Iodine-Catalyzed Radical C–H Amination of Nonaromatic Imidazole Oxides: Access to Cyclic α-Aminonitrones
Alexey A. Akulov, Михаил В. Вараксин, Anna A. Nelyubina, Anton N. Tsmokaluk, Dmitrii G. Mazhukin, А. Ya. Tikhonov, Valery N. Charushin, Олег Н. Чупахин
Abstract
A straightforward cross-dehydrogenative coupling approach to incorporate alicyclic amino residues into the structure of model cyclic aldonitrones, 2 H -imidazole oxides, is reported. The elaborated C(sp 2 )–H functionalization is achieved by employing cyclic amines in the presence of the I 2 – tert -butyl hydroperoxide (TBHP) reagent system. As a result, a series of 19 novel heterocyclic derivatives were obtained in yields of up to 97%. A mechanistic study involving electron paramagnetic resonance spectroscopic experiments allowed the radical nature of the reaction to be confirmed. In particular, the envisioned mechanistic rationale comprises N-iodination of a cyclic amine, followed by N–I bond homolysis of the resulting intermediate and subsequent amination of the nitrone moiety via the newly generated nitrogen-centered radical.