1-Imidoyl-1,2,3-benzotriazoles—Novel Reagents for the Synthesis of 1-Aryl-5-trifluoromethylimidazoles

Article abstract of DOI:10.1134/S1070428019040122

1-Imidoylbenzotriazoles [N-aryl-1-(1H-benzotriazol-1-yl)-2,2,2-trifluoroethan-1-imines] reacted with tosylmethyl isocyanide according to van Leusen’s procedure to give difficultly accessible 1-aryl-4-(4-methylbenzenesulfonyl)-5-(trifluoromethyl)-1H-imidaz

Full text of DOI:10.1134/S1070428019040122

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2019, Vol. 55, No. 4, pp. 493–497. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Organicheskoi Khimii, 2019, Vol. 55, No. 4, pp. 591–595.
1-Imidoyl-1,2,3-benzotriazoles—Novel Reagents for the Synthesis
of 1-Aryl-5-trifluoromethylimidazoles
A. S. Buneva,* E. V. Varakinaa, D. A. Khochenkova, b, and A. S. Peregudovc
a Togliatti State University, Togliatti, Russia
*e-mail: a.s.bunev@gmail.com
b Blokhin National Medical Research Center of Oncology, Moscow, Russia
c Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia
Received November 14, 2018; revised November 18, 2018; accepted December 9, 2018
Abstract—1-Imidoylbenzotriazoles [N-aryl-1-(1H-benzotriazol-1-yl)-2,2,2-trifluoroethan-1-imines] reacted
with tosylmethyl isocyanide according to van Leusen’s procedure to give difficultly accessible 1-aryl-4-(4-
methylbenzenesulfonyl)-5-(trifluoromethyl)-1H-imidazoles in good yields (81–94%). The initial imidoylbenzo-
triazoles were conveniently synthesized by reaction of sodium benzotriazolide with the corresponding imidoyl
chlorides in THF. The reactions were carried out with a wide series of imidoylbenzotriazoles containing various
electron-donating and electron-withdrawing substituents in the N-aryl fragment.
Keywords: imidazoles, van Leusen reaction, isocyanides, trifluoromethyl-substituted azoles, benzotriazole.
DOI: 10.1134/S1070428019040122
Organofluorine compounds, including fluorine-con-
taining heterocycles, are very attractive substrates from
both theoretical and practical viewpoints [1]. In recent
years, fluorinated heterocycles have attracted particular
attention of researchers in the field of medicinal and
bioorganic chemistry. This is related to unique prop-
erties of organofluorine compounds and their very high
physiological activity [2].
We previously described a procedure for the syn-
thesis of difficultly accessible 5-trifluoromethylimid-
azoles by the van Leusen reaction of imidoyl chlorides
with tosylmethyl isocyanide (TosMIC) in the presence
of sodium hydride [8]. This procedure, as well as clas-
sical methods [8–14] of synthesis of fluoroalkylimid-
azoles, made it possible to obtain 1,4,5-trisubstituted
imidazoles in moderate yields.
Introduction of fluorine atoms or fluorine-contain-
ing substituents into organic molecules often dramati-
cally changes their chemical and pharmaceutical
properties [3]. In this way, a large number of fluorine-
containing drugs have been created, including anti-
tumor agents with different mechanisms of action
(fulvestrant, nilotinib, capecitabine), CNS drugs
(escitalopram, rufinamide, ioflupane), and cardio-
vascular drugs (ezetimibe, nebivolol, prasugrel) [4–7].
In continuation of our studies aimed at synthesizing
low-molecular-weight imidazole derivatives, in this
work we examined the possibility of using 1-imidoyl-
benzotriazoles as N1–C5 synthons in the synthesis of
imidazoles by the van Leusen reaction with TosMIC.
We tried to obtain initial imidoylbenzotriazoles 2
according to the known procedures involving treatment
of substituted acetanilides with benzotriazole and
phosphoryl chloride [15] or with 1-chlorobenzotriazole
Scheme 1.
N
N
POCl3, Et3N, MeCN (X = H)
or Ph3P, THF, reflux (X = Cl)
O
N
N
N
+
N
Ar
Ar
N
CF3
H
N
F3C
X
2
493

BUNEV et al.
494
Scheme 2.
Ts
TosMIC, NaH
THF, r.t., 1 h
Ar
Cl
N
N
N
N
NaH, THF, r.t.
+
N
2a–2k
N
H
F3C
F3C
1a–1k
Ar
3a–3k
1–3, Ar = Ph (a), 2-MeC6H4 (b), 4-MeC6H4 (c), 2,4-MeC6H3 (d), 4-MeOC6H4 (e), 4-CF3C6H4 (f), 4-FC6H4 (g),
2-ClC6H4 (h), 4-ClC6H4 (i), 4-BrC6H4 (j), 4-O2NC6H4 (k).
Scheme 3.
CF3
Bt
F3C
Ts
H–
2
Ts
Ar
Ar
3
Ts
NC
Ts
NC
N
H
N
–H2
–Bt–
NC
N
:
C
A
B
C
Bt = 1H-benzotriazol-1-yl.
and triphenylphosphine [16]. However, trifluoroacet-
anilides failed to react under these conditions and were
recovered from the reaction mixtures (Scheme 1).
methyl-substituted imidazoles by reaction with tosyl-
methyl isocyanide. Taking into account synthetic
accessibility of initial imidoyl chlorides and isocy-
anides, the proposed procedure makes it possible to
obtain a variety of polysubstituted imidazoles con-
taining pharmacophoric groups.
We succeeded in synthesizing required compounds
2 by direct reaction of sodium benzotriazolide with
imidoyl chlorides 1a–1k in THF. According to the
TLC data, the reaction was complete in 1.5–2 h.
Taking into account that further transformation of 2a–
2k is accomplished in the same solvent, we were able
to obtain imidazoles 3a–3k in a one-pot process by
subsequent treatment of the resulting solution of 2a–2k
with TosMIC and sodium hydride. Imidazoles 3a–3k
were thus isolated in 81–94% yield (Scheme 2). The
yield of 3 almost did not depend on the substituent in
the N-aryl fragment of initial imidoylbenzotriazole 2.
EXPERIMENTAL
The IR spectra were recorded in KBr on an FSM-
1
1201 spectrometer. The H, 13C, and 19F NMR spectra
were recorded on a Bruker Avance 600 instrument at
600, 150, and 377 MHz, respectively using DMSO-d6
as solvent and tetramethylsilane (1H, 13C) or CFCl3
(19F) as internal standard. The elemental compositions
were determined with a Vario El Cube analyzer. The
melting points were measured on a Boetius hot stage
and are uncorrected.
A probable reaction mechanism includes the fol-
lowing stages. Initially, deprotonation of TosMIC with
sodium hydride generates stabilized carbanion A
which attacks the C=N carbon atom of 2 to give
intermediate adduct B. Elimination of benzotriazolide
ion from the latter yields intermediate C which under-
goes intramolecular cyclization leading to imidazole 3
(Scheme 3).
1-Aryl-4-(4-methylbenzenesulfonyl)-5-(trifluoro-
methyl)-1H-imidazoles 3a–3k (general procedure).
Benzotriazole, 5 mmol, was added to a suspension of
5.5 mmol of sodium hydride in 30 mL of THF. The
mixture was stirred until hydrogen no longer evolved
(~15 min), and a solution of imidoyl chloride 1a–1k in
5 mL of THF was added dropwise. The mixture was
stirred and left to stand for 1.5 h to complete the
reaction (TLC, ethyl acetate–hexane, 1:9). A solution
of 5 mmol of TosMIC in 10 mL of THF was added,
and 5.5 mmol of sodium hydride was then added in
portions over a period of 5–10 min. The mixture was
stirred for 1 h and carefully treated with ice water
(200 mL). The precipitate was filtered off, dried, and
recrystallized from toluene–hexane (9:1).
1
The H NMR spectra of 3a–3k characteristically
showed a singlet of the 2-H proton of the imidazole
ring at δ 8.20–8.41 ppm, as well as other signals. In
the 19F NMR spectra of 3a–3k, fluorine atoms of
the 5-trifluoromethyl group resonated in the region
δF –53.64 to –51.81 ppm; the spectra of 3f and 3g
contained additional singlets at δF –61.34 (4-CF3C6H4)
and –110.57 ppm (4-FC6H4), respectively.
Thus, trifluoroacetimidoylbenzotriazoles are
convenient reagents for the synthesis of 5-trifluoro-
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1-IMIDOYL-1,2,3-BENZOTRIAZOLES
495
4-(4-Methylbenzenesulfonyl)-1-phenyl-5-(tri-
fluoromethyl)-1H-imidazole (3a). Yield 1.63 g
(89%), beige powder, mp 201–203°C. IR spectrum, ν,
cm–1: 3106, 1584, 1498, 1385, 1335, 1190, 1150, 680,
593. H NMR spectrum, δ, ppm: 2.42 s (3H, CH3),
7.49 d (2H, Harom, J = 8.1 Hz), 7.53–7.64 m (5H,
8.29 s (1H, 2-H). 13C NMR spectrum, δC, ppm: 19.0
(CH3), 21.6 (CH3), 21.6 (CH3), 127.1, 128.7, 129.9,
130.5, 130.8, 134.9, 137.1, 142.2, 145.5. 19F NMR
spectrum: δF –53.32 ppm. Found, %: C 57.73; H 4.39;
N 7.22. C19H17F3N2O2S. Calculated, %: C 57.86;
H 4.34; N 7.07.
1
H
arom), 7.87 d (2H, Harom, J = 8.0 Hz), 8.28 s (1H, 2-H).
1-(4-Methoxyphenyl)-4-(4-methylbenzenesul-
fonyl)-5-(trifluoromethyl)-1H-imidazole (3e). Yield
1.64 g (83%), beige powder, mp 201–202°C. IR spec-
trum, ν, cm–1: 3110, 1586, 1502, 1336, 1261, 1185,
13C NMR spectrum, δC, ppm: 21.6 (CH3), 118.7, 120.4,
121.3, 121.5, 127.1, 128.6, 128.77, 129.9, 130.4,
130.6, 130.8, 134.9, 137.1, 142.2, 143.4, 145.5.
19F NMR spectrum: δF –52.15 ppm. Found, %:
C 55.56; H 3.67; N 7.60. C17H13F3N2O2S. Calculated,
%: C 55.73; H 3.58; N 7.65.
1
1154, 1008, 682, 584. H NMR spectrum, δ, ppm:
2.42 s (3H, CH3), 3.82 (3H, OCH3), 7.07–7.11 m (2H,
Harom), 7.50 d.d (4H, Harom, J = 8.4, 5.8 Hz), 7.86 d
(2H, Harom, J = 8.3 Hz), 8.20 s (1H, 2-H). 13C NMR
spectrum, δC, ppm: 21.6 (CH3), 56.1 (OCH3), 114.9,
121.7, 127.4, 128.5, 128.6, 130.4, 137.2, 142.3, 143.2,
145.4, 160.83. 19F NMR spectrum: δF –52.28 ppm.
Found, %: C 54.43; H 3.85; N 7.21. C18H15F3N2O3S.
Calculated, %: C 54.54; H 3.81; N 7.07.
4-(4-Methylbenzenesulfonyl)-1-(2-methyl-
phenyl)-5-(trifluoromethyl)-1H-imidazole (3b).
Yield 1.69 g (89%), beige powder, mp 179–180°C. IR
spectrum, ν, cm–1: 3105, 1593, 1495, 1335, 1181,
1151, 771, 661, 594. 1H NMR spectrum, δ, ppm: 1.97 s
(3H, CH3), 2.42 s (3H, CH3), 7.41–7.35 m (1H, Harom),
7.46 d (1H, Harom, J = 7.0 Hz), 7.51 t.d (4H, Harom, J =
5.5, 2.8 Hz), 7.88 d (2H, Harom, J = 8.3 Hz), 8.26 s (1H,
2-H). 13C NMR spectrum, δC, ppm: 16.8 (CH3), 21.6
(CH3), 127.5, 128.2, 128.6, 130.5, 131.2, 131.4, 134.0,
135.2, 137.1, 142.2, 143.3, 145.5. 19F NMR spec-
trum: δF –53.47 ppm. Found, %: C 56.74; H 4.06;
N 7.23. C18H15F3N2O2S. Calculated, %: C 56.84;
H 3.97; N 7.36.
4-(4-Methylbenzenesulfonyl)-5-(trifluoro-
methyl)-1-[4-(trifluoromethyl)phenyl]-1H-imidazole
(3f). Yield 2.04 g (94%), brown powder, mp 149–
150°C. IR spectrum, ν, cm–1: 3106, 1598, 1497, 1341,
1179, 1155, 773, 666, 591. 1H NMR spectrum, δ, ppm:
2.42 s (3H, CH3), 7.50 d (2H, Harom, J = 8.2 Hz), 7.89 d
(4H, Harom, J = 8.2 Hz), 7.99 d (2H, Harom, J = 8.4 Hz),
8.34 s (1H, 2-H). 13C NMR spectrum, δC, ppm: 21.6
(CH3), 127.2, 128.4, 128.6, 130.5, 137.1, 138.4, 142.2;
143.7, 145.6. 19F NMR spectrum, δF, ppm: –51.96
(5-CF3), –61.34 (4′-CF3). Found, %: C 49.66; H 2.87;
N 6.50. C18H12F6N2O2S. Calculated, %: C 49.77;
H 2.78; N 6.45.
4-(4-Methylbenzenesulfonyl)-1-(4-methyl-
phenyl)-5-(trifluoromethyl)-1H-imidazole (3c).
Yield 1.64 g (86%), beige powder, mp 159–161°C. IR
spectrum, ν, cm–1: 3104, 1594, 1516, 1472, 1337,
1
1191, 1152, 1006, 683, 593. H NMR spectrum, δ,
ppm: 2.37 s (3H, CH3), 2.41 s (3H, CH3), 7.36 d (2H,
1-(4-Fluorophenyl)-4-(4-methylbenzenesulfonyl)-
5-(trifluoromethyl)-1H-imidazole (3g). Yield 1.65 g
(86%), beige powder, mp 164–166°C. IR spectrum, ν,
cm–1: 3108, 1598, 1488, 1336, 1187, 1152, 1018, 677,
596. H NMR spectrum, δ, ppm: 2.42 s (3H, CH3),
7.40–7.47 m (2H, Harom), 7.50 d (2H, Harom, J =
H
arom, J = 8.2 Hz), 7.45 d (2H, Harom, J = 8.3 Hz),
7.48 d (2H, Harom, J = 8.2 Hz); 7.88 d (2H, Harom
,
J = 8.2 Hz), 8.24 s (1H, 2-H). 13C NMR spectrum,
δC, ppm: 21.1 (CH3), 21.6 (CH3), 118.7, 120.5,
121.3, 126.8, 128.0, 128.6, 129.1, 129.8, 130.3, 130.9,
132.4, 137.2, 143.4, 145.5. 19F NMR spectrum:
δF –52.25 ppm. Found, %: C 56.75; H 4.03;
N 7.31. C18H15F3N2O2S. Calculated, %: C 56.84;
H 3.97; N 7.36.
1
8.1 Hz), 7.67–7.74 m (2H, Harom), 7.87 d (2H, Harom
,
J = 8.3 Hz), 8.26 s (1H, 2-H). 13C NMR spectrum, δC,
ppm: 21.6 (CH3), 116.7, 128.6, 129.7, 130.4, 131.2;
137.1, 142.3, 143.3, 145.5. 19F NMR spectrum, δF,
ppm: –52.21 (5-CF3), –110.57 (4′-F). Found, %:
C 53.01; H 3.27; N 7.22. C17H12F4N2O2S. Calculated,
%: C 53.13; H 3.15; N 7.29.
1-(2,4-Dimethylphenyl)-4-(4-methylbenzenesul-
fonyl)-5-(trifluoromethyl)-1H-imidazole (3d). Yield
1.76 g (89%), beige powder, mp 177–179°C. IR spec-
trum, ν, cm–1: 3111, 1596, 1336, 1261, 1185, 1154,
1008, 813, 682, 594. 1H NMR spectrum, δ, ppm: 2.40 s
(3H, CH3), 2.42 s (3H, CH3), 2.43 s (3H, CH3), 7.36 s
(1H, Harom), 7.50 d (2H, Harom, J = 8.1 Hz), 7.57–
7.60 m (2H, Harom), 7.88 d (2H, Harom, J = 7.4 Hz),
1-(2-Chlorophenyl)-4-(4-methylbenzenesul-
fonyl)-5-(trifluoromethyl)-1H-imidazole (3h). Yield
1.66 g (83%), beige powder, mp 198–200°C. IR spec-
trum, ν, cm–1: 3107, 1593, 1490, 1335, 1180, 1153,
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BUNEV et al.
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1
1008, 676, 594. H NMR spectrum, δ, ppm: 2.42 s
(3H, CH3), 7.51 d (2H, Harom, J = 8.1 Hz), 7.57 t.d (1H,
Harom, J = 7.7, 1.4 Hz), 7.66 t.d (1H, Harom, J = 7.7,
1.4 Hz), 7.77 d.d (1H, Harom, J = 8.1, 1.4 Hz), 7.85 d.d
(1H, Harom, J = 7.9, 1.6 Hz), 7.88 d (2H, Harom, J =
8.3 Hz), 8.35 s (1H, 2-H). 13C NMR spectrum, δC,
ppm: 21.6 (CH3), 118.5, 120.3, 122.1, 128.6, 128.9,
131.3, 132.5, 133.0, 137.0, 142.4, 143.3, 145.6.
19F NMR spectrum: δF –53.64 ppm. Found, %:
C 51.08; H 3.07; N 6.91. C17H12ClF3N2O2S. Calculat-
ed, %: C 50.94; H 3.02; N 6.99.
Found, %: C 49.55; H 3.03; N 10.08. C17H12F3N3O4S.
Calculated, %: C 49.64; H 2.94; N 10.22.
FUNDING
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 16-33-00349 mol_a).
CONFLICT OF INTERESTS
The authors declare the absence of conflict of
interests.
1-(4-Chlorophenyl)-4-(4-methylbenzenesul-
fonyl)-5-(trifluoromethyl)-1H-imidazole (3i). Yield
1.78 g (89%), beige powder, mp 201–202°C. IR spec-
trum, ν, cm–1: 3107, 1594, 1499, 1336, 1190, 1151,
1022, 839, 664, 593. 1H NMR spectrum, δ, ppm: 2.41 s
(3H, CH3), 7.49 d (2H, Harom, J = 8.1 Hz), 7.65–7.68 m
(4H, Harom), 7.87 d (2H, Harom, J = 8.2 Hz), 8.28 s
(1H, 2-H). 13C NMR spectrum, δC, ppm: 21.6 (CH3),
118.6, 121.4, 121.7, 128.6, 129.2, 129.3, 129.9, 130.4,
133.8, 135.6, 137.1, 142.2, 143.5, 145.5. 19F NMR
spectrum: δF –52.12 ppm. Found, %: C 50.75; H 3.09;
N 6.86. C17H12ClF3N2O2S. Calculated, %: C 50.94;
H 3.02; N 6.99.
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4-(4-Methylbenzenesulfonyl)-1-(4-nitrophenyl)-
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1
592, 534. H NMR spectrum, δ, ppm: 2.42 (3H, CH3),
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