Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen - a suitable way to N-hydrazonation of C-H-bonds.

The sensitized photoexcitation of 2-diazocyclopentane-1,3-diones in the presence of THF leads to the insertion of the terminal N-atom of the diazo group into the α-С-Н bond of THF, producing the associated -alkylhydrazones in yields of up to 63-71%. Further irradiation of hydrazones derived from furan-fused tricyclic diazocyclopentanediones culminates in the cycloelimination of furans to yield 2--(alkyl)hydrazone of cyclopentene-1,2,3-trione. By contrast, the direct photolysis of carbocyclic diazodiketones gives only Wolff rearrangement products with up to 90-97% yield.