The Proton Sponge Effect: Substitution of Quino[7,8‐<i>h</i>]quinoline and the First Structurally Characterised Derivatives

Shaffer, Karl J.; Parr, Daniel C.; Wenzel, Marco; Rowlands, Gareth J.; Plieger, Paul G.

doi:10.1002/ejoc.201201131

Cited by 13 publications

(25 citation statements)

References 27 publications

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“…To prepare 1,10-phenanthrolines we first attempted to adopt a one-step Skraup-Doebner-Miller cyclocondensation of ortho -phenylenediamines 1 with unsaturated carbonyl compounds. However, like in previous work by other authors, this procedure failed, possibly due to an intermolecular condensation [26]. Instead, the synthesis of 4,7-dichloro-1,10-phenanthroline derivatives 4 has been carried out using a three-step condensation of 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid), orthoesters, and ortho -phenylenediamines 1 (Scheme 1) [22,23].…”

Section: Resultssupporting

confidence: 59%

Synthesis and Electrochemical and Spectroscopic Characterization of 4,7-diamino-1,10-phenanthrolines and Their Precursors

et al. 2019

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New approaches to the synthesis of 4,7-dichloro-1,10-phenanthrolines and their corresponding 9H-carbazol-9-yl-, 10H-phenothiazin-10-yl- and pyrrolidin-1-yl derivatives were developed. Their properties have been characterized by a combination of several techniques: MS, HRMS, GC-MS, electronic absorption spectroscopy and multinuclear NMR in both solution and solid state including 15N CP/MAS NMR. The structures of 5-fluoro-2,9-dimethyl-4,7-di(pyrrolidin-1-yl)-1,10-phenanthroline (5d), 4,7-di(9H-carbazol-9-yl)-9-oxo-9,10-dihydro-1,10-phenanthroline-5-carbonitrile (6a) and 4,7-di(10H-phenothiazin-10-yl)-1,10-phenanthroline-5-carbonitrile (6b) were determined by single-crystal X-ray diffraction measurements. The nucleophilic substitutions of hydrogen followed by oxidation produced compounds 6a and 6b. The electrochemical properties of selected 1,10-phenanthrolines were investigated using cyclic voltammetry and compared with commercially available reference 1,10-phenanthrolin-5-amine (5l). The spatial distribution of frontier molecular orbitals of the selected compounds has been calculated by density functional theory (DFT). It was shown that potentials of reduction and oxidation were in consistence with the level of HOMO and LUMO energies.

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Section: Resultssupporting

confidence: 59%

Synthesis and Electrochemical and Spectroscopic Characterization of 4,7-diamino-1,10-phenanthrolines and Their Precursors

et al. 2019

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“…(PHFX) 2 homodimers], varying between 2.62-3.04 Å, and 2.82-3.13 Å for phosphor and arsenic derivatives, respectively. (PHFX) 2 homodimers], varying between 2.62-3.04 Å, and 2.82-3.13 Å for phosphor and arsenic derivatives, respectively.…”

Section: Discussionmentioning

confidence: 99%

Intramolecular pnicogen interactions in phosphorus and arsenic analogues of proton sponges

Sánchez‐Sanz

Trujillo

Alkorta

et al. 2014

Phys. Chem. Chem. Phys.

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A computational study of the intramolecular pnicogen bond in 1,8-bis-substituted naphthalene derivatives (ZXH and ZX2 with Z = P, As and X = H, F, Cl, and Br), structurally related to proton sponges, has been carried out. The aim of this paper is the study of their structural parameters, interaction energies and electronic properties such as electron density on the intramolecular interaction. The calculated geometrical parameters associated to the P···P interaction are in reasonably good agreement with the crystal structures found in a CSD search, in particular those of the halogen derivatives. Isodesmic reactions where the 1,8-bis-substituted derivatives are compared to monosubstituted derivatives have been calculated, indicating that the 1,8 derivatives are more stable than the monosubstituted ones for those cases with X-Z···Z-X and F-Z···Z-H alignments. Electron densities and Laplacians at the BCP on the pnicogen interactions suggest that they can be classified as pure closed shell interactions with a partial covalent character. Electron density shift maps are consistent with the results for intermolecular pnicogen interactions. Relationships between interatomic distance and electron density at the bond critical points and between interatomic distance and the orbital charge transfer stabilization energies have been found.

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“…Besides the replacement of DMAN's methyl groups by numerous different alkyl substituents, [17][18][19] the nitrogen atoms have been integrated in an aromatic system as for instance shown in Staab's quino- [7,8h]quinoline. [20] This structure motive was recently further modified by Shaffer et al [21] Apart from varying the substituents of DMAN, several proton-chelating compounds with backbones other than naphthalene have been synthesized. The interaction of two basicity centers has also been achieved by aromatic spacers such as fluorene, [22] heterofluorene, [23] phenantrene, [24] biphenyl [25] or helicene [26] moieties.…”

Section: Introductionmentioning

confidence: 99%

“…Besides the replacement of DMAN’s methyl groups by numerous different alkyl substituents,17–19 the nitrogen atoms have been integrated in an aromatic system as for instance shown in Staab’s quino[7,8 h ]quinoline 20. This structure motive was recently further modified by Shaffer et al 21. Apart from varying the substituents of DMAN, several proton‐chelating compounds with backbones other than naphthalene have been synthesized.…”

Section: Introductionmentioning

confidence: 99%

Superbasic Alkyl‐Substituted Bisphosphazene Proton Sponges: Synthesis, Structural Features, Thermodynamic and Kinetic Basicity, Nucleophilicity and Coordination Chemistry

Kögel

Xie

Baal

et al. 2014

Chemistry A European J

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Herein we describe an easily accessible class of superbasic proton sponges based on the 1,8-bisphosphazenylnaphthalene (PN) proton pincer motif and P-alkyl substituents ranging from methyl (TMPN) to n-butyl (TBPN), isopropyl (TiPrPN) and cyclopentyl (TcyPPN). These neutral bases with a pK(BH)(+) value (MeCN) of ~30 were accessible via a Kirsanov condensation using commercially available 1,8-diaminonaphthalene, and in case of TMPN and TBPN, simple one-pot procedures starting from trisalkylphosphanes can be performed. Furthermore, the known pyrrolidinyl-substituted superbase TPPN previously synthesized via a Staudinger reaction could also be prepared by the Kirsanov strategy allowing its preparation in a larger scale. The four alkyl-substituted proton sponges were structurally characterized in their protonated form; molecular XRD structures were also obtained for unprotonated TiPrPN and TcyPPN. Moreover, we present a detailed description of spectroscopic features of chelating bisphosphazenes including TPPN and its hyperbasic homologue P2-TPPN on which we reported recently. The four alkyl-substituted superbases were investigated with respect to their basic features by computational means and by NMR titration experiments revealing unexpectedly high experimental pK(BH)(+) values in acetonitrile between 29.3 for TMPN and 30.9 for TBPN. Besides their thermodynamic basicity, we exemplarily studied the kinetic basicity of TMPN and TPPN by means of NMR-spectroscopic methods. Furthermore, the competing nucleophilic versus basic properties were examined by reacting the proton sponges with ethyl iodide. Insight into the coordination chemistry of chelating superbases was provided by reacting TMPN with trimethylaluminum and trimethylgallium to give cationic complexes of Group XIII metal alkyls that were structurally characterized.

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The Proton Sponge Effect: Substitution of Quino[7,8‐h]quinoline and the First Structurally Characterised Derivatives

Cited by 13 publications

References 27 publications

Synthesis and Electrochemical and Spectroscopic Characterization of 4,7-diamino-1,10-phenanthrolines and Their Precursors

Synthesis and Electrochemical and Spectroscopic Characterization of 4,7-diamino-1,10-phenanthrolines and Their Precursors

Intramolecular pnicogen interactions in phosphorus and arsenic analogues of proton sponges

Superbasic Alkyl‐Substituted Bisphosphazene Proton Sponges: Synthesis, Structural Features, Thermodynamic and Kinetic Basicity, Nucleophilicity and Coordination Chemistry

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