5-(4-Chloro-phenyl)-3-(4-nitro-benzyl)-3,6-dihydro-[1,3,4]oxadiazin-2-one → 3-(4-Amino-benzyl)-5-(4-chloro-phenyl)-3,6-dihydro-[1,3,4]oxadiazin-2-one

A suspension of the compound obtained in Step D (42.02 mmoles) in a mixture of EtOH (350 ml) and acetic acid (26 ml) is heated at reflux for 5 minutes. Powdered iron (309 mmoles) and FeCl3.6H2O (2.1 mmoles) are added to the resulting solution. The reaction mixture is stirred at reflux overnight. After evaporation, water (250 ml) is added to the residue and then sonicated for 2 minutes. The mixture is made alkaline (pH 12) using aqueous 2M sodium hydroxide solution, then diluted with AcOEt (500 ml) and then filtered over Celite. The phases are separated and the aqueous phase is extracted with AcOEt. The organic phases are combined. The organic phase obtained is washed with water and then with saturated NaCl solution, dried over sodium sulphate, filtered and evaporated to dryness. The residue is triturated in ethyl ether, filtered and dried in vacuo to yield the title product in the form of a white powder, which is used directly in the next Step.