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Chromatographic Resolution, Circular Dichroism Spectra, Absolute Configurations, and Crystal Structures of Bridged Biphenyls, Containing Sulfide, Sulfoxide, and Sulfone Groups in the Bridge
Author(s) -
LončarTomašcović Linda,
ŠaracArneri Ruža,
HergoldBrundić Antonija,
Nagl Ante,
Mintas Mladen,
Sandström Jan
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(20000216)83:2<479::aid-hlca479>3.0.co;2-w
Subject(s) - chemistry , enantiomer , cndo/2 , circular dichroism , racemization , bathochromic shift , absolute configuration , cotton effect , crystallography , sulfoxide , stereochemistry , molecule , organic chemistry , physics , quantum mechanics , fluorescence
Four chiral 1,1′‐biphenyls with one or two sulfur‐containing bridges in 2,2′‐ or 2,2′‐ and 6,6′‐positions, viz . 1,11‐dimethyl‐5,7‐dihydrodibenzo[ c , e ]thiepin ( 1 ), its S ‐oxide ( 2 ) and S , S ‐dioxide ( 3 ), and the doubly bridged 10,12‐dihydro‐4 H ,6 H ‐[2]benzothiepino[6,5,4‐ def ][2]benzothiepin ( 4 ) have been studied by chromatography, CD spectroscopy, X‐ray crystallography, and empirical force‐field and CNDO/S calculations. The structures obtained by force‐field calculations showed good agreement with the crystal structures determined for 2 and 3 . Compounds 2 , 3 , and 4 , but not 1 , could be resolved into enantiomers by chromatography on swollen microcrystalline triacetylcellulose. The barrier for biphenyl inversion in 2 was found to be higher than 167 kJ⋅mol −1 by an attempted thermal racemization. The CD spectra of the enantiomers of 2 – 4 were recorded and resolved into individual bands, and the corresponding rotational strengths were calculated. The transitions showed considerable similarity to those of a 1,1′‐biphenyl with hydrocarbon bridge ( cf. 5 ), albeit with bathochromic shifts, which permitted the assignment of the absolute configurations of the enantiomers of 2 – 4 . The assignments were supported by comparison of the experimental CD spectra with spectra calculated by the CNDO/S method. All first‐eluted enantiomers were found to have the ( S )‐configuration.