Crystal X-ray diffraction guided NMR analysis of 3,9-diaryl-2,4,8,10- tetraoxaspiro[5.5]undecanes under differently shielding effect of terminal aromatic rings

Article abstract of DOI:10.1016/j.molstruc.2010.03.062

The stereoscopic structures of 3,9-di(o-, m-and p-chlorophenyl)-2,4,8,10- tetraoxaspiro[5.5]undecanes were elucidated via high-resolution 1D and 2D NMR techniques including ¹H NMR, ¹³C NMR, DEPT, ¹H-¹H COSY, HSQ

Full text of DOI:10.1016/j.molstruc.2010.03.062

Journal of Molecular Structure 973 (2010) 152–156
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Crystal X-ray diffraction guided NMR analysis of 3,9-diaryl-2,4,8,10-tetraoxaspi-
ro[5.5]undecanes under differently shielding effect of terminal aromatic rings
*
Xiaoqiang Sun , Shu-Ling Yu, Zheng-Yi Li, Yang Yang
Key Laboratory of Fine Petrochemical Engineering, Jiangsu Polytechnic University, Changzhou 213164, Jiangsu, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The stereoscopic structures of 3,9-di(o-, m- and p-chlorophenyl)-2,4,8,10-tetraoxaspiro[5.5]undecanes
were elucidated via high-resolution 1D and 2D NMR techniques including 1H NMR, 13C NMR, DEPT,
1H-1H COSY, HSQC, and HMBC. Complete and accurate assignment of 1H and 13C spectral data, especially
the discrimination of hydrogens and carbons in four methylenes under differently shielding effect of aro-
matic rings were achieved by NMR analysis guided by crystal X-ray diffraction.
Received 29 January 2010
Received in revised form 23 March 2010
Accepted 24 March 2010
Available online 27 March 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Spiro-1,3-dioxanes
Pentaerythritol diacetals
Stereoscopic structure
NMR
Crystal X-ray diffraction
Shielding effect
1. Introduction
shielding effect of terminal aromatic rings by 1D and 2D NMR
techniques and stereoscopic structure analysis guided by crystal
Owing to the characteristic axial and helical chirality, the ste-
reochemistry of spiranes with six-membered rings has been
extensively studied [1]. In the past three decades, most of these
investigations were carried out with spiranes containing 1,3-
dioxane units [1–15]. The chirality of the parent spiro[5.5]unde-
cane was first observed by Dodziuk [4,5] and confirmed by Grosu
[6,7]. NMR plays an important role in structural identification,
and 2D NMR technique as one of the most effective methods
for the determination of molecular spatial structure has been
widely used in stereochemistry [16–18]. Although several studies
on the stereochemistry of 3,9-disubstituted 2,4,8,10-tetraoxaspi-
ro[5.5]undecane derivatives based on NMR experiments have
been well established [2,5,12,13,15], most of them focused on
the effect of different substituents such as alkyl and phenyl on
position 3,9. Therefore, complete and accurate assignment of pro-
ton and carbon signals in four methylenes under the differently
shielding effect of terminal aromatic rings is also an interesting
challenge. Herein three examples including o-, m- and p-chloro-
phenyl substituted 2,4,8,10-tetraoxaspiro[5.5]undecanes 1–3
(Fig. 1) were investigated respectively to describe the stereo-
chemistry of pentaerythritol diacetals under the differently
X-ray diffraction.
2. Experimental
2.1. Reagents and samples
All reagents were of analytical grade unless otherwise
stated.
Three white compounds 1–3 were prepared by the following
method. To a solution of o-, m-, and p-chlorobenzaldehyde (5 mmol)
and pentaerythritol (3 mmol, 0.41 g) in toluene (25 mL), phospho-
tungstic acid (1 mol%, 16.5 mg) as catalyst was added, respectively.
The mixtures were refluxed for 6–8 h to complete the reaction. After
reaction, the mixtures were allowed to cool to the room tempera-
ture, and dichloromethane (25 mL) was added to dissolve the prod-
uct. The insoluble residues were filtrated out and the filtrate was
dried over Na2SO4. The crude products were isolated by removing
CH2Cl2 undervacuum to give a white solid in 72%, 63%, and 46% yield,
respectively. The pure samples of 1–3 for NMR experiments were
obtained by recrystallization using ethanol as the solvent.
2.2. NMR measurements
* Corresponding author. Address: School of Chemistry and Chemical Engineering,
Jiangsu Polytechnic University, Changzhou 213164, China. Tel.: +86 (519)
86330003; fax: +86 (519) 86330257.
All 1D (1H and 13C) and 2D NMR experiments were performed
on a Bruker AVANCE III-500 NMR spectrometer (500.13 MHz for
E-mail address: chemsxq@yahoo.com.cn (X. Sun).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.03.062

X. Sun et al. / Journal of Molecular Structure 973 (2010) 152–156
153
structure was solved by direct methods and refined by full matrix
least-squares methods on F2 using the SHELXS-97 [19] and SHEL-
XL-97 [20] programs. The positions of hydrogen atoms were calcu-
lated theoretically and included in the final cycles of refinement in
a riding model along with attached carbons. The final cycle of full
matrix least-squares refinement was based on 3447 independent
Fig. 1. Structure of 2,4,8,10-tetraoxaspiro[5.5]undecane derivatives 1–3.
reflections [I > 2r (I)] and 226 variable parameters with
R1 = 0.0377, wR2 = 0.1142. CCDC 752853 contains the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data Cen-
tre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk).
1H and 125.77 MHz for 13C) equipped with a 5 mm BBO probe. The
specimens were dissolved in 0.5 mL CDCl3, 1H NMR and 13C NMR
spectra were recorded on NMR spectrometer using TMS as an
internal reference. Chemical shifts (d) were reported in parts per
million (ppm), The pulse conditions were as follows: for the 1H
NMR spectrum, spectrometer frequency (SF) = 500.13 MHz, acqui-
sition time (AQ) = 1.638 s, number of scans (NS) = 2, number of
dummy scans (DS) = 0, relaxation delay (RD) = 1.0 s, 90° pulse
3. Results and discussion
3.1. Characterization of pentaerythritol diacetals 1–3 by 1D and 2D
NMR techniques
width (PW) = 12.56 ls, spectral width (SW) = 19.99 Hz, Fourier
transform (FT) size TD = 32 K; for the 13C NMR spectrum,
SF = 125.77 MHz, AQ = 1.10 s, NS = 2048, DS = 4, RD = 1.0 s, 90°
pulse width = 9.70 ls, SW = 236.64 Hz, line broadening (LB) =
1H spectra and the 13C spectra for compounds 1–3 were mea-
sured at room temperature and the results were summarized in
Tables 1–3, respectively. CDCl3 was used as solvent for three sam-
ples, which provided clear 1H and 13C NMR spectra for 1–3, and
most of their signals were resolved. This allowed us to observe
the chemical shifts and measure the coupling constants in most
cases. Most 13C signals could be assigned through HSQC. For qua-
ternary carbons, analysis of HMBC data was sufficient to complete
the assignment.
1.0 Hz, TD = 32 K; for the HSQC spectrum, AQ = 0.051 s, NS = 8,
DS = 16, RD = 1.5 s, SW = 19.99 (1H) and 236.64 (13C) Hz, FT
size = 1024 ꢀ 1024, and 135 Hz one-bond coupling constant; for
the HMBC spectrum, AQ = 0.205 s, NS = 8, DS = 16, RD = 1.5 s,
F1 = 29761.91 Hz, F2 = 5500 Hz, FT size = 2048 ꢀ 1024; for the
COSY spectrum, AQ = 0.15 s, NS = 4, DS = 4, RD = 1.49 s,
F1 = 6684.49 Hz, F2 = 6684.49 Hz, FT size = 1024 ꢀ 1024, experi-
ment was performed at 298 K.
3.2. Crystal structure of 3,9-di(o-chlorophenyl)-2,4,8,10-
2.3. X-ray crystallography
tetraoxaspiro[5.5]undecane 1
M = 381.23, C19H18Cl2O4, Orthorhombic, Space group P212121,
A high-quality single crystal of di(o-chlorophenyl)-2,4,8,10-tet-
raoxaspiro[5.5]undecane 1 with aS configuration suitable for X-ray
crystallography was hazardously picked up from the racemic mix-
tures of crystals in methanol solution without any chiral separa-
tion, which is like in the known experiment of Pasteur. As shown
in Fig. 2, the two six-member O-heterocycles both adopt chair con-
formation, and the aromatic rings located at the equatorial of posi-
tion 3 and 9, which is conformed to the reported similar crystal
structures [21,22]. A 2D-net structure packing along a and b axis
a = 7.0400(5) Å, b = 7.2389(6) Å, c = 34.674(3) Å,
a = b = c = 90°,
V = 1767.1(2) Å3, Z = 4, Dcalcd = 1.433 g/cm3. A colorless crystal of
dimension 0.21 ꢀ 0.21 ꢀ 0.16 mm for compound 1 was used for
measurement at 295 (2) K with the u- and
x
-scans mode on a Bru-
radia-
ker APEX-II diffractometer with CCD detector using Mo K
a
tion (k = 0.71073 Å). The data were corrected for Lorentz and
polarization effects and absorption corrections based on the
multi-scan method were performed using SADABS program. The
Table 1
1H and 13C NMR chemical shifts,
t
(ppm), multiplicities and coupling constants, J (H–H) (Hz), 1H–1H and 1H–13C correlations in HMBC, COSY and HSQC spectra for compound 1.
C
1
dC (ppm)
H
1
dH (ppm)
HMBC
COSY
HSQC
70.7 (t)
e 3.88 (2H, dd, J = 11.5 Hz, J = 2.5 Hz,)
a 3.75 (2H, d, J = 11.5 Hz)
C-3,5,6,7,11
Ha-1, He-5
He-1
Ha-1, He-1
3
5
99.4 (d)
71.3 (t)
3
5
5.84 (2H, s)
e 4.95 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.95 (2H, d, J = 11.5 Hz)
C-1,5,13,17
C-1,3,6,7,11
–
H-3
Ha-5, He-5
Ha-5, He-1
He-5
6
7
32.5 (s)
71.3 (t)
–
7
–
–
–
–
e 4.95 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.95 (2H, d, J = 11.5 Hz)
5.84 (2H, s)
e 3.88 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.75 (2H, d, J = 11.5 Hz)
–
–
7.35 (2H, d)
7.40 (2H, t)
7.34 (2H, m)
7.74 (2H, m)
–
C-1,5,6,9,11
Ha-7, He-11
He-7
–
Ha-11, He-7
He-11
–
–
H-15
H-14,16
H-15,17
H-16
Ha-7, He-7
9
11
99.4 (d)
70.7 (t)
9
11
C-7,11,130,170
C-1,5,6,7,9
H-9
Ha-11, He-11
12
13
14
15
16
17
120
130
140
150
160
170
132.6 (s)
135.2 (s)
130.3 (d)
129.5 (d)
127.0 (d)
127.7 (d)
132.6 (s)
135.2 (s)
130.3 (d)
129.5 (t)
127.0 (t)
127.7 (d)
–
–
–
–
–
–
14
15
16
17
–
C-12,13,15,16
C-13,14,16,17
C-12,14,15,17
C-3,12,13,16
–
H-14
H-15
H-16
H-17
–
–
–
–
–
–
–
140
150
160
170
7.35 (2H, d)
7.40 (2H, t)
7.34 (2H, m)
7.74 (2H, m)
C-120,130,150,160
C-130,140,160,170
C-120,140,150,170
C-9,120,130,150
H-150
H-140,160
H-150,170
H-160
H-140
H-150
H-160
H-170

154
X. Sun et al. / Journal of Molecular Structure 973 (2010) 152–156
Table 2
1H and 13C NMR chemical shifts,
t
(ppm), multiplicities and coupling constants, J (H–H) (Hz), 1H–1H and 1H–13C correlations in HMBC, COSY and HSQC spectra for compound 2.
C
1
dC (ppm)
H
1
dH (ppm)
HMBC
COSY
HSQC
70.7 (t)
e 3.83 (2H, d, J = 11.65 Hz)
a 3.65 (2H, d, J = 11.65 Hz)
5.43 (2H, s)
e 4.83 (2H, d, J = 11.65 Hz)
a 3.84 (2H, d, J = 11.65 Hz)
–
e 4.83 (2H, d, J = 11.65 Hz)
a 3.84 (2H, d, J = 11.65 Hz)
5.43 (2H, s)
e 3.83 (2H, d, J = 11.65 Hz)
a 3.65 (2H, d, J = 11.65 Hz)
–
7.50 (4H, d)
–
7.31 (2H, m)
7.33 (2H, m)
7.36 (2H, d)
–
7.50 (2H, s)
–
C-3,5,6,7,11
Ha-1, He-5
He-1
–
Ha-5, He-1
He-5
–
Ha-7, He-11
He-7
–
Ha-11, He-7
He-11
–
H-14
–
H-16
H-15,17
H-16
–
H-140
–
H-160
H-150,170
H-160
Ha-1, He-1
3
5
99.4 (d)
71.3 (t)
3
5
C-1,5,13,17
C-1,3,6,-7,11
H-3
Ha-5, He-5
6
7
32.5 (s)
71.3 (t)
–
7
–
–
C-1,5,6,9,11
Ha-7, He-7
9
11
99.4 (d)
70.7 (t)
9
11
C-7,11,130,170
C-1,5,6,7,9
H-9
H-11
12
13
14
15
16
17
120
130
140
150
160
170
132.6 (s)
135.2 (s)
130.3 (d)
129.5 (d)
127.0 (d)
127.7 (d)
132.6 (s)
135.2 (s)
130.3 (d)
129.5 (t)
127.0 (t)
127.7 (d)
–
13
–
15
16
17
–
130
–
150
160
170
–
–
H-13
–
H-15
H-16
H-17
–
H-130
–
H-150
H-160
H-170
C-3,12,14,17
–
C-13,14,16,17
C-12,14,15,17
C-3,12,13,16
–
C-9,120,140,170
–
C-130,140,160,170
C-120,140,150,170
C-9,120,130,150
7.31 (2H, m)
7.33 (2H, d)
7.36 (2H, d)
Table 3
1H and 13C NMR chemical shifts,
t
(ppm), multiplicities and coupling constants, J (H–H) (Hz), 1H–1H and 1H–13C correlations in HMBC, COSY and HSQC spectra for compound 3.
C
1
dC (ppm)
H
1
dH (ppm)
HMBC
COSY
HSQC
70.5 (t)
e 3.82 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.65 (2H, d, J = 11.5 Hz)
5.43 (2H, s)
e 4.82 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.83 (2H, d, J = 11.5 Hz)
–
e 4.82 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.83 (2H, d, J = 11.5 Hz)
5.4 3 (2H, s)
e 3.82 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)
a 3.65 (2H, d, J = 11.5 Hz)
–
7.42 (4H, d, J = 8.5 Hz)
7.35 (4H, d, J = 8.5 Hz)
–
7.35 (4H, d, J = 8.5 Hz)
7.42 (4H, d, J = 8.5 Hz)
–
7.42 (4H, d, J = 8.5 Hz)
7.35 (4H, d, J = 8.5 Hz)
–
7.35 (4H, d, J = 8.5 Hz)
7.42 (4H, d, J = 8.5 Hz)
C-3,5,6,7,11
Ha-1, He-5
He-1
–
Ha-1, He-1
3
5
101.5 (d)
71.0 (t)
3
5
C-1,5,13,17
C-1,3,6,7,11
H-3
Ha-5, He-5
Ha-5, He-1
He-5
–
Ha-7, He-11
He-7
–
Ha-11, He-7
He-11
–
H-14
H-13
–
6
7
32.5 (s)
71.0 (t)
–
7
–
–
C-1,5,6,9,11
Ha-7, He-7
9
11
101.5 (d)
70.5 (t)
9
11
C-7,11,130,170
C-1,5,6,7,9
H-9
Ha-11, He-11
12
13
14
15
16
17
120
130
140
150
160
170
134.9 (s)
127.5 (d)
128.5 (d)
136.4 (s)
128.5 (d)
127.5 (d)
134.9 (s)
127.5 (d)
128.5 (d)
136.4 (s)
128.5 (d)
127.5 (d)
–
–
–
13
14
–
16
17
–
130
140
–
160
170
C-3,12,14,17
C-12,13,15,16
–
C-12,14,15,17
C-3,12,13,16
–
C-9,120,140,170
C-120,130,150,160
–
H-13
H-14
–
H-17
H-16
–
H-16
H-17
–
H-140
H-130
–
H-130
H-14
–
C-12,14,15,17
C-9,120,130,150
H-170
H-160
H-160
H-170
was constructed by intermolecular weak interaction including
Clꢁ ꢁ ꢁHAr and CHꢁ ꢁ ꢁ , respectively (Fig. 3).
3.95 ppm) are in lower field than H-1(11) (3.88 ppm and
3.75 ppm). Secondly, for positions 5(7), the equatorial protons
(He) are closer to different ring oxygens than the axial ones (Ha),
so the former is more deshielded than the latter [He-5(7) vs Ha-
5(7), 4.95 ppm vs 3.95 ppm]. In the case of 1(11), the signal of
He-1(11) (3.88 ppm) are in lower field than that of Ha-1(11)
(3.75 ppm) result from the anisotropic effects of single bonds in
the six-member heterocycles [12,17]. Finally, the equatorial pro-
tons [He-5(7) and He-1(11)] on the same plan can further split to
form the double-double peaks [4.95 (2H, dd, J = 11.5 Hz,
J = 2.5 Hz) and 3.88 (2H, dd, J = 11.5 Hz, J = 2.5 Hz)] due to coupling
of the two terminal protons on W disposal involving four bonds
[18,23]. Moreover, all the 1H NMR signal assignments of methyl-
enes of compound 1 were in agreement with the corresponding
data of 13C NMR, DEPT, 1H-1H COSY, HSQC, and HMBC (Table 1).
p
3.3. Crystal X-ray diffraction guided assignment of protons in four
methylenes of 3,9-di(o-chlorophenyl)-2,4,8,10-
tetraoxaspiro[5.5]undecane 1 in 1H NMR spectrum
Use 1 as a model compound to determine the 1H NMR signals
for the four methylenes. As depicted in Fig. 2 and partial 1H NMR
spectrum of compounds 1 in Fig. 4, firstly, the H-5(7) in ‘‘methy-
lene inside” oriented toward the other 1,3-dioxane ring are more
deshielded than H-1(11) in ‘‘methylene outside” oriented in oppo-
site direction as a result of the influence of the van der Waals Radii
site effect induced by oxygen atoms of the different six-member
heterocycles [5], so the signals of H-5(7) (4.95 ppm and

X. Sun et al. / Journal of Molecular Structure 973 (2010) 152–156
155
Fig. 2. Crystal structure of compound 1.
Fig. 3. The molecular packing along a and b axis in the crystal structure of 1 (dashed lines indicate Clꢁ ꢁ ꢁHAr (green) and CHꢁ ꢁ ꢁ
p
(blue) weak interactions). (For interpretation
of the references to colour in this figure legend, the reader is referred to the web version of this article.)
3.4. Crystal structure guided NMR analysis for compounds 1–3 under
differently shielding effect of terminal aromatic rings
It conducted that the H-3(9) signal in compound 1 shifted
0.41 ppm toward low field comparing with that in the com-
pounds 2 and 3. Secondly, owing to the differently shielding ef-
fects of aromatic rings, four methylenes proton signals in
compound 1 shifted about 0.1 ppm toward low field and the cor-
responding carbon signals also gave rise to downfield shifts
(Tables 1–3) than those of compounds 2 and 3. Moreover, in com-
pounds 2 and 3, four groups of peaks of methylenes were not
completely separated, the signals of Ha-5(7) and He-1(11) par-
tially overlapped, and their chemical shifts moved toward high
field contrasting to compound 1. These phenomena indicated that
the terminal aromatic rings could significantly affect the chemical
shifts and split pattern of hydrogens and carbons in six-member
heterocycles of 3,9-diaryl-2,4,8,10-tetraoxaspiro[5.5] undecanes.
Although the effect of different brominated alkyl [13], alkyl and
phenyl [12] on position 3,9 of 2,4,8,10-tetraoxaspiro[5.5]unde-
canes have been described by Grosu, it is the first time that the
influence of aryl bearing different steric and electronic effect
was discussed here.
With the unambiguous NMR signal assignment for compound
1 in hand, different substrates 2 and 3 were further probed to
illustrate the influence on NMR induced by differently shielding
effect of terminal aromatic rings. As shown in Fig. 4, despite of
unique discrimination among the three isomers 1–3 caused by
different positions of the chlorine atoms on the aromatic rings,
obviously different signals including the chemical shifts and split
pattern of protons in two six-member heterocycles were ob-
served. The signals of H-5(7), H-1(11) and H-3(9) were similar
in compounds 2 and 3, while those of the compound 1 gave great
difference. It might be attributed to the different steric structure
and electronic effect of aryl resulted from chlorine atom located
at different positions on benzene rings. Firstly, there are weak
interactions between H-3(9) and Cl1(2) in compound 1 (distance
of CHꢁ ꢁ ꢁCl, 2.589 Å and 2.552 Å, Fig. 2) while none in compounds
2 and 3 because of the long distance between H-3(9) and Cl1(2).

156
X. Sun et al. / Journal of Molecular Structure 973 (2010) 152–156
Fig. 4. The partial 1H NMR spectra of compounds 1–3.
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We have completely and accurately assigned all the proton and
carbon signals for 3,9-di(o-, m- and p-chlorophenyl)-2,4,8,10-tetra-
oxaspiro[5.5]undecanes 1–3 by using 1D and 2D NMR techniques
including 1H, 13C NMR, DEPT135, 1H-1H COSY, HSQC, and HMBC
experiments. The NMR analysis guided by crystal X-ray diffraction
disclosed that despite of the same environment of the two six-
member rings, the chemical environment of two methylenes exist-
ing in the same ring and the two protons in the same methylene
were both different because of the molecular axial chirality. Fur-
thermore, the chemical shifts and split pattern of hydrogens and
carbons in two six-member heterocycles could be influenced by
the location of substituent on the terminal aromatic rings. This
study has provided significant proofs for the identification of the
similar structures as pentaerythritol diacetals bearing spiro-1,3-
dioxanes skeleton.
Acknowledgement
We gratefully acknowledge financial support from the Natural
Science Foundation of China (No. 20872051).
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University of Göttingen, Göttingen, 1997.
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