Copper(II) bromide as a procatalyst for the in situ preparation of active Cu nanoparticles for the efficient reduction of nitroarenes using sodium borohydride is described. During reduction, Cl, I, COOH, aliphatic nitro and OCH₂Ph groups remain intact displaying the chemoselectivity of the process. The method is also useful for the reduction of cyano and olefinic compounds. Scalability of the method was demonstrated up to 100 mmol.