Highly peri-, regio- and diastereoselective 1,3-dipolar cycloaddition of mesitonitrile oxide to 1,7-dimethyl-2,3-dihydro-1H-1,4-diazepines: unexpected one-step formation of a new triheterocyclic framework

We report here an efficient one-step synthesis of new [1,2,4]oxadiazolo[4,5-d][1,4]diazepines and [1,2,4]oxadiazolo[4,5-d][1,4]-diazepine-8-spiro-5′-isoxazolines by way of highly peri-, regio- and diastereoselective 1,3-dipolar cycloadditions of mesitonitrile oxide to 1,7-dimethyl-2,3-dihydro-1H-1,4-diazepines. The structures were elucidated by spectral methods and X-ray crystallographic analysis. The regiochemistry of the cycloaddition is dictated by frontier orbital interactions.