Die Polyine

Abstract

Die Untersuchung der Inhaltsstoffe verschiedener Vertreter der Gattung Curlina L. zeigt, daB diese Gattung neben bereits bekannten Verbindungen mehrere neue Substanzen (10,15,16,ZO) enthalt, die in ihrer Struktur geklart werden konnten. Biogenetisch sind alle Verbindungen recht eng miteinander verwandt.In1 Tribus Cynareae sind das En-tetrain-en 1 sowie das Pentain-en 2 und ihre Folgeprodukte sehr weit verbreitet 2). Eine Ausnahme machen lediglich die Arten des Subtribus Cctrlininae. Die Gattung Xeranthemum enthalt vor allem Thiophenderivate vom Typ 3*), wahrend man aus Arten der Gattung Atractylis das Furanderivat 42) sowie das En-triin-dien-acetat 5 isoliert. Das Acetat 5 kommt auch in den Wurzeln von Carlina vulgaris L.3) vor, die Konfiguration war jedoch unklar. Das trans.transIsomere ist in Coreopsis-und Cosmos-Arten enthaltenz), es ist verschieden von dem Acetat aus Carlina vulgaris.

Carbyne: The Molecular Approach

“…[55] The answer to this question (and others) required a rather significant set of X-ray crystallographic data, ideally for molecules within the same series of polyynes. While we had some success with the TIPS[n] polyynes, [44] including a structure of TIPS [8], which was only the second known octayne structure at the time, [56] we lacked enough data to make a meaningful conclusion for this series. Success, on the other hand, came to Wes Chalifoux with the tBu[n] series, [32] for which crystal structures could be obtained for n = 2-4, 8, and 10.…”

“…In any case, after a flurry of work in the 1950s [8][9][10] and 1970s, [11,12] followed by somewhat of a hiatus, the question of carbyne and polyynes emerged again in the 1990s, sparked in part by marvelous acetylenic structures reported by the groups of, for example, John Gladysz, [13,14] Uwe Bunz, [15,16] Yoshito Tobe, [17,18] Yves Rubin, [19] Larry Scott, [20] and, of course, François Diederich, [21][22][23][24] as well as others. [25] In 1997, I started at the University of Alberta with my own research group, and my thoughts returned quickly to polyynes, and how one might form polyynes.…”

“…Early work from the groups of Bohlmann, Jones, Walton, and others afforded several oligomeric series, with sp-carbon chains as long as -(C≡C)16-, but characterization was limited. [8,11,12] Traditional methods for polyyne synthesis, in most cases, required the prior assembly of a terminal alkyne/polyyne as one or both of the precursors to assemble a longer product. This may not be a problem for all polyyne synthesis, but it was easily predictable that instability would eventually become an insurmountable problem.…”

“…This work was led by Sara Eisler and undergraduate Erin Elliott, who assembled triisopropylsilyl-endcapped polyynes TIPS[n] (n = number of acetylene units) containing 2-6, 8, and 10 acetylene units in a few steps based on the general FBWr protocol ( Figure 5). [44] This included the stable polyynes TIPS [8] and TIPS [10], which allowed for a more thorough analysis of structural, physical, and optical properties based on length. The TIPS[n] series was used to explore, for the first time, the potential of a series of polyynes as third-order nonlinear optical (NLO) materials.…”

Oligomers from sp-Hybridized Carbon: Cumulenes and Polyynes

“…Early work by Kuhn and coworkers [22][23][24][25][26][27], and later by Bohlmann and coworkers [28][29][30][31], targeted the cumulenes, but these efforts were hampered by the rather frustrating instability shown by these compounds. Nevertheless, a number of remarkable synthetic efforts provided several series of cumulenes, including the [n]Ph and [n]Cy series (where n is the number of cumulated double bonds), which were extended to the point of [9]cumulenes (Fig.…”