Ring contraction acid imides

The thermal and acid-catalysed ring-contractions of l-acyl-l,2-diazepines to pyridine iV-imides and/or 2-(acylamino)pyridines is well known. Moore has now reported a new reaction path in the thermolysis of (84), leading to the 1,3-diazepine (85) in addition to a 6-benzamidopyridine. A stepwise conversion of (84) into (85) is favoured, assisted by electron release from oxygen, rather than a sigmatropic rearrangement " [cf. the formation of (65) described above]. 

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