Tert-Butyl nitrite mediated azo coupling between anilines and imidazoheterocycles

Article abstract of DOI:10.1039/c6ra03070j

A ^tBuONO mediated practical and efficient method for the synthesis of azo imidazoheterocycles with broad functionalities has been achieved by the reaction between imidazoheterocycles and anilines at room temperature in goods yields. Azo indoliz

Full text of DOI:10.1039/c6ra03070j

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tert-Butyl nitrite mediated azo coupling between anilines and
imidazoheterocycles
Received 00th January 20xx,
Accepted 00th January 20xx
Amrita Chakraborty, Sourav Jana, Golam Kibriya, Amrita Dey and Alakananda Hajra*
A tBuONO mediated practical and efficient method for the synthesis of azo imidazoheterocycles with broad functionalities
has been achieved by the reaction between imidazoheterocycles and anilines at room temperature in goods yields. Azo
indolizines were also prepared employing this methodology. Mild reaction conditions, tolerance of wide functionalities,
operational simplicity and easy purification of products are the notable advantages of the current protocol.
DOI: 10.1039/x0xx00000x
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heterocycle. Imidazo[1,2-a]pyridine derivatives are also found
to be useful in material sciences.8 Accordingly, much efforts
have been made for the synthesis and functionalization of
imidazopyridine scaffold.9 For the last few years our group is
also actively engaged in developing strategies for synthesis10
and functionalization of imidazoheterocycles.11
Introduction
Azoheterocycles are well known for their uses as organic
dyestuffs, pharmaceutical agents and food additives.1 Besides
traditional utilities, these scaffolds are successfully employed
as photodissociable ligands in molecular switches and
machines owing to their light driven cis/trans isomerisation2
(Fig. 1). A few azoheterocycles exhibit potential role in various
fields of electronic industry, namely, non-linear optics,3 liquid
crystal technology4 and photodynamic therapy.5 Due to
diverse applications of these compounds, continuous efforts
have been made to device new synthetic methods for
azoheterocyclic compounds.1a,2a,6
Based on our experiences we envisioned that incorporation
of azo functionality in the imidazo[1,2-a]pyridine ring could
impart marked biological properties as well as
photoresponsive soft materials based applications. Generally
azoimidazo[1,2-a]pyridines are synthesized through diazo
coupling using conc. HCl and NaNO2.6e Herein, we report a
straightforward and environmentally benign protocol for the
synthesis of azoimidazo[1,2-a]pyridines by the reaction
t
between anilines and imidazo[1,2-a]pyridines using BuONO in
EtOH at room temperature (Scheme 1).
Scheme 1 Synthesis of (E)-3-(Aryldiazenyl)imidazo[1,2-a]pyridines.
Fig 1. Important azoheteroarene scaffolds
Results and discussion
Imidazo[1,2-a]pyridine moiety displays an extensive array of
biological activities such as antitumor, antiparasitic, anti-
inflammatory, antiviral, hypnotic, analgesic, antipyretic, etc.7
Some marketed drugs like olprinone, alpidem, zolpidem,
saripidem etc. contain this fused bicyclic 5–6 nitrogenous
Our effort was initiated by the reaction between p-toluidine
(
(
2a, 1.1 equiv.) and 8-methyl-2-phenylimidazo[1,2-a]pyridine
t
1a) in presence of BuONO (1.2 equiv.) at room temperature
in DMSO affording the diazo compound 3aa in 68% (Table 1,
entry 1). Next we checked the effect of various solvents like
DMF, CH3CN, THF, 1,4-dioxane, DCM, MeOH and EtOH (Table
1, entries 2-8). Among them, EtOH was found to be the best
solvent to furnish the desired product with 88% yield after 8 h
(Table 1, entry 8) probably due to fact that EtOH is a polar
protic solvent which helps to stabilize the diazonium ion.
Prolonged reaction time did not improve the yield. Next we
Department of Chemistry, Visva-Bharati (A Central University)
Santiniketan, 731235, West Bengal, India.
E-mail: alakananda.hajra@visva-bharati.ac.in
http://www.visvabharati.ac.in/AlakanandaHajra.html
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
t
increased the amount of p-toluidine (2a) and BuONO, but no
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Scheme 2 Substrates scopea
significant increase in yield was seen to occur (Table 1, entry
9). Only a trace amount of product was obtained when the
reaction was performed at 0 oC for 24 h (Table 1, entry 10).
Table 1 Optimization of the reaction conditionsa
Entry
1
Solvent
DMSO
2a
(equiv.)
1.1
tBuONO Temp Time Yield
(equiv.)
1.2
(oC)
(h)
24
(%)
68
rt
2
3
4
5
6
DMF
CH3CN
THF
1.1
1.1
1.1
1.1
1.1
1.2
1.2
1.2
1.2
1.2
rt
rt
rt
rt
rt
24
24
24
24
24
54
43
63
56
nrb
1,4-dioxane
DCM
7
MeOH
1.1
1.2
rt
24
76
8
EtOH
1.1
1.2
rt
8
88
9
EtOH
EtOH
1.5
1.1
2
rt
0
24
24
88
10
1.2
trace
a
Reaction conditions: All reactions were carried out on 0.20 mmol scale in
solvent (1.5 mL). b no reaction.
With the optimized reaction conditions in hand, the
substrate scope of the present protocol was explored and the
results are summarized in Scheme 2. A variety of anilines
having both electron donating substitutents like -Me, -OMe
and electron withdrawing groups like -CN, -NO2, -CO2Et, -
COMe, -COPh were studied under the present reaction
conditions. It is notable that electron-defficient anilines gave
better yields (3ad-ah) compared to electron-rich anilines (3aa
and 3ab) as diazonium salts bearing electron withdrawing
groups are stronger electrophiles than electron-rich diazonium
salts. The anilines having different halogens like -Cl, -F and -I
successfully reacted with imidazopyridine to give the
corresponding products in significant yields
Importantly, the reaction between 8-methyl-2-
1a
(3ai-ak).
phenylimidazo[1,2-a]pyridine
(
)
and
afforded
2-
aminobenzenesulfonamide
(
2m
)
ethyl
benzenesulfonate substituted azo derivative 3am
.
Next, we checked the scope of imidazopyridines having
different substituents like -Cl, -Br and -CN on the pyridine ring
as shown in Scheme 2. All of them gave the
a
Reaction conditios: 1 (0.20 mmol), 2 (0.22 mmol) and tBuONO (0.24 mmol) in EtOH
azoimidazopyridines (3cf, 3da and 3ef) with good to excellent
(1.5 mL) at rt for 8 h. b Reactions completed in 2 h. c tBuONO (0.4 mmol).
yields. Imidazopyridines having different aryl (3fa and 3ga) and
heteroaryl (3ha) substitutions at C-2 position furnished the
products with good yields. To our delight, heteroaryl amines
such as aminopyrazoles and aminopyridines also worked well
The
stereochemistry
of
8-methyl-2-phenyl-3-(p-
3aa was further
tolyldiazenyl)imidazo[1,2-a]pyridine
confirmed by X-ray single crystallographic analysis (Fig. 2).12
(
)
under the present reaction conditions
(
3an and 3ao).
1i), 2-
However, 2,3-unsubstituted imidazo[2,1-a]pyridine
(
isobutyl and CF3-substituted imidazo[2,1-a]pyridine (1j and 1k)
did not afford the desired products.
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The present protocol is also applicable for the intramolecular
azo coupling. Benzo[e]pyrrolo[2,1-c]-1,2,4-benzotriazine13
was obtained with 78% yield (Scheme 5). It is worthy to
mention that benzotriazine is an analogue of indole[1,2-c]-
9
9
1,2,4-benzotriazine derivatives which exhibit potent antifungal
activities against five phytopathogenic fungi.14
Fig 2 X-ray crystal structure of 3aa (Thermal ellipsoids are drawn at 30% probablity
level)
Scheme 5. Synthesis of benzo[e]pyrrolo[2,1-c][1,2,4]triazine
Next
imidazoheterocycles like benzo[d]imidazo[2,1-b]thiazole and
imidazo[2,1-b]thiazole (Scheme 3). Pleasingly, the
corresponding azo products were obtained with excellent
yields (5aa ca).
we
extended
our
protocol
to
other
Practical applicability of the present methodology was
examined by carrying out the gram-scale reaction in laboratory
setup (Scheme 6). The reaction afforded the azo imidazo[1,2-
a]pyridine (3aa) without significant decrease in yield (84%).
-
Scheme 3. Substrate scope of imidazoheterocyclesa
Scheme 6. Gram-scale Reactiona
A plausible mechanism is outlined in Scheme 7. First, aniline 2a
is converted to diazonium intermediate15
A in presence of
tBuONO which subsequently reacted with imidazopyridine 1a
at 3-postion. Finally the azo compound 3aa is formed via
a
t
Reaction conditios: 4 (0.20 mmol), 2 (0.22 mmol) and BuONO (0.24 mmol) in
EtOH (1.5 mL) at rt for 8 h. b Reaction completed in 1 h.
deprotonation of intermediate
2-positon of imidazopyridine ring is necessary to stabilise the
generated positive charge at 2-positon of the intermediate
B. The presence of aryl group at
Other than imidazoheterocycles, we were successful to install
the azo functionality in indolizine moiety regioselectively
(Scheme 4). Indolizines bearing –CO2Me and −CN successfully
reacted with differently substituted anilines to give the desired
products in very good yields (7af and 7bg).
B.
Therefore, 2-alkyl substituted imidazopyridine (1j) is inert
under the present reaction conditions.
Scheme 4. Synthesis of azo indolizinesa
Scheme 7. Plausible reaction pathway
a Reaction conditios: 0.20 mmol of 6 and 0.22 mmol of 2 in EtOH (1.5 mL) in the
presence of tBuONO (0.24 mmol) at rt for 4 h.
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The yellow precipitate was collected, washed with EtOH (5
mL) and 10% ethyl acetate/petroleum ether (3 mL). The solid
product was dried under vacuum to furnish pure
Conclusions
In summary, we have developed a convenient method for the
synthesis of azo imidazo[1,2-a]pyridines. A variety of (E)-3-
(aryldiazenyl)imidazo[1,2-a]pyridines with wide range of
functionalities were synthesized in good to excellent yields
under neutral conditions. Intriguingly, the protocol is also
applicable to other heterocycles like imidazo[2,1-b]thiazoles,
benzo[e]pyrrolo[2,1-c][1,2,4]triazine 9.
(E)-8-Methyl-2-phenyl-3-(p-tolyldiazenyl)imidazo[1,2-
a]pyridine (3aa): Orange solid (88%, 57 mg), mp 104-105 °C. IR
(KBr) νmax: 3443, 3022, 2465, 1599, 1524, 1477, 1445, 1350,
1252 cm-1; 1H NMR (400 MHz, CDCl3): δ 9.81 (d, J = 6.8 Hz, 1H),
8.46 (d, J = 8.4 Hz, 2H), 7.76 (d, J = 8.0 Hz, 2H), 7.54 (t, J = 7.6
Hz, 2H), 7.48-7.44 (m, 1H), 7.30-7.22 (m, 3H), 6.91 (t, J = 6.8
Hz, 1H), 2.72 (s, 3H), 2.43 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
152.0, 149.7, 146.0, 139.7, 133.5, 132.5, 130.1, 129.9, 129.1,
128.5, 128.4, 127.4, 127.2, 122.0, 115.1, 21.5, 17.0; HRMS (ESI-
TOF) m/z: [M + H]+ Calcd for C21H19N4: 327.1610; found:
327.1602.
benzo[d]imidazo[2,1-b]thiazoles
and
indolizines.
The
developed reaction procedure shows broad substrates scope,
uses safe reagents and solvent, clean reaction, and product
isolation by simple filtration making it a useful and preparative
method. We believe it will gain much imporatnce in academia
as well as industry for the synthesis of functionalized
azoheterocyles.
(E)-3-((4-Methoxyphenyl)diazenyl)-8-methyl-2-
phenylimidazo[1,2-a]pyridine (3ab): Orange solid (83%, 57
mg), mp 106-108 oC. IR (KBr) νmax: 3566, 3431, 3408, 3137,
Experimental Section
1
2825, 1603, 1582, 1497, 1439, 1375, 1308, 1250 cm-1; H NMR
General Information
(400 MHz, CDCl3): δ 9.80 (d, J = 6.4 Hz, 1H), 8.44 (d, J = 7.6 Hz,
2H), 7.80 (d, J = 8.8 Hz, 2H), 7.53 (t, J = 7.6 Hz, 2H), 7.45 (t, J =
7.2 Hz, 1H), 7.28 (t, J = 6.8 Hz, 1H), 7.00-6.95 (m, 3H), 3.88 (s,
3H), 2.78 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 161.2, 148.0,
144.7, 132.3, 132.1, 130.3, 129.4, 129.2, 128.5, 127.10, 127.06,
123.8, 115.6, 114.5; 55.7, 17.3; HRMS (ESI-TOF) m/z: [M + H]+
Calcd for C21H19N4O: 343.1559; found: 343.1555.
All reagents were purchased from commercial sources and
used without further purification, unless otherwise mentioned.
Petroleum ether (PE) refers to the fraction of petroleum
boiling between 60-80 oC. All reactions were carried out in
oven-dried glassware. All solvents were dried and distilled
before use. TLC was monitored on aluminium backed Silica Gel
60 (HF254) 0.25 mm plates (Merck) using various organic
solvent mixtures. Melting points were determined in open
capillary tubes and are uncorrected. IR spectra were recorded
(E)-8-Methyl-2-phenyl-3-(phenyldiazenyl)imidazo[1,2-
o
a]pyridine (3ac): Orange solid (87%, 54 mg), mp 98-100 C. IR
1
on a FTIR instrument. H and 13C NMR spectra were acquired
(KBr) νmax: 3059, 3028, 2395, 1618, 1591, 1579, 1525, 1483,
1
1471, 1444, 1379, 1350, 1290, 1250 cm-1; H NMR (400 MHz,
on spectrometers operating at 300 or 400 or 500 MHz and 75
or 100 or 125 MHz respectively, using CDCl3 (δ = 7.26 ppm for
the 1H NMR and δ =77.16 ppm for the 13C NMR or DMSO-d6 (δ
= 2.50 ppm for the 1H NMR and δ = 39.50 ppm for the 13C
NMR) solvent. High resolution mass spectra were obtained
using Qtof Micro YA263 instrument. X-ray single crystal data
were collected using MoKα (λ = 0.7107 Å) radiation on a
SMART APEX diffractometer equipped with CCD area detector.
Data collection, data reduction, structure solution/refinement
were carried out using the software package of SMART APEX.
Imidazoheterocycles were prepared by our reported methods,10c
and indolizine heterocycles were prepared by Hu. et al. report.16
Typical experimental procedure for the synthesis of (E)-8-methyl-
CDCl3): δ 9.86 (d, J = 6.8 Hz, 1H), 8.44 (d, J = 7.2 Hz, 2H), 7.87
(d, J = 7.6 Hz, 2H), 7.54-7.46 (m, 5H), 7.39 (t, J = 7.2 Hz, 1H),
7.29 (d, J = 6.8 Hz, 1H), 6.97 (t, J = 6.8 Hz, 1H), 2.74 (s, 3H); 13
C
NMR (100 MHz, CDCl3): δ 153.8, 150.2, 146.0, 133.1, 130.2,
129.6, 129.4, 129.32, 129.26, 129.0, 128.5, 127.4, 127.2, 122.1,
115.5, 17.0; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H17N4:
313.1453; found: 313.1447.
(E)-2-Phenyl-3-(p-tolyldiazenyl)imidazo[1,2-a]pyridine (3ba):
Orange solid (81%, 51 mg), mp 103-104 oC. IR (KBr) νmax: 3049,
3026, 1626, 1597, 1570, 1552, 1445, 1385, 1350, 1246 cm-1; 1H
NMR (400 MHz, CDCl3): δ 9.97 (d, J = 6.8 Hz, 1H), 8.45-8.43 (m,
2H), 7.78-7.74 (t, 3H), 7.55-7.51 (m, 2H), 7.48-7.44 (m, 2H),
7.30 (d, J = 8.0 Hz, 2H), 7.03 (t, J = 6.8 Hz, 1H), 2.43 (s, 3H); 13
C
2-phenyl-3-(p-tolyldiazenyl)imidazo[1,2-a]pyridine (3aa):
t
NMR (100 MHz, CDCl3): δ 152.0, 150.3, 146.0, 139.9, 133.4,
132.3, 130.1, 130.0, 129.4, 129.27, 129.25, 128.6, 122.1, 117.6,
115.2, 21.6; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H17N4:
313.1453; found: 313.1447.
A mixture of
p
-toluidine 2a (0.22 mmol, 21 mg) and BuONO
(0.24 mmol, 25 mg, 29
µ
L) in EtOH (1.5 mL) was taken in a
round bottom flask and was stirred for 3 min at room
temperature. To this solution 8-methyl-2-phenylimidazo[1,2-
(E)-2-((8-Methyl-2-phenylimidazo[1,2-a]pyridin-3-
yl)diazenyl)benzonitrile (3ad): Orange solid (91%, 61 mg), mp
a
]pyridine 1a (0.20 mmol, 42 mg) was added and allowed to
stir for 8 h (TLC). The orange precipitate was collected, washed
with EtOH (5 mL) and 10% ethyl acetate/petroleum ether (3
mL). The solid product was dried under vacuum to afford pure
o
141-142 C. IR (KBr) νmax: 3496, 3061, 2916, 2393, 2289, 2225,
1
1925, 1619, 1522, 1478, 1384, 1282, 1242, 1212 cm-1; H NMR
(400 MHz, CDCl3): δ 10.02 (s, 1H), 8.42 (d, J = 6.0 Hz, 2H), 7.88
(d, J = 4.4 Hz, 1H), 7.77 (d, J = 4.8 Hz, 1H), 7.64 (d, J = 7.2 Hz,
1H), 7.54-7.47 (m, 3H), 7.43-7.38 (m, 2H), 7.16 (d, J = 6.4 Hz,
1H), 2.76 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 156.0, 152.9,
147.1, 133.6, 133.2, 132.6, 131.1, 130.4, 130.0, 128.73, 128.66,
(
a
E
)-8-methyl-2-phenyl-3-(
]pyridine 3aa in 88% yield.
Synthesis of benzo[ ]pyrrolo[2,1-
solution of 2-(1 -pyrrol-1-yl)aniline
p-tolyldiazenyl)imidazo[1,2-
e
c
8
][1,2,4]triazine (9): To a
(0.20 mmol) in EtOH (1
mL) was added BuONO (0.24 mmol, 25 mg, 29 L) and the
H
t
µ
reaction mixture was stirred at room temperature for 8 h (TLC).
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128.4, 127.6, 118.3, 117.0, 115.6, 112.0, 17.0; HRMS (ESI-TOF) (m, 2H), 7.48-7.44 (m, 3H), 7.31 (d, J = 6.8, 1H), 6.98 (t, J = 6.8
m/z: [M + H]+ Calcd for C21H16N5: 338.1406; found: 338.1399.
Hz, 1H), 2.73 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 152.5,
(E)-8-Methyl-3-((3-nitrophenyl)diazenyl)-2
151.1, 146.5, 134.8, 133.4, 130.2, 129.5, 129.4, 129.1, 128.6,
phenylimidazo[1,2-a]pyridine (3ae): Orange solid (92%, 66 127.7, 127.3, 123.2, 115.5, 16.9; HRMS (ESI-TOF) m/z: [M + H]+
mg), mp 152-153 oC. IR (KBr) νmax: 3281, 3099, 1618, 1526, Calcd for C20H16ClN4: 347.1063; found: 347.1066.
1508, 1474, 1456, 1416, 1350, 1319, 1286, 1246 cm-1; H NMR (E)-3-((4-Fluorophenyl)diazenyl)-8-methyl-2-
1
(400 MHz, CDCl3): δ 9.80 (d, J = 6.8 Hz, 1H), 8.60 (t, J = 6.8 Hz, phenylimidazo[1,2-a]pyridine (3aj): Orange solid (90%, 59
1H), 8.40 (d, J = 8.0 Hz, 2H), 8.17-8.16 (m, 1H), 8.09 (d, J = 7.2 mg), mp 102-103 oC. IR (KBr) νmax: 3130, 3053, 3032, 2229,
Hz, 1H), 7.62-7.46 (m, 4H), 7.35 (d, J = 7.2 Hz, 1H), 7.02 (t, J = 2129, 1587, 1477, 1445, 1425, 1379, 1348, 1294, 1247 cm-1; 1H
7.2 Hz, 1H), 2.72 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 154.7, NMR (400 MHz, CDCl3): δ 9.75 (d, J = 6.8 Hz, 1H), 8.42-8.39 (m,
152.8, 149.3, 147.1, 133.1, 132.5, 130.2, 129.98, 129.95, 129.8, 2H), 7.83-7.79 (m, 2H), 7.55-7.51 (m, 2H), 7.48-7.43 (m, 1H),
128.7, 127.9, 127.6, 126.8, 122.8, 117.4, 116.0, 16.9; HRMS 7.26-7.24 (m, 1H), 7.18-7.13 (m, 2H), 6.92 (t, J = 7.2 Hz, 1H),
1
(ESI-TOF) m/z: [M + H]+ Calcd for C20H16N5O2: 358.1304; found: 2.71 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 163.2 (d, JCF = 249
4
Hz), 150.5, 150.4 (d, JCF = 2 Hz), 146.3, 133.5, 132.4, 130.1,
358.1298.
2
129.2, 128.6, 128.5, 127.5, 127.1, 123.7 (d, JCF = 9 Hz), 116.1
(E)-Ethyl4-((8-methyl-2-phenylimidazo[1,2-a]pyridin-3-
2
yl)diazenyl)benzoate (3af): Red solid (97%, 75 mg), mp 126- (d, JCF = 23 Hz), 115.2, 16.9; HRMS (ESI-TOF) m/z: [M + H]+
128 oC. IR (KBr) νmax: 3369, 2980, 2902, 2841, 2446, 1711, Calcd for C20H16FN4: 331.1359; found: 331.1368.
1599, 1477, 1273, 1248 cm-1; 1H NMR (400 MHz, CDCl3): δ 9.85 (E)-3-((2-Iodophenyl)diazenyl)-8-methyl-2-phenylimidazo[1,2-
(d, J = 6.8 Hz, 1H), 8.44-8.42 (m, 2H), 8.15 (d, J = 8.4 Hz, 2H), a]pyridine (3ak): Orange solid (83%, 73 mg), mp 111-112 oC. IR
7.85 (d, J = 8.4 Hz, 2H), 7.55-7.45 (m, 3H), 7.32 (d, J = 7.2 Hz, (KBr) ν: 3117, 2916, 1522, 1481, 1373, 1238 cm-1; 1H NMR (400
1H), 6.99 (t, J = 7.2 Hz, 1H), 4.41 (q, J = 6.8 Hz, 2H), 2.72 (s, 3H), MHz, CDCl3): δ 10.13 (d, J = 6.4 Hz, 1H), 8.44 (d, J = 8.0 Hz, 2H),
1.43 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): δ 166.4, 8.00 (d, J = 8.0 Hz, 1H), 7.76 (d, J = 8.0 Hz, 1H), 7.55-7.52 (m,
156.8, 152.1, 146.9, 133.3, 132.9, 130.8, 130.2, 129.6, 128.6, 2H), 7.49-7.41 (m, 2H), 7.36 (d, J = 7.2 Hz, 1H), 7.06 (t, J = 7.6
127.7, 127.5, 121.8, 115.8, 61.2, 16.9, 14.5; HRMS (ESI-TOF) Hz, 2H), 2.74 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 153.1,
m/z: [M
385.1660.
+
H]+ Calcd for C23H21N4O2: 385.1665; found: 152.1, 146.9, 139.8, 133.4, 133.0, 130.4, 130.3, 129.7, 129.5,
129.1, 128.7, 128.6, 127.5, 117.2, 116.0, 101.5, 16.9; HRMS
(E)-1-(4-((8-Methyl)-2-phenylimidazo[1,2-a]pyridin-3-
(ESI-TOF) m/z: [M + H]+ Calcd for C20H16IN4: 439.0420; found:
yl)diazenyl)phenyl)ethanone (3ag): Orange solid (96%, 68 mg), 439.0436.
mp 114-116 oC. IR (KBr) νmax: 3854, 3838, 3821, 3749, 3736, (E)-Ethyl2-((8-methyl-2-phenylimidazo[1,2-a]pyridin-3-
3674, 3651, 3616, 3061, 2991, 2918, 1680, 1651, 1595, 1560, yl)diazenyl)benzenesulfonate (3al): Compound 3al was
1541, 1524, 1512, 1491, 1477, 1460, 1443, 1377, 1350, 1292, obtained
as
described
for
3aa
by
using
2-
1263, 1248 cm-1; H NMR (400 MHz, CDCl3): δ 9.85 (d, J = 6.8 aminobenzenesulfonamide 2l (0.22 mmol, 38 mg), tBuONO
Hz, 1H), 8.43 (d, J = 7.2 Hz, 2H), 8.06 (d, J = 8.4 Hz, 2H), 7.87 (d, (0.4 mmol, 42 mg, 48 μL), 8-methyl-2-phenylimidazo[1,2-
J = 8.4 Hz, 2H), 7.55-7.46 (m, 3H), 7.33 (d, J = 6.8 Hz, 1H), 7.00 a]pyridine 1a (0.20 mmol, 42 mg). Orange solid (80%, 67 mg),
(t, J = 6.8 Hz, 1H), 2.72 (s, 3H), 2.64 (s, 3H); 13C NMR (100 MHz, mp 182-183 oC. IR (KBr) νmax: 3089, 1586, 1510, 1382, 1346,
1
CDCl3): δ 197.4, 156.6, 152.0, 146.7, 136.4, 133.1, 132.8, 130.1, 1243 cm-1; H NMR (400 MHz, CDCl3): δ 10.27 (d, J = 6.4 Hz,
1
130.0, 129.6, 129.5, 128.5, 127.5, 127.4, 121.8, 115.7, 26.8, 1H), 8.44 (d, J = 7.2 Hz, 2H), 8.13 (d, J = 7.6 Hz, 1H), 7.94 (d, J =
16.8; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C22H19N4O: 8.0 Hz, 1H), 7.72 (t, J = 7.2 Hz, 1H), 7.56-7.41 (m, 5H), 7.13 (t, J
355.1559; found: 355.1552.
= 7.2 Hz, 1H), 4.18 (q, J = 6.8 Hz, 2H), 2.75 (s, 3H), 1.25 (t, J =
7.2 Hz, 3H); 13C NMR (100 MHz, DMSO-d6): δ 143.8, 132.9,
(E)-(2-((8-Methyl-2-phenylimidazo[1,2-a]pyridin-3-
yl)diazenyl)phenyl)(phenyl)methanone (3ah): Orange solid 131.7, 131.1, 130.6, 130.1, 129.9, 129.8, 129.4, 128.8, 128.4,
o
(94%, 78 mg), mp 111-112 C. IR (KBr) νmax: 3309, 3134, 3061, 127.7, 127.0, 125.1, 123.3, 117.1, 114.2, 56.1, 18.6, 16.3;
2918, 2367, 2338, 1901, 1663, 1589, 1522, 1478, 1441, 1383, HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C22H21N4O3S: 421.1334;
1314 cm-1; 1H NMR (400 MHz, CDCl3): δ 8.61 (d, J = 6.8 Hz, 1H), found: 421.1327.
8.38-8.36 (m, 2H), 7.92-7.89 (m, 3H), 7.66-7.59 (m, 2H), 7.55- (E)-Ethyl4-((6-chloro-2-phenylimidazo[1,2-a]pyridine-3-
7.47 (m, 5H), 7.43-7.39 (m, 2H), 7.21 (d, J = 6.8 Hz, 1H), 6.57 (t, yl)diazenyl)benzoate (3cf): Orange solid (95%, 78 mg), mp
o
J = 7.2 Hz, 1H), 2.69 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 140-141 C. IR (KBr) νmax: 3043, 2980, 2368, 1934, 1721, 1599,
198.2, 151.8, 146.0, 138.4, 137.8, 133.4, 132.7, 132.6, 131.2, 1522, 1479, 1385, 1317 cm-1; 1H NMR (400 MHz, CDCl3): δ
130.3, 130.1, 129.8, 129.7, 129.4, 128.9, 128.7, 128.6, 127.2, 10.07 (s, 1H), 8.40 (d, J = 8.0 Hz, 2H), 8.19 (d, J = 8.4 Hz, 2H),
127.0, 116.3, 115.6, 17.0; HRMS (ESI-TOF) m/z: [M + H]+ Calcd 7.90 (d, J = 8.8 Hz, 2H), 7.74 (d, J = 9.6 Hz, 1H), 7.56-7.47 (m,
for C27H21N4O: 417.1715; found: 417.1712.
4H), 4.42 (q, J = 7.2 Hz, 2H), 1.44 (t, J = 7.2 Hz, 3H); 13C NMR
(100 MHz, CDCl3): δ 166.3, 156.4, 144.7, 132.4, 132.3, 131.4,
(E)-3-((4-Chlorophenyl)diazenyl)-8-methyl-2-
phenylimidazo[1,2-a]pyridine (3ai): Orange solid (88%, 61 131.1, 130.9, 130.2, 130.1, 128.8, 127.5, 123.8, 122.0, 117.9,
mg), mp 100-101 oC. IR (KBr) νmax: 3043, 2918, 2849, 2422, 61.3, 14.5; HRMS (ESI-TOF) m/z: [M
+
H]+ Calcd for
1618, 1583, 1572, 1522, 1472, 1445, 1383, 1375, 1350, 1308, C22H18ClN4O2: 405.1118; found: 405.1110.
1
1294, 1252 cm-1; H NMR (400 MHz, CDCl3): δ 9.82 (d, J = 6.8 (E)-6-Bromo-2-phenyl-3-(p-tolyldiazenyl)imidazo[1,2-
Hz, 1H), 8.41 (d, J = 8.0 Hz, 2H), 7.78 (d, J = 6.8, 2H), 7.55-7.51 a]pyridine (3da): Orange solid (76%, 59 mg), mp 136-137 oC. IR
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(KBr) νmax: 3130, 3038, 3001, 2917, 2857, 1933, 1894, 1599, MHz, CDCl3): δ 9.78 (d, J = 6.8 Hz, 1H), 9.08 (s, 1H), 8.56 (d, J =
1474, 1382, 1325, 1237 cm-1; 1H NMR (400 MHz, CDCl3): δ 3.6 Hz, 1H), 8.39 (d, J = 7.2 Hz, 2H), 8.02 (d, J = 8.0 Hz, 1H),
10.15 (s, 1H), 8.41 (d, J = 8.4 Hz, 2H), 7.79 (d, J = 8.4 Hz, 2H), 7.52-7.43 (m, 3H), 7.40-7.30 (m, 1H), 7.30 (d, J = 6.8 Hz, 1H),
7.64 (d, J = 9.2 Hz, 1H), 7.54-7.46 (m, 4H), 7.32 (d, J = 8.0 Hz, 6.97 (t, J = 6.8 Hz, 1H), 2.70 (s, 3H); 13C NMR (100 MHz, CDCl3):
2H), 2.44 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 151.7, 150.4, δ 151.8, 149.6, 149.4, 146.7, 146.4, 133.2, 132.9, 130.1, 129.5,
144.3, 140.6, 133.0, 132.3, 132.1, 130.1, 130.0, 129.5, 129.3, 128.6, 127.7, 127.4, 126.1, 124.1, 115.7, 16.8; HRMS (ESI-TOF)
128.7, 122.3, 118.1, 109.5, 21.6; HRMS (ESI-TOF) m/z: [M + H]+ m/z: [M + H]+ Calcd for C19H16N5: 314.1406; found: 314.1401.
Calcd for C20H16BrN4: 391.0558; found: 391.0552.
(E)-8-Methyl-2-phenyl-3-((3-phenyl-1H-pyrazol-5-
(E)-Ethyl4-((6-cyano-2-phenylimidazo[1,2-a]pyridin-3-
yl)diazenyl)imidazo[1,2-a]pyridine (3an): Brown solid (74%, 56
yl)diazenyl)benzoate (3ef): Orange solid (88%, 70 mg), mp mg), mp 135-137 oC. IR (KBr) νmax: 3142, 3067, 3013, 2880,
o
1
184-186 C. IR (KBr) νmax: 3401, 3120, 3046, 2984, 2234, 1934, 1483, 1373, 1308, 1249 cm-1; H NMR (500 MHz, DMSO-d6): δ
1
1713, 1599, 1524, 1482, 1387, 1334, 1308 cm-1; H NMR (400 9.69 (d, J = 6.5 Hz, 1H), 8.41 (d, J = 7.5 Hz, 2H), 7.87 (d, J = 7.5
MHz, CDCl3): δ 10.35 (s, 1H), 8.40 (d, J = 6.4 Hz, 2H), 8.20 (d, J = Hz, 2H), 7.58 (t, J = 7.5 Hz, 2H), 7.50-7.47 (m, 5H), 7.39 (t, J =
8.4 Hz, 2H), 7.91 (d, J = 8.4 Hz, 2H), 7.82 (d, J = 8.8 Hz, 1H), 7.5 Hz, 1H), 7.21 (t, J = 7.0 Hz, 1H), 6.91 (s, 1H), 2.61 (s, 3H); 13C
7.60-7.53 (m, 4H), 4.43 (d, J = 7.2 Hz, 2H), 1.44 (t, J = 7.2 Hz, NMR (125 MHz, DMSO-d6): δ 148.5, 145.7, 132.7, 132.1, 129.7,
3H); 13C NMR (100 MHz, CDCl3): δ 166.1, 156.0, 135.3, 132.0, 129.6, 129.4, 129.1, 128.9, 128.7, 128.5, 126.9, 125.4, 116.2,
131.7, 131.0, 130.9, 130.6, 130.3, 129.8, 128.9, 122.2, 121.8, 90.8, 16.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C23H19N6:
118.6, 116.4, 101.5, 61.4, 14.5; HRMS (ESI-TOF) m/z: [M + H]+ 379.1671; found: 379.1668.
Calcd for C23H18N5O2: 396.1460; found: 396.1452.
(E)-2-(p-Tolyl)-3-(p-tolyldiazenyl)benzo[d]imidazo[2,1-
o
b]thiazole (5aa): Yellow solid (92%, 70 mg), mp 128-129 C. IR
(E)-2-(Naphthalen-2-yl)-3-(p-tolyldiazenyl)imidazo[1,2-
a]pyridine (3fa): Orange solid (90%, 65 mg), mp 111-113 oC. IR (KBr) νmax: 3095, 3058, 3020, 2708, 2272, 1485, 1474, 1356,
(KBr) νmax: 3080, 3018, 1506, 1487, 1458, 1394, 1385, 1352, 1335, 1236 cm-1; H NMR (400 MHz, CDCl3): δ 9.14 (d, J = 8.0
1
1323, 1302, 1248, 1240 cm-1; 1H NMR (400 MHz, CDCl3): δ 9.97 Hz, 1H), 8.20 (d, J = 8.4 Hz, 2H), 7.81 (d, J = 8.4 Hz, 2H), 7.67 (d,
(s, 1H), 8.97 (s, 1H), 8.60 (d, J = 8.8 Hz, 1H), 8.00-7.96 (m, 2H), J = 7.6 Hz, 1H), 7.46 (t, J = 7.2 Hz, 1H), 7.38-7.30 (m, 5H), 2.45
7.90-7.88 (m, 1H), 7.82-7.76 (m, 3H), 7.54-7.45 (m, 3H), 7.31 (s, 3H), 2.44 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 153.4, 151.7,
(d, J = 7.6 Hz, 2H), 7.03 (s, 1H), 2.44 (s, 3H); 13C NMR (100 MHz, 150.9, 140.4, 139.1, 138.8, 134.4, 130.8, 130.1, 130.0, 129.7,
CDCl3): δ 152.0, 150.1, 146.1, 140.0, 133.8, 133.5, 132.5, 130.8, 129.3, 126.0, 125.4, 123.5, 122.3, 119.6, 21.63, 21.57; HRMS
130.1, 130.0, 129.5, 129.4, 129.1, 128.0, 127.8, 127.1, 126.9, (ESI-TOF) m/z: [M + H]+ Calcd for C23H19N4S: 383.1330; found:
126.3, 122.1, 117.5, 115.2, 21.6; HRMS (ESI-TOF) m/z: [M + H]+ 383.1327.
Calcd for C24H19N4: 363.1610; found: 363.1603.
(E)-3-((2-Bromo-5-(trifluoromethyl)phenyl)diazenyl)-2-
(E)-2-(3-(p-Tolyldiazenyl)imidazo[1,2-a]pyridin-2-
phenylbenzo[d]imidazo[2,1-b]thiazole (5bo): Yellow solid
o
o
yl)phenol(3ga): Orange solid (82%, 54 mg), mp 120-122 C. IR (93%, 93 mg), mp 161-162 C. IR (KBr) νmax: 3086, 3057, 3020,
(KBr) νmax: 3086, 3024, 2916, 2858, 2806, 2725, 2644, 2557, 2930, 1516, 1474, 1423, 1377, 1342, 1317, 1256, 1232 cm-1; 1H
1618, 1587, 1578, 1512, 1497, 1408, 1385, 1354, 1323, 1303, NMR (400 MHz, CDCl3): δ 9.51 (d, J = 8.8 Hz, 1H), 8.27 (d, J =
1
1245, 1234 cm-1; H NMR (400 MHz, CDCl3): δ 13.09 (brs, 1H), 7.6 Hz, 2H), 8.00 (s, 1H), 7.87 (d, J = 8.4 Hz, 1H), 7.72 (d, J = 8.0
10.00 (d, J = 6.4 Hz, 1H), 8.74 (d, J = 7.6 Hz, 1H), 7.88 (d, J = 6.4 Hz, 1H), 7.51-7.41 (m, 6H); 13C NMR (75 MHz, CDCl3): δ 156.1,
2
Hz, 1H), 7.75 (d, J = 8.0 Hz, 2H), 7.66 (d, J = 8.8 Hz, 1H), 7.50 (t, 155.5, 151.9, 137.6, 134.7, 133.9, 132.9, 130.0 (q, JCF = 33.0
3
J = 7.2 Hz, 1H), 7.38-7.28 (m, 3H), 7.10-6.99 (m, 2H), 2.45 (s, Hz), 130.3, 129.9, 129.8, 128.6, 126.9, 126.5, 126.1 (q, JCF
=
3H); 13C NMR (100 MHz, CDCl3): δ 159.6, 151.8, 143.6, 140.2, 3.8 Hz), 126.0, 123.8 (q, 1JCF = 270.8 Hz), 123.5, 120.4, 116.3 (q,
131.3, 131.2, 130.0, 129.9, 129.5, 122.8, 122.6, 122.1, 119.4, 3JCF = 4.5 Hz); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for
117.8, 116.5, 116.4, 115.8, 21.6; HRMS (ESI-TOF) m/z: [M + H]+ C22H13BrF3N4S: 500.9996; found: 501.0000.
Calcd for C20H17N4O: 329.1402; found: 329.1396.
(E)-6-Phenyl-5-(p-tolyldiazenyl)imidazo[2,1-b]thiazole (5ca):
o
Yellow solid (89%, 57 mg), mp 126-127 C. IR (KBr) νmax: 3138,
(E)-2-(Thiophen-2-yl)-3-(p-tolyldiazenyl)imidazo[1,2-
o
a]pyridine (3ha): Yellow solid (85%, 54 mg), mp 120-121 C. IR 3109, 3096, 3061, 3030, 2804, 2249, 1601, 1522, 1475, 1456,
(KBr) νmax: 3059, 3029, 2917, 2856, 2395, 1952, 1901, 1787, 1437, 1369, 1348, 1325, 1294, 1250 cm-1; H NMR (400 MHz,
1
1
1716, 1554, 1484, 1431, 1384, 1331 cm-1; H NMR (400 MHz, CDCl3): δ 8.50 (s, 1H), 8.37 (d, J = 7.6 Hz, 2H), 7.74 (d, J = 7.6
CDCl3): δ 9.86 (d, J = 6.8 Hz, 1H), 8.13-8.12 (m, 1H), 7.83 (d, J = Hz, 2H), 7.50 (t, J = 7.2 Hz, 2H), 7.41 (t, J = 7.2 Hz, 1H), 7.28 (d, J
8.0 Hz, 2H), 7.69 (d, J = 9.2 Hz, 1H), 7.55-7.53 (m, 1H), 7.46- = 8.0 Hz, 2H), 6.88 (d, J = 3.6 Hz, 1H), 2.43 (s, 3H); 13C NMR
7.42 (m, 1H), 7.31 (d, J = 8.4 Hz, 2H), 7.22-7.20 (m, 1H), 7.00 (t, (100 MHz, CDCl3): δ 154.2, 151.5, 149.6, 140.3, 136.1, 133.4,
J = 7.0 Hz, 1H), 2.43 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 129.9, 129.0, 128.9, 128.6, 123.2, 122.3, 113.1, 21.6; HRMS
152.0, 146.4, 146.1, 140.0, 135.7, 130.9, 130.0, 129.8, 129.6, (ESI-TOF) m/z: [M + H]+ Calcd for C18H15N4S: 319.1017; found:
129.2, 128.1, 122.3, 117.3, 115.0, 21.6; HRMS (ESI-TOF) m/z: 319.1015.
[M + H]+ Calcd for C18H15N4S: 319.1017; found: 319.1015.
(E)-Methyl3-((4-(1-ethoxycarbonyl)phenyl)diazenyl)
(E)-8-Methyl-2-phenyl-3-(pyridin-3-yldiazenyl)imidazo[1,2-
indolizine-1-carboxylate (7af): Red solid (94%, 66 mg), mp 97-
o
a]pyridine (3am): Orange solid (79%, 49 mg), mp 145-146 C. 98 oC. IR (KBr) νmax: 3404, 3370, 3125, 3096, 3083, 2979, 2956,
IR (KBr) νmax: 3030, 2918, 2849, 1672, 1580, 1526, 1473, 1447, 2900, 2866, 2835, 2639, 2327, 2260, 1956, 1911, 1707, 1700,
1
1423, 1381, 1350, 1306, 1292, 1261, 1248 cm-1; H NMR (400 1599, 1521, 1418, 1388, 1343 cm-1; 1H NMR (400 MHz, CDCl3):
6 | J. Name., 2012, 00, 1-3
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Journal Name
ARTICLE
A.-A. El-Ahl, F. A. Badria, Chem. Pharm. Bull. 2009, 57, 1348;
(e) A. Sharma, B. K. Sarangi and R. K. Behera, J. Indian Chem.
Soc. 1985, 62, 253; (f) A. S. Shawali, M. Sami and S. M. Sherif,
J. Heterocyclic Chem., 1980, 17, 877; (g) H. M. Hassaneen, A.
S. Shawali, N. M. Elwan and N. M. Abounada, Org. Prep.
Proced. Int., 1992, 24, 171; (h) H. Faustino, R. M. El-
Shishtawy, L. V. Reis, P. F. Santos and P. Almeida,
Tetrahedron Lett., 2008, 49, 6907.
(a) C. Enguehard-Gueiffier and A. Gueiffier, Mini Rev. Med.
Chem., 2007, 7, 888; (b) A. T. Baviskar, S. M. Amrutkar, N.
Trivedi, V. Chaudhary, A. Nayak, S. K. Guchhait, U. C.
Banerjee, P. V. Bharatam and C. N. Kundu, ACS Med. Chem.
δ 9.32 (brs, 1H), 8.27 (d, J = 8.8 Hz, 1H), 8.08 (d, J = 8.4 Hz, 2H),
7.79 (d, J = 7.6 Hz, 3H), 7.34 (t, J = 7.6 Hz, 1H), 6.99 (t, J = 6.8
Hz, 1H); 4.38 (q, J = 7.2 Hz, 2H), 3.89 (s, 3H), 1.41 (t, J = 6.8 Hz,
3H); 13C NMR (100 MHz, CDCl3): δ 166.3, 164.7, 156.1, 138.2,
130.6, 130.5, 127.6, 121.7, 119.9, 115.5, 108.3, 61.2, 51.5,
14.4; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C19H18N3O4:
352.1297; found: 352.1291.
7
(E)-3-((4-Acetylphenyl)diazenyl)indolizine-1-carbonitrile
(
7bg): Red solid (92%, 53 mg), mp 143-145 oC. IR (KBr) νmax
:
3135, 3107, 2369, 2217, 1934, 1677, 1490, 1422, 1350 cm-1; 1H
NMR (400 MHz, CDCl3): δ 9.42 (brs, 1H), 8.06 (d, J = 8.0 Hz, 2H),
7.89 (d, J = 8.0 Hz, 2H), 7.78 (d, J = 8.0 Hz, 1H), 7.65 (s, 1H),
7.44 (t, J = 6.8 Hz, 1H), 7.13 (t, J = 7.6 Hz, 1H), 2.65 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 197.4, 156.0, 139.6, 137.6, 129.6,
127.6, 126.3, 126.21, 126.15, 122.3, 118.1, 116.1, 115.3, 87.2,
26.9; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C17H13N4O:
289.1089; found: 289.1086.
Lett., 2015, 6, 481.
(a) A. J. Stasyuk, M. Banasiewicz, M. K. Cyrański and D. T.
Gryko, J. Org. Chem., 2012, 77, 5552; (b) N. Shao, G.-X. Pang,
8
9
C.-X. Yan, G.-F. Shi and Y. Cheng, J. Org. Chem., 2011, 76
7458.
,
(a) K. Pericherla, P. Kaswan, K. Pandey and A. Kumar,
Synthesis, 2015, 47, 887; (b) A. K. Bagdi, S. Santra, K. Monir
and A. Hajra, Chem. Commun., 2015, 51, 1555; (c) H. Cao, X.
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Benzo[e]pyrrolo[2,1-c][1,2,4]triazine (9): Yellow solid (78%, 26
mg), mp 176-178 oC. IR (KBr) νmax: 3119, 3109, 3055, 3020,
1792, 1706, 1610, 1578, 1524, 1506, 1491, 1456, 1406, 1356,
1308, 1277, 1236 cm-1; 1H NMR (400 MHz, CDCl3): δ 8.42 (d, J =
8.4 Hz, 1H), 7.85-7.83 (m, 2H), 7.72 (t, J = 7.6 Hz, 1H), 7.57 (t, J
Liu, H. Cai, S. Qiu and J. Tan, Chem. Commun., 2015, 51
1823.
,
10 (a) S. Mishra, K. Monir, S. Mitra and A. Hajra, Org. Lett.,
2014, 16, 6084; (b) K. Monir, A. K. Bagdi, M. Ghosh and A.
Hajra, Org. Lett., 2014, 16, 4630; (c) A. K. Bagdi, M. Rahman,
S. Santra, A. Majee and A. Hajra, Adv. Synth. Catal., 2013,
355, 1741; (d) S. Santra, A. K. Bagdi, A. Majee and A. Hajra,
Adv. Synth. Catal., 2013, 355, 1065.
11 (a) K. Monir, A. K. Bagdi, M. Ghosh and A. Hajra, J. Org.
Chem., 2015, 80, 1332; (b) S. Mitra, M. Ghosh, S. Mishra and
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= 8.0 Hz, 1H), 7.42 (d, J = 4.0 Hz, 1H), 7.10 (t, J = 4.0 Hz, 1H); 13
C
NMR (100 MHz, CDCl3): δ 141.3, 136.5, 132.3, 130.8, 125.9,
124.9, 116.4, 113.5, 111.0, 109.0; HRMS (ESI-TOF) m/z: [M +
H]+ Calcd for C10H8N3: 170.0718; found: 170.0715.
Acknowledgements
12 Further information can be found in the CIF file. This crystal
was deposited in the Cambridge Crystallographic Data
Centre and assigned as CCDC 1420103.
13 Von Dr. H. GroB and Dipl.-Chem. J. Gloede, Angew. chem.,
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DOI: 10.1039/C6RA03070J
tert-Butyl nitrite mediated azo coupling between anilines and
imidazoheterocycles
Amrita Chakraborty, Sourav Jana, Golam Kibriya, Amrita Dey, and Alakananda
Hajra*
Department of Chemistry, Visva-Bharati (A Central University),
Santiniketan, 731235, West Bengal, India.
E-mail: alakananda.hajra@visva-bharati.ac.in
A tBuONO mediated practical and efficient method for the synthesis of azo imidazoheterocycles
with broad functionalities has been achieved by the reaction between imidazoheterocycles and
anilines at room temperature in goods yields. Azo indolizines were also prepared employing this
methodology. Mild reaction conditions, tolerance of wide functionalities, operational simplicity
and easy purification of products are the notable advantages of the current protocol.