Quantitative aspects of Lewis acidity. Part VIII. The validity of infrared carbonyl shifts as measures of Lewis acid strength. The interaction of Lewis acids and phenalen-1-one(perinaphthenone)

1967 ◽  
pp. 723 ◽  
Author(s):  
Ali Mohammad ◽  
D. P. N. Satchell ◽  
R. S. Satchell
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Strength ◽  
Lewis Acidity

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.

A Practical Method for Regioselective 5′-O-tert-Butyldimethylsilyl Deprotection of Persilylated Nucleosides by Methanolic Phosphomolybdic Acid

Synlett ◽  
2018 ◽  
Vol 29 (18) ◽  
pp. 2437-2443
Author(s):  
Shan-Shan Gong ◽  
Qi Sun ◽  
Hua-Shan Huang ◽  
Rui Kong ◽  
Xiu-An Zheng ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Lewis Acid ◽  
31P Nmr ◽  
Practical Method ◽  
Phosphomolybdic Acid ◽  
Acid Strength ◽  
Lewis Acidity ◽  
Anion Cluster ◽  
Practical Synthesis

In nucleoside/nucleotide chemistry, the regioselective cleavage of 5′-O-TBS groups of persilylated nucleosides is a desired approach for structural functionalization at the 5′-position. However, efficient and practical methods for this purpose are still limited. In our research, we found that homogeneous methanolic phosphomolybdic acid (PMA) efficiently catalyzes the regioselective deprotection of 5′-O-TBS groups of a diversity of persilylated nucleoside substrates and can be applied in practical synthesis at scales of up to 15 g. 31P NMR results indicated that an anion cluster forms and the Lewis acidity of homogeneous PMA is organic-solvent dependent. The efficacy and pronounced regioselectivity of methanolic PMA occurs as a result of a lowering of the Lewis acid strength upon solvation of the molybdophosphate anions.

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.

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.

scholarly journals Hydrogen activation using a novel tribenzyltin Lewis acid

2017 ◽  
Vol 375 (2101) ◽  
pp. 20170008 ◽  
Author(s):  
Robert T. Cooper ◽  
Joshua S. Sapsford ◽  
Roland C. Turnell-Ritson ◽  
Dong-Hun Hyon ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Low Temperature ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Lewis Acidity ◽  
The Novel ◽  
Hydrogen Activation ◽  
Frustrated Lewis Pair

Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. Despite this, the Lewis acids (LAs) in these transformations are often boranes, with heavier p -block elements receiving surprisingly little attention. The novel LA Bn 3 SnOTf ( 1 ) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R 3 SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R 3 Sn + LA core have also been investigated. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.

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.

Homologation of Alkyl Acetates, Alkyl Ethers, Acetals and Ketals by Formal Insertion of Diazo Compounds into a Carbon-Carbon Bond

Synthesis ◽  
2021 ◽  
Author(s):  
Fei Wang ◽  
Junyi Yi ◽  
Yoshihiro Nishimoto ◽  
Makoto Yasuda
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Diazo Compounds ◽  
Lewis Acidity ◽  
Carbon Carbon Bond ◽  
Leaving Group ◽  
Diazo Esters ◽  
Alkyl Ethers ◽  
Alkyl Acetates ◽  
Leaving Groups

We have accomplished homologation of alkyl acetates, alkyl ethers, acetals, and ketals via formal insertion of diazo esters into carbon-carbon σ-bonds. The combined Lewis acid of InI3 with Me3SiBr catalyzed the homologation of alkyl acetates and alkyl ethers. That of acetals and ketals was catalyzed solely by the use of InBr3. The key point of the homologation mechanism is that the indium-based Lewis acids have the appropriate amount of Lewis acidity to achieve both the abstraction and release of leaving groups. The abstraction of a leaving group by an indium-based Lewis acid, the electrophilic addition of carbocation or oxonium intermediates to diazo esters followed by the rearrangement of carbon substituents provides the corresponding cation intermediates. Finally, the leaving group that is captured by the Lewis acid bonds with cation intermediates to furnish the homologated products.

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