Russian Journal of Organic Chemistry, Vol. 41, No. 1, 2005, pp. 47-53. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005,
pp. 51-56.
Original Russian Text Copyright Ó 2005 by Turov, Bondarenko, Tkachuk, Khilya.
Conformational Mobility of Substituted 2-Methoxychalcones
under the Action of Lanthanide Shift Reagents
A. V. Turov, S. P. Bondarenko, A. A. Tkachuk, and V. P. Khilya
Taras Shevchenko Kiev National University, ul. Vladimirskaya 64, Kiev, 01033 Ukraine
e-mail: vkhilya@hotmail.com
Received March 27, 2003
AbstractVarious lanthanide shift reagents Ln(fod) were found to affect the conformational composition of
3
2
-methoxychalcones. Coordination of Yb(fod) occurs mainly at the carbonyl oxygen atom of the substrate, while
3
Eu(fod) and shift reagents derived from other lanthanides coordinate substituted chalcones as bidentate ligands,
3
giving rise to a secondary tetrachelate with the corresponding change of conformation of the substrate molecule.
The possibility for chelation is determined by steric hindrances in the vicinity of the substrate coordination
centers and concurrent coordination of other electron-donor groups present in the substrate molecule.
Lanthanide shift reagents (LSR) have long been used
Complex formation of LSR with difunctional
in structural and conformational analysis of organic compounds is characterized by some specific features.
compounds, studies of their chirality, and interpretation Most frequently, coordination centers present in a sub-
of the NMR spectra. Creation of superconducting strate molecule operate independently from each other,
spectrometers made it possible to solve many problems and the induced shifts are integral quantities for all possible
without involving LSR. In the recent years, new fields of adducts. If coordination centers in a substrate molecule
application of LSR were found, e.g., enhancement of are spatially close, chelation with LSR is possible to afford
regioselectivity of organic reactions [1], analysis of ion tetrakis-adducts in which the coordination number of
ion interactions [2], and experimental determination of lanthanide increases to 8 [8]. In order to study this mode
the site of predominant charge localization in anions [3]. of coordination in more detail, we synthesized a series of
The effect of LSR on conformations of difunctional substituted 1-(2'-alkoxyphenyl)-3-phenyl-2-propenones
compounds was revealed recently [4]. Although this
property of LSR can complicate their use as
5
5
5
conformational probes, it may be helpful in modeling
interactions between small molecules and biological
macromolecules, where biological activity of a small
molecule originates from variation of its conformation
during association. Therefore, studies on the effect of
LSR on molecular conformations in solution seem to be
important.
$
%
D
5
5
5
2
5
, ;9,
x
1
IXVI, R = H, unless otherwise stated; I, R = OCH ,
3
3
7
1
3
5
1
R = Cl, R = F; II, R = OCH , R = R = Cl; III, R = OCH ,
Application of LSR is based on their ability to
selectively coordinate electron-donor functional groups
in the substrates and induce shifts of signals in the NMR
spectra; the magnitude of the lanthanide-induced shifts
depends on the structure of the LSRsubstrate adduct
and arrangement of magnetic nuclei in the substrate
molecule relative to the coordination center [5, 6]. The
structure of LSR adducts with monofunctional organic
molecules was extensively studied [7].
3
3
3
5
1
3
7
1
5
R = Br, R = Cl; IV, R = OC H , R = R = Cl; V, R = R =
2
5
3
1
3
6 7
OCH , R = Cl; VI, R = OCH , R = Cl, R R = OCH O;
3
3
7
2
1
1
3
6
VII, R = OCH , R = Cl, R R = OCH CH O; VIII, R =
3
2
1
2
2
4
7
2
4
R = OCH , R = CH , R = NO ; IX, R = R = R = OCH ,
3
3
2
3
7
1
2
4
6
1
6
R = Cl; X, R = R = R = OCH , R = NO ; XI, R = R =
3
2
7
3
1
3
6
7
R = OCH , R = F; XII, R = OCH(CH ) , R = F, R = R =
3
3 2
1
6
7
3
1
6
OCH ; XIII, R = R = R = OCH , R = Cl; XIV, R = R =
3
3
2
7
3
1
6
7
4
R = OCH , R = Br; XV, R = R = R = R = OCH , R =
3
3
1
3
6
7
CH ; XVI, R = OC H , R = Cl, R = R = OCH .
3
2
5
3
1070-4280/05/4101-0047Ó2005 Pleiades Publishing, Inc.
Turov
