Regioselective, Solvent- and Metal-Free Chalcogenation of Imidazo[1,2-a]pyridines by Employing I2/DMSO as the Catalytic Oxidation System

Article abstract of DOI:10.1002/chem.201600800

Highly efficient molecular-iodine-catalyzed chalcogenations (S and Se) of imidazo[1,2-a]pyridines were achieved by using diorganoyl dichalcogenides under solvent-free conditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed the preparation of different types of chalcogenated imidazo[1,2-a]pyridines with structural diversity. Furthermore, the current protocol was also extended to other N-heterocyclic cores.

Full text of DOI:10.1002/chem.201600800

DOI: 10.1002/chem.201600800
Full Paper
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Green Chemistry |Hot Paper|
Regioselective, Solvent- and Metal-Free Chalcogenation of
Imidazo[1,2-a]pyridines by Employing I2/DMSO as Catalytic
Oxidation System
Jamal Rafique, Sumbal Saba, Alisson R. Rosꢀrio, and Antonio L. Braga*[a]
In memory of Dr. Syed H. Hussain who was killed by terrorists while protecting his students
Abstract: Highly efficient molecular-iodine-catalyzed chalco-
genations (S and Se) of imidazo[1,2-a]pyridines were ach-
ieved by using diorganoyl dichalcogenides under solvent-
free conditions. This approach afforded the desired products
that had been chalcogenated regioselectively at the C3 posi-
tion in up to 96% yield by using DMSO as an oxidant, in the
absence of a metal catalyst, and under an inert atmosphere.
This mild, green approach allowed the preparation of differ-
ent types of chalcogenated imidazo[1,2-a]pyridines with
structural diversity. Furthermore, the current protocol was
also extended to other N-heterocyclic cores.
Introduction
which is mainly due to their antioxidant, antitumor, anti-inflam-
matory, and antiviral activities.[5,6] In addition, these scaffolds
are present in a wide range of molecules that have important
applications in material sciences,[7] and they also play a funda-
mental role in modern organic synthesis and catalysis.[8,9] As
a consequence, important advances are being made in the se-
lective CÀS/Se bond formation, and direct chalcogenation (S/
Se) is an attractive approach.[5,8–10]
The imidazo[1,2-a]pyridine (IP) core, found in many bioactive
natural products and pharmaceuticals, represents an important
“privileged scaffold”.[1] Several commercially available drugs
have the IP moiety in their core structure, e.g., alpidem, neco-
pidem, saripidem (as anxiolytics), zolpidem (as a sedative), mir-
oprofen (as an analgesic), and zolimidine (for the treatment of
peptic ulcer) (Figure 1).[1a,2] Additionally, IP derivatives are
We have considered the biological relevance of organochalc-
ogen compounds and the wide spectrum of therapeutic prop-
erties of IPs; however, few synthetic methods for the construc-
tion of 3-sulfenyl-imidazo[1,2-a]pyridines have been reported
in the literature,[11] and even fewer studies have been carried
out on the selenium counterpart.[11i,12] Furthermore, some of
the methods suffer from limitations, such as the use of non-
green solvents and prefunctionalized coupling partners, low
atom economy, poor substrate scope, the requirement of
metal catalysts, ligands, and bases, sensitivity to atmosphere,
harsh reaction conditions, or elaborate multistep processes,
and these issues reduce their synthetic utility.
Figure 1. Imidazo[1,2-a]pyridine-based drug compounds.
useful in the field of optoelectronics and material sciences as
charge transporters.[3] Therefore, the synthesis and functionali-
zation of IPs has received considerable attention.[1a,4]
In recent decades, the biological and medicinal properties of
organochalcogenides (S, Se) have gained increasing interest,[5]
In recent years, the I2/DMSO oxidative system has been suc-
cessfully applied in various types of organic transformations.[13]
In this context, it would be advantageous and highly desirable
to develop a ligand- and metal-free protocol that involves a sol-
vent-free system for the preparation of chalcogenated IPs,
which is applicable to various sources of stable organochalco-
gens. Thus, in relation to our continuing interest in the chalco-
genation of heteroarenes and organochalcogen chemistry as
well as the design of eco-friendly processes,[10a–c,14] we now
report, for the first time, the use of the I2/DMSO oxidant
system in the chalcogenation (S, Se) of IPs at the C3 position.
This new regioselective, scalable, and metal-free protocol pro-
ceeded smoothly with a half molar equivalent of different di-
chalcogenides and without the exclusion of air or moisture.
[a] Dr. J. Rafique, Dr. S. Saba, Dr. A. R. Rosꢀrio, Prof. Dr. A. L. Braga
Departamento de Quꢁmica
Universidade Federal de Santa Catarina
Florianopolis, 88040-900 (Brazil)
E-mail: braga.antonio@ufsc.br
Homepage: http://labselen.ufsc.com/
Supporting information and ORCID numbers from the authors for this arti-
cle are available on the WWW under
http://dx.doi.org/10.1002/chem.201600800.
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Results and Discussion
Table 1. Optimization of the reaction conditions.[a]
For the optimization of the selenylation reaction, 7-methyl-2-
phenylimidazo[1,2-a]pyridine (1a) and diphenyl diselenide (2a)
were selected as model substrates, and these were evaluated
under various conditions (Table 1). The reaction was successful
with I2 (20 mol%) in the presence of 5 molar equivalents of
DMSO (0.089 mL) at 1108C for 18 h; this afforded the desired
product 3a in 69% yield (entry 1). There was no improvement
in the yield when the reaction was conducted under inert at-
mosphere (entry 2), which shows that the reaction can be per-
formed without the exclusion of air. The ideal reaction temper-
ature was found to be 908C (entries 3–5). In relation to the
source of iodine in the reaction system, a negative effect was
observed when NaI and KI were used instead of I2, and this re-
sulted in 50 and 54% yields of the selenated product 3a, re-
spectively (entries 6 and 7). Lowering the catalyst loading to 5
and 2.5 mol% led to the desired product 3a in lower yields
(entries 9 and 10). The ideal reaction time was examined for
this transformation and found to be 9 h (entries 11–13).
Entry
Catalyst [mol%] Oxidant [equiv] T [8C] t [h] Yield [%][b]
1
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
NaI (20)
KI (20)
I2 (10)
I2 (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
H2O2 (5)
110
110
100
90
80
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
18
18
18
18
18
18
18
18
18
18
12
9
69
67
83
87
78
50
54
87
86
56
88
90
60
57
12
91
89
77
44
–
2[c]
3
4
5
6
7
8
9
10
11
12
13
14
15
16[d]
17
18
19
20
I2 (2.5)
I2 (5)
I2 (5)
I2 (5)
6
I2 (5)
9
I2 (5)
I2 (5)
TBHP (5)
DMSO
9
9
I2 (5)
I2 (5)
I2 (5)
DMSO (3)
DMSO (2)
DMSO (1)
DMSO (1)
9
9
9
9
With regard to the influence of the oxidant on the selenyla-
tion of substrate 1a, we found that the use of H2O2 or TBHP in-
stead of DMSO resulted in a less efficient transformation
(Table 1, entries 14–19). The use of DMSO (3 mL) as the solvent
did not provide any further positive influence on the yield of
3a (entry 16 vs. 12). Similarly, upon decreasing the amount of
DMSO from 5 to 3 molar equivalents, we obtained the product
3a in 89% yield (entry 17), whereas a further decrease in
DMSO afforded a lower yield of 3a (entries 18–19).
–
[a] Reaction conditions: 1a (0.25 mmol), 2a (0.125 mmol), catalyst
(mol%), oxidant (molar equiv). [b] Yield of isolated poduct. [c] Reaction
under argon atmosphere. [d] 2 mL DMSO.
With the optimized reaction conditions in hand (Table 1,
entry 17), we explored the generality and scope of
this method, and the reaction demonstrated wide
substrate scope in terms of the diorganyl diselenide
Table 2. Scope of diorganyl diselenide 2.[a,b]
substrates 2 (Table 2). Various diaryl diselenides with
electron-donating (R=Me, OMe), electron-withdraw-
ing (R=F, Cl, CF3), and sterically bulky substituents
(R=naphthyl) successfully reacted to afford the cor-
responding products in good to excellent yields (3a–
i, 71–93%). We also observed that the C-2 heteroaryl
diselenide gave the desired selenide 3j in a similar
high yield (82%). In general, electron-withdrawing
groups afforded the best results (3a–e vs. f–g). Fur-
thermore, steric hindrance of the ortho-substituent
on the aryl unit of the diselenide substrate showed
an unfavorable influence on the yields compared
with the para-substituted counterparts (3b–c vs. d–
e). However, a sterically bulkier aryl moiety on the
diselenide substrate (R=1-naphthyl) afforded the de-
sired product 3i in 71% yield. Finally, considering the
importance of butylated organoselenides in cross-
coupling reactions,[15] we were successful in using di-
butyl diselenide 2k to produce the corresponding
product 3k in good yield.
The success in the iodine-catalyzed CÀSe bond for-
mation, through the C(sp2)ÀH bond activation of
biaryl substrate 1a, prompted us to expand this
method by using diorganyl disulfide substrates 4a–
[a] Reaction conditions: 1a (0.25 mmol), 2 (0.125 mmol), I2 (5 mol%), DMSO (3 molar
equiv, 0.054 mL), 908C, 9 h. [b] Yield of isolated product.
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products 8a–i and aa–ai were successfully obtained
in 79–96% yield. In general, disulfide 4a afforded
the coupled products in better yields compared with
the diselenide 2a. IP substrates with substituents at
C-6 or C-7, or without functionalization (at the pyri-
dine ring) did not show any significant effects to-
wards the yield. The system also tolerated changes
in the electronic nature of the C-2 substituents of
the phenyl group of the IP substrate; in this case,
electron-withdrawing groups (Br, Cl, F, CN) showed
superiority over an electron-donating group (OMe).
Additionally, we extended the method to imida-
zo[1,2-a]pyrimidine, which furnished the correspond-
ing chalcogenated products 8h and ah in good
yields. Notably, the method showed high regioselec-
tivity because the IP substrate that had no substitu-
ent at the C-2 position was selectively chalcogenated
at C-3 to exclusively give products 8i and ai in 85
and 91% yield, respectively.
Table 3. Scope of diorganyl disulfides 5.[a,b]
To demonstrate the synthetic utility of this new
protocol, a series of reactions were carried out on
different scales in a normal laboratory setup. Imida-
zo[1,2-a]pyridine 1a efficiently reacted with diphenyl
[a] Reaction conditions: 1a (0.25 mmol), 4 (0.125 mmol), I2 (5 mol%), DMSO (3 molar
equiv, 0.054 mL), 908C, 9 h. [b] Yield of isolated product.
i as the coupling partner (Table 3). Accordingly, the thiolation
of biaryl 1a under the optimized reaction conditions that had
been determined for selenylation afforded the corresponding
sulfenylated products 5a–j in 58 to 95% yield. The sulfenyla-
tion of IP was governed by similar electronic and steric effects
that were observed in the selenylation reaction; furthermore,
diorganyl disulfides 4 afforded the coupling products in better
yields than the corresponding diorganyl diselenides 2.
Table 4. Scope of imidazo[1,2-a]pyridines 1.[a,b]
Other thiolating agents were tested under the optimized re-
action conditions (Scheme 1). The reaction of thiols 6 proceed-
[a] Reaction conditions: 1a (0.25 mmol), 2a or 4a (0.125 mmol), I2
(5 mol%), DMSO (3 molar equiv, 0.054 mL), 908C, 9 h. [b] Yield of isolated
product.
Scheme 1. Thiolation by using other sulfenylating agents.
ed smoothly, and the corresponding coupled products 5a and
k were isolated in 80 and 54% yield, respectively (Scheme 1a).
Similarly, when aryl sulfonyl hydrazide (7) was employed as the
substrate, we obtained the desired products 5a and b in 84
and 81% yield, respectively (Scheme 1b). However, the use of
dichalcogenides as chalcogenylating agents appears to be
a better synthetic option as they are odorless and inexpensive.
The reaction scope was further tested by using different IP
cores 1 with diselenide 2a and disulfide 4a under the opti-
mized conditions (Table 4). The corresponding chalcogenated
diselenide 2a under the optimized conditions up to a 10 mmol
scale, which afforded product 3a with no major decrease in
yield (Figure 2). Therefore, this protocol represents a practical
method for the synthesis of biologically relevant lead com-
pounds.
Other N-heterocyclic cores were tested under the optimized
conditions. Indazole 9a furnished the corresponding C-3-sele-
nylated products 10a–c in good yields (Table 5, entries 1–3).
On the other hand, 2-aryl 1,3,4-oxadiazole 9b and benzothia-
zole 9c afforded the corresponding selenylated and sulfenylat-
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These results indicate that scavenging the generated
HI terminates the catalytic cycle by inhibiting the
DMSO activation. To exclude the unusual formation
of CÀI and CÀS bonds with imidazo[1,2-a]-pyri-
dines,[16] we carried out an experiment without di-
phenyl diselenide (2a). Interestingly, we did not ob-
serve these unusual products; we believe that this is
the consequence of a low concentration of iodine
and DMSO (Scheme 2e).
Table 5. Scope of N-heterocyclic core 9.[a]
Entry N-Heterocyclic core 9 Product 10–14
Yield [%][b]
81
1
2
3
Ar=Ph, Y=Se, 10a
Ar=4-MeOPh, Y=Se 10b 79
Ar=4-ClPh, Y=Se, 10c
85
Based on the above results and on previous re-
ports,[10a–b,11] a possible mechanism has been pro-
posed with model substrates 1i and 2a (Scheme 3).
An electrophilic species A (PhSeI) is most likely gen-
erated when the diphenyl diselenide (2a) is submit-
ted to reaction with the catalyst (I2). Next, the reac-
tive intermediate A reacts regioselectively with imi-
dazo[1,2-a]pyridine (1i) at the C-3 position to form
species B. This species can undergo proton elimina-
tion to afford the desired selenylated product 8i,
with the concomitant formation of HI. Two molar
equivalents of HI react with DMSO to afford the pro-
tonated sulfur species C, which with the elimination
of water, results in the formation of iodine–dimethyl
sulfide intermediate D.[17] Finally, the iodide species
4
5
Ar=Ph, Y=Se, 11 a
Ar=Ph, Y=S, 11 b
39
33
6
7
Ar=Ph, Y=Se, 12a
Ar=Ph, Y=S, 12b
22
19
8
9
13
14
–
–
[a] Reaction conditions: 9 (0.25 mmol), 2 or 4 (0.125 mmol), I2 (5 mol%), DMSO (3
molar equiv, 0.054 mL), 908C, 9 h. [b] Yield of isolated product.
D eliminates Me2S, which regenerates the catalyst in the reac-
Figure 2. Results for the reaction on different scales.
ed products in low yields (entries 4–7), and benzoxazole 9d
and benzimidazole 9e did not react under these conditions
(entries 8–9).
To elucidate the mechanism, we performed some control ex-
periments (Scheme 2). Firstly, addition of a radical inhibitor
(TEMPO) did not hamper the reaction, and the desired seleny-
lated product 3a was obtained in 81% yield (Scheme 2a); this
excluded the possibility of a radical pathway. Secondly, when
biaryl 1a was treated with PhSeBr instead of diphenyl disele-
nide (2a), we isolated the product 3a in 85% yield, which
shows that the reaction goes through a phenylselenium cat-
ionic intermediate (Scheme 2b). Thirdly, the coupling reaction
of biaryl 1a with diselenide 2a by using a catalytic amount of
HI instead of iodine smoothly gave product 3a in 82% yield
(Scheme 2c), which demonstrates that HI is most likely one of
the intermediates of this transformation.
Scheme 2. Investigation of the reaction mechanism.
To further develop our understanding of the reaction mech-
anism, we carried out the reaction in the presence of tertiary
amines as the base (Scheme 2d). The use of DABCO, Hꢂnig’s
base, and Et3N resulted in an abrupt decrease in the yields.
Scheme 3. Proposed mechanism for the reaction.
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iodine (5 mol%, 3.2 mg), and DMSO (3 equiv, 0.75 mmol, 59 mg)
were charged in a Schlenk tube. The reaction was heated to 908C
in an oil bath for 9 h. Then, the reaction mixture was dissolved in
ethyl acetate (10 mL), and washed with 2ꢃ5 mL of an aqueous so-
lution of 10% Na2S2O3. The organic layer was separated, dried over
MgSO4, and concentrated under vacuum. The crude product was
purified by flash chromatography on silica gel (hexane or hexane/
ethyl acetate, 8:2).
tion medium. An important feature of this process is that the
concentration of iodide in the reaction medium is low as it is
continuously consumed by the mild oxidant (DMSO), which
precludes competitive side reactions.
Conclusion
We have developed a green, iodine-catalyzed, regioselective,
and efficient strategy for the preparation of 3-selenyl- and 3-
sulfenyl-imidazo[1,2-a]pyridine derivatives. Under mild condi-
tions, the reaction worked well in the presence of the I2/DMSO
oxidant system with a half molar equivalent of diorganyl di-
chalcogenides, an odorless source of chalcogens, without the
exclusion of air and moisture, which afforded a wide range of
chalcogenated imidazo[1,2-a]pyridines at the C3 position in
good to excellent yields. Furthermore, thiols and sulfonyl hy-
drazides were also successfully applied as alternative sulfeny-
lating agents. This reaction is robust, and no significant loss of
yield is expected upon scale-up. Similarly, the current protocol
was successfully extended to other N-heterocyclic cores.
7-Methyl-2-phenyl-3-(p-tolylselanyl)imidazo[1,2-a]pyridine
(3b) (New compound)
Yield: 88% (83 mg); yellow solid; mp: 119–1208C; 1H NMR
(200 MHz, CDCl3): d=8.27–8.02 (m, 3H), 7.48–7.30 (m, 4H), 7.04–
6.90 (m, 4H), 6.63 (dd, J=7.0, 1.5 Hz, 1H), 2.40 (s, 3H), 2.23 ppm (s,
3H); 13C NMR (50 MHz, CDCl3): d=151.5, 148.0, 137.5, 136.6, 134.0,
130.4, 128.7, 128.4, 128.3, 127.3, 124.8, 116.0, 115.5, 102.4, 21.4,
21.0 ppm; IR (KBr): 3068, 2922, 1652, 1558, 1456, 1350, 1236, 1154,
1032, 844, 770, 669 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2Se:
379.0709 [M+H]+; found: 379.0707.
3-((4-Methoxyphenyl)selanyl)-7-methyl-2-phenylimidazo[1,2-
a]pyridine (3c) (New compound)
Yield: 85% (84 mg); yellow solid; mp: 100–1018C; 1H NMR
(200 MHz, CDCl3): d=8.28–8.08 (m, 3H), 7.52–7.28 (m, 4H), 7.08 (d,
J=8.8 Hz, 2H), 6.76–6.59 (m, 3H), 3.69 (s, 3H), 2.40 ppm (s, 3H);
13C NMR (50 MHz, CDCl3): d=159.0, 151.1, 147.9, 137.5, 134.1,
130.6, 128.8, 128.3, 124.7, 120.9, 116.0, 115.5, 115.4, 103.2, 55.3,
21.4 ppm; IR (KBr): n˜ =3047, 2924, 1652, 1558, 1458, 1340, 1227,
1064, 821, 736, 666 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2OSe:
395.0658 [M+H]+; found: 395.0662.
Experimental Section
General
Proton nuclear magnetic resonance spectra (1H NMR) were ob-
tained at 200 MHz on a Bruker AC-200 NMR spectrometer. Spectra
were recorded in CDCl3. Chemical shifts are reported in ppm, refer-
enced to the solvent peak of CDCl3 or tetramethylsilane (TMS) as
the external reference. Data are reported as follows: chemical shift
(d), multiplicity, coupling constant (J) in Hertz, and integrated in-
tensity. Carbon-13 nuclear magnetic resonance spectra (13C NMR)
were obtained at 50 MHz on a Bruker AC-200 NMR spectrometer.
Spectra were recorded in CDCl3. Chemical shifts are reported in
ppm, referenced to the solvent peak of CDCl3. Abbreviations to
denote the multiplicity of a particular signal are: s (singlet), d (dou-
blet), t (triplet), q (quartet), quint (quintet), sext (sextet), and m
(multiplet). Selenium-77 nuclear magnetic resonance spectra
(77Se NMR) at 38.14 MHz on a Bruker AC-200 NMR spectrometer.
Spectra were recorded in CDCl3. Chemical shifts are reported in
ppm, referenced to diphenyl diselenide as the external reference
(463.15 ppm). High resolution mass spectra were recorded on
a Bruker microTOF-Q II ESI mass spectrometer equipped with an
automatic syringe pump for sample injection. Infrared spectra
were recorded on a Bruker Optics Alpha benchtop FT-IR spectrom-
eter and are reported in frequency of absorption (cmÀ1). The melt-
ing points were determined in a Microquimica MQRPF-301 digital
model equipment with heating plate. Column chromatography
was performed on silica gel (230–400 mesh). Thin layer chromatog-
7-Methyl-2-phenyl-3-(o-tolylselanyl)imidazo[1,2-a]pyridine
(3d) (New compound)
Yield: 79% (74 mg); yellow solid; mp: 129–1318C; 1H NMR
(200 MHz, CDCl3): d=8.17–7.99 (m, 3H), 7.51–7.30 (m, 4H), 7.20–
7.01 (m, 2H), 6.86 (t, J=7.5 Hz, 1H), 6.65 (d, J=7.0 Hz, 1H), 6.54 (d,
J=7.8 Hz, 1H), 2.45 (s, 3H), 2.42 ppm (s, 3H); 13C NMR (50 MHz,
CDCl3): d=152.3, 148.4, 137.7, 136.4, 134.0, 131.7, 130.6, 128.7,
128.4, 128.3, 127.2, 126.8, 126.4, 124.8, 116.1, 115.6, 100.9, 21.4,
21.1 ppm; IR (KBr): n˜ =3059, 2922, 1652, 1558, 1458, 1348, 1230,
1032, 848, 770, 668 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2Se:
379.0709 [M+H]+; found: 379.0708.
3-((2-Methoxyphenyl)selanyl)-7-methyl-2-phenylimidazo[1,2-
a]pyridine (3e) (New compound)
Yield: 75% (74 mg); yellow solid; mp: 125–1268C; 1H NMR
(200 MHz, CDCl3): d=8.20–8.05 (m, 3H), 7.48–7.29 (m, 4H), 7.18–
7.06 (m, 1H), 6.89–6.80 (m, 1H), 6.70–6.58 (m, 2H), 6.41 (dd, J=7.7,
1.5 Hz, 1H), 3.91 (s, 3H), 2.41 ppm (s, 3H); 13C NMR (50 MHz,
CDCl3): d=156.6, 152.3, 148.4, 137.6, 134.0, 128.7, 128.2, 127.4,
127.2, 125.2, 122.0, 120.1, 116.0, 115.5, 110.6, 100.3, 55.9, 21.4 ppm;
IR (KBr): n˜ =3056, 2928, 1652, 1558, 1458, 1486, 1346, 1240, 1021,
raphy (TLC) was performed by using Merck silica gel GF254
,
0.25 mm thickness. For visualization, TLC plates were either placed
under ultraviolet light or stained with iodine vapor and acidic va-
nillin. Most reactions were monitored by TLC for disappearance of
starting material.
856, 752, 668 cmÀ1
; HRMS (ESI): m/z calcd for C21H19N2OSe:
395.0658 [M+H]+; found: 395.0656.
General procedure for the iodine-catalyzed chalcogenation
of imidazo[1,2-a]pyridines 1 by using diorganyl chalcoge-
nides 2 or 4
3-((4-Chlorophenyl)selanyl)-7-methyl-2-phenylimidazo[1,2-
a]pyridine (3 f) (New compound)
A
mixture
of
the
appropriate
imidazo[1,2-a]pyridines
Yield: 91% (90 mg); yellow solid; mp: 144–1468C; 1H NMR
(200 MHz, CDCl3): d=8.18–8.04 (m, 3H), 7.52–7.34 (m, 4H), 7.12 (d,
1 (0.25 mmol), diorganyl dichalcogenide 2 or 4 (0.125 mmol),
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J=8.4 Hz, 2H), 6.99 (d, J=8.5 Hz, 2H), 6.67 (dd, J=7.0, 1.4 Hz, 1H),
2.42 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=151.9, 148.2, 137.9,
133.8, 132.8, 129.8, 129.5, 128.7, 128.5, 128.3, 124.6, 116.2, 115.8,
101.5, 21.4 ppm; IR (KBr): n˜ =3066, 2922, 1652, 1558, 1472, 1350,
(d, J=7.0 Hz, 1H), 2.64 (t, J=6.7 Hz, 2H), 2.43 (s, 3H), 1.54–1.38 (m,
2H), 1.35–1.19 (m, 2H), 0.75 ppm (t, J=7.1 Hz, 3H); 13C NMR
(50 MHz, CDCl3): d=150.1, 147.6, 136.8, 134.4, 128.7, 128.1, 128.0,
124.8, 115.9, 115.2, 103.5, 32.1, 29.3, 22.7, 21.3, 13.5 ppm; IR (KBr):
1087, 1053, 807, 786, 669 cmÀ1
;
HRMS (ESI): m/z calcd for
n˜ =3045, 2927, 1652, 1558, 1474, 1352, 1227, 862, 751, 668 cmÀ1
;
C20H16N2ClSe: 399.0160 [M+H]+; found: 399.0154.
HRMS (ESI) m/z calcd for C18H21N2Se: 345.0865 [M+H]+; found:
345.0870.
3-((4-Fluorophenyl)selanyl)-7-methyl-2-phenylimidazo[1,2-
a]pyridine (3g) (New compound)
3-((4-Methoxyphenyl)thio)-7-methyl-2-phenylimidazo[1,2-
a]pyridine (5c) (New compound)
Yield: 89% (85 mg); yellow solid; mp: 147–1488C; 1H NMR
(200 MHz, CDCl3): d=8.25–8.09 (m, 3H), 7.48–7.34 (m, 4H), 7.13–
7.03 (m, 2H), 6.87 (t, J=8.6 Hz, 2H), 6.67 (d, J=7.0 Hz, 1H),
2.42 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=162.0 (d, JCÀF
246.4 Hz), 151.6, 148.1, 137.7, 133.9, 130.3 (d, JCÀF =7.8 Hz), 128.7,
128.4, 128.3, 125.5 (d, JCÀF =3.2 Hz), 124.6, 117.1, 116.6, 115.9 (d, JCÀ
F =21.1 Hz), 102.3, 21.4 ppm; IR (KBr): n˜ =3066, 2924, 1652, 1558,
1456, 1337, 1021, 815, 736, 669 cmÀ1; HRMS (ESI): m/z calcd for
C20H16N2FSe: 383.0458 [M+H]+; found: 383.0454.
Yield: 87% (75 mg); white solid; mp: 110–1128C; 1H NMR
(200 MHz, CDCl3): d=8.28–8.10 (m, 3H), 7.49–7.30 (m, 4H), 6.97 (d,
J=8.6 Hz, 2H), 6.77–6.62 (m, 3H), 3.69 (s, 3H), 2.40 ppm (s, 3H);
13C NMR (50 MHz, CDCl3): d=158.5, 150.7, 147.3, 137.7, 133.6,
128.4, 128.3, 127.8, 125.8, 123.6, 116.1, 115.6, 115.1, 106.9, 55.3,
21.4 ppm; IR (KBr): n˜ =3059, 2923, 1652, 1558, 1458, 1337, 1231,
1025, 854, 746, 668 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2SO:
347.1213 [M+H]+; found: 347.1214.
=
7-Methyl-2-phenyl-3-((3-(trifluoromethyl)phenyl)selanyl)imida-
zo[1,2-a]pyridine (3h) (New compound)
7-Methyl-2-phenyl-3-(o-tolylthio)imidazo[1,2-a]pyridine (5d)
(New compound)
Yield: 93% (100 mg); yellow solid; mp: 105–1068C; 1H NMR
(200 MHz, CDCl3): d=8.22–8.03 (m, 3H), 7.51–7.34 (m, 6H), 7.21 (t,
J=7.7 Hz, 1H), 7.08 (d, J=7.8 Hz, 1H), 6.68 (d, J=7.0 Hz, 1H),
2.42 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=152.2, 148.3, 138.03,
133.6, 132.8, 131.8 (q, JCÀF =32.5 Hz), 131.03 (q, JCÀF =1.2 Hz), 129.9,
128.64, 128.5, 128.3, 126.2, 124.9, 124.7 (q, JCÀF =3.9 Hz), 123.5 (q,
Yield: 83% (68 mg); white solid; mp: 156–1578C; 1H NMR
(200 MHz, CDCl3): d=8.14 (dd, J=8.0, 1.6 Hz, 2H), 8.02 (d, J=
7.0 Hz, 1H), 7.49–7.32 (m, 4H), 7.17 (d, J=7.3 Hz, 1H), 7.02 (td, J=
7.3, 1.1 Hz, 1H), 6.89 (t, J=6.9 Hz, 1H), 6.64 (dd, J=7.0, 1.5 Hz, 1H),
6.41 (d, J=7.7 Hz, 1H), 2.50 (s, 3H), 2.41 ppm (s, 3H); 13C NMR
(50 MHz, CDCl3): d=151.6, 147.7, 137.8, 134.9, 134.4, 133.5, 130.7,
128.4, 128.3, 126.9, 125.6, 124.1, 123.7, 116.2, 115.6, 104.7, 21.4,
19.8 ppm; IR (KBr): n˜ =3066, 2921, 1652, 1558, 1458, 1340, 1244,
1025, 803, 744, 668 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2S:
331.1263 [M+H]+; found: 331.1265.
J
CÀF =271.5 Hz), 123.4 (q,
JCÀF =3.7 Hz), 116.2, 115.8, 100.8,
21.3 ppm; IR (KBr): n˜ =3061, 2926, 1652, 1558, 1456, 1342, 1247,
1035, 844, 781, 668 cmÀ1; HRMS (ESI): m/z calcd for C21H16N2F3Se:
433.0426 [M+H]+; found: 433.0423.
7-Methyl-3-(naphthalen-1-ylselanyl)-2-phenylimidazo[1,2-
a]pyridine (3i) (New compound)
3-((3-Chlorophenyl)thio)-7-methyl-2-phenylimidazo[1,2-a]pyri-
dine (5e) (New compound)
Yield: 71% (73 mg); yellow solid; mp: 145–1478C; 1H NMR
(200 MHz, CDCl3): d=8.18–8.05 (m, 4H), 7.86–7.77 (m, 1H), 7.67–
7.31 (m, 7H), 7.09 (t, J=7.7 Hz, 1H), 6.84 (d, J=7.3 Hz, 1H), 6.55 (d,
J=7.0 Hz, 1H), 2.37 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=
152.4, 148.4, 137.7, 134.3, 133.9, 132.2, 129.5, 128.8, 128.7, 128.4,
128.3, 127.1, 126.6, 126.4, 126.3, 125.4, 125.1, 124.8, 116.1, 115.6,
100.7, 21.4 ppm; IR (KBr): n˜ =3049, 2916, 1652, 1558, 1458, 1348,
1260, 1023, 956, 844, 766, 687 cmÀ1; HRMS (ESI): m/z calcd for
C24H19N2Se: 415.0709 [M+H]+; found: 415.0711.
Yield: 95% (83 mg); white solid; mp: 101–1038C; 1H NMR
(200 MHz, CDCl3): d=8.19–8.05 (m, 3H), 7.55–7.34 (m, 4H), 7.12–
7.04 (m, 2H), 6.99 (s, 1H), 6.84–6.76 (m, 1H), 6.69 (dd, J=7.0,
1.4 Hz, 1H), 2.42 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=151.7,
147.7, 138.2, 137.8, 135.4, 133.3, 130.4, 128.7, 128.4, 128.3, 126.2,
125.1, 123.5, 123.4, 116.3, 115.9, 104.3, 21.4 ppm; IR (KBr): n˜ =3067,
2924, 1652, 1558, 1458, 1342, 1264, 1070, 824, 734, 668 cmÀ1
;
HRMS (ESI): m/z calcd for C20H16N2SCl: 351.0717 [M+H]+; found:
351.0723.
7-Methyl-2-phenyl-3-(thiophen-2-ylselanyl)imidazo[1,2-a]pyri-
dine (3j) (New compound)
3-((2-Chlorophenyl)thio)-7-methyl-2-phenylimidazo[1,2-a]pyri-
dine (5 f) (New compound)
1
Yield: 82% (76 mg); yellow solid; mp: 89–918C; H NMR (200 MHz,
Yield: 92% (81 mg); white solid; mp: 148–1498C; 1H NMR
(200 MHz, CDCl3): d=8.17–8.05 (m, 3H), 7.52–7.34 (m, 5H), 7.11–
6.89 (m, 2H), 6.70 (dd, J=6.9, 1.5 Hz, 1H), 6.39 (dd, J=7.8, 1.6 Hz,
1H), 2.44 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=152.1, 147.9,
138.3, 134.7, 133.3, 131.1, 130.1, 128.5, 128.3, 127.6, 126.8, 125.6,
123.7, 116.4, 115.9, 103.8, 21.5 ppm; IR (KBr): n˜ =3048, 2922, 1652,
1558, 1456, 1356, 1238, 1030, 851, 724, 668 cmÀ1; HRMS (ESI): m/z
calcd for C20H16N2SCl: 351.0717 [M+H]+; found: 351.0718.
CDCl3): d=8.40 (d, J=7.0 Hz, 1H), 8.23–8.10 (m, 2H), 7.57–7.35 (m,
4H), 7.26–7.19 (m, 1H), 7.14–7.09 (m, 1H), 6.92–6.81 (m, 1H), 6.72
(d, J=7.0 Hz, 1H), 2.40 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=
150.7, 147.7, 137.5, 134.0, 132.5, 131.3, 129.6, 129.0, 128.3, 128.2,
128.0, 124.7, 116.1, 115.6, 104.2, 21.4 ppm; IR (KBr): n˜ =3060, 2924,
1652, 1558, 1472, 1346, 1229, 1023, 854, 742, 668 cmÀ1; HRMS (ESI):
m/z calcd for C18H15N2SeS: 371.0116 [M+H]+; found: 371.0113.
3-(Butylselanyl)-7-methyl-2-phenylimidazo[1,2-a]pyridine (3k)
(New compound)
3-(Benzylthio)-7-methyl-2-phenylimidazo[1,2-a]pyridine (5g)
(New compound)
Yield: 69% (59 mg); yellow liquid; 1H NMR (200 MHz, CDCl3): d=
8.40 (d, J=7.0 Hz, 1H), 8.28–8.16 (m, 2H), 7.60–7.26 (m, 4H), 6.72
Yield: 78% (72 mg); white solid; mp: 114–1158C; 1H NMR
(200 MHz, CDCl3): d=8.20 (dd, J=8.1, 1.4 Hz, 2H), 7.94 (d, J=
&
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Full Paper
7.0 Hz, 1H), 7.50–7.32 (m, 4H), 7.15–7.01 (m, 3H), 6.98–6.85 (m,
2H), 6.50 (dd, J=7.0, 1.3 Hz, 1H), 3.79 (s, 2H), 2.37 ppm (s, 3H);
13C NMR (50 MHz, CDCl3): d=150.1, 146.9, 137.3, 137.1, 134.0,
128.8, 128.5, 128.3, 128.1, 127.3, 126.1, 123.4, 115.9, 114.9, 108.7,
40.7, 21.4 ppm; IR (KBr): n˜ =3064, 2926, 1652, 1558, 1458, 1340,
1209, 1019, 770, 668 cmÀ1; HRMS (ESI): m/z calcd for C21H19N2S:
331.1263 [M+H]+; found: 331.1258.
128.4, 128.3, 128.2, 128.1, 126.6, 123.3, 122.8, 116.9, 102.3,
18.4 ppm; HRMS (ESI): m/z calcd for C20H17N2Se: 365.0552 [M+H]+;
found: 365.0556.
2-(4-Chlorophenyl)-7-methyl-3-(phenylselanyl)imidazo[1,2-
a]pyridine (8c) (New compound)
Yield: 89% (88 mg); yellow solid; mp: 113–1158C; 1H NMR
(200 MHz, CDCl3): d=8.63–8.44 (m, 3H), 7.88 (s, 1H), 7.77 (d, J=
8.6 Hz, 2H), 7.67–7.50 (m, 3H), 7.40–7.32 (m, 2H), 7.09 (d, J=
7.0 Hz, 1H), 2.82 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=149.8,
147.3, 138.4, 135.1, 134.5, 131.8, 129.5, 128.6, 126.2, 125.6, 123.7,
116.1, 116.0, 105.8, 21.4 ppm; IR (KBr): n˜ =3069, 2912, 2669, 1644.
1558, 1458, 1346, 1091, 834, 736 cmÀ1; HRMS (ESI): m/z calcd for
C20H16N2SeCl: 399.0160 [M+H]+; found: 399.0163.
3-((4-Chlorobenzyl)thio)-7-methyl-2-phenylimidazo[1,2-a]pyri-
dine (5h) (New compound)
Yield: 81% (74 mg); white solid; mp: 137–1408C; 1H NMR
(200 MHz, CDCl3): d=8.16–8.07 (m, 2H), 7.97 (d, J=7.0 Hz, 1H),
7.48–7.32 (m, 4H), 6.95 (d, J=8.4 Hz, 2H), 6.73 (d, J=8.2 Hz, 2H),
6.55 (d, J=7.0 Hz, 1H), 3.69 (s, 2H), 2.38 ppm (s, 3H); 13C NMR
(50 MHz, CDCl3): d=150.5, 146.9, 137.3, 135.7, 133.7, 133.2, 130.0,
128.4, 128.3, 128.2, 128.1, 123.2, 115.9, 115.1, 108.0, 39.8, 21.3 ppm;
IR (KBr): n˜ =3065, 2924, 1652, 1558, 1458, 1348, 1058, 774,
668 cmÀ1; HRMS (ESI): m/z calcd for C21H18N2SCl: 365.0874 [M+H]+;
found: 365.0872.
2-(3-Bromophenyl)-7-methyl-3-(phenylselanyl)imidazo[1,2-
a]pyridine (8d) (New compound)
Yield: 92% (102 mg); yellow solid; mp: 103–1058C; 1H NMR
(200 MHz, CDCl3): d=8.35–8.28 (m, 1H), 8.22 (d, J=7.0 Hz, 1H),
8.10 (dt, J=7.7, 1.2 Hz, 1H), 7.55–7.43 (m, 2H), 7.33–7.22 (m, 1H),
7.20–7.05 (m, 5H), 6.72 (dd, J=7.0, 1.6 Hz, 1H), 2.43 ppm (s, 3H);
13C NMR (50 MHz, CDCl3): d=149.2, 147.6, 138.7, 135.4, 131.6,
131.5, 130.6, 129.9, 129.8, 128.5, 127.2, 127.0, 124.9, 122.5, 116.3,
115.9, 103.0, 21.5 ppm; IR (KBr): n˜ =3049, 2905, 1652 1558, 1458,
1350, 1233, 1150, 1066, 732, 667 cmÀ1; HRMS (ESI): m/z calcd for
C20H16N2SeCl: 399.0160 [M+H]+; found: 399.0163.
7-Methyl-2-phenyl-3-(thiophen-2-ylthio)imidazo[1,2-a]pyridine
(5i) (New compound)
Yield: 88% (71 mg); light yellow solid; mp: 110–1118C; 1H NMR
(200 MHz, CDCl3): d=8.38–8.22 (m, 3H), 7.53–7.36 (m, 4H), 7.19–
7.08 (m, 1H), 7.04–6.95 (m, 1H), 6.89–6.79 (m, 1H), 6.72 (dd, J=7.0,
1.4 Hz, 1H), 2.39 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=150.0,
147.0, 137.8, 134.0, 133.6, 129.7, 128.6, 128.5, 128.4, 127.7, 127.5,
123.5, 116.2, 115.6, 108.3, 21.4 ppm; IR (KBr): n˜ =3054, 2928, 1658,
1558, 1456, 1345, 1056, 845, 779, 668 cmÀ1; HRMS (ESI): m/z calcd
for C18H15N2S: 323.0671 [M+H]+; found: 323.0673.
2-(3-Bromophenyl)-7-methyl-3-(phenylthio)imidazo[1,2-a]pyri-
dine (8ad) (New compound)
Yield: 96% (95 mg); white solid; mp: 120–1218C; 1H NMR
(200 MHz, CDCl3): d=8.38 (s, 1H), 8.22–8.09 (m, 2H), 7.56–7.42 (m,
2H), 7.31–7.10 (m, 4H), 7.01–6.93 (m, 2H), 6.72 (d, J=7.0 Hz, 1H),
2.42 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=158.1, 148.6, 146.8,
138.9, 134.6, 131.5, 131.1, 129.9, 129.4, 126.7, 126.3, 125.7, 123.6,
122.5, 116.3, 115.9, 106.5, 21.4 ppm; IR (KBr): n˜ =3048, 2912, 1658,
1558, 1456, 1337, 1070, 848, 779, 668 cmÀ1; HRMS (ESI): m/z calcd
for C20H16N2SBr: 397.0192 [M+H]+; found: 397.0190.
3-(Isopropylthio)-7-methyl-2-phenylimidazo[1,2-a]pyridine (5j)
(New compound)
Yield: 58% (41 mg); yellow liquid; 1H NMR (200 MHz, CDCl3): d
8.46–8.29 (m, 3H), 7.52–7.34 (m, 4H), 6.72 (dd, J=7.0, 1.6 Hz, 1H),
3.13 (hept, J=6.7 Hz, 1H), 2.43 (s, 3H), 1.14 ppm (d, J=6.7 Hz, 6H);
13C NMR (50 MHz, CDCl3): d=149.9, 146.9, 137.1, 134.3, 128.4,
128.3, 128.1, 123.8, 116.1, 115.2, 109.5, 40.8, 23.2, 21.4 ppm; IR
(KBr): n˜ =3056, 2920, 1652, 1558, 1456, 1352, 1227, 1054, 848, 795,
669 cmÀ1; HRMS (ESI): m/z calcd for C17H19N2S: 283.1263 [M+H]+;
found: 283.1259.
2-(4-Methoxyphenyl)-7-methyl-3-(phenylselanyl)imidazo[1,2-
a]pyridine (8e) (New compound)
Yield: 81% (79 mg); yellow solid; mp: 104–1058C; 1H NMR
(200 MHz, CDCl3): d=8.20–8.05 (m, 3H), 7.44 (s, 1H), 7.19–7.05 (m,
5H), 7.00–6.91 (m, 2H), 6.64 (dd, J=7.0, 1.6 Hz, 1H), 3.82 (s, 3H),
2.41 ppm (s, 3H); 13C NMR (50 MHz, CDCl3): d=159.9, 151.6, 148.1,
137.5, 131.4, 130.0, 129.7, 128.1, 126.6, 124.7, 115.9, 115.4, 113.8,
101.1, 55.3, 21.4 ppm; IR (KBr): n˜ =3066, 2924, 1652, 1553, 1456,
1248, 1142, 1021, 872, 736, 668 cmÀ1; HRMS (ESI): m/z calcd for
C21H19N2SeO: 395.0658 [M+H]+; found: 395.0659.
7-Methyl-2-phenyl-3-(propylthio)imidazo[1,2-a]pyridine (5k)
(New compound)
Yield: 54% (38 mg); yellow liquid; 1H NMR (200 MHz, CDCl3): d=
8.45–8.22 (m, 2H), 7.53–7.34 (m, 2H), 6.82–6.68 (m, 1H), 2.61 (t, J=
7.6 Hz, 1H), 2.44 (s, 3H), 1.55–1.37 (m, 2H), 0.88 ppm (t, J=7.3 Hz,
3H); 13C NMR (50 MHz, CDCl3): d=149.4, 146.8, 137.1, 134.1, 128.4,
128.3, 128.1, 123.7, 116.2, 115.3, 109.7, 38.0, 23.1, 21.4, 13.3 ppm; IR
(KBr): n˜ =3057, 2924, 1652, 1558, 1456, 1340, 1228, 1054, 838, 797,
668 cmÀ1; HRMS (ESI): m/z calcd for C17H19N2S: 283.1263 [M+H]+;
found: 283.1266.
2-(4-Methoxyphenyl)-7-methyl-3-(phenylthio)imidazo[1,2-
a]pyridine (8ae) (New compound)
1
Yield: 80% (69 mg); white solid; mp: 110–1098C H NMR (200 MHz,
CDCl3): d=8.20–8.01 (m, 3H), 7.45 (s, 1H), 7.25–7.07 (m, 3H), 7.04–
6.89 (m, 4H), 6.64 (d, J=6.9 Hz, 1H), 3.80 (s, 3H), 2.40 ppm (s, 3H);
13C NMR (50 MHz, CDCl3): d=159.9, 151.2, 147.5, 137.8, 135.7,
129.6, 129.4, 126.1, 125.9, 125.4, 123.6, 116.0, 115.5, 113.8, 104.5,
55.3, 21.4 ppm; IR (KBr): n˜ =3063, 2961, 1652, 1558, 1458, 1248,
6-Methyl-2-phenyl-3-(phenylselanyl)imidazo[1,2-a]pyridine
(8a) (New compound)
Yield: 87% (78 mg); yellow solid; mp: 109–1118C; 1H NMR
(200 MHz, CDCl3): d=8.18–8.08 (m, 3H), 7.61 (d, J=9.1 Hz, 1H),
7.46–7.33 (m, 3H), 7.19–7.05 (m, 6H), 2.28 ppm (s, 3H); 13C NMR
(50 MHz, CDCl3): d=151.7, 146.8, 133.9, 131.3, 129.7, 129.6, 128.7,
1172, 1032, 840, 734, 668 cmÀ1
C21H19N2SO: 347.1213 [M+H]+; found: 347.1217.
; HRMS (ESI): m/z calcd for
Chem. Eur. J. 2016, 22, 1 – 10
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ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2-(4-Fluorophenyl)-3-(phenylthio)imidazo[1,2-a]pyridine (8af)
(New compound)
3-((4-methoxyphenyl)selanyl)-1H-indazole (10b) (New com-
pound)
Yield: 92% (73 mg); white solid; mp: 1258C; 1H NMR (200 MHz,
CDCl3): d=8.00–7.83 (m, 3H), 7.46–7.35 (m, 1H), 7.09–6.77 (m, 6H),
6.74–6.65 (m, 2H), 6.61–6.51 ppm (m, 1H); 13C NMR (50 MHz,
CDCl3): d=163.1 (d, JCÀF =248.4 Hz), 150.5, 147.1, 135.0, 130.2 (d,
Yield: 79% (60 mg); yellow solid; mp: 99–1018C; 1H NMR
(200 MHz, CDCl3): d=12.50 (s, 1H), 7.79–7.61 (m, 2H), 7.52–7.30
(m, 3H), 7.19–7.10 (m, 1H), 6.72 (d, J=8.8 Hz, 2H), 3.70 ppm (s,
3H); 13C NMR (50 MHz, CDCl3): d=159.3, 141.3, 134.4, 134.2, 127.3,
126.0, 121.5, 121.1, 120.0, 115.0, 110.8, 55.3 ppm; IR (KBr): n˜ =3402,
3050, 3027, 2990, 1655, 1548, 1450, 1360, 1231, 1142, 1031, 846,
775, 678 cmÀ1; HRMS (ESI): m/z calcd for C14H13N2OSe: 305.0186
[M+H]+; found: 305.0193.
J
CÀF =8.1 Hz), 129.6, 129.5, 126.8, 126.2, 125.6, 124.5, 117.6, 115.4 (d,
CÀF =21.5 Hz), 113.2, 106.1 ppm; IR (KBr): n˜ =3040, 2935, 1650,
J
1539, 1456, 1397, 1264, 1154, 1075, 830, 732, 669 cmÀ1; HRMS (ESI):
m/z calcd for C19H14N2SF: 321.0856 [M+H]+; found: 321.0854.
2-(4-Cyanophenyl)-3-(phenylselanyl)imidazo[1,2-a]pyridine
(8g) (New compound)
3-((4-chlorophenyl)selanyl)-1H-indazole (10c) (New com-
pound)
1
Yield: 85% (79 mg); yellow solid mp: 97–988C; H NMR (200 MHz,
Yield: 85% (65 mg); white solid; mp: 105–1078C; 1H NMR
(200 MHz, CDCl3): d=12.38 (s, 1H), 7.75–7.58 (m, 2H), 7.47–7.29
(m, 3H), 7.25–7.09 ppm (m, 3H); 13C NMR (50 MHz, CDCl3): d=
141.3, 133.2, 132.5, 129.5, 128.9, 127.6, 126.2, 122.0, 121.0,
110.8 ppm; IR (KBr): n˜ =3400, 3062, 3020, 1645, 1548, 1455, 1357,
1234, 1147, 1026, 844, 770, 681 cmÀ1; HRMS (ESI): m/z calcd for
C13H10N2ClSe: 308.9690 [M+H]+; found: 308.9691.
CDCl3): d=8.44–8.25 (m, 3H), 7.78–7.62 (m, 3H), 7.41–7.30 (m, 1H),
7.24–7.05 (m, 4H), 6.90 ppm (t, J=6.9 Hz, 1H); 13C NMR (50 MHz,
CDCl3): d=149.3, 147.9, 138.3, 132.1, 130.2, 129.9, 129.1, 128.3,
127.2, 127.1, 125.7, 119.0, 117.8, 113.6, 111.7, 104.3 ppm; IR (KBr):
n˜ =2962, 2924, 1655, 1558, 1459, 1340, 1265, 1070, 803, 742,
668 cmÀ1; HRMS (ESI): m/z calcd for C20H14N3Se: 376.0348 [M+H]+;
found: 376.0352.
General Procedure for the iodine-catalyzed reactions of
thiols 6 with 7-methyl-2-phenylimidazo[1,2-a]pyridine (1a)
Acknowledgements
We gratefully acknowledge CAPES, CNPq, CERSusChem GSK/
FAPESP (grant 2014/50249–8), INCT-Catꢀlise and FAPESC-
Pronex for financial support. J.R. (postdoctoral fellow) and S.S.
(postdoctoral fellow) are grateful to CAPES, CNPq and TWAS
for the fellowships. The authors also acknowledge CEBIME for
the HRMS analysis.
A
mixture of 7-methyl-2-phenylimidazo[1,2-a]pyridine 1a
(0.25 mmol, 52 mg) and the appropriate thiol 6 (0.25 mmol) were
used under standard conditions.
General Procedure for the iodine-catalyzed reactions of aryl-
sulfonyl hydrazides 7 with 7-methyl-2-phenylimidazo[1,2-
a]pyridine (1a)
A
mixture of 7-methyl-2-phenylimidazo[1,2-a]pyridine 1a
Keywords: green chemistry · iodine · nitrogen heterocycles ·
selenium · sulfur
(0.25 mmol, 52 mg) and the appropriate arylsulfonyl hydrazide 7
(0.25 mmol) were used under standard conditions.
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CDCl3): d=12.78 (s, 1H), 7.74–7.62 (m, 2H), 7.45–7.34 (m, 3H),
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Received: February 19, 2016
Published online on && &&, 0000
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FULL PAPER
&
Green Chemistry
J. Rafique, S. Saba, A. R. Rosꢀrio,
A. L. Braga*
&& – &&
Chalcogenation of N-heterocycles:
Highly efficient molecular-iodine-cata-
lyzed chalcogenations (S and Se) of imi-
dazo[1,2-a]pyridines are achieved by
using diorganoyl dichalcogenides under
solvent-free conditions.
Regioselective, Solvent- and Metal-
Free Chalcogenation of Imidazo[1,2-
a]pyridines by Employing I2/DMSO as
Catalytic Oxidation System
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Chem. Eur. J. 2016, 22, 1 – 10
www.chemeurj.org
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ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!