CAAC–CAAC dimers with alkylene spacers are presented. These compounds are electron-rich and undergo one- and two-electron oxidation.

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu I -complexes and cyclic thiones when reacted with Cu I -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu I -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH 2 ) by 1,1-dehydration of methanol. Addressed is also the reactivity of water towards CAACs, which proceeds through an oxidative addition of the OÀ H bond to the carbon(II)-center. This emphasizes the ability of carbon-compounds to mimic the reactivity of transition-metal complexes: reversible oxidative addition and reductive elimination of the OÀ H bond to/from the C(II)/C(IV)-centre.

Herein, a new type of carbodicarbene (CDC) comprising two different classes of carbenes is reported; NHC and CAAC as donor substituents and compare the molecular structure and coordination to Au(I)Cl to those of NHC‐only and CAAC‐only analogues. The conjugate acids of these three CDCs exhibit notable redox properties. Their reactions with [NO][SbF6] were investigated. The reduction of the conjugate acid of CAAC‐only based CDC with KC8 results in the formation of hydrogen abstracted/eliminated products, which proceed through a neutral radical intermediate, detected by EPR spectroscopy. In contrast, the reduction of conjugate acids of NHC‐only and NHC/CAAC based CDCs led to intermolecular reductive (reversible) carbon–carbon sigma bond formation. The resulting relatively elongated carbon–carbon sigma bonds were found to be readily oxidized. They were, thus, demonstrated to be potent reducing agents, underlining their potential utility as organic electron donors and n‐dopants in organic semiconductor molecules.

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.

Alkenes are known to undergo oxidation to radical cations and dications. The radical cations are often highly reactive and not stable under air. Herein, we report the synthesis, isolation, characterization, and molecular structure of an alkene-derived radical cation A, which is stable in air both in the solid state and in solution. The access to this compound was facilitated from E-diamino tri-substituted alkene B as a synthon for the synthesis of A through one-electron oxidation. The E-diamino tri-substituted alkene B was synthesized by the two-electron reduction of N,N′-1,2-propylene-bridged bis-2-phenyl-pyrrolinium cation C. Under two-electron oxidation, alkene B transforms back to cation C involving a double carbocation rearrangement.

The isolation of carbon-centered diradicals is always challenging due to synthetic difficulties and their limited stability. Herein we report the synthesis of a trans-1,4-cyclohexylene bridged bis-NHC-CAAC dimer derived thermally stable...

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu I -complexes and cyclic thiones when reacted with Cu I -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu I -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH 2 ) by 1,1-dehydration of methanol. Addressed is also the reactivity of water towards CAACs, which proceeds through an oxidative addition of the OÀ H bond to the carbon(II)-center. This emphasizes the ability of carbon-compounds to mimic the reactivity of transition-metal complexes: reversible oxidative addition and reductive elimination of the OÀ H bond to/from the C(II)/C(IV)-centre.

Carbenes. In their Research Article (e202202637), Tharangattu N. Narayanan, Carola Schulzke, Cem B. Yildiz, Anukul Jana et al. report the in situ generation of cyclic (alkyl)(amino)carbenes through the thermal 1,1‐dehydration of secondary pyrrolidin‐2‐ol alcohols.