Neue planarchirale [2.2]Phane – Synthese, Struktur und chiroptische Eigenschaften

Abstract

Darstellung, Konformationen und chiroptische Eigenschaften der zehngliedrigen planarchiralen Naphthalinophane 4, 5 (heterocyclisch) und 6 -8 (carbocyclisch) werden beschrieben. Die Enantiomereii von 4 und 6 werden mitteldruckchromatographisch an (-)-a-(2,4,5,7-Tetranitro-9-fluoreny1idenaminooxy)propionsaure (TAPA) angereichert und polarimetrisch und circulardichrographisch untersucht. 'H-NMR-Spektren belegen die anti-Konformationen fur 4 und 6 -8, wlhrend sie fur 5 eine konformativ flexible syn-Konformation nahelegen. New Planarchiral[2.2]PhanesSyntheses, Structures, and Chiroptical PropertiesPreparation, conformations and chiroptical properties of the ten-membered, planarchiral naphthalinophanes 4, 5 (heterocyclic) and 6 -8 (carbocyclic) are described. 4 and 6 are chromalographically enriched using (-)-a-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)propionic acid (TAPA), Optical rotations and circular dichroisms of 4 and 6 are determined. The anticonformations are ascertained for 4 and 6 -8 by 'H NMR spectroscopy, whereas a conformational flexible syn conformation is supposed for 5 . Geeignete carbo-1) and h e t e r o c y~l i s c h e 2~~

Helical Porphyrinoids: Incorporation of Ferrocene Subunits into Macrocyclic Structures

“…[1] The interest in helical structures stems in part from the occurrence of screw-like motifs in important biomolecules, such as proteins, nucleic acids, or polysaccharides, and the self-assembly of helical superstructures observed in these systems has been mimicked in a variety of artificial supramolecules. [2][3][4][5][6] Alternatively, molecular helicity may result from an appropriate design of a covalent structure, best exemplified by the syntheses of numerous aromatic helicenes.…”

“…[11] Helical conformations of biliverdins and related conjugated oligopyrroles are involved in complex conformational equilibria, [16] but can be stabilized by additional bridging [17,18] or metal coordination. In particular, iron biliverdins (1), which are important intermediates in heme degradation, possess helical structures both in the solid state [19,20] and inside the active site of heme oxygenase. [21] Metallocene units possessing rotational freedom around the main axis have been used as flexible "helicity elements," for example, in ansa-bridged systems [22] and ferrocene-con-macrocycles.…”

“…[2][3][4][5][6] Alternatively, molecular helicity may result from an appropriate design of a covalent structure, best exemplified by the syntheses of numerous aromatic helicenes. [1,7] In porphyrinoid chemistry, helical structures are a consequence of macrocycle expansion [8][9][10][11][12][13][14][15] or occur in sterically congested noncyclic oligopyrroles, such as biliverdins. [16] In the case of expanded porphyrins, the helicity is associated with twisted, figure-of-eight structures, [8][9][10][11][12][13][14][15] some of which are stable enough to be separated into enantiomers.…”

Molecular Knots

“…The optical rotatory power of the free knot [(+) or (-)-(K-84) p ] was then + or -2.000°mol -1 L dm -1 . Interestingly, the demetalated knot can be considered as two intertwined helicenes and the values obtained can be compared to those measured for heterohelicenes of similar structures [84][85][86].…”

The First Enantiomerically Pure Triangulane (M)-Trispiro[2.0.0.2.1.1]nonane Is a σ-[4]Helicene

“…[4] Racemic [4]triangulane (rac-2) was first synthesized over 25 years ago, [5] and in the meantime improved syntheses [6] as well as spectral, [7] structural, [8] and thermochemical properties [9] of rac-2 are sufficiently well documented. Essentially, the C 2 -symmetric molecule of (M)-2 is a section of a helix, so that the stereochemical descriptors for helicenes [10] should also be applicable to (M)-2 and extended unbranched triangulanes 1.…”