Preparation of substituted methyl o-nitrophenyl sulfides

Article abstract of DOI:10.3390/70100007

The nucleophilic substitution of substituted o-nitrochlorobenzenes with substituted methanethiolates, catalysed with triethylamine or pyridine, has been used to prepare a series of appropriately substituted methyl-o- nitrophenylsulfides. The prepared compounds were identified by their ¹H- and ¹³C-NMR spectra. The base catalysed ring closure of methyl 2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate only results in an attack of carbanion on the ester group, not on a nitro group as with the other compounds prepared. The cyclisation product is methyl 3-hydroxy-5,7-dinitro-benzo[b]thiophene-2-carboxylate (11).

Full text of DOI:10.3390/70100007

Molecules 2002, 7, 7-17
molecules
ISSN 1420-3049
http://www.mdpi.org
Preparation of Substituted Methyl o-Nitrophenyl Sulfides
Katerina Dudova‡, Frantisek Castek, Vladimir Machacek* and Petr Simunek
Department of Organic Chemistry, University of Pardubice, Čs. legií 565, 532 10 Pardubice, Czech.
Republic, Tel. +420 40 603 7015, Fax +420 40 603 7068, ‡e-mail: katerina.dudova@seznam.cz
* Author to whom correspondence should be addressed; e-mail: vladimir.machacek@upce.cz
Received: 27 September 2001; in revised form 9 November 2001 / Accepted: 13 November 2001 /
Published: 31 January 2002
Abstract: The nucleophilic substitution of substituted o-nitrochlorobenzenes with
substituted methanethiolates, catalysed with triethylamine or pyridine, has been used to
prepare a series of appropriately substituted methyl-o-nitrophenylsulfides. The prepared
1
13
compounds were identified by their H- and C-NMR spectra. The base catalysed ring
closure of methyl 2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate
only results in an attack of carbanion on the ester group, not on a nitro group as with the
other compounds prepared. The cyclisation product is methyl 3-hydroxy-5,7-dinitro-
benzo[b]thiophene-2-carboxylate (11).
Keywords: Nucleophilic aromatic substitution, sulfur nucleophiles, ring closure.
Introduction
Wagner et al. [1] have described the base-catalysed reaction of substituted 2-nitrochlorobenzenes
with esters of sulfanylethanoic acid giving the correspondingly substituted 2-alkoxycarbonyl-
benzo[d]thiazol-3-oxides. The expected intermediate of this reaction, i.e. a substituted alkyl (2-
nitrophenylsulfanyl)ethanoate, was isolated and identified in a single case – the case of ethyl (4-cyano-
2,6-dinitrophenylsulfanyl)ethanoate [1]. It is interesting that 2,6-dinitrochlorobenzene reacts with
methyl sulfanylethanoate in methanol (with triethylamine catalysis) to give 2-methoxycarbonyl-7-
nitrobenzo[d]thiazol-3-oxide, while the isomeric 2,4-dinitrochlorobenzene under the same conditions

Molecules 2002, 7
8
only gives the “open” substituted methyl (2,4-dinitrophenylsulfanyl)ethanoate, which does not undergo
any ring closure [1], Scheme 1.
Scheme 1
COOCH3
Cl
X
COOCH3
S
NO2
Y
S
+
HSCH2COOCH3
N(C2H5)3
HSCH2COOCH3
N(C2H5)3
-
NO2
N
O
O2N
NO2
X = NO2, Y = H
X = H, Y = NO2
Janík [2] developed a method for preparation of substituted methyl (2,6-dinitrophenyl-
sulfanyl)ethanoates and studied the kinetics of the cyclisation reactions of methyl (2,4,6-
trinitrophenylsulfanyl)ethanoate and methyl (4-methoxycarbonyl-2,6-dinitrophenylsulfanyl)ethanoate
to the corresponding benzo[d]thiazol-3-oxides [2,3]. On the basis of the kinetic studies he suggested
the mechanism of this cyclisation reaction. It proceeds as a multi-step reaction: the first step consists in
base-catalysed splitting off of the proton from the methylene group of the substrate to give the
corresponding carbanion, which in the second step attacks the nitrogen atom of nitro group of the same
molecule. There then follows a splitting off of hydroxyl ion and final formation of the product
(Scheme 2). The reaction rate is determined by the first two steps, which are specifically affected by
oxygen and nitrogen bases (substituted phenoxides and tertiary amines) [2,3]. The kinetic
measurements carried out so far have not allowed an unambiguous decision as to which of the first two
reaction steps is rate-limiting.
Scheme 2
COOCH3
CH2
COOCH3
CH
S
S
B
O2N
NO2
O2N
O2N
NO2
+
- BH
COOCH3
+
COOCH3
S
S
+
O
N
-
N
O2N
+
O
HO
O

Molecules 2002, 7
9
The aim of the present work was to synthesise a larger series of the “open” compounds of type I
for subsequent more detailed kinetic studies.
X
I
O2N
S
Y
NO2
Comp.
1
2
3
4
5
6
7
8
9
10
COOCH3 COOCH3 COOCH3
p-NO2-Ph p-NO2-Ph COOCH3 C6H5
X
Y
CH3
CH(CH3)2
Br
NO2
COOH
COOH
C6H5
COOH
COOCH3 COOCH3 COOCH3 p-NO2-Ph COOCH3
Results and discussion
Compounds 1 – 8 were prepared by nucleophilic substitution reaction of the chlorine substitutent
(activated for SNAr by the presence of several electron-withdrawing groups: NO2, COOCH3) by
substituted methanethiolate ions. The methanethiolate ions were generated from the corresponding
substituted methanethiols by reaction with triethylamine or pyridine. It turned out that the whole
amount of the base cannot be added at once because a high concentration of base causes an immediate
cyclisation of the primary substituted alkyl 2-nitrophenyl sulfides to benzo[d]thiazol-3-oxides (Scheme
2), as described by Wagner et al. [1]. If the base concentration is kept at a low level throughout the
reaction, then the alkyl 2-nitrophenyl sulfides can be obtained in relatively good yields.
COOCH3
Scheme 3
S
O2N
OH
Cl
11
NO2
S
O2N
COOCH3
-
HSCH2COOCH3
B
+
H3COOC
NO2
+
-
N
COOCH3
O
NO2

Molecules 2002, 7
10
The above-described method fails in the case of compound 9. In the reaction of methyl
sulfanylethanoate with methyl 2-chloro-3,5-dinitrobenzenecarboxylate in the presence of a base, the
primary methyl 2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate (9) produces a
carbanion, which can attack either the nitro group (to give the substituted benzo[b]thiazol-3-oxide) or
the ester group (to give methyl 3-hydroxy-5,7-dinitrobenzo[b]thiophene-2-carboxylate (11); Scheme
3). We have found that the attack on the ester group is so fast that the carbanion attacks this group
exclusively. This rate of attack makes it impossible to prepare methyl 2-(methoxy-
carbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate (9): even if the base was added very slowly,
and we obtained mixtures of 9 and 11 with the latter substance predominating considerably. Therefore,
compound 9 was prepared in a “roundabout” way: the nucleophilic substitution with anion of methyl
sulfanylethanoate was carried out on the 2-chloro-3,5-dinitrobenzenecarboxylate anion that was
formed by adding 1 equivalent of triethylamine to 2-chloro-3,5-dinitrobenzenecarboxylic acid. Of
course, the nucleophilic substitution itself by action of sulfanylethanoate anion (formed by addition of
the second equivalent of base) is somewhat slowed down by the presence of carboxylate group in the
substrate, but it can be accomplished without subsequent cyclisation. The esterification of the
carboxylic acid group in compound 5 was carried out only in the last step by reaction with
diazomethane under mild conditions.
Preparation of 2-(phenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylic acid 6 and methyl 2-
(phenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate 10 from 2-chloro-3,5-dinitrobenzoic acid are
described in the literature [4] without any experimental specifications and physical constants.
Janík [2] prepared methyl (2,4,6-trinitrophenylsulfanyl)ethanoate by reaction of 2,4,6-
trinitrochlorobenzene with methyl sulfanylethanoate catalysed with triethylamine in heterogeneous
phase (benzene). We have tested the possibility of preparing this substance in a homogeneous phase
(methanol). It was found that in methanolic solution the substrate undergoes a side reaction with
methoxide giving 2,4,6-trinitroanisole. The methoxide is formed at low concentration by solvolytic
reaction of the solvent with triethylamine. In order to eliminate this reaction, we adopted 1,2-
dimethoxyethane as the solvent: it is sufficiently polar for the reactants to dissolve and does not
contain acidic protons. The reactions in this solvent take place very cleanly.
Acknowledgements
The research was financially supported by the Grant Agency of the Czech Republic, Grant No.
203/01/0227.
Experimental
General methods
The synthesised substances were identified by means of their 1H- and 13C-NMR spectra, elemental
analyses and, if applicable, by comparison of their melting points with literature data. The 1H- and 13C-

Molecules 2002, 7
11
NMR spectra were measured at 25 °C with an AMX 360 Bruker spectrometer at the frequencies of
360.14 and 90.57 MHz, respectively. For the measurements the substances were dissolved in CDCl3 or
(CD3)2SO (5% solutions). The δ 1H chemical shifts are referenced to the signal of HMDSO in CDCl3
solutions (δ1H: 0.05) and to the solvent signal in (CD3)2SO solutions (δ 1H: 2.55). The δ 13C chemical
shifts are referenced to the signals of the two solvents (δ13C: 77.0 and 39.6, respectively). The analysis
of the proton spectra was carried out according to the rules for the first-order splitting with the help of
13
integral intensities. The C-NMR spectra were measured with full decoupling from the protons, and
the signals were assigned with the help of SCS. The quaternary carbon atoms and CH groups were
differentiated by means of the APT pulse sequence. The elemental analyses were carried out on an
automatic analyser EA 1108 (Fisons). The yields, melting points and elemental analyses of the
1
13
substances synthesised are presented in Table I. The H- and C-NMR spectra with assigned signals
are given in Tables IIa and IIb.
2,4,6-Trinitrochlorbenzene was prepared by treatment of 2,4,6-trinitrophenol with POCl3 in dry
pyridine [5]. The product was recrystallized from methanol, yield 54 %, m.p. 82.5-83°C (lit. [5] m.p.
80-81°C).
2-Methyl-4,6-dinitrochlorobenzene (yield 61 % after recrystallization from ethanol, m.p. 62-63°C, lit.
[6] m.p. 63-64°C) and 2-isopropyl-4,6-dinitrochlorobenzene (yield 73 % after recrystallization from
propan-2-ol, m.p. 69.5-70°C) were prepared from 2-methyl-4,6-dinitrophenol and 2-isopropyl-4,6-
dinitrophenol, respectively, by an analogous reaction [7]. For 2-isopropyl-4,6-dinitro-chlorobenzene,
C9H9N2O4Cl (244.6) calculated C: 44.19%; H: 3.71%; N: 11.45% and Cl: 14.49%; found C: 43.98%;
H: 3.50%; N: 11.29% and Cl: 14.49; 1H-NMR (CDCl3): 8.41 d (1H, J = 2.5 Hz, H5); 8.36, d (1H, J =
2.5 Hz, H3); 3.60, sept (1H, J = 6.8 Hz ,CH); 1.36, d (6H, J = 6.8 Hz, 2xCH3); 13C-NMR (CDCl3):
151.16 (C2), 149.05 (C6), 145.97 (C4), 131.49 (C1), 123.82 (C3), 117.33 (C5), 30.91 (CH), 22.08
(CH3).
2-Methyl-4,6-dinitrophenol and 2-isopropyl-4,6-dinitrophenol were prepared by dinitration [8] of the
corresponding 2-alkylphenols. 2-Bromo-4,6-dinitrophenol was prepared by the bromination of 2,4-
dinitrophenol in acetic acid [9] in 68% yield (after recrystallization from ethanol), m.p. 118-119°C, lit.
[10] m.p. 118-119°C. 2-Chloro-3,5-dinitrobromobenzene was prepared from 2-bromo-4,6-dinitro-
phenol by the same way as the 2,4,6-trinitrochlorobenzene in 77% yield (after recrystallization from
ethanol), m.p. 61-62°C, lit. [11] m.p. 63°C.
2-Chloro-3,5-dinitrobenzenecarboxylic acid was prepared by dinitration and subsequent hydrolysis
(one pot) of 2-chlorobenzonitrile [12] in 86 % yield (after recrystallization from aqueous methanol),
m.p. 199-200.5°C, lit. [13] m.p. 198-199°C. Methyl 2-chloro-3,5-dinitrobenzenecarboxylate was
prepared by esterification of the corresponding acid with methanol, m.p. 89-90°C, lit. [14] m.p. 90.3-
91°C. 4-Nitrophenylmethanethiol was prepared according to the literature method [15] by treatment of
4-nitrophenylchloromethane with thioethanoic S-acid and consequent hydrolysis of the S-acetyl

Molecules 2002, 7
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1
derivative with diluted sulfuric acid. The structure of the crude product was verified by H-NMR
spectroscopy and it was pure enough for next synthesis.
Methyl (2-methyl-4,6-dinitrophenylsulfanyl)ethanoate (1).
Methyl sulfanylethanoate (2.45 g, 0.023 mol) was added to a solution of of 2-methyl-4,6-
dinitrochlorobenzene (5 g, 0.023 mol) in 1,2-dimethoxyethane (25 mL) in a 100 mL flask at room
temperature under an inert atmosphere of Ar. A solution of triethylamine (2.34 g, 0.023 mol) in 1,2-
dimethoxyethane (5 mL) was then added dropwise with magnetic stirring over ca. 30 minutes. The
mixture was stirred an additional 1.5 h and then poured into dilute aqueous hydrochloric acid (1:1, 20
mL). The product was extracted with chloroform (2x50 mL), the organic phase was dried over
Na2SO4, and the solvent was evaporated under reduced pressure. The residue was recrystallized from
methanol yielding 5.82 g (88%) of the title product, m.p. 48-50°C.
Methyl (2-isopropyl-4,6-dinitrophenylsulfanyl)ethanoate (2) and methyl (2-bromo-4,6-di-nitro-
phenylsulfanyl)ethanoate (3) were prepared by the same way from the appropriately substituted
chlorobenzenes.
(4-Nitrophenylmethyl) (2,4,6-trinitrophenyl) sulfide (4).
Pyridine (0.79 g, 0.01 mol) was added dropwise to a stirred solution of 2,4,6-trinitrochlorobenzene
(2.5 g, 0.01 mol) and 4-nitrophenylmethanethiol (1.7 g, 0.01 mol) in methanol (40 mL) in a 100 ml
flask at room temperature under an inert atmosphere of Ar. The mixture was heated for 1 h to 40-50°C.
Cooling to –5°C followed and the resulting precipitate was collected by suction, washed successively
with water (50 mL) and cold methanol (30 mL) and then recrystallized from chloroform yielding 2.0 g
(52%) of the product, m.p. 161.5-162.5°C.
2-(Methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylic acid (5).
Methyl sulfanylethanoate (4.46 g, 0.042 mol) was added dropwise to a stirred solution of 2-chloro-
3,5-dinitrobenzoic acid (9.86 g, 0.04 mol) in 1,2-dimethoxyethane (25 mL) in a 100 ml flask at room
temperature under an inert atmosphere of Ar. Triethylamine (4.05 g, 0.04 mol) was added at once to
neutralize the carboxy group. More triethylamine (4.05 g, 0.04 mol) was then added dropwise with
stirring over a period of ca. 30 minutes. The mixture was stirred for an additional 10 minutes and then
poured into dilute aqueous hydrochloric acid (1:1, 30 mL). The product was extracted with chloroform
(3x50 mL), the organic phase was dried over Na2SO4 and the solvent was removed under reduced
pressure. The residue was recrystallized from chloroform yielding 7.8 g (62%) of the product, m.p.
109-111°C.

Molecules 2002, 7
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2-(Phenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylic acid (6) was prepared in similar fashion (two
equivalents of triethylamine were added at once and the reaction time was lengthened to 4 h at room
temperature).
2-(4-Nitrophenylmethylsulfanyl)-3,5-dinitrobenzencarboxylic acid (7).
Pyridine (0.79 g, 0.01 mol) was added in one portion at room temperature to a stirred solution of
2-chloro-3,5-dinitrobenzenecarboxylic acid (2.47 g, 0.01 mol) and 4-nitrophenylmethanethiol (1.7 g,
0.01 mol) in methanol (40 mL) in a 100 ml flask under an inert atmosphere of Ar. Additional pyridine
(0.79 g, 0.01 mol) was then added dropwise with stirring. The mixture was stirred for 1 h at a
temperature of 40-50°C and then poured into diluted aqueous hydrochloric acid (1:1, 60 mL). The
organic phase was extracted with ether (3x50 mL), dried over Na2SO4 and evaporated to dryness. The
yield after recrystallization from chloroform was 2.3 g (60%); m.p. 179.5 - 180°C.
Methyl 2-(4-nitrophenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate (8).
Pyridine (0.79 g, 0.01 mol) was added at once to a stirred solution of 2.61 g (0.01 mol) of methyl
2-chloro-3,5-dinitrobenzenecarboxylate and 1.7 g (0.01 mol) of 4-nitrophenyl-methanethiol in 40 ml of
methanol in a 100 ml flask at room temperature under the inert atmosphere of Ar. The mixture was
stirred for 1 h at the temperature of 40 - 50°C. After cooling to –5°C, the precipitate was separated by
suction and washed with 50 ml of water and 30 ml of ice-cold methanol. The yield after
recrystallization from methanol-chloroform mixture was 0.95 g (26%), m.p. 128-129°C.
Methyl 2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate (9).
A solution of diazomethane (2.40 g, 0.057 mol) in ether was cautiously poured into the solution of
2-(methoxycarbonylmethylsulfanyl)-3,5-dinitrobenzenecarboxylic acid (5) (5 g, 0.016 mol) in dry
ether (250 mL). The mixture was kept at the room temperature for 1 h. Acetic acid was added
dropwise till the evolution of nitrogen stopped. The ether was removed and the residue was
recrystallized from toluene yielding 4.2 g (80%), m.p. 76-77°C.
Reaction of methyl 2-chloro-3,5-dinitrobenzenecarboxylate with methyl sulfanylethanoate
Methyl sulfanylethanoate (0.50 g, 4.7 mmol) was added to methyl 2-chloro-3,5-dinitrobenzoate (1
g, 3.8 mmol) dissolved in methanol. Triethylamine (0.38 g, 3.8 mmol) in methanol (10 mL) was added
with stirring over a 10 minute period. The whole preparation was carried out under an inert atmosphere
of Ar. The precipitated product was separated by suction after 5 minutes and recrystallized from
toluene. The compound obtained was identified as methyl 3-hydroxy-5,7-dinitrobenzo[b]thiophene-2-
carboxylate (11). Yield: 0.80 g (71 %), m.p. 226-230 oC. Calculated for C10H6O7N2S (298.2): 40.27%
C, 2.03% H, 9.39% N, 10.75% S; found: 39.96% C, 1.90% H, 9.45% N, 10.77% S. 1H-NMR (CDCl3):

Molecules 2002, 7
14
4
13
10.08 s (1 H, OH); 9.32 and 9.14 AB (2 H, J=2.10 Hz, Ar); 4.03 s (3 H, OCH3); C-NMR (CDCl3):
166.55 (CO); 158.84, 145.16, 142.61, 137.52, 133.75 and 108.49 (6 x Cq); 124.21 and 119.92 (2 x
CH); 53.20 (OCH3).
Methyl 2-(phenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylate (10).
Distilled thionylchloride, (7.3 mL, 11.9 g, 0.1 mol) was added dropwise to a boiling solution of 2-
(phenylmethylsulfanyl)-3,5-dinitrobenzenecarboxylic acid (6) (3.34 g, 0.01 mol) in methanol (50 mL).
The solid compound that precipitated after standing overnight was collected by suction and
recrystallized from methanol yielding 3 g (86%), m.p. 114.5-115°C.
Table I. Melting points and elemental analyses of compounds 1-10
Elemental analysis
Solvent for
M.p.
(°C)
Yield
(%)
Formula /
M.w.
Comp.
Calculated / Found (%)
Br
crystallisation
C
H
N
S
C10H10N2O6S
286.3
C12H14N2O6S
314.3
41.96 3.52 9.79 11.20
41.94 3.57 9.78 11.39
45.86 4.49 8.91 10.20
45.66 4.72 8.68 10.26
Methanol
48 - 50
93.5 -95
103 - 104
88
81
78
1
2
Chloroform–
Cyclohexane
C9H7N2O6SBr 30.79 2.01 7.98 9.13 22.76
Methanol
Chloroform
Chloroform
Chloroform
Chloroform
3
351.1
C13H8N4O8S
380.3
C10H8N2O8S
316.2
C14H10N2O6S
334.3
C14H9N3O8S
379.3
C11H10N2O8S
393.3
C15H12N2O6S
330.215
C15H11N3O8S
348.3
30.60 2.09 7.92 9.35 22.79
41.06 2.12 14.73 8.43
41.27 2.03 14.69 8.43
37.98 2.55 8.86 10.14
37.99 2.56 9.13 10.16
50.30 3.01 8.38 9.59
50.00 3.23 8.20 9.59
44.33 2.39 11.08 8.45
44.48 2.36 10.87 8.51
45.81 2.82 10.68 8.15
45.90 2.78 10.52 8.22
40.00 3.05 8.48 9.71
40.27 3.02 8.37 9.49
51.72 3.47 8.04 9.20
51.64 3.5 7.89 9.05
161.5 -162.5 52
4
109 - 111
144 - 146.5
179.5 - 180
128-129
62
60
60
24
81
86
5
6
7
Methanol–
Chloroform
8
Toluene
76 - 77
9
Methanol
114.5 - 115
10

Molecules 2002, 7
15
Table IIa. 1H- Chemical Shifts (δ) of Compounds 1 – 10
Y
S
1
X
O2N
X = CH3, CH(CH3)2, Br, COOH, COOCH3
Y = COOCH3, Ph, p-NO2-C6H4
6
5
2
3
4
NO2
Comp. Solvent
H3
8.30
AB, J = 2.4 Hz
8.27 8.34
d, J = 2.3 Hz
8.45 8.67
H5
CH2
3.59
s
3.58
s
3.73
s
4.26
s
OCH3
3.66
s
3.68
s
Ph
Other
8.31
CDCl3
CDCl3
–
δ(ArCH3) 2.76 s
1
2
δ(ArCH) 3.91 sp
δ((CH3)2) 1.33 s
–
–
3.66
s
CDCl3
3
−
–
–
–
d, J = 2.4 Hz
8.69
s
8.16
7.41
CDCl3
–
4
AA'XX'
8.69
d, J = 2.5 Hz
8.66 8.86
d, J = 2.5 Hz
8.68 8.87
d, J = 2.5 Hz
8.72 8.93
d, J = 2.5 Hz
8.62 8.70
d, J = 2.5 Hz
8.72 8.93
d, J = 2.5 Hz
8.94
3.92
s
3.60
s
DMSO-d6
DMSO-d6
DMSO-d6
CDCl3
–
5
7.40-7.15
m
8.16
AA'XX'
8.15 7.41
4.25
–
–
–
6
4.37
s
4,37
s
3.74
s
4.20
s
7.41
–
7
δ(OCH3) 4.01 s
8
AA'XX'
3.66
s
CDCl3
–
δ(OCH3) 4.03 s
δ(OCH3) 4.01 s
9
7.13-7.73
m
DMSO-d6
–
10

Molecules 2002, 7
16
Table IIb. 13C-Chemical Shifts (δ) of Compounds 1 – 10
Y
S
1
X
O2N
X = CH3, CH(CH3)2, Br, COOH, COOCH3
6
5
2
3
8
9
7
10
4
H (NO2)
Y = COOCH3,
NO2
Y =
Y = C6H5,
Comp. Solvent
Ar-S-
155.19 (C6); 147.63 (C4);
X
CH2
COOCH3
C6H4NO2
168.31 (CO)
52.52 (CH3)
CDCl3 146.93 (C2); 132.99 (C1) 126.74
(C3); 116.14 (C5)
21.52 (CH3)
36.62
–
1
2
3
158.42 (C2); 155.75 (C6)
31.65 (CH)
23.63 (CH3)2
168.35 (CO)
52.64 (CH3)
CDCl3
CDCl3
148.15 (C4); 131.37 (C1)
123.13 (C3); 115.98 (C5)
158.42 (C2); 155.75 (C6)
148.15 (C4);131.37 (C1)
123.13 (C3); 115.98 (C5)
38.26
36.30
–
–
168.35 (CO)
52.64 (CH3)
–
148.18 (C10)
147.33 (C7)
130.41 (C8)
121.65 (C9)
154.92 (C2);147.82 (C4)
141.61 (C1); 124.51 (C3)
CDCl3
–
40.92
38.60
40.84
–
4
5
6
155.42 (C6); 147.91 (C4)
141.48 (C1); 134.26 (C3)
127.35 (C2); 121.61 (C5)
166.61 (CO)
53.44 (CH3)
DMSO-d6
DMSO-d6
169.27 (CO)
166.04 (CO)
–
135.89 (C7)
128.78 (C8)
127.95 (C9)
126.19 (C10)
147.95 (C10)
145.16 (C7)
127.02 (C8)
121.26 (C9)
147.85 (C10)
142.83 (C7)
126.64 (C8)
124.24 (C9)
154.04 (C6); 146.51 (C4)
140.58 (C1); 134.58 (C3)
129.08 (C2); 120.52 (C5)
–
–
–
155.43 (C6); 147.80 (C4)
142.04 (C1); 133.52 (C3)
131.12 (C2); 124.73 (C5)
DMSO-d6
CDCl3
166.73 (CO)
40.84
41.39
7
8
155.23 (C6); 147.11 (C4)
140.61 (C1); 135.20 (C3)
130.29 (C2); 120.80 (C5)
164.62 (CO)
53.97 (CH3)

Molecules 2002, 7
17
155.13 (C6); 146.96 (C4)
139.94 (C1); 135.66 (C3)
126.95 (C2); 120.99 (C5)
164.42 (CO)
53.85 (CH3)
168.34 (CO)
52.94 (CH3)
CDCl3
CDCl3
38.37
42.10
–
9
139.91 (C7)
128.99 (C8)
128.33 (C9)
126.60 (C10)
154.56 (C6); 146.29 (C4)
137.58 (C1); 135.21 (C3)
129.32 (C2); 120.84 (C5)
164.81 (CO)
53.80 (CH3)
–
10
References
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Sample Availability: Samples are available from the authors.
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