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 H₂O/CO₂ 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 CO₂, 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 CO₂ at 60°C in 8 h. The Fe/H₂O/CO₂ 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 CO₂. 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.