Photocatalysis of Organic Reactions Using Crude St. John's Wort

Abstract

Natural products, like hypericin, have attracted interest as cost-effective, safer photocatalysts in organic synthesis. They effectively absorb light and offer an alternative to metal-based catalysts like ruthenium and iridium. Hypericin and its derivatives are naturally found in the supplement St. John's Wort, but isolating pure hypericin is difficult due to the low concentration. Although bioengineering microorganisms to produce hypericin is possible, it is technically complex. Instead, we explored using St. John's Wort supplement capsules directly as the photocatalyst in arylation reactions with diazonium salts and aromatic rings. Reaction conditions were optimized by purifying the capsules, using an everyday sun lightbulb, and irradiating for 48 hours. To evaluate the efficacy of this approach, the recyclability of the St. John's Wort will be tested using eco-friendly deep eutectic solvents and room temperature ionic liquids. The results of this research should highlight the potential for natural product mixtures to serve as effective and simple photocatalysts for organic reactions.