Direct sulfenylation of imidazoheterocycles with disulfides in an iodine-hydrogen peroxide system

Article abstract of DOI:10.1055/s-0034-1379941

Imidazoheterocycles undergo efficient and regioselective sulfenylation with disulfides using the iodine/hydrogen peroxide system in ethanol at 25 °C. This green strategy tolerates a wide range of functional groups to afford diverse sulfenylated imidazoheterocycles in high yields. Moreover, the fipronil (a pesticide) skeleton can be readily attached to imidazoheterocycles using this strategy, which is significant in drug development.

Full text of DOI:10.1055/s-0034-1379941

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2015, 47, 659–671
paper
659
X.-M. Ji et al.
Paper
Synthesis
Direct Sulfenylation of Imidazoheterocycles with Disulfides in an
Iodine–Hydrogen Peroxide System
N
S
N
Xiao-Ming Ji
I2 (20 mol%)
H2O2 (2 equiv)
I2 (20 mol%)
H2O2 (2 equiv)
R2
Ar
R1
Ar
R1
S
S
R1
N
N
Shu-Juan Zhou
Fan Chen*
EtOH, 25 °C, 18 h
EtOH, 25 °C, 18 h
S
R1
S
25 examples
up to 94% yield
14 examples
up to 93% yield
Xing-Guo Zhang
Ri-Yuan Tang*
College of Chemistry and Materials Engineering, Wenzhou
University, Wenzhou 325035, P. R. of China
try@wzu.edu.cn
fanchen@wzu.edu.cn
Received: 04.11.2014
Accepted after revision: 01.12.2014
Published online: 08.01.2015
azoheterocycles.9t,15c,19–21 The present metal-free methods
suffer from some drawbacks such as using corrosive acid,20b
a commercially unavailable ionic liquid,20c or excess N-chlo-
rosuccinimide.20d Major limitations in scaling up reactions
arise from metal pollution, and the use of harsh reaction
conditions and excess reagents. During this work, Hiebel et
al.21 developed an efficient method for the sulfenylation of
imidazoheterocycles with thiophenols using iodine as a
catalyst in PEG400. However, a higher reaction temperature
is required to resolve the solubility problems of some start-
ing materials in PEG400. These sulfenylation methodologies
mainly focus on imidazo[1,2-a]pyridines, whereas the
sulfenylation of imidazo[2,1-b]thiazoles remains scarce.20d
The development of a highly efficient, ecofriendly, practical,
and applicable method for the sulfenylation of imidazo[2,1-
b]thiazoles is highly desirable. We hypothesized that cata-
lytic amount of elemental iodine would accomplish the
sulfenylation of imidazoheterocycles with disulfides in the
presence of hydrogen peroxide. Moreover, disulfides are de-
sirable sulfenylating agents as they are less toxic and more
stable than thiols. As a part of our continuing interest in di-
rect C–H sulfenylation,15b,22 we report an iodine/hydrogen
peroxide-promoted regioselective sulfenylation of imidazo-
heterocycles with disulfides in ethanol at room tempera-
ture.
Initially, we used the sulfenylation of 6-phenylimid-
azo[2,1-b]thiazole (1a) with diphenyl disulfide as the mod-
el reaction (Table 1), various solvents were investigated in
the presence of 20 mol% of iodine and two equivalents of
hydrogen peroxide at 25 °C (entries 1–5). The results show
that both toluene and 1,2-dichloroethane gave moderate
yields of 3aa (entries 1 and 2); polar solvents were more
suitable for the sulfenylation [yield of 3aa: 83% (DMF), 95%
(DMSO), and 92% (EtOH); entries 3–5]. Some oxidants were
examined in ethanol as an ecofriendly solvent. Both tert-
butyl hydroperoxide and potassium persulfate gave 3aa in
DOI: 10.1055/s-0034-1379941; Art ID: ss-2014-f0673-op
Abstract Imidazoheterocycles undergo efficient and regioselective
sulfenylation with disulfides using the iodine/hydrogen peroxide sys-
tem in ethanol at 25 °C. This green strategy tolerates a wide range of
functional groups to afford diverse sulfenylated imidazoheterocycles in
high yields. Moreover, the fipronil (a pesticide) skeleton can be readily
attached to imidazoheterocycles using this strategy, which is significant
in drug development.
Key words iodine, sulfenylation, disulfide, imidazothiazole, imidazo-
pyridine
The functionalization of imidazoheterocycles is an im-
portant task for biochemists and synthetic chemists be-
cause imidazoheterocyclic motifs are privileged scaffolds
that exhibit a broad range of biological activity.1 For exam-
ple, imidazo[2,1-b]thiazoles exhibit good activity as anti-
cancer agents,2 SIRT1 activators,3 RSK2 inhibitors,4 and an-
tiviral agents,5 and in the treatment of cystic fibrosis.6 Sev-
eral drugs (including alpidem, olprinone, necopidem,
zolimidine, and saripidem) have been developed by func-
tionalization of the imidazo[1,2-a]pyridine skeleton.7 As a
result, substantial efforts have been devoted to the func-
tionalization of imidazoheterocycles.8,9
Sulfenyl groups are important structural units in many
naturally occurring and bioactive compounds.10 In recent
years, direct sulfenylation of heterocyclic compounds has
become an intriguing strategy for the synthesis of biological
molecules. Significant progress in the direct sulfenylation of
indoles has been made using various sulfenylating agents
such as sulfenyl halides,11 N-thioimides,12 sulfonium salts,13
thiols,14 disulfides,15 quinone mono-O,S-acetals,16 arenesul-
fonyl chlorides,17 and sulfonyl hydrazides.18 However, little
attention has been paid to the direct sulfenylation of imid-
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good yields, but these yields were lower than those ob-
tained with hydrogen peroxide (entries 6 and 7); molecular
oxygen gave a much lower yield of 3aa than other oxidants
(48%, entry 8). We then attempted to decrease the loading
of iodine and hydrogen peroxide, respectively (entries 9
and 10). The results show that using 10 mol% of iodine de-
creased the yield of 3aa to 71%, and one equivalent of hy-
drogen peroxide lower the yield to 64%. In the absence of
hydrogen peroxide, one equivalent of iodine gave 3aa in
52% yield, and 20 mol% of iodine gave a 33% yield, suggest-
ing that hydrogen peroxide is key to the catalytic cycle (en-
tries 11 and 12); the transformation did not proceed in the
absence of iodine (entry 13). The addition of 2,2,6,6-te-
tramethylpiperdin-1-oxyl (TEMPO) to the reaction ap-
peared to have almost no effect on the yield; 84% yield of
product 3aa was still obtained in the presence of one equiv-
alent of TEMPO (entry 14). It is noteworthy that the reac-
tion can be scaled up without lowering the yield, using 4
mmol of 1a still gave the target product in 91% yield under
the standard conditions (entry 5). Finally, the optimized
conditions were: iodine (20 mol%), hydrogen peroxide (2
equiv), and ethanol at 25 °C.
With this iodine-catalyzed procedure in hand, the scope
of the disulfides was investigated (Scheme 1). Diphenyl di-
sulfides containing Me, OMe, Cl, and F groups were tolerat-
ed well under the standard conditions. Both electron-
donating or electron-withdrawing groups gave excellent
yields of products 3ab–ah. For example, bis(halo-substitut-
ed phenyl) disulfides, both monochloro- or dichloro-substi-
tuted, have excellent reactivity in the sulfenylation giving
products 3ad–ah; these are synthetically useful for further
modification because of the diverse reactivity of halo
groups. To our delight, the sulfenylation of less reactive di-
alkyl disulfides was successfully carried out under 60 °C us-
ing one equivalent of dimethyl disulfide or diethyl disulfide,
giving the target products 3ai and 3aj, respectively, in ex-
cellent yields. Because of the diverse bioactivity of hetero-
cycles, the sulfenylation of heterocyclic disulfides with im-
idazo[2,1-b]thiazoles is promising in drug development.
Heterocyclic disulfides, including thiophenyl, furanyl, and
pyridinyl, were used to sulfenylate imidazo[2,1-b]thiazoles.
All of these disulfides gave the corresponding products
3ak–am in excellent yields (83–94%). To further demon-
strate the versatility of this sulfenylation strategy, dipyri-
din-2-yl disulfide was allowed to react with various imid-
azo[2,1-b]thiazoles to give 3bm–km. The results show that
electron-donating substituents on the benzene ring of 6-
phenylimidazo[2,1-b]thiazole favor the reaction, giving the
corresponding products 3bm–dm in good yields under the
standard conditions. To our delight, the useful hydroxy
group was well tolerated under the standard conditions,
providing the target product 3dm in 85% yield.
Table 1 Screening of Optimal Conditionsa
S
N
S
N
I2, oxidant
Ph
+
PhSSPh
N
Ph
solvent, 25 °C
N
S
Ph
3aa
1a
2a
Despite the reduction in yields when electron-with-
drawing groups such as halo groups are present under stan-
dard conditions, excellent yields could be obtained by ele-
vating the temperature or increasing the disulfide loading
for products 3em–hm. For example, the reaction of bromo-
substituted substrate with 0.8 equivalents of dipyridin-2-yl
disulfide at 60 °C improved the yield of 3hm from 68% to
93%. We next evaluated the effect of substituents on the
thiazole ring. The methyl-substituted substrate gave a 91%
yield of product 3im at 60 °C using 0.8 equivalents of dipyr-
idin-2-yl disulfide. Unexpectedly, a benzothiazole-contain-
ing substrate gave a 98% yield of the iodinated product in-
stead of product 3jm at 25 °C, but a 89% yield of product
3jm was obtained at 60 °C. It was pleasing to find that the
sulfenylation of 6-methylimidazo[2,1-b]thiazole went at
60 °C to provide 3km in 87% yield.
Subsequently, the scope of the reaction with imid-
azo[1,2-a]pyridines was investigated (Scheme 2). Firstly,
several disulfides were reacted with 2-phenylimidazo[1,2-
a]pyridine, all of these disulfides exhibited good reactivity
giving products 5aa–al. Encouragingly, scaling up the reac-
tion of 4a twentyfold still afforded the product 5aa in 89%
yield. Heterocyclic disulfides, including thiophenyl, furanyl,
and pyridinyl, performed well, giving the target product
5ak–am in good yields. Examination of substituents on the
Entry
Catalyst
Oxidant
(equiv)
Solvent
Isolated yield
(%)
1
2
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (20 mol%)
I2 (10 mol%)
I2 (20 mol%)
I2 (1 equiv)
I2
H2O2 (2)
H2O2 (2)
H2O2 (2)
H2O2 (2)
H2O2 (2)
TBHP
K2S2O8
O2
toluene
DCE
43
51
3
DMF
83
4
DMSO
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
95
5
92 (91)b
86
6
7
80
8c
9
48
H2O2
71
10
11
12
13
14d
H2O2 (1)
–
64
52
–
33
–
H2O2
–
I2
H2O2
84
a Reaction conditions: 1a (0.2 mmol), 2a (0.1 mmol, 1 equiv), I2, [O], solvent
(2 mL), 25 °C; materials 30% aq H2O2 (30% in water) or 60% TBHP in decane.
b 1a (4 mmol), 2a (2 mmol), EtOH (8 mL).
c O2 (1 bar).
d TEMPO (1 equiv) was added.
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pyridine ring showed that halo-substituted substrates, ex-
cept the fluoro-substituted substrate, produced the target
products 5bm–em in excellent yields at 60 °C, albeit lower
yields were obtained at 25 °C. To our delight, the substrate
with a hydroxy group was tolerated well under the stan-
dard conditions giving the product 5fm which could be fur-
ther modified at the hydroxy group; this is important in
synthetic chemistry and pharmaceutical chemistry. Under
the standard conditions, dithiophen-2-yl disulfide also
smoothly sulfenylated a bromo-substituted imidazo[1,2-
a]pyridine to provide target product 5ek in 89% yield. The
I2 (20 mol%
H2O2 (2 equiv)
S
N
R1
R2
S
N
R1
+
R2SSR2
N
N
EtOH, 25 °C, 18 h
S
3
1
2
S
N
S
N
S
N
S
N
S
N
N
N
N
N
N
S
S
S
S
S
Cl
Cl
MeO
Cl
Cl
3ae, 90%
3ab, 94%
3ac, 95%
3ad, 93%
3af, 88%
S
N
S
N
N
S
N
S
N
N
N
S
N
N
S
S
S
N
F
SEt
SMe
S
F
3aj, 90%a
3ai, 92%a
3ak, 94%
3ag, 92%
3ah, 93%
S
N
S
N
N
S
N
S
N
S
N
OMe
N
N
N
N
HO
S
S
S
S
S
N
N
N
N
O
3bm, 84%
3am, 91%
3cm, 91%
3dm, 85%
3al, 83%
S
N
S
S
N
S
N
S
N
N
S
N
F
Cl
Br
N
N
N
N
S
S
S
F
S
N
N
N
N
N
3fm, 52% (85%)a
3em, 63% (90%)a
3im, 75% (91%)b
3gm, 65% (91%)b
3hm, 68% (93%)b
S
S
N
N
N
N
S
N
S
N
3km, 87%b
3jm, 0% (89%)c
Scheme 1 Scope of the sulfenylation of imidazo[1,2-a]pyridine. Reaction conditions: 1 (0.2 mmol), 2 (0.1 mmol, 0.5 equiv), I2 (20 mol%), H2O2
(2 equiv), EtOH (2 mL), 25 °C, 18 h. a Using disulfide (1 equiv), 60 °C. b Using disulfide (0.8 equiv), 60 °C. c 60 °C.
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I2 (20 mol%)
H2O2 (2 equiv)
N
N
R1
R1
Ph
R2
Ph
+
R2SSR2
N
N
EtOH, 25 °C, 18 h
S
4
2
5
N
N
N
N
N
N
N
N
N
O
N
S
S
S
S
S
N
Cl
S
Cl
5af, 85%
5am, 76% (91%)b
5aa, 91% (89%)a
5ak, 92%
5al, 88%
OH
Cl
Br
N
N
N
N
N
N
N
N
N
N
N
F
S
S
S
S
S
N
N
N
N
5dm, 71% (90%)b
5em, 71% (93%)b
5bm, 78% (88%)c
5fm, 90%
5cm, 51% (53%)c
Br
N
N
N
N
S
S
N
S
5gm, 86%b
5ek, 89%
Scheme 2 Scope of the sulfenylation of imidazo[1,2-a]pyridine. Reaction conditions: 4 (0.2 mmol), 2 (0.1 mmol, 0.5 equiv), I2 (20 mol%), H2O2
(2 equiv), EtOH (2 mL), 25 °C, 18 h. a Disulfide (1 equiv), 60 °C. b Disulfide (0.8 equiv), 60 °C. c 60 °C.
S
N
N
Ph
Ph
1a
4a
N
N
PhSeSePh
(1)
Se
Se
6
Ph
Ph
7, 88%
8, 87%
S
N
N
NC
S
N
Ph
2
Ph
N
N
N
H2N
N
NH2
Cl
S
Cl
1a
N
H2N
4a
S
Cl
Cl
(2)
N
CN
N
F3C
CN
F3C
Cl
Cl
11, 87%
CF3
10, 86%
9
Scheme 3 Selenylation and synthesis of fipronil analogues. Reaction conditions: 4a or 1a (0.2 mmol), I2 (20 mol%), H2O2 (2 equiv), EtOH (2 mL), 60 °C,
18 h; for 6 (0.16 mmol, 0.8 equiv), for 9 (0.1 mmol, 0.5 equiv).
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sulfenylation of 2-methylimidazo[1,2-a]pyridine with
dipyridin-2-yl disulfide was also carried out at 60 °C to af-
ford product 5gm in 86% yield.
reaction. This successful S–S bond cleavage of pyrazolyl di-
sulfide followed by direct sulfenylation with imidazo-
heterocycles is significant for pesticide and drug design.25
To elucidate the reaction mechanism, a serial of control
experiments were conducted as showed in Scheme 4.
During the reaction development, a small amount of iodin-
ated product 12 was observed by GC-MS. We speculated
that the electron-rich heterocyclic compounds can undergo
an oxidative iodination in the iodine/hydrogen peroxide
system.26 A quantitative iodinated product 12 was obtained
in the reaction of 6-phenylimidazo[2,1-b]thiazole (1a) with
one equivalent of iodine and two equivalents of hydrogen
To test their use in practical applications, diphenyl
diselenide was reacted with 6-phenylimidazo[2,1-b]thi-
azole and 2-phenylimidazo[1,2-a]pyridine giving 7 and 8 in
88% and 87% yields, respectively [Scheme 3 (1)]. Further-
more, new fipronil analogues 10 and 11 were readily to be
prepared by this iodine-catalyzed sulfenylation strategy in
good yields [Scheme 3,(2)].23,24 It is noteworthy that func-
tional groups, including amino, cyano, chloro, trifluoro-
methyl, and the pyrazole ring, were well tolerated in the
S
N
I2 (1 equiv)
H2O2 (2 equiv)
S
N
Ph
(1)
(2)
N
Ph
Ph
N
EtOH, 25 °C, 2 h
I
1a, 0.1 mmol
12, 100%
S
N
S
N
S
N
Ph
N
+
PhSSPh
+
Ph
N
EtOH, 25 °C,18 h
N
S
I
Ph
12, 0.1 mmol
recovered: 98%
2a, 0.05 mmol
recovered: 98%
3aa, 0%
1a, 0%
S
N
N
S
N
S
N
N
Ph
H2O2 (2 equiv)
Ph
+
PhSSPh
+
Ph
N
(3)
EtOH, 25 °C,18 h
S
Ph
I
12, 0.1 mmol
recovered: 98%
2a, 0.05 mmol
recovered: 96%
3aa, 0%
1a, 0%
S
N
N
S
N
Ph
Ph
I2
+
PhSSPh
+
N
(4)
EtOH, 60 °C,18 h
S
I
Ph
12, 0.1 mmol
2a, 0.05 mmol
3aa, 91%
S
N
N
I2 (20 mol%)
H2O2 (2 equiv)
S
N
O
Ph
Ph
(5)
+
PhSSPh
+
S
N
Ph OEt
EtOH, 25 °C,18 h
S
I
Ph
12, 0.1 mmol
conversion: 92%
2a, 0.05 mmol
3aa, 75%
16%
conversion: 100%
S
N
N
S
N
S
N
N
Ph
HI (0.1 mmol)
Ph
+
PhSSPh
+
Ph
N
(6)
EtOH, 25 °C,18 h
S
I
Ph
12, 0.1 mmol
recovered: 98%
Scheme 4 Control experiments
2a, 0.05 mmol
3aa, 0%
1a, 0%
recovered: 98%
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PhSSPh
I2
2 PhSI
H2O
S
N
I2, H2O2
S
N
Ph
Ph
N
N
1a
I
12
H2O2
S
N
Ph
HI
N
S
H
Ph
I
S
N
N
13
Ph
S
Ph
3aa
Scheme 5 A possible mechanism
peroxide for two hours, suggesting that the iodinated prod-
uct 12 may be a reaction intermediate [Scheme 4 (1)]. We
next reacted the iodinated product 12 with diphenyl disul-
fide in the absence of iodine and hydrogen peroxide, how-
ever no sulfenylated product 3aa or deiodinated product 1a
was found [Scheme 4 (2)]. Further investigation showed
that this sulfenylation was unsuccessful even when on the
addition of two equivalents of hydrogen peroxide [Scheme
4 (3)]. Interestingly, in the absence of iodine/hydrogen per-
oxide, iodinated product 12 reacted with diphenyl disulfide
at 60 °C to afford product 3aa in 91% yield together with el-
emental iodine [Scheme 4 (4)]. This result demonstrated
that iodinated product 12 could be readily deiodinated at
60 °C, which can account for better yields obtaining at 60 °C
for some substrates (e.g., product 3jm). The treatment of io-
dinated product 12 with diphenyl disulfide under standard
conditions gave the target product 3aa in 75% yield togeth-
er with ethyl benzenesulfinate as a byproduct in 16% yield
[Scheme 4 (5)]. Finally, the reaction of iodinated product 12
with diphenyl disulfide was conducted in the presence of
hydrogen iodide (55% aqueous solution), in which hydrogen
iodide may contribute to reductive deiodination.27 Howev-
er, target product 3aa and deiodinated product 1a were not
obtained. These results suggested that iodinated product 12
may be a byproduct and could undergo a deiodination pro-
cess to regenerate substrate 1a under the standard condi-
tions.28
dine/hydrogen peroxide system, substrate 1a would under-
go an oxidative iodination and deiodination process to yield
the iodinated product 12 and regenerate the substrate 1a.28
In summary, we have developed an iodine-catalyzed
sulfenylation reaction of imidazoheterocycles with disul-
fide in the presence of hydrogen peroxide. This green strat-
egy provides a convenient and efficient route for the prepa-
ration of diverse sulfenylated imidazoheterocycles under
mild conditions. Many functional groups, including halo,
amino, hydroxy, methoxy, cyano, trifluoromethyl, thiophe-
nyl, furanyl, pyridinyl, and pyrazolyl, were tolerated well
under the standard conditions. Generally, this reaction has
broader substrate scope than previous reports.15c,19–21
Moreover, the reaction can be scaled up, giving excellent
yields. This green strategy also allows for the synthesis of
fipronil analogues that are significant in drug development.
1H and 13C NMR spectra were measured on a Bruker Avance-III 500
instrument (500 MHz for 1H, 125 MHz for 13C NMR) using CDCl3 or
DMSO-d6 as the solvent referenced to internal TMS (δ = 0,0 ppm) as
the standard. Mass spectra were measured on a Shimadzu GC-MS-
QP2010 Plus spectrometer (EI). HRMS (ESI) analysis was measured on
a Bruker micrOTOF-Q II instrument. IR analysis was measured on Ni-
colet IS10 spectrophotometer (ATR).
Preparation of imidazoheterocycles: All starting materials were readi-
ly prepared according to reported methods.29
6-Phenyl-5-(phenylthio)imidazo[2,1-b]thiazole (3aa);20d Typical
Procedure
According to the present results and previous re-
ports,15b,g,21 a possible mechanism is proposed in Scheme 5.
Diphenyl disulfide firstly reacts with iodine to generate
PhSI in situ, followed by a Friedel–Crafts reaction with sub-
strate 1a to produce intermediate 13. Intermediate 13 then
undergoes a dehydrogenation process to afford the product
3aa and hydrogen iodide. Hydrogen iodide can be readily
oxidized by hydrogen peroxide to yield iodine. In the io-
A 15-mL tube with a Teflon cap, equipped with a magnetic stirring
bar, was charged with substrate 1a (0.20 mmol), diphenyl disulfide
(0.10 mmol, 0.5 equiv), and I2 (20 mol%); H2O2 (2 equiv) and EtOH (2
mL) were then added sequentially. The tube was capped and stirred at
25 °C for 18 h, the crude mixture was diluted with EtOAc, and washed
with sat. aq Na2S2O3 solution (3 × 10 mL). The organic phase was dried
(MgSO4), filtered through a Celite pad, and washed with EtOAc. The
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filtrate was concentrated in vacuo, and the resulting residue was pu-
rified by column chromatography (hexane–EtOAc) to afford product
3aa as a light yellow solid; yield: 56.8 mg (92%).
1H NMR (500 MHz, CDCl3): δ = 8.09–8.06 (m, 2 H), 7.41–7.36 (m, 3 H),
7.34–7.31 (m, 1 H), 7.20–7.17 (m, 2 H), 6.99–6.97 (m, 2 H), 6.84 (d, J =
4.5 Hz, 1 H).
IR (ATR): 3072, 2930, 1576, 1432, 1330, 1028, 785 cm–1
.
13C NMR (125 MHz, CDCl3): δ = 152.9, 151.7, 134.5, 133.4, 132.2,
129.6, 128.5, 128.4, 127.5, 127.2, 117.9, 113.3, 107.2.
1H NMR (500 MHz, CDCl3): δ = 8.11–8.09 (m, 2 H), 7.41–7.38 (m, 3 H),
7.34–7.31 (m, 1 H), 7.23 (t, J = 7.5 Hz, 2 H), 7.14 (t, J = 7.5 Hz, 1 H),
7.08–7.06 (m, 2 H), 6.82 (d, J = 4.5 Hz, 1 H).
LRMS (EI, 70 eV): m/z (%) = 342 (48), 231 (8), 189 (5), 187 (100), 77
(12).
13C NMR (125 MHz, CDCl3): δ = 152.7, 151.5, 135.9, 133.6, 129.5,
HRMS (ESI): m/z [M + H]+ calcd for C17H12ClN2S2: 343.0125; found:
128.5, 128.2, 127.6, 126.2, 125.9, 118.1, 113.1, 107.8.
343.0110.
LRMS (EI, 70 eV): m/z (%) = 308 (65), 188 (12), 187 (100), 121 (10), 51
(6).
5-[(3,5-Dichlorophenyl)thio]-6-phenylimidazo[2,1-b]thiazole
(3af)
White solid; yield: 66.3 mg (88%).
6-Phenyl-5-(p-tolylthio)imidazo[2,1-b]thiazole (3ab)
Light yellow solid; yield: 60.6 mg (94%).
IR (ATR): 3012, 2973, 1550, 1531, 1493, 1318, 1179, 776, 703 cm–1
.
IR (ATR): 3075, 2952, 2918, 1550, 1497, 1434, 817, 784, 762 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.05 (dd, J = 5.3, 3.5 Hz, 2 H), 7.42–7.38
(m, 3 H), 7.36–7.33 (m, 1 H), 7.12 (t, J = 1.5 Hz, 1 H), 6.90–6.88 (m, 3
H).
13C NMR (125 MHz, CDCl3): δ = 153.7, 152.3, 139.9, 136.0, 133.1,
1H NMR (500 MHz, CDCl3): δ = 8.13–8.11 (m, 2 H), 7.41–7.38 (m, 3 H),
7.34–7.30 (m, 1 H), 7.03 (d, J = 8.0 Hz, 2 H), 6.98 (d, J = 8.0 Hz, 2 H),
6.80 (d, J = 4.5 Hz, 1 H), 2.27 (s, 3 H).
128.6, 127.5, 126.5, 123.6, 117.8, 113.7, 105.4.
13C NMR (125 MHz, CDCl3): δ = 152.4, 151.3, 136.2, 133.7, 132.2,
130.2, 128.5, 128.2, 127.6, 126.3, 118.1, 112.9, 108.5, 20.9.
LRMS (EI, 70 eV): m/z (%) = 376 (38), 231 (19), 188 (13), 187 (100), 77
(13).
LRMS (EI, 70 eV): m/z (%) = 322 (67), 188 (12), 187 (100), 135 (70), 77
(12).
HRMS (ESI): m/z [M + H]+ calcd for C17H11Cl2N2S2: 376.9735; found:
376.9731.
HRMS (ESI): m/z [M + H]+ calcd for C18H15N2S2: 323.0671; found:
323.0677.
5-[(3-Fluorophenyl)thio]-6-phenylimidazo[2,1-b]thiazole (3ag)
5-[(4-Methoxyphenyl)thio]-6-phenylimidazo[2,1-b]thiazole (3ac)
Light yellow solid; yield: 60.0 mg (92%).
Light yellow solid; yield: 64.1 mg (95%).
IR (ATR): 2975, 1552, 1403, 1185, 870, 761, 711 cm–1
.
IR (ATR): 2962, 2930, 1578, 1352, 1045, 752, 743 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.09–8.07 (m, 2 H), 7.42–7.38 (m, 3 H),
7.35–7.32 (m, 1 H), 7.21–7.17 (m, 1 H), 6.85–6.81 (m, 3 H), 6.77–6.74
(m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 164.4 (d, JC–F = 247.9 Hz, 1 C), 153.1,
151.8, 138.5 (d, JC–F = 7.3 Hz, 1 C), 133.4, 130.8 (d, JC–F = 8.4 Hz, 1 C),
128.5, 128.4, 127.6, 121.3 (d, JC–F = 3.0 Hz, 1 C), 118.0, 113.3, 113.2 (d,
JC–F = 23.6 Hz, 1 C), 112.8 (d, JC–F = 24.1 Hz, 1 C), 106.8.
1H NMR (500 MHz, CDCl3): δ = 8.16–8.14 (m, 2 H), 7.43–7.40 (m, 3 H),
7.35–7.32 (m, 1 H), 7.09–7.06 (m, 2 H), 6.82 (d, J = 4.5 Hz, 1 H), 6.80–
6.77 (m, 2 H), 3.74 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 158.7, 151.9, 151.1, 133.7, 128.6,
128.4, 128.1, 127.6, 126.2, 118.1, 115.2, 112.9, 109.5, 55.4.
LRMS (EI, 70 eV): m/z (%) = 338 (66), 188 (13), 187 (100), 152 (4), 77
(11).
LRMS (EI, 70 eV): m/z (%) = 326 (61), 231 (13), 188 (12), 187 (100), 89
(6).
HRMS (ESI): m/z [M + H]+ calcd for C18H15N2OS2: 339.0620; found:
339.0614.
HRMS (ESI): m/z [M + H]+ calcd for C17H12FN2S2: 327.0420; found:
327.0415.
5-[(3-Chlorophenyl)thio]-6-phenylimidazo[2,1-b]thiazole (3ad)
Light yellow solid; yield: 63.7 mg (93%).
5-[(2-Fluorophenyl)thio]-6-phenylimidazo[2,1-b]thiazole (3ah)
IR (ATR): 3098, 3056, 1528, 1472, 1013, 723, 691 cm–1
.
Light yellow solid; yield: 60.7 mg (93%).
IR (ATR): 2982, 1423, 1187, 875, 728 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.08–8.06 (m, 2 H), 7.41–7.37 (m, 3 H),
7.32 (t, J = 7.5 Hz, 1 H), 7.15– 7.09 (m, 2 H), 7.06 (d, J = 1.7 Hz, 1 H),
6.89 (dd, J = 7.5, 1.5 Hz, 1 H), 6.84 (d, J = 4.4 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 153.6, 152.2, 138.5, 135.8, 133.7,
130.9, 128.9, 128.8, 127.9, 126.8, 125.9, 124.2, 118.3, 113.7, 107.0.
1H NMR (500 MHz, CDCl3): δ = 8.10 (d, J = 7.6 Hz, 2 H), 7.45 (d, J = 4.5
Hz, 1 H), 7.40 (t, J = 7.6 Hz, 2 H), 7.33 (t, J = 7.3 Hz, 1 H), 7.16–7.11 (m,
1 H), 7.08–7.05 (m, 1 H), 6.95–6.92 (m, 1 H), 6.85 (d, J = 4.5 Hz, 1 H),
6.77 (t, J = 7.6 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 159.6 (d, JC–F = 243.6 Hz, 1 C), 153.3,
LRMS (EI, 70 eV): m/z (%) = 342 (48), 231 (13), 187 (100), 121 (6), 77
151.7, 133.4, 128.5, 128.3, 128.1 (d, JC–F = 2.0 Hz, 1 C), 128.0 (d, JC–F
=
(13).
7.4 Hz, 1 C), 127.6, 125.1 (d, JC–F = 3.4 Hz, 1 C), 123.0 (d, JC–F = 17.0 Hz,
1 C), 118.2, 116.0 (d, JC–F = 20.9 Hz, 1 C), 113.1, 105.8.
HRMS (ESI): m/z [M + H]+ calcd for C17H12ClN2S2: 343.0125; found:
343.0138.
LRMS (EI, 70 eV): m/z (%) = 326 (71), 231 (16), 188 (12), 187 (100),
121 (7).
5-[(4-Chlorophenyl)thio]-6-phenylimidazo[2,1-b]thiazole (3ae)
HRMS (ESI): m/z [M + H]+ calcd for C17H12FN2S2: 327.0420; found:
Light yellow solid; yield: 61.2 mg (90%).
327.0415.
IR (ATR): 3089, 3070, 1528, 1463, 1080, 809, 698 cm–1
.
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5-(Methylthio)-6-phenylimidazo[2,1-b]thiazole (3ai)20b
Light yellow solid; yield: 45.5 mg (92%).
IR (ATR): 3051, 2956, 2919, 1530, 1459, 1332, 723, 695 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.18 (d, J = 8.0 Hz, 2 H), 7.55 (d, J = 4.5
Hz, 1 H), 7.44 (t, J = 7.5 Hz, 2 H), 7.33 (t, J = 7.0 Hz, 1 H), 6.85 (d, J = 4.5
Hz, 1 H), 2.28 (s, 3 H).
1H NMR (500 MHz, CDCl3): δ = 8.44–8.43 (m, 1 H), 8.10–8.08 (m, 2 H),
7.47–7.44 (m, 2 H), 7.41–7.38 (m, 2 H), 7.34–7.30 (m, 1 H), 7.05–7.02
(m, 1 H), 6.87 (d, J = 4.5 Hz, 1 H), 6.79 (d, J = 8.1 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 159.2, 152.9, 151.9, 150.2, 137.4,
133.5, 128.5, 128.3, 127.6, 120.7, 119.8, 118.3, 113.2, 106.7.
.
LRMS (EI, 70 eV): m/z (%) = 309 (86), 231 (40), 188 (12), 187 (100), 78
(12).
HRMS (ESI): m/z [M + H]+ calcd for C16H12N3S2: 310.0467; found:
310.0463.
13C NMR (125 MHz, CDCl3): δ = 150.1, 150.0, 134.0, 128.3, 127.7,
127.3, 117.8, 112.7, 19.3.
LRMS (EI, 70 eV): m/z (%) = 246 (70), 231 (100), 187 (57), 115 (9), 89
(9).
5-(Pyridin-2-ylthio)-6-(p-tolyl)imidazo[2,1-b]thiazole (3bm)
Yellow solid; yield: 54.3 mg (84%).
IR (ATR): 3053, 2972, 1563, 1476, 1418, 1331, 812, 754, 709 cm–1
5-(Ethylthio)-6-phenylimidazo[2,1-b]thiazole (3aj)
.
Light yellow oil; yield: 46.4 mg (90%).
1H NMR (500 MHz, CDCl3): δ = 8.44–8.43 (m, 1 H), 7.99 (d, J = 8.0 Hz, 2
H), 7.47–7.43 (m, 2 H), 7.20 (d, J = 8.0 Hz, 2 H), 7.03 (dd, J = 7.4, 4.9 Hz,
1 H), 6.85 (d, J = 4.5 Hz, 1 H), 6.77 (d, J = 8.5 Hz, 1 H), 2.36 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 159.4, 153.1, 151.9, 150.2, 138.3,
137.5, 130.7, 129.3, 127.5, 120.7, 119.8, 118.3, 113.0, 106.2, 21.4.
IR (ATR): 3058, 2953, 2927, 1532, 1458, 1331, 701, 697 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.21 (dd, J = 8.0, 1.1 Hz, 2 H), 7.55 (d, J =
4.5 Hz, 1 H), 7.43–7.40 (m, 2 H), 7.33–7.29 (m, 1 H), 6.82 (d, J = 4.5 Hz,
1 H), 2.69 (q, J = 7.5 Hz, 2 H), 1.13 (t, J = 7.5 Hz, 3 H).
13C NMR (125 MHz, CDCl3): δ = 150.8, 150.2, 134.1, 128.3, 127.7,
127.4, 118.1, 112.6, 111.2, 30.8, 15.0.
LRMS (EI, 70 eV): m/z (%) = 323 (92), 290 (39), 202 (13), 201 (100), 78
(11).
HRMS (ESI): m/z [M + H]+ calcd for C17H14N3S2: 324.0624; found:
324.0621.
LRMS (EI, 70 eV): m/z (%) = 260 (52), 231 (100), 188 (53), 187 (43), 77
(12).
HRMS (ESI): m/z [M + H]+ calcd for C13H13N2S2: 261.0515; found:
261.0507.
6-(4-Methoxyphenyl)-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3cm)
6-Phenyl-5-(thiophen-2-ylthio)imidazo[2,1-b]thiazole (3ak)
Yellow solid; yield: 61.8 mg (91%).
IR (ATR): 3058, 2965, 1430, 1350, 1265, 1172, 1096, 874, 775 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.44–8.42 (m, 1 H), 8.05–8.03 (m, 2 H),
7.46–7.43 (m, 2 H), 7.04–7.01 (m, 1 H), 6.93–6.90 (m, 2 H), 6.84 (d, J =
4.5 Hz, 1 H), 6.77 (d, J = 8.0 Hz, 1 H), 3.81 (s, 3 H).
Light yellow solid; yield: 59.1 mg (94%).
IR (ATR): 3072, 2926, 1545, 1338, 1109, 753, 678 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.19 (dd, J = 7.5, 1.2 Hz, 2 H), 7.61 (d, J =
4.5 Hz, 1 H), 7.47–7.44 (m, 2 H), 7.38–7.35 (m, 1 H), 7.21 (dd, J = 5.3,
1.2 Hz, 1 H), 7.07 (dd, J = 3.6, 1.2 Hz, 1 H), 6.90–6.86 (m, 2 H).
.
.
13C NMR (125 MHz, CDCl3): δ = 159.8, 159.3, 152.8, 151.7, 150.1,
137.4, 128.9, 126.2, 120.6, 119.7, 118.2, 113.9, 112.8, 105.5, 55.3.
13C NMR (125 MHz, CDCl3): δ = 151.2, 151.0, 133.8, 133.6, 130.7,
128.5, 128.4, 128.2, 127.9, 127.7, 118.0, 113.0, 110.8.
LRMS (EI, 70 eV): m/z (%) = 339 (90), 261 (50), 218 (15), 217 (100), 78
(13).
HRMS (ESI): m/z [M + H]+ calcd for C17H14N3OS2: 340.0573; found:
340.0557.
LRMS (EI, 70 eV): m/z (%) = 314 (61), 281 (9), 187 (100), 71 (6).
HRMS (ESI): m/z [M + H]+ calcd for C15H11N2S3: 315.0079; found:
315.0072.
5-[(2-Methylfuran-3-yl)thio]-6-phenylimidazo[2,1-b]thiazole
(3al)
2-[5-(Pyridin-2-ylthio)imidazo[2,1-b]thiazol-6-yl]phenol (3dm)
White solid; yield: 55.4 mg (85%).
Light yellow solid; yield: 51.9 mg (83%).
IR (ATR): 3629, 2961, 1530, 1429, 1265, 1112, 842, 751 cm–1
.
IR (ATR): 3022, 2965, 1520, 1417, 1265, 1023, 745 cm–1
.
1H NMR (500 MHz, DMSO): δ = 8.40 (dd, J = 4.8, 0.9 Hz, 1 H), 8.01 (dd,
J = 8.0, 1.6 Hz, 1 H), 7.89 (d, J = 4.4 Hz, 1 H), 7.69–7.65 (m, 1 H), 7.47 (d,
J = 4.4 Hz, 1 H), 7.22–7.17 (m, 2 H), 7.02 (d, J = 8.0 Hz, 1 H), 6.92 (dd,
J = 8.0, 0.8 Hz, 1 H), 6.83–6.80 (m, 1 H).
13C NMR (125 MHz, DMSO): δ = 157.4, 156.3, 150.0, 149.9, 149.3,
137.9, 129.9, 127.4, 121.1, 120.0, 119.0, 118.8, 117.2, 116.9, 115.7,
105.9.
1H NMR (500 MHz, CDCl3): δ = 8.15 (dd, J = 8.3, 1.2 Hz, 2 H), 7.51 (d, J =
4.5 Hz, 1 H), 7.46–7.42 (m, 2 H), 7.37–7.33 (m, 1 H), 7.13 (d, J = 2.0 Hz,
1 H), 6.85 (d, J = 4.5 Hz, 1 H), 6.09 (d, J = 2.0 Hz, 1 H), 2.26 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 152.8, 150.8, 150.5, 141.0, 133.9,
128.4, 128.0, 127.9, 117.9, 113.3, 112.9, 110.8, 110.5, 12.0.
LRMS (EI, 70 eV): m/z (%) = 312 (65), 200 (60), 188 (13), 187 (100), 89
(8).
HRMS (ESI): m/z [M + H]+ calcd for C16H13N2OS2: 313.0464; found:
313.0465.
LRMS (EI, 70 eV): m/z (%) = 325 (100), 281 (32), 209 (19), 207 (58), 73
(28).
HRMS (ESI): m/z [M + H]+ calcd for C16H12N3OS2: 326.0416; found:
326.0420.
6-Phenyl-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole (3am)
Yellow solid; yield: 56.1 mg (91%).
IR (ATR): 3056, 2953, 2927, 1532, 1458, 1445, 1335, 701 cm–1
6-(4-Fluorophenyl)-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3em)
.
Yellow solid; yield: 60.6 mg (90%).
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IR (ATR): 2923, 1563, 1487, 1437, 1391, 1341, 1245, 1188, 819, 769
cm–1
HRMS (ESI): m/z [M + H]+ calcd for C16H11BrN3S2: 387.9572; found:
387.9572.
.
1H NMR (500 MHz, CDCl3): δ = 8.43 (d, J = 5.0 Hz, 1 H), 8.07 (dd, J = 8.5,
5.6 Hz, 2 H), 7.48–7.44 (m, 2 H), 7.08–7.03 (m, 3 H), 6.87 (d, J = 4.5 Hz,
1 H), 6.79 (d, J = 8.0 Hz, 1 H).
2-Methyl-6-phenyl-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3im)
13C NMR (125 MHz, CDCl3): δ = 162.8 (d, JC–F = 246.5 Hz, 1 C), 158.9,
151.9 (d, JC–F = 7.8 Hz, 1 C), 150.2, 137.4, 129.7 (d, JC–F = 3.2 Hz, 1 C),
129.4, 129.3, 120.7, 119.7, 118.3, 115.4 (d, JC–F = 21.4 Hz, 1 C), 113.2,
106.4.
Yellow solid; yield: 62.7 mg (91%).
IR (ATR): 3048, 2928, 1540, 1459, 1435, 1245, 1089, 751, 709, 686 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.44–8.42 (m, 1 H), 8.08–8.06 (m, 2 H),
7.46–7.42 (m, 1 H), 7.36 (t, J = 7.5 Hz, 2 H), 7.29 (t, J = 7.5 Hz, 1 H), 7.16
(d, J = 1.3 Hz, 1 H), 7.04–7.01 (m, 1 H), 6.76 (d, J = 8.0 Hz, 1 H), 2.39 (d,
J = 1.2 Hz, 3 H).
.
LRMS (EI, 70 eV): m/z (%) = 327 (79), 249 (33), 286 (15), 205 (100), 95
(13).
HRMS (ESI): m/z [M + H]+ calcd for C16H11FN3S2: 328.0373; found:
13C NMR (125 MHz, CDCl3): δ = 159.4, 151.5, 151.2, 150.1, 137.4,
328.0363.
133.6, 128.4, 128.1, 127.4, 127.3, 120.5, 119.7, 114.8, 106.1, 14.1.
LRMS (EI, 70 eV): m/z (%) = 323 (95), 290 (30), 202 (15), 201 (100), 77
(12).
HRMS (ESI): m/z [M + Na]+ calcd for C17H13N3NaS2: 346.0443; found:
346.0436.
6-(3-Fluorophenyl)-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3fm)
Yellow solid; yield: 55.8 mg (85%).
IR (ATR): 2935, 1486, 1393, 1237, 1102, 819, 769 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.42 (dd, J = 5.0, 1.0 Hz, 1 H), 7.90 (d, J =
7.5 Hz, 1 H), 7.85–7.82 (m, 1 H), 7.49–7.45 (m, 2 H), 7.35–7.31 (m, 1
H), 7.06–6.98 (m, 2 H), 6.89 (d, J = 4.5 Hz, 1 H), 6.80 (d, J = 8.5 Hz, 1 H).
2-Phenyl-3-(pyridin-2-ylthio)benzo[d]imidazo[2,1-b]thiazole
(3jm)
White solid; yield: 64.5 mg (89%).
13C NMR (125 MHz, CDCl3): δ = 162.9 (d, JC–F = 243.3 Hz), 158.5, 151.8,
151.3 (d, JC–F = 2.6 Hz), 150.2, 137.4, 135.7 (d, JC–F = 8.5 Hz), 129.9 (d,
IR (ATR): 3060, 2926, 1503, 1463, 1348, 754, 743 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.45 (d, J = 4.5 Hz, 1 H), 8.31–8.30 (m, 1
H), 8.09 (d, J = 7.8 Hz, 2 H), 7.68–7.66 (m, 1 H), 7.44–7.38 (m, 3 H),
7.34–7.28 (m, 3 H), 7.02 (dd, J = 7.0, 5.3 Hz, 1 H), 6.89 (d, J = 8.1 Hz, 1
H).
J = 8.3 Hz), 123.1 (d, JC–F = 2.9 Hz), 120.8, 119.9, 118.3, 115.0 (d, JC–F
21.1 Hz), 114.5 (d, JC–F = 23.1 Hz), 113.4, 107.3.
=
LRMS (EI, 70 eV): m/z (%) = 327 (72), 249 (34), 286 (13), 205 (100), 95
(15).
13C NMR (125 MHz, CDCl3): δ = 159.6, 153.6, 151.1, 150.2, 137.5,
133.5, 133.1, 130.2, 128.4, 128.4, 127.8, 126.4, 125.0, 124.0, 120.7,
120.0, 114.4, 109.0.
HRMS (ESI): m/z [M + H]+ calcd for C16H11FN3S2: 328.0373; found:
328.0369.
LRMS (EI, 70 eV): m/z (%) = 359 (100), 326 (24), 281 (93), 207 (45).
HRMS (ESI): m/z [M + H]+ calcd for C20H14N3S2: 360.0624; found:
360.0617.
6-(4-Chlorophenyl)-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3gm)
Yellow solid; yield: 62.2 mg (91%).
IR (ATR): 2091, 1545, 1479, 1454, 1397, 1318, 1135, 1013, 845, 763
6-Methyl-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole (3km)
cm–1
.
Light yellow solid; yield: 43.0 mg (87%).
1H NMR (500 MHz, CDCl3): δ = 8.44–8.42 (m, 1 H), 8.06–8.04 (m, 2 H),
7.49–7.45 (m, 2 H), 7.38–7.32 (m, 2 H), 7.07–7.04 (m, 1 H), 6.89 (d, J =
4.5 Hz, 1 H), 6.79 (d, J = 8.1 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 158.6, 151.9, 151.5, 150.2, 137.4,
134.1, 131.9, 128.8, 128.7, 120.8, 119.8, 118.3, 113.4, 106.8.
IR (ATR): 3055, 2928, 1460, 1439, 1335, 730, 691 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.41 (dd, J = 4.5, 1.0 Hz, 1 H), 7.49–7.45
(m, 1 H), 7.38 (d, J = 4.5 Hz, 1 H), 7.05–7.02 (m, 1 H), 6.83 (d, J = 4.5 Hz,
1 H), 6.68 (d, J = 8.0 Hz, 1 H), 2.44 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 159.4, 152.6, 151.2, 149.7, 137.0,
120.2, 119.3, 118.0, 112.1, 107.3, 13.8.
LRMS (EI, 70 eV): m/z (%) = 343 (95), 249 (34), 286 (13), 221 (100), 95
(15).
HRMS (ESI): m/z [M + H]+ calcd for C16H11ClN3S2: 344.0077; found:
344.0075.
LRMS (EI, 70 eV): m/z (%) = 247 (91), 214 (40), 169 (37), 125 (100), 78
(24).
HRMS (ESI): m/z [M + H]+ calcd for C11H10N3S2: 248.0311; found:
248.0315.
6-(4-Bromophenyl)-5-(pyridin-2-ylthio)imidazo[2,1-b]thiazole
(3hm)
2-Phenyl-3-(phenylthio)imidazo[1,2-a]pyridine (5aa)15c
Yellow solid; yield: 72.1 mg (93%).
Light yellow solid; yield: 55.0 mg (91%).
IR (ATR): 3057, 2936, 1527, 1470, 1437, 1318, 1245, 1142, 816, 726
IR (ATR): 3061, 2932, 1475, 1432, 1217, 1023, 776 cm–1
.
cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.26 (d, J = 7.0 Hz, 1 H), 8.22–8.20 (m, 2
H), 7.73 (d, J = 9.0 Hz, 1 H), 7.45–7.42 (m, 2 H), 7.39–7.35 (m, 1 H),
7.34–7.31 (m, 1 H), 7.20 (t, J = 7.5 Hz, 2 H), 7.12 (t, J = 7.5 Hz, 1 H),
7.01–6.99 (m, 2 H), 6.85 (t, J = 7.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 151.5, 147.2, 135.3, 133.5, 129.5,
128.7, 128.5, 128.5, 126.7, 126.1, 125.7, 124.6, 117.7, 113.1, 106.4.
1H NMR (500 MHz, CDCl3): δ = 8.43–8.42 (m, 1 H), 8.01–7.98 (m, 2 H),
7.52–7.45 (m, 4 H), 7.07–7.04 (m, 1 H), 6.89 (d, J = 4.5 Hz, 1 H), 6.79
(d, J = 8.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 158.5, 151.8, 151.5, 150.1, 137.3,
132.4, 131.5, 129.0, 122.4, 120.7, 119.7, 118.2, 113.3, 106.8.
LRMS (EI, 70 eV): m/z (%) = 389 (68), 387 (63), 265 (59), 230 (100).
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LRMS (EI, 70 eV): m/z (%) = 302 (83), 225 (23), 182 (13), 181 (100), 77
LRMS (EI, 70 eV): m/z (%) = 303 (83), 302 (15), 225 (81), 182 (18), 78
(9).
(100).
HRMS (ESI): m/z [M + H]+ calcd for C18H14N3S: 304.0903; found:
304.0905.
3-[(3,5-Dichlorophenyl)thio]-2-phenylimidazo[1,2-a]pyridine
(5af)
Yellow solid; yield: 63.5 mg (85%).
6-Methyl-2-phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine
IR (ATR): 3022, 2970, 1528, 1490, 1320, 1172, 769 cm–1
.
(5bm)
White solid; yield: 55.7 mg (88%).
IR (ATR): 2930, 1540, 1423, 1116, 824, 786 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.22 (d, J = 7.0 Hz, 1 H), 8.15–8.13 (m, 2
H), 7.76 (d, J = 9.0 Hz, 1 H), 7.47 –7.44 (m, 2 H), 7.41–7.36 (m, 2 H),
7.12 (t, J = 2.0 Hz, 1 H), 6.94–6.91 (m, 1 H), 6.84 (d, J = 2.0 Hz, 2 H).
13C NMR (125 MHz, CDCl3): δ = 152.4, 147.6, 139.3, 136.1, 133.0,
129.0, 128.6, 128.4, 127.3, 126.5, 124.3, 123.4, 118.0, 113.6, 104.1.
.
1H NMR (500 MHz, CDCl3): δ = 8.44 (d, J = 4.7 Hz, 1 H), 8.17 (d, J = 8.0
Hz, 2 H), 8.10 (s, 1 H), 7.64 (d, J = 9.0 Hz, 1 H), 7.42–7.37 (m, 3 H), 7.34
(t, J = 7.0 Hz, 1 H), 7.19 (d, J = 9.0 Hz, 1 H), 7.03–7.01 (m, 1 H), 6.60 (d,
J = 8.0 Hz, 1 H), 2.31 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 159.0, 151.3, 150.2, 146.4, 137.3,
133.5, 129.9, 128.5, 128.4, 128.3, 123.1, 122.3, 120.6, 119.4, 117.1,
104.9, 18.4.
LRMS (EI, 70 eV): m/z (%) = 370 (57), 225 (51), 182 (13), 181 (100), 78
(70).
HRMS (ESI): m/z [M + H]+ calcd for C19H13Cl2N2S: 371.0171; found:
371.0164.
LRMS (EI, 70 eV): m/z (%) = 317 (93), 284 (30), 239 (100), 207 (13), 63
(71).
2-Phenyl-3-(thiophen-2-ylthio)imidazo[1,2-a]pyridine (5ak)
HRMS (ESI): m/z [M + H]+ calcd for C19H16N3S: 318.1059; found:
Light yellow solid; yield: 56.7 mg (92%).
318.1060.
IR (ATR): 2930, 1537, 1426, 1332, 1108, 752 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.48 (d, J = 7.0 Hz, 1 H), 8.33–8.25 (m, 2
H), 7.66 (d, J = 9.0 Hz, 1 H), 7.49 (t, J = 7.5 Hz, 2 H), 7.40 (t, J = 7.5 Hz, 1
H), 7.30–7.27 (m, 1 H), 7.14 (d, J = 5.0 Hz, 1 H), 7.02 (d, J = 3.6 Hz, 1 H),
6.89 (t, J = 6.8 Hz, 1 H), 6.86–6.82 (m, 1 H).
6-Fluoro-2-phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine
(5cm)
Yellow solid; yield: 34.2 mg (53%).
IR (ATR): 2928, 1557, 1486, 1433, 1386, 1180, 820, 772 cm–1
.
13C NMR (125 MHz, CDCl3): δ = 150.2, 146.7, 133.6, 133.5, 130.1,
128.7, 128.7, 128.5, 128.0, 127.6, 126.6, 124.5, 117.8, 113.1, 109.3.
1H NMR (500 MHz, CDCl3): δ = 8.42–8.41 (m, 1 H), 8.24 (dd, J = 3.3, 2.6
Hz, 1 H), 8.16–8.14 (m, 2 H), 7.71 (dd, J = 9.5, 4.9 Hz, 1 H), 7.46–7.41
(m, 3 H), 7.38–7.35 (m, 1 H), 7.28–7.24 (m, 1 H), 7.06–7.03 (m, 1 H),
6.70 (d, J = 8.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 157.9, 153.9 (d, JC–F = 237.0 Hz), 152.6
(d, JC–F = 2.3 Hz), 150.4, 144.9, 137.4, 133.1, 128.8, 128.5, 128.3, 120.9,
LRMS (EI, 70 eV): m/z (%) = 308 (70), 275 (73), 182 (13), 181 (100).
HRMS (ESI): m/z [M + H]+ calcd for C17H13N2S2: 309.0515; found:
309.0509.
3-[(2-Methylfuran-3-yl)thio]-2-phenylimidazo[1,2-a]pyridine
(5al)
119.8, 118.7 (d, JC–F = 25.3 Hz), 118.3 (d, JC–F = 8.6 Hz), 111.6 (d, JC–F
=
41.3 Hz), 107.1.
Light yellow solid; yield: 54.0 mg (88%).
LRMS (EI, 70 eV): m/z (%) = 321 (15), 200 (13), 199 (100), 78 (9), 76
(11).
IR (ATR): 3021, 2963, 1522, 1420, 1264, 1017, 738 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.45–8.43 (m, 1 H), 8.26–8.24 (m, 2 H),
7.65 (dd, J = 9.0, 1.0 Hz, 1 H), 7.50–7.47 (m, 2 H), 7.41–7.38 (m, 1 H),
7.28–7.25 (m, 1 H), 7.09 (d, J = 1.9 Hz, 1 H), 6.91–6.88 (m, 1 H), 6.00
(d, J = 1.9 Hz, 1 H), 2.26 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 152.5, 149.9, 146.4, 141.0, 133.8,
128.8, 128.4, 128.4, 126.1, 124.4, 117.7, 113.0, 112.8, 110.0, 109.3,
12.0.
HRMS (ESI): m/z [M + H]+ calcd for C18H13FN3S: 322.0809; found:
322.0802.
8-Chloro-2-phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine
(5dm)
White solid; yield: 60.7 mg (90%).
IR (ATR): 2930, 1550, 1487, 1434, 1316, 778, 719 cm–1
.
LRMS (EI, 70 eV): m/z (%) = 306 (100), 273 (57), 195 (13), 194 (97), 78
(95).
HRMS (ESI): m/z [M + H]+ calcd for C18H15N2OS: 307.0900; found:
307.0886.
1H NMR (500 MHz, CDCl3): δ = 8.40–8.39 (m, 1 H), 8.24 (d, J = 7.0 Hz, 1
H), 8.21–8.19 (m, 2 H), 7.44–7.40 (m, 4 H), 7.37 (t, J = 7.5 Hz, 1 H),
7.04–7.02 (m, 1 H), 6.82 (t, J = 7.5 Hz, 1 H), 6.68 (d, J = 8.0 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 158.0, 152.1, 150.3, 144.7, 137.4,
132.9, 128.9, 128.7, 128.5, 125.8, 123.6, 123.5, 120.8, 119.8, 112.7,
107.6.
2-Phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine (5am)
White solid; yield: 55.0 mg (91%).
LRMS (EI, 70 eV): m/z (%) = 337 (89), 302 (28), 259 (61), 215 (100),
112 (70).
IR (ATR): 3563, 2948, 1543, 1467, 1387, 1331, 1132, 713, 683 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 8.41–8.40 (m, 1 H), 8.29 (dd, J = 7.0, 1.0
Hz, 1 H), 8.18 (d, J = 7.5 Hz, 2 H), 7.73 (dd, J = 9.0, 0.8 Hz, 1 H), 7.43–
7.32 (m, 5 H), 7.01–6.99 (m, 1 H), 6.88–6.85 (m, 1 H), 6.62 (dd, J = 8.0,
0.8 Hz, 1 H).
13C NMR (125 MHz, CDCl3): δ = 158.6, 151.5, 150.3, 147.4, 137.4,
133.4, 128.7, 128.5, 128.5, 126.9, 124.6, 120.7, 119.6, 117.8, 113.2,
105.5.
HRMS (ESI): m/z [M + H]+ calcd for C18H13ClN3S: 338.0513; found:
338.0508.
8-Bromo-2-phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine
(5em)
White solid; yield: 71.0 mg (93%).
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IR (ATR): 2980, 1533, 1490, 1387, 1344, 1188, 940, 785, 723 cm–1
.
HRMS (ESI): m/z [M + H]+ calcd for C13H12N3S: 242.0746; found:
242.0740.
1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 4.56 Hz, 1 H), 8.28 (d, J = 7.0
Hz, 1 H), 8.20 (d, J = 7.5 Hz, 2 H), 7.59 (d, J = 7.5 Hz, 1 H), 7.42–7.39 (m,
3 H), 7.36 (t, J = 7.2 Hz, 1 H), 7.02 (dd, J = 7.0, 4.9 Hz, 1 H), 6.75 (t, J =
7.0 Hz, 1 H), 6.66 (d, J = 8.0 Hz, 1 H).
6-Phenyl-5-(phenylselanyl)imidazo[2,1-b]thiazole (7)
Light yellow solid; yield: 62.8 mg (88%).
13C NMR (125 MHz, CDCl3): δ = 158.0, 152.0, 150.3, 145.2, 137.3,
132.9, 129.2, 128.9, 128.7, 128.4, 124.0, 120.8, 119.7, 113.1, 111.9,
107.6.
IR (ATR): 3052, 2976, 1489, 1437, 773, 751 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.09–8.07 (m, 2 H), 7.41–7.37 (m, 3 H),
7.31 (t, J = 7.5 Hz, 1 H), 7.20–7.14 (m, 5 H), 6.77 (d, J = 4.5 Hz, 1 H).
.
LRMS (EI, 70 eV): m/z (%) = 383 (100), 381 (97), 261 (88), 156 (78), 76
(29).
HRMS (ESI): m/z [M + H]+ calcd for C18H13BrN3S: 383.9993; found:
383.9982.
13C NMR (125 MHz, CDCl3): δ = 153.0, 151.7, 134.0, 131.5, 129.7,
128.7, 128.4, 128.1, 127.9, 126.8, 118.8, 112.5, 102.6.
LRMS (EI, 70 eV): m/z (%) = 356 (28), 276 (100), 275 (45), 137 (12), 77
(27).
HRMS (ESI): m/z [M + H]+ calcd for C17H13N2SSe: 356.9959; found:
356.9948.
[2-Phenyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridin-8-yl]metha-
nol (5fm)
Yellow solid; yield: 61.3 mg (90%).
IR (ATR): 3636, 2973, 1573, 1420, 1417, 1377, 783, 686 cm–1
2-Phenyl-3-(phenylselanyl)imidazo[1,2-a]pyridine (8)15c
.
Light yellow solid; yield: 61.0 mg (87%).
IR (ATR): 3049, 2973, 2930, 1540, 1423, 1116, 824, 786 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.34–8.33 (m, 1 H), 8.17 (dd, J = 5.2, 3.3
Hz, 2 H), 7.72–7.70 (m, 1 H), 7.45–7.42 (m, 2 H), 7.38–7.35 (m, 1 H),
7.31–7.27 (m, 1 H), 7.18–7.14 (m, 3 H), 7.11–7.09 (m, 2 H), 6.84–6.81
(m, 1 H).
1H NMR (500 MHz, CDCl3): δ = 8.40–8.39 (m, 1 H), 8.19 (d, J = 7.0 Hz, 1
H), 8.15–8.13 (m, 2 H), 7.40–7.37 (m, 3 H), 7.35–7.32 (m, 1 H), 7.27–
7.25 (m, 1 H), 7.02–6.99 (m, 1 H), 6.84 (t, J = 7.0 Hz, 1 H), 6.62 (d, J =
8.0 Hz, 1 H), 5.11 (s, 2 H).
13C NMR (125 MHz, CDCl3): δ = 158.8, 151.1, 150.6, 146.5, 137.7,
133.4, 130.5, 129.1, 128.9, 128.8, 124.2, 123.9, 121.1, 120.1, 113.6,
106.3, 62.4.
.
13C NMR (125 MHz, CDCl3): δ = 151.9, 147.8, 133.9, 131.0, 129.7,
128.8, 128.5, 128.4, 128.3, 126.7, 126.5, 125.7, 117.6, 113.0, 103.0.
LRMS (EI, 70 eV): m/z (%) = 333 (8), 331 (13), 253 (43), 209 (55), 207
(36).
HRMS (ESI): m/z [M + H]+ calcd for C19H16N3OS: 334.1009; found:
LRMS (EI, 70 eV): m/z (%) = 350 (35), 273 (11), 270 (100), 181 (13), 78
(59).
334.1009.
5-Amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(6-
phenylimidazo[2,1-b]thiazol-5-yl)thio]-1H-pyrazole-3-carboni-
trile (10)
8-Bromo-2-phenyl-3-(thiophen-2-ylthio)imidazo[1,2-a]pyridine
(5ek)
White solid; yield: 94.8 mg (86%).
White solid; yield: 68.7 mg (89%).
IR (ATR): 2928, 1540, 1480, 1334, 1198, 903, 744, 712 cm–1
1H NMR (500 MHz, CDCl3): δ = 8.48 (d, J = 6.5 Hz, 1 H), 8.29 (d, J = 8.0
Hz, 2 H), 7.54 (d, J = 7.5 Hz, 1 H), 7.49 (t, J = 7.5 Hz, 2 H), 7.41 (t, J = 7.5
Hz, 1 H), 7.16 (d, J = 5.3 Hz, 1 H), 7.02 (d, J = 3.6 Hz, 1 H), 6.89–6.82 (m,
1 H), 6.79 (t, J = 7.0 Hz, 1 H).
IR (ATR): 3430, 2954, 2261, 1529, 1169, 880, 769, 665 cm–1
.
.
1H NMR (500 MHz, CDCl3): δ = 8.02 (d, J = 4.5 Hz, 1 H), 7.98 (d, J = 7.5
Hz, 2 H), 7.64 (s, 2 H), 7.46 (t, J = 7.5 Hz, 2 H), 7.35 (t, J = 7.5 Hz, 1 H),
6.99 (d, J = 4.5 Hz, 1 H), 3.72 (s, 2 H).
13C NMR (125 MHz, CDCl3): δ = 152.1, 151.3, 149.7, 136.3, 135.0,
134.6 (q, JC–F = 34.4 Hz, 1 C), 134.0, 130.8, 128.7, 128.7, 128.5, 126.2 (q,
JC–F = 3.5 Hz, 2 C), 121.9 (q, JC–F = 272.3 Hz, 1 C), 119.0, 113.4, 113.0,
110.7, 96.4.
13C NMR (125 MHz, CDCl3): δ = 151.2, 144.8, 133.5, 133.1, 130.9,
129.3, 129.3, 129.2, 128.8, 128.7, 128.0, 124.2, 113.4, 112.3, 111.8.
LRMS (EI, 70 eV): m/z (%) = 386 (54), 307 (21), 262 (15), 261 (100), 76
(18).
HRMS (ESI): m/z [M + H]+ calcd for C17H12BrN2S2: 388.9605; found:
388.9591.
LRMS (EI, 70 eV): m/z (%) = 550 (21), 200 (100).
HRMS (ESI): m/z [M + H]+ calcd for C22H12Cl2F3N6S2: 550.9889; found:
550.9881.
5-Amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(2-
phenylimidazo[1,2-a]pyridin-3-yl)thio]-1H-pyrazole-3-carboni-
trile (11)
2-Methyl-3-(pyridin-2-ylthio)imidazo[1,2-a]pyridine (5gm)
Light yellow solid; yield: 41.5 mg (86%).
IR (ATR): 3058, 2951, 2919, 1545, 1459, 1439, 1383, 736, 687 cm–1
.
White solid; yield: 94.8 mg (87%).
1H NMR (500 MHz, CDCl3): δ = 8.45–8.34 (m, 1 H), 8.20 (d, J = 7.0 Hz, 1
H), 7.63 (d, J = 9.0 Hz, 1 H), 7.42–7.39 (m, 1 H), 7.32–7.29 (m, 1 H),
7.03–7.01 (m, 1 H), 6.86 (t, J = 7.0 Hz, 1 H), 6.51 (d, J = 8.0 Hz, 1 H),
2.57 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 159.0, 151.8, 150.0, 147.3, 137.1,
126.2, 124.4, 120.4, 119.3, 117.1, 112.7, 106.5, 14.0.
IR (ATR): 3428, 2960, 2259, 1530, 1227, 1170, 772 cm–1
.
1H NMR (500 MHz, DMSO): δ = 8.65 (d, J = 7.0 Hz, 1 H), 8.26–8.25 (m,
2 H), 8.21 (s, 2 H), 7.73 (d, J = 8.5 Hz, 1 H), 7.53–7.50 (m, 2 H), 7.46–
7.41 (m, 2 H), 7.13–7.10 (m, 1 H), 6.73 (s, 2 H).
13C NMR (125 MHz, DMSO): δ = 151.0, 148.6, 145.6, 135.8, 135.4,
133.4, 132.9 (q, JC–F = 33.6 Hz, 1 C), 132.5, 128.6, 128.3, 128.2, 126.7,
126.5 (q, JC–F = 3.4 Hz, 2 C), 125.2, 122.2 (q, JC–F = 272.4 Hz, 1 C), 117.2,
113.0, 112.5, 108.7, 90.8.
LRMS (EI, 70 eV): m/z (%) = 241 (100), 208 (52), 163 (65), 131 (25), 78
(70).
LRMS (EI, 70 eV): m/z (%) = 544 (20), 194 (100).
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HRMS (ESI): m/z [M + H]+ calcd for C24H14Cl2F3N6S: 545.0324; found:
545.0313.
(6) Budriesi, R.; Ioan, P.; Leoni, A.; Pedemonte, N.; Locatelli, A.;
Micucci, M.; Chiarini, A.; Galietta, L. J. V. J. Med. Chem. 2011, 54,
3885.
(7) (a) Belohlavek, D.; Malfertheiner, P. J. Scand. J. Gastroenterol.,
Suppl. 1979, 54, 44. (b) Boerner, R. J.; Moller, H. J. Psychophar-
makotherapie 1997, 4, 145. (c) Abe, Y.; Kayakiri, H.; Satoh, S.;
Inoue, T.; Sawada, Y.; Inamura, N.; Asano, M.; Aramori, I.;
Hatori, C.; Sawai, H.; Oku, T.; Tanaka, H. J. Med. Chem. 1998, 41,
4587. (d) Mizushige, K.; Ueda, T.; Yukiiri, K.; Suzuki, H. Cardio-
vasc. Drug. Rev. 2002, 20, 163. (e) Okubo, T.; Yoshikawa, R.;
Chaki, S.; Okuyama, S.; Nakazato, A. Bioorg. Med. Chem. 2004,
12, 423. (f) Mori, H.; Tanaka, M.; Kayasuga, R.; Masuda, T.; Ochi,
Y.; Yamada, H.; Kishikawa, K.; Ito, M.; Nakamura, T. Bone 2008,
43, 840.
(8) References for imidazo[2,1-b]thiazoles, see: (a) Kolavi, G.;
Hegde, V.; Khazi, I. A. Tetrahedron Lett. 2006, 47, 2811.
(b) Huang, G.; Sun, H.; Qiu, X.; Jin, C.; Lin, C.; Shen, Y.; Jiang, J.;
Wang, L. Org. Lett. 2011, 13, 5224. (c) Mukherjee, C.; Watanabe,
K. T.; Biehl, E. R. Tetrahedron Lett. 2012, 53, 6008.
5-Iodo-6-phenylimidazo[2,1-b]thiazole (12)
Yellow solid; yield: 65.1 mg (quant.).
IR (ATR): 3055, 2932, 1501, 1439, 760, 692, 587 cm–1
1H NMR (500 MHz, DMSO): δ = 8.18–7.77 (m, 3 H), 7.55–7.26 (m, 4 H).
13C NMR (125 MHz, DMSO): δ = 150.1, 147.7, 133.9, 128.3, 127.5,
.
126.8, 120.1, 113.7, 58.6.
LRMS (EI, 70 eV): m/z (%) = 326 (100), 200 (11), 198 (23), 128 (6), 89
(9).
HRMS (ESI): m/z [M + H]+ calcd for C11H8IN2S: 326.9447; found:
326.9441.
Acknowledgment
We gratefully acknowledge the NSFC (Nos. 21202121 and 21272178)
and Wenzhou University (No. wzucy034 and 3162014044) for finan-
cial support.
(9) References for imidazo[1,2-a]pyridine, see: (a) Chernyak, N.;
Gevorgyan, V. Angew. Chem. Int. Ed. 2010, 49, 2743.
(b) Kianmehr, E.; Ghanbari, M.; Niri, M. N.; Faramarzi, R. J. Comb.
Chem. 2010, 12, 41. (c) Wang, H. G.; Wang, Y.; Liang, D. D.; Liu, L.
Y.; Zhang, J. C.; Zhu, Q. Angew. Chem. Int. Ed. 2011, 50, 5678.
(d) Ma, L. J.; Wang, X. P.; Yu, W.; Han, B. Chem. Commun. 2011,
47, 11333. (e) Albrecht, Ł.; Albrecht, A.; Ransborg, L. K.;
Jørgensen, K. A. Chem. Sci. 2011, 2, 1273. (f) Sucunza, D.;
Samadi, A.; Chioua, M.; Silva, D. B.; Yunta, C.; Infantes, L.;
Carreiras, M. C.; Soriano, E.; Marco-Contelles, J. Chem. Commun.
2011, 47, 5043. (g) Yan, R. L.; Yan, H.; Ma, C.; Ren, Z. Y.; Gao, X.
A.; Huang, G. S.; Liang, Y. M. J. Org. Chem. 2012, 77, 2024.
(h) Guchhait, S. K.; Chandgude, A. L.; Priyadarshani, G. J. Org.
Chem. 2012, 77, 4438. (i) Nair, D. K.; Mobin, S. M.; Namboothiri,
I. N. N. Org. Lett. 2012, 14, 4580. (j) He, C.; Hao, J.; Xu, H.; Mo, Y.;
Liu, H.; Han, J.; Lei, A. Chem. Commun. 2012, 48, 11073. (k) Zeng,
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Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0034-1379941.
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