Intramolecular Cycloadditions of Photogenerated Azaxylylenes with Oxadiazoles Provide Direct Access to Versatile Polyheterocyclic Ketopiperazines Containing a Spiro-oxirane Moiety

Photogenerated azaxylylenes undergo intramolecular cycloadditions to 1,3,4-oxadiazole pendants, which are accompanied by concomitant release of dinitrogen, yielding functionalized ketopiperazinoquinolinols containing an oxirane moiety fused to the quinolinole moiety while spiro-connected to diketopiperazine. These primary photoproducts are reactive versatile intermediates which can be further derivatized under nucleophilic S(N)1- or S(N)2-like ring opening of the oxirane moiety. The oxidized quinolinones undergo new rearrangements under the conditions of the Schmidt reaction, leading to unprecedented triazacanoindolinones.