New insights into the catalytic reduction of aliphatic nitro compounds with hypophosphites under ultrasonic irradiation

Abstract

This work describes an efficient process for the reduction of nitro compounds to the corresponding amines with a catalytic amount of Pd/C (0.6 mol%), and a mixture of sodium hypophosphite and hypophosphorous acid as a reducing agent in H₂O/2-MeTHF at 60 °C. The reaction was optimized under silent conditions. The conditions for the in situ production of H₂ using the mixture NaH₂PO₂/H₃PO₂ were studied. The influence of ultrasonic activation was investigated both in terms of efficiency and kinetics. The reaction was shown to be efficient in water, at 70 °C with a quantitative conversion and a maximal yield in only 15 min thanks to the ultrasonic activation. Finally, ultrasound was proved to act as a physical agent of phase transfer.