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Acid Activation in Phenyliodine Dicarboxylates: Direct Observation, Structures, and Implications
Susana Izquierdo1, Stéphanie Essafi2, Iker Del Rosal2
1Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology , 43007, Tarragona, Spain.
Hypervalent iodine reagents, crucial for organic synthesis, are activated by acids. This study elucidates the mechanism of this activation using PhI(OAc)2 and BF3·Et2O, revealing structural and electronic insights into enhanced reactivity.
Area of Science:
- Organic Synthesis
- Hypervalent Iodine Chemistry
- Catalysis
Background:
- Hypervalent iodine reagents are widely used in oxidative processes.
- Acidic additives (Lewis or Brønsted) enhance the reactivity of λ³-iodanes.
- The precise mechanism of this acid-induced activation remains poorly understood.
Purpose of the Study:
- To investigate the activation mechanism of hypervalent iodine reagents by acids.
- To explore the interaction between PhI(OAc)2 and BF3·Et2O.
- To elucidate the structural and electronic factors responsible for enhanced reactivity.
Main Methods:
- Spectroscopic analysis to study the dynamic acid-base interaction.
- Isolation and X-ray diffraction of the PhI(OAc)2-BF3 complex.
- Density Functional Theory (DFT) calculations for electronic structure analysis.
Main Results:
- The PIDA·BF3 complex was successfully isolated and its structure determined.
- Spectroscopic data confirmed the dynamic acid-base interaction between the reagent and Lewis acid.
- DFT calculations provided insights into the electronic redistribution and structural changes upon activation.
Conclusions:
- The study provides the first structural evidence of an acid-iodane complex.
- The findings clarify the origin of enhanced reactivity in acid-activated hypervalent iodine systems.
- This work deepens the understanding of catalytic activation mechanisms in organic synthesis.
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