Intramolecular H-Atom Abstraction in γ-Azido-Butyrophenones: Formation of 1,5 Ketyl Iminyl Radicals

Photolysis of gamma-azidobutyrophenone derivatives yields 1,4 ketyl biradicals via intramolecular H-atom abstraction. The 1,4 ketyl biradicals expel a nitrogen molecule to form 1,5 ketyl iminyl biradicals, which decay by ring closure to form a new carbon-nitrogen bond. The 1,5 ketyl iminyl biradicals were characterized with transient spectroscopy. In argon/nitrogen-saturated solutions, the biradicals have lambda(max) approximately 300 nm and tau = 15 micros. DFT-TD calculations were used to support the proposed mechanism for formation of the 1,5 ketyl iminyl radicals.