1.2- Diazepinium betaines

Moore et a/.462 have studied cycloadditions to the 1,2-diazepinium betaines (1), which are also vinylogous azomethine imines. Ketenes and isocyanates add in a 1,5 manner and rearrange to 1,3-cycloadducts. Dimethyl acetylenedicarboxylate gave in 30 minutes 33% of 2, the formal product of a 1,3-cycloaddition, but possibly formed via a 1,5-cycloaddition. On heating, 2 gave 6 and another product via the postulated intermediates 4 and 7. Thermolysis of the related compounds 3 463 gave 5.464... 

A-Aminopyridinium salts (14), and their derivatives substituted at the exocyclic amino group, can also be prepared by rearrangement reactions. Thus, the diazepinone 22 and diazepinium betaine 23 are converted into the A-amino salts (26) by concentrated acids.44-47 This rearrangement... 

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