A new family of phosphorus heterocycle, namely 2-substituted 3-[4-(2-oxo-3,4-dihydro-2λ 5 benzo[e][1,3,2]oxazaphosphinin-3-yl)phenyl]-3,4-dihydrobenzo[e][1,3,2]oxazaphosphinin-2oxides (5a–j) has been synthesized by the condensation of 2-[[4-(2-hydroxy-benzylamino)phenylamino]methyl]phenol (1) with phosphorus oxychloride in presence of triethylamine in dry tetrahydrofuran, followed by the reaction with various phenols 3a–j. Alternatively, some of these compounds 5a-e were prepared by the cyclocondensation of 1 with aryl phosphorodichloridates 4a–e. All title compounds were characterized by elemental and spectral analyses. Their antimicrobial activity was also evaluated.