Lactams phenanthridones

The action of ethylamine on the dienone lactone (182) gives j 7-ethyl-3-ethylaminophenanthridone (183) instead of the expected IV-ethyl lactam. The yield of the phenanthridone rises with increasing temperature and at 210° it is the sole product. The following mechanism has been suggested ... 

Phenanthridine in methanol solution is unaffected by ozone, but in methylene dichloride quinoline-3,4-dicarboxylic acid (2%) and phenanthridone (23%) are formed a large part of the remaining phenanthridine can be recovered unchanged.335 The reaction thus proceeds much less readily than in the case of acridine. The mechanism by which the lactam is formed is not known with certainty, but an intermediate such as 233 has been proposed.335 However, an initial electrophilic attack producing 234, followed by loss of oxygen and a proton shift, seems equally likely. 

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