Laser flash photolysis of 3-(biphenyl-4-yl)-2H-azirine. Dynamic protonation of a nitrile ylide

Abstract

Laser flash photolysis of 3-(biphenyl-4-yl)-2H-azirine has been carried out in various alcohols. In each case the formation of a new band was detected, resulting from the decay of nitrile ylide (NY). The formation rate which agreed completely with the decay rate, decreased with increasing pK_s of the alcohol. The new band was assigned to an azaallyl cation, formed by protonation of the terminal carbon atom of NY. The new band also decayed according to pseudo-first-order kinetics and its rate decreased with increasing pK_s.