Revealing the Iron-Catalyzed ?-Methyl Scission of tert-Butoxyl Radicals via the Mechanistic Studies of Carboazidation of Alkenes.

ABSTRACT: We describe here a mechanistic study of the iron-catalyzed carboazidation of alkenes involving an intriguing metal-assisted ?-methyl scission process. Although t-BuO radical has frequently been observed in experiments, the ?-methyl scission from a t-BuO radical into a methyl radical and acetone is still broadly believed to be thermodynamically spontaneous and difficult to control. An iron-catalyzed ?-methyl scission of t-BuO is investigated in this work. Compared to a free t-BuO radical, the coordination at the iron atom reduces the activation energy for the scission from 9.3 to 3.9 ~ 5.2 kcal/mol. The low activation energy makes the iron-catalyzed ?-methyl scission of t-BuO radicals almost an incomparably facile process and explains the selective formation of methyl radicals at low temperature in the presence of some iron catalysts. In addition, a radical relay process and an outer-sphere radical azidation process in the iron-catalyzed carboazidation of alkenes are suggested by density functional theory (DFT) calculations.

SUBMITTER: Chiou MF 

PROVIDER: S-EPMC7179474 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature