Synthese und eigenschaften von oxydo‐p‐oligophenylenen. 18. Mitteilung über poly‐ und oligophenylene

Abstract

ZUSAMMENFASSUNG:Oxydosubstituierte p-Oligophenylene leiten sich vom Dibenzofuran ab, sind also briikkensubstituierte Oligophenylene. Ihre Darstellung erfolgte mit Hilfe der ULLMANN-Re&-tion unter Verwendung von Jodderivaten des Dibenzofurans; zu deren Darstellung dienten entsprechende Aminoverbindungen.Einige Oxydo-p-oligophenylene wurden auf der Grundlage der Kupplungs-Reaktion von o-Chlorphenyl-diazoniumverbindungen mit p-Benaochinon und nachfolgendem Oxydoringschlul3 an daraus hervorgehenden 2-Chlor-2'-hydroxybiarylen erhalten. Als weitere RingschluB-Reaktion wurde die dehydratisierende Atherspaltung von 2,2'-Dimethoxybiarylen angewandt. Damit konnte die Synthese eines Trioxydo-p-quaterphenyls, eines durchgehend uberbruckten Quaterphenylderivates, verwirklicht werden. Die Darstellung des entsprechenden Dioxydo-p-terphenyles gelang nach der EBELschen Dibenzofuransynthese.Die vollstandige oberbriickung fiihrt ZZI verminderter Loslichkeit und erhohtem Schmelzpunkt. Durch die gleichzeitige Substitution mit Methoxylgruppen war es in mehreren Fallen moglich, die Loslichkeit zu verbessern.Die Bruckensubstitution fiihrt zu langwelligen Elektronenbanden. Bei vollstandiger cberbruckung werden UV-Absorptionsbanden (Konjugationsbanden) beobachtet, die betrachtlich langerwellig sind als die der unsubstituierten Grundkorper. Von der Rotverschiebung der UV-Absorptionsbanden sind auch die Emissionsbanden betroffen: daher zeigen fast alle Oxydo-p-oligophenylene eine intensive blaue Lumineszenz. SUMMARY:Oxido-substituted p-oligophenylenes are derivatives of dibenzo€uran; thus, they are bridge-substituted oligophenylenes. Synthesis was carried out by means of the ULLMANN reaction using iodine derivatives of dibenzofuran which in turn were prepared from the corresponding amino compounds. diazonium compounds with p-benzoquinone and subsequent oxido-ring closure of the resulting 2-chloro-2'-hydroxy-biaryls. Dehydrating ether cleavage of 2,2'-dimethoxy-biaryls was applied as a further method of ring closure. Thus, synthesis of a trioxido-p-quaterphenyl a per-bridged quaterphenyl derivative was accomplished. Preparation o€ the corresponding dioxido-p-terphenyl succeeded with satisfactory yield by means of EBEL'S dibenzofuran synthesis.

Protofilaments, Filaments, Ribbons, and Fibrils from Peptidomimetic Self-Assembly: Implications for Amyloid Fibril Formation and Materials Science

“…Electrophilic aromatic iodination of dibenzofuran (1) gave 2,8-diiododibenzofuran (2) in 82% yield . Intermediate 2 was subjected to a tandem palladium catalyzed Heck cross-coupling reaction with ethyl acrylate affording the bis- α - β - unsaturated ethyl ester 2,8-dibenzofuran-bis-(ethyl-3-propionate) (3) in 99% yield. − Saponification followed by hydrogenation of diester 3 affords the C 2 symmetric 2,8-dibenzofuran-bis-(3-propionic acid) (4) in 95% yield…”

“…46 Intermediate 2 was subjected to a tandem palladium catalyzed Heck cross-coupling reaction with ethyl acrylate affording the bis-R-β-unsaturated ethyl ester 2,8-dibenzofuranbis-(ethyl-3-propionate) (3) in 99% yield. [47][48][49] Saponification followed by hydrogenation of diester 3 affords the C 2 symmetric 2,8-dibenzofuran-bis-(3-propionic acid) (4) in 95% yield. 50 Diacid (4) was converted to 2,8-dibenzofuran-bis-(pentafluorophenyl-3-propionate) (5) in 62% yield (after recrystallization) employing a dicyclohexylcarbodiimide (DCC) mediated esterification with pentafluorophenol.…”

Effects of Additional Linkers in Biphenyl-4,4‘-dinitrene on the Low-Lying Singlet−Triplet Energy Gap and Zero-Field Splitting

“…After the mixture had been cooled, 400 mL of water was added. The mixture was filtrated, washed with water, and dried to give 0.85 g (20%) of 3,7-diaminodibenzofuran as a brown solid: mp 152−155 °C (lit . 152 °C); 1 H NMR (CDCl 3 , 200 MHz) δ 3.81 (br s, 4H), 6.67 (dd, J = 8.0 Hz, J = 4.0 Hz, 2H), 6.82 (d, J = 4.0 Hz, 2H), 7.54 (d, J = 8.0 Hz, 2H); 13 C NMR (CDCl 3 , 50 MHz) δ 98.10, 111.24, 116.70, 120.16, 145.35, 157.80.…”

“…The mixture was filtrated, washed with water, and dried to give 0.85 g (20%) of 3,7-diaminodibenzofuran as a brown solid: mp 152-155 °C (lit. 14 3,7-Diazidodibenzofuran (DA4). In a 200 mL Erlenmeyer flask were placed 100 mL of water, 10 mL of concentrated hydrochloric acid, and 0.4 g (2 mmol) of 3,7-diaminodibenzofuran.…”