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Published on: February 16, 2020
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Ring Opening of Diketene in Superacidic Media
Sebastian Steiner1, Ulli Blumenschein1, Zurwa M Shafiq1
1Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany.
The Journal of Organic Chemistry
|December 16, 2024
Summary
Diketene reacts in superacidic systems to form novel protonated acetoacetyl fluoride salts. These compounds exhibit unique ring-like structures and superelectrophilic properties, revealed through advanced spectroscopic and crystallographic analyses.
Area of Science:
- Superacid Chemistry
- Organic Fluorine Chemistry
- Spectroscopy and Crystallography
Background:
- Diketene is a versatile synthetic intermediate.
- Superacidic systems (HF/MF5) enable the study of highly reactive species.
- Protonation of diketene can lead to complex ionic structures.
Purpose of the Study:
- To investigate the reactions of diketene in binary superacidic systems (HF/MF5, M=As, Sb).
- To characterize the resulting protonated acetoacetyl fluoride salts.
- To elucidate the structural and electronic properties of these species.
Main Methods:
- Reactions in HF/MF5 and DF/MF5 superacidic media.
- Low-temperature vibrational spectroscopy.
- Nuclear magnetic resonance (NMR) spectroscopy.
- Single-crystal X-ray diffraction.
- Quantum chemical pKa calculations.
Main Results:
- Formation of monoprotonated and diprotonated acetoacetyl fluoride salts.
- Characterization of salts, including crystal structures of [CH3C(OH)CH2COF][SbF6]·HF and [CH3C(OH)CH2C(OH)F][SbF6]2·HF.
- Identification of a six-membered ring structure with intramolecular hydrogen bonding in the monoprotonated species.
- Description of the diprotonated species as a 1,3-gitonic superelectrophile.
Conclusions:
- Diketene undergoes controlled protonation in superacidic media to yield stable ionic compounds.
- The structural diversity, including ring formation and superelectrophilic character, is dependent on the degree of protonation.
- Spectroscopic and crystallographic data provide detailed insights into the reaction mechanisms and product structures.
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