Ligand-Enabled C-H Hydroxylation with Aqueous H2O2 at Room Temperature
Zhen Li1, Han Seul Park1, Jennifer X Qiao2
1The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, United States.
Researchers developed a novel catalyst for room-temperature C-H hydroxylation using green hydrogen peroxide. This scalable method efficiently converts benzoic and phenylacetic acids, enabling synthesis of complex molecules like ibuprofen and natural products.
Area of Science:
- Catalysis
- Organic Chemistry
- Green Chemistry
Background:
- Palladium(II)-catalyzed C-H activation reactions are prevalent, yet developing catalysts compatible with green oxidants like aqueous hydrogen peroxide remains a significant challenge.
- The compatibility of palladium(II) catalysts with sustainable oxidants, particularly aqueous hydrogen peroxide, has been a persistent hurdle in various catalytic oxidations, including Wacker-type reactions.
Purpose of the Study:
- To develop a novel catalytic system for efficient C-H hydroxylation using a green oxidant.
- To enable room-temperature palladium-catalyzed C-H hydroxylation of benzoic and phenylacetic acids using aqueous hydrogen peroxide.
- To demonstrate the scalability and utility of the developed methodology for synthesizing valuable compounds.
Main Methods:
- Development of a bifunctional bidentate carboxyl-pyridone (CarboxPyridone) ligand.
- Utilized aqueous hydrogen peroxide (35% H2O2) as the industry-compatible oxidant.
- Conducted palladium-catalyzed C-H hydroxylation reactions at room temperature.
Main Results:
- The CarboxPyridone ligand enabled room-temperature C-H hydroxylation of a wide array of benzoic and phenylacetic acids.
- Demonstrated scalability with a 1000 mmol scale synthesis of ibuprofen (206 g) using only 1 mol % palladium catalyst loading.
- Showcased the protocol's utility through derivatization of products and synthesis of polyfluorinated natural products (coumestan, pterocarpene) from phenol intermediates.
Conclusions:
- A novel CarboxPyridone ligand facilitates efficient and scalable palladium-catalyzed C-H hydroxylation using aqueous hydrogen peroxide at room temperature.
- This methodology offers a practical and green approach for synthesizing valuable organic molecules, including pharmaceuticals and natural products.
- The developed catalytic system overcomes previous limitations in using sustainable oxidants with palladium catalysts.
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