Visible Light Organic Photoredox-Catalyzed C-H Alkoxylation of Imidazopyridine with Alcohol

Article abstract of DOI:10.1021/acs.joc.7b02582

The visible light-mediated C-3 alkoxylation of imidazopyridines with alcohols has been achieved using rose bengal as an organic photoredox catalyst at room temperature. Widely abundant air acts as the terminal oxidant that avoids the use of a stoichiometric amount of peroxo compounds. A wide range of functional groups could be tolerated under the reaction conditions to produce C(sp²)-H alkoxylated products in high yields.

Full text of DOI:10.1021/acs.joc.7b02582

Note
Cite This: J. Org. Chem. 2017, 82, 13722−13727
pubs.acs.org/joc
Visible Light Organic Photoredox-Catalyzed C−H Alkoxylation of
Imidazopyridine with Alcohol
Golam Kibriya, Sadhanendu Samanta, Sourav Jana, Susmita Mondal, and Alakananda Hajra*
Department of Chemistry, Visva-Bharati (A Central University), Santiniketan 731235, India
*
S Supporting Information
ABSTRACT: The visible light-mediated C-3 alkoxylation of imidazopyridines with alcohols has been achieved using rose bengal
as an organic photoredox catalyst at room temperature. Widely abundant air acts as the terminal oxidant that avoids the use of a
stoichiometric amount of peroxo compounds. A wide range of functional groups could be tolerated under the reaction conditions
2
to produce C(sp )−H alkoxylated products in high yields.
visible light photoredox process has emerged as a
containing imidazo[1,2-a]pyridines have been used as selective
A
prominent tool in challenging chemical transformations in
and potent inhibitors of mycobacterial adenosine triphosphate
1
13a
recent years. The most common catalysts employed to
photoredox reactions are ruthenium and iridium polypyridyl
(ATP) synthesis and to measure the luciferase activity in
13b
living cells (Figure 1). However, only limited methods for
2
complexes in organic synthesis. However, these precious metal
catalysts are potentially toxic on a larger scale. Thus, major
3
efforts have been devoted to utilize organic dyes as metal-free
alternatives for their inexpensiveness, nontoxicity, synthetic
4
versatility, and better environmental perspective.
The development of an efficient method for the construction
of the C−O bond has gained much attention from the synthetic
organic chemists due to their wide occurrence in a large
number of biologically active molecules and in natural
5
products. Traditional methods for the synthesis of alkyl ethers
involve acid-catalyzed condensation of alcohols, coupling of
alkoxides and alkyl halides (Williamson synthesis), alkoxymer-
Figure 1. Examples of ether-based live cell substrates.
6
curation/demercuration of alkenes, etc. The use of toxic
the construction of imidazo[1,2-a]pyridine ethers exists. Very
recently, Zhong et al. reported a copper-catalyzed coupling
between 2-aminopyridine and 2-phenoxyacetophenone for the
metals and harsh reaction conditions are the disadvantages o7f
these methods in the formation of complex organic molecules.
Recently, a number of Pd- and Cu-catalyzed methods have
been developed as useful alternatives for the synthesis of alkyl
14
synthesis of imidazopyridine ethers. To the best of our
knowledge, there is no method for direct C−H alkoxylation on
imidazo[1,2-a]pyridine moieties. Recently, we have reported a
visible light-mediated C-3 thiocyanation of imidazoheterocycles
8
ethers. However, many of these methods still suffer from
limited substrate scopes and generate stoichiometric by-
products. Therefore, the development of straightforward and
environmentally benign methods for the synthesis of direct C−
15
using an eosin Y photocatalyst. On the basis of our previous
9
experiences and continuous efforts on the synthesis of
H alkoxylation is highly demanding in organic synthesis. As a
16
functionalized imidazoheterocycles herein, we report a direct
and environmentally benign method for the alkoxylation of
imidazopyridines using rose bengal as a photoredox catalyst
under ambient air at room temperature (Scheme 1).
consequence, there are only few methodologies that have been
reported recently to construct a new C−O bond through
10
photoredox catalysis.
However, the functionalization of imidazo[1,2-a]pyridines is
synthetically attractive as this heterocyclic scaffold is widely
We started our investigation by using 2-phenylimidazo[1,2-
a]pyridine (1a) and methanol as model substrates. Initially, we
carried out the reaction using 2 equiv of methanol as an
11
used in biological and medicinal fields. The nature of the
substituents present at the C-3 positions of imidazo[1,2-
a]pyridines regulates their pharmacological activities. Thus,
several methods have been developed for the synthesis and
Received: October 11, 2017
Published: November 27, 2017
12
functionalization of imidazoheterocycles. C-3 alkoxyl group-
©
2017 American Chemical Society
13722
DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727

The Journal of Organic Chemistry
Note
Scheme 1. C-3 Alkoxylation of Imidazopyridine
With the optimized reaction conditions in hand, we
investigated the scope of this alkoxylation reaction to show
the generality of this methodology (Scheme 2). At first, the
Scheme 2. C-3 Alkoxylation of Imidazopyridines with
a
Alcohols
alkoxylating reagent with eosin Y as an organo photocatalyst in
a CH CN solvent under a 20 W LED light. The results are
3
summarized in Table 1. To our delight, 2-phenyl-3-methoxy-
a
Table 1. Optimization of the Reaction Conditions
entry
photocatalyst
eosin Y
solvent
oxidant
yield (%)
1
2
3
4
5
6
7
8
9
CH CN
air
56
3
eosin Y
THF
air
59
eosin Y
toluene
1,2-DCE
DCM
air
45
eosin Y
air
38
eosin Y
air
trace
72
eosin Y
DMF
air
eosin Y
DMSO
1,4-dioxane
air
65
eosin Y
air
68
eosin Y
H O
2
air
trace
88
10
11
12
13
14
15
16
17
18
19
rose bengal
Ru(bpy) Cl ·6H O
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
air
air
62
3
2
2
Ir(ppy)3
air
68
rose bengal
rose bengal
rose bengal
rose bengal
O2
89
TBHP
K S O
72
75
2
2
8
b
trace
c
air
air
air
nd
d
rose bengal
rose bengal
55
e
30
a
Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol), photocatalyst (2
b
mol %), solvent (3 mL), 20 W LED bulb. Under an argon
atmosphere. Not detected. Irradiated with a green LED. Irradiated
c
d
e
with a blue LED.
imidazo[1,2-a]pyridine (3aa) was formed in 56% yield after 6 h
under ambient air (Table 1, entry 1). Inspired by this initial
result, we checked the effect of other solvents such as THF,
toluene, 1,2-DCE, DCM, DMF, DMSO, 1,4-dioxane, and H O
2
a
(
Table 1, entries 2−9). The best result was obtained in DMF
Reaction conditions: 1 (0.2 mmol), 2 (0.4 mmol), rose bengal (2 mol
b
c
%
), DMF (3 mL), 20 W LED bulb. 5 mmol scale. Reaction
yielding 72% of the desired product (Table 1, entry 6). The
screening of other photocatalysts such as rose bengal,
Ru(bpy) Cl ·6H O, and Ir(ppy) (Table 1, entries 10−12)
revealed that the alkoxylated product could be obtained in an
excellent yield by using rose bengal as a photocatalyst (Table 1,
d
continued for 9 h. Reaction completed in 4 h.
3
2
2
3
effect of the C-2 substituents on the phenyl ring was examined.
The imidazopyridine moiety with electron-donating substitu-
ents (−CH and −OCH ) on the phenyl ring afforded the
corresponding methoxylated products with excellent yields
(3ba and 3ca). Halogens were also well-tolerated under the
present reaction conditions (3da and 3ea). Strong electron-
withdrawing groups like −CF and −NO in the phenyl ring
also successfully gave the desired products without any
difficulties (3fa and 3ga). The hydroxy-substituted phenyl
ring of imidazo[1,2-a]pyridine also afforded the desired product
with a good yield (3ha). To our delight, the naphthyl- and
thiophene-substituted imidazo[1,2-a]pyridines furnished the
corresponding methoxylated products with high yields (3ia and
entry 10). In presence of molecular O , the yield of the
2
3
3
alkoxylated product did not improve much (Table 1, entry 13).
The use of other stoichiometric oxidants like TBHP and
K S O resulted in lower yields (Table 1, entries 14 and 15).
2
2
8
No product was formed in the absence of any photocatalyst
3
2
(
Table 1, entry 17). Moreover, the yield decreased significantly
when the reaction mixture was irradiated with a green LED and
blue LED for 12 h (Table 1, entries 18 and 19). Finally, the
optimized reaction conditions were obtained using 2 mol %
rose bengal in DMF by irradiation with a 20 W LED for 6 h
(Table 1, entry 10).
1
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DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727

The Journal of Organic Chemistry
ja). Also, imidazo[1,2-a]pyridines bearing a methyl sub-
Note
3
Scheme 4. Control Experiments
stituent on the pyridine ring at different positions efficiently
reacted with methanol to afford the desired products with good
yields (3ka and 3la). Next, to check the feasibility of alcohols, a
variety of primary and secondary alcohols were also tested as
alkoxylating agents, and in all of the cases, it afforded the
corresponding products in moderate to good yields (3kb−
3kp). Saturated alcohols like ethanol, propan-2-ol, 1-butanol, 2-
methylpropan-1-ol, and 3-methylbutan-1-ol smoothly reacted
with imidazopyridine (1k) and gave the desired products with
excellent yields (3kb−3kf). Notably, unsaturated alcohols such
as prop-2-en-1-ol, (E)-but-2-en-1-ol, (E)-3-phenylprop-2-en-1-
ol, and prop-2-yn-1-ol were also well-tolerated under the
present reaction conditions (3kg−3kj). Moreover, 2-bromoe-
thanol, a halogenated alcohol, was also found to participate
efficiently in this reaction (3kk). Surprisingly, when ethylene
glycol was used, only one hydroxyl group could be coupled
with 1k to afford the desired product in 81% yield (3kl). When
phenylmethanol, 1-tolylethanol, and furylmethanol were
employed, the corresponding products (3km−3ko) were
obtained in 75−85% yields. More interestingly, the natural
product, geraniol, also gave the alkoxylated product with an
excellent yield (3kp). However, the present methodology is not
applicable for the C-2 alkyl-substituted imidazo[1,2-a]pyridine,
simple imidazo[1,2-a]pyridine (1m and 1n), indole, imidazole,
sterically hindered tertiary alcohols, and aliphatic thiols.
Moreover, no alkoxylated product was obtained when 3-
phenylimidazo[1,2-a]pyridine was treated with methanol under
the standard conditions. This result illustrated that the reaction
selectively took place at the 3-position. The gram-scale reaction
of the present methodology was also performed in the usual
laboratory setup by taking 8-methyl-2-phenylimidazo[1,2-a]-
pyridine (1k) and methanol (2a). The corresponding
alkoxylated product (3ka) was obtained without a significant
decrease in yield, which signifies the practical applicability of
the present methodology.
found in the presence of benzoquinone (BQ) (Scheme 4, eq A,
ii)). These results signify that the reaction possibly proceeds
through a radical pathway. The reaction did not proceed at all
in the dark (Scheme 4, eq B), which strongly supports the
radical mechanism.
(
On the basis of our experimental observations and literature
4
f,10a
reports,
a plausible mechanistic pathway has been
proposed in Scheme 5. A single electron transfer (SET) from
Scheme 5. Probable Mechanistic Pathway
To extend the scope of our methodology, we carried out the
reaction with substituted benzo[d]imidazo[2,1-b]thiazoles
(
Scheme 3). To our delight, in all of the cases, the alkoxylated
imidazopyridine to the excited state of rose bengal (RB*)
afforded the imidazopyridine radical cation (A) and photo-
products were obtained in excellent yields (5aa−5ba).
•
−
catalyst radical anion (RB ). The resulting imidazopyridine
radical cation reacts with alcohol (ROH) to yield the alkoxide-
adduct radical (B). The photoredox cycle is completed by the
Scheme 3. C-3 Alkoxylation of Benzoimidazothiazoles with
Alcohols
a
•
−
reduction of O to O , which can abstract a proton to
2
2
•
•
produce HO . Hydrogen abstraction by HO from inter-
2
2
mediate B affords the alkoxylation product with H O , which is
2
2
detected by the starch−iodine test. Benzoquinone, which acts
as a scavenger of the superoxide radical anion, completely
4i
stopped the formation of the desired product.
In summary, we have developed a direct C-3 alkoxylation of
imidazopyridines using visible light organophotoredox catalysis
at ambient temperature. This methodology exploits a
commercially available organic dye (rose bengal) as the
inexpensive and nontoxic photocatalyst using air as the sole
green oxidant. A wide range of functional groups present in the
substrates could be tolerated under the mild reaction
conditions to provide the corresponding alkoxylated products
in moderate to excellent yields. To the best of our knowledge,
this is the first report for the direct C−H alkoxylation of
imidazopyridines. We believe this visible light-driven organo-
photocatalytic C−H alkoxylation strategy will add prospective
luminescence over expensive and toxic metal-catalyzed
reactions in organic synthesis.
a
Reaction conditions: 4 (0.2 mmol), 2 (0.4 mmol), rose bengal (2 mol
), DMF (3 mL), 20 W LED bulb.
%
To unravel the mechanistic path for the alkoxylation reaction
of imidazopyrines with alcohols, a few control experiments
were carried out as shown in Scheme 4. In the presence of
radical scavenger 2,2,6,6-tetramethylpiperidine-1-oxyl
(
(
TEMPO), only a trace amount of product was obtained
Scheme 4, eq A, (i)). No formation of the desired product was
1
3724
DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727

The Journal of Organic Chemistry
Note
3
-Methoxy-2-(4-(trifluoromethyl)phenyl)imidazo[1,2-a]pyridine
EXPERIMENTAL SECTION
■
1
(
3fa). Yellow oil (49 mg, 84% yield), R = 0.6 (PE/EA = 88:12). H
f
General Information. All reagents were purchased from
commercial sources and used without further purification. H NMR
spectra were determined on a 400 MHz spectrometer as solutions in
NMR (CDCl , 400 MHz): δ 8.42−8.41 (m, 1H), 8.08 (d, J = 8.4 Hz,
1
3
1
1
H), 7.80−7.76 (m, 1H), 7.72 (d, J = 8.0 Hz, 2H), 7.34 (d, J = 7.6 Hz,
13 1
H), 7.19−7.16 (m, 1H), 3.82 (s, 3H). C{ H} NMR (CDCl , 100
3
CDCl . Chemical shifts are expressed in parts per million (δ), and the
3
MHz): δ 166.4, 159.1, 158.8, 148.3, 138.3, 137.4, 133.5 (J
= 32
C−F
signals were reported as s (singlet), d (doublet), t (triplet), m
Hz), 128.9, 125.7 (JC−F = 8 Hz), 123.8 (JC−F = 284 Hz), 122.3, 120.2,
2.3. Anal. Calcd for C H F N O: C, 61.65; H, 3.79; N, 9.59%.
multiplet). Coupling constants (J) were given in Hz. 13C{ H} NMR
1
(
5
15
11
3
2
spectra were recorded at 100 MHz in a CDCl solution. Chemical
3
Found: C, 61.48; H, 3.72; N, 9.70%.
-Methoxy-2-(3-nitrophenyl)imidazo[1,2-a]pyridine (3ga). Brown
1
shifts are referenced to CDCl (δ = 7.26 for H and δ = 77.16 for
3
3
1
3
1
C{ H} NMR) as the internal standard. TLC was done on silica gel-
1
gummy mass (44 mg, 81% yield), R = 0.55 (PE/EA = 80:20). H
f
coated glass slides. All solvents were dried and distilled before use.
Commercially available solvents were freshly distilled before the
reaction. All reactions involving moisture-sensitive reactants were
executed using oven-dried glassware. All of the imidazoheterocycles
NMR (CDCl , 400 MHz): δ 8.85 (d, J = 2 Hz, 1H), 8.43−8.41 (m,
3
1
7
3
1
1
1
H), 8.38−8.36 (m, 1H), 8.29−8.27 (m, 1H), 7.82−7.78 (m, 1H),
.66 (t, J = 8.4 Hz, 1H), 7.38 (d, J = 8.0 Hz, 1H), 7.22−7.18 (m, 1H),
13
1
.85 (s, 3H). C{ H} NMR (CDCl , 100 MHz): δ 166.1, 158.3,
16b
3
were prepared by our reported method.
57.9, 148.7, 148.3, 138.5, 136.0, 134.2, 129.8, 126.4, 123.5, 122.6,
20.5, 52.5. Anal. Calcd for C H N O : C, 62.45; H, 4.12; N,
General Experimental Procedure for the Synthesis of
Compound 3aa−3kp. Imidazo[1,2-a]pyridine (1, 0.2 mmol),
alcohol (2, 0.4 mmol), rose bengal (2.0 mol %), and DMF (3.0
mL) were added to an oven-dried reaction vessel equipped with a
magnetic stir bar, and the reaction vessel was irradiated using a 20 W
LED bulb at room temperature under ambient air for 6 h. The
progress of the reaction was monitored by TLC. After completion of
the reaction, the reaction mixture was extracted with ethyl acetate. The
organic phase was dried over anhydrous Na SO and concentrated
14
11
3
3
5.61%. Found: C, 62.25; H, 4.17; N, 15.48%.
-(3-Methoxyimidazo[1,2-a]pyridin-2-yl)phenol (3ha). Yellow oil
2
1
(
41 mg, 85% yield), R = 0.6 (PE/EA = 82:18). H NMR (CDCl , 400
f
3
MHz): δ 13.67 (s, 1H), 8.43−8.42 (m, 1H), 7.79−7.75 (m, 1H),
7
7
(
.44−7.38 (m, 2H), 7.33 (d, J = 7.6 Hz, 1H), 7.20−7.17 (m, 1H),
13 1
.05−7.03 (m, 1H), 6.93−6.89 (m, 1H), 3.91 (s, 3H). C{ H} NMR
CDCl , 100 MHz): δ 165.3, 163.4, 162.8, 155.7, 148.3, 138.5, 134.6,
3
2
4
1
30.8, 122.7, 120.8, 119.2, 118.3, 116.2, 52.3. Anal. Calcd for
under reduced pressure to get the crude residue, which was purified by
column chromatography on silica gel (60−120 mesh) using petroleum
ether/ethyl acetate as an eluent to afford the pure alkoxylated products
C H N O : C, 69.99; H, 5.03; N, 11.66%. Found: C, 69.80; H,
1
4
12
2
2
5
.08; N, 11.78%.
-Methoxy-2-(naphthalen-2-yl)imidazo[1,2-a]pyridine (3ia).
3
(
3aa−3kp).
Brown gummy mass (45 mg, 83% yield), R = 0.5 (PE/EA =
f
3
-Methoxy-2-phenylimidazo[1,2-a]pyridine (3aa). Colorless oil
1
1
84:16). H NMR (CDCl , 400 MHz): δ 8.44−8.42 (m, 1H), 8.29 (s,
3
(
39 mg, 88% yield), R = 0.6 (PE/EA = 84:16). H NMR (CDCl , 400
f
3
1
1
H), 8.23−8.21 (m, 1H), 7.94−7.90 (m, 2H), 7.87 (d, J = 8.0 Hz,
H), 7.79−7.75 (m, 1H), 7.59−7.51 (m, 2H), 7.35 (d, J = 8.0 Hz,
MHz): δ 8.41−8.39 (m, 1H), 7.97−7.94 (m, 2H), 7.77−7.73 (m, 1H),
7
7
.53−7.51 (m, 1H), 7.48−7.45 (m, 2H), 7.29 (d, J = 8.0 Hz, 1H),
13
1
13 1
1H), 7.17−7.13 (m, 1H), 3.86 (s, 3H). C{ H} NMR (CDCl , 100
.15−7.12 (m, 1H), 3.80 (s, 3H). C{ H} NMR (CDCl , 100 MHz):
3
3
MHz): δ 167.0, 160.7, 159.5, 148.3, 138.2, 135.3, 132.8, 131.6, 130.6,
δ 166.9, 160.7, 159.5, 148.3, 138.1, 134.2, 132.2, 128.8, 128.6, 121.7,
19.6, 52.1. Anal. Calcd for C H N O: C, 74.98; H, 5.39; N, 12.49%.
1
29.4, 128.7, 128.2, 127.9, 126.8, 124.2, 121.8, 119.8, 52.2. Anal. Calcd
for C H N O: C, 78.81; H, 5.14; N, 10.21%. Found: C, 78.97; H,
.10; N, 10.30%.
3-Methoxy-2-(thiophen-2-yl)imidazo[1,2-a]pyridine (3ja). Brown
oil (40 mg, 86% yield), R = 0.5 (PE/EA = 88:12). H NMR (CDCl ,
1
14
12
2
Found: C, 74.82; H, 5.46; N, 12.59%.
-Methoxy-2-(p-tolyl)imidazo[1,2-a]pyridine (3ba). Yellow oil (41
18 14
2
5
3
1
mg, 86% yield), R = 0.6 (PE/EA = 88:12). H NMR (CDCl , 400
f
3
1
MHz): δ 8.39−8.38 (m, 1H), 7.85−7.83 (m, 2H), 7.75−7.70 (m, 1H),
f
3
4
00 MHz): δ 8.38−8.36 (m, 1H), 7.74−7.70 (m, 1H), 7.57−7.56 (m,
7
.28−7.25 (m, 3H), 7.12−7.09 (m, 1H), 3.79 (s, 3H), 2.41 (s, 3H).
1
3
1
1H), 7.54−7.53 (m, 1H), 7.29 (d, J = 8.0 Hz, 1H), 7.13−7.09 (m,
C{ H} NMR (CDCl , 100 MHz): δ 166.9, 160.6, 159.6, 148.2,
3
1
2
1
H), 3.81 (s, 3H). 13C{ H} NMR (CDCl , 100 MHz): δ 165.9, 158.8,
1
42.9, 138.0, 131.5, 129.5, 128.6, 121.5, 119.5, 52.0, 21.7. Anal. Calcd
3
54.8, 148.1, 141.1, 138.1, 132.8, 132.3, 128.2, 121.7, 120.0, 52.3. Anal.
Calcd for C H N OS: C, 62.59; H, 4.38; N, 12.16%. Found: C,
2.41; H, 4.44; N, 12.30%.
3-Methoxy-8-methyl-2-phenylimidazo[1,2-a]pyridine (3ka).
for C H N O: C, 75.61; H, 5.92; N, 11.76%. Found: C, 75.80; H,
15
14
2
5
.87; N, 11.89%.
-Methoxy-2-(4-methoxyphenyl)imidazo[1,2-a]pyridine (3ca).
12 10
2
6
3
1
Yellow oil (44 mg, 87% yield), R = 0.45 (PE/EA = 80:20). H
f
1
Brown oil (42 mg, 89% yield), R = 0.55 (PE/EA = 90:10). H
NMR (CDCl , 400 MHz): δ 8.40−8.38 (m, 1H), 7.94−7.92 (m, 2H),
f
3
NMR (CDCl , 400 MHz): δ 8.22−8.20 (m, 1H), 8.01−7.98 (m, 2H),
7
6
.76−7.71 (m, 1H), 7.27−7.25 (m, 1H), 7.13−7.09 (m, 1H), 6.99−
3
.96 (m, 2H), 3.88 (s, 3H), 3.80 (s, 3H). 13C{ H} NMR (CDCl , 100
1
7.55−7.50 (m, 2H), 7.48−7.44 (m, 2H), 7.06−7.03 (m, 1H), 3.78 (s,
3
1
3
1
H), 2.40 (s, 3H). 13C{ H} NMR (CDCl , 100 MHz): δ 166.8, 159.5,
MHz): δ 167.0, 163.0, 160.0, 159.8, 148.2, 138.0, 130.6, 126.9, 121.3,
19.4, 114.2, 55.6, 52.0. Anal. Calcd for C H N O : C, 70.85; H,
.55; N, 11.02%. Found: C, 70.70; H, 5.61, N, 10.98%.
-(4-Fluorophenyl)-3-methoxyimidazo[1,2-a]pyridine (3da). Yel-
3
58.1, 145.5, 138.9, 134.3, 132.0, 130.1, 128.7, 128.6, 121.8, 52.0, 17.5.
Anal. Calcd for C H N O: C, 75.61; H, 5.92; N, 11.76%. Found: C,
1
5
15 14 2 2
15 14
2
7
5.76; H, 5.99; N, 11.64%.
-Methoxy-7-methyl-2-phenylimidazo[1,2-a]pyridine (3la). Yel-
2
1
3
low oil (40 mg, 83% yield), R = 0.5 (PE/EA = 86:14). H NMR
f
1
low oil (40 mg, 84% yield), R = 0.5 (PE/EA = 84:16). H NMR
(
7
3
CDCl , 400 MHz): δ 8.40−8.38 (m, 1H), 7.99−7.96 (m, 2H), 7.77−
f
3
(
CDCl , 400 MHz): δ 8.25 (d, J = 4.8 Hz, 1H), 7.96−7.93 (m, 2H),
.72 (m, 1H), 7.28 (d, J = 8.0 Hz, 1H), 7.17−7.12 (m, 3H), 3.80 (s,
3
H). 13C{ H} NMR (CDCl , 100 MHz): δ 166.7, 165.3 (J
1
= 252
7.54−7.49 (m, 1H), 7.47−7.43 (m, 2H), 7.13 (s, 1H), 6.55 (d, J = 5.2
3
C−F
Hz, 1H), 3.80 (s, 3H), 2.38 (s, 3H). 13C{ H} NMR (CDCl
MHz): δ 166.9, 160.6, 159.5, 149.4, 147.9, 134.3, 132.1, 128.7, 128.5,
122.9, 120.3, 52.1, 21.1. Anal. Calcd for C15 O: C, 75.61; H, 5.92;
1
, 100
Hz), 159.3, 159.2, 148.2, 138.2, 130.9 (JC−F = 8 Hz), 130.4 (JC−F = 3
Hz), 121.8, 119.7, 116.0 (JC−F = 22 Hz), 52.2. Anal. Calcd for
C H FN O: C, 69.41; H, 4.58; N, 11.56%. Found: C, 69.62; H, 4.62;
3
H N
14 2
14
11
2
N, 11.46%.
-(4-Chlorophenyl)-3-methoxyimidazo[1,2-a]pyridine (3ea).
N, 11.76%. Found: C, 75.42; H, 5.97; N, 11.65%.
3-Ethoxy-8-methyl-2-phenylimidazo[1,2-a]pyridine (3kb). Yellow
oil (45 mg, 89% yield), R
2
1
1
Brown oil (45 mg, 87% yield), R = 0.6 (PE/EA = 86:14). H NMR
f
= 0.6 (PE/EA = 90:10). H NMR (CDCl
3
,
f
(
CDCl , 400 MHz): δ 8.40−8.39 (m, 1H), 7.92−7.89 (m, 2H), 7.77−
400 MHz): δ 8.19−8.18 (m, 1H), 8.02−7.99 (m, 2H), 7.53−7.49 (m,
3
7
.73 (m, 1H), 7.45−7.42 (m, 2H), 7.29 (d, J = 8.0 Hz, 1H), 7.16−7.13
2H), 7.48−7.44 (m, 2H), 7.04−7.01 (m, 1H), 4.25 (q, J = 14.4 Hz,
m, 1H), 3.80 (s, 3H). 13C{ H} NMR (CDCl , 100 MHz): δ 166.6,
1
13
1
(
2H), 2.38 (s, 3H), 1.14 (t, J = 7.2 Hz, 3H). C{ H} NMR (CDCl ,
3
3
1
5
59.3, 159.1, 148.3, 138.5, 138.2, 132.6, 129.9, 129.1, 122.0, 119.9,
2.2. Anal. Calcd for C H ClN O: C, 65.00; H, 4.29; N, 10.83%.
100 MHz): δ 166.0, 159.9, 158.7, 145.5, 138.6, 134.4, 131.9, 128.7,
128.6, 127.9, 121.6, 61.4, 17.5, 14.0. Anal. Calcd for C H N O: C,
14
11
2
16 16
2
Found: C, 65.18; H, 4.23; N, 10.95%.
76.16; H, 6.39; N, 11.10%. Found: C, 75.99; H, 6.35; N, 11.20%.
1
3725
DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727

The Journal of Organic Chemistry
Note
3
-Isopropoxy-8-methyl-2-phenylimidazo[1,2-a]pyridine (3kc).
Anal. Calcd for C H N O: C, 77.84; H, 5.38; N, 10.68%. Found: C,
77.64; H, 5.31; N, 10.77%.
17
14
2
1
Yellow oil (45 mg, 85% yield), R = 0.5 (PE/EA = 88:12). H NMR
f
(
CDCl , 400 MHz): δ 8.19−8.17 (m, 1H), 8.01−7.99 (m, 2H), 7.54−
3-(2-Bromoethoxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine
3
7
1
1
1
7
.50 (m, 2H), 7.48−7.44 (m, 2H), 7.04−7.01 (m, 1H), 5.20−5.11 (m,
(3kk). Brown gummy mass (57 mg, 86% yield), R = 0.45 (PE/EA =
f
1
13
1
H), 2.36 (s, 3H), 1.14 (d, J = 6.0 Hz, 6H). C{ H} NMR (CDCl ,
86:14). H NMR (CDCl , 400 MHz): δ 8.19−8.18 (m, 1H), 8.04−
3
3
00 MHz): δ 165.2, 160.2, 159.0, 145.4, 138.5, 134.4, 131.9, 128.7,
8.01 (m, 2H), 7.55−7.51 (m, 2H), 7.49−7.45 (m, 2H), 7.07−7.04 (m,
1H), 4.51 (t, J = 6.4 Hz, 1H), 3.41 (t, J = 6.4 Hz, 1H), 2.42 (s, 3H).
28.6, 127.5, 121.4, 69.4, 21.6, 17.5. Anal. Calcd for C H N O: C,
17
18
2
13
1
6.66; H, 6.81; N, 10.52%. Found: C, 76.86; H, 6.88; N, 10.39%.
-Butoxy-8-methyl-2-phenylimidazo[1,2-a]pyridine (3kd). Yellow
C{ H} NMR (CDCl , 100 MHz): δ 165.8, 158.7, 157.9, 145.3,
3
3
139.0, 134.0, 132.1, 128.8, 128.7, 128.6, 122.1, 64.5, 27.7, 17.5. Anal.
Calcd for C H BrN O: C, 58.02; H, 4.57; N, 8.46%. Found: C,
1
oil (50 mg, 90% yield), R = 0.6 (PE/EA = 88:12). H NMR (CDCl ,
f
3
16 15
2
4
2
2
00 MHz): δ 8.19−8.18 (m, 1H), 8.02−7.99 (m, 2H), 7.54−7.50 (m,
H), 7.48−7.44 (m, 2H), 7.04−7.01 (m, 1H), 4.18 (t, J = 6.8 Hz, 2H),
.38 (s, 3H), 1.52−1.45 (m, 2H), 1.25−1.15 (m, 2H), 0.84 (t, J = 7.6
58.18; H, 4.63; N, 8.32%.
2-((8-Methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)oxy)ethan-1-ol
(3kl). Brown gummy mass (43 mg, 81% yield), R = 0.45 (PE/EA =
f
13
1
1
Hz, 3H). C{ H} NMR (CDCl , 100 MHz): δ 166.1, 159.9, 158.6,
70:30). H NMR (CDCl , 400 MHz): δ 8.19−8.17 (m, 1H), 7.99−
3
3
1
1
45.5, 138.6, 134.4, 131.9, 128.7, 128.6, 127.8, 121.6, 65.2, 30.3, 19.0,
7.5, 13.7. Anal. Calcd for C H N O: C, 77.11; H, 7.19; N, 9.99%.
7.97 (m, 2H), 7.57−7.52 (m, 2H), 7.49−7.45 (m, 2H), 7.09−7.05 (m,
1H), 4.47−4.44 (m, 2H), 3.81−3.79 (m, 2H), 2.65 (br, 1H), 2.41 (s,
18
20
2
3H). 13C{ H} NMR (CDCl , 100 MHz): δ 166.3, 159.4, 157.9, 145.4,
1
Found: C, 77.27; H, 7.13; N, 10.08%.
-Isobutoxy-8-methyl-2-phenylimidazo[1,2-a]pyridine (3ke). Yel-
3
3
139.3, 134.1, 132.2, 129.0, 128.8, 128.6, 122.2, 67.0, 60.3, 17.6. Anal.
1
low oil (49 mg, 87% yield), R = 0.5 (PE/EA = 88:12). H NMR
Calcd for C H N O : C, 71.62; H, 6.01; N, 10.44%. Found: C,
f
16 16
2
2
(
7
CDCl , 400 MHz): δ 8.19−8.18 (m, 1H), 8.03−8.00 (m, 2H), 7.52−
71.44; H, 6.06; N, 10.34%.
3-(Benzyloxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine (3km).
Yellow oil (53 mg, 85% yield), R = 0.6 (PE/EA = 84:16). H NMR
3
.49 (m, 2H), 7.48−7.44 (m, 2H), 7.03−7.00 (m, 1H), 3.95 (d, J = 6.8
1
Hz, 2H), 2.39 (s, 3H), 1.84−1.77 (m, 1H), 0.78 (d, J = 6.8 Hz, 6H).
f
1
3
1
C{ H} NMR (CDCl , 100 MHz): δ 166.1, 159.8, 158.6, 145.5,
(CDCl , 400 MHz): δ 8.02−8.01 (m, 1H), 8.00−7.97 (m, 2H), 7.53−
3
3
1
38.6, 134.4, 131.9, 128.68, 128.66, 127.8, 121.6, 71.5, 27.4, 19.0, 17.5.
7.48 (m, 2H), 7.46−7.42 (m, 2H), 7.31−7.29 (m, 3H), 7.22−7.20 (m,
1
3
1
Anal. Calcd for C H N O: C, 77.11; H, 7.19; N, 9.99%. Found: C,
2H), 6.99−6.96 (m, 1H), 5.23 (s, 2H), 2.38 (s, 3H). C{ H} NMR
18
20
2
7
7.29; H, 7.15; N, 10.13%.
(CDCl
132.0, 128.8, 128.7, 128.6, 128.5, 128.4, 128.2, 121.8, 67.1, 17.5. Anal.
Calcd for C21 O: C, 80.23; H, 5.77; N, 8.91%. Found: C, 80.37;
H, 5.73; N, 9.04%.
8-Methyl-2-phenyl-3-(1-(p-tolyl)ethoxy)imidazo[1,2-a]pyridine
3
, 100 MHz): δ 166.1, 159.3, 158.1, 145.5, 138.7, 135.1, 134.4,
3
-(Isopentyloxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine (3kf).
1
Yellow oil (52 mg, 88% yield), R = 0.6 (PE/EA = 90:10). H NMR
H N
18 2
f
(
7
CDCl , 400 MHz): δ 8.20−8.18 (m, 1H), 8.02−7.99 (m, 2H), 7.53−
3
.49 (m, 2H), 7.48−7.44 (m, 2H), 7.04−7.01 (m, 1H), 4.21 (t, J = 6.8
1
Hz, 2H), 2.37 (s, 3H), 1.52−1.144 (m, 1H), 1.41−1.36 (m, 2H), 0.83
(3kn). Yellow oil (55 mg, 80% yield), R
NMR (CDCl , 400 MHz): δ 8.02−8.01 (m, 1H), 7.95−7.92 (m, 2H),
f
= 0.5 (PE/EA = 88:12). H
d, J = 6.4 Hz, 6H). 13C{ H} NMR (CDCl , 100 MHz): δ 166.1,
1
(
3
3
1
6
7
59.8, 158.6, 145.5, 138.6, 134.3, 131.9, 128.67, 128.63, 127.8, 121.6,
7.52−7.46 (m, 2H), 7.44−7.40 (m, 2H), 7.14−7.09 (m, 4H), 6.97−
3.9, 37.0, 24.8, 22.4, 17.5. Anal. Calcd for C H N O: C, 77.52; H,
6.94 (m, 1H), 6.02 (q, J = 13.2 Hz, 1H), 2.36 (s, 3H), 2.33 (s, 3H),
19
22
2
1.41 (d, J = 6.4 Hz, 3H). 13C{ H} NMR (CDCl
1
, 100 MHz): δ 165.1,
.53; N, 9.52%. Found: C, 77.39; H, 7.60; N, 9.41%.
-(Allyloxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine (3kg).
Brown gummy mass (46 mg, 87% yield), R = 0.6 (PE/EA =
3
3
159.8, 158.7, 145.5, 138.5, 137.8, 137.6, 134.4, 131.9, 129.2, 128.6,
127.5, 126.4, 125.4, 121.4, 73.7, 21.7, 21.2, 17.5. Anal. Calcd for
f
1
8
8
1
4
6:14). H NMR (CDCl , 400 MHz): δ 8.19−8.18 (m, 1H), 8.02−
C H N O: C, 80.67; H, 6.48; N, 8.18%. Found: C, 80.82; H, 6.42; N,
23 22 2
3
.00 (m, 2H), 7.54−7.50 (m, 2H), 7.48−7.44 (m, 2H), 7.05−7.02 (m,
H), 5.84−5.74 (m, 1H), 5.27−5.21 (m, 1H), 5.20−5.17 (m, 1H),
8.07%.
3-(Furan-2-ylmethoxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine
13
1
(
3ko). Brown gummy mass (46 mg, 75% yield), R = 0.6 (PE/EA =
.70−4.68 (m, 2H), 2.39 (s, 3H). C{ H} NMR (CDCl , 100 MHz):
f
3
1
9
7
1
0:10). H NMR (CDCl , 400 MHz): δ 8.05−8.04 (m, 1H), 7.98−
δ 165.9, 159.4, 158.3, 145.4, 138.7, 134.3, 132.0, 131.4, 128.7, 128.6,
28.2, 121.8, 119.2, 66.0, 17.5. Anal. Calcd for C H N O: C, 77.25;
3
.95 (m, 2H), 7.51−7.49 (m, 2H), 7.46−7.42 (m, 2H), 7.38−7.37 (m,
H), 7.01−6.98 (m, 1H), 6.37 (d, J = 3.2 Hz, 1H), 6.35−6.33 (m,
1
17
16
2
H, 6.10; N, 10.60%. Found: C, 77.06; H, 6.15; N, 10.48%.
1
3
1
(
E)-3-(But-2-en-1-yloxy)-8-methyl-2-phenylimidazo[1,2-a]-
1H), 5.20 (s, 2H), 2.38 (s, 3H). C{ H} NMR (CDCl , 100 MHz): δ
3
pyridine (3kh). Brown gummy mass (47 mg, 85% yield), R = 0.6 (PE/
EA = 86:14). H NMR (CDCl , 400 MHz): δ 8.19−8.17 (m, 1H),
165.9, 158.0, 145.5, 143.4, 138.8, 134.4, 132.0, 130.2, 129.0, 128.7,
128.6, 128.4, 121.8, 111.4, 110.7, 58.5, 17.5. Anal. Calcd for
f
1
3
8
7
2
.01−7.99 (m, 2H), 7.53−7.49 (m, 2H), 7.47−7.43 (m, 2H), 7.04−
.01 (m, 1H), 5.75−5.69 (m, 1H), 5.46−5.42 (m, 1H), 4.64−4.62 (m,
C H N O : C, 74.98; H, 5.30; N, 9.20%. Found: C, 74.79; H,
19 16 2 2
5.37; N, 9.32%.
13
1
H), 2.38 (s, 3H), 1.68−1.66 (m, 3H). C{ H} NMR (CDCl , 100
(E)-3-((3,7-Dimethylocta-2,6-dien-1-yl)oxy)-8-methyl-2-
phenylimidazo[1,2-a]pyridine (3kp). Brown gummy mass (58 mg,
3
MHz): δ 165.9, 159.7, 158.4, 145.4, 138.7, 134.4, 132.3, 131.9, 128.7,
28.6, 128.0, 124.4, 121.6, 66.0, 17.9, 17.5. Anal. Calcd for
C H N O: C, 77.67; H, 6.52; N, 10.06%. Found: C, 77.82; H,
1
1
80% yield), R
f
= 0.5 (PE/EA = 90:10). H NMR (CDCl
3
, 400 MHz):
δ 8.19−8.18 (m, 1H), 8.01−7.98 (m, 2H), 7.53−7.49 (m, 2H), 7.47−
7.43 (m, 2H), 7.04−7.01 (m, 1H), 5.23−5.19 (m, 1H), 5.09−5.04 (m,
1H), 4.71 (d, J = 7.2 Hz, 2H), 2.38 (s, 3H), 2.09−2.03 (m, 2H), 2.01−
18
18
2
6
.46; N, 10.16%.
-(Cinnamyloxy)-8-methyl-2-phenylimidazo[1,2-a]pyridine (3ki).
3
1
3
1
Brown gummy mass (59 mg, 87% yield), R = 0.5 (PE/EA = 84:16).
1.97 (m, 2H), 1.66 (s, 3H), 1.63 (s, 3H), 1.59 (s, 3H). C{ H} NMR
(CDCl , 100 MHz): δ 166.1, 159.8, 158.5, 145.5, 143.3, 138.6, 134.4,
32.0, 131.9, 128.6, 127.9, 125.1, 123.8, 121.6, 117.5, 62.1, 39.6, 26.3,
5.8, 17.8, 17.5, 16.5. Anal. Calcd for C H N O: C, 79.96; H, 7.83;
f
1
H NMR (CDCl , 400 MHz): δ 8.12−8.11 (m, 1H), 8.04−8.02 (m,
3
3
1
2
2
6
2
1
1
8
H), 7.53−7.45 (m, 4H), 7.35−7.27 (m, 5H), 6.96−6.93 (m, 1H),
.57 (d, J = 16.0 Hz, 1H), 6.17−6.10 (m, 1H), 4.87−4.85 (m, 1H),
24 28
2
.40 (s, 3H). 13C{ H} NMR (CDCl , 100 MHz): δ 165.9, 159.5,
1
N, 7.77%. Found: C, 80.13; H, 7.88; N, 7.63%.
-Methoxy-2-phenylbenzo[d]imidazo[2,1-b]thiazole (5aa). Yel-
3
3
58.3, 145.5, 138.7, 136.2, 135.0, 134.3, 132.0, 128.76, 128.71, 128.2,
28.1, 126.7, 122.2, 121.7, 65.8, 17.5. Anal. Calcd for C H N O: C,
1
low oil (40 mg, 72% yield), R
(CDCl , 400 MHz): δ 7.78−7.76 (m, 1H), 7.75−7.71 (m, 2H), 7.43−
7.37 (m, 4H), 7.33−7.28 (m, 1H), 7.25−7.20 (m, 1H), 3.43 (s, 3H).
= 0.6 (PE/EA = 90:10). H NMR
23
20
2
f
1.15; H, 5.92; N, 8.23%. Found: C, 81.32; H, 5.88; N, 8.10%.
-Methyl-2-phenyl-3-(prop-2-yn-1-yloxy)imidazo[1,2-a]pyridine
3kj). Brown gummy mass (41 mg, 78% yield), R = 0.6 (PE/EA =
3
8
13
1
(
C{ H} NMR (CDCl , 100 MHz): δ 173.2, 167.3, 135.3, 130.9,
f
3
1
9
3:7). H NMR (CDCl , 400 MHz): δ 8.21−8.19 (m, 1H), 8.03−8.00
129.8, 128.7, 127.5, 126.8, 126.5, 126.1, 123.5, 113.8, 103.9, 52.9. Anal.
Calcd for C H N OS: C, 68.55; H, 4.31; N, 9.99%. Found: C, 68.77;
3
(
4
m, 2H), 7.55−7.50 (m, 2H), 7.49−7.45 (m, 2H), 7.06−7.03 (m, 1H),
16
12
2
.83 (d, J = 2.4 Hz, 2H), 2.47 (t, J = 2.4 Hz, 1H), 2.43 (s, 3H).
H, 4.25; N, 9.87%.
3-Ethoxy-2-phenylbenzo[d]imidazo[2,1-b]thiazole (5ab). Yellow
1
3
1
C{ H} NMR (CDCl , 100 MHz): δ 165.7, 158.3, 157.5, 145.4,
3
1
1
39.0, 134.3, 132.1, 128.9, 128.7, 128.6, 122.1, 75.4, 74.6, 52.4, 17.5.
oil (46 mg, 78% yield), R = 0.55 (PE/EA = 90:10). H NMR (CDCl ,
f
3
1
3726
DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727

The Journal of Organic Chemistry
Note
4
4
1
1
1
4
00 MHz): δ 7.78−7.76 (m, 1H), 7.75−7.72 (m, 2H), 7.42−7.38 (m,
(6) (a) Feuer, H.; Hooz, J. Methods of Formation of the Ether
Linkage. In The Chemistry of the Ether Linkage; Patai, S., Ed.; Wiley:
New York, 1967; pp 445−498. (b) Williamson, A. W. J. Chem. Soc.
1852, 4, 229.
(7) Maier, T. C.; Fu, G. C. J. Am. Chem. Soc. 2006, 128, 4594.
(8) (a) Torraca, K. E.; Huang, X.; Parrish, C. A.; Buchwald, S. L. J.
Am. Chem. Soc. 2001, 123, 10770. (b) Newhouse, T.; Baran, P. S.
Angew. Chem., Int. Ed. 2011, 50, 3362. (c) Beccalli, E. M.; Broggini, G.;
Martinelli, M.; Sottocornola, S. Chem. Rev. 2007, 107, 5318. (d) Stahl,
S. S.; Labinger, J. A.; Bercaw, J. E. Angew. Chem., Int. Ed. 1998, 37,
2180. (e) Desai, L. V.; Malik, H. A.; Sanford, M. S. Org. Lett. 2006, 8,
1141.
H), 7.32−7.28 (m, 1H), 7.24−7.20 (m, 1H), 3.68−3.61 (m, 2H),
.28 (t, J = 7.2 Hz, 3H). 13C{ H} NMR (CDCl , 100 MHz): δ 173.5,
1
3
66.9, 135.8, 131.0, 129.7, 128.7, 127.4, 126.8, 126.6, 126.1, 123.4,
13.8, 103.8, 61.2, 15.4. Anal. Calcd for C H N OS: C, 69.36; H,
17
14
2
.79; N, 9.52. Found: C, 69.17; H, 4.73; N, 9.65%.
,6-Dimethoxy-2-phenylbenzo[d]imidazo[2,1-b]thiazole (5ba).
Yellow gummy mass (46 mg, 75% yield), R = 0.5 (PE/EA =
3
f
1
86:14). H NMR (CDCl , 400 MHz): δ 7.67 (d, J = 8.8 Hz, 1H),
3
7
.55−7.52 (m, 2H), 7.43−7.39 (m, 1H), 7.31−7.28 (m, 2H), 7.12 (d, J
=
2.8 Hz, 1H), 6.97−6.95 (m, 1H), 4.07 (s, 3H), 3.82 (s, 3H).
1
3
1
C{ H} NMR (CDCl , 100 MHz): δ 165.8, 164.7, 156.7, 146.1,
3
1
35.6, 131.5, 130.2, 129.3, 128.9, 128.5, 122.3, 114.3, 104.7, 55.8, 55.5.
(9) (a) Chen, F. J.; Zhao, S.; Hu, F.; Chen, K.; Zhang, Q.; Zhang, S.
Q.; Shi, B. F. Chem. Sci. 2013, 4, 4187. (b) Jiang, T. S.; Wang, G. W. J.
Org. Chem. 2012, 77, 9504.
Anal. Calcd for C H N O S: C, 65.79; H, 4.55; N, 9.03%. Found: C,
17
14
2
2
65.99; H, 4.61; N, 8.90%.
(10) (a) Zheng, Y. W.; Ye, P.; Chen, B.; Meng, Q. Y.; Feng, K.;
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.7b02582.
Wang, W.; Wu, L. Z.; Tung, C. H. Org. Lett. 2017, 19, 2206. (b) Yi, H.;
Niu, L.; Song, C.; Li, Y.; Dou, B.; Singh, A. K.; Lei, A. Angew. Chem.,
Int. Ed. 2017, 56, 1120.
■
*
S
(11) (a) Enguehard-Gueiffier, C.; Gueiffier, A. Mini-Rev. Med. Chem.
2
007, 7, 888. (b) Baviskar, A. T.; Amrutkar, S. M.; Trivedi, N.;
Chaudhary, V.; Nayak, A.; Guchhait, S. K.; Banerjee, U. C.; Bharatam,
P. V.; Kundu, C. N. ACS Med. Chem. Lett. 2015, 6, 481.
Starch−idodine test for the detection of hydrogen
1
13
1
peroxide and scanned copies of H and C{ H} NMR
spectra of the synthesized compounds (PDF)
(12) (a) Bagdi, A. K.; Santra, S.; Monir, K.; Hajra, A. Chem. Commun.
2
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AUTHOR INFORMATION
Corresponding Author
E-mail: alakananda.hajra@visva-bharati.ac.in.
■
*
ORCID
Sadhanendu Samanta: 0000-0003-2215-9189
Susmita Mondal: 0000-0002-8795-942X
Alakananda Hajra: 0000-0001-6141-0343
́
(h) Stasyuk, A. J.; Banasiewicz, M.; Cyranski, M. K.; Gryko, D. T. J.
Org. Chem. 2012, 77, 5552. (i) Sun, P.; Jiang, M.; Wei, W.; Min, Y.;
Zhang, W.; Li, W.; Yang, D.; Wang, H. J. Org. Chem. 2017, 82, 2906.
(13) (a) Tantry, S. J.; Markad, S. D.; Shinde, V.; Bhat, J.;
Balakrishnan, G.; Gupta, A. K.; Ambady, A.; Raichurkar, A. V.;
Kedari, C.; Sharma, S.; Mudugal, N. V.; Narayan, A.; Kumar, C. N. N.;
Nanduri, R.; Bharath, S.; Reddy, J.; Panduga, V.; Prabhakar, K. R.;
Kandaswamy, K.; Saralaya, R.; Kaur, P.; Dinesh, N.; Guptha, S.; Rich,
K.; Murray, D.; Plant, H.; Preston, M.; Ashton, H.; Plant, D.; Walsh, J.;
Alcock, P.; Naylor, K.; Collier, M.; Whiteaker, J.; McLaughlin, R. E.;
Mallya, M.; Panda, M.; Rudrapatna, S.; Ramachandran, V.; Shandil, R.
K.; Sambandamurthy, V. K.; Mdluli, K.; Cooper, C. B.; Rubin, H.;
Yano, T.; Iyer, P. S.; Narayanan, S.; Kavanagh, S.; Mukherjee, K.;
Balasubramanian, V.; Hosagrahara, V. P.; Solapure, S.; Ravishankar, S.;
Shahul, H. P. J. Med. Chem. 2017, 60, 1379. (b) Coutant, E. P.; Janin,
Y. L. Chem. - Eur. J. 2015, 21, 17158.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
A.H. acknowledges the financial support from CSIR, (Grant no.
2(0307)/17/EMR-II). S.S. thanks UGC-New Delhi (UGC-
SRF) and S.M. thanks CSIR-New Delhi (CSIR-SRF) for their
fellowships. We are thankful to Dr. Murali Mohan Guru for the
helpful discussion.
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DOI: 10.1021/acs.joc.7b02582
J. Org. Chem. 2017, 82, 13722−13727