Synthesis and Characterization of 2,7-Di(tert-butyl)pyreno[4,5-c:9,10-c′]difuran and Derived Pyrenophanes

Abstract

Isobenzofurans (IBF)s have seen widespread use in the synthesis of both natural products and polycyclic aromatic hydrocarbons. There are few examples that have two IBF entities linked in a fused aromatic ring system. Here we present the synthesis and characterization of a bis(IBF), 2,7-di(tert-butyl)pyreno[4,5-c:9,10-c']difuran. Reaction with bis(maleimide) dienophiles gives pyrenophanes. The solid-state structures of the bis(IBF) and two cyclophanes are discussed.

K‐Region‐Extended [c]‐Heteroannulated Pyrenes

“…In the parents ystem,t he [d]-, [f]-, [k]-, and [m]-bond lengthsa re between 1.43 and 1.44 . [7] All compoundsw ere investigated by UV/Vis absorption and fluorescencespectroscopy (Figure 4). However,f or In the structures with fused five-membered rings, the lengths of the inner bonds are about 1.44-1.45 for the mono-fused compounds 3a-3c and even 1.47 and 1.48 for bis-fused pyrenes 7a and 7b.U nsurprisingly,t he lengths of the fused K-edges in 3a-3c and 7a, 7b are between 1.44 and 1.49 ,and suggest that no more olefinic character remains.…”

“…The most frequently used scaffold to realize peri-fused structures is pyrene, and an umber of larger linearly annulated p-systems are based on pyrene or related systems. [7] Despite the very low yield of 2%,t his compound has even be analyzedb ysingle-crystal XRD. To the best of our knowledge,o nly two such singly fused pyrenesh ave been described in the literature, [5] mainly as precursorsf or porphyrins.…”

“…Besides theoretical discussions on this substance class, [6] only one example of synthesizinga doubly [c]-fused bis-furanopyrenew as described before. [7] Despite the very low yield of 2%,t his compound has even be analyzedb ysingle-crystal XRD.…”

“…[14] In these systemst he centralb ond (1.44 )a sw ell as the [d]-, [f]-, [k]-, and [m]-bonds (1.43-1.44 ) are much shorter than those in in 3a or 7a,a nd indicate greater delocalization of all p-electrons therein.T he fused bondsa re also in the typical range of conjugated delocalized bonds. [7] All compoundsw ere investigated by UV/Vis absorption and fluorescencespectroscopy (Figure 4). The absorption spectra of the fused compoundss how mainly one broad peak in the UV regioni ncluding af ew shoulders redshifted to the absorption maximum.…”

Synthesis of a Zigzag Carbon Nanobelt

“…3a). 36 The reactive aryne generated from halogen-magnesium exchange reaction was trapped by furan and the subsequent retro-Diels-Alder reaction mediated by 3,6-di-2-pyridyl-1,2,4,5-tetrazine afforded 4. Diels-Alder dimerization of 4 was induced in the presence of a small amount of n-BuLi (0.35 equiv of 4).…”