Photoredox‐Catalyzed Decarboxylative Bromination, Chlorination and Thiocyanation Using Inorganic Salts

Decarboxylative halogenations of alkyl carboxylic acids are highly valuable reactions for the synthesis of stucturally diverse alkyl halides. However, many reported protocols rely on stoichiometric strong oxidants or highly electrophilic halogenating agents. Herein, we describe visible-light photoredox-catalyzed decarboxylative halogenations of N-hydroxyphthalimide-activated carboxylic acids that avoid stiochiometric oxidants and use inexpensive inorganic halide salts as the halogenating agents. Brominations with lithium bromide proceed under simple, transition metal-free conditions using an organic photoredox catalyst and no other additives, whereas dual photoredox–copper-catalysis is required for chlorinations with lithium chloride. The mild conditions display excellent functional group tolerance, which is demonstrated through the transformation of a diverse range of structurally complex carboxylic acid-containing natural products into the corresponding alkyl bromides and chlorides. In addition, we show the generality of the dual photoredox–copper-catalyzed decarboxylative functionalizations with inorganic salts by extension to a thiocyanation with potasium thiocyanide, which was applied to the synthesis of complex alkyl thiocyanates.