Cyclisch konjugierte 5‐ und 7‐Ringsysteme, II¹⁾ 6‐Amino‐ sowie 6‐Hydroxy‐Fulvene und deren Aza‐Analoga

Abstract

Durch nucleophile Substitution werden 6-Dialkylamino-f ulvene in 6-Amino-fulvene sowie Acylcyclopentadiene oder deren Derivate ubergefuhrt. Mit einigen der von MEERWEIN beschriebenen Carbonium-Oxonium-Immonium-Salzen reagiert Cyclopentadien-natrium unter Bildung von 6.6-disubstituierten Fulvenen. Die Reaktivitat sowie die UV-Spektren und Dipolmomente der so erhaltenen, gekreuzt konjugierten Keten-acetale und -aminale zeigen den starken EinfluB von Substituenten am exocyclischen C-Atom auf die cyclische Konjugation der Fulvene. Die leicht zuganglichen, bisher unbekannten 6-Amino-6-aza-fulveneHydrazone des monomeren Cyclopentadienons -gleichen in ihren Eigenschaften den 6-Amino-fulvenen.Fulvenen mit funktionellen Gruppen am exocyclischen C-Atom kommt als Ausgangsstoffen fiir Synthesen zahlreicher, den 5-Ring enthaltender bi-und polycyclisch konjugierter, nicht-benzoider Systeme besonderes Interesse zu4). Von einem Studium der chemischen und physikalischen Eigenschaften dieser Fulvene waren weitere Informationen iiber die Bindungsverhaltnisse des gekreuzt konjugierten Systems sowie iiber den SubstituenteneinfluR auf die cyclische Konjugation des carbocyclischen 5-Rings zu erwarten4-6).

(η4-Tetraarylcyclobutadiene)(η5-formylcyclopentadienyl)cobalt(I) complexes: Facilities to finetune the electron-donating capability in dipolar organometallics

“…Hamburg. Formylcyclopentadienyl sodium [23], formylcyclopentadienyl thallium [24], tris(triphenylphosphine)-cobalt(I) chloride [25], and the p-substituted diarylethynes [26] were prepared according to the literature procedures.…”

Structural Features of Primary 6-Aminopentafulvenes and Some of Their Derivatives

“…The synthesis of 6-amino-6-methylpentafulvene (2) was carried out as described by Hafner et al [24] For this purpose 6-(dimethylamino)-6-methylpentafulvene (1) was treated for a prolonged time (7 d) at elevated temperature (40°C) with NH 3 . In an addition/elimination reaction sequence the product 2 was formed by extrusion of dimethylamine.…”

“…The reagents 1, 3a, and 3b were prepared according to the literature. [24,38] N,NDibenzylalanine, -valine, and -leucine used for the generation of the reagents 6a, 6b, and 6c were synthesized as described in the literature. [32,33] Ϫ For instrumentation used for the characterization of the compounds, including a list of spectrometers used, see e.g.…”

“…Preparation analogous to a procedure described previously by Hafner et al [24] A steel autoclave was charged with 6-dimethylamino-6-methylpentafulvene (1), and then precooled (Ϫ78°C) liquid NH 3 (ca. 200 mL) was carefully added at Ϫ78°C.…”

“…Surprisingly, the essential parent systems such as 6-amino-6-methylpentafulvene (2) seem not to have been characterized by X-ray diffraction so far, although these very useful organic compounds have been known for many years. [24] We, therefore, have characterized compound 2 (see Scheme 1) by X-ray crystal structure analysis, and we have prepared two series of derivatives of 2, that contain electron-withdrawing substituents attached either at the carbocyclic ring system or the nitrogen center, and studied the systematic structural variations caused by these electronic consequences of the general 6-aminopentafulvene system. The preparations and the X-ray crystal structure analyses of these examples are described in this article along with a structural characterization of the parent 6-amino-6-methylpentafulvene 2.…”