Used as a catalyst in organic synthesis, particularly in coupling reactions such as Ullmann-type reactions where carbon-carbon or carbon-heteroatom bonds are formed. It is effective in reactions involving aryl halides and nucleophiles like amines, alcohols, or thiols. Also employed in the synthesis of pharmaceuticals, agrochemicals, and fine chemicals due to its ability to facilitate transformations under relatively mild conditions. Additionally, cuprous bromide finds use in photochemical reactions and in some cases as a reagent in the preparation of other copper-based catalysts.