Solvent-free zinc-mediated Béchamp reduction using mechanochemistry†

Abstract

In this study, we report the first mechanochemical protocol for highly efficient solvent-free Béchamp reduction using inexpensive Zn metal as a reductant in combination with NH₄Cl. This reaction is considerably faster than previous solution-based reactions. Herein, a variety of nitroarenes were chemoselectively reduced to the corresponding primary aromatic amines in good yields within 30 min. Notably, the present solvent-free protocol does not require an organic solvent or air-sensitive and/or expensive reagents, and all synthetic operations can be performed under ambient conditions, greatly enhancing its practical utility. Furthermore, the feasibility of the gram-scale reaction as well as the synthesis of an important intermediate of the muscle relaxant tizanidine were demonstrated.