Calcium Bistriflimide-Mediated Sulfur(VI)–Fluoride Exchange (SuFEx): Mechanistic Insights toward Instigating Catalysis

Authors

Brian Han, Chapman University
Samuel R. Khasnavis, Pomona College
Matthew Nwerem, Chapman University
Michael Bertagna, Chapman University
Nicholas D. Ball, Pomona CollegeFollow
O. Maduka Ogba, Chapman UniversityFollow

Document Type

Article

Publication Date

6-14-2022

Abstract

We report a mechanistic investigation of calcium bistriflimide-mediated sulfur(VI)–fluoride exchange (SuFEx) between sulfonyl fluorides and amines. We determine the likely pre-activation resting state─a calcium bistriflimide complex with ligated amines─thus allowing for corroborated calculation of the SuFEx activation barrier at ∼21 kcal/mol, compared to 21.5 ± 0.14 kcal/mol derived via kinetics experiments. Transition state analysis revealed: (1) a two-point calcium-substrate contact that activates the sulfur(VI) center and stabilizes the leaving fluoride and (2) a 1,4-diazabicyclo[2.2.2]octane additive that provides Brønsted-base activation of the nucleophilic amine. Stable Ca–F complexes upon sulfonamide formation are likely contributors to inhibited catalytic turnover, and a proof-of-principle redesign provided evidence that sulfonamide formation is feasible with 10 mol % calcium bistriflimide.

Comments

This article was originally published in Inorganic Chemistry in 2022. https://doi.org/10.1021/acs.inorgchem.2c01230

Recommended Citation

Han, B.; Khasnavis, S. R.; Nwerem, M.; Bertagna, M.; Ball, N. D.; Ogba, O. M. Calcium Bistriflimide-Mediated Sulfur(VI)–Fluoride Exchange (SuFEx): Mechanistic Insights toward Instigating Catalysis. Inorg. Chem. 2022. https://doi.org/10.1021/acs.inorgchem.2c01230

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This work is licensed under a Creative Commons Attribution 4.0 License.