Variable temperature proton nmr spectra indicate an activation energy of 19.0±0.5 kcal/mol for conformational equilibration in hexahydro-3, 3, 7, 7-tetramethyl-1, 2-oxazepine-5-one. It is suggested that the rate process involves slow conformational interconversion of the seven- membered ring and not slow inversion at the nitrogen atom. The synthesis of several related 1, 2-oxazepines is described.
![7,7,10,10-tetramethyl-1,4,9-trioxa-8-azaspiro[4.6]undecane Structure](https://image.chemsrc.com/caspic/327/55815-52-6.png)