Cobalt ferrite nanoparticles for annulation of C3-substituted nitroarenes and aryl isothiocyanates.

The synthesis of medicinally relevant N-aryl-substituted 2-aminobenzothiazoles often uses 2-aminothiophenol derivatives, which are not commercially abundant, as starting materials. Herein, we report a method for the annulation of C3-substituted nitroarenes and aryl isothiocyanates towards the synthesis of 2-aminobenzothiazoles. Reactions proceeded in the presence of cobalt ferrite nanoparticles as a catalyst, DABCO as a base, and DMF as a promoter. The cobalt ferrite nanoparticles could be recovered after each run and reused up to 3 times while the product yield was not diminished. Our method appears to be the first example of the direct use of substituted nitroarenes for yielding 2-aminobenzothiazoles.

Synthesis of 2-benzyl benzoxazoles and benzothiazoles via elemental sulfur promoted cyclization of styrenes with 2-nitrophenols and N,N-dialkyl-3-nitroanilines.

Herein we report a method for affording 2-benzyl benzoxazoles from substituted styrenes and 2-nitrophenols. The success of this method relies on the use of simple reagents, namely elemental sulfur and DABCO. A combination of identical reagents was utilized for the annulation of styrenes with N,N-dialkyl-3-nitroanilines to afford 2-benzyl benzothiazoles. Overall, benzoxazoles and benzothiazoles bearing useful functionalities such as halogens, amines, and heterocyclic groups were isolated in moderate to good yields. Our methods are a rare example of divergent transformations of substituted nitroarenes towards 2-benzyl benzoxazoles and benzothiazoles.