A Bottleable Imidazole-Based Radical as a Single Electron Transfer Reagent

Abstract

Reduction of 1,3-bis(2,6-diisopropylphenyl)-2,4-diphenyl-1H-imidazol-3-ium chloride (1) resulted in the formation of the first structurally characterized imidazole-based radical 2. 2 was established as a single electron transfer reagent by treating it with an acceptor molecule tetracyanoethylene. Moreover, radical 2 was utilized as an organic electron donor in a number of organic transformations such as in activation of an aryl−halide bond, alkene hydrosilylation, and in catalytic reduction of CO 2 to methoxyborane, all under ambient temperature and pressure.Note pubs.acs.org/joc

Mesoionic N-heterocyclic olefin catalysed reductive functionalization of CO2 for consecutive N-methylation of amines

“…Simultaneously, the amine is activated by reaction with 9-BBN forming the N -borylated compound 12 with the liberation of hydrogen gas. In the subsequent step, the formyl group was transferred from the intermediate 11 to N -borylated amine 12 leading to the formation of formanilide 13 and (9-BBN) 2 O as a byproduct, which was characterized by NMR spectroscopy 46 (see the ESI; Fig. S24 and S25 ‡ ).…”

Air-/Heat-Stable Crystalline Carbon-Centered Radicals Derived from an Annelated N-Heterocyclic Carbene

“…The first structure of imidazole-based radical III was characterized in which the C2 and C4 positions were sterically protected by phenyl groups (Figure 1a, right). 9 Radical III was moderately stable under an inert atmosphere but decayed within minutes when exposure to air, indicating that only steric protection may not be sufficient to render the NHC-based radicals stable. On the basis of the above findings, we speculated that fusing an additional ring on the imidazole backbone could improve the stability of NHC-stabilized organic radicals by enhancing the delocalization of spin density.…”

The histidine-brace active site of a copper monooxygenase is redox active and forms part of an in-built enzyme repair mechanism

“…In making an assignment of the pre-edge transitions in Int1, we turn to previous work on the UV-vis spectra of transient imidazolyl radicals, Cu II -(imidazolyl radicals) and Cu II -(histidyl radicals), all of which exhibit semi-intense absorptions at ca. 360 nm (e > 2,000 M -1 cm -1 ) 28,29 , and also that of an isolated imidazolyl radical with an intense band at 365 nm (e ~ 2,000 M -1 cm -1 ) 30 . The analogy between these absorptions and that in Int1 directs us towards the possibility that Int1 is, in fact, a Cu II -(histidyl radical) complex.…”