Macrocycles with a phenothiazine core: Synthesis, structural analysis, and electronic properties

Article abstract of DOI:10.1016/j.tetlet.2012.12.068

New phenothiazine macrocycles with polyethyleneoxy chains were synthesized in good yields by reacting 10-ethyl-10H-3,7-di(3-hydroxyphenyl)phenothiazine with diiodurated or ditosylated polyethyleneglycols. Their structures were investigated by NMR spectros

Full text of DOI:10.1016/j.tetlet.2012.12.068

Tetrahedron Letters 54 (2013) 1107–1111
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Macrocycles with a phenothiazine core: synthesis, structural analysis,
and electronic properties
Ilißsca Medrußt a, Raluca Turdean a, Radu Gropeanu a, Flavia Pop a, Loïc Toupet b, Niculina D. Ha˘dade a,
a
Elena Bogdan a, , Ion Grosu
⇑
a Babeßs-Bolyai University, Supramolecular Organic and Organometallic Chemistry Center (SOOMCC), Cluj-Napoca, 11 Arany Janos Str., 400028 Cluj-Napoca, Romania
b Université de Rennes I, UMR 6626, 35042 Rennes Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
New phenothiazine macrocycles with polyethyleneoxy chains were synthesized in good yields by react-
ing 10-ethyl-10H-3,7-di(3-hydroxyphenyl)phenothiazine with diiodurated or ditosylated polyethylene-
glycols. Their structures were investigated by NMR spectroscopy and single crystal X-ray
crystallography in the case of one compound. The electronic properties were determined by absorption
spectroscopy and cyclic voltammetry and their complexation ability for alkali cations was investigated
by ES-HRMS.
Received 4 October 2012
Revised 3 December 2012
Accepted 13 December 2012
Available online 25 December 2012
Keywords:
Phenothiazines
Macrocycles
Ó 2012 Elsevier Ltd. All rights reserved.
X-ray molecular structure
C–Hꢀ ꢀ ꢀ
p interactions
ES-HRMS investigations
Phenothiazine is an important nitrogen–sulfur heterocycle and
its derivatives exhibit broad pharmacological and biological
activities, being used as sedatives, tranquilizers, antituberculotics,
antipyretics, antitumor agents, bactericides, or parasiticides.1 Phe-
nothiazine derivatives have good donor abilities and low oxidation
potential and form stable radical cations2 and their physiological
activities can be attributed to these properties.1,3 Phenothiazine
has a ‘butterfly structure’,4 and on oxidation to radical cation adopts
a planar geometry. Due to its interesting properties, phenothiazine
has become a popular heterocyclic unit used in material sciences5
and also in biology and biochemistry as a marker for proteins,
DNA, or other biochemical systems.6 Phenothiazine is found as a
core unit in redox-active alkylated7 and heteroarylated8 bi- and ter-
phenothiazines, oligophenothiazine-fullerene dyads,9 cruciform
fluorophores,10 molecular wires,11 or ligands for surface modifica-
tion.12 There are very few reported macrocycles with phenothiazine
units, the most representative being the cyclophanes with phenothi-
azine and bipyridinium or with two phenothiazine units.13
starting from 10H-phenothiazine 1 (Scheme 1). The alkylation of 1
with ethyl iodide was followed by core bromination of 10-ethyl-
10H-phenothiazine 2 to afford 3 in 76% yield.14 The diboronic dies-
ter 4 was synthesized according to the literature,15 and further
subjected to Suzuki cross-coupling16 with 3-bromophenol to give
10-ethyl-10H-3,7-di(3-hydroxyphenyl)phenothiazine
5 in good
yield (60%). Next, diphenol 5 was reacted with either diiodurated
or ditosylated polyethyleneglycols in acetonitrile at high dilution,
to afford the macrocycles 6 with different cavity sizes (Scheme 1,
yields up to 32%).17
The structure of the macrocycles 6 was confirmed by their mass
and NMR spectra and also by single crystal X-ray diffraction for 6b
(Fig. 1).18
The solid state molecular structure shows the butterfly confor-
mation of the phenothiazine core with a boat conformation for the
six-membered heterocycle and a bowsprit orientation of the ethyl
substituent located on the N atom (Fig. 1). On the other hand, there
are four types of molecules in the lattice (Fig. 2a), which exhibit
differences between the torsion angles of the aromatic units and
between the torsion angles in the chains. The angles between the
planes of the benzene units of the phenothiazine core have differ-
Herein we report the synthesis, structural analysis, and com-
plexation studies of the first phenothiazine macrocycles embedded
in ethylenoxide chains of various lengths (Scheme 1).
The building block for the synthesis of the target macrocycles
was the diphenol 5 which was obtained via a multistep procedure
ent values in the four types of molecules (a = 28.6°, 32.1°, 41.4°,
and 46.7°). The aromatic substituents at positions 3 and 7 are not
coplanar with the benzene rings of the phenothiazine units and
the dihedral angles between their planes are all different, the eight
values varying from 13.15° to 34.47°. This peculiar situation occurs
⇑
Corresponding author. Tel.: +40 264 593833; fax: +40 264 590818.
E-mail address: ebogdan@chem.ubbcluj.ro (E. Bogdan).
as the result of numerous C–Hꢀ ꢀ ꢀp and C–Hꢀ ꢀ ꢀp contacts, which
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.12.068

1108
I. Medrußt et al. / Tetrahedron Letters 54 (2013) 1107–1111
H
N
N
N
KOtBu, THF
Br2, CH3COOH
S
1
S
Br
S
3
Br
rt, overnight
76%
C2H5I, rt
90%
2
1. nBuLi, THF, -78 oC, 20 min
2. B(OCH3)3, -78 oC, 30 min
3. pinacol, rt, 2 h
3-bromophenol
N
S
N
S
Pd[PPh3]4, K2CO3
DME:H2O
O
O
B
B
95 oC, 14 h
60%
O
O
4. AcOH, rt, 14 h
OH
OH
43%
4
5
X
O
X
n
N
S
Cs2CO3, CH3CN
6a, m = 1, 32%
X = I, OTs; n = 3-5
reflux, 7 d
O
O
O
O
O
6b
6c
, m = 2, 52%
, m = 3, 37%
m
Scheme 1.
oxygen atoms of the chains exhibit intra- and intermolecular C–
Hꢀ ꢀ ꢀp contacts involving the H atoms of the polyethyleneoxide
units (see the Supplementary data).
The 1H NMR spectra of 6a–c exhibit characteristic patterns for
the phenothiazine core and for the polyethyleneoxide chains with
four, five, and six ethyleneoxy units, respectively. The similar aro-
matic units as well as the similar parts of the ethyleneoxy chains
are magnetically equivalent showing unique sets of signals. How-
ever, a certain flexibility of the chains and a partial rotation of
the aromatic substituents of the heterocyclic core have to be taken
into consideration, and these motions, at the average of the confor-
mational equilibria, render the similar groups of the macrocycles
equivalent in the NMR.
The electronic properties of the macrocycles 6a–c were investi-
gated by UV–Vis absorption spectra and cyclic voltammetry. The
electrochemical data of the compounds 6a–c were obtained by
cyclic voltammetry at room temperature in the anodic region,
and the redox potentials calculated against ferrocene are summa-
rized in Table 1. The one-electron reversible oxidation potentials
of phenothiazine derivatives 6a–c are in the expected regions for
phenothiazine derivatives and correspond to the formation of
Figure 1. Molecular structure of macrocycle 6b.
ensure the favorable packing in the lattice. Thus, one can consider
the lattice to be formed by pairs of macrocycles (highlighted in dif-
ferent colors: blue–orange and green–pink) exhibiting perpendicu-
lar phenothiazine cores (Fig. 2a).
In each pair considered, the benzene rings of the phenothiazine
cores and one phenol ring exhibit edge-tilted to face (T) structures
(Fig. 2b and c). Thus, in the green–pink assembly, the dihedral an-
stable phenothiazine radical cations. Compared to N-methyl-phe-
nothiazine (E00/+1 = 767 mV)7c and N-hexyl-phenothiazine [(E0
=
0/+1
728 mV),7c N-ethyl-phenothiazine has, most probably, an
intermediate value of E00/+1], anodic shifts being observed for mac-
rocycles 6a–c. This is consistent with the electrochemical behavior
gles between the similar aromatic rings are
for the rings of the phenothiazine core and
nol rings, while the C–Hꢀ ꢀ ꢀ contacts correspond to the H-centroid
of aromatic ring distances d = 2.941, 2.823, and 3.039 Å. The similar
data for the orange–blue assembly are: = 79.15°, 84.95°, and
67.92° and d = 2.904, 2.814, and 3.093 Å, respectively. Additionally,
contacts between H atoms of the chains and aromatic
a
= 76.83° and 84.36°
of other 3,7-aryl substituted phenothiazines bearing electron-
a
= 62.14° for the phe-
withdrawing groups.14 The difference in E0
of the three macro-
0/+1
p
cycles is probably due to the enclosure of the macrocycles which
favors the increase of the torsion angle of the benzene rings
belonging to the phenoxy units with respect to the phenothiazine
core. The quasi-orthogonal orientation of the benzene rings re-
a
C–Hꢀ ꢀ ꢀ
p
duces the influence of the phenoxy substituents to the ꢁI effect.
units of the neighboring macrocycles could also be observed in
both assemblies [d = 2.893 Å (Fig. 2b) and d = 2.806 Å (Fig. 2c)].
Some relevant interactions can be also noticed between mole-
cules belonging to different assemblies. For the green–blue
(Fig. 2d) and pink–orange (Fig. 2e) pairs, T structures involving
one of the benzene rings of the phenothiazine cores could be ob-
0/+1
The higher observed value of the E0
(824 mV) for the
Table 1
Selected electronic properties of macrocycles 6aꢁc
a
0/+1b
Compd
Absorption kmax,
(nm)
E0
(mV)
abs
served. The characteristic data are:
a
= 85.09° and 84.28°;
contacts involving
6a
6b
6c
276, 327
280, 335
280, 333
824
777
786
d = 2.759 and 2.960 Å, respectively. C–Hꢀ ꢀ ꢀ
p
the H atoms of the methyl groups of the orange and green mole-
cules respectively, and the phenol units of their partners were also
revealed (distances from the H atom to the centroid of the aromatic
unit d = 2.905 and 3.110 Å, respectively). Other details of the inter-
a
Adsorption spectra were recorded at room temperature in CH2Cl2.
Cyclic voltammetry measurements were performed in CH2Cl2 at rt,
b
m
= 100 mV/
s, electrolyte: nBu4N+PF6ꢁ, Pt working electrode, Pt counter electrode, and Ag/AgCl
pseudo reference electrode.
molecular C–Hꢀ ꢀ ꢀ
p contacts in the lattice are given in the SI. The

I. Medrußt et al. / Tetrahedron Letters 54 (2013) 1107–1111
1109
Figure 2. (a) Part of the crystal structure of 6b showing the four different types of molecules; view of the lattice showing selected C–Hꢀ ꢀ ꢀ
p
interactions between the pair of
molecules, (b) green–pink assembly, (c) orange–blue assembly, (d) green–blue assembly, (e) pink–orange assembly.
0/+1
macrocycle with the shortest chain 6a, could be attributed to a
nearly coplanar disposition of the phenolic rings with respect to
the phenothiazine unit (conformation in which both ꢁI effect of
OH group and ꢁE effect of the phenyl ring can operate). A coplanar
disposition of the aromatic rings ensures the shortest distance be-
tween the oxygen atoms of the phenoxy substituents. The increas-
ing number of the ethyleneoxy units leads to an increase of the
torsion of the phenoxy substituents of the phenothiazine core hav-
ing as result the decrease of the E0
values. A similar trend was
observed for the variation of kmax (in these cases diminishing of
the kmax values) when the spectra of 6b and those of 6a and 6c
were compared.
In order to investigate their ability to complexation of alkali me-
tal cations, which is characteristic for the crown ether class,19 the
macrocycles 6a–c were subjected to ES-HRMS experiments that re-
vealed high affinities for Li+, Na+, and K+ cations. The investigations

1110
I. Medrußt et al. / Tetrahedron Letters 54 (2013) 1107–1111
Table 2
References and notes
Relative intensity peaks of complexes of macrocycles 6a–c and alkali metal cations
(samples of equimolecular amounts of 1.5 ꢂ 10ꢁ4 M solution of
6 dissolved in
1. (a) Mietzsch, F. Angew. Chem. 1954, 66, 363; (b) Ionescu, M.; Mantsch, H. Adv.
Heterocycl. Chem. 1967, 8, 83; (c) Bodea, C.; Silberg, I. Adv. Heterocycl. Chem.
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Albery, W. J.; Foulds, A. W.; Hall, K. J.; Hillman, A. R.; Edgell, R. G.; Orchard, A. F.
Nature 1979, 282, 793; (f) Silberg, I. A.; Cormos, G.; Oniciu, D. C. Adv. Heterocycl.
Chem. 2006, 90, 205.
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Chem. Soc. Jpn. 1971, 44, 663.
acetonitrile and 1:1:1:1:1 mixture of LiCl, NaSCN, KSCN, Rb2CO3, and Cs2CO3, each salt
1.5 ꢂ 10ꢁ4 M solution dissolved in acetonitrile).
6a (%)
6b (%)
6c (%)
[M+Li]+
[M+Na]+
[M+K]+
100
78
78
—
—
11
37
100
60
—
—
21
6
59
100
—
2
4
[M+Rb]+
[M+Cs]+
[2M+K]+
4. (a) Bell, J. D.; Blount, J. F.; Briscoe, O. V.; Freeman, H. C. Chem. Commun. 1968,
1656; (b) Pan, D.; Philips, L. J. Phys. Chem. A 1999, 103, 4737.
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Cabaj, J.; Bartoszek, M.; Sulkowski, W. W. Electrochim. Acta 2008, 53, 2545.
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104, 7574; (b) Tierny, M.; Grinstaff, M. W. J. Org. Chem. 2000, 65, 5355; (c)
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Wagner, C.; Wagenknecht, H.-A. Chem. Eur. J. 1871, 2005, 22.
7. (a) Müller, T. J. J. Tetrahedron Lett. 1999, 40, 6563; (b) Krämer, C. S.; Zeitler, K.;
Müller, T. J. J. Org. Lett. 2000, 2, 3723; (c) Krämer, C. S.; Müller, T. J. J. Eur. J. Org.
Chem. 2003, 3534.
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Müller, T. J. J. Tetrahedron Lett. 2006, 47, 8329.
were performed with solutions containing equimolecular amounts
of multicomponent mixtures formed by the macrocyclic host and
the five guest cations as well as samples containing the macrocycle
and a single guest cation. Thus, the mass spectra of the solutions of
equimolecular amounts of macrocycle 6 and LiCl, NaSCN, KSCN,
Rb2CO3, and Cs2CO3 showed the highest preference to formation
of [6a+Li]+, [6b+Na]+, and [6c+K]+ complexes, respectively (Table 2),
according to the macrocycle cavity size. Macrocycles 6a and 6b,
with four and five ethyleneoxy units, also exhibited a peak corre-
sponding to sandwich20 [2M+K]+ complexes, besides the 1:1 com-
plex with K+ (Table 2). There were no traces of the [M+Rb+] or
[M+Cs+] peaks for macrocycles 6 even in the samples containing
only the macrocycle and rubidium or cesium carbonate, except
for 6c which exhibited a peak corresponding to the complex with
Cs+ (Table 2). However, the experiments conducted with lithium
chloride revealed some interesting aspects. The ES-HRMS spectra
of the samples of macrocycles 6 and LiCl showed no affinity for
the lithium cation, while in the samples of 6 with equimolecular
amounts of the alkali metal salts, the corresponding [M+Li]+ peak
was present (Table 2). This noticeable change in complexation abil-
ity can be explained by the change in pH to slightly basic,21 since in
the samples containing all alkali metal salts the corresponding car-
bonates (for Rb and Cs) or thiocyanates (for Na and K) were used
and chloride for Li.
10. Hauck, M.; Schönhaber, J.; Zucchero, A. J.; Hardcastle, K. I.; Müller, T. J. J.; Bunz,
U. H. F. J. Org. Chem. 2007, 72, 6714.
11. Sailer, M.; Franz, A. W.; Müller, T. J. J. Chem. Eur. J. 2008, 14, 2602.
12. (a) Franz, A. W.; Zhou, Z.; Turdean, R.; Wagener, A.; Sarkar, B.; Hartmann, M.;
Ernst, S.; Thiel, W. R.; Müller, T. J. J. Eur. J. Org. Chem. 2009, 3895; (b) Turdean,
R.; Bogdan, E.; Terec, A.; Petran, A.; Vlase, L.; Turcu, I.; Grosu, I. Cent. Eur. J.
Chem. 2009, 7, 111; (c) Franz, A. W.; Stoycheva, S.; Himmelhaus, M.; Müller, T.
J. J. Beilstein J. Org. Chem. 2010, 6, 1.
13. (a) Petry, C.; Lang, M.; Staab, H. A.; Bauer, H. Angew. Chem., Int. Ed. Engl 1993,
32, 1711; (b) Bauer, H.; Stier, F.; Petry, C.; Knorr, A.; Stadler, C.; Staab, H. A. Eur.
J. Org. Chem. 2001, 3255; (c) Memminger, K.; Oeser, T.; Müller, T. J. J. Org. Lett.
2008, 10, 2797.
14. Sailer, M.; Nonnenmacher, M.; Oeser, T.; Müller, T. J. J. Eur. J. Org. Chem. 2006,
423.
15. Krämer, C. S.; Zimmerman, T. J.; Sailer, M.; Müller, T. J. J. Synthesis 2002, 1163.
16. (a) Krämer, C. S.; Zeitler, K.; Müller, T. J. J. Tetrahedron Lett. 2001, 42, 8619; (b)
Sailer, M.; Gropeanu, R. A.; Müller, T. J. J. J. Org. Chem. 2003, 68, 7509.
17. General procedure for the synthesis of macrocycles 6a–c: A solution of 1 mmol of
diiodurated tetraethylene glycol (for 6a), ditosylated pentaethylene glycol (for
6b), and ditosylated hexaethylene glycol (for 6c) in dry acetonitrile was added
over 3 days to a solution of diphenol 5 (1 mmol) and Cs2CO3 (5 mmol) in dry
acetonitrile at reflux. The stirring under reflux was continued for additional
4 days. After cooling to room temperature, water (100 ml) and
dichloromethane (50 ml) were added to the reaction mixture, the organic
layer was separated and the aqueous layer was extracted with
dichloromethane (2 ꢂ 50 ml). The combined organic layers were washed
with brine, dried with sodium sulfate and the solvents were removed in
vacuum. The residue was adsorbed on silica gel and was purified by column
chromatography.
In summary, we report here the synthesis, structural analysis,
and complexation ability of new phenothiazine macrocycles. To
the best of our knowledge these are the first examples of crown
ethers embedding phenothiazine units. Macrocycles 6 exhibit an
electrochemical behavior similar to N-alkyl phenothiazine. The
ES-HRMS experiments performed in order to determine the affinity
of 6 for alkali cations, revealed a high affinity of 6a for Li+, 6b for
Na+, and 6c for K+, respectively. In the case of 6b, the solid state
molecular structure investigations showed numerous intra- and
29-Ethyl-7,10,13,16,19-pentaoxa-37-thia-29-aza-hexacyclo
[23.7.5.1.2,61.20,240.28,360.30,38]-nonatriconta-1(32),2,4,6(33),
20(34),21,23,25,27,30,35,37-dodecaene (6a)
intermolecular C–Hꢀ ꢀ ꢀp and C–Hꢀ ꢀ ꢀ
p interactions.
Yield 32% (182 mg), light green solid, mp = 195–196 °C; Rf = 0.59 (pentane:
ethyl acetate = 3:1); ES-HRMS: calcd for C34H36NO5S [M+H]+: 570.2303, found:
570.2309. 1H NMR (300 MHz, CD2Cl2) d ppm: 1.49 (3H, t, J = 6.9 Hz), 3.68 (8H,
s), 3.81 (4H, t, J = 6.6 Hz), 4.01 (2H, q, J = 6.9 Hz), 4.24 (4H, t, J = 6.3 Hz), 6.83
(2H, dd, J = 8.1; J0 = 2.4 Hz), 7.03 (2H, d, J = 8.1 Hz), 7.16–7.21 (4H, overlapped
peaks), 7.29 (2H, t, J = 7.8 Hz), 7.42 (2H, dd, J = 8.4, 1.8 Hz), 7.53 (2H, d,
J = 1.8 Hz).13C NMR (75 MHz, CD2Cl2) d ppm: 13.44 (CH3), 41.67 (N–CH2),
67.65, 70.13, 71.10, 71.19 (CH2), 112.69, 115.95, 116.05, 118.75, 126.24,
127.51, 130.11 (CH; aromatic), 125.74, 136.65, 141.85, 145.96, 159.72
Acknowledgements
This work was supported by CNCS–UEFISCDI (projects PN-II-
IDEI_2278/2008 and PNII-ID-PCCE-2011-2-0027). I. Medrußt thanks
for
a Ph.D. scholarship, project co-financed by the Sectorial
(Cquaternary
;
aromatic). ES(+)-HRMS: m/z = 570.23 [M+H]+; 576.24 [M+Li]+;
operational program for human resources development 2007–
2013 Priority Axis 1. ‘Education and training in support for growth
and development of
intervention 1.5: Doctoral and post-doctoral programs in support
of research; Contract No. POSDRU/88/1.5/S/60185–‘Innovative
Doctoral Studies in a Knowledge Based Society’, Babesß-Bolyai
University, Cluj-Napoca, Romania.
592.21 [M+Na]+; 608.19 [M+K]+; 1139.46 [2M+H]+; 1177.41 [2M+K]+.
32-Ethyl-7,10,13,16,19,22-hexaoxa-40-thia-32-aza-hexacyclo
[26.7.5.1.2,61.23,270.31,390.33,41]-dotetraconta-1(35),2,4,6(36),
23(37),24,26,28,30,33,38,41-dodecaene (6b)
a knowledge based society’ Key area of
Yield 52% (319 mg), light green solid, mp = 114–115 °C; Rf = 0.51
(pentane:ethyl acetate = 1:2); ES-HRMS: calcd for
C
36H40NO6S [M+H]+:
614.2573, found: 614.2571. 1H NMR (300 MHz, CDCl3) d ppm: 1.51 (3H, t,
J = 7.0 Hz), 3.70–3.78 (12H, overlapped peaks), 3.86 (4H, t, J = 5.8 Hz), 4.02 (2H,
q, J = 7.0 Hz), 4.24 (4H, t, J = 5.8 Hz), 6.87 (dd, 2H, J = 8.0, 1.8 Hz), 6.98 (2H, d,
J = 8.4 Hz), 7.14–7.19 (4H, overlapped peaks), 7.32 (t, 2H, J = 8.0 Hz), 7.41 (4H,
dd, J = 7.4 Hz, 2.0 Hz), 7.48 (2H, d, J = 2.0 Hz). 13C NMR (75 MHz, DMSO-d6) d
ppm: 13.16 (CH3), 41.65 (N–CH2), 67.48, 69.72, 70.78, 70.92, 76.67 (CH2),
112.71, 114.87, 115.38, 118.84, 125.98, 128.45, 129.77 (CH, aromatic), 124.82,
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.
2012.12.068.
133.56, 135.83, 141.34, 159.26 (Cquaternary
; aromatic). ES(+)-HRMS: m/
z = 614.26 [M+H]+; 620.36 [M+Li]+; 636.24 [M+Na]+; 652.21 [M+K]+; 1227.51
[2M+H]+; 1265.46 [2M+K]+.

I. Medrußt et al. / Tetrahedron Letters 54 (2013) 1107–1111
1111
35-Ethyl-7,10,13,16,19,22,25-heptaoxa-43-thia-35-aza-hexacy
clo[29.7.5.1.2,61.26,300.34,420.36,44]-pentatetraconta-1(38),2,4,6
(39),26(40),27,29,31,33,36,41,44-dodecaene (6c)
ES(+)-HRMS: m/z = 658.28 [M+H]+; 664.29 [M+Li]+; 680.27 [M+Na]+; 696.24
[M+K]+; 790.18 [M+Cs]; 1353.52 [2M+K]+.
18. Crystallographic data of the structure reported in this Letter have been
deposited at the Cambridge Crystallographic Data Center as supplementary
publication no CCDC-278084. Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK or as
Supplementary data of this Letter.
19. Blair, S. M.; Kempen, E. C.; Brodbelt, J. S. J. Am. Soc. Mass Spectrom. 1998, 9,
1049.
20. Nicoll, J. B.; Dearden, D. V. Int. J. Mass Spectrom. 2001, 204, 171.
21. Alfonso, I.; Astorga, C.; Gotor, V. J. Inclusion Phenom. Macrocycl. Chem. 2005, 53,
131.
Yield 37% (243 mg), light green solid, mp = 108–109 °C; Rf = 0.34
(pentane:ethyl acetate = 1:5); ES-HRMS: calcd for
C
38H44NO7S [M+H]+:
658.2836, found: 658.2833. 1H NMR (300 MHz, CD2Cl2) d ppm: 1.49 (3H, t,
J = 6.9 Hz), 3.66–3.72 (16H, overlapped peaks), 3.86 (4H, t, J = 5.1 Hz), 4.04 (2H,
q, J = 6.9 Hz), 4.24 (4H, t, J = 5.1 Hz), 6.87 (2H, dd, J = 8.1, 2.4 Hz), 7.01 (2H, d,
J = 7.2 Hz), 7.19–7.25 (4H, overlapped peaks), 7.36 (2H, t, J = 7.8 Hz), 7.47–7.49
(4H, overlapped peaks). 13C NMR (75 MHz, CD2Cl2) d ppm: 13.1 (CH3), 42.1 (N–
CH2), 67.9, 69.9, 70.8, 70.9, 71.2 (CH2), 113.4, 113.6, 115.5, 118.9, 126.0, 126.2,
130.1 (CH, aromatic), 124.6, 135.3, 141.3, 144.7, 159.6 (Cquaternary; aromatic).