Study of concerted and sequential photochemical Wolff rearrangement by femtosecond UV-vis and IR spectroscopy

The ultrafast time-resolved ultraviolet-visible (UV-vis) and infrared (IR) spectroscopies are used for studying a simple aryl diazo ketone to assess the relative importance of these processes to the light induced formation of ketenes from a diazo carbonyl precursor. The photolysis of the conformer of the precursor has led to the formation of hot ketene from [super 1]BpC[N.sub.2]COC[H.sub.3]* by Wolff Rearrangement (WR) in concert with nitrogen extrusion.