Synthesis, Crystal Structure, and Circular Dichroism Spectra of (1S)-4,8-Diphenylbarbaralane-2,6-dicarbonitrile – Chiroptical Properties of the Transition State of a Degenerate Cope Rearrangement
✍ Scribed by Helmut Quast; Maximilian Seefelder; Eva-Maria Peters; Karl Peters
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 543 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-193X
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✦ Synopsis
Diphenylbicyclo[3.3.1]
nonane-2,6-dione rac-3 is resolved in torsional angles in the crystal. The molecular structures of (1S)-1 and (1S)-3 closely resemble those of the corresponding 57 % overall yield by chromatographic separation of the diastereomeric (R)-N-(1-phenylethyl)carbamates 9 which are racemates investigated previously. These results show (i) that intermolecular interactions in the solid state are of minor obtained from (R)-(1-phenylethyl) isocyanate ( 8) and the 6hydroxydiphenylbicyclo[3.3.1]nonan-2-ones endo-and exo-importance and (ii) that the unusually long C2-C8 distance of (1S)-1 and rac-1 (168 pm) is a molecular but not an averaged 4. The enantiomers (1R)-(e.r. = 98:2) and (1S)-3 (e.r. = 97:3) are regenerated from 9 by reduction with lithium aluminium property due to a non-degenerate Cope rearrangement in the crystal. CD spectra are reported for (1R)-and (1S)-3, the hydride followed by Swern oxidation of the resulting diols 5. The title compound (1S)-1 is synthesised in three steps from unsaturated dicarbonitrile (1S)-13, and (1S)-1. The CD spectrum of (1S)-1 exhibits a weak positive band at 459 nm (1S)-3 in improved yield on the route that had led to rac-1. The absolute configurations are established by X-ray where rac-1 shows a temperature-dependent absorption which has been assigned to the higher, vibronic state diffraction analyses of the carbamates endo-(1R)-9 and exo-(1S)-9. X-ray diffraction analyses were also performed of the represented by rac-1*. The intensity of the weak CD band depends on the temperature and the solvents in the same camphanoate (1R)-7, the intermediates rac-endo-4 and (1S)-3, and the title compound (1S)-1. Hydroxy ketone rac-endo-way as the UV/Vis absorption of rac-1. This supports the conclusion that both bands originate from the same source, 4 adopts similar conformations in the solid state and in solution as shown by a comparison of vicinal 1 H, 1 H coupling viz. the transition state 1* of the degenerate Cope rearrangement 1 o 1Ј. constants from proton spectra with those calculated from sorption around 450 nm. [4] The increase of this band with