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Synthesis, Molecular Structure, and Chiroptical Properties of Dibenzylidene Derivatives of Bicyclo[3.3.1]nonane and Brexane
Author(s) -
Stončius Sigitas,
Neniškis Algirdas,
Loganathan Nagarajan,
Wendt Ola F.
Publication year - 2015
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.22480
Subject(s) - chemistry , nonane , bicyclic molecule , computational chemistry , stereochemistry , organic chemistry
Synthesis of several enantiomerically pure unsaturated bicyclo[3.3.1]nonane and related brexane (tricyclo[4.3.0.0 3,7 ]nonane) derivatives bearing exocyclic benzylidene substituents from readily available (+)‐(1 S ,5 S )‐bicyclo[3.3.1]nonane‐2,6‐dione was accomplished. Molecular geometry and chiroptical properties of compounds with enone and styrene chromophores were studied by X‐ray diffraction analysis, molecular modeling , and circular dichroism (CD) spectroscopy. Difunctional 3,7‐dibenzylidenebicyclo[3.3.1]nonanes, such as 2 and 7 , 8 , 9 , exhibited intense CD couplets, arising from the exciton coupling between the two unsaturated chromophores. The observed negative sign of the exciton couplets is congruent with the negative twist (negative chirality) defined by the two interacting transition dipoles. The sign of the Cotton effect corresponding to the π→π* transitions in the CD spectra of monoenone 4 and tricyclic brexane acetate 11 was correlated with the intrinsic dissymmetry (helicity) of the styrene chromophore. Chirality 27:728–737, 2015 . © 2015 Wiley Periodicals, Inc.