Towards In‐Plane Delocalized 4N/7e Radical Cations and 4N/6e Dications – One‐/Two‐Electron Oxidation of Proximate‐Parallel Bis(N,N'‐bicyclic)‐bishydrazines

Abstract

In the pursuit of novel bishomoconjugated (σ‐bishomoaromatic) 4N/7(6)e bonding motifs, (bisseco)pagodane/isopagodane and dodecahedrane‐like, caged, proximate‐parallel bishydrazines have been designed as suitable host skeletons. The derived radical cations and dications are characterized by calculations as cyclically in‐plane delocalized (σ‐bishomoaromatic) species (4N/7(6)e). However, the synthetic approaches based on a pool of half‐caged proximate‐parallel bisdiazenes/bishydrazines and on strategies in part elaborated in the pagodane area have not led to the target structures. Half‐caged, rather flexible bis(N,N'‐bicyclic) bishydrazines (9,10) evolved as the structurally closest synthetically accessible model compounds. Whilst CV (PE, ESR)measurements were not suggestive of significant through‐space interaction in the respective radical cations and dications, DFT calculations (B3LYP/6‐31G*) identified a singlet dication (102+) as proximate, cyclically in‐plane delocalized species, which, however, relaxed into a more stable, more distant triplet. In an Appendix, selected examples are presented for the synthetic utilization of proximate‐parallel bisdiazenes (bishydrazines) in the area of more or less preorganized, semi‐ to fully caged tetra(hexa)azapolycyclic molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Reactions of the Tetraalkyldigallium Compound R2Ga–GaR2 [R = CH(SiMe3)2] with Acidic Reagents, Retention vs. Cleavage of the Ga–Ga Bond and Formation of Supramolecular Aggregates via Hydrogen Bonding

“…Two five‐membered GaCN 2 O heterocycles result which are annulated via the central N–N bond. The N–N bond lengths (143.1 pm on average) are in the lower range of N–N bonds in hydrazine derivatives,12 but correspond well to values of dicarbonyl hydrazides 20. Ga–O (194.6 pm) and Ga–N distances (201.6 pm on average) are in normal ranges.…”

Directed, Palladium(II)-Catalyzed Intermolecular Aminohydroxylation of Alkenes Using a Mild Oxidation System

“…14 Moreover, after phthalimide deprotection the resulting primary amine was found to undergo cyclization to cleave the directing group and form β-hydroxy-γ-lactam derivative 6 . 10d,10e We discovered, perhaps unsurprisingly, that this β-hydroxy AQ amide motif is quite susceptible to elimination upon activation; for instance, heating the mesyl-protected alcohol in triethylamine gave 96% of protected trans-4-aminocrotonic acid 7 , 15 which is a potent agonist of GABA(A) and GABA(C) receptors. 16…”

[6+6]Photocycloadditions in Face‐to‐Face Benzo/Pyridazino Substrates – En Route to Azapagodanes

“…3.2 Å), could have meant a highly attractive extension of our search for proximate, synperiplanar bishydrazines and the derived (radical) ions. [33] In explorative experiments, however, the C=N double bonds in 15a proved resistant to their hydrogenative saturation and bridging interconnections. [34] With this 86th report on "Photochemical Transformations", a series comes to an end which began in 1962, [35] in the earlier days of preparative, particularly mechanistic organic photochemistry.…”