Allene in molekularen Materialien

Abstract

Dieser Kurzaufsatz liefert eine kritische Übersicht über die Entwicklung allenhaltiger fortschrittlicher Funktionsmaterialien. Ausgehend von Entwurf und Synthese stabiler, enantiomerenreiner Bausteine wird eine Vielfalt von Systemen – wie formstabile Makrocyclen, Foldamere, Polymere, Charge‐Transfer‐Chromophore, Dendrimere, Flüssigkristalle und redoxschaltbare chirale Chromophore – bezüglich ihrer Herstellung, Eigenschaften und möglichen Anwendungen diskutiert. Ziel der Zusammenstellung ist es, einen Anreiz zur verstärkten Anwendung enantiomerenreiner Allene beim rationalen Entwurf neuer Funktionswerkstoffe zu liefern.

Unexpected Formation of a [4]Radialene and Dendralenes by Addition of Tetracyanoethylene to a Tetraaryl[5]cumulene

“…Thus, our attention turned to identification of product B. Viehe and co-workers [23] had shown that polarized [3]cumulenes could be efficiently trapped by reaction with bromine. As the study progressed, it became clear that product B (Scheme 2) is not stable, and transforms to products A and C in a ratio of about 9:1 over time, on warming, or concentration of the reaction mixture.…”

“…Thus, our attention turned to identification of product B. Viehe and co-workers [23] had shown that polarized [3]cumulenes could be efficiently trapped by reaction with bromine. Compound 14 is not, unfortunately, a product that is easily linked to the presence of [3]cumulene 9 during the reaction of 7 with TCNE. (2)].…”

“…The fractions containing product B were stored at low temperature (i.e. Cyclization of rotamer 17' then affords [3]dendralene 11. 250 mL) were reduced to less than 1 mL under vacuum, and NMR spectra were acquired.…”

“…The cycloaddition reaction of a tetraaryl [5]cumulene with the electron-deficient olefin tetracyanoethylene affords unusual products, including functionalized dendralenes and alkylidene cyclobutanes, as well as a symmetric [4]radialene that shows unique solvatochromism, with l max values approaching the near-IR region. [2] The chemistry and reactivity of lower [n]cumulenes, namely, n = 2 (allenes) [3] and n = 3 (butatrienes), [4,5] has been explored in recent years, but longer [n]cumulenes (n ! The cycloaddition reaction sequence has also been explored by mechanistic and theoretical studies.…”

A Versatile Synthesis of β‐Lactam‐Fused Oxacycles through the Palladium‐Catalyzed Chemo‐, Regio‐, and Diastereoselective Cyclization of Allenic Diols

“…Though this mode of reactivity has previously been reported for allenols, similar reactions for the corresponding allenic diols have remained largely unexplored. [4] The discovery of new reactivity and principles for controlling chemo-, regio-and stereoselectivity is a fundamental task for organic synthesis. Both the enormous potential of confrontation of two functional groups that are either reactive or inert (chemoselectivity) and the preferential reaction with one direction of bond-making (regioselectivity) joined to the possibility of stereocontrol can all be encountered in the heterocyclization reaction of allenic diols.…”