π-Conjugated Benzoperylenes: Sequential C–S Bond Cleavage and Charge Distribution Patterns of the Anions

Abstract

Chemical reduction of polyaromatic hydrocarbons yielded solutions of long‐lived polyanionic species. Reduction of a sulfur heterocycle afforded a stable sulfur‐containing dianion. Sulfur extrusion from this dianion proceeded upon further contact with the reducing metal. NMR and UV studies indicate a sulfur extrusion mechanism different than that previously observed in THF. Electron transfer to the already reduced hydrocarbon skeleton results in the stepwise cleavage of the two C–S bonds and the extrusion of a sulfur atom. Dimers of aromatic hydrocarbons such as pyrene and phenanthrene have been reduced as well. The interplay between coulombic repulsions and resonance energies is described.

π-Conjugated Anions: From Carbon-Rich Anions to Charged Carbon Allotropes

“…This gain/loss pattern, by which localization requires planarity but imposes repulsive interactions, is at an overall favorable state with the gain in delocalization or resonance energy compensating the increase in coulombic repulsions. [79] The degree of electron delocalization over the whole dimer varies with changes in charge localizations at the inter-ring positions. Lowering of the charge densities at these positions by extension of the surface for potential delocalization (as in going from phenanthrene subunits to pyrene units) results in a greater separation between the two subunits and hence a lower conjugation.…”

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

“…Most typically, a C−C bond is formed, although other bond types can also be obtained (e.g., C−B, Scheme 17; C−N, 43.7; N−N, 43.4; C−O, 90.2, 98.7, Schemes 96, 97; C−S, 99.2). The new ring, which may be carbo-or heterocyclic, is usually six-membered, although five- (196.4, 197.3; Charts 59, 60; Schemes 263,264,273,275,276), seven-(Schemes 13,156,157,186), and eight-membered rings (Scheme 162; 158.8, 164.3, 206.8, 268.3) have also been prepared. Nevertheless, when rings other than 6-membered are targeted, rearrangements may occur (cf., 33.3).…”

“…Desulfurization of 53.2 with Raney nickel produced dibenzoperylene 53.3 in moderate yield . The mechanism of potassium-induced desulfurization of 53.2 was investigated in 1999 by Rabinovitz et al Zander and Franke reported an alternative route to 53.2 involving sequential thermal desulfurization–dehydrogenation of tetrabenzothianthrene 53.4 . They additionally showed that the thiophene ring could be reintroduced to 53.3 using direct reaction with elemental sulfur.…”

Catalytic Reductions Without External Hydrogen Gas: Broad Scope Hydrogenations with Tetrahydroxydiboron and a Tertiary Amine

“…(In some reactions small amounts of the known 9,9'-biphenanthrene was isolated. [59] ) Similar conditions, with any noted variations, were used for the other transformations.…”

“…Purification on a silica column packed in hexanes and eluted with hexanes gave 177.5 mg (99% yield) of compound 1 as a white solid. (In some reactions small amounts of the known 9,9′‐biphenanthrene was isolated …”