Title

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

Researcher ORCID Identifier

0000-0002-6816-1113

Document Type

Article

Department

Chemistry (Pomona)

Publication Date

6-12-2022

Keywords

Anions, calcium bistriflimide, S(VI) fluoride, SuFEx, computational chemistry, transition states, kinetics, catalysis

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.

Terms of Use & License Information

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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