Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione: An unusual long-lived triplet as a reaction intermediate

Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione (DBD) is pr esumed to involve a short lived carbene, followed by Wolff rearrangement to a long-lived ketene. We have detected ketene ylides following photolysis o f nan in the presence of amines but not with pyridine. The triplet state of DBD lives several microseconds, an unusual observation for a diazo compoun d; however, the triplet is not a ketene precursor, which must result from e xcited singlet state fragmentation of DBD.