Synthesis and structure of new crown ethers with 1,4-phenylene and 1,4-naphthylene units

Article abstract of DOI:10.1016/j.molstruc.2011.01.052

The synthesis of monomers and dimers of some new crown ether type macrocycles with 1,4-phenylene and 1,4-naphthylene units are reported. The structural investigations of the compounds were carried out by NMR spectra, MS measurements and the single crystal X-ray solid state molecular structure of one compound.

Full text of DOI:10.1016/j.molstruc.2011.01.052

Journal of Molecular Structure 996 (2011) 17–23
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and structure of new crown ethers with 1,4-phenylene
and 1,4-naphthylene units
⇑
Monica Cîrcu, Anca Petran, Andrei Serban Gâz, Elena Bogdan , Anamaria Terec, Ciprian I. Raßt,
⇑
Richard A. Varga, Ion Grosu
‘‘Babes-Bolyai’’ University, Organic Chemistry Department and CCSOOM, Cluj-Napoca, 11 Arany Janos Str., 400028 Cluj-Napoca, Romania
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of monomers and dimers of some new crown ether type macrocycles with 1,4-phenylene
and 1,4-naphthylene units are reported. The structural investigations of the compounds were carried out
by NMR spectra, MS measurements and the single crystal X-ray solid state molecular structure of one
compound.
Received 13 November 2010
Received in revised form 24 January 2011
Accepted 24 January 2011
Available online 31 January 2011
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Macrocycles
Crown ethers
Podands
X-ray structure
NMR
1. Introduction
The unsubstituted ortho,ortho’-dibenzocrown ethers are well
known and they are commercially available [1,6] Their meta, meta’
The synthesis and the structural investigations of crown ether
type macrocycles became an important target in organic chemistry
after the first work reported in this area by Pedersen in 1967 [1].
Crown ether type macrocycles are successfully used in the con-
struction of sensors, as hosts for the chemoselective recognition
of different guests [2], they can ensure the solubility of salts [3]
or they can increase the activity of catalysts [4].
A further application of crown ether type macrocycles should be
connected to their deposition on different surfaces (e.g. gold 1.1.1)
in order to obtain materials which are sensitive to different guest
species (e.g. alkali cations). For this purpose the target macrocycles
has to exhibit appropriate substituents which can themselves (or
after transformations) interact with the surface and can facilitate
the deposition of the macrocycles. Another feature concerning
the structure of these target macrocycles is correlated to the pres-
ence of groups which can insure the organization of the macrocy-
cles on the surface. Extended aromatic groups (e.g. naphthalene or
or para, para’ isomers were already obtained [7] but they are not so
widely used as the classic dibenzo crown ethers. Crown ethers
with 1,4-naphthylene or substituted phenylene units are not com-
mon. We focused in this work on the synthesis of crown ether type
macrocycles (I, Chart 1) exhibiting 2,3-dimethyl-1,4-phenylene
and 1,4-naphthylene units. In our opinion the 1,4-phenylene unit
could be functionalized in order to facilitate the deposition of the
macrocycles on different surfaces, while the 1,4-naphthylene units
could insure the self organization of the macrocycles and thus, the
target compounds could be important intermediates for the access
to macrocycles based organized monolayers.
2. Experimental
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were re-
corded at rt in CDCl3 on a Bruker 300 MHz spectrometer, using
the solvent line as reference.
anthracene units), via
p–p stacking, are important candidates for
The crystal of 14b was studied on a Bruker AXS X8-APEX II dif-
the obtaining of organized (self-assembled) monolayers (SAM’s)
[5].
fractometer with graphite monochromatized Mo K
a radiation.
Data were collected at room temperature (297 K). The structure
was refined with anisotropic thermal parameters. The hydrogen
atoms were refined with a riding model and a mutual isotropic
thermal parameter. For structure solving and refinement the soft-
ware package SHELX-97 was used [8,9] The drawings were created
with Ortep [10] and Diamond programs [11]. The structural data
⇑
Corresponding authors.
E-mail addresses: ebogdan@chem.ubbcluj.ro (E. Bogdan), igrosu@chem.ubbcluj.
ro (I. Grosu).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.01.052

18
M. Cîrcu et al. / Journal of Molecular Structure 996 (2011) 17–23
Scheme 4. Synthesis of dimer macrocycle 14b.
Chart 1. Model of target macrocycles (the chains contain polyethyleneglycol units
of various lengths).
The geometries of the cations of complex 7a(Cs+) were opti-
mized at density functional theory level using B3LYP functional
as implemented in GAMESS 2010 R2 software package [12,13].
For all atoms the LANL2DZ basis set was used as published on
EMSL database [14–18]. Frequency calculations confirmed that
the optimized geometries are energy minima (no negative fre-
quencies were obtained).
2.1. Procedure for the synthesis of 1
Sodium hydroxide (1.6 g, 40 mmol) was solved in a mixture of
ethanol (20 ml) and water (5 ml) and added to the ethanolic solu-
tion of 2,3-dimethylbenzene-1,4-diol (1.38 g, 10 mmol, 20 ml eth-
anol) forming a dark red solution that was allowed to stir for
30 min. 2-Chloroethanol (3.22 g, 30 mmol) was then added under
stirring and the obtained solution was refluxed for 1 day, and the
formation of a precipitate was observed. After cooling to room
temperature, the solvent was removed in vacuo affording a red so-
lid that was dissolved in EtOAc (100 ml) and washed with water
(2 ꢀ 75 ml). The aqueous phase was further extracted with EtOAc
(2 ꢀ 75 ml). The combined organic phases were washed with brine
(50 ml), dried over MgSO4 and the solvent was evaporated in va-
cuo. Purification of the residue by column chromatography
(EtOAc/petroleum ether 1:1; Rf = 0.42) gave 1 as a off-white pow-
der (1.7 g, 7.5 mmol, yield 76%). 2,3-Dimethyl-1,4-bis(10,40-diox-
abutane-10-yl)-benzene 1. White solid (1.7 g, 76%, 7.5 mmol,
m.p. = 117–119 °C). 1H NMR d = 1.92 (s, 2H, OH), 2.18 (s, 6H,
CH3), 3.95 (m, 4H, H-30), 4.02 (m, 4H, H-20), 6.67 ppm (s, 2H, H-5,
Scheme 1. Synthesis of macrocycles 5b, 6a and 7a.
Scheme 2. Synthesis of podands 1–3.
13
H-6). C NMR d = 12.2 (CH3), 61.8 (C-30), 70.4 (C-20), 109.9 (C-5,
C-6), 127.3 ppm (C-2, C-3), 151.2 (C-1, C-4). MS (ESI) m/z (rel.
int.%) 249 [M + Na]+ (100). Anal. Calcd for C12H18O4 (226.27): C,
67.30; H, 8.02; found: C, 67.49; H, 7.89.
was deposited at the Cambridge Crystallographic Data Center,
deposition number is CCDC 799290 (14b).
Electrospray ionization mass spectra ESI (ESI+) were recorded
using an Esquire 3000 ion-trap mass spectrometer (Bruker Dalton-
ic GmbH, Bremen, Germany) equipped with a standard ESI/APCI
source.
2.2. Procedure for the synthesis of 2
Melting points were measured with a Kleinfeld melting point
apparatus and are uncorrected. Thin layer chromatography (TLC)
was conducted on silica gel 60 F254 TLC plates purchased from
Merck. Preparative column chromatography was performed using
A solution of 2,3-dimethylbenzene-1,4-diol (1.38 g, 10 mmol) in
dry DMF (50 ml) was added over 30 min to a stirred suspension of
K2CO3 (8.28 g, 60 mmol) in dry DMF (75 ml) under argon. After an
additional 30 min, a solution of 5-chloro-3-oxa-1-pentanol (3.74 g,
30 mmol) in dry DMF (30 ml) was added over 30 min, and the tem-
perature was raised to 80 °C. Stirring and heating were continued
for 2 days. After cooling to room temperature, the reaction mixture
was filtered and the solid residue was washed with DMF (20 ml).
PharmPrep 60 CC (40–63 lm) silica gel purchased from Merck.
Solvents were dried and distilled under argon using standard
procedures before use. Chemicals of commercial grade were used
without further purification.
Scheme 3. Synthesis of ditosylated podand 13 and macrocycle 14b.

M. Cîrcu et al. / Journal of Molecular Structure 996 (2011) 17–23
19
Fig. 1. X-ray diffraction investigations of compound 14b: (a) Ortep diagram, (b) View of the zig-zag disposition of the neighboring molecules in sheets, with a dihedral angle
of 60°, (c) View of the lattice along b crystallographic axis.

20
M. Cîrcu et al. / Journal of Molecular Structure 996 (2011) 17–23
Fig. 2. 1H NMR spectrum (CDCl3, fragment) of compound 7a.
The solvent was removed in vacuo and the residue was partitioned
between CH2Cl2 (150 ml) and a saturated solution of NaCl (70 ml).
The pH was adjusted to 5 with 2 N HCl. The organic phase was sep-
arated and the aqueous phase was washed with CH2Cl2
(2 ꢀ 50 ml). The combined organic solutions were washed with
H2O (80 ml), dried (MgSO4), and concentrated in vacuo affording
2 as a yellow oil (1.31 g, 4.17 mmol, 42%).
(150 ml), was washed with 2 N HCl (30 ml) and H2O (2 ꢀ 50 ml).
The organic phase was dried (MgSO4), filtered and the solvent
was evaporated in vacuo. Purification of the residue by column
chromatography (EtOAc; Rf = 0.27) gave 3 as a yellow oil (1.87 g,
4.65 mmol, 46%).
2,3-Dimethyl-1,4-bis(10,40,70,100-tetraoxadecane-10-yl)-benzene
3. Yellow oil (1.87 g, 46%, 4.65 mmol).1H NMR d = 2.15 (s, 6H, CH3),
3.59–4.07 (m, 24H, H-20, H-3,0 H-50, H-60, H-80, H-90), 6.64 ppm (s,
2H, H-5, H-6); 13C NMR d = 12.2 (CH3), 61.6, 68.7, 70.0, 70.8, 72.5
(C-10, C-20, C-40, C-50, C-70, C-80), 110.0 (C-5, C-6), 127.2 (C-2, C-3),
151.2 ppm (C-1, C-4). MS (ESI) m/z (rel. int.%) 425 [M + Na]+
(100). Anal. Calcd for C20H34O8 (402.48): C, 59.68; H, 8.51; found:
C, 59.36; H, 8.71.
2,3-Dimethyl-1,4-bis(10,40,70-trioxaheptane-10-yl)-benzene
2.
White solid (1.31 g, 42%, 4.17 mmol). 1H NMR d = 1.92 (s, 2H,
OH), 2.17 (s, 6H, CH3), 3.68 (m, 4H, H-60), 3.76 (m, 4H, H-50), 3.86
(m, 4H, H-30), 4.07 (m, 4H, H-20), 6.67 ppm (s, 2H, H-5, H-6); 13C
NMR d = 12.2 (CH3), 61.7 (C-50), 68.8 (C-20), 69.9 (C-30), 72.5 (C-
60), 110.0 (C-5, C-6), 127.4 (C-2, C-3), 151.3 ppm (C-1, C-4). MS
(ESI) m/z (rel. int.%) 337 [M + Na]+ (100). Anal. Calcd for C16H26O6
(314.37): C, 61.13; H, 8.34; found: C, 61.37; H, 8.59.
2.4. General procedure for the synthesis of macrocycles 5b, 6a and 7a
2.3. Procedure for the synthesis of 3
A solution of 1, 2 or 3 (1 mmol) in dry THF (20 ml) was added to
a suspension of NaH (powder 97%, 3 mmol) in dry THF (250 ml)
and the mixture was refluxed for 3 h. Then a solution of 1,4-dibro-
momethylnaphthalene (1 mmol) in dry THF (120 ml) was added
dropwise to the refluxing suspension over 60 h. The reddish mix-
ture was refluxed for another 48 h. After removal of the solvent,
H2O (50 ml) was added and the mixture was extracted with CHCl3
(4 ꢀ 50 ml). The combined organic phases were dried over anhy-
drous MgSO4, and the solvent was removed under reduced pres-
sure. The crude product was purified by column chromatography
(EtOAc/petroleum ether = 1.5:1) to afford the desired compound.
A solution of 2,3-dimethylbenzene-1,4-diol (1.38 g, 10 mmol) in
dry t-butyl alcohol (50 ml) was added to a solution of potassium t-
butoxide (2.8 g, 25 mmol) in dry t-butyl alcohol (40 ml) under ar-
gon. The mixture was refluxed for 4 h, then 8-chloro-3,6-dioxa-1-
octanol (4.22 g, 25 mmol) was added over 30 min and the reflux
was continued for 24 h. After cooling to room temperature, the
reaction mixture was filtered and the solid residue washed with
CH2Cl2 (3 ꢀ 50 ml). The combined organic solutions were
evaporated in vacuo, and the residue was solved in CH2Cl2

M. Cîrcu et al. / Journal of Molecular Structure 996 (2011) 17–23
21
J = 6.6, 3.3 Hz, 2H, H-25, H-26), 8.05 ppm (dd, J = 6.6, 3.3 Hz, 2H,
H-24, H-27). 13C NMR d = 11.7 (CH3), 69.5, 70.3, 70.4, 71.3, 71.6
(C-2, C-4, C-5, C-7, C-8, C-15, C-16, C-18, C-19, C-21), 111.1 (C-
29, C-30), 124.2 (C-31, C-32), 125.1 (C-24, C-27), 125.8 (C-25, C-
26), 127.1 (C-11, C-12), 131.5 (C-23, C-28), 133.7 (C-1, C-22),
151.6 ppm (C-10, C-13). MS (ESI) m/z (rel. int.%) 489.3 [M + Na]+
(100), 505.3 [M + K]+ (40). Anal. Calcd for C28H34O6 (466.57): C,
72.08; H, 7.35; found: C, 72.41; H, 7.19.
14,15-Dimethyl-3,6,9,12,17,20,23,26-octaoxatetracyclo[26,6,21,28
,
213,16,029,34]octatricosan-1(38),13,15,28(37),29(34),30,32,35-octaene
7a. Yellowish oil (0.15 g, 28%, 0.28 mmol). 1H NMR d = 2.03 (s, 6H,
CH3), 3.69 (m, 16 H, H-4, H-5, H-7, H-8, H-21, H-22, H-24, H-25),
3.81 (m, 4H, H-10, H-19), 3.99 (m, 4H, H-11, H-18), 4.95 (s, 4H, H-
2, H-27), 6.52 (s, 2H, H-35, H-36), 7.33 (s, 2H, H-37, H-38), 7.41
(dd, J = 6.6, 3.3 Hz, 2H, H-31, H-32), 8.10 ppm (dd, J = 6.6, 3.3 Hz,
2H, H-30, H-33). 13C NMR d = 12.19 (CH3), 68.94 (C-11, C-18), 69.49
(C-10, C-19), 69.94, 70.84, 70.93, 71.05 (C-4, C-5, C-7. C-8, C-21, C-
22, C-24, C-25), 71.68 (C-2, C-27), 110.00 (C-35, C-36), 124.50 (C-
37, C-38), 125.72 (C-30, C-33), 125.82 (C-31, C-32), 127.25 (C-14,
C-15), 131.89 (C-29, C-34), 134.03 (C-1, C-28), 151.20 ppm (C-13,
C-16). MS (ESI) m/z (rel. int.%) 555.3 [M + H]+(100). Anal. Calcd for
C32H42O8 (554.67): C, 69.29; H, 7.63; found: C, 69.12; H, 7.37.
2.5. Procedure for the synthesis of 14b
To the mixture of 1.45 mmol of 2,3-dimethyl-hydroquinone (8)
and 11 mmol of Cs2CO3 solved in 350 ml dry acetonitrile, a solution
of triethyleneglycoleditosylate (4.35 mmol) in 10 ml acetonitrile
was added dropwise with a push-syringe, under argon, over 4 days.
After 10 days reflux at 80°C the reaction was worked up by filtering
the salt and evaporating the solvent. Acetonitrile was distilled at
reduce pressure and the crude product was solubilized in 100 ml
water and extracted with dichloromethane (3 x 25 ml). The organic
layer was dried (MgSO4) and purified on chromatographic column
using hexane: ethyl acetate = 2:1 as eluent (yields 30%; Rf = 0.20).
The same experimental procedure using ditosylated 13
(0.28 mmol), 2,3-dimethylhydroquinone 8 (0.25 mmol), Cs2CO3
(1.28 mmol) and dry acetonitril (350 ml) gave macrocycle 14b in
22% yields.
13,14,27,28-Tetramethyl-2,5,8,11,16,19,22,25-octaoxa-triciclo
[24,2212,15]dotricontan-1(28),12,14,27,29,31-hexaene 14b. White
crystals (0.22 g, 30%, 0.43 mmol; m.p. = 135–136 °C). 1H NMR
d = 2.06 (s, 12H, CH3), 3.75 (s, 8H, H-6, H-7, H-20, H-21), 3.84 (m,
8H), 3.96 (m, 8H), 6.50 ppm (s, 4H, aromatic protons), 13C NMR
d = 12.16 (CH3), 68.83, 70.15, 71.21 (C-3, C-4, C-6, C-7, C-9, C-10,
C-17, C-18, C-20, C-21, C-23, C-24), 110.07 (C-29, C-30, C-31, C-
32), 127.09 (C-13, C-14, C-27, C-28), 151.35 ppm (C-1, C-C-12, C-
15, C-26). MS (ESI) m/z (rel. int.%) m/z 505.28 (100%). [M + H]+Anal.
Calcd for C28H40O8 (504.61): C, 66.65; H, 7.99; found: C, 66.42; H,
8.14.
Fig. 3. Optimized geometries [models A (a) and B (b)] of the complex 7a(Cs+).
Hydrogen atoms were omitted for clarity.
8,9-Dimethyl-3,6,11,14-tetraoxatetracyclo[14,6,21,16,27,10,017,22
]
hexacosane-1(26),7,9,16(25), 17(22),18,20,23-octaene 5b. White
solid (0.08 g, 21%, 0.21 mmol, m.p. = 168 °C). 1H NMR: d = 2.03 (s,
12H, CH3), 3.86 (t, J = 4.4 Hz, 8H, H-4, H-13, H-26, H-35), 4.05 (t,
J = 4.4 Hz, 8H, H-5, H-12, H-27, H-34), 5.06 (s, 8H, H-2, H-15, H-
24, H-37), 6.51 (s, 4H, H-45, H-46, H-47, H-48), 7.48 (s, 4H, H-49,
H-50, H-51, H-52), 7.49 (m, 4H, H-19, H-20, H-41, H-42),
8.12 ppm (m, 4H, H-18, H-21, H-40, H-43). 13C NMR: d 12.22
(CH3), 68.72, 68.86, 71.48 (C-2, C-4, C-5, C-12, C-13, C-15, C-24,
C-26, C-27, C-34, C-35, C-37), 109.49 (C-45, C-46, C-47, C-48),
124.46 (C-49, C-50, C-51, C-52), 125.47 (C-18, C-21, C-40, C-43),
125.96 (C-19, C-20, C-41, C-42), 127.15 (C-8, C-9, C-30, C-31),
131.79 (C-17, C-22, C-39, C-44), 133.99 (C-1, C-16, C-23, C-38),
151.19 ppm (C-7, C-10, C-29, C-32). MS (ESI) m/z (rel
int.%) = 379.3 [M + H]+ (100). Anal. Calcd for C24H26O4 (378.46): C,
76.17; H, 6.92; found: C, 75.88; H, 7.11.
3. Results and discussion
New crown ether type macrocycles 5–7 with 2,3-dimethyl-
1,4-phenylene and 1,4-naphthylene units, monomers 6a and 7a
(m = 1) and the dimer 5b (m = 2), were obtained in fair yields
(21–28%) by the usual procedure for the synthesis of macrocy-
cles starting from diols and dibrominated compounds [19]
(Scheme 1). The macrocycles were separated from the raw prod-
uct by column chromatography. The formation of dimers 6b and
7b was not observed (ESI-MS investigations of the corresponding
raw products).
11,12-Dimethyl-3,6,9,14,17,20-hexaoxatetracyclo[20,6,21,22
,
210,13,023,28]dotricosan-1(32),10, 12,22(31),23(28),24,26,29-octae-
ne 6a. White solid (0.11 g, 24%, 0.24 mmol, m.p. = 120–121 °C).
1H NMR d = 2.12 (s, 6H, CH3), 3.66 (m, 8 H), 3.86 (t, J = 4.5 Hz, 4H,
H-7, H-16), 4.02 (t, J = 4.5 Hz, 4H, H-8, H-15), 4.99 (s, 4H, H-2, H-
21), 6.58 (s, 2H, H-29, H-30), 7.41 (s, 2H, H-31, H-32), 7.45 (dd,
Podands 1–3 were obtained in good yields (42–76%) using
hydroquinone 8 and chloropolyethylene glycols 9–11. Procedures
adapted from similar syntheses reported in the literature [20] were

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M. Cîrcu et al. / Journal of Molecular Structure 996 (2011) 17–23
applied (Scheme 2). The synthesis of 1 was carried out in ethanol
using NaH as base, while 2 was obtained in DMF and the synthesis
of 3 was performed in t-butanol using K2CO3 instead of NaH.
In the synthesis of 3 starting from diphenol 8 and ditosylated
triethyleneglycol 12, besides ditosylated derivative 13, the dimer
macrocycle 14b was also obtained in a significant amount.
The yields in macrocycle 14b (30%) and in ditosylated derivative
13 (49%) were good and compounds 13 and 14b could be separated
by column chromatography (Scheme 3).
model B (3.203, 3.209, 3.279 Å) than in model A (3.136, 3.175,
3.222 Å). In both structures there are contacts shorter than 4.0 Å
between the centroids of the aromatic groups and the cesium ion
(A: 3.777, 3.800 Å; B: 3.721, 3.916 Å).
In gas phase the energy found for the model B is 2.83 kcal/mol
lower than that found for model A.
Podands 1–3 and 13 were investigated by NMR and mass spec-
trometry and the data are shown in the experimental part.
The synthesis of new macrocycle 14b was also performed start-
ing from 8 and 13 using the high dilution procedure, but the yields
in macrocyclic compound could not be improved (22%; Scheme 4).
The structure of 14b could be investigated by the solid state
molecular structure obtained by single crystal X-ray diffractometry
(Fig. 1a). The ORTEP diagram shows the almost planar structure of
the compound; the angle between the two aromatic rings is
4. Conclusions
New macrocycles with cavities of different sizes exhibiting 1,4-
phenylene and 1,4-naphthylene units were obtained in fair yields
by the reaction of several ditosylated diols exhibiting polyethyl-
eneglycol type chains of different lengths with 1,4-dibromomethy-
le-naphthalene. The structure of the macrocycles was investigated
by NMR spectra, ESI-MS and X-ray diffractometry. In the case of
the macrocycle with two 1,4-phenylene units the solid state
molecular structure investigation revealed the almost planar struc-
a
= 0.00°, the distance between the two planes described by the
aromatic units is d = 0.849 Å and the distance between the cen-
troids of the two aromatic units is d0 = 6.430 Å. In the lattice the
molecules exhibit a zig-zag arrangement (Fig. 1b) and the angle be-
tween two neighboring macrocycles is of 60°. The view of the lat-
tice along the b axis reveals the formations of columns (Fig. 1c).
The arrangement of the molecules in the lattice is insured by C–
ture of the compound and C–H——p interactions between the mol-
ecules in the lattice. The ESI-MS investigations of the largest
monomeric macrocycle showed the preference for the complexa-
tion of Cs+, the largest alkali cation.
H——p (aromatic) interactions between the hydrogen atoms of
the methyl group of a molecule and the centroids of the aromatic
rings of the neighboring macrocycles (d⁄—H = 2.743 Å; Fig. 1b).
The structural investigations in solution revealed only a small
number of signals in the NMR spectra of 5b, 6a, 7a and 14b proving
the symmetry of the structures and the flexibility of the chains.
Thus, the 1H NMR spectrum of 14b exhibits singlets for the aro-
matic protons, the protons of the central ethyleneoxide groups
and the methyl groups (d = 6.50; 7.75; 2.06 ppm), while for the
protons of the rest of ethyleneoxide groups there are two multi-
plets at 3.96 and 3.84 ppm, respectively.
Acknowledgment
This work was supported by CNCSIS–UEFISCDI, project number
PN II–IDEI 2278/2008.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2011.01.052.
The 1H NMR spectrum of 7a (Fig. 2) exhibits singlets for the pro-
tons of the substituted moiety of the naphthalene ring, the protons
of the benzene ring, the methylene protons connected to the naph-
thalene unit and the methyl groups connected to the benzene ring
(7.32, 6.62, 4.94 and 2.02), while the protons of the ethyleneoxide
groups give overlapped peaks in the range 3.63–3.99 ppm.
The aromatic protons Hm and Hk display signals (multiplets,
d = 7.41 and 8.10 ppm) corresponding to an AA0BB0 system as it
can be observed in symmetrically ortho-disubstituted benzenes.
In an ESI-MS experiment, samples obtained by stirring for
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