Selective Catalytic Hydrogenation of Functionalized Nitroarenes: An Update

In this update, progress made in the last decade for the selective catalytic hydrogenation of nitroarenes in the presence of other reducible functions is reviewed. The main focus is on catalytic systems capable of reducing nitro groups with very high chemoselectivity in substrates containing carbon-carbon or carbon-nitrogen double or triple bonds, carbonyl or benzyl groups, and multiple Cl, Br, or I substituents. The performance of new catalyst types is described, most notably of gold-based catalysts, but also of modified classical Pt, Pd, and Ni catalysts, as well as homogeneous catalysts. The best results for the various chemoselectivity problems are compiled and assessed with regard to their versatility and synthetic viability. In addition, progress in understanding mechanistic aspects are briefly described.