O‐p‐Methoxyphenyl α‐Hydroxycarboxylic Acids as Versatile Hydroxyalkylation Agents for Photocatalysis

Reliable radical precursors are crucial for photocatalytic processes. In particular, heteroatom‐stabilized radicals have attracted considerable research interest in photocatalysis. Among them, α‐amino radicals have received the most attention, while the research on α‐hydroxy radicals is much less developed. Herein, we present O‐PMP α‐hydroxycarboxylic acids as novel precursors for the formation of oxygen‐stabilized radicals. These radicals have been successfully used as building blocks in Pd‐catalyzed allylation reactions, Ni‐catalyzed arylation and alkenylation reactions, and Giese reactions. A subsequent deprotection step liberates the corresponding hydroxyalkylation products. Heteroatom‐stabilized radicals are useful building blocks for photocatalysis. Despite the intensive research on α‐amino radicals, α‐hydroxy radicals have never received comparable attention. Herein we present O‐p‐methoxyphenyl (PMP) α‐hydroxycarboxylic acids as easy to prepare, bench‐stable and synthetically highly flexible radical precursors. Next to their synthesis, we describe their application in five different photocatalytic reactions.