Spirobinaphthopyrans: Synthesis, x-ray crystal structure, separation of enantiomers, and barriers to thermal racemization

Lončar-Tomašković, Linda; Lorenz, Klaus; Hergold‐Brundić, Antonija; Mrvoš-Sermek, Draginja; Nagl, Ante; Mintas, Mladen; Mannschreck, Albrecht

doi:10.1002/(sici)1520-636x(1999)11:5/6<363::aid-chir3>3.0.co;2-f

Cited by 12 publications

(6 citation statements)

References 17 publications

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“…2.317 Å. Furthermore, the bond lengths and bond angles around the spiro -carbon C9 of B–B are similar to the values reported for spirobinapthopyran molecule with propylene bridge …”

Section: Resultssupporting

confidence: 84%

Chemistry and Photochemistry of 2,6-Bis(2-hydroxybenzilidene)cyclohexanone. An Example of a Compound Following the Anthocyanins Network of Chemical Reactions

et al. 2014

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The kinetics and thermodynamics of the 2,6-bis(2-hydroxybenzilidene)cyclohexanone chemical reactions network was studied at different pH values using NMR, UV-vis, continuous irradiation, and flash photolysis. The chemical behavior of the system partially resembles anthocyanins and their analogue compounds. 2,6-Bis(2-hydroxybenzilidene)cyclohexanone exhibits a slow color change from yellow to red styrylflavylium under extreme acidic conditions. The rate constant for this process (5 × 10(-5) s(-1)) is pH independent and controlled by the cis-trans isomerization barrier. However, the interesting feature is the appearance of the colorless compound, 7,8-dihydro-6H-chromeno[3,2-d]xanthene, isolated from solutions of acid to neutral range, characterized by (1)H NMR and single crystal X-ray diffraction. Light absorption by 2,6-bis(2-hydroxybenzilidene)cyclohexanone solutions immediately after preparation exclusively results in cis-isomer as photoproduct, which via hemiketal formation yields (i) red styrylflavylium by dehydration under extremely acidic solutions (pH < 1) and (ii) colorless 7,8-dihydro-6H-chromeno[3,2-d]xanthene by cyclization in solutions of acid to neutral range.

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“…2.317 Å. Furthermore, the bond lengths and bond angles around the spiro -carbon C9 of B–B are similar to the values reported for spirobinapthopyran molecule with propylene bridge …”

Section: Resultssupporting

confidence: 84%

Chemistry and Photochemistry of 2,6-Bis(2-hydroxybenzilidene)cyclohexanone. An Example of a Compound Following the Anthocyanins Network of Chemical Reactions

et al. 2014

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“…Other examples in which the central carbon was linked to two oxygen in 2,2’‐spirochromene derivatives 7 and 2‐oxaindan spiropyrane derivatives 8 were reported by Mannschreck and colleagues . Spirochromene 7 was selected to illustrate the concept of enantiomeric enrichment of stereolabile chiral compounds by dynamic (D)HPLC .…”

Section: Resultsmentioning

confidence: 99%

A Forgotten Chiral Spiro Compound Revisited: 3,3'‐Dimethyl‐3H,3'H‐2,2'‐spirobi[[1,3]benzothiazole]

et al. 2015

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The title compound was obtained as a side product during dimerization-oxidation steps of the carbene generated from N-methylbenzothiazolium iodide. Chromatography on (S,S)-Whelk O1 column showed on cooling a typical plateau shape chromatogram indicating an exchange between two enantiomers on the column. The thermal barrier to racemization was determined (85 kJ.mol(-1) at 10 °C) by dynamic high-performance liquid chromatography (DHPLC).The absolute configuration of the first (M) and second eluted (P) enantiomers on the (S, S)-Whelk O1 column was established by comparing the reconstructed circular dichroism (CD) spectra from the CD detector signal and the calculated CD spectrum of the (P) enantiomer. Mass spectrometry revealed that 3,3'-dimethyl-3H,3'H-2,2'-spirobi[[1,3]benzothiazole] can be viewed as a masked thiophenate attached to a benzothiazolium framework.

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“…There are no significant differences between bond lengths and angles of those two moieties in both structures 1 and 2 as well as in the 2,2Ј-spirobi-3,3Ј-dimethylene[2H-1-benzopyran] (7). 4 In these structures, the benzene or pyridine rings, with the exception of the oxygen atoms, are nearly coplanar. The angle [C3-C2-C3Ј] around the spiro carbon atom increases with elongation of the chain in the C3-C3Ј bridge.…”

Section: Results and Discussion Crystal Structures And Conformationsmentioning

confidence: 99%

“…Also, the value for the [C3-C2-C3Ј] angle is in good agreement with the one found in the structurally related 2,2Ј-spirobibenz[d]chromene that contains an isobutylene chain in C3-C3Ј bridge, 21 as well as with that of the structurally related spirobinaphthopyrans. 4 …”

Section: Results and Discussion Crystal Structures And Conformationsmentioning

confidence: 99%

“…1 The photochromic behavior of spiropyrans is based on the reversibility between the colorless "closed" spiropyran and the colored "open" merocyanine via heterolytic cleavage of the spiro oxygen-carbon bond. 2 In continuation of our previous studies on chiral 2H-chromenes [3][4][5] and 2H-1-benzopyran-2,2Ј-indolines, 6,7 we have prepared the novel spirobipyridopyrans 1 and 2 and indolinospiropyridopyrans 3-5, containing a modified B 6 unit (Scheme 1) in order to separate their enantiomers and determine the barriers to racemization.…”

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confidence: 99%

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Spirobipyridopyrans and indolinospiropyridopyrans: Synthesis, x-ray crystal structure, separation of enantiomers, and barriers to thermal cleavage of the C(sp3)-O bond

et al. 2001

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The novel chiral spirobipyridopyrans 1 and 2 were synthesized by the acid catalyzed aldol type condensation of 5-deoxypyridoxal with the appropriate ketone and subsequent reaction of the resulting pyrylium salt with base. The indolinospiropyridopyrans 3-5, which contain the modified B(6) unit, were prepared by aldol reaction of 5-deoxypyridoxal with 1,3,3-trimethyl-2-methylenindolines. Analytical separation of enantiomers was accomplished by low-pressure liquid chromatography (LPLC) on triacetylcellulose. The barriers to thermal racemization were determined by on-line measurements of the enriched enantiomers after LPLC. Gibbs energies of activation DeltaG superset, not equals for reversible cleavage of the C(spiro)-O bond in 1, 3, and 4 were in the range 103-108 kJ/mol. The lower limits of the barriers in 2 and 5 were estimated to be greater than 102 and 109 kJ/mol by attempted thermal racemizations. The increase of the barriers from 3 to 4 and 5 was explained by the influence of electron withdrawing groups, which reduce the stability of the ring-opened transition states to C(sp3)-O bond cleavage. Geometrical data from X-ray structure analysis showed that the angle [C3-C2-C3'] around the spiro carbon atom increases with elongation of the chain in the C3-C3' bridge. This angle widening is explained by a ring-strain effect, which is greater in the five-membered ring in the skeleton of 7 than in the six- and seven-membered rings of 1 and 2.

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Spirobinaphthopyrans: Synthesis, x-ray crystal structure, separation of enantiomers, and barriers to thermal racemization

Cited by 12 publications

References 17 publications

Chemistry and Photochemistry of 2,6-Bis(2-hydroxybenzilidene)cyclohexanone. An Example of a Compound Following the Anthocyanins Network of Chemical Reactions

Chemistry and Photochemistry of 2,6-Bis(2-hydroxybenzilidene)cyclohexanone. An Example of a Compound Following the Anthocyanins Network of Chemical Reactions

A Forgotten Chiral Spiro Compound Revisited: 3,3'‐Dimethyl‐3H,3'H‐2,2'‐spirobi[[1,3]benzothiazole]

Spirobipyridopyrans and indolinospiropyridopyrans: Synthesis, x-ray crystal structure, separation of enantiomers, and barriers to thermal cleavage of the C(sp3)-O bond

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