Photoinduced Decarbonylative Rearrangement of Diazabicyclo[2.2.2]Octenones: A Photochemical Approach of Diazabicyclo[4.1.0]heptene Skeleton from Masked <i>o</i>‑Benzoquinone

We report a photoinduced decarbonylative rearrangement of diazabicyclo[2.2.2]­octenone in the facile synthesis of a functionalized diazabicyclo[4.1.0]­heptene skeleton, a unique derivative of the hydropyridazine type structure which could be found in a variety of biologically active natural products. The scope of functional group compatibility in the photoreaction was examined by taking advantage of the easy access of the heterobicyclo[2.2.2] structure from the Diels–Alder reaction of masked o-benzoquinones. 4-Phenyl-1,2,4-triazoline-3,5-dione served as the dienophile which provided the adjacent N–N unit in hexahydropyridazine-type products of subsequent photorearrangement