Ligand-free access to benzisothiazolones and benzisoselenazolones through NiFe2O4 catalyzed concomitant annulation of 2-halobenzanilides with chalcogens and their late-stage transformations

Abstract

The present work demonstrates an efficient ligand-free synthesis of diverse benzisothiazolones and benzisoselenazolones exploiting a magnetically retrievable nano-nickel ferrite catalyst in X–N (X = S, Se) cross-coupling with concurrent annulation of 2-iodobenzanilides and elemental sulphur or selenium. The protocol features the use of the recyclable nano-nickel ferrite catalyst, substrate diversity, cheap sulphur and selenium powder as chalcogenation agents, comparatively low reaction temperature and useful application of synthesized molecules. The rarely explored chemistry of NiFe₂O₄ towards the X–N cross-coupling reaction well complements conventional methods for the synthesis of S–N or Se–N heterocycles. Nickel ferrite nanoparticles were prepared by a simple hydrothermal method and characterized by using XRD, SEM, TEM, HRTEM, SAED, energy dispersive X-ray spectroscopy, XPS, ICP-AES and FT-IR analyses. The easy recovery of the catalyst and high product conversion make the protocol practically economic. The oxidation prone sulphur in benzisothiazolones is transformed into a variety of saccharin motifs using TBN and oxygen as the right oxidant combination. In addition, both the S–N and Se–N containing heterocycles are scaled up and further transformed into novel C–H functionalized products and selenol derivatives, respectively.