Tuning the reduction potentials of benzoquinone through the coordination to Lewis acids

2021 ◽  
Vol 23 (16) ◽  
pp. 9822-9831
Author(s):  
Brena L. Thompson ◽  
Zachariah M. Heiden
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Computational Study ◽  
Acid Strength ◽  
Reduction Potentials

This computational study investigates the nature of the interaction between benzoquinone and one and two Lewis acids by examining the influence of Lewis acid strength on the ability to alter the two reduction potentials of the coordinated benzoquinone molecule.

Fluorinated 9-borafluorenes vs. conventional perfluoroaryl boranes — Comparative Lewis acidity

2005 ◽  
Vol 83 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Preston A Chase ◽  
Patricio E Romero ◽  
Warren E Piers ◽  
Masood Parvez ◽  
Brian O Patrick
Keyword(s):  
Key Words ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Strength ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Electrochemical Studies ◽  
Steric Factors

Perfluorinated 9-phenyl-9-borafluorene, 1, is an antiaromatic analog of the well-known tris(pentafluorophenyl)borane. Spectroscopic, structural, and electrochemical studies have been performed on 1 and its Lewis base adducts with MeCN, THF, and PMe3 with a view to assessing its comparative Lewis acid strength relative to B(C6F5)3. For the sterically undemanding Lewis base MeCN, 1 and B(C6F5)3 have comparable LA strengths, while for more sterically prominent THF, 1 is clearly the stronger Lewis acid (LA) based on competition experiments. We conclude that steric factors, rather than antiaromaticity, are the most important determinants in the LA strength differences between 1 and B(C6F5)3.Key words: boranes, Lewis acids, fluorinated compounds, heterocycles.

Lewis Acid Coordination Redirects S-Nitrosothiol Reduction

2020 ◽  
Author(s):  
Valiallah Hosseininasab ◽  
Alison C. McQuilken ◽  
Abolghasem (Gus) Bakhoda ◽  
Jeffery A. Bertke ◽  
Qadir K. Timerghazin ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Reduction Potential ◽  
Chemical Reduction ◽  
Physiological Responses ◽  
Outer Sphere ◽  
Intramolecular Electron Transfer ◽  
Computational Studies ◽  
Reduction Potentials ◽  
Initial Reduction

<i>S</i>-Nitrosothiols (RSNOs) serve as air-stable reservoirs for nitric oxide in biology and are responsible for a myriad of physiological responses. While copper enzymes promote NO release from RSNOs by serving as Lewis acids capable of intramolecular electron-transfer, redox innocent Lewis acids separate these two functions to reveal the effect of coordination on structure and reactivity. The synthetic Lewis acid B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinates to the RSNO oxygen atom in adducts RSNO-B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, leading to profound changes in the RSNO electronic structure and reactivity. Although RSNOs possess relatively negative reduction potentials (-1.0 to -1.1 vs. NHE), B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordination increases their reduction potential by over 1 V into the physiologically accessible +0.1 V vs. NHE. Outer-sphere chemical reduction results in formation of the Lewis acid stabilized hyponitrite dianion <i>trans</i>-[LA–O–N=N–O–LA]<sup>2–</sup> (LA = B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>) that releases N<sub>2</sub>O upon acidification. Mechanistic and computational studies support initial reduction to the [RSNO-B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>]<sup>•/- </sup>radical-anion susceptible to N-N coupling prior to loss of RSSR.

INFRARED SPECTRA OF COMPLEXES OF 4-PYRIDONES

1963 ◽  
Vol 41 (2) ◽  
pp. 515-521 ◽  
Author(s):  
Denys Cook
Keyword(s):  
Nitrogen Atom ◽  
Carbonyl Group ◽  
Lewis Acid ◽  
Infrared Spectra ◽  
Lewis Acids ◽  
Donor Site ◽  
Acid Strength ◽  
Ring Mode ◽  
Lower Frequencies

The infrared spectra of many complexes of Lewis acids with some 4-pyridones have been recorded. Large shifts to lower frequencies of about 100 cm−1 have been observed in a band near 1560 cm−1 as the Lewis acid strength increased. Much smaller shifts of about 5 to 10 cm−1 in a band near 1640 cm−1 were noted. The former band has therefore been designated as the carbonyl frequency, and the latter as a ring mode involving CC stretching.The donor site of 4-pyridones is therefore the carbonyl group, and not the nitrogen atom. Protonated 4-pyridones have similar spectra, and are consistent with O-, not N-protonation.

INFRARED SPECTRA OF XANTHONE: LEWIS ACID COMPLEXES

1963 ◽  
Vol 41 (2) ◽  
pp. 522-526 ◽  
Author(s):  
Denys Cook
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Quantitative Estimate ◽  
Donor Site ◽  
Carbonyl Oxygen ◽  
Acid Strength ◽  
Carbonyl Groups ◽  
Wide Range ◽  
Stretching Vibration ◽  
Solid Complexes

Xanthone, a member of the γ-pyrone species, which have basic carbonyl groups, forms an excellent series of solid complexes with Lewis acids. In these complexes the carbonyl oxygen atom is the donor site, and the carbonyl stretching vibration moves to progressively lower frequency as the Lewis acid strength increases. The carbonyl frequency in the BI3 complex, 1400 cm−1, is one of the lowest encountered in complexes of this type.The wide range of Lewis acids used to form these complexes has enabled a quantitative estimate of the Lewis acid strength to be made, which compares reasonably well with previous estimates.

Lewis Acid Coordination Redirects S-Nitrosothiol Reduction

2020 ◽  
Author(s):  
Valiallah Hosseininasab ◽  
Alison C. McQuilken ◽  
Abolghasem (Gus) Bakhoda ◽  
Jeffery A. Bertke ◽  
Qadir K. Timerghazin ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Reduction Potential ◽  
Chemical Reduction ◽  
Physiological Responses ◽  
Outer Sphere ◽  
Intramolecular Electron Transfer ◽  
Computational Studies ◽  
Reduction Potentials ◽  
Initial Reduction

<i>S</i>-Nitrosothiols (RSNOs) serve as air-stable reservoirs for nitric oxide in biology and are responsible for a myriad of physiological responses. While copper enzymes promote NO release from RSNOs by serving as Lewis acids capable of intramolecular electron-transfer, redox innocent Lewis acids separate these two functions to reveal the effect of coordination on structure and reactivity. The synthetic Lewis acid B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordinates to the RSNO oxygen atom in adducts RSNO-B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>, leading to profound changes in the RSNO electronic structure and reactivity. Although RSNOs possess relatively negative reduction potentials (-1.0 to -1.1 vs. NHE), B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> coordination increases their reduction potential by over 1 V into the physiologically accessible +0.1 V vs. NHE. Outer-sphere chemical reduction results in formation of the Lewis acid stabilized hyponitrite dianion <i>trans</i>-[LA–O–N=N–O–LA]<sup>2–</sup> (LA = B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>) that releases N<sub>2</sub>O upon acidification. Mechanistic and computational studies support initial reduction to the [RSNO-B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>]<sup>•/- </sup>radical-anion susceptible to N-N coupling prior to loss of RSSR.

Lewis Acid-Promoted Suzuki Reaction using Palladium Chloride Anchored on a Polymer as a Catalyst

2008 ◽  
Vol 61 (8) ◽  
pp. 610 ◽  
Author(s):  
Guozhi Fan ◽  
Hanjun Zhang ◽  
Siqing Cheng ◽  
Zhandong Ren ◽  
Zhijun Hu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Heterogeneous Catalysts ◽  
Suzuki Reaction ◽  
Cross Coupling ◽  
Palladium Chloride ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Recoverable Catalyst

Palladium chloride anchored on polystyrene modified by 5-amino-1,10-phenanthroline was prepared and used as an efficient recoverable catalyst for Suzuki cross-coupling reactions. The heterogeneous catalysts can be easily separated from the reaction mixture and reused for five cycles without significant Pd leaching and loss of catalytic activity. Rate enhancement in the Suzuki reaction by Lewis acids was also studied.

Synthesis of pyrrolo[1,2-a]naphthyridines by Lewis acid mediated cycloisomerization

2017 ◽  
Vol 15 (15) ◽  
pp. 3216-3231 ◽  
Author(s):  
Anika Flader ◽  
Silvio Parpart ◽  
Peter Ehlers ◽  
Peter Langer
Keyword(s):  
Lewis Acid ◽  
Lewis Acids

Functionalized pyrrolo[1,2-a]naphthyridines were synthesized by application of PtCl2 and Bi(OTf)3 as simple Lewis acids in a cycloisomerization reaction.

Lewis Acid Behavior of SF4: Synthesis, Characterization, and Computational Study of Adducts of SF4with Pyridine and Pyridine Derivatives

2015 ◽  
Vol 21 (16) ◽  
pp. 6247-6256 ◽  
Author(s):  
Praveen Chaudhary ◽  
James T. Goettel ◽  
Hélène P. A. Mercier ◽  
Shahin Sowlati-Hashjin ◽  
Paul Hazendonk ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Computational Study ◽  
Pyridine Derivatives
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