Angewandte Chemie International Edition
10.1002/anie.202102719
RESEARCH ARTICLE
number, acceptor number, dielectric constant, dipole moment,
refractive index, polarizability, viscosity, specific heat capacity,
relative polarity, E (30) polarity scale, molecular weight, density
T
crowded alkenes, solvent properties scales, enantioenrichment
reactions, asymmetric or stereoselective reactions, for example,
in a search for suitable functionalization conditions (e.g. solvent
type, temperature) for chiral-meso interconvertible molecules in
order to obtain targeted stereochemical structure of a product.
or Hildebrand and Hansen solubility parameters were
investigated. However, no significant correlation across all
solvents was found. The correlations for non-aromatic and
aromatic solvents, when analyzed separately, show three
moderate correlations between Kt/c and the solvents' refractive
index, viscosity (Figure 5b,c) or polarizability (see Figure S32b).
To explain the mechanism of solvent-induced cis/trans
interconversion, we have performed MD simulations on FDF
molecule in all studied solvents at 25 °C (for details, see Section
Acknowledgements
We are grateful to Dr. Takeshi Yasuda (NIMS), Dr. Takashi
Kajitani (Tokyo Tech.), and Prof. Takanori Fukushima (Tokyo
Tech.) for their efforts on the physicochemical studies of FDF in
the solid states. Dr. Manas Bera (NIMS) is greatly acknowledged
for his contribution in the initial stages of this work. This research
was supported by KAKENHI Grant-in-Aid for Scientific Research
1
0 in Supporting information). It turned out that the alkyl side
chains play a critical role in the observed behaviour. Aromatic
non-polar solvents keep the alkyl chains solvated and in extended
form, making the cis-form enthalpically favoured. Contrarily, polar
non-aromatic solvents show repulsive interactions towards alkyl
chains, which tend to shrink and sterically interact between
themselves. It induces entropic force towards conformation
change to the state with higher entropy (i.e. trans-form with higher
surface area and alkyl chains more apart. Overall, the solvent-
induced interconversion is attributed mainly to the solvophobic
interactions between solvent molecules and peripheral alkyl
chains. Moreover, the MD simulated tendencies are in good
agreement with experimentally observed data (compare Figure
(
No. 19K05229 for J.L.); Innovative Areas "π-System Figuration"
Grant (No. 26102009 and No. 15K21721 for M.T.) from JSPS;
Grant-in-Aid for Transformative Research Areas (A) "Condensed
Conjugation" from MEXT (20H05868 for M.T.); and the MEXT
"NIMS Molecule and Material Synthesis Platform" program.
Conflict of interest
The authors declare no conflict of interest.
5
a and Fig. S39).
Finally, we studied the H NMR spectra upon changing the
volume fraction of toluene-d in CDCl (Tol), because two solvents
toluene-d and CDCl3) exhibit a strong preference of FDF for cis-
1
8
3
Keywords: conformation analysis • crowded alkene • chirality •
diastereomers • solvent effects
(
8
or trans-isomer, respectively (Figure S34). The plot of the
extracted Kt/c values has nonlinear but continuous dependence of
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In conclusion, we have shown that FDF aromatic hydrocarbon
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48-754.
with the DFT calculations, a comprehensive kinetic description of
FDF conformational behaviour was presented. It was shown that
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