Rearrangement of Electron‐Rich N‐Allyldibenzotetraazafulvalenes –An Experimental and Theoretical Study

Abstract

The deprotonation of N‐allylbenzimidazolium halides 9a–d initially results in the formation of the N‐allyldibenzotetraazafulvalenes 10. These electron‐rich olefins rearrange to give 1,1′,2′,3′‐tetraalkyl‐1′,2′‐dihydro‐2,2′‐bibenzimidazoles 13, either by a 3‐aza‐Cope rearrangement or by a homolytic N‐alkyl bond cleavage and addition of the radical at the 2′‐position of the bibenzimidazole. Alternatively, double N‐alkyl bond cleavage gives rise to 1,1′‐dialkyl‐2,2′‐bibenzimidazoles 14. All reaction pathways were studied by use of quantum chemical calculations at the DFT/B3‐LYP/TZVP//DFT/BP86/SV(P) level, by comparison of the activation parameters for the radical and the concerted rearrangement mechanisms with the experimentally obtained products.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Molecular Structures and Catalytic Activity of Palladium Complexes Derived from Lutidine-bridged Bis(benzimidazolin-2-ylidene) Ligands

“…Complexes [5]Br- [8]Br have been completely charac- terized by NMR spectroscopy and mass spectrometry. Isolation of the free carbene ligands or their dibenzotetraazafulvalene dimers was not possible because of intramolecular rearrangement processes occurring upon C2 deprotonation as described earlier [10].…”

Structural Diversity of Copper(I)–N‐Heterocyclic Carbene Complexes; Ligand Tuning Facilitates Isolation of the First Structurally Characterised Copper(I)–NHC Containing a Copper(I)–Alkene Interaction

“…[25,26] Reaction of compound 1b with a base (tBuOK) in the presence of CuBr resulted in the desired product, in addition to two allyl rearrangement products (see ESI). [27] As the allyl substituents appear to be sensitive to strong bases, the coordination of ligands 1a-1e to copper(I) was therefore achieved via deprotonation and coordination in situ using copper oxide (Scheme 1).…”

New structural motifs of silver and gold complexes of pyridine-functionalized benzimidazolylidene ligands

“…Benzimidazolin-2-ylidenes as a class of NHC ligands are easily accessible from commercially available benzimidazole or o-phenylenediamine [40,41]. The preparation, structures, and reactions of benzannulated NHCs have been well studied by Hahn's group [42][43][44][45][46][47][48][49][50][51][52], however, compared to their imidazolylidene analogues, benzimidazolin-2-ylidenes complexes are less studied both in structural diversity and homogeneous catalysis [53][54][55][56][57]. Free benzimidazolin-2-ylidene usually forms dimeric complexes, thus the preparation of metal-benzimidazolin-2-ylidene complexes through Ag-benzimidazolin-2-ylidene transmetallation approach is convenient and practical.…”