EVIDENCE FOR STEPWISE NITROGEN EXTRUSION AND RING EXPANSION UPON PHOTOLYSIS OF PHENYL AZIDE

The temperature dependence of the products formed on photolysis of two independent precursors of phenylnitrene has been studied. The identity of the product-forming intermediates (triplet phenylnitrene versus ketene imine) produced on photolysis of phenyl azide and benzenesulfoximine in the presence of diethylamine show the same qualitative variation with temperature. An excited state of the nitrene precursor is not responsible for the known temperature dependence of the distribution of stable products. The data are consistent with stepwise formation of singlet phenylnitrene and subsequent expansion to azacycloheptatetraene. The singlet and triplet energies of phenyl azide have been determined by energy transfer.