Selective Reduction of Nitro Group Without Effecting Vinyl or Alkyne Group and Hydration of Alkyne in Pressurized H ₂ O/CO ₂ Medium

Selective reduction of nitroaromatics containing reducible groups is of great significance and has attracted the attention in chemical synthesis. Here, a low‐cost and easy to operate H 2 O/CO 2 acidic system combined with non‐precious metal iron powder was used to prepare amino aromatics without affecting double or triple bond. Under optimized conditions (1 MPa CO 2 , 60°C, 2.5 h), the selectivity of 3‐aminostyrene reached 99.4% at 99.2% conversion of 3‐nitrostyrene. For the reduction of 4‐nitrophenylacetylene (4‐NPA) to 4‐aminophenylacetylene (4‐APA), the conversion of 4‐NPA reached 99.5%, and the selectivity to 4‐APA could reach 90.5% with 0.2 MPa CO 2 at 60°C in 8 h. The Fe/H 2 O/CO 2 system is also effective for the one‐pot transformation including the reduction and hydration of 4‐NPA to 4‐aminoacetophenone with a high conversion (95.4%) and selectivity (97.7%). After the reaction is completed, the acidic system will self‐neutralize by the release of CO 2 . The non‐precious metal‐acidic system is green, low‐cost, and high selective for the reduction of nitroaromatics without affecting the easy reducible groups and the hydration of alkyne group.