Selective Reduction of Nitro Group Without Effecting Vinyl or Alkyne Group and Hydration of Alkyne in Pressurized
1State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China.
Abstract:
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.
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