A new heterocyclic system, 1, 2, 9-triaza-8-oxabicyclo-[5.3. 0]-3, 5, 9-decatriene 4, has been synthesized by regiospecific 1, 3-dipolar cycloaddition of nitrile oxides to the imine double bond of 1, 2-diazepines. Bis-adduct 5a is obtained in only trace amounts showing that the imine double bond is more reactive than the Δ4-olefinic bond.
![5-phenyl-[1,2]diazepine-1-carboxylic acid ethyl ester Structure](https://image.chemsrc.com/caspic/277/31020-24-3.png)
![1,2,4-Oxadiazolo[4,5-b][1,2]diazepine-5(9aH)-carboxylicacid, 8-phenyl-3-(2,4,6-trimethylphenyl)-, ethyl ester Structure](https://image.chemsrc.com/caspic/396/64762-40-9.png)
![Methanone,[8-methyl-3-(2,4,6-trimethylphenyl)-1,2,4-oxadiazolo[4,5-b][1,2]diazepin-5(9aH)-yl]phenyl- Structure](https://image.chemsrc.com/caspic/158/64762-46-5.png)