Electro-conversion of cumene into acetophenone using boron-doped diamond electrodes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-09-07 |
| Journal | Beilstein Journal of Organic Chemistry |
| Authors | Mana Kitano, Tsuyoshi Saitoh, Shigeru Nishiyama, Yasuaki Einaga, Takashi Yamamoto |
| Institutions | Keio University, Tsukuba International University |
| Citations | 6 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a sustainable and straightforward electro-conversion of cumene into acetophenone using Boron-Doped Diamond (BDD) electrodes, leveraging the materialâs unique electrochemical properties.
- Core Achievement: Direct, catalyst-free electro-oxidation of cumene (1) to acetophenone (3), a key industrial intermediate.
- Material Necessity: BDD electrodes are essential because their wide potential window enables the direct anodic oxidation of cumene, which occurs at a high potential (2.40 V vs Ag/Ag+). Conventional electrodes (Graphite, Ni) fail this conversion.
- Optimum Yield: An isolated yield of 34% for acetophenone was achieved under undivided cell conditions using Et4NClO4 as the supporting electrolyte.
- Green Chemistry: The protocol utilizes electricity as the sole oxidizing and reducing reagent, eliminating catalyst waste, avoiding harsh conditions (high temperature/pressure), and simplifying scale-up.
- Mechanism Insight: The reaction proceeds via the anodic generation of the cumyl cation intermediate, followed by reaction with cathodically generated hydroperoxide anion (derived from dissolved oxygen reduction).
- Process Simplicity: The reaction is performed in an undivided beaker-type cell under constant current conditions at room temperature.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Main Product Yield (Acetophenone, 3) | 34 | % | Isolated yield, optimum conditions (Table 1, Entry 4) |
| Anode Material | Boron-Doped Diamond (BDD) | N/A | Required for high potential oxidation |
| Cathode Material (Optimum) | Boron-Doped Diamond (BDD) | N/A | Used in undivided cell setup |
| Optimum Current Density (j) | 2.1 | mA/cm2 | Constant current applied |
| Total Charge (Q) Applied | 5 | F | Relative to 1 mole of cumene |
| Cumene Oxidation Potential | 2.40 | V | vs Ag/Ag+, measured via Cyclic Voltammetry on BDD |
| Supporting Electrolyte (Optimum) | Et4NClO4 | 0.1 M | Concentration in MeCN solvent |
| Electrode Immersed Area | 1.8 | cm2 | Used for current density calculation |
| Reaction Temperature | Room Temperature (rt) | N/A | No heating required |
| Byproduct Yield (α-Cumyl Alcohol, 4) | 11 | % | Isolated yield under optimum conditions |
Key Methodologies
Section titled âKey MethodologiesâThe electro-conversion was performed using a straightforward, undivided cell setup under galvanostatic control (constant current).
- Cell Configuration: Undivided beaker-type cell equipped with BDD electrodes (0.3 x 1.0 x 7.0 cm; 1.8 cm2 immersed area).
- Reaction Mixture: 1.00 mmol cumene (1) dissolved in 5 mL MeCN solvent.
- Electrolyte: 0.1 M Et4NClO4 (tetraethylammonium perchlorate) was used as the supporting electrolyte.
- Electrolysis Conditions: The reaction was run at room temperature (rt) under constant current conditions.
- Current Application: A current density of 2.1 mA/cm2 was applied until a total charge of 5 F (Faradays, relative to the mole of cumene) was passed.
- Intermediate Confirmation: Control experiments using MeCN-MeOH solvent confirmed the reaction intermediate was the cumyl cation (a cationic species), evidenced by the formation of methyl cumyl ether (5) in 21% yield.
- Oxygen Source Determination: Experiments using dehydrated MeCN and MeCN-H2O mixtures confirmed that the oxygen source for the hydroperoxide intermediate is dissolved oxygen, not residual water.
- Product Isolation: After electrolysis, the solvent was removed in vacuo, and the residue was purified using silica gel column chromatography (CH2Cl2).
Commercial Applications
Section titled âCommercial ApplicationsâThis technology, centered on the use of BDD electrodes for high-potential organic synthesis, has relevance across several industrial sectors:
- Fine Chemical Manufacturing: Direct, clean synthesis of oxidized aromatic alkyls (e.g., acetophenone from cumene), reducing reliance on traditional, high-energy catalytic processes.
- Sustainable Chemical Production: Provides a scalable, cost-efficient, and environmentally benign alternative for industrial oxidation reactions, aligning with growing demands for green chemistry protocols.
- Electrochemical Reactor Design: The successful use of BDD in an undivided cell demonstrates potential for simplified reactor designs in industrial electrosynthesis, avoiding complex membrane separation.
- Advanced Oxidation Processes (AOPs): BDDâs wide potential window is critical for generating highly reactive species (like hydroxyl radicals or superoxide) necessary for both organic synthesis and environmental remediation (e.g., industrial wastewater treatment).
- Energy Storage and Conversion: The ability of BDD to efficiently handle oxygen reduction (generating superoxide/hydroperoxide) is relevant to optimizing oxygen electrochemistry in fuel cells and metal-air batteries.
View Original Abstract
A straightforward electro-conversion of cumene into acetophenone has been reported using boron-doped diamond (BDD) electrodes. This particular conversion is driven by the addition reaction of a cathodically generated hydroperoxide anion to an anodically generated cumyl cation, where the BDDâs wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe.