¹ H‐Kernresonanzverschiebungen in der Gerüstebene anisotroper CO‐, CN‐ und CC‐Doppelbindungen

Abstract

Die Synthese von Fluorenderivaten mit 2,7-und 1 ,I-Dirnethyl-sowie 2-Fluor-und 2,7-DifluorSubstituenten wird beschrieben. Durch Analyse und Vergleich ihrer NMR-Spektren zeigt sich, da13 lH-Atomkerne in Doppelbindungsebenen bei geringeren Magnetfeldstarken absorbieren als in Vergleichsverbindungen ohne entsprechende Doppelbindung. Modellverbindungen mit Tetralin-und Indan-Struktur fuhren zum gleichen SchluR. Die Bedeutung konjugativer Substituenteneinfliisse und elektrischer Feldeffekte wird anhand von Verschiebungslnderungen bei der Protonierung beurteilt.

Polymorphism Versus Thermochromism: Interrelation of Color and Conformation in Overcrowded Bistricyclic Aromatic Enes

“…166-167 8C (decomp) [76] 9-Diazo-2,7-dimethyl-9H-fluorene (16): Diazofluorene 16 was prepared according to a literature procedure. [76] Anhydrous sodium sulfate (0.511 g, 3.60 mmol), yellow mercury oxide (1.608 g, 7.43 mmol), and 2,7-dimethyl-9H-fluoren-9-one hydrazone (15) (1.000 g, 4.49 mmol) were carefully ground by using a mortar, transferred to a round-bottomed flask equipped with magnetic stirrer and drying tube, and dry diethyl ether (25 mL) was added. Upon dropwise addition of a freshly prepared saturated solution of KOH in ethanol (0.5 mL), the reaction mixture turned deep red.…”

“…Ketone (13) was reacted with hydrazine hydrate in ethanol to give 2,7-dimethyl-9H-fluoren-9-one hydrazone (15), which was oxidized with yellow mercury oxide to 9-diazo-2,7-dimethyl-9H-fluorene (16). [76,77] Ketone (14) was converted to 9H-xanthene-9-thione (17) [78] with Lawessons reagent, and reacted with (16) in boiling benzene to give the intermediate thiirane 2,7-dimethyl-dispiro-(9H-fluorene-9,2'-thiirane-3',9''-[9H]-xanthene) (18). The thiirane sulfur was eliminated with triphenylphosphine [71] in boiling benzene to give the purple 9-(2,7-dimethyl-9H-fluoren-9-ylidene)-9H-xanthene (11) (Scheme 1), which was purified by chromatography with a yield of 67 %.…”

Reaction of the Silver Salts of Arylnitroacetonitriles with 9‐Bromofluorene Synthesis of 9‐(α‐Cyanoarylidene)fluorenes

“…This is explained assuming that the upfield signal corresponds to I-H standing Z to the aryl group, which should be out of coplanarity with respect to the remaining system, thus causing an upfield shift of the adjacent fluorenyl proton signal of about 1 ppm. An analogous situation has been found in other arylidenefluorenes 16).…”