Copper(II)-catalyzed aerobic oxidative coupling between chalcone and 2-aminopyridine via C-H amination: An expedient synthesis of 3-aroylimidazo[1,2-a]pyridines

Article abstract of DOI:10.1002/adsc.201300900

A simple and efficient protocol has been developed for the synthesis of 3-aroylimidazopyridines via copper(II) acetate-catalyzed aerobic oxidative amination. A library of 3-aroylimidazopyridines was synthesized from readily accessible chalcones and 2-aminopyridines with high yields and regioselectivity. The reaction proceeds through a tandem Michael addition followed by an intramolecular oxidative amination. The successful application of this methodology for a gram-scale reaction indicates its potential for bulk synthesis.

Full text of DOI:10.1002/adsc.201300900

Supporting Information
© Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2013

Supporting Information
Copper(II)-Catalyzed Aerobic Oxidative Coupling between
Chalcone and 2-Aminopyridine via C-H Amination: An
Expedient Synthesis of 3-Aroylimidazo[1,2-a]pyridines
Kamarul Monir,a Avik Kumar Bagdi,a Subhajit Mishra,a Adinath Majee,a and
Alakananda Hajra*a
a Department of Chemistry, Visva-Bharati (A Central University),
Santiniketan-731235, India
Table of contents:
1.
Experimental Section
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A. General
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B. General Experimental Procedure
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C. Spectroscopic Data
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2.
3.
References
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1H and 13C NMR spectra of Compounds
S1

1. Experimental Section
A. General:
1H NMR spectra were determined on a Bruker 400 (400 MHz) and Bruker 300 (300 MHz)
spectrometer as solutions in CDCl3. Chemical shifts are expressed in parts per million (δ) and
the signals were reported as s (singlet), d (doublet), t (triplet), m (multiplet) and coupling
constants J were given in Hz. 13C NMR spectra were recorded at 100 MHz and 75 MHz in
CDCl3 solution. Chemical shifts are expressed in parts per million (δ) and are referenced to
CDCl3 (δ = 77.16) as internal standard. TLC was done on silica gel coated glass slide (Merck,
Silica gel G for TLC). All solvents were dried and distilled before use. Commercially available
substrates were freshly distilled before the reaction. Solvents, reagents and chemicals were
purchased from Aldrich, Fluka, Merck, SRL, Spectrochem and Process Chemicals. All reactions
involving moisture sensitive reactants were executed using oven dried glassware. The synthesis
of chalcone was carried out according to the reported method.1
B. General procedure for synthesis of imidazo[1,2-a]pyridine derivatives:
N
N
O
Ph
Ph
Phenyl-(2-phenyl-imidazo[1,2-a]pyridin-3-yl)-methanone (3a):
A mixture of 2-aminopyridine (1a, 1.2 mmol), chalcone(2a, 1 mmol), Cu(OAc)2.H2O (0.1
mmol), and 1,10-Phenanthroline (0.1 mmol) in 1,2-dichlorobenzene (2 mL) was stirred in a
reaction tube at 120 OC for 12 hours using O2 baloon. The reaction was monitored by TLC. After
completion of the reaction, it was cooled to room temperature. Then it was filtered and washed
with dichloromethane. The filtrate was concentrated and the crude product was purified by
column chromatography on silica gel using petroleum ether/ethyl acetate (2:1) as eluent. Yield:
S2

84%; 1H NMR (CDCl3, 400 MHz) δ : 9.54 (d, J = 6.8 Hz, 1H), 7.80 (d, J = 9.2 Hz, 1H), 7.51 (d,
J = 8.8 Hz, 2H), 7.3 (d, J = 9.6 Hz, 2H), 7.28-7.26 (m, 1H), 7.18-7.01 (m, 7H) ; 13C NMR
(CDCl3, 100 MHz) δ :187.2, 154.8, 147.2, 138.4, 133.8, 131.6, 130.0, 129.4, 129.1, 128.1, 127.6,
127.4 (2C), 119.8, 117.3, 114.5. Anal. Calcd. For (%) C20H14N2O: C, 80.52; H, 4.73; N, 9.39.
Found C, 80.51; H, 4.63; N, 9.41.
Typical procedure for synthesis of Michael adduct 1,3-diphenyl-3-(pyridin-2-ylamino)-
propan-1-one (A):
H
N
N
O
1,3-Diphenyl-3-(pyridin-2-ylamino)-propan-1-one (A):
A mixture of 2-aminopyridine (1a, 1.2mmol), chalcone (2a, 1mmol) in 1,2 dichlorobenzene
(2mL) was stirred in a reaction tube under ambient air at 120 OC for 18 hours. The reaction was
monitored by TLC. After completion of the reaction, it was cooled to room temperature. Then it
was filtered and washed with dichloromethane. The filtrate was concentrated and the crude
product was purified by column chromatography on silica gel using petroleum ether/ethyl
1
acetate (2:1) as eluent. Yield: 48%. H NMR (CDCl3, 400 MHz) δ : 7.96 (d, J = 6.0 Hz, 1H),
7.84-7.81 (m, 2H), 7.48-7.41 (m, 1H), 7.39-7.32 (m, 4H), 7.29-7.20 (m, 3H), 7.19-7.17 (m, 1H),
6.47-6.44 (m, 1H), 6.27 (d, J = 8.4 Hz, 1H), 5.34-5.33 (m, 2H), 3.59-3.53 (m, 1H), 3.41-3.36
(m, 1H) ; 13C NMR (CDCl3, 100 MHz) δ :197.9, 157.7, 148.0, 142.4, 137.4, 136.7, 133.2, 128.6,
128.5, 128.1, 127.2, 126.4, 113.3, 107.4, 52.5, 45.6. Anal. Calcd. For (%) C20H18N2O: C, 79.44;
H, 6.00; N, 9.26. Found C, 79.53; H, 6.12; N, 9.13.
Typical procedure for synthesis of phenyl-(2-phenyl-imidazo[1,2-a]pyridin-3-yl)-
methanone (3a) from 1,3-diphenyl-3-(pyridin-2-ylamino)-propan-1-one (A):
S3

A mixture of 1,3-diphenyl-3-(pyridin-2-ylamino)-propan-1-one (A, 0.25mmol), Cu(OAc)2.H2O
(0.025 mmol) and 1,10-Phenanthroline (0.025 mmol) in 1,2-dichlorobenzene (1 mL) was stirred
O
in a reaction tube with O2 baloon at 120 C for 12 hours. The reaction was monitored by TLC.
After completion of the reaction, it was cooled to room temperature. Then it was filtered and
washed with dichloromethane. The filtrate was concentrated and the crude product was purified
by short column chromatography on silica gel to afford the compound 3a.
C. Spectroscopic Data:
Phenyl-(2-phenyl-imidazo[1,2-a]pyridin-3-yl)-methanone (Table 2, 3a):
1
Yield: 250 mg, 84%; Gummy mass; H NMR (CDCl3, 400 MHz) δ : 9.54
(d, J = 6.8 Hz, 1H), 7.80 (d, J = 9.2 Hz, 1H), 7.51 (d, J = 8.8 Hz, 2H), 7.3
(d, J = 9.6 Hz, 2H), 7.28-7.26 (m, 1H), 7.18-7.01 (m, 7H) ; 13C NMR
N
N
(CDCl3, 100 MHz) δ :187.2, 154.8, 147.2, 138.4, 133.8, 131.6, 130.0,
O
Ph
129.4, 129.1, 128.1, 127.6, 127.4 (2C), 119.8, 117.3, 114.5 ; Anal. Calcd.
Ph
For (%) C20H14N2O: C, 80.52; H, 4.73; N, 9.39. Found C, 80.51; H, 4.63;
N, 9.41.
(7-Methyl-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3b):
Yield: 249 mg, 80%; Gummy mass; 1H NMR (CDCl3, 400 MHz) δ : 9.35
Me
(d, J = 7.2, 1H), 7.53 (s, 1H), 7.40 (d, J = 8.8 Hz, 2H), 7.22-7.14 (m, 3H),
7.05-6.96 (m, 5H), 6.86 (d, J = 6.8 Hz, 1H), 2.43 (s, 3H) ; 13C NMR
N
(CDCl3, 100 MHz) δ : 187.0, 154.9, 141.0, 138.6, 133.7, 131.5, 130.1,
129.4, 128.1, 127.6 (2C), 127.4, 119.6, 117.2, 115.9, 21.5; Anal. Calcd.
For (%) C21H16N2O: C, 80.75; H, 5.16; N, 8.97. Found C, 80.65; H, 5.14;
N, 8.99.
N
O
Ph
Ph
S4

(8-Methyl-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3c):
1
Yield: 243 mg, 78%; Gummy mass; H NMR (CDCl3, 400 MHz) δ :
Me
9.29 (d, J = 6.8 Hz, 1H), 7.38 (d, J = 8.4 Hz, 2H), 7.22 (d, J = 7.6 Hz,
2H), 7.18-7.09 (m, 2H), 7.00-6.92 (m, 5H), 6.86 (t, J = 6.8 Hz, 1H),
2.61 (s, 3H); 13C NMR (CDCl3, 100 MHz) δ : 187.2, 154.3, 147.4,
N
N
O
138.6, 134.1, 131.4, 130.1, 129.3, 127.9, 127.5, 127.5, 127.2, 125.7,
Ph
Ph
120.9, 114.4, 16.9; Anal. Calcd. For (%) C21H16N2O: C, 80.75; H, 5.16;
N, 8.97. Found C, 80.68; H, 5.26; N, 8.80.
(6-Chloro-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3d):
1
Yield: 269 mg, 81%; Gummy mass; H NMR (CDCl3, 400 MHz) δ :
Cl
9.54 (s, 1H), 7.67 (d, J = 9.6 Hz, 1H), 7.44-7.41 (m, 3H), 7.25-7.19 (m,
13
3H), 7.06-7.00 (m, 5H); C NMR (CDCl3, 100 MHz) δ : 187.4, 155.2,
N
N
145.7, 138.3, 133.6, 132.1, 130.5, 130.2, 129.8, 128.6, 127.9, 126.3,
123.0, 120.3, 117.8; Anal. Calcd. For (%) C20H13ClN2O: C, 72.18; H,
3.94; N, 8.42. Found C, 72.23; H, 4.01; N, 8.31.
O
Ph
Ph
(6-Bromo-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3e):
1
Yield: 286 mg, 76%; Gummy mass; H NMR (CDCl3, 400 MHz ) δ :
Br
9.70 (s, 1H) 7.71 (d, J = 9.6 Hz, 1H), 7.58 (d, J = 9.2 Hz, 1H), 7.50 (d,
J = 8.0 Hz, 2H), 7.32-7.25 (m, 3H), 7.15-7.06 (m, 5H); 13C NMR
N
N
(CDCl3, 100 MHz) δ : 187.3, 154.8, 145.7, 141.2, 138.1, 133.4, 132.6,
O
Ph
132.1, 130.2, 129.6, 128.5, m128.3, 127.8, 117.9, 115.5, 109.5; Anal.
Ph
Calcd. For (%) C20H13BrN2O: C, 63.68; H, 3.47; N, 7.43. Found C,
63.80; H, 3.45; N, 7.47.
S5

(6-Iodo-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3f):
1
Yield: 335 mg, 79%; Gummy mass; H NMR (CDCl3, 400 MHz) δ :
I
9.78 (s, 1H), 8.09 (d, J = 6.4 Hz, 1H), 7.70-7.61 (m, 2H), 7.50-7.45 (m,
2H), 7.32-7.27 (m, 2H), 7.14-7.08 (m, 5H); 13C NMR (CDCl3, 100 MHz)
N
N
δ : 187.3, 154.3, 145.8, 138.1, 137.2, 133.0, 132.1, 130.2, 129.9, 129.6,
O
Ph
128.6, 128.3, 127.8, 119.7, 118.3, 78.0; Anal. Calcd. For (%)
Ph
C20H13IN2O: C, 56.62; H, 3.09; N, 6.60. Found C, 56.57; H, 3.29; N,
6.75
(4-Chloro-phenyl)-[2-(4-methoxy-phenyl)-7-methyl-imidazo[1,2-a]pyridin-3-yl]-methanone
(Table 2, 3g):
CH3
Yield: 287 mg, 76%; Gummy mass; 1H NMR (CDCl3, 400 MHz) δ
N
N
: 9.31 (d, J = 6.8 Hz, 1H), 7.51 (s, 1H), 7.32 (d, J = 6.8 Hz, 2H),
7.11 (d, J = 6.8 Hz, 2H), 6.99 (d, J = 6.8 Hz, 2H), 6.85 (d, J = 7.2
Cl
O
13
Hz, 1H), 6.53 (d, J = 8.8 Hz, 2H), 3.66 (s, 3H), 2.43 (s, 3H) ; C
OCH3
NMR (CDCl3, 100 MHz) δ : 185.5, 159.9, 154.8, 147.7, 141.3,
137.6, 137.1, 131.4, 130.8, 127.9, 127.3, 125,.9, 119.2, 117.2, 115.9, 113.3, 55.2, 21.5; Anal.
Calcd. For (%) C22H17ClN2O2: C, 70.12; H, 4.55; N, 7.43. Found C, 70.20; H, 4.67; N, 7.49.
(2-Benzo[1,3]dioxol-5-yl-imidazo[1,2-a]pyridin-3-yl)-phenyl-methanone (Table 2, 3h):
Yield: 284 mg, 83%; Gummy mass; 1H NMR (CDCl3, 400 MHz) δ : 9.49
(d, J = 6.8 Hz, 1H), 7.78 (d, J = 8.4 Hz, 1H), 7.52-7.49 (m, 3H), 7.29 (t,
N
N
J = 7.6 Hz, 1H), 7.14 (t, J = 7.6 Hz, 2H), 7.05 (t, J = 7.6 Hz, 1H), 6.85
O
(s, 1H), 6.75 (d, J = 8.0 Hz, 1H), 6.48 (d, J = 8.0 Hz, 1H), 5.83 (s, 2H);
Ph
13C NMR (CDCl3, 100 MHz) δ : 187.2, 154.3, 147.7, 147.2, 147.1,
O
O
138.7, 131.7, 129.4, 129.3, 128.1, 127.8, 127.6, 124.9, 119.6, 117.1,
S6

114.6, 110.1, 107.7, 101.0, 21.3; Anal. Calcd. For (%) C21H14N2O3: C, 73.68; H, 4.12; N, 8.18.
Found C, 73.77; H, 4.25; N, 8.23.
[2-(4-Chloro-phenyl)-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2, 3i):
1
Yield: 269 mg, 81%; Gummy mass; H NMR (CDCl3, 400 MHz) δ :
9.44 (d, J = 6.8 Hz, 1H), 7.73 (d, J = 8.8 Hz, 1H), 7.46 (d, J = 8.4 Hz,
N
N
1H), 7.42 (d, J = 8.0 Hz, 2H), 7.24 (t, J = 7.6 Hz, 1H), 7.17 (d, J = 8.8
O
Hz, 2H), 7.07-7.02 (m, 3H), 6.98 (d, J = 8.4 Hz, 2H); 13C NMR (CDCl3,
Ph
100 MHz) δ : 187.0, 153.3, 147.3, 138.4, 134.4, 132.4, 131.9, 131.3,
Cl
129.4, 129.3, 128.1, 127.8, 119.9, 117.3, 114.7; Anal. Calcd. For (%)
C20H13ClN2O: C, 72.18; H, 3.94; N, 8.42. Found C, 72.24; H, 4.13; N,
8.46.
[2-(4-Chloro-phenyl)-8-methyl-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2, 3j):
1
Yield: 263 mg, 76%; Gummy mass; H NMR (CDCl3, 400 MHz ) δ :
Me
9.41 (d, J = 6.4 Hz, 1H), 7.50 (d, J = 7.2 Hz, 2H), 7.36-7.27 (m, 4H),
N
7.14 (t, J = 7.6 Hz, 2H), 7.08-7.02 (m, 3H), 2.74 (s, 3H); 13C NMR
N
O
(CDCl3, 100 MHz) δ : 187.2, 153.1, 138.6, 134.2, 132.8, 131.8, 131.4,
Ph
129.4, 128.2, 127.9, 127.8, 127.5, 125.9, 114.8, 17.0; Anal. Calcd. For
(%) C21H15ClN2O: C, 72.73; H, 4.36; N, 8.08. Found C, 72.81; H, 4.51;
Cl
N, 8.13.
[2-(4-Chloro-phenyl)-7-methyl-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2,
3k):
Me
1
Yield: 270 mg, 78%; Gummy mass; H NMR (CDCl3, 400 MHz) δ : 9.43
N
N
(d, J = 7.2 Hz, 1H), 7.56 (s, 1H), 7.48 (d, J = 8.0 Hz, 2H), 7.32 (t, J = 7.6
O
Hz, 1H), 7.24 (d, J = 8.4 Hz, 2H), 7.13 (t, J = 8.0 Hz, 2H), 7.06 (d, J = 8.4
Ph
13
Hz, 2H), 6.94 (d, J = 7.2 Hz, 1H), 2.52 (s, 3H); C NMR (CDCl3, 100
Cl
MHz) δ : 186.8, 153.7, 147.8, 141.0, 138.6, 134.3, 132.6, 131.7, 131.3,
S7

129.4, 127.8, 127.4, 119.7, 117.2, 116.0, 21.5; Anal. Calcd. For (%) C21H15ClN2O: C, 72.73; H,
4.36; N, 8.08. Found C, 72.85; H, 4.51; N, 8.13.
[2-(3-Nitro-phenyl)-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2, 3l):
Yield: 277 mg, 81%; Gummy mass; 1H NMR (CDCl3, 400 MHz) δ :
9.47 (d, J = 7.2 Hz, 1H), 8.02 (s, J = 9.0 Hz, 1H), 7.90 (d, J = 8.8 Hz,
N
N
1H), 7.75 (d, J = 8.8 Hz, 1H), 7.62 (d, J = 8.0 Hz, 1H), 7.50 (t, J =
O
8.4 Hz, 1H), 7.40 (d, J = 8.4 Hz, 2H), 7.23-7.14 (m, 2H), 7.08 (t, J =
7.6 Hz, 1H), 7.0 (t, J = 8.0 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ :
Ph
NO2
186.9, 152.0, 147.5, 147.4, 138.4, 135.7, 132.1, 129.9, 129.4, 128.8,
128.4, 128.0, 125.3, 122.9, 120.4, 117.6, 115.3; Anal. Calcd. For (%) C20H13N3O3: C, 69.96; H,
3.82; N, 12.24. Found C, 70.13; H, 3.95; N, 12.29.
[7-Methyl-2-(3-nitro-phenyl)-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2, 3m):
1
Yield: 285 mg, 80%; Gummy mass; H NMR (CDCl3, 400 MHz) δ :
Me
9.42 (d, J = 7.2 Hz, 1H), 8.05 (s, 1H), 7.94 (d, J = 7.2 Hz, 1H), 7.67
(d, J = 7.6 Hz, 1H), 7.55 (s, 1H), 7.43 (d, J = 7.2 Hz, 2H), 7.28-7.18
N
N
(m, 2H), 7.05 (t, J = 7.6 Hz, 2H), 6.96 (d, J = 7.2 Hz, 1H), 2.50 (s,
O
3H); 13C NMR (CDCl3, 100 MHz) δ : 186.6, 152.2, 147.8, 147.3,
Ph
NO2
141.6, 138.6, 135.8, 135.6, 131.8, 129.3, 128.7, 127.9, 127.5, 125.2,
122.8, 120.1, 117.8, 116.1, 21.6; Anal. Calcd. For (%) C21H15N3O3: C, 70.58; H, 4.23; N, 11.76.
Found C, 70.63; H, 4.33; N, 11.86.
3-Phenyl-1-(2-phenyl-imidazo[1,2-a]pyridin-3-yl)-propenone (Table 2, 3n):
1
Yield: 269 mg, 83%; Gummy mass; H NMR (CDCl3, 400 MHz)
δ : 9.81 (d, J = 7.2 Hz, 1H), 7.79 (d, J = 8.8 Hz, 1H), 7.70-7.64
N
N
(m, 3H), 7.52-7.45 (m, 4H), 7.25-7.20 (m, 3H), 7.09 (d, J = 6.8
Hz, 2H), 7.05 (t, J = 6.8 Hz, 1H), 6.83 (d, J = 15.6 Hz, 1H) ; 13C
NMR (CDCl3, 100 MHz) δ : 180.5, 154.2, 146.9, 141.0, 134.8,
O
S8

130.5, 129.9, 129.5, 129.2, 128.9, 128.6, 128.4, 128.0, 125.3, 122.0, 117.1, 114.8; Anal. Calcd.
For (%) C22H16N2O: C, 81.46; H, 4.97; N, 8.64. Found C, 81.55; H, 5.134; N, 8.77.
1-(7-Methyl-2-phenyl-imidazo[1,2-a]pyridin-3-yl)-3-phenyl-propenone (Table 2, 3o):
1
Yield: 270 mg, 80%; Gummy mass; H NMR (CDCl3, 400 MHz)
Me
δ : 9.62 (d, J = 7.2 Hz, 1H), 7.61-7.54 (m, 3H), 7.44-7.39 (m,
4H), 7.18-7.12 (m, 3H), 7.01 (d, J = 6.8 Hz, 2H), 6.81 (d, J = 7.2
N
N
Hz, 1H), 6.75 (d, J = 15.6Hz, 1H), 2.37 (s, 3H) ; 13C NMR
(CDCl3, 100 MHz) δ : 180.2, 154.8, 147.6, 141.2, 140.6, 135.2,
134.9, 130.5, 129.9, 129.2, 128.7, 128.4, 128.2, 128.1, 125.4,
O
121.9, 117.3, 115.9, 21.5; Anal. Calcd. For (%) C23H18N2O: C, 81.63; H, 5.36; N, 8.28. Found C,
81.71; H, 5.47; N, 8.32.
[2-(4-Methoxy-phenyl)-imidazo[1,2-a]pyridin-3-yl]-phenyl-methanone (Table 2, 3p):
1
Yield: 242 mg, 74%; Gummy mass; H NMR (CDCl3, 300 MHz) δ :
9.48 (d, J = 6.0 Hz, 1H), 7.79 (d, J = 7.2 Hz, 1H), 7.50-7.44 (m, 3H),
N
N
7.26-7.22 (m, 3H), 7.11-7.00 (m, 3H), 6.58 (d, J = 6.9 Hz, 2H), 3.67
13
(s, 3H) ; C NMR (CDCl3, 75 MHz) δ : 187.4, 159.7, 154.6, 147.3,
O
146.3, 139.2, 138.6, 131.7, 131.5, 128.2, 127.8, 126.2, 119.6, 117.2,
OMe
114.5, 113.3, 55.2; Anal. Calcd. For (%) C21H16N2O2: C, 76.81; H,
4.91; N, 8.53. Found C, 76.79; H, 4.88; N, 8.50.
1-(2-Phenyl-imidazo[1,2-a]pyridin-3-yl)-ethanone (Table 2, 3q):
1
Yield: 61 mg, 26%; Gummy mass; H NMR (CDCl3, 400 MHz) δ : 9.80 (d, J
= 7.2 Hz, 1H), 7.72 (d, J = 8.8 Hz, 1H), 7.47-7.45 (m, 3H), 7.19-7.17 (m,
2H), 7.07-7.05 (m, 2H), 2.13 (s, 3H) ; 13C NMR (CDCl3, 100 MHz) δ : 192.0,
N
N
157.3, 145.9, 140.1, 139.0, 133.7, 133.0, 128.9, 128.5, 127.9, 123.2, 111.6,
O
21.8; Anal. Calcd. For (%) C15H12N2O: C, 76.25; H, 5.12; N, 11.86. Found C,
S9

76.21; H, 5.10; N, 11.83.
1,3-Diphenyl-3-(pyridin-2-ylamino)-propan-1-one (A):
Yield: 145 mg, 48%; Gummy mass; 1H NMR (CDCl3, 400 MHz) δ : 7.96
H
N
(d, J = 6.0 Hz, 1H), 7.84-7.81 (m, 2H), 7.48-7.41 (m, 1H), 7.39-7.32 (m,
4H), 7.29-7.20 (m, 3H), 7.19-7.17 (m, 1H), 6.47-6.44 (m, 1H), 6.27 (d, J =
8.4 Hz, 1H), 5.34-5.33 (m, 2H), 3.59-3.53 (m, 1H), 3.41-3.36 (m, 1H) ;
13C NMR (CDCl3, 100 MHz) δ :197.9, 157.7, 148.0, 142.4, 137.4, 136.7,
133.2, 128.6, 128.5, 128.1, 127.2, 126.4, 113.3, 107.4, 52.5, 45.6; Anal.
N
O
Calcd. For (%) C20H18N2O: C, 79.44; H, 6.00; N, 9.26. Found C, 79.53; H, 6.12; N, 9.13.
2. References:
1. Vogel's Textbook of Practical Organic Chemistry (5th Edition) [A.I. Vogel, A.R. Tatchell,
B.S. Furnis, A.J. Hannaford, P.W.G. Smith], Page No: 1034.
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