Thermolysis of a tertiary alkoxyamine. Recombination and disproportionation of alpha-phenethyl/diethyl nitroxyl radical pairs

Alkoxyamine 3 undergoes thermolysis only on heating to over 150 degrees C, Delta H double dagger = 34.3 +/- 1.6 kcal/mol and Delta S double dagger = 0.8 +/- 3.7 eu. The initially formed nitroxyl (6) and alpha-phenethyl radicals (5) mainly disproportionate to styrene plus diethylhydroxylamine (2) but they also recombine to starting material and undergo a new reaction, disproportionation to ethylbenzene plus nitrone(12). The latter reacts with the styrene product to yield oxazolidines 8 and 9. The competition between attack of 6, generated from azo-alpha-phenylethane (1), on 2 versus styrene allowed us to calculate a rate constant at 120 degrees C of 5 x 10(3) M-1 s(-1) for H . transfer from diethylhydroxylamine to 5.