Study of the radical chemistry promoted by tributylborane

The structures of radicals generated in the oxidation process of trialkylborane were detected based on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC/Q-ToF MS) combined with the spin trapping method. Structural identification of the spin adducts produced by 5,5-dimethyl-1-pyrroline-1-oxide with radicals could be carried out unambiguously by combining the data obtained by UPLC/Q-ToF MS analyses. Then the oxidation mechanism was described. To specify the inter-relationships between the oxidation process of trialkylborane and the concomitant radical chemistry, four kinds of alkanes providing different H-abstraction reactivity to alkoxy radical were chosen as radical capturers. The final oxidation products of trialkylborane were characterized by GC-MS and B-11-NMR. The results indicted that the radical content was not only affected by the oxidation degree of trialkylborane, but also done by the activity of alkane. Especially the hydrogen atom abstraction by n-butoxy radical played an important role in the oxidation process of tributylborane, which would promote the oxidizability of tributylborane and deepen the oxidation degree of tributylborane.