N,N′‐Ethylene‐Bridged Bis‐2‐Aryl‐Pyrrolinium Cations to E‐Diaminoalkenes: Non‐Identical Stepwise Reversible Double‐Redox Coupled Bond Activation Reactions

Abstract

This work presents a stepwise reversible two‐electron transfer induced hydrogen shift leading to the conversion of a bis‐pyrrolinium cation to an E‐diaminoalkene and vice versa. Remarkably, the forward and the reverse reaction, which are both reversible, follow two completely different reaction pathways. Establishing such unprecedented property in this type of processes was possible by developing a novel synthetic route towards the starting dication. All intermediates involved in both the forward and the backward reactions were comprehensively characterized by a combination of spectroscopic, crystallographic, electrochemical, spectroelectrochemical, and theoretical methods. The presented synthetic route opens up new possibilities for the generation of multi‐pyrrolinium cation scaffold‐based organic redox systems, which constitute decidedly sought‐after molecules in contemporary chemistry.

α,α′-Diamino-p-tetrafluoroquinodimethane: Stability of One- and Two-Electron Oxidized Species and Fixation of Molecular Oxygen

“…For the synthesis of the targeted α,α′-diamino- p -tetrafluoroquinodimethane, we synthesized the corresponding two-electron oxidized bis-iminium-cation 4 as a synthon as shown in Scheme…”

Bis-[cyclic(alkyl)(amino)carbene]-derived diradicals

“…Carbon-centre-based diradicals are generally interesting topics for various research fields; 11 their syntheses and subsequent isolation, however, are always challenging due to their extreme inherent reactivity. 12 Therefore, developing new, more facile and/or more reliable approaches for the isolation of carbon-centre-based diradicals is required, yet demanding. Strategically, we can envision to derive diradicals from bis-CAACs as synthons.…”

Activation of O2 across a C(sp3)–C(sp3) bond

“…This observation is in contrast to our recently reported N , N ′-ethylene bridged bis-2-aryl-pyrrolinium cations, which undergo double C–H activation of the ethylene bridge under reductive conditions. 14…”