Thermolysis of a Tertiary Alkoxyamine. Recombination and Disproportionation of α-Phenethyl/Diethyl Nitroxyl Radical Pairs

Abstract

Alkoxyamine 3 undergoes thermolysis only on heating to over 150 °C, ΔH⧧ = 34.3 ± 1.6 kcal/mol and ΔS⧧ = 0.8 ± 3.7 eu. The initially formed nitroxyl (6) and α-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 5, generated from azo-α-phenylethane (1), on 2 versus styrene allowed us to calculate a rate constant at 120 °C of 5 × 103 M-1 s-1 for H• transfer from diethylhydroxylamine to 5.