Unusually Long Lifetimes of the Singlet Derived from 4-Azido-2,3,5,6-tetrafluorobenzamides

Article abstract of DOI:10.1021/j100053a012

Laser flash photolysis (308 nm, 20 ns, 150 mJ) of 4-azido-2,3,5,6-tetrafluorobenzamides, esters, and thioesters generate singlet nitrenes which can be intercepted with pyridine to produce strongly absorbing ylides.It was possible to resolve the rate of formation of the ylides as a function of pyridine concentration.This has lad to direct measurements of the absolute rate constants of (a) the reaction of the nitrene with pyridine, (b) ring expansion of the nitrene to a ketenimine, and (c) singlet to triplet nitrene intersystem crossing.