2-[(3'-chloro-4'-nitro phenylamino) methyl]phenol 1 underwent facile condensation with various phosphorus dichlorides 2a-j in the presence of TEA in dry THF at 60-65 and afforded corresponding 1,3,2 λ5 –benzoxaphosphinin-2-one derivatives 3a-j. Their chemical structures were characterized using IR, 1H, 13C, 31P NMR and mass spectral studies. All the above compounds were screened for anti-microbial activity and their bioassay showed them to possess significant antimicrobial activity