Chemoselective Reductive Heterocyclization by Controlling the Binomial Architecture of Metal Particles and Acid-Base Properties of the Support

Abstract

[EN] 2,¿1-¿Benzisoxazoles were produced by reductive heterocyclization of 2-¿nitroacylarenes using supported Pt nanoparticles. The reaction involves a cascade process in which the first step is the redn. of the nitro group into hydroxylamine which subsequently cycles to 2,¿1-¿benzisoxazole through the nucleophilic attack to the carbonyl group in 2-¿position. The reaction was performed on Pt¿/C, Pt¿/TiO2 and Pt¿/MgO using hydrogen as reducing agent under mild reaction conditions. Pt¿/MgO was the most active and selective catalyst. The study of the influence of the crystal size of the metal on the activity and selectivity, combined with the reaction mechanism by in situ FTIR spectroscopy of the adsorbed reactant, showed that max. activity and selectivity to the target compd. can be achieved by controlling the architecture of metal particles and acid-¿base properties of the support. The effect of the temp. on the selectivity, the stability of Pt¿/MgO catalyst, and the scope of the reaction were studied. Finally, the reductive cyclization using different metals (Pd and Au) supported on MgO was also performed.