One-Pot Allan–Robinson/Friedl?nder Route to Chromen-/Quinolin-4-ones through the Domino Acetylative Cyclisation of 2-Hydroxy-/2-Aminobenzaldehydes

Article abstract of DOI:10.1002/ejoc.201701435

The domino synthesis of 2-phenyl-4H-chromen-4-ones and quinolin-4-ones through acetylation of 2-hydroxy-/2-aminobenzaldehydes with α-haloketones followed by intramolecular oxa-/azaheterocyclisation is reported. This method represents a new extension of the Allan–Robinson and Friedl?nder reactions, and uses N-heterocyclic-carbene catalysis to construct the target molecules in good to excellent yields: 86–95 % for the chromen-4-ones, and 83–96 % for the quinolin-4-ones. This approach has the advantages of operational simplicity, ambient reaction conditions, and no by-product formation.

Full text of DOI:10.1002/ejoc.201701435

A Journal of
Accepted Article
Title: One-pot Allan-Robinson/Friedländer route to Chromen-/
Quinolin-4-one via Domino Acetylative Cyclisation of 2-
Hydroxy-/2-Aminobenzaldehyde
Authors: Vijai Kumar Rai, Manorama Singh, Ankita Rai, Fooleswar
Verma, and Ganeswar P. Sahu
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201701435
Link to VoR: http://dx.doi.org/10.1002/ejoc.201701435
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10.1002/ejoc.201701435
European Journal of Organic Chemistry
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One-pot Allan-Robinson/Friedländer route to Chromen-/Quinolin-
4-one via Domino Acetylative Cyclisation of 2-Hydroxy-/2-
Aminobenzaldehyde
Vijai K. Rai,* [a] Fooleswar Verma,[a] Ganeshwar P. Sahu,[a] Manorama Singh[a] and Ankita Rai[b]
Abstract: Domino synthesis of 2-phenyl-4H-chromen-4-ones and quinolin-4-ones via acetylation of 2-hydroxy/-2-aminobenzaldehyde with α-
haloketones followed by intramolecular oxa-/azaheterocyclization is reported. The envisaged method is novel extension of Allan-Robinson and
Friedländer reaction using N-heterocyclic carbene catalysis to construct target molecules in good to excellent yield; 86-95% of chromen-4-ones
and 83-96% of quinolin-4-ones and has advantage of its operational simplicity, no by-product formation, and ambient reaction conditions.
Introduction
On demand, there are scores of natural products has concerned
2-phenyl-4H-chromen-4-ones moiety, also called flavones which
represent a fundamental function in natural products,1 drugs,2 and
contribute a wide variety of considerable biologically activities.3
From synthetic point of view, flavones have been well utilized as
platform chemical for expansion of different types of their
derivatives to generate a library of drugs and natural products.4-5
Literature reports a good number of synthetic strategies (Scheme
1)5-8 for construction of 2-phenyl-4H-chromen-4-ones employing
various types of reagents viz., Rh, Pd/IL, Fe(OTf)3, microwave
irradiation, additional oxidants, base, PhI(OAc)2, I2/SbCl3 etc.9,10
However, these reported methods undergo one or more
drawbacks such as harsh reaction conditions, poor substituent
Scheme 1. Various routes to substituted 2-phenyl-4H-chromen-4-one.
scope, multistep synthesis, low yield of pure products and thus
construction of 2-phenyl-4H-chromen-4-one is still challenging
task in organic synthesis.
short of regiocontrol. Keeping this point in mind, we chose α-
N-Heterocyclic carbene (NHC) catalyst has cooperated
haloketone as an alternative ketone component of Allan–
Robinson reaction, which would not only avoid the problem of
tremendous job for coupling of carbon-carbon bond, especially
activation of aldehydes, α-functionalized aldehydes, ketones, and
regiocontrol but would also be a novel and potential substrate for
enals to development of new scaffolds and new reactions.11 The
intramolecular oxa-heterocyclization affording a library of 2-
umpolung strategy for conversion of electrophilic into nucleophilic
aldehydes has the valuable beauty of NHC-catalyst,12 which
phenyl-4H-chromen-4-ones. Herein, we disclose an NHC-
catalyzed efficient synthesis of 2-phenyl-4H-chromen-4-ones via
acetylation of 2-hydroxybenzaldehyde 1 with α-haloketones 2
followed by intramolecular oxa-heterocyclization cascades
(Scheme 2). The envisaged protocol is hitherto unreported and is
the outcome of our interest to expand synthetically useful
processes for biologically and pharmaceutically important
molecules.14,15
cultivates a new carbon-carbon bond and shortens the usual
synthetic corridor in organic synthesis.13 Since 1924, Allan-
Robinson reaction1 has been explored for synthesis of 2-phenyl-
4H-chromen-4-one (flavones),1-5 which involves base catalyzed
condensation between o-hydroxyaryl ketones and an anhydride
of aromatic acid. Later on, substrate scope of this method was
tolerated by o-acyl phenols and carboxylic acid derivatives.
Allan–Robinson reaction is still attractive process to
fabricate flavone ring due to presence of a variety of functional
group in the substrates. Though, a broad range of functional
groups is recognized on the aromatic ring in o-hydroxy aldehyde
constituent, the construction of the reactive species has been
[a]
[b]
Department of Chemistry, Guru Ghasidas Vishwavidyalaya,
Bilaspur–495 009, C. G., India.
E-mail: vijaikrai@hotmail.com
School of Physical Sciences, Jawaharlal Nehru University, New
Delhi–110 027. India
Scheme 2. Synthesis of substituted 2-phenyl-4H-chromen-4-one 3.
Supporting information for this article is given via a link at the end of
the document.
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Results and Discussion
increasing the amount of pre-catalyst up to 25 mol %, yield of
product 3a was same (Table 1, entry 10), while on decreasing the
amount of pre-catalyst from 20 to 15 mol %, the yield of product
3a was also reduced (Table 1, entry 11). Next, we also checked
the role of pre-catalyst in present conversion and a reaction was
set up containing a mixture of salicylaldehyde 1a (2.0 mmol) and
phenacyl bromide 2a (2.0 mmol) in 10 mL of THF-ButOH under
positive pressure of nitrogen followed by addition of DBU (0.4
mmol) in absence of benzimidazolium salt 4c. No product
formation even after prolonged reaction time confirms not only the
essential role of pre-catalyst 4c but also rules out the possibility
of amine catalysis in the present conversion (Table 1, entry 12).
Thus, 20 mol % of each pre-catalyst 4c and DBU in THF-ButOH
has been found the best reaction condition for preparation of 2-
phenyl-4H-chromen-4-one 3a (Table 1).
In model experiment, salicylaldehyde 1a (2 mmol) and phenacyl
bromide 2a (2mmol) were taken as substrate and different NHC
inventor 4a-f catalyst (Figure 1), stirring in hot air-dried round
bottom flask at room temperature and results are sum up in Table
1. NHC-catalyst 4c was found to be the most efficient among
different NHC precursors 4a-f for synthesis of product 3a (Table
1, entries 1-6). To generate the NHC, 20% of DBU was used as
base with 20 mol % of pre-catalyst 4c for the best result (Table 1,
entries 1-6). Furthermore, we have screened various solvents for
the formation of 3a and THF-ButOH was found the best solvent
system among THF-H2O, THF-ButOH, DCM and THF-MeOH
(Table 1, entries 6-9). However, for conversion of product 3a, we
have also monitored the role of pre-catalyst in model reaction. On
After optimization of reaction conditions, we next
investigated the substrate scope for the envisaged reaction and a
variety of substituted salicyldehyde 1 and phenacyl bromide 2
were used employing present reaction condition affording good to
excellent yield of target molecule 3 (Figure 2). The substituent on
the benzene ring of substrate did not show any specific effect over
the product outcome as well as conversion rate (Fig. 2). For
generality of the envisaged process, total 17 products have been
synthesized with the highest yield (95%) of product 3j. The
formation of product was confirmed by their 1H NMR and 13C
spectral analysis.
Figure 1. Screening of catalyst 4a-f.
Table 1. Optimization experiment for synthesis of 3a [a]
.
The formation of 2-phenyl-4H-chromen-4-one 3 may be
explained (Scheme 3) presumably by nucleophilic attack of
carbene 4 to carbonyl carbon of salicyldehyde 1 followed by
proton shift in 5 generating homoenolate 6. The homoenolete 6
(d1 nucleophile) then attacked to phenacyl bromide 2, resulting
adduct 7 which further underwent intramolecular oxa-
Entry
Pre-catalyst
4 (mol %)
Solvent [b]
Time (h)[c]
Yield (%)[d,e]
1
4a (20)
4b (20)
4d (20)
4e (20)
4f (20)
4c (20)
4c (20)
4c (20)
4c (20)
4c (25)
4c (15)
-
THF-ButOH
THF-ButOH
THF-ButOH
THF-ButOH
THF-ButOH
THF-ButOH
DCM
5
5
5
5
5
5
6
5
5
5
5
6
41
27
38
36
50
90
42
65
62
90
79
00
2
3
4
5
6
7
8
THF-MeOH
THF-H2O
9
10
11
12
THF-ButOH
THF-ButOH
THF-ButOH
[a] For the detail pl see the general method of preparation. [b] THF-MeOH
(10:01) and THF-H2O (10:01) were used. [c] Time for stirring at room
temperature. [d] Yield of isolated and purified product. [e] All compounds
gave C and H analyses within ± 0.37 %, and satisfactory spectral (1H NMR,
13C NMR and EIMS) data.
Figure 2. Substrate scope for the formation of 2-phenyl-4H-chromen-4-one 3.
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Scheme 3. Plausible mechanism for the formation of Flavones 3.
heterocyclization proton shifting cascades to produce adduct 8. In
the last step, presumably enhanced stability of conjugated double
bond of 3 has been the driving force for dehydration of 8 (Scheme
3).
Quinolines are the most common structural motifs found in
natural (cinchona alkaloids) and synthetic products, displaying a
wide range of biological activities16,17 with enhanced electronic
and photonic functions.18 Literature documents a good number of
synthetic routes for construction of quinoline ring including Skraup,
Doebner-von Miller, Friedländer and Combes methods.19-29
Friendläender reaction is still attractive method to construct
quinoline ring due to the observed broad range of functional group
is tolerated on the aromatic ring in aromatic o-amino aldehyde
component, lack of regiocontrol in functional group compatibility
in the substrates. Though, a wide the formation of the reactive
species, derived from the ketone component still opens up new
substrate hope with α-metylene carbonyl moiety. As a probe to
check the general validity of the envisaged synthetic methodology
and to construct quinoline ring keeping in mind, we extended the
scope of aldehyde component from o-hydroxy- to o-amino
benzaldehyde for synthesis of quinolin-4-ones 10. Thus, after
preliminary experimentation, 2-aminobenzaldehyde 9 (2 mmol),
phenacyl bromide 2 (2mmol), pre-catalyst 4c (20 mol%) and DBU
(20 mol%) were taken in THF-ButOH for synthesis of quinoline 10
(Figure 3). Total 12 products were synthesized in good to
excellent yield with the highest yield of 10e as 96%. Both electron
releasing (-Me, -OMe, -NH2) as well as electron withdrawing (-Br,
-Cl, -F, -NO2) groups tolerated the product yield good to excellent
in this conversion. All the synthesized products 10 were confirmed
by their 1H NMR and 13C NMR spectra.
Figure 3. Substrate scope for the formation of quinoline-4-ones 10.
the synthesized molecules may serve platform chemical for
generating a library of biologically relevant molecules and would
be a practical alternative to the existing procedures for their
preparations.
Experimental Section
General: All chemicals were purchased from Aldrich, Sd-Fine and Hi-
Media (India) and used as received, except all solvents which were used
after distillation. All reactions were carried out with oven-dried glassware
under air. Distilled n- hexane and ethyl acetate were used for column
chromatography. Analytical TLC was performed on Merck 60F254 silica
gel plates (0.25 mm thickness). Column chromatography was performed
on silica gel (60-120 mesh size, Hi-Media (India). 1H NMR spectra were
recorded on Bruker AV 400.
The 1H NMR chemical shifts are reported relative to the centre of
solvent resonance (CDCl3: 7.26 (1H). Chemical shifts are expressed in
parts per million (δ) and the signals were reported as s (singlet), d (doublet),
dd (double doublet), t (triplet), tt (triplet triplet), dt (doublet triplet), q
(quartet), m (multiplet) and coupling constants J were given in Hz. 13C
NMR spectra were recorded at 100 MHz in CDCl3 and DMSO-d6 solution.
Chemical shifts are expressed in parts per million (δ) and are referenced
to CDCl3 (δ = 77.16) as internal standard.
Conclusions
We have developed a domino synthesis of 2-phenyl-4H-chromen-
4-one and quinolin-4-one via dehydrative acetylation of different
o-substituted aldehyde with α-haloketone followed by
intramolecular heterocyclization, which is hitherto unknown and
has advantage of its operational simplicity, atom economy, no by-
product formation and ambient reaction conditions. Furthermore,
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Experiment procedure for 2-phenyl-4H-chromen-4-one (3): The 2-
hydroxybenzaldehyde 1 (2.0 mmol), phenacyl bromide 2 (2.0 mmol) were
taken in the hot air-dried round bottom flask. Benzimidazolium salt 4c (0.4
mmol) and 10 mL of THF/ButOH; 10:1 under positive pressure of nitrogen
followed by addition of DBU (0.4 mmol) with a syringe. The resulting
solution was stirred for 5-6 h at room temperature. After completion of the
reaction (monitored by TLC), the reaction mixture was concentrated under
reduced pressure. The residue was purified by flash column
chromatography on silica gel using n-hexane/EtOAc (8:2) as eluent to
afford analytically pure product 3. Characterization data of the
representative compounds are:
2-(3,5-Difluorophenyl)-4H-chromen-4-one (3g): Yellowish solid (94%);
mp 146–147 °C; H NMR (400 MHz, CDCl3) δ 8.21 (dd, J = 7.9, 1.7 Hz,
1
1H), 7.58–7.42 (m, 5Harom.), 6.98 (tt, 1H), 6.76 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 178.1, 164.6, 162.1, 160.6, 156.1, 135.1 (d, J = 9.4 Hz), 134.2,
125.8, 123.8, 118.1, 109.5, 108.5, 107.1; IR (KBr): 1640, 1378, 1122 cm−1
;
Anal. Calcd for C15H8F2O2: C, 69.77, H, 3.12%; Found: C, 69.47, H, 3.49%.
2-(3,4-Dichlorophenyl)-4H-chromen-4-one (3h): Yellowish solid (92%);
1
mp 196–199 °C; H NMR (400 MHz, CDCl3) δ 8.20 (dd, J = 7.9, 1.7 Hz,
1H), 8.01 (d, J = 2.2 Hz, 1H), 7.72 (td, J = 8.5, 6.5, 1.9 Hz, 2H), 7.63 (td, J
= 9.3, 8.0 Hz, 2H), 7.42 (td, 1H), 6.69 (s, 1H); 13C NMR (100 MHz, CDCl3)
δ 178.1, 160.8, 156.0, 135.9, 134.1, 133.7, 131.7, 131.1, 128.0, 125.8,
125.5, 125.2, 123.9, 118.0, 108.2; ; IR (KBr): 1663, 1605, 1470, 1131
cm−1; Anal. Calcd for C15H8Cl2O2: C, 61.88, H, 2.77%; Found: C, 61.77, H,
2.85.
2-Phenyl-4H-chromen-4-one (3a): Colourless solid (90%); mp 95-96 °C;
1H NMR (400 MHz, CDCl3) δ 8.25 (dd, J = 8.0, 1.7 Hz, 1H), 7.95–7.45 (m,
8Harom.), 7.06 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 178.5, 164.5, 156.4,
134.4, 132.1, 131.3, 129.1, 126.5, 125.7, 125.6, 123.1, 118.1, 106.9; IR
(KBr): 1640, 1605, 1375, 1130 cm−1; Anal. Calcd for C15H10O2: C, 81.07,
H, 4.54%; Found: C, 81.26, H, 4.65%.
2-(4-Chlorophenyl)-4H-chromen-4-one (3i): Colourless solid (90%); mp
177–178 °C; 1H NMR (400 MHz, CDCl3) δ 8.23 (dd, J = 8.0, 1.6 Hz, 1H),
7.86 (d, 2H), 7.70 (td, J = 8.7,0 7.1, 1.7 Hz, 1H), 7.56 (d, J = 8.4 Hz, 1H),
7.49 (d, 2H), 7.42 (t, J = 7.6 Hz, 1H), 6.78 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 178.1, 162.6, 156.2, 137.8, 133.9, 130.2, 129.3, 127.5, 125.7,
2-(2-Methoxyphenyl)-4H-chromen-4-one (3b): Colourless solid (92%);
mp 97–100 °C; 1H NMR (400 MHz, CDCl3) δ 8.24 (dd, J = 8.0, 1.7 Hz, 1H),
7.89 (dd, J = 7.8, 1.8 Hz, 1H), 7.65 (td, J = 8.7, 7.1, 1.7 Hz, 1H), 7.52 (d,
1H), 7.45 (td, 1H), 7.38 (td, J = 8.1, 7.1, 1.1 Hz, 1H), 7.12 (s, 1H), 7.09 (td,
J = 7.6, 1.0 Hz, 1H), 7.02 (d, 1H), 3.91 (s, 3H); 13C NMR (100 MHz, CDCl3)
δ 178.5, 160.8, 158.0, 156.5, 133.6, 132.4, 129.2, 125.6, 124.9, 123.8,
125.3, 123.9, 117.1, 108.0; IR (KBr): 1660, 1375, 1093, 827, 754 cm−1
;
Anal. Calcd for C15H9ClO2: C, 70.19, H, 3.53%; Found: C, 70.56, H, 3.16%.
2-(4-Nitrophenyl)-4H-chromen-4-one (3j): Yellowish solid (95%); mp
120.8, 120.7, 118.0, 112.6, 111.7, 55.9; IR (KBr): 1638, 1615, 1462 cm−1
;
1
232–235 °C; H NMR (400 MHz, CDCl3) δ 8.38 (d, J = 9.0 Hz, 2H), 8.24
Anal. Calcd for C16H12O3: C, 76.18, H, 4.79%; Found: C, 76.55, H, 4.65%.
(dd, J = 7.9, 1.7 Hz, 1H), 8.11 (d, J = 8.9 Hz, 1H), 7.74 (td, J = 8.6, 7.1, 1.7
Hz, 1H), 7.60 (dd, J = 8.5, 1.0 Hz, 1H), 7.45 (td, J = 8.2, 7.1, 1.1 Hz, 1H),
6.80 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 176.6, 164.1, 159.1, 144.8,
132.3 130.7, 129.2, 128.1, 126.4, 124.2, 122.4, 119.8, 107.8; IR (KBr):
1660, 1523, 1347, 857 cm−1; Anal. Calcd for C15H9NO4: C, 67.42, H, 3.39,
N, 5.24%; Found: C, 67. 24, H, 3.46, N, 5.18%.
2-(3-Fluorophenyl)-4H-chromen-4-one (3c): Colourless solid (88%); mp
97–98 °C; 1H NMR (400 MHz, CDCl3) δ 8.23 (dd, J = 7.9, 1.7 Hz, 1H),
7.68-7.24 (m, 7Harom.), 6.78 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 178.7,
163.0 (d, J = 241.7 Hz), 156.1, 134.0, 133.9, 133.9, 130.7 (d, J = 8.1 Hz),
125.7, 125.4, 123.9, 121.9 (d, J = 3.1 Hz), 118.5 (d, J = 21.2), 118.0, 113.3
(d, J = 23.9 Hz), 108.2; IR (KBr): 1664, 1642, 1510, 1376 cm−1; Anal.
Calcd for C15H9FO2: C, 75.00, H, 3.78%; Found: C, 75.25, H, 3.85%.
2-(p-Tolyl)-4H-chromen-4-one (3k): Yellowish solid (87%); mp 105–
107 °C; 1H NMR (400 MHz, CDCl3) δ 8.22 (dd, J = 7.9, 1.7 Hz, 1H), 7.82-
7.24 (m, 7Harom.), 6.93 (s, 1H), 2.42 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
178.4, 164.3 156.3, 142.7, 134.0, 129.8, 128.6, 126.4, 125.6, 125.4, 123.3,
118.1, 106.4, 21.5; IR (KBr): 1642, 1468, 815 cm−1; Anal. Calcd for
C16H12O2: C, 81.34, H, 5.12%; Found: C, 81.44, H, 5.02%.
2-(3-Nitrophenyl)-4H-chromen-4-one (3d): Colourless solid (91%); mp
1
196–198 °C; H NMR (400 MHz, CDCl3) δ 8.80 (t, J = 2.0 Hz, 1H), 8.37
(ddd, J = 8.2, 2.4, 1.0 Hz, 1H), 8.22 (dq, J = 7.8, 1.7 Hz, 2H), 7.76–7.70
(m, 2Harom.), 7.63 (dd, J = 8.5, 1.1 Hz, 1H), 7.45 (td, J = 8.1, 7.0, 1.1 Hz,
1H), 6.89 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 177.1, 161.0, 156.8, 148.5,
134.3, 133.6, 131.7, 130.3, 125.9, 125.8, 125.7, 123.9, 121.2, 118.1,
108.8; IR (KBr): 1661, 1619, 1459, 1369 cm−1; Anal. Calcd for C15H9NO4:
C, 67.42, H, 3.39, N, 5.24%; Found: C, 67.25, H, 3.45, N, 5.15%.
2-(4-Methoxyphenyl)-4H-chromen-4-one (3l): Yellowish solid (89%); mp
151–152 °C; 1H NMR (400 MHz, CDCl3) δ 8.23 (dd, J = 8.0, 1.7 Hz, 1H),
7.92 (d, 2H), 7.73 (td, J = 8.7, 7.1, 1.7 Hz, 1H), 7.60 (dd, J = 8.5, 1.0 Hz,
1H), 7.44 (td, J = 8.0, 7.1, 1.0 Hz, 1H), 7.11 (bs, 1H), 7.01 (d, 2H), 3.91 (s,
3H); 13C NMR (100 MHz, CDCl3) δ 178.1, 165.4, 163.3, 156.3, 134.6,
128.7, 125.8, 125.6, 123.1, 122.3, 118.1, 114.7, 104.8, 55.6; IR (KBr):
1642, 1378, 827 cm−1; Anal. Calcd for C16H12O3: C, 76.18, H, 4.79%;
Found: C, 76.44, H, 5.02%.
2-(3-Methoxyphenyl)-4H-chromen-4-one (3e): Colourless solid (89%);
1
mp 125–127 °C; H NMR (400 MHz, CDCl3) δ 8.24 (dd, J = 8.0, 1.7 Hz,
1H), 7.69 (td, J = 8.7, 7.0, 1.7 Hz, 1H), 7.55 (d, 1H), 7.49 (dt, J = 7.7, 1.4
Hz, 1H), 7.44 (d, J = 3.2 Hz, 1H), 7.43–7.39 (m, 2Harom.), 7.06 (ddd, J = 8.1,
2.6, 1.1 Hz, 1H), 6.81 (s, 1H), 3.88 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
178.4, 163.1, 159.7, 156.2, 133.7, 133.0, 130.1, 125.6, 125.2, 123.9, 118.7,
118.1, 117.1, 111.4, 107.7, 55.9; IR (KBr): 1650, 1605, 1464, 867, 767,
693 cm−1; Anal. Calcd for C16H12O3: C, 76.18, H, 4.79%; Found: C, 75.95,
H, 5.16%.
7-Methoxy-2-phenyl-4H-chromen-4-one (3m): Colourless solid (91%);
1
mp 86–88 °C; H NMR (400 MHz, CDCl3) δ 8.12-8.05 (m, 1Harom.), 7.92
(dd, J = 7.8, 1.9 Hz, 2H), 7.50–7.48 (m, 3H), 6.99-6.96 (m, 2Harom.), 6.92
(s, 1H); 13C NMR (100 MHz, CDCl3) δ 177.8, 164.5, 163.7, 158.1, 131.7,
131.5, 129.0, 127.0, 126.3, 117.3, 114.9, 106.8, 100.1, 55.9; IR (KBr):
1650, 1627, 1445, 1152, 1018 cm−1; Anal. Calcd for C16H12O3: C, 76.18,
H, 4.79%; Found: C, 76.25, H, 4.95%.
2-(3-Bromophenyl)-4H-chromen-4-one (3f): Yellowish solid (93%); mp
85–89 °C; 1H NMR (400 MHz, CDCl3) δ 8.20 (dd, J = 8.0, 1.7 Hz, 1H), 8.05
(t, J = 1.9 Hz, 1H), 7.79-7.35 (m, 6Harom.), 6.68 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 178.0, 161.6, 156.0, 134.4, 133.9, 133.7, 130.5, 129.2, 125.7,
125.4, 124.8, 123.9, 123.2, 118.0, 108.1; IR (KBr): 1642, 1605, 1470,
1366 cm−1; Anal. Calcd for C15H9BrO2: C, 59.83, H, 3.01%; Found: C,
60.15, H, 3.06%.
6-Fluoro-2-phenyl-4H-chromen-4-one (3n): Yellowish solid (86%); mp
125–127 °C; 1H NMR (400 MHz, CDCl3) δ 7.92-7.82 (m, 3Harom.), 7.56–
7.50 (m, 5Harom.), 6.80 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 177.3, 163.6,
160.8, 158.4, 152.5, 131.6 (d, J = 30.6 Hz), 129.1, 126.3, 125.1 (d, J = 7.1
Hz), 121.9 (d, J = 25.4 Hz), 120.1 (d, J = 8.1 Hz), 110.6 (d, J = 23.6 Hz),
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10.1002/ejoc.201701435
European Journal of Organic Chemistry
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106.9; IR (KBr): 1658, 1357 cm−1; Anal. Calcd for C15H9FO2: C, 75.00, H,
3.78%; Found: C, 75.30, H, 3.65%.
7-Chloro-2-(4-fluorophenyl) quinolin-4-one (10d): Solid (93%); 1H NMR
(400 MHz, DMSO-d6) δ 11.73 (br s, 1H), 8.12 (d, J = 8.6 Hz, 1H), 7.92−7.89
(m, 2Harom.), 7.78 (s, 1H), 7.46 (t, J = 8.8 Hz, 2H), 7.37 (dd, J = 8.6, 1.7 Hz,
1H), 6.30 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 169.6, 141.9, 131.3,
131.2, 128.2, 125.4, 119.0, 118.2, 116.6, 116.4, 104.0; Anal. Calcd for
C15H10ClFNO: C, 65.83, H, 3.31, N, 6.94%; Found: C, 65.63, H, 3.66, N,
6.75%.
6-Chloro-2-phenyl-4H-chromen-4-one (3o): Yellowish solid (91%); mp
1
177–180 °C; H NMR (400 MHz, CDCl3) δ 8.18 (d, J = 2.5 Hz, 1H), 7.89
(dd, 2H), 7.60–7.50 (m, 5Harom.), 6.87 (s, 1H); 13C NMR (100 MHz, CDCl3)
δ 177.4, 163.8, 154.6, 133.9, 131.8, 131.4, 131.2, 129.1, 126.3, 125.1,
124.9, 119.1, 107.5; IR (KBr): 1651, 1604, 1433, 1130, 679 cm−1; Anal.
Calcd for C15H9ClO2: C, 70.19, H, 3.53%; Found: C, 70.50, H, 3.45%.
2-(4-Fluorophenyl)-6-nitroquinolin-4-one (10e): Yellowish solid (96%);
1H NMR (400 MHz, DMSO-d6) δ 8.48 (d, J = 2.7 Hz, 1H), 7.95 (dd, J = 9.2,
2.7 Hz, 1H), 7.67 (s, 1H), 7.28−7.15 (m, 4Harom.), 6.68 (d, J = 9.2 Hz, 1H),
5.67 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 187.6, 163.6 (d, J = 244.4
Hz), 161.8, 155.3, 134.3, 133.1 (d, J = 3.5 Hz), 130.1 (d, J = 8.3 Hz), 126.9,
126.7, 120.0, 115.8, 115.2 (d, J = 21.6 Hz), 93.3; Anal. Calcd for
C15H10FN2O3: C, 63.38, H, 3.19, N, 6.68%; Found: C, 63.21, H, 3.01, N,
7.03%.
6-Bromo-2-phenyl-4H-chromen-4-one (3p): Yellowish solid (92%); mp
1
172–175 °C; H NMR (400 MHz, CDCl3) δ 8.38 (d, J = 2.4 Hz, 1H), 7.91
(dd, J = 8.0, 1.7 Hz, 2H), 7.78 (dd, J = 8.9, 2.5 Hz, 1H), 7.54–7.46 (m,
4Harom.), 6.84 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 177.0, 163.9, 155.1,
137.0, 132.0, 131.3, 129.1, 128.4, 126.4, 125.1, 120.0, 118.8, 107.4; IR
(KBr): 1650, 1598, 1453, 1435 cm−1; Anal. Calcd for C15H9BrO2: C, 59.83,
H, 3.01%; Found: C, 60.12, H, 3.15%.
6-Nitro-2-phenylquinolin-4-one (10f): Yellowish solid (92%); 1H NMR
(400 MHz, DMSO-d6) δ 8.42 (s, 1H), 7.92 (d, J = 12.0 Hz, 1H), 7.39–7.22
(m, 4Harom.), 6.60 (d, J = 8.0 Hz, 1H), 5.82 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) δ 187.5, 162.8, 155.3, 136.8, 134.3, 128.1, 128.0, 127.5, 126.8,
126.7, 120.1, 115.8, 93.8; IR (KBr): 3019, 1615, 1513, 1319 cm−1; Anal.
Calcd for C15H10N2O3: C, 67.67, H, 3.79, N, 10.52%; Found: C, 67.48, H,
3.67, N, 10.65%.
6-Nitro-2-phenyl-4H-chromen-4-one (3q): Yellowish solid (93%); mp
185–187 °C; 1H NMR (400 MHz, CDCl3) δ 9.07 (d, J = 2.8 Hz, 1H), 8.53(dd,
J = 9.2, 2.8 Hz, 1H), 7.91 (dd, J = 8.2, 1.6 Hz, 2H), 7.71 (d, J = 9.2 Hz, 1H),
7.56–7.52 (m, 4Harom.), 6.90 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 176.8,
164.0, 159.0, 144.6, 132.3, 130.7, 129.2, 128.1, 126.4, 124.0, 122.4, 119.8,
107.8; IR (KBr): 1648, 1614, 1510, 1456, 1337, 1018 cm−1; Anal. Calcd
for C15H9NO4: C, 67.42, H, 3.39%; Found: C, 67.54, H, 3.51%.
6-Bromo-2-phenylquinolin-4-one (10g): Yellowish solid (91%); 1H NMR
(400 MHz, DMSO-d6) δ 8.31 (s, 1H), 8.22 (d, J = 8.0 Hz, 1H) 7.88 (d, J =
Experiment procedure for 2-Phenylquinolin-4-one (10): A hot oven
dried round bottom flask was charged with benzimidazolium salt 4c (0.4
mmol). 2-aminobenzaldehyde 9 (2.0 mmol), phenacyl bromide 2 (2.0
mmol) and 10 mL of THF/ButOH; 10:1 under positive pressure of nitrogen
followed by addition of DBU (0.4 mmol) with a syringe. The resulting yellow
solution was stirred for 4-5 h at room temperature. After completion of the
reaction (monitored by TLC), the reaction mixture was concentrated under
reduced pressure. The residue was purified by flash column
chromatography on silica gel using n-hexane/EtOAc (8:2) as eluent to
afford analytically pure product 10. Characterization data of the
representative compounds are:
8.0 Hz, 1H) 7.85–7.81 (m, 2Harom.), 7.48-7.42 (m, 3Harom.), 7.34 (s, 1H); 13
C
NMR (100 MHz, DMSO-d6) δ 168.2, 156.8, 138.7, 137.9, 132.7, 130.8,
129.5, 128.4, 126.0, 121.8, 121.6, 120.7, 104.7; Anal. Calcd for
C15H10BrNO: C, 60.02, H, 3.36, N, 4.67%; Found: C, 60.37, H, 3.07, N,
4.65%.
6-Methyl-2-phenylquinolin-4-one (10h): Solid (88%); 1H NMR (400 MHz,
DMSO-d6) δ 8.05 (d, J = 8.0 Hz, 1H), 7.71-7.43 (m, 7Harom.), 6.71 (s, 1H),
2.49 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ 179.7, 151.6, 139.1, 134.7,
134.6, 134.4, 131.0, 129.4, 127.7, 125.0, 124.6, 118.7, 107.0, 21.6; Anal.
Calcd for C16H13NO: C, 81.68, H, 5.57, N, 5.95%; Found: C, 81.99, H, 5.37,
N, 5.67%.
2-Phenylquinolin-4-one (10a): Solid (92%) m.p. 251–254 °C; 1H NMR
(400 MHz, DMSO-d6) δ 8.31 (d, J = 8.0 Hz, 1H), 8.28 (d, J = 8.0, 1H), 7.83-
7.77 (m, 3Harom.), 7.75 (d, J = 8.0 Hz, 2H), 7.60 (t, J = 7.2 Hz, 1H), 7.46 (t,
J = 7.2 Hz, 1H), 6.61 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 176.5,
150.9, 140.0, 134.7, 131.8, 130.4, 129.0, 127.4, 124.9, 124.7, 123.2, 118.7,
107.7; IR (KBr): 1629, 3259 cm−1; Anal. Calcd for C15H11NO: C, 81.43, H,
5.01, N, 6.33%; Found: C, 81.25, H, 5.15, N, 6.50%.
2-(4-Methoxyphenyl)quinolin-4-one (10i): Brown solid (88%); 1H NMR
(400 MHz, DMSO-d6) δ 11.52 (br, s, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.84 (dd,
J = 9.2, 2.7 Hz, 1H), 7.79 (dd, J = 9.2, 2.7 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H),
7.36−7.32 (m, 2Harom.), 7.18−7.14 (m, 2Harom.), 6.33 (s, 1H), 3.83 (s, 3H);
13C NMR (100 MHz, DMSO-d6) δ 176.0, 161.8, 149.6, 140.1, 131.6, 128.8,
126.2, 124.8, 124.7, 123.1, 118.6, 114.4, 106.4, 55.5; Anal. Calcd for
C16H13NO2: C, 76.48, H, 5.21, N, 5.57%; Found: C, 76.58, H, 5.37, N,
5.47%.
2-(4-Fluorophenyl)quinolin-4-one (10b): Solid (91%), m.p. 317-319 °C;
1H NMR (400 MHz, DMSO-d6) δ 11.71 (br, s, 1H), 8.12 (d, J = 12 Hz, 1H),
7.92 (d, J = 12 Hz, 2H), 7.76 (d, J = 8.0 Hz, 1H), 7.69 (t, J = 7.2 Hz, 1H),
7.44 (d, J = 8.0 Hz, 2H), 7.36 (t, J = 7.2 Hz, 1H), 6.33 (s, 1H); 13C NMR
(100 MHz, DMSO-d6) δ 176.1, 163.4 (d, J = 248.2 Hz), 149.4, 140.5, 131.9,
130.7 (d, J = 3.1 Hz), 129.9 (d, J = 8.8 Hz), 124.8, 124.7, 123.3, 118.7,
116.0 (d, J = 21.8 Hz), 107.0; Anal. Calcd for C15H10FNO: C, 75.30, H,
4.21, N, 7.94%; Found: C, 75.24, H, 4.35, N, 7.90%.
2-(4-Bromophenyl)quinolin-4-one (10j): Solid (93%); 1H NMR (400 MHz,
DMSO-d6) δ 11.5 (br, s, 1H), 8.17 (d, J = 8.0 Hz, 2H), 7.80 (dd, J = 9.2, 2.7
Hz, 1H), 7.77 (d, J = 8.0 Hz, 2H), 7.70−7.50 (m, 3Harom.), 7.17 (s, 1H); 13
C
NMR (100 MHz, DMSO-d6) δ 176.9, 148.5, 140.5, 133.3, 131.9, 131.9,
129.5, 124.9, 124.7, 124.0, 123.3, 118.7, 107.5; Anal. Calcd for
C15H10BrNO: C, 60.02, H, 3.36, N, 4.67%; Found: C, 60.12, H, 3.37, N,
4.47%.
7-Chloro-2-phenylquinolin-4-one (10c): Solid (89%); 1H NMR (400 MHz,
DMSO-d6) δ 8.47 (d, J = 12.0 Hz, 1H), 8.35 (d, J = 8.0 Hz, 1H), 7.99−7.96
(m, 2Harom.), 7.68−7.60 (m, 4Harom.), 7.45 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) δ 170.7, 157.4, 142.0, 141.2, 133.4, 131.5, 130.1 129.3, 129.0,
126.0, 119.9, 118.7, 104.0; Anal. Calcd for C15H11ClNO: C, 70.46, H, 3.94,
N, 5.48%; Found: C, 70.81, H, 3.69, N, 5.36%.
2-(2-Bromophenyl)quinolin-4-one (10k): Red solid (95%); 1H NMR (400
MHz, DMSO-d6) δ 7.69−7.61 (m, 2Harom.), 7.43 (td, J = 7.5, 1.2 Hz, 1H),
7.32 (ddd, J = 8.0, 7.4, 1.8 Hz, 1H), 7.24 (dd, J = 7.5, 1.7 Hz, 1H), 7.08
(ddd, J = 8.4, 7.1, 1.5 Hz, 1H), 6.60 (dd, J = 8.3, 1.2 Hz, 1H), 6.50 (ddd, J
= 8.1, 7.1, 1.2 Hz, 1H), 6.41 (br s, 1H), 5.67 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) δ 188.5, 158.8, 149.8, 138.3, 132.0, 131.3, 129.6, 129.4, 129.4,
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10.1002/ejoc.201701435
European Journal of Organic Chemistry
FULL PAPER
127.4, 121.9, 121.7, 116.3, 114.7, 93.8; Anal. Calcd for C15H11BrNO: C,
60.02, H, 3.36, N, 4.67%; Found: C, 60.22, H, 3.47, N, 4.27%.
[6]
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2-(4-Aminophenyl)quinolin-4-one (10l): Yellowish solid (83%); 1H NMR
(400 MHz, DMSO-d6) δ 11.7 (br s, 1H), 8.3 (dd, J = 8.1, 1.5 Hz, 1H), 7.8
(d, J = 8.3 Hz, 1H), 7.7−7.6 (m, 3Harom.), 7.3 (ddd, J = 8.0, 6.9, 1.1 Hz, 1H),
6.7- 6.6 (m, 2Harom.), 6.6 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 176.8,
151.8, 150.6, 140.4, 131.4, 128.3, 124.5, 122.9, 120.1, 118.5, 113.6,
104.4; 1629; IR 3428 cm−1; Anal. Calcd for C15H13N2O: C, 76.25, H, 5.12,
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Acknowledgements
We sincerely thank the SERB (No.–SR/FT/CS-99/2010), DST,
New Delhi, Government of India, for financial support and AIRF,
JNU New Delhi, for providing microanalysis and spectra.
Keywords: Allan-Robinson reaction • Friedländer reaction •
NHC • Salicylaldehyde • Chromen-4-one • Quinolin-4-one
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10.1002/ejoc.201701435
European Journal of Organic Chemistry
FULL PAPER
FULL PAPER
NHC-Catalysis*
Vijai K. Rai,* [a] Fooleswar Verma,[a]
Ganeshwar P. Sahu,[a] Manorama
Singh[a] and Ankita Rai[b]
Page No. – Page No.
One-pot Allan-Robinson/Friedländer
route to Chromen-/Quinolin-4-one via
Domino Acetylative Cyclisation of 2-
Hydroxy-/2-Aminobenzaldehyde
This article is protected by copyright. All rights reserved.