Electrostatically Enhanced 3- and 4‑Pyridyl Borate Salt Nucleophiles and Bases

A variety of electrostatically enhanced 3- and 4-pyridylborate salt catalysts are reported and show significant improvement over an activated noncharged neutral control compound. Their nucleophilicity in a stoichiometric SN2 reaction and catalytic performance in a urethane synthesis are evaluated al...

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Bibliographic Details
Published inJournal of organic chemistry Vol. 88; no. 15; pp. 10525 - 10538
Main Authors Dempsey, Stephen H., Lovstedt, Alex, Kass, Steven R.
Format Journal Article
LanguageEnglish
Published WASHINGTON American Chemical Society 04.08.2023
Amer Chemical Soc
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
DENSITY FUNCTIONALS
ALCOHOLS
DEPROTONATION
KINETICS
ORGANOCATALYSIS
CHIRAL GUANIDINE
ACYL TRANSFER
METAL-FREE
CATALYSTS
DISCOVERY
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Summary:A variety of electrostatically enhanced 3- and 4-pyridylborate salt catalysts are reported and show significant improvement over an activated noncharged neutral control compound. Their nucleophilicity in a stoichiometric SN2 reaction and catalytic performance in a urethane synthesis are evaluated along with three methods for rapidly evaluating the basicity of these species. That is, qualitative titrations in CH2Cl2 and CHCl3 were carried out, two separate solution-state IR studies in CCl4 and CDCl3 are reported, and the proton affinities of the anionic components of the salts were computed. Charge differences between the anion and its protonated zwitterionic conjugate acid are evaluated along with the highest occupied molecular orbitals of the anions in relationship to some of the surprising reactivity findings that were observed in the two kinetic studies.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.3c00523