Abstract: On EI-MS, the saturated oxygen atom of the ethoxylcarbonyl group is capable of acting as site to which a hydrogen atom can be transferred, the presence of hydrogen on an azirino gives a product ion corresponding to the loss of alcohol. Seven memberd ring of diazepine decomposes by α-cleavage follow by 2-ehlorophezyl or 2-chlorophenylethylene elimination gives benzamidazole or quinoxaline.