Microdroplets Co-catalyze Nitro Hydrogenation in Organic and Pharmaceutical Application.

Aqueous microdroplets spontaneously generate interfacial species, opening new avenues for catalyst-free chemistry. However, research has focused on acidic and oxidative pathways, leaving basic and reductive transformations largely unexplored. In this study, we demonstrated that interfacial superbases catalyzed nitro reduction without external base catalysts, achieving up to 33% yield, compared to no conversion in the bulk phase. With the addition of 0.5 mol % 4,4'-bipyridyl (4 times decreased compared to the literature) for co-catalysis, nitro hydrogenation was completed in ethanol microdroplets due to a remarkable rate acceleration factor of 1.05 × 104. This method afforded (hetero)aromatic and aliphatic amines and known pharmaceuticals in satisfactory yields (81-98%) and gram scalability (up to 1.63 g h-1) with excellent functional group tolerance, highlighting its potential for organic and pharmaceutical applications.