Methyl Substitution as a Probe for π-Spin Distribution in the Radical Anion of 1,6-Methano[10]annulene

ESR. and ENDOR. spectra are reported for the radical anion of the 2-methyl derivative (III) of 1,6-methano[10]annulene (I). Comparison of the hyperfine data for I·? and III·? with those for the radical anions of naphthalene (II) and its 1-methyl derivative (IV), respectively, confirms the suggestion that – despite the vastly different α-proton coupling constants – the π-spin distributions should be similar in the two series. This result provides further support for the view that the π-spin distribution, in particular, and the cyclic π-delocalisation, in general, are not seriously perturbed by moderate deviations of the π-perimeter from planarity.     

Specifically (π → π*)-Induced Cyclohexenone Reactions 6-Benzylbicyclo [4.4.0]dec-1-en-3-ones

6-Benzylbicyclo [4.4.0]dec-1-en-3-one ( 9 ) and the 2-methyl homologue ( 10 ) underwent a (γ → α )-1, 3-benzyl shift to the β,γ-unsaturated ketones 21 and 22 , respectively, when excited in the π π* absorption band. The quantum yield was ca. 0.1 at 254 nm for the formation of both products in alkane solvents. These reactions occur specifically from the S₂(π, π*) state in competition with its decay to the S₁(n, π*) and T states. The triplet reaction of 9 , initiated by n → π* irradiation and by sensitization, was a double-bond shift to 20 , whereas no identifiable product was observed from 10 under these conditions. Direct and acetone-sensitized irradiations of 21 and 22 resulted in oxadi-π-methane rearrangements to mixtures of syn- and anti- 30 and syn- and anti- 31 , respectively.     

Disupersilylperoxo Radical Anion [tBu3SiOOSitBu3]⋅−: An Intermediate of Supersilanide Oxidation

In the oxidative process of the supersilanide anion [SitBu₃]^?, radical species are generated. The continuous wave (cw)‐EPR spectrum of the reaction solution of Na[SitBu₃] with O₂ revealed a signal, which could be characterized as disupersilylperoxo radical anion [tBu₃SiOOSitBu₃]^?? affected by sodium ions though ion‐pair formation. A mechanism is suggested for the oxidative process of supersilanide, which in a further step can be helpful in a better understanding of the oxidation process of isoelectronic phosphanes.     

ESR. Spectra of the Radical Ions of Indeno[1, 2, 3-cd]fluoranthene

The ESR. spectra of the radical anion and the radical cation of indeno [1, 2, 3-cd]-fluoranthene have been recorded. Their hyperfine structures are consistent with those expected on the basis of simple MO models.     

Synthesen und chemische Reaktionen von ω,ω-Bis(alkylthio)chinonmethiden des 1,6-Methano[10]annulens

Syntheses and Chemical Reactions of ω,ω-Bis(alkylthio)quinonemethides of 1.6-Methano[10]annulenes The syntheses of the donor-acceptor-substituted compounds 3 – 5 , 9 starting from 2 , 7 , or 8 , furthermore, the syntheses of 12 , 15 – 21 are described. The detailed results of ¹H- and ¹³C-NMR-spectroscopic measurements are reported.