The free radical rearrangements of nitrogen centered radicals were studied. The addition of tributyltin radical to the azido group affords new aminyl radicals bearing tributylstannyl group. This nitrogen centered radicals underwent intramolecular hydrogen atom abstraction reaction.
It was found that 1,5-hydrogen atom transfer from carbon to nitrogen was favorable when the resulting carbon centered radicals could be stabilized by the neighboring group after migration. When the radical stabilizing group was the nitrile group, 1,5-hydrogen transfer from carbon to nitrogen competed with intramolecular addition of aminyl radicals to the nitrile group. Also 1,5-$Bu_3Sn$ group transfer from carbon to nitrogen was found. But simple aminyl radicals generated by the reaction of sulfenamides with n-$Bu_3SnH$ gave poorer yields in hydrogen atom transfer. 1,6-Hydrogen atom transfer was much inferior to 1,5-hydrogen atom transfer.
In the reactions of some compounds containing carbon-carbon double bond, tetrahydrofuranyl or cyclopentanyl compounds were obtained in good yields through radical cyclization via radical translocation. Furthermore, reaction of alkyl azides with n-$Bu_3SnH$/AIBN afforded the corresponding aldehydes and ketones along with the amines. The formation of the carbonyl compounds is unexpected and the mechanistic insight awaits further studies.
