Thioxanthone is a highly versatile and effective organocatalyst for photochemical applications, with its low-toxicity, metal-free structure driving growing interest in sustainable photocatalysis. Building on our previous 2021 review, this update covers advances from 2021–2025 in thioxanthone-based synthetic organic photochemistry – excluding polymerization and is organized by reaction type to highlight its expanding versatility.

Abstract

Thioxanthone (TX) and its derivatives are standout, heavy-atom-free triplet photosensitizers, due to their high triplet energy, long-lived triplet states, and ability to work synergistically with metal catalysts. These features render them highly useful in photochemical processes. A previous 2021 review covered TX's photophysical properties and photochemical applications. This review constitutes an update and highlights the growing number of studies since then, demonstrating TX's versatility in synthetic organic photochemistry. The content covers the literature during the period 2021–2025 and is organized by reaction type excluding applications in polymerization reactions.