α-Substituted β-mercapto ketone based synthesis of 3-alkyl-3-[(alkylsulfanyl)methyl]-2-methyl-3H-indoles

Article abstract of DOI:10.1007/s10593-021-02940-4

[Figure not available: see fulltext.] A novel approach to the synthesis of 3-(alkylsulfanylmethyl)-substituted 1H-indoles was developed based on the Fischer indole synthesis involving accessible β-mercapto ketones. Heterocyclization of 3-[(alkylsulfanyl)methyl]alkan-2-ones and phenylhydrazine by the action of ZnCl₂ in MeOH or EtOH gave previously unknown 3-alkyl-3-[(alkylsulfanyl)methyl]-2-methyl-3H-indoles.

Full text of DOI:10.1007/s10593-021-02940-4

DOI 10.1007/s10593-021-02940-4
Chemistry of Heterocyclic Compounds 2021, 57(5), 543–547
α-Substituted β-mercapto ketone based synthesis of
3-alkyl-3-[(alkylsulfanyl)methyl]-2-methyl-3H-indoles
Larisa А. Baeva1*, Radik M. Nugumanov1,
Rail R. Gataullin1, Akhnef А. Fatykhov1
1 Ufa Institute of Chemistry, Ufa Federal Research Center of the Russian Academy of Sciences,
69 Oktyabrya Ave., Ufa 450054, Russia; е-mail: sulfur@anrb.ru
Submitted December 29, 2020
Accepted February 4, 2021
Translated from Khimiya Geterotsiklicheskikh Soedinenii,
2021, 57(5), 543–547
A novel approach to the synthesis of 3-(alkylsulfanylmethyl)-substituted 1H-indoles was developed based on the Fischer indole synthesis
involving accessible β-mercapto ketones. Heterocyclization of 3-[(alkylsulfanyl)methyl]alkan-2-ones and phenylhydrazine by the action
of ZnCl2 in MeOH or EtOH gave previously unknown 3-alkyl-3-[(alkylsulfanyl)methyl]-2-methyl-3H-indoles.
Keywords: 3H-indole, indolenine, β-mercapto ketone, phenylhydrazine, Fischer reaction.
2(3)-Substituted indole derivatives, including those con-
taining the methylsulfanyl fragment, are incorporated in the
structures of natural alkaloids1 and pharmacologically
useful substances.2 Thus, (7-methoxy-1H-indol-3-yl)[bis-
(methylsulfanyl)]acetonitrile isolated from the seeds of
Dithyrea wislizenii is one of the simplest compounds with
antifeedant properties.1e,f And 6-bromo-4-dimethylamino-
methyl-5-hydroxy-1-methyl-2-phenylsulfanylmethylindole-
3-carboxylic acid ethyl ester hydrochloride salt
(umifenovir) has a broad spectrum of antiviral activity.2d–f
Among 2(3)-aryl(alkyl,hetaryl)sulfanylmethyl-1H-indoles,
substances that are active against hepatitis B,3 chikungunya4
viruses, and HIV,5 as well as have antiparkinsonian,6
antidepressant6c,7 properties and other types of neuro-
psychotropic action6c,8 were found. Introduction of
arylsulfanyl(sulfonyl)methyl groups in the molecule of
indoles with their subsequent transformation was proposed
for the synthesis of useful 3,3'-bisindolylmethanes,9а mono-
fluoromethyl-substituted indoles,9b and other compounds.9c,d
The existing methods for the synthesis of 2(3)-aryl-
(alkyl,hetaryl)sulfanylmethyl-1H-indoles, as a rule, are
based on the functionalization of indole derivatives. Thus,
for the preparation of 3-(methylsulfanylmethyl)-substituted
1H-indoles, the reaction of 1H-indoles with sulfoxonium
ylides, which are obtained by the action of such reagents as
trifluoroacetic anhydride,9a dicyclohexylcarbodiimide,10b
CuBr(PPh3)3 and NH4OAc mixture9a,10 on dimethyl
sulfoxide9a,10 or methylsulfanylmethyl acetate,10a is used.
Another method for the synthesis of these compounds is
the three-component condensation of indoles with
aldehydes and thiols in the presence of bases11 or Lewis
acids.12 Reactions of indoles with α-chloro sulfides,13a
α-bromo sulfones,13b or alkyl(benzyl)sulfanylmethyl-
amines,14 as well as the reaction of indol-3-ylmethanol15
and indol-3-ylmethyldialkylamines16 with thiols are of
importance.
To access 3-(methylsulfanylmethyl)-substituted 3H-indoles
(indolenines), the reaction of 1H-indoles with dimethyl
sulfide and N-chlorosuccinimide (the Corey–Kim reagent)
in the presence of a base was proposed.17 An alternative
method for the preparation of 3,4-dihydro-1H-thiopyrano-
[4,3-b]indoles by the reaction of arylhydrazine
hydrochlorides with 3-methyltetrahydrothiopyran-4-one in
the presence of 5–28% solutions of hydrogen chloride in
EtOH was described by a study.18 However, the proposed
cyclization is limited to the use of thiopyran-4-one and its
S,S-dioxide.
Direct functionalization of indole rings using
sulfoxonium ylides or sulfonium imides grants access to
exclusively 3-(methylsulfanylmethyl)-substituted indole
derivatives. Other methods usually involve multistep
transformations.
In this work, we used an approach based on the
heterocyclization of phenylhydrazine with functionalized
0009-3122/21/57(5)-0543©2021 Springer Science+Business Media, LLC
543

Chemistry of Heterocyclic Compounds 2021, 57(5), 543–547
Scheme 1
ketones (Fischer indole synthesis)19 in the presence of
ZnCl2 to obtain novel 3-alkylsulfanylmethyl-3H-indoles.
Table 1. Yields of 3H-indoles 2a,c,f depending on
the conditions of the condensation of 4-(alkylsulfanyl)-3-methyl-
butan-2-ones 1a,c,f with phenylhydrazine in the presence of
ZnCl2 (molar ratio 1:1:0.4, reflux)
20
As the ketone component, we chose such β-mercapto
ketones as 4-(alkylsulfanylmethyl)-substituted butan- or
hexan-2-ones, easily obtained as a result of the three-
component condensation of the accessible butan-2-one
(methyl ethyl ketone) or hexan-2-one with formaldehyde
and thiols or sodium sulfide.21 The sources of methanethiol
and sodium sulfide were waste sulfide-alkaline solutions
formed during alkaline purification of gas condensates and
hydrogen sulfide containing gas streams, respectively.21а–с
The use of methyl ketones in reaction with phenyl-
hydrazine makes it possible to regioselectively obtain
2-methylindoles, since cyclization in acidic media involves
the more substituted alkyl group at the carbonyl
functionality.19
Reaction conditions
Starting
compound
3H-Indole Yield, %
Solvent
MeOH
MeOH
MeOH
MeOH
MeOH*
MeOH
EtOH
Time, h
3
6
9
9
9
6
6
9
9
1а
2а
2а
2а
2с
2с
2f
15
92
64
66
8
1а
1а
1с
1с
1f
14
17
1f
2f
EtOH
1f
2f
* 0.5 equiv ZnCl2.
The reaction of 4-(alkylsulfanyl)-3-methylbutan-2-ones
1a–d with an equimolar amount of phenylhydrazine in
MeOH in the presence of ZnCl2 (0.4 equiv) as a Lewis acid
for 7–9 h gave the corresponding 3-[(alkylsulfanyl)methyl]-
2,3-dimethyl-3H-indoles 2a–d in 56–92% yields (Scheme 1).
By decreasing the reaction time, the yield of 3H-indole 2а
decreases (Table 1). According to gas-liquid chromato-
graphy data, after 6 h, the reaction mixture was composed
of 31% of the starting compound 1a, 13% of indole 2a, and
37% of an intermediate product which turned out to be
unstable under the conditions of column chromatography
and was transformed into compound 2a during isolation.
By the model reaction of β-mercapto ketone 1c with
phenylhydrazine, it was demonstrated that an increase in
the amount of catalyst has no effect on the yield of
3H-indole 2c (Table 1).
3H-Indole 2a was obtained earlier in 82% yield by the
reaction of 2,3-dimethyl-1H-indole with dimethyl sulfide
and N-chlorosuccinimide (the Corey–Kim reagent) in the
presence of diisopropylethylamine in CH2Cl2 under an
argon atmosphere at –78°С.17 Considering the accessibility
of the starting reagents, process conditions that do not
require cooling, and a higher yield of the target product,
our proposed method for preparing compound 2a has
advantages over the existing one.
The reaction of 4,4-thiobis(3-methylbutan-2-one) (1f)
with phenylhydrazine proceeds with 41% conversion of the
starting compound under the conditions analogous to the
preparation of 3H-indoles 2a–d. When MeOH is replaced
by EtOH, the conversion of β-mercapto ketone 1f reached
48%; however, the predominant reaction product was
2,3-dimethyl-1H-indole (3) (31% yield). The yield of
3H-indole 2f did not exceed 17%. The formation of
compound 3 can be explained by probable aromatization of
the intermediate 2,3,3-substituted indolin-2-amine (A) as a
result of the retro-Mannich reaction, analogous to that
described in the literature.22 It is also known that 2,3,3-
substituted 3H-indoles are stable compounds23 whereas
3,3-disubstituted indolenines in an acidic medium can
undergo the Plancher rearrangement with the formation of
2,3-disubstituted isomers.24 It is possible that elimination of
the СH2SCH2CH(Me)COMe fragment from indole 2f is
completed not by migration but by cleavage of the C–S
bond and transformation into a stable compound.22c The
latter assumption may be supported by the fact that the
formation of 2,3-dimethyl-1H-indole (3) is practically not
observed in the reaction of phenylhydrazine with
(hexylsulfanylmethyl)-substituted butan-2-one 1d.
We failed to obtain indole 2g from 4-(methylsulfanyl)-
3-[(methylsulfanyl)methyl]butan-2-one (1g). At the same
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Chemistry of Heterocyclic Compounds 2021, 57(5), 543–547
time, 3-[(methylsulfanyl)methyl]hexan-2-one 1е reacts
with phenylhydrazine to form the corresponding indole 2e
in 51% yield.
performed on a HEKAtech Euro EA 3000 CHNS-analyzer.
Monitoring of the reaction progress and assessment of
the purity of synthesized compounds were done by gas-
liquid chromatography on a Khromos 1000 chromatograph,
1 m × 3 mm column, stationary phase SE-30 (5%) on
chromatone N-AW-DMCS (0.16–0.20 mm), 50–300°С,
flame ionization detector, helium carrier gas. Column
chromatography was performed on MN Kieselgel 60
(0.063–0.2 μm) silica gel.
The structure of 3H-indoles 2a–f and 1H-indole 3 was
established on the basis of spectral data. The formation of
the indolenine and indole rings is confirmed by the data of
IR and NMR spectroscopy. The IR spectra of indolenines
2a–f contain absorption bands in the 1579–1581 cm–1 range
which are characteristic of the ring C=N bond.25 The
spectrum of 3H-indole 2f also contains an intense
absorption band of the carbonyl group at 1709 cm–1. In the
1H NMR spectra of compounds 2a–f, in addition to the
signals of the protons of the aromatic ring, the
characteristic singlet signal of the protons of the 2-CH3
group (2.28–2.31 ppm), as well as two doublet signals of
the nonequivalent protons of the 1'-CH2 methylene group
in the ranges of 2.76–2.84 and 3.02–3.07 ppm are evident.
β-Mercapto ketones 1a,e–g were synthesized according
to published methods.21a,b Compounds 1b–d were obtained
according to a known procedure,21d with the difference that
the reaction of butan-2-one with formaldehyde and
alkanethiols was carried out with a 2:2:1 molar ratio of
1
reagents. IR and H NMR spectra of compound 1b are
identical to those reported previously.21e
3-Methyl-4-(propan-2-ylsulfanyl)butan-2-one (1с). Yield
4.3 g (89%), colorless oil. IR spectrum, ν, cm–1: 1712 (C=O).
1H NMR spectrum, δ, ppm (J, Hz): 1.19 (3H, d,3J = 7.0,
1
In the H NMR spectra of compounds 2a–d,f, a second
singlet signal of the 3-СH3 group protons is observed in the
1.36–1.38 ppm range. In the 13C NMR spectra, the carbon
atoms of the 2-СН3 and 3-СH3 groups correspond to
signals at 21.8 or 21.9, and 15.9–16.3 ppm, respectively.
In the 13С NMR spectrum of 3H-indole 2f, a doubling of
the signals of the carbon atoms of all substituents is
3
3-CH3); 1.25 (3H, d, J = 6.7, (CH3)2CH); 1.26 (3H, d,
3J = 6.7, (CH3)2CH); 2.19 (3H, s, 1-CH3); 2.51 (1H, dd,
2J = 12.6, 3J = 6.7, 4-СH2); 2.83 (1H, dd, 2J = 12.6, 3J = 7.0,
3
4-СH2); 2.73 (1H, sext, J = 7.0, 3-СH); 2.90 (1H, sept,
3J = 6.7, CH(CH3)2). 13C NMR spectrum, δ, ppm: 16.5
(3-CH3); 23.4 ((CH3)2CH); 28.7 (C-1); 32.9 (C-4); 35.6
(CH(CH3)2); 47.3 (C-3); 211.0 (С-2). Mass spectrum, m/z
(Irel, %): 161 [M+H]+ (100). Found, %: С 60.00; Н 10.11;
S 20.14. С8Н16OS. Calculated, %: С 59.95; Н 10.06; S 20.01.
4-(Hexylsulfanyl)-3-methylbutan-2-one (1d). Yield
5.3 g (87%), colorless oil. IR spectrum, ν, cm–1: 1713
1
observed, whereas in the H NMR spectrum a doubling of
the signals of the protons of the 3,4',6'-CH3 methyl groups
is apparent, which confirms the formation of a mixture of
(3R*,4'R*)- and (3R*,4'S*)-diastereomers.
In contrast to the IR spectra of 3H-indoles 2a–f, the IR
spectrum of 2,3-dimethyl-1H-indole 3 exhibits an intense
absorption band of the NH group at 3395 cm–1. In the
13C NMR spectrum, the signals of the 2-СH3 and 3-СH3
carbon atoms are predictably shifted upfield and are
observed at 8.4 and 11.6 ppm, respectively. IR spectrum,
1H and 13C NMR spectra of compound 3 are in good
agreement with published data.26
To conclude, novel 3H-indoles containing an alkyl-
sulfanylmethyl fragment at C-3 position were synthesized
based on the reaction of readily accessible 3-[(alkyl-
sulfanyl)methyl]alkan-2-ones with phenylhydrazine. The
synthesized compounds are of interest for studying their
biological activity and chemical properties. The yields of
the target indolenines decrease with an increase in the
length of the alkyl substituent in 4-(alkylsulfanyl)-
3-methylbutan-2-ones.
1
(C=O). H NMR spectrum, δ, ppm (J, Hz): 0.87 (3H, t,
3
3J = 7.0, 7'-СH3); 1.17 (3H, d, J = 6.9, 3-CH3); 1.22–1.32
3
(4H, m, 5',6'-СH2); 1.35 (2H, quint, J = 7.2, 4'-СH2); 1.55
3
(2H, quint, J = 7.2, 3'-СH2); 2.18 (3H, s, 1-СH3); 2.45–
2.51 (3H, m, 2'-СH2, 4-СH); 2.72 (1H, sext, 3J = 6.9, 3-СH);
2.79 (1H, dd, 2J = 12.5, 3J = 7.1, 4-СH). 13C NMR
spectrum, δ, ppm: 14.0 (C-7'); 16.5 (3-CH3); 22.5 (С-6');
28.7 (C-1); 28.5, 29.6, 31.4, 32.9, 34.7 (C-4,2'–5'); 47.2
(C-3); 211.0 (С-2). Mass spectrum, m/z (Irel, %): 203
[M+H]+ (100), 244 [M+H+MeCN]+ (3). Found, %:
С 65.32; Н 10.82; S 15.94. С11Н22OS. Calculated, %:
С 65.29; Н 10.96; S 15.85.
Synthesis of sulfanylmethyl-substituted 3-alkyl-
2-methyl-3H-indoles 2a–f (General method). A solution of
phenylhydrazine hydrochloride (0.29 g, 2 mmol) in MeOH
(EtOH for compound 1f) (8 ml) and ZnCl2 (0.055 g,
0.4 mmol) were added with stirring to a solution of
compound 1a–f (2 mmol) in MeOH (EtOH for compound
1f) (4 ml). The reaction mixture was heated under reflux
for 7–9 h, and the solvent was distilled off. The residue was
diluted with four volumes of H2O and extracted with
CH2Cl2. The combined extracts were washed successively
with H2O, 3% aqueous NaHCO3, H2O, and dried over
MgSO4. The solvent was distilled off, the residue was
chromatographed on a silica gel column (eluents PhH–
hexane, gradient from 1:2 to 1:0.5, PhH–hexane–EtOH,
1:0.5:0.3).
Experimental
IR spectra were registered on a Shimadzu JR Prestige-21
1
spectrometer with the sample as a thin film. H and 13C
NMR spectra were acquired on a Bruker Avance III 500 MHz
spectrometer (500 and 125 MHz, respectively) in СDСl3;
the residual solvent signals (7.27 ppm for 1Н nuclei, 77.1 ppm
for 13С nuclei). Assignments in the 13C NMR spectra were
made based on the spectra of analogous compounds.17
Mass spectra of compounds 2a–f, 3 were registered on a
Shimadzu LCMS-2010 EV chromato-mass spectrometer
with one quadrupole in the positive ion registration mode at
a capillary potential of 4.5 kV, electrospray ionization,
eluent MeCN–H2O, 95:5. Elemental analysis was
2,3-Dimethyl-3-[(methylsulfanyl)methyl]-3H-indole (2a).
Yield 0.38 g (92%), red-brown oil. IR spectrum, ν, cm–1:
545

Chemistry of Heterocyclic Compounds 2021, 57(5), 543–547
1579 (C=N). 1H NMR spectrum, δ, ppm (J, Hz): 0.59–0.69
and 0.75–0.84 (2H, m, CH2CH2CH3); 1.72–1.80 and 1.93–
2.03 (2H, m, CH2СH2CH3); 0.75 (3H, t, 3J = 6.8,
CH2CH2CH3); 1.81 (3H, s, CH3S); 2.26 (3H, s, 2-СH3);
1
1579 (C=N). H NMR spectrum, δ, ppm (J, Hz): 1.36 (3H,
s, 3-CH3); 1.83 (3H, s, SСH3); 2.28 (3H, s, 2-СH3); 2.79
2
2
(1H, d, J = 13.0, CH2S); 3.02 (1H, d, J = 13.0, CH2S);
7.19 (1H, t, 3J = 7.4, H-5); 7.32 (1H, t, 3J = 7.6, H-6); 7.37
(1H, d, 3J = 7.4, H-4); 7.54 (1H, d, 3J = 7.6, H-7). 13C NMR
spectrum, δ, ppm: 15.9 (2-CH3); 17.4 (СH3S); 21.8
(3-СH3); 41.1 (CH2S); 58.2 (С-3); 119.9, 121.9, 125.1,
128.2 (С-4–7); 142.9 (C-3a); 154.3 (C-7a); 185.5 (C-2).
Mass spectrum, m/z (Irel, %): 206 [M+H]+ (100), 247
2
2
2.80 (1H, d, J = 13.0, SСH2); 3.04 (1H, d, J = 13.0,
3
SСH2); 7.20 (1H, t, J = 7.6, H-5); 7.30–7.35 (2H, m,
3
H-4,6); 7.53 (1H, d, J = 7.6, H-7). 13C NMR spectrum,
δ, ppm: 14.2 (CH3(CH2)2); 16.3 (2-CH3); 17.5 (CH3S); 17.1
(CH2CH2CH3); 38.3 (CH2CH2CH3); 40.9 (CH2S); 62.9
(С-3); 119.9, 122.2, 125.1, 128.2 (С-4–7); 141.2 (C-3a);
155.2 (C-7a); 184.8 (C-2). Mass spectrum, m/z (Irel, %):
234 [M+H]+ (100), 275 [M+H+MeCN]+ (8). Found, %:
С 72.12; Н 8.15; N 5.90; S 13.82. С14Н19NS. Calculated,
%: С 72.05; Н 8.21; N 6.00; S 13.74.
1
[M+H+MeCN]+ (67). IR, H and 13C NMR spectra are in
good agreement with those published in the study.17
2,3-Dimethyl-3-[(propylsulfanyl)methyl]-3H-indole (2b).
Yield 0.40 g (86%), red-brown oil. IR spectrum, ν, cm–1:
1
1581 (C=N). H NMR spectrum, δ, ppm (J, Hz): 0.84 (3H,
t, 3J = 7.3, 5'-СH3); 1.37 (3H, s, 3-CH3); 1.38–1.48 (2H, m,
4'-СH2); 2.15–2.25 (2H, m, 3'-СH2); 2.29 (3H, s, 2-СH3);
(3R*,4'R*)- and (3R*,4'S*)-4-{[(2,3-Dimethyl-3H-indol-
3-yl)methyl]sulfanyl}-3-methylbutan-2-one (2f), dia-
stereomer ratio 1:1. Yield 0.09 g (17%), red-brown oil.
2
2
2.77 (1H, d, J = 12.9, 1'-СH2); 3.05 (1H, d, J = 12.9,
3
3
1
1'-СH2); 7.20 (1H, t, J = 7.4, H-5); 7.33 (1H, t, J = 7.7,
IR spectrum, ν, cm–1: 1709 (C=O), 1579 (C=N). H NMR
3
3
H-6); 7.38 (1H, d, J = 7.4, H-4); 7.54 (1H, d, J = 7.7,
H-7). 13C NMR spectrum, δ, ppm: 13.3 (C-5'); 16.0 (2-CH3);
21.9 (3-СH3); 22.8 (C-4'); 35.7 (C-3'); 38.7 (C-1'); 58.0
(С-3); 120.0, 121.9, 125.1, 128.2 (С-4–7); 143.0 (C-3a);
154.4 (C-7a); 185.6 (C-2). Mass spectrum, m/z (Irel, %):
234 [M+H]+ (100), 275 [M+H+MeCN]+ (4). Found, %:
С 72.46; Н 7.96; N 5.93; S 13.99. С14Н19NS. Calculated,
%: С 72.05; Н 8.21; N 6.00; S 13.74.
spectrum, δ, ppm (J, Hz): both isomers: 0.98 (1.5H, d,
3
3J = 7.1, 4'-CH3); 1.01 (1.5H, d, J = 6.9, 4'-CH3); 1.36
(3H, s, 2-CH3); 2.04 (1.5H, s, 6'-СH3); 2.05 (1.5H, s,
6'-СH3); 2.28 (1.5H, s, 3-СH3); 2.30 (1.5H, s, 3-СH3); 2.83
2
2
(0.5H, d, J = 13.0; 1'-CH2), 2.84 (0.5H, d, J = 13.0,
2
1'-CH2); 3.07 (1H, d, J = 13.0, 1'-CH2); 2.09–2.12, 2.22–
2.29, 2.38–2.50 and 2.55–2.58 (3H, m, 3'-CH2, 4'-CH);
7.17–7.23 (1H, m, H Ar); 7.30–7.38 (2H, m, H Ar); 7.55
3
(1H, d, J = 7.6, H Ar). 13C NMR spectrum, δ, ppm: 15.9,
2,3-Dimethyl-3-[(propan-2-ylsulfanyl)methyl]-3H-indole
(2c). Yield 0.30 g (64%), red-brown oil. IR spectrum, ν, cm–1:
15.9 (2-CH3); 16.2, 16.4 (4'-CH3); 21.0, 21.9 (3-СH3); 28.4,
28.8 (C-6'); 35.9, 36.1 and 39.5, 39.7 (C-1',3'); 47.2, 47.3
(C-4'); 58.2, 58.2 (С-3); 119.9, 121.9, 125.3, 128.3 (С-4–7);
142.6, 142.7 (C-3a); 153.9 (C-7a); 185.7 (C-2); 210.7,
210.7 (C-6'). Mass spectrum, m/z (Irel, %): 276 [M+H]+
(100), 317 [M+H+MeCN]+ (3). Found, %: С 69.58; Н 7.88;
N 5.10; S 11.86. С16Н21NOS. Calculated, %: С 69.78; Н
7.69; N 5.09; S 11.64.
1
1580 (C=N). H NMR spectrum, δ, ppm (J, Hz): 1.13 (3H,
3
3
d, J = 6.7, (CH3)2CH); 1.16 (3H, d, J = 6.7, (CH3)2CH);
1.38 (3H, s, 3-СH3); 2.31 (3H, s, 2-CH3); 2.58 (1H, sept,
2
3J = 6.7, CH(CH3)2); 2.76 (1H, d, J = 12.5, SСH2); 3.07
3
(1H, d, 2J = 12.5, SСH2); 7.20 (1H, t, J = 7.4, H-5); 7.33
(1H, t, 3J = 7.7, H-6); 7.38 (1H, d, 3J = 7.4, H-4); 7.54 (1H,
d, 3J = 7.7, H-7). 13C NMR spectrum, δ, ppm: 15.9
(2-CH3); 21.9 (3-СH3); 23.3 ((CH3)2CH); 36.1 (CH(CH3)2);
36.9 (CH2S); 57.6 (С-3); 119.9, 121.9, 125.1, 128.1 (С-4–7);
142.8 (C-3a); 154.3 (C-7a); 185.7 (C-2). Mass spectrum,
m/z (Irel, %): 234 [M+H]+ (100), 275 [M+H+MeCN]+ (18).
Found, %: С 72.09; Н 8.06; N 5.92; S 14.01. С14Н19NS.
Calculated, %: С 72.05; Н 8.21; N 6.00; S 13.74.
2,3-Dimethyl-1H-indole (3). Yield 0.09 g (31%), mp 101–
103°С (PhH–hexane–EtOH, 1:0.5:0.3) (mp 104–106°С26b).
IR spectrum, ν, cm–1: 3395 (NH), 1463, 1435, 737.
1H NMR spectrum, δ, ppm (J, Hz): 2.24 (3H, s, 2-CH3);
2.37 (3H, s, 3-CH3); 7.09 (1H, dt, 3J = 7.3, 4J = 1.2, H Ar);
3
4
3
7.10 (1H, dt, J = 7.5, J = 1.2, H Ar); 7.26 (1H, dd, J =
7.2, 4J = 1.3, H Ar); 7.48 (1H, d, 3J = 7.3, H Ar); 7.67 (1H,
br. s, NH). 13C NMR spectrum, δ, ppm: 8.4 (3-CH3); 11.6
(2-CH3); 107.1 (С-3); 109.9, 117.9, 119.0, 120.9 (С-4–7);
129.4 (C-3a); 130.6 (C-2); 135.2 (C-7а). Mass spectrum,
m/z (Irel, %): 146 [M+H]+ (100), 187 [M+H+MeCN]+ (19).
3-[(2-Hexylsulfanyl)methyl]-2,3-dimethyl-3H-indole
(2d). Yield 0.31 g (56%), red-brown oil. IR spectrum, ν, cm–1:
1
1581 (C=N). H NMR spectrum, δ, ppm (J, Hz): 0.85 (3H,
3
t, J = 7.0, 8'-СH3); 1.12–1.28 (6H, m, 5'–7'-СH2); 1.36
(3H, s, 2-CH3); 1.34–1.42 (2H, m, 4'-СH2); 2.15–2.28 (2H,
m, 3'-СH2); 2.29 (3H, s, 3-СH3); 2.77 (1H, d, J = 12.9,
IR, H and 13C NMR spectra are in good agreement with
2
1
2
1'-СH2); 3.04 (1H, d, J = 12.9, 1'-СH2); 7.19 (1H, t,
those published previously.26
3
3J = 7.4, H-5); 7.32 (1H, t, J = 7.7, H-6); 7.37 (1H, d,
3
3J = 7.4, H-4); 7.54 (1H, d, J = 7.7, H-7). 13C NMR
Spectral and analytical studies were carried out on the
equipment of the Collective Use Center ''Khimiya'', Ufa
Institute of Chemistry, Ufa Federal Research Center of the
Russian Academy of Sciences.
spectrum, δ, ppm: 13.9 (С-8'); 15.9 (2-CH3); 21.8 (3-СH3);
22.4 (C-7'); 28.3, 29.4, 31.3, 33.6 (C-3'–6'); 38.7 (C-1');
58.0 (С-3); 119.9, 121.9, 125.1, 128.1 (С-4–7); 142.9 (C-3a);
154.3 (C-7a); 185.6 (C-2). Mass spectrum, m/z (Irel, %):
276 [M+H]+ (100), 317 [M+H+MeCN]+ (26). Found, %:
С 74.17; Н 8.98; N 5.11; S 11.68. С17Н25NS. Calculated,
%: С 74.13; Н 9.15; N 5.08; S 11.64.
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2-Methyl-3-[(methylsulfanyl)methyl]-3-propyl-3H-indole
(2e). Yield 0.24 g (51%), red-brown oil. IR spectrum, ν, cm–1:
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