γBL. However, while the prevalence of coiled conformations over extended conformations was expected for poly(LA), this factor does not affected the reactivity of lactides. Very good agreement between the experimental and calculated data for ROP of GL, l-LA and (R,S)-lactide [47] should be separately noted. 4-(Dimethylamino)pyridine (DMAP) and Related CompoundsDMAP was the first employed organocatalyst in polymer synthesis. In 2001, Nederberg et al. [48] reported the "first organocatalytic living polymerization" (Ð M < 1.2) of L-lactide (l-LA) mediated by DMAP or 4-pyrrolidinopyridine in the presence of ROH initiators. Four years later [49], Feng and Dong reported polymerization of ε-caprolactone (εCL) catalyzed by DMAP in the presence of chitozane as an initiator. Bourissou et al. studied the mechanism of DMAP-catalyzed ROP of l-LA and five-membered lactic O-carboxylic anhydride (lacOCA) [50]. Two possible reaction pathways were analyzed at the B3LYP/6-31G(d) level of theory [39,40,51]; the solvent effect of dichloromethane was taken into account through the PCM/SCRF model [52]. The modeled reaction was the methanolysis of l-LA or lacOCA; alternative nucleophilic/monomer (Scheme 1a) and basic/alcohol (Scheme 1b) activation mechanisms were proposed for these reactions, and then analyzed by DFT optimization of the key reaction intermediates and transition states, if necessary. Scheme 1. Schematic representation of the nucleophilic/monomer (a) and basic/alcohol (b) mechanisms for (Dimethylamino)pyridine (DMAP)-catalyzed methanolysis of l-LA. Author Contributions: Conceptualization, P.I.; Methodology, I.N. and P.I.; Writing-Original draft preparation, P.I.; Writing-Review and editing, I.N. and P.I.; V...

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“…[ 2–5 ] The other organosuperbases that are not naphthalene based were also examined experimentally and computationally. [ 6–17 ] Some of the introduced superbases meet much higher basicity than DMAN, which is mainly due to the unique stability of their conjugate acids. In general, stability and positive charge delocalization in the conjugate acid of the base are provided by the solvation, resonance, IHBs, and use of electron‐donating groups.…”

Section: Introductionmentioning

confidence: 99%

Substituted ketenes offer exceptional carbon bases in gas phase: Computational study by density functional theory method

Golpayegani

Mirjafary

Saeidian

et al. 2020

J of Physical Organic Chem

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In the present study, ketene derivatives with cyclopropene and methylenecyclopropene substituents have been investigated by B3LYP/6‐311+G(d,p) level of theory to evaluate their suitability as powerful carbon superbases. The protonation at C (sp) site provides new neutral organic bases with proton affinities (PAs) = 879–1,218 kJ/mol, in which some are more basic than 1,8‐bis(dimethylamino)‐naphthalene, whose gas‐phase PA of 1,028 kJ/mol is considered the threshold of superbasicity. The PAs of designed ketenes were amplified by substitution of electron‐releasing groups such as methyl and dimethylamino on the molecular framework. Two indices of aromaticity, nucleus‐independent chemical shift and harmonic oscillator model of aromaticity, were also used for elucidation of ketene basicity, which reveals that a cyclopropene ring on the proposed ketene derivatives becomes aromatic upon protonation.

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Design of Robust Organosuperbases and Anion Receptors by Combination of Azine Heterocycle Skeleton and Phosphazene Motif

Cited by 9 publications

References 38 publications

Nitriles with High Gas-Phase Basicity—Part II Transmission of the Push–Pull Effect through Methylenecyclopropene and Cyclopropenimine Scaffolds Intercalated between Different Electron Donor(s) and the Cyano N-Protonation Site

Nitriles with High Gas-Phase Basicity—Part II Transmission of the Push–Pull Effect through Methylenecyclopropene and Cyclopropenimine Scaffolds Intercalated between Different Electron Donor(s) and the Cyano N-Protonation Site

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Substituted ketenes offer exceptional carbon bases in gas phase: Computational study by density functional theory method

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