Perturbed [12]annulenes. Synthesis of pyracylenes

Abstract

Utilizing PMO theory, pyracylene is described as a [12]annulene with an internal vinyl cross-link. As such, it should be an unusually good model for a planar [12]annulene. To examine such a hypothesis, the synthesis of pyracylene, 1,2-dibromopyracylene, and 1,2-diphenylpyracylene was achieved. The key step involved a polybenzylic bromination. After introduction of the first bromine, subsequent hydrogen atom removal involved predominantly, if not exclusively, the ¡3-hydrogen trans to that bromine. Iodide-promoted elimination of the thus formed dibromide introduced the crucial bridging double bonds. Polarographic reduction suggested the presence of an empty approximately nonbonding molecular orbital in agreement with the above model. Dramatic support arose from their nmr spectra which show the protons shifted to exceptionally high fields. These abnormal shifts are interpreted in terms of a paramagnetic ring current-in excellent accord with the proposed peripheral electronic model.

Straining strained molecules. III. The spectral and mutagenic properties and an alternate synthesis of diaceperylene and dicyclopenta[1,2,3-cd:1′,2′,3′-lm]perylene

“…We envisioned reduction of 5 to a tetra-alcohol, followed by conversion to 3,4,9,10-tetrakis(bromomethyl)perylene, and then ring closure using either PhLi (2) or Ph,P (1 1). However, we were not able to reduce 5 to the tetra-01 6 using either LiAlH,/THF or or part 11, see ref.…”

“…(16) 145. I(C-12a), 141.3(C-12b), 129.O(C-12d), 128.3(C-12c), 12 l.l(C-3(4)), 12 1 .O(C-4 (3) 2 DDQ (2,3-dichloro-5,6-dicyanoquinone) (3 17 rng, 1.4 mmol) was added to a solution of diaceperylene 1 (170 mg, 0.56 mmol) in dry, argon-degassed benzene (250 mL), and the mixture was heated under reflux for 3 h under argon. After cooling, the mixture was filtered, and the benzene evaporated to give crude product.…”

“…In this paper we investigate straining the perylene nucleus by synthesis and study of diaceperylene (I), and dicyclopenta[l,2,3-cd: 1 ',2',3'-lmlperylene ("dia~e~e r~l~l e n e " )~ (2). The latter is of especial interest in that in the same way that pyracylene (3) is a perturbed [12]annulene (2), 2 is formally a perturbed [20]annulene.…”

1,2,3,4,7,8,9,10-Octahydrodicyclohepta[de, ij]naphthalene and 2,7-dimethylpyrene: a short novel synthesis

“…These compounds have received much chemical (1,4) and theoretical (5-7) attention to ascertain their degree of 'aromatic' character. The next higher homologue 'dipleiadiene ' 4 has not yet been synthesized (for synthesis of a similar system, see ref.…”

“…Interestingly, the sequence also provides a source of 2,7-dimethylpyrene 9 for which there is only one reported synthesis with an acceptable yield (1 2). ,2,3,4,7,8,9,ij inaphtlzalme The synthesis of 8 was based on the observation that mono Diels-Alder adducts of maleic anhydride and bicycllc dienes could be converted directly to benzenoid hydrocarbons in yields of 60-70% by heating with phosphorus pentoxide (13). This procedure has been used previously by us to synthesize a series of bis meta-annelated benzenoid hydrocarbons (14).…”