Ueber ein neues Reduktionsprodukt des Xanthons

Gurgenjanz, G.; Kostanecki, v.

doi:10.1002/cber.189502802219

Cited by 37 publications

(11 citation statements)

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“…1) have fascinated chemists since the parent BAE bifluorenylidene (1) was synthesized in 1875 [5]; dixanthylene (2) was synthesized in 1895 [6]; and thermochromism, piezochromism, and photochromism were revealed in bianthrone (3) [7,8] and dixanthylene (2) [9]. BAEs are defined by the general structure shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The BAEs are attractive substrates for the study of the ground-state properties and dynamic stereochemistry of overcrowded polycyclic aromatic enes (PAEs) and for their thermochromic, photochromic, electrochromic, and piezochromic behavior [2]. The homomerous BAEs dithioxanthylene (4) [10], diselenoxanthylene (5) [11], and ditelluroxanthylene (6) [12] are not thermochromic. Heteromerous derivatives of 2 and 4 and related overcrowded enes serve as candidates for chiroptical molecular switches and molecular motors [13].…”

Section: Introductionmentioning

confidence: 99%

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Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

et al. 2014

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The syntheses, molecular and crystal structures, NMR spectroscopic study, and DFT computational study of naphthologs of mono-bridged (X = -, O, S, Se, and Te) tetraarylethene (BAE-1s) 11-25 with a,a-, b,b-, and a,b-dinaphthalenyl substituents have been reported. The BAE-1s have been prepared by Barton-Kellog twofold extrusion from the respective chalcogenothiones and diazomethylenebisnaphthylenes. Complete assignments of 1 Hand 13 C-NMR spectra of 11-25 have been made through 2-dimensional correlation spectroscopy (DQF-COSY, HSQC, HMBC, and NOESY). The corresponding intermediates, thiiranes 33-47, have been also isolated (except 38), and their molecular and crystal structures have been determined. The molecular structures of BAE-1s 12-15, 20, and 22-25 adopted folded-twisted conformations with considerably folded (u = 30°-57°) tricyclic moieties. The a,a-and a,b-dinaphthalenyl derivatives are more overcrowded than b,b-dinaphthalenyl derivatives. The relief of the steric strain due to the overcrowding around C 9 = C 9 0 caused by the presence of naphthalenyl substituents was achieved by their twisting around the single bonds that connect the a-naphthalenyl and b-naphthalenyl moieties to C 9 0 . The 1 H-NMR spectra have shown shielding of H 2 , H 7 of 11-25 and the pronounced deshielding of H 8 0 , H 8 00 of a,a-dinaphthalenyl-substituted BAE-1s 13-15 in contrast to b,b-dinaphthalenyl-substituted BAE-1s 16-20. The upfield shifts of H 2 , H 7 suggested conformations in which these hydrogens are located above the planes of the opposing naphthalene rings. DFT calculations of 11-20 have been performed at B3LYP/6-31G(d) and B3LYP/ SDD. The results have shown that the global minima of BAE-1s without a chalcogen bridge 11 and 16 are twisted (-sc,-sc)-C 2 -t conformations. The global minima of BAE1s with a chalcogen bridge are folded-twisted (-sc,-ac)-C 1 -ft conformations for a,a-dinaphthalenyl-substituted BAE1s 12-15 and either anti-or syn-(-sc,ac)-C 1 -ft conformations for b,b-dinaphthalenyl-substituted BAE-1s 17-20. The pronounced differences between the a,a-dinaphthalenyl and the b,b-dinaphthalenyl derivatives are noted. Dispersion-corrected B3LYP calculations stabilize significantly the a,a-dinaphthalenyl derivatives versus the b,b-dinaphthalenyl derivatives. The geometrical parameters of BAEs-1 11-15 and 20, derived from their molecular X-ray structures and from their B3LYP-optimized geometries are in a good agreement.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

et al. 2014

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“…Here we report syntheses, molecular and crystal structures, and an NMR spectroscopic study of the following analogs of BAEs: 9,9 0 -di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9 0 -di-(1-naphthylmethylene)-9H-xanthene (6), as well as a DFT study of the conformational spaces of 5 and 6 and their constitutional isomers 9,9 0 -di-(2-naphthylmethylene)-9H-fluorene (7) and 9,9 0 -di-(2-naphthylmethylene)-9H-xanthene (8). The molecular and crystal structure of the related 3 0 ,3 0 -di(1-naphthyl)-spiro[9H-fluorene-9,2 0 -thiirane] (11) is also reported.…”

Section: Introductionmentioning

confidence: 99%

“…1, X, Y: -) was synthesized in 1875 [5], dixanthylene (2) (Fig. 1, X, Y: O) was synthesized in 1895 [6] and thermochromism [7][8][9][10][11] and photochromism [12,13] were revealed in bianthrone (3) (Fig. 1, X, Y: C=O) [14,15].…”

Section: Introductionmentioning

confidence: 99%

Overcrowded naphthologs of mono-bridged tetraarylethylenes: analogs of bistricyclic aromatic enes

et al. 2009

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The naphthalogous mono-bridged tetraarylethylenes 9,9 0 -di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9 0 -di-(1-naphthylmethylene)-9H-xanthene (6), analogs of bifluorenylidene (1) and bixanthenylidene (2), have been synthesized and their molecular and crystal structures have been determined. Ene 5 has been prepared by two alternative synthetic routes. The molecular structures of 5 and 6 show that each of these enes has very small twist around the central double bond, but the two naphthalene rings in both 5 and 6 are highly twisted. According to the NMR study, 5 and 6 in solution adopt conformations which are similar to those found by X-ray crystal structure analysis. The notable upfield shifts of H 1 and H 8 (6.11 and 6.83 ppm, respectively) and H 2 and H 7 (6.70 and 6.44 ppm, respectively) in 5 and 6 are due to the shielding caused by the nearly orthogonally twisted naphthalene rings. The B3LYP/6-31G(d) calculations of 5, 6, and their 2-naphthyl and phenyl analogs have been performed. In the 1-naphthyl series, the more efficient conjugation between the naphthyl substituents and the central C=C and the overcrowding due to the peri-hydrogen atoms lead to higher twists of the naphthyl groups and to lower twists of the central C=C. In the 2-naphthyl series, the opposite effects are noted.

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“…The bistricyclic aromatic enes [1,2] (1) have fascinated chemists since bifluorenylidene (2) was synthesized in 1875, [3] dixanthylene (3) was synthesized in 1895, [4] and thermochromism and piezochromism were revealed in bichromic B conformer are identical. Syn-folded conformers of bistricyclic enes with central six-membered rings have been reported as metastable conformations Ϫ the photochromic E form Ϫ in the cases of, for example, 10,10Ј-dimethylbiacridan (8) (1, X,Y: NCH 3 ), dithioxanthylene (9) (1, X,Y: S), and the methylene-bridged bistricyclic ene 10 (1, X,Y: CH 2 ).…”

Section: Introductionmentioning

confidence: 99%

Conformational Space and Dynamic Stereochemistry of Overcrowded Homomerous Bistricyclic Aromatic Enes − A Theoretical Study

2001

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The conformational spaces and dynamic stereochemistry of representative overcrowded homomerous bistricyclic aromatic enes (1, X = Y) are investigated, applying the semiempirical PM3 method. The experimental energy barriers for E,Z isomerizations, enantiomerizations, and conformational inversions of 1 and related compounds, derived from DNMR and other kinetic studies, are reviewed. This study focuses on the analysis of the minima, transition states, and dynamic mechanisms of the conformational isomerizations of bifluorenylidene (2), dixanthylene (3), dithioxanthylene (9), and bi-5H-dibenzo[a,d]cyclohepten-5-ylidene (11). The four representative bistricyclic enes differ in the sizes of their central rings and in their bridging groups. The mechanisms of the interconversions

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Ueber ein neues Reduktionsprodukt des Xanthons

Cited by 37 publications

References 0 publications

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

Overcrowded naphthologs of mono-bridged tetraarylethylenes: analogs of bistricyclic aromatic enes

Conformational Space and Dynamic Stereochemistry of Overcrowded Homomerous Bistricyclic Aromatic Enes − A Theoretical Study

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