Fe3O4 nanoparticles as an efficient catalyst for one-pot synthesis of novel fused phosphorus heterocycles bearing diethyl phosphonate

An efficient and practical method for the synthesis of novel fused phosphorus heterocycles incorporating diethyl phosphonate by the one-pot in the presence of Fe3O4 nanoparticles as a reusable catalyst was achieved. The four-component reactions of ortho-substituted anilines, namely 2-aminophenol, 2-aminothiophenol and 1,2-phenylenediamine with salicylaldehyde, diethyl phosphite and hexaethylphosphorus triamide in the presence of Fe3O4 nanoparticles as a catalyst at 80–90 °C afforded the corresponding 1,3,2-benzo(oxaza/thiaza/diaza)phospholo[2,3-b][1,3,2]benzoxazaphosphinines 1–3 in good yields (80-84%). When the same reactions were repeated by substitution of salicylaldehyde with benzaldehyde, the 1,2-benzazaphospholo[2,1-b][1,3,2]benzo(oxaza/thiaza)phospholes 4 and 5 and 1,3,2-benzodiazaphosphole 6 derivatives were isolated in 78–83% yields. The structures of the synthesized compounds were established by elemental analysis and spectroscopic techniques (IR, MS and NMR).