Synthesis, characterization, and molecular structure of [6](9,10)anthracenophane and its peri-substituted derivatives: The smallest 9,10-bridged anthracenes

Yoshito Tobe*, Shinji Saiki, Naoto Utsumi, Takuji Kusumoto, Hideaki Ishii, Kiyomi Kakiuchi, Kazuya Kobiro, Koichiro Naemura

*Corresponding author for this work

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

[6](9,10)Anthracenophane (1a) was synthesized by the benzoannelation method starting from dibromo[6]paracyclophane 6 via diepoxyanthracenophanes 3a and 4a. In a similar fashion, peri-substituted derivatives, tetramethyl (1b) and tetraphenyl (1c), were synthesized through the corresponding diepoxyanthracenes 3b, 4b, and 3c. Molecular structures of tetramethyldiepoxyanthracenophanes 3b and 5b are discussed with regard to the Mills-Nixon effect on the basis of their X-ray structure analyses. The parent anthracenophane 1a is extremely air- and acid-sensitive, so it is characterized spectroscopically as a mixture containing its dihydro derivative 8a. The perisubstituted derivatives 1b and 1c are more stable than 1a, and are fully characterized by spectroscopic methods and X-ray crystallographic analyses. X-ray structures reveal that the out-of-plane deformation angles of the bridged aromatic ring of 1b and 1c are the largest observed in any short-bridged [n]cyclophanes. Semiempirical AM1 calculations indicate that the out-of-plane deformation of the aromatic rings 1b and 1c is more severe than that of 1a due to the steric repulsion between the benzylic methylenes and the peri substituents. That the kinetic stability observed for 1b and 1c was greater than that of 1a is, therefore, ascribable to the steric protection of the reactive bridgehead carbons by the peri substituents. Acid-catalyzed rearrangement of 1a-c gave the corresponding methylenedihydroisomers 2a-c, which represent the first examples of bridged methylenedihydroanthracenes. Photochemical isomerization of 1b and 1c took place readily, giving the corresponding Dewar anthracenes 11b and 11c. Thermal cycloreversion of 11b and 11c gave the cyclophanes 1b and 1c with E(a) values of 22.3 and 25.4 kcal/mol, respectively.

Original languageEnglish
Pages (from-to)9488-9497
Number of pages10
JournalJournal of the American Chemical Society
Volume118
Issue number40
DOIs
StatePublished - 9 Oct 1996

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