Silver(i)/base-promoted propargyl alcohol-controlled regio- or stereoselective synthesis of furan-3-carboxamides and (Z)-enaminones

Article abstract of DOI:10.1039/C8OB01791C

A novel and facile regioselective synthesis of furan-3-carboxamides by a silver(i)/base-promoted reaction of propargyl alcohol with 3-oxo amides has been demonstrated. This one-pot protocol provides a rapid synthetic approach to diverse trisubstituted furan-3-carboxamides via cascade nucleophilic addition, intramolecular cyclization, elimination, and isomerization reactions. Employing a substituted propargyl alcohol, (Z)-enaminones have been obtained with high stereoselectivities by a Ag₂CO₃-promoted reaction starting from 3-oxo amides via C-N bond cleavage.

Full text of DOI:10.1039/C8OB01791C

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Silver(I)/base-promoted propargyl alcohol-
controlled regio- or stereoselective synthesis of
Cite this: DOI: 10.1039/c8ob01791c
furan-3-carboxamides and (Z)-enaminones†
a
Sabera Sultana, a Jae-Jin Shim, a Sung Hong Kim b and Yong Rok Lee
*
A novel and facile regioselective synthesis of furan-3-carboxamides by a silver(I)/base-promoted reaction
of propargyl alcohol with 3-oxo amides has been demonstrated. This one-pot protocol provides a rapid
synthetic approach to diverse trisubstituted furan-3-carboxamides via cascade nucleophilic addition,
intramolecular cyclization, elimination, and isomerization reactions. Employing a substituted propargyl
alcohol, (Z)-enaminones have been obtained with high stereoselectivities by a Ag2CO3-promoted
reaction starting from 3-oxo amides via C–N bond cleavage.
Received 25th July 2018,
Accepted 31st August 2018
DOI: 10.1039/c8ob01791c
rsc.li/obc
Among these, a typical method for furan-3-carboxamides
involves a 5-step procedure starting from β-keto esters (method
Introduction
Furans are one of the most important and versatile hetero- a, Scheme 1).10 Other useful approaches include AgNO3-
cycles found in natural products, pharmaceuticals, agrochem- mediated cycloisomerizations of N-propargylamide (method b,
icals, and functional materials.1 In addition, they have been Scheme 1)11 and PdCl2-catalyzed reactions of 3-alkyne-1,2-diols
widely used as valuable building blocks in organic synthesis.2 with isocyanate (method c, Scheme 1).12 Although a variety of
As a consequence, numerous methods for the synthesis of sub- methods for the synthesis of furan-3-carboxamides have been
stituted furans have been developed.3 However, synthetic developed, more facile and efficient synthetic strategies are
approaches to substituted furans bearing amide groups have still desirable.
been less explored so far. Furans bearing amide groups have
The regioselective reaction of silver salts with alkynes is an
been recognized as important subunits in many biologically important tool that has been widely used for the synthesis and
active molecules (Fig. 1).4 For example, proximicin A (I), iso- functionalization of the heterocycles.13 In particular, the use
lated from a marine actinomycete of the genus Verrucosispora,5 of combination of a silver salt with a base is a valuable
displays potent antitumor activities against several carcinoma method for the synthesis of many heterocycles, especially
cell lines.6 Compound II shows ∼1000-fold more potent trypa- those containing oxygen and nitrogen atoms.14 We have
nocidal activity than nifurtimox, which is currently used for previously reported the silver-promoted cycloaddition of
the treatment of human African trypanosomiasis.7 Compound 1,3-dicarbonyls with alkenes for the synthesis of dihydrofurans
III exhibits potent inhibitory activity against Schistosoma
mansoni NAD+ catabolizing enzyme (SmNACE),8 and
Compound IV is a potent inhibitor of lethal H5N1 influenza A
viruses.8 In addition, fenfuram (V), furcarbanil (VI), and
methfuroxam (VII) are well-known compounds belonging to
one of the most important class of agrochemical fungicides
for the control of most plant diseases in agriculture.9
Owing to their importance and usefulness, several synthetic
approaches for furan-carboxamides have been developed.
aSchool of Chemical Engineering, Yeungnam University, Gyeongsan 38541,
Republic of Korea. E-mail: yrlee@yu.ac.kr; Fax: +82-53-810-4631;
Tel: +82-53-810-2529
bAnalysis Research Division, Daegu Center, Korea Basic Science Institute,
Daegu 41566, Republic of Korea
†CCDC 1850643. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/c8ob01791c
Fig. 1 Biologically active compounds containing furan-carboxamides.
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Scheme 1 Reported synthetic methods for furan-3-carboxamides.
and furans.15 In addition in 2012, Lei’s group reported the
silver carbonate-mediated reaction of ketoester with phenyl-
acetylene to provide furan rings via β-ketoalkyne intermediate
(method a, Scheme 2).16 More commonly, furan rings have
been synthesized from the ketoester and propargyl alcohol via
the formation of γ-ketoalkyne intermediate in the presence of
metal catalysts e.g. Ru, Cu, Fe, Ag (AgSbF6), and Au (method b,
Scheme 2).17 In contrast to these common reports, this paper
describes silver/base-promoted regioselective synthesis of
furan-3-carboxamides via β-ketoalkene intermediate starting
from commercially available 3-oxo-N-alkylbutanamides or
3-oxo-N-arylbutanamides with propargyl alcohol (method c,
Scheme 2). Importantly, there was no any isolation of other
possible products via γ-ketoalkyne (method d, Scheme 2) or
β-ketoalkyne intermediate (method e, Scheme 2).
Scheme 3 Stereoselective synthetic strategies for (Z)-enaminones.
cally interesting heterocycles and aromatic compounds.18 Over
the past decade, a number of methods have been developed
for the preparation of (E)- and (Z)-enaminones.19 Typical
methods for (Z)-enaminones included the reaction of aniline
with β-ketoester in presence of metal catalyst Nb or Ni or metal
free condition by using IQGO (method a, Scheme 3),20 with
propargyl alcohol in presence of Ru catalyst (method b,
Scheme 3), or with but-3-yn-2-one under metal free condition
(method c, Scheme 3).21 However, despite the great advances
in (Z)-enaminones, herein we describe a new methodology
based on 3-oxo-N-arylbutanamides as a nitrogen source with
1-phenylprop-2-yn-1-ol in presence of silver carbonate (method
d, Scheme 3).
Enaminones show a versatile reactivity in organic synthesis
and are important building blocks for the synthesis of biologi-
Results and discussion
To optimize the reaction conditions, the Ag(I)-catalyzed reac-
tion of 3-oxo-N-phenylbutanamide (1a) with propargyl alcohol
(2a) was first examined under different silver salts and bases
in several solvents (Table 1). The initial attempt with Ag2CO3
(1 equiv.) in the presence of 2 equivalents of NaOAc in aceto-
nitrile at room temperature for 24 h gave no product (entry 1).
Increasing the temperature upto reflux condition provided the
product 3a in 67% yield (entry 2). Encouraged by this result,
further reaction in other solvents such as toluene, 1,2-dichloro-
ethane (DCE), DMF, and DMSO were screened. In toluene,
product 3a was formed in 40% yield (entry 3), whereas in other
solvents of 1,2-dichloroethane, DMF and DMSO, no products
were isolated (entries 4–6). Screening the reaction with other
silver salts such as AgOAc (1 equiv.), AgOTf (1 equiv.) and
AgNO3 (1 equiv.) in the presence of 2 equivalents of NaOAc in
acetonitrile at 80 °C for 12 h gave no products (entries 7–9).
With Ag2O (1 equiv.) and NaOAc (2 equiv.) in acetonitrile at
80 °C for 12 h, product 3a was produced in 25% yield (entry
10). In an attempt to increase the yield of 3a, other inorganic
and organic bases such as Cs2CO3, K2CO3, DBU, and TEA were
next screened. The reactions with 2 equivalents of Cs2CO3,
K2CO3, and DBU did not produce 3a (entries 11–13). Instead,
Scheme 2 Regioselective synthetic strategies for substituted furan-3-
carboxylates.
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Table 1 Optimization of the reaction conditions for the synthesis of 3a a
Yieldb (%)
Entry
Ag salt
Base
Additive
Solvent
Temp.
Time (h)
3a
3a′
1
2
3
4
5
6
7
8
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
AgOAc (1 eq.)
AgOTf (1 eq.)
AgNO3 (1 eq.)
Ag2O (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (1 eq.)
Ag2CO3 (0.5 eq.)
Ag2CO3 (2 eq.)
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
Cs2CO3
K2CO3
DBU
—
—
—
—
—
—
—
—
—
—
—
—
—
—
MS
MS
MS
CH3CN
CH3CN
Toluene
DCE
rt
24
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
0
67
40
0
0
0
0
0
0
0
25
0
0
71
77
52
75
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
80 °C
DMF
DMSO
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
9
10
11
12
13
14
15
16
17
TEA
TEA
TEA
a Reaction conditions: 1a (1.0 mmol), 2a (5.0 mmol) in the presence of silver salt and base (2.0 eq.) in 5 mL solvent. b Isolated yield.
the combination of Ag2CO3 with TEA provided 3a in 71% yield
(entry 14). Notably, a further improvement of the yield of 3a
(77%) was accomplished by the addition of molecular sieve
(4 Å) (entry 15). Decreasing (0.5 equiv.) or increasing (2.0
equiv.) the loading of Ag2CO3 did not improve the yield of 3a
(entries 16 and 17). Importantly, none of these conditions pro-
duced the product 3a′. The compounds 3a was isolated by
column chromatography and characterized by spectroscopic
1
analysis. The H NMR spectrum of 3a exhibits a broad singlet
at δ = 7.26 ppm characteristic of an –NH peak and a singlet at
δ = 7.08 ppm corresponding to the vinylic proton at C-5 of the
furan ring. The regiochemistry was confirmed by X-ray crystal
structure of 4a (Fig. 2). The different regiochemistry of this
protocol compared to Lei’s work might be due to the presence
of free-alcohol functional group.
Fig. 2 X-ray crystal structure of 4a.
With the optimized conditions in hand, the generality of
this reaction was further explored by reacting 2a with different
3-oxo-N-arylbutanamides 1b–1i bearing electron-donating and/ The reaction of N-methyl-3-oxobutanamide (1j) and N-benzyl-
or withdrawing groups (Table 2). For example, reaction of 1b, 3-oxobutanamide (1k) with 2a provided products 4a and 4b in
1c, 1d, 1e or 1f bearing electron-donating groups such as 4-Me, 78 and 75% yield respectively. The reaction of 1l and 1m
2-OMe, 4-OMe, 4-OEt, and 2,4-OMe on the benzene ring pro- bearing alkyl substituents such as ethyl, and i-propyl at C-3
vided products 3b–3f in 68–76% yields. Similarly, treatment of with 2a provided products 4c and 4d in 68 and 75% yield,
1g or 1h bearing electron-withdrawing group on the benzene respectively. Similarly, treatment of 1n bearing a long aliphatic
ring with 2a afforded 3g and 3h in 70 and 72% yield, respect- chain led to the corresponding product 4e in 74% yield. When
ively. Notably, 3-oxo-N-arylbutanamide 1i bearing both elec- 3-oxo-N,3-diphenylpropanamide (1o), 3-oxo-3-phenyl-N-(p-
tron-donating and -withdrawing groups on the aromatic ring tolyl)propanamide (1p) or 3-(4-methoxyphenyl)-3-oxo-N-phe-
was also transformed to the desired product 3i in 76% yield.
nylpropanamide (1q) were reacted with 2a, the corresponding
To demonstrate the versatility of this reaction, additional products 4f, 4g and 4h were isolated in 69, 75 and 77% yields,
reactions of β-oxo amides (1j–1r) bearing various substituents respectively. The reaction of N-(naphthalene-1-yl)-3-oxo-3-phe-
at C-3 and N-alkyl or aryl groups were next examined (Table 3). nylpropanamide (1r) with 2a afforded the product 4i in 68%
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Table 2 Formation of diverse furan-3-carboxamides 3b–3i by reaction
of 1b–1i with 2a
Table 3 Formation of diverse furan-3-carboxamides 4a–4j by reaction
of 1j–1r and 2a
yield. However, the treatment of 1a with 3-phenyl-2-propyn-1-ol
(2b) did not provide the desired furan product, instead, start-
ing materials were recovered. On the other hand, the use of
ethylacetoaceate instead of 1a did not provide any desired
product. In addition, reaction of 1a with propargyl amine did
not afford the desired product.
lysis and comparison of their spectral data with those of the
reported (Z)-and (E)-enaminones.18–21 In the 1H NMR of 5a,
the characteristic N–H proton peak at δ = 12.13 ppm is a broad
doublet (J = 10.8 Hz) due to the formation of a strong intra-
molecular hydrogen bond between the N–H proton and the
carbonyl oxygen in the (Z)-enaminone.
The versatility of this reaction for the synthesis of diverse
furan-3-carboxamides, prompted us to examine the reaction
with substituted propargyl alcohol, 1-phenylprop-2-yn-1-ol (2c).
Surprisingly, treatment of 1a with 2c in dry acetonitrile at
80 °C for 12 h provided unexpected product 5a in 57% yield.
Importantly, addition of a drop of water in dry acetonitrile, the
yield of 5a increased to 66%. With this optimized result, the
generalization of reaction was explored as shown in Table 4.
Reactions of 1b, 1s or 1d bearing electron-donating groups
4-Me, 4-i-Pr and 4-OMe respectively, on the N-phenyl ring
afforded 5b–5d in 65–68% yield; those of 1t, 1h, 1u, or 1v
bearing electron-withdrawing groups such as 3-Cl, 4-Cl, 3-Br
and 4-Br on the N-phenyl ring furnished 5e–5h in 64–67%
yields respectively. The reaction of N-(naphthalen-1-yl)-3-oxo-3-
phenylpropanamide (1r) led to the desired product 5i in 63%
yield. However, when aliphatic substituted propargyl alcohol
such as but-3-yn-2-ol was used instead of 2c, the desired (Z)-
enaminone was not produced. The (Z)-stereochemistry of the
synthesized compounds was confirmed by spectroscopic ana-
To elucidate the mechanism of the reaction, various control
experiments were performed (Scheme 4). The reaction of 1a
with silver acetylide 2a′ which was prepared from the reported
procedure,22 in basic conditions provided 3a in 64% yield (eqn
(1), Scheme 4). The formation of 2a′ was confirmed by IR spec-
troscopy through the absence of C–H stretching absorption at
3287 cm−1 for terminal alkyne proton of 2a (see ESI, Fig. S4 &
S5†). This result indicates that silver acetylide might be an
intermediate of the reaction. On the other hand, the treatment
of 1a with Ag2CO3/TEA in wet acetonitrile at 80 °C for 12 h pro-
vided aniline (1w), which was detected by GC/MS (see ESI,
Fig. S2 and S3†) (eqn (2), Scheme 4). In addition, the reaction
of aniline (1w) with 1-phenylprop-2-yn-1-ol (2c) in the presence
of Ag2CO3 (1.0 equiv.)/TEA (2.0 equiv.) in acetonitrile provided
5a in 80% yield (eqn (3), Scheme 4). Treatment of 1w with 2c
in the presence of Ag2CO3 (1.0 equiv.) without TEA provided 5a
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Table 4 Formation of diverse (Z)-enaminones 5a–5i by reaction of 1a–
1b, 1d, 1h, 1r, 1s–1v and 2c
Scheme 5 Plausible mechanism for regioselective formation of 3a.
Scheme 6 Plausible mechanism for stereoselective formation of 5a.
Ag2CO3. Under basic conditions, the nucleophilic addition of
enolate of 1a′ to 2a′ gives intermediate 6, which undergoes
proton exchange with B : H+ to furnish intermediate 7.
Subsequent intramolecular cyclization of intermediate 8 with
loss of water leads to the intermediate 9 followed by isomeriza-
tion to give the final product 3a.
The plausible reaction pathway for the stereoselective for-
mation of 5a is outlined in Scheme 6. The coordination of 1a
with Ag2CO3 gives 1a″ in which the carbonyl group undergoes
a subsequent nucleophilic attack by water to afford 1w. A
similar Cu(I)-mediated synthesis of aniline starting from
β-arylacetoacetamide has been previously described.23
Conjugated addition of 1w with 2c in the presence of Ag2CO3
finally provide the product 5a.
Scheme 4 Control experiments.
Conclusions
In conclusion, we have developed a silver carbonate-promoted
in 72% yield. However, when the reaction was carried out in one-pot protocol for the regioselective construction of diverse
presence of 2 equivalents of TEA without Ag2CO3, the desired furan-3-carboxamides starting from commercially available
product 5a was not isolated. Further reaction in the presence β-oxo amides and propargyl alcohol. This methodology pro-
of a catalytic amount of Ag2CO3 (20 mol%)/TEA (2.0 equiv.) vides a rapid synthetic route to various substituted furan-3-car-
provided 5a in lower yield (36%).
boxamides bearing N-aryl, N-alkyl, and N-polyaromatic substi-
Based on control experiments and observed products, a tuents. Moreover, a novel approach for the stereoselective
plausible mechanism that accounts for the regioselective syn- preparation of (Z)-enaminones has been accomplished by the
thesis of 3a is depicted in Scheme 5. Initially, silver acetylide Ag2CO3-promoted reaction of β-oxo amides and a substituted
2a′ is formed by the reaction of propargyl alcohol (2a) with propargyl alcohol through the C–N bond cleavage of amides.
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140–142 °C. Yield: 77% (166 mg). 1H NMR (600 MHz, CDCl3) δ
7.54 (2H, d, J = 7.8 Hz), 7.33 (2H, t, J = 7.8 Hz), 7.26 (1H, brs),
7.11 (1H, t, J = 7.2 Hz), 7.08 (1H, s), 2.53 (3H, s), 2.20 (3H, s);
Experimental
General remarks
All experiments were carried out in open air. Merck-precoated 13C NMR (150 MHz, CDCl3) δ 162.9, 156.1, 137.9, 137.8, 128.9,
TLC silica gel plates (Art. 5554) with a fluorescent indicator 124.2, 119.9, 118.4, 117.5, 13.7, 9.6; IR (ATR) 3293, 1642, 1504,
were used for TLC analysis. Column chromatography was per- 1413, 1228, 1109, 1046, 919, 810, 746 cm−1; HRMS m/z (M+)
formed using silica gel (Merck, Art. 9385). Melting points are calcd for C13H13NO2: 215.0946. Found: 215.0944.
uncorrected and were determined using micro-cover glasses
2,4-Dimethyl-N-(p-tolyl)furan-3-carboxamide (3b). The title
on a Fisher-Johns apparatus. 1H NMR spectra were recorded compound (3b) was prepared according to the general pro-
on a Varian-VNS (600 MHz) or Bruker (300 MHz) spectrometer, cedure. The product was obtained as a white solid, mp
1
and the residual solvent peak (δ = 7.24 ppm for CDCl3) or TMS 123–125 °C. Yield: 68% (156 mg). H NMR (600 MHz, CDCl3)
(δ = 0.00 ppm) was used as reference. 13C NMR spectra were δ 7.42 (2H, d, J = 8.4 Hz), 7.20 (1H, brs), 7.13 (2H, d, J =
recorded on a Varian-VNS (150 MHz) or Bruker (75 MHz) 7.8 Hz), 7.07 (1H, s), 2.52 (3H, s), 2.31 (3H, s), 2.19 (3H, s); 13C
spectrometer using the residual solvent peak (δ = 77.0 ppm for NMR (150 MHz, CDCl3) δ 162.8, 156.2, 137.9, 135.3, 133.9,
CDCl3) as reference. Chemical shifts (δ) are expressed in ppm 129.5, 120.1, 118.4, 117.5, 20.8, 13.8, 9.8; IR (ATR) 3296, 1642,
and J values are given in Hz. Multiplicities are abbreviated as 1503, 1411, 1230, 1107, 1036, 915, 811, 743 cm−1; HRMS m/z
follows; s = singlet, d = doublet, t = triplet, q = quartet, br s = (M+) calcd for C14H15NO2: 229.1103. Found: 229.1101.
broad singlet, dd = doublet of doublets, td = triplet of doub-
N-(2-Methoxyphenyl)-2,4-dimethylfuran-3-carboxamide (3c).
lets, quint = quintet, sept = septet, and m = multiplet. IR The title compound (3c) was prepared according to the general
spectra were recorded on a FTIR (BIO-RAD) spectrometer, and procedure. The product was obtained as a gummy liquid.
high-resolution mass spectra were obtained with a JEOL Yield: 72% (176 mg). 1H NMR (600 MHz, CDCl3) δ 8.48 (1H,
JMS-700 spectrometer at the Korea Basic Science Institute.
dd, J = 7.8, 1.2 Hz), 8.10 (1H, brs), 7.06 (1H, s), 7.01 (1H, td, J =
7.2, 1.8 Hz), 6.96 (1H, td, J = 7.8, 1.2 Hz), 6.86 (1H, dd, J = 7.8,
1.2 Hz), 3.86 (3H, s), 2.56 (3H, s), 2.23 (3H, s); 13C NMR
(150 MHz, CDCl3) δ 162.4, 156.9, 147.8, 137.9, 127.9, 123.4,
General procedure for the preparation of furan-3-carboxamides
(3a–3i & 4a–4i)
To a solution of β-oxo amides (1) (1.0 mmol) and propargyl 121.1, 119.5, 118.4, 117.5, 109.8, 55.7, 13.9, 9.8; IR (ATR) 3296,
alcohol (2a) (5.0 mmol, 5.0 equiv.) in dry acetonitrile (5 mL) 1642, 1508, 1415, 1230, 1102, 1046, 918, 812, 745 cm−1; HRMS
was added silver carbonate (1.0 mmol, 1 equiv.), triethylamine m/z (M+) calcd for C14H15NO3: 245.1052. Found: 245.1049.
(2.0 mmol, 2 equiv.), and molecular sieves 4 Å (1.0 g). The
N-(4-Methoxyphenyl)-2,4-dimethylfuran-3-carboxamide (3d).
resulting mixture was stirred under a N2 atmosphere at 80 °C The title compound (3d) was prepared according to the general
for 12 h. The progress of the reaction was monitored by TLC procedure. The product was obtained as a white solid, mp
1
with ethyl acetate and hexane (EtOAc/hexane 1 : 4) as eluents. 153–154 °C. Yield: 75% (184 mg). H NMR (600 MHz, CDCl3)
After completion, the reaction mixture was filtered through a δ 7.43 (2H, d, J = 9.0 Hz), 7.28 (1H, s), 7.04 (1H, s), 6.84 (2H, d,
plug of silica gel (Et2O was used as eluent). The solvent was J = 9.0 Hz), 3.77 (3H, s), 2.48 (3H, s), 2.16 (3H, s); 13C NMR
removed in vacuo and the resulting crude material was sub- (150 MHz, CDCl3) δ 162.8, 156.5, 156.1, 137.9, 130.9, 121.9,
jected to silica gel chromatography to give the desired products 118.4, 117.4, 114.1, 55.5, 13.8, 9.8; IR (ATR) 3299, 1646, 1506,
(3a–3i & 4a–4i).
1415, 1231, 1106, 1041, 917, 812, 745 cm−1; HRMS m/z (M+)
calcd for C14H15NO3: 245.1052. Found: 245.1049.
N-(4-Ethoxyphenyl)-2,4-dimethylfuran-3-carboxamide (3e).
The title compound (3e) was prepared according to the general
General procedure for the preparation of (Z)-enaminones
(5a–5i)
To a solution of β-oxo amides (1) (1.0 mmol) and 1-phenyl- procedure. The product was obtained as a white solid, mp
1
prop-2-yn-1-ol (2c) (1.0 mmol) in a drop of water and aceto- 150–154 °C. Yield: 75% (194 mg). H NMR (600 MHz, CDCl3)
nitrile (5 mL) was added silver carbonate (1.0 mmol, 1 equiv.) δ 7.42 (2H, d, J = 8.4 Hz), 7.16 (1H, brs), 7.06 (1H, s), 6.86 (2H,
and triethylamine (2 equiv.). The resulting mixture was stirred d, J = 8.4 Hz), 4.01 (2H, q, J = 7.2 Hz), 2.51 (3H, s), 2.19 (3H, s),
at 80 °C for 12 h. The progress of the reaction was monitored 1.38 (3H, t, J = 7.2 Hz); 13C NMR (150 MHz, CDCl3) δ 162.7,
by TLC with ethyl acetate and hexane (EtOAc/hexane 1 : 9) as 156.3, 155.9, 138.0, 130.7, 121.9, 118.3, 117.4, 114.8, 63.7, 14.8,
eluents. After completion, the reaction mixture was filtered 13.9, 9.9; IR (ATR) 3298, 1640, 1502, 1411, 1236, 1108, 1040,
through a plug of silica gel (Et2O was used as eluent). The 912, 816, 742 cm−1; HRMS m/z (M+) calcd for C15H17NO3:
solvent was removed in vacuo and the resulting crude material 259.1208. Found: 259.1207.
was subjected to silica gel chromatography to give the desired
products (5a–5i) as yellow solids.
N-(2,4-Dimethoxyphenyl)-2,4-dimethylfuran-3-carboxamide
(3f). The title compound (3f) was prepared according to the
general procedure. The product was obtained as a white solid,
Characterization data of synthesized compounds
1
mp 161 °C. Yield: 76% (209 mg). H NMR (600 MHz, CDCl3)
2,4-Dimethyl-N-phenylfuran-3-carboxamide (3a). The title δ 8.34 (1H, d, J = 9.6 Hz), 7.86 (1H, brs), 7.05 (1H, s), 6.48–6.47
compound (3a) was prepared according to the general pro- (2H, m), 3.84 (3H, s), 3.78 (3H, s), 2.52 (3H, s), 2.21 (3H, s);
cedure. The product was obtained as a white solid, mp 13C NMR (150 MHz, CDCl3) δ 162.4, 156.6, 156.2, 149.2, 137.9,
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121.5, 120.5, 118.5, 117.6, 103.8, 98.6, 55.8, 55.5, 13.9, 9.8; IR cedure. The product was obtained as a white solid, mp
(ATR) 3296, 1641, 1502, 1413, 1234, 1105, 1046, 917, 818, 149–151 °C. Yield: 75% (165 mg). 1H NMR (600 MHz, CDCl3) δ
749 cm−1; HRMS m/z (M+) calcd for C15H17NO4: 275.1158. 7.34–7.30 (4H, m), 7.28–7.25 (1H, m), 7.01 (1H, s), 5.85 (1H,
Found: 275.1159.
brs), 4.58 (2H, d, J = 10.8 Hz), 2.47 (3H, s), 2.09 (3H, s); 13C
N-(2-Chlorophenyl)-2,4-dimethylfuran-3-carboxamide (3g). NMR (150 MHz, CDCl3) δ 164.6, 156.0, 138.4, 137.8, 128.8,
The title compound (3g) was prepared according to the general 127.7, 127.5, 118.4, 116.8, 43.5, 13.8, 9.9; IR (ATR) 3023, 1646,
procedure. The product was obtained as a white solid, mp 1583, 1447, 1401, 1305, 1242, 1209, 1016, 977, 786 cm−1
;
160–162 °C. Yield: 70% (174 mg). 1H NMR (600 MHz, CDCl3) δ HRMS m/z (M+) calcd for C14H15NO2: 229.1103. Found:
8.54 (1H, d, J = 8.4 Hz), 7.92 (1H, brs), 7.37 (1H, d, J = 7.8 Hz), 229.1104.
7.28 (1H, t, J = 7.8 Hz), 7.08 (1H, s), 7.02 (1H, t, J = 7.2 Hz),
2-Ethyl-4-methyl-N-phenylfuran-3-carboxamide (4c). The title
2.58 (3H, s), 2.27 (3H, s); 13C NMR (150 MHz, CDCl3) δ 162.6, compound (4c) was prepared according to the general pro-
157.7, 138.1, 134.9, 128.9, 127.8, 124.3, 122.4, 121.4, 118.3, cedure. The product was obtained as a white solid, mp
117.1, 14.2, 10.2; IR (ATR) 3299, 1648, 1507, 1416, 1235, 1104, 112–115 °C. Yield: 68% (155 mg). 1H NMR (600 MHz, CDCl3) δ
1043, 912, 811, 740 cm−1
;
HRMS m/z (M+) calcd for 7.54 (2H, d, J = 8.4 Hz), 7.33 (2H, t, J = 7.8 Hz), 7.29 (1H, brs),
7.11 (1H, t, J = 7.2 Hz), 7.08 (1H, s), 2.92 (2H, q, J = 7.8 Hz),
C13H12ClNO2: 249.0557. Found: 249.0558.
N-(4-Chlorophenyl)-2,4-dimethylfuran-3-carboxamide (3h). 2.19 (3H, s), 1.25 (3H, t, J = 7.8 Hz); 13C NMR (150 MHz,
The title compound (3h) was prepared according to the CDCl3) δ 162.8, 161.2, 138.2, 137.9, 129.1, 124.4, 119.9, 118.2,
general procedure. The product was obtained as a white solid, 116.7, 21.3, 12.4, 9.8; IR (ATR) 3298, 1645, 1514, 1412, 1229,
mp 163–165 °C. Yield: 72% (179 mg). 1H NMR (600 MHz, 1129, 1046, 910, 811, 746 cm−1; HRMS m/z (M+) calcd for
CDCl3) δ 7.49 (2H, d, J = 8.4 Hz), 7.30 (1H, brs), 7.28 (2H, d, J = C14H15NO2: 229.1103. Found: 229.1104.
9.0 Hz), 7.07 (1H, d, J = 1.2 Hz), 2.51 (3H, s), 2.18 (3H, s); 13C
2-Isopropyl-4-methyl-N-phenylfuran-3-carboxamide (4d). The
NMR (150 MHz, CDCl3) δ 162.8, 156.8, 138.2, 136.4, 129.3, title compound (4d) was prepared according to the general pro-
129.1, 121.2, 118.1, 117.2, 13.9, 9.9; IR (ATR) 3298, 1649, 1507, cedure. The product was obtained as a gummy liquid. Yield:
1413, 1230, 1104, 1049, 912, 816, 742 cm−1; HRMS m/z (M+) 75% (182 mg). 1H NMR (600 MHz, CDCl3) δ 7.55 (2H, d, J = 8.4
calcd for C13H12ClNO2: 249.0557. Found: 249.0560.
Hz), 7.34 (1H, brs), 7.32 (2H, t, J = 7.8 Hz), 7.10 (1H, t, J = 7.8
N-(4-Chloro-2,5-dimethoxyphenyl)-2,4-dimethylfuran-3-car- Hz), 7.08 (1H, d, J = 1.2 Hz), 3.55 (1H, sept, J = 6.6 Hz), 2.17
boxamide (3i). The title compound (3i) was prepared according (3H, s), 1.26 (6H, d, J = 7.2 Hz); 13C NMR (150 MHz, CDCl3)
to the general procedure. The product was obtained as a white δ 164.1, 162.9, 137.9, 137.8, 129.0, 124.3, 119.9, 117.9, 115.8,
solid, mp 155–156 °C. Yield: 76% (235 mg). 1H NMR 27.3, 20.9, 9.7; IR (ATR) 3292, 1606, 1500, 1411, 1228, 1109,
(600 MHz, CDCl3) δ 8.34 (1H, s), 8.07 (1H, brs), 7.06 (1H, s), 1039, 918, 812, 740 cm−1; HRMS m/z (M+) calcd for C15H17NO2:
6.88 (1H, s), 3.89 (3H, s), 3.83 (3H, s), 2.55 (3H, s), 2.22 (3H, s); 243.1259. Found: 243.1256.
13C NMR (150 MHz, CDCl3) δ 162.5, 157.3, 149.2, 141.8, 138.1,
4-Methyl-N-phenyl-2-undecylfuran-3-carboxamide (4e). The
127.3, 118.2, 117.2, 115.3, 112.2, 104.7, 56.7, 56.5, 14.0, 9.9; IR title compound (4e) was prepared according to the general pro-
(ATR) 3292, 1642, 1509, 1411, 1238, 1103, 1040, 916, 819, cedure. The product was obtained as a gummy liquid. Yield:
748 cm−1; HRMS m/z (M+) calcd for C15H16ClNO4: 309.0768. 74% (241 mg). 1H NMR (600 MHz, CDCl3) δ 7.54 (2H, d, J =
Found: 309.0764.
7.8 Hz), 7.38 (1H, brs), 7.32 (2H, td, J = 7.2, 7.2 Hz), 7.11–7.08
N,2,4-Trimethylfuran-3-carboxamide (4a). The title com- (1H, m), 7.07 (1H, d, J = 1.8 Hz), 2.87 (2H, t, J = 7.8 Hz), 2.17
pound (4a) was prepared according to the general procedure. (3H, s), 1.66 (2H, quint, J = 7.8 Hz), 1.33–1.23 (12H, m), 0.85
The product was obtained as white crystals, mp 130–133 °C. (3H, t, J = 6.6 Hz); 13C NMR (150 MHz, CDCl3) δ 162.8, 160.1,
Yield: 78% (119 mg). 1H NMR (600 MHz, CDCl3) δ 6.97 (1H, s), 138.1, 137.9, 128.9, 124.3, 119.9, 118.2, 117.3, 31.8, 29.9, 29.3,
5.74 (1H, brs), 2.88 (3H, d, J = 4.8 Hz), 2.41 (3H, s), 2.06 (3H, 29.25, 29.21, 28.1, 22.6, 14.0, 9.7; IR (ATR) 3285, 1646, 1515,
s); 13C NMR (150 MHz, CDCl3) δ 165.5, 155.4, 137.7, 118.4, 1435, 1305, 1243, 1063, 916, 877, 751 cm−1; HRMS m/z (M+)
117.0, 26.2, 13.6, 9.7; IR (ATR) 3285, 1645, 1518, 1433, 1203, calcd for C21H29NO2: 327.2198. Found: 327.2197.
1142, 1072, 917, 826, 758 cm−1; HRMS m/z (M+) calcd for
C8H11NO2: 153.0790. Found: 153.0788.
4-Methyl-N,2-diphenylfuran-3-carboxamide (4f). The title
compound (4f) was prepared according to the general pro-
cedure. The product was obtained as a white solid, mp
130–132 °C. Yield: 69% (191 mg). 1H NMR (600 MHz, CDCl3) δ
X-Ray crystallographic data of compound 4a
Empirical formula – C8H11NO2, M = 153.18, space group P21, a 7.66 (2H, d, J = 7.2 Hz), 7.41–7.38 (4H, m), 7.36–7.34 (2H, m),
= 5.0234(15) Å, b = 12.137(4) Å, c = 13.751(4) Å, V = 826.2(4) Å3, 7.29 (2H, t, J = 7.8 Hz), 7.25 (1H, s), 7.09 (1H, t, J = 7.2 Hz),
Z = 4, T = 296 K, ρcalcd = 1.232 g cm−3, 2Θmax. = 25.048°, refine- 2.19 (3H, s); 13C NMR (150 MHz, CDCl3) δ 162.7, 152.5, 139.3,
ment of 213 parameters on 2772 independent reflections with 137.7, 129.7, 129.0, 128.9, 127.1, 124.4, 122.1, 119.7, 118.6, 8.9;
wR2 = 0.1007 and S = 1.011. The crystal structure has been de- IR (ATR) 3285, 1646, 1515, 1435, 1305, 1243, 1063, 877,
posited at the Cambridge Crystallographic Data Centre (CCDC 751 cm−1; HRMS m/z (M+) calcd for C18H15NO2: 277.1103;
1850643†).
found: 277.1100.
N-Benzyl-2,4-dimethylfuran-3-carboxamide (4b). The title
4-Methyl-2-phenyl-N-(p-tolyl)furan-3-carboxamide (4g). The
compound (4b) was prepared according to the general pro- title compound (4g) was prepared according to the general
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procedure. The product was obtained as a white solid, mp procedure. The product was obtained as a yellow solid, mp
1
133–134 °C. Yield: 75% (218 mg). H NMR (300 MHz, CDCl3) δ 132–133 °C. Yield: 68% (180 mg). 1H NMR (600 MHz, CDCl3) δ
7.65 (2H, dd, J = 8.1, 1.5 Hz), 7.42–7.31 (6H, m), 7.24 (1H, s), 12.14 (1H, d, J = 11.4 Hz), 7.92 (2H, d, J = 7.2 Hz), 7.50–7.46
7.09 (2H, d, J = 8.4 Hz), 2.29 (3H, s), 2.18 (3H, s); 13C NMR (2H, m), 7.43 (2H, t, J = 7.2 Hz), 7.19 (2H, d, J = 8.4 Hz), 7.03
(75 MHz, CDCl3) δ 162.6, 152.3, 139.3, 135.1, 134.1, 129.7, (2H, d, J = 7.8 Hz), 5.98 (1H, d, J = 7.8 Hz), 2.87 (1H, sept, J =
129.5, 128.9, 128.8, 127.0, 122.1, 119.7, 118.7, 20.9, 8.9; IR (ATR) 6.6 Hz), 1.23 (6H, d, J = 7.2 Hz); 13C NMR (150 MHz, CDCl3) δ
3287, 1647, 1514, 1432, 1325, 1245, 1163, 875, 756 cm−1; HRMS 190.7, 145.3, 144.6, 139.3, 138.0, 131.4, 128.4, 127.6, 127.2,
m/z (M+) calcd for C19H17NO2: 291.1259. Found: 291.1258.
116.4, 93.2, 33.5, 23.9; IR (ATR) 3237, 2923, 1639, 1606, 1545,
2-(4-Methoxyphenyl)-4-methyl-N-phenylfuran-3-carboxamide 1471, 1260, 1023, 961, 815, 735 cm−1; HRMS m/z (M+) calcd for
(4h). The title compound (4h) was prepared according to the C18H19NO: 265.1467. Found: 265.1464.
general procedure. The product was obtained as a white solid,
(Z)-3-((4-Methoxyphenyl)amino)-1-phenylprop-2-en-1-one (5d).
mp 155–156 °C. Yield: 77% (236 mg). 1H NMR (600 MHz, The title compound (5d) was prepared according to the general
CDCl3) δ 7.59 (2H, d, J = 9.0 Hz), 7.41 (2H, d, J = 7.8 Hz), 7.35 procedure. The product was obtained as a yellow solid, mp
(1H, brs), 7.28 (2H, t, J = 7.8 Hz), 7.21 (1H, s), 7.08 (1H, t, J = 135–136 °C. Yield: 67% (169 mg). 1H NMR (600 MHz, CDCl3) δ
7.2 Hz), 6.92 (2H, d, J = 9.0 Hz), 3.81 (3H, s), 2.19 (3H, s); 12.17 (1H, d, J = 12.6 Hz), 7.91 (2H, d, J = 7.2 Hz), 7.48–7.46
13C NMR (150 MHz, CDCl3) δ 162.8, 160.2, 152.9, 138.8, 137.8, (1H, m), 7.45–7.39 (3H, m), 7.03 (2H, d, J = 8.4 Hz), 6.88 (2H,
129.0, 128.9, 124.3, 122.3, 122.0, 119.6, 117.3, 114.3, 55.3, 9.1; d, J = 7.2 Hz), 5.95 (1H, d, J = 7.8 Hz), 3.78 (3H, s); 13C NMR
IR (ATR) 3287, 1642, 1545, 1430, 1315, 1240, 1163, 878, (150 MHz, CDCl3) δ 190.6, 156.4, 145.9, 139.3, 133.8, 131.3,
756 cm−1; HRMS m/z (M+) calcd for C19H17NO3: 307.1208. 128.4, 127.2, 117.9, 114.9, 92.8, 55.5; IR (ATR) 2923, 1621,
Found: 307.1205.
4-Methyl-N-(naphthalen-1-yl)-2-phenylfuran-3-carboxamide (4i). calcd for C16H15NO2: 253.1103. Found: 253.1103.
The title compound (4i) was prepared according to the general (Z)-3-((3-Chlorophenyl)amino)-1-phenylprop-2-en-1-one (5e).
1509, 1469, 1283, 1227, 1023, 815, 735 cm−1; HRMS m/z (M+)
procedure. The product was obtained as a white solid, mp The title compound (5e) was prepared according to the general
130–133 °C. Yield: 68% (222 mg). 1H NMR (600 MHz, CDCl3) δ procedure. The product was obtained as a yellow solid, mp
8.74 (1H, s), 7.84 (1H, d, J = 6.6 Hz), 7.71 (1H, d, J = 7.8 Hz), 135–136 °C. Yield: 64% (164 mg). 1H NMR (600 MHz, CDCl3) δ
7.55 (1H, d, J = 8.4 Hz), 7.47 (2H, d, J = 7.2 Hz), 7.36–7.24 (7H, 12.07 (1H, d, J = 11.4 Hz), 7.91 (2H, d, J = 7.8 Hz), 7.50–7.48
m), 7.19–7.17 (1H, m), 2.16 (3H, s); 13C NMR (150 MHz, CDCl3) (1H, m), 7.45–7.42 (3H, m), 7.24 (1H, t, J = 7.8 Hz), 7.09–7.08
δ 171.2, 159.6., 149.7, 136.6, 135.7, 133.9, 130.9, 130.2, 129.1, (1H, m), 7.02 (1H, dd, J = 7.8, 1.8 Hz), 6.95 (1H, dd, J = 7.2, 1.8
128.7, 126.5, 126.4, 126.3, 126.1, 125.7, 125.5, 120.2, 120.0, Hz), 6.04 (1H, d, J = 7.8 Hz); 13C NMR (150 MHz, CDCl3) δ
104.6, 10.3; IR (ATR) 3285, 1648, 1518, 1436, 1304, 1242, 1073, 191.4, 144.1, 141.5, 138.9, 135.6, 131.8, 130.8, 128.5, 127.4,
917, 870, 758 cm−1; HRMS m/z (M+) calcd for C22H17NO2: 123.5, 116.1, 114.6, 94.6; IR (ATR) 3249, 1644, 1531, 1455,
327.1259. Found: 327.1257.
(Z)-1-Phenyl-3-(phenylamino)prop-2-en-1-one (5a). The title C15H12ClNO: 257.0607. Found: 257.0605.
1250, 1032, 971, 811, 755 cm−1; HRMS m/z (M+) calcd for
compound (5a) was prepared according to the general pro-
(Z)-3-((4-Chlorophenyl)amino)-1-phenylprop-2-en-1-one (5f).
cedure. The product was obtained as a yellow solid, mp The title compound (5f) was prepared according to the general
1
130–132 °C. Yield: 66% (147 mg). H NMR (600 MHz, CDCl3) procedure. The product was obtained as a yellow solid, mp
δ 12.13 (1H, d, J = 10.8 Hz), 7.92 (2H, d, J = 7.8 Hz), 7.53–7.47 162–163 °C. Yield: 66% (169 mg). 1H NMR (600 MHz, CDCl3) δ
(2H, m), 7.45–7.42 (2H, m), 7.33 (2H, t, J = 7.8 Hz), 7.09 (2H, d, 12.11 (1H, d, J = 12.0 Hz), 7.91 (2H, d, J = 7.2 Hz), 7.50–7.47
J = 8.4 Hz), 7.06 (1H, t, J = 7.2 Hz), 6.01 (1H, d, J = 7.8 Hz); 13C (1H, m), 7.44–7.39 (3H, m), 7.27 (2H, d, J = 9.0 Hz), 7.00 (2H,
NMR (150 MHz, CDCl3) δ 191.0, 144.9, 140.2, 139.2, 131.6, d, J = 9.0 Hz), 6.02 (1H, d, J = 7.8 Hz); 13C NMR (150 MHz,
129.7, 128.4, 127.3, 123.7, 116.3, 93.7; IR (ATR) 3237, 3057, CDCl3) δ 191.2, 144.5, 138.9, 138.8, 131.7, 129.7, 128.6, 128.4,
2997, 1657, 1602, 1545, 1471, 1260, 961 cm−1; HRMS m/z (M+) 127.3, 117.4, 94.2; IR (ATR) 3250, 1640, 1504, 1448, 1235, 1016,
calcd for C15H13NO: 223.0997. Found: 223.0996.
(Z)-1-Phenyl-3-(p-tolylamino)prop-2-en-1-one (5b). The title 257.0607. Found: 257.0604.
970, 811, 756 cm−1; HRMS m/z (M+) calcd for C15H12ClNO:
compound (5b) was prepared according to the general pro-
(Z)-3-((3-Bromophenyl)amino)-1-phenylprop-2-en-1-one (5g).
cedure. The product was obtained as a yellow solid, mp The title compound (5g) was prepared according to the general
1
120–122 °C. Yield: 65% (154 mg). H NMR (600 MHz, CDCl3) procedure. The product was obtained as a yellow solid, mp
δ 12.13 (1H, d, J = 12.0 Hz), 7.92 (2H, d, J = 7.2 Hz), 7.49–7.41 162–164 °C. Yield: 63% (189 mg). 1H NMR (600 MHz, CDCl3) δ
(4H, m), 7.13 (2H, d, J = 7.8 Hz), 6.99 (2H, d, J = 7.8 Hz), 5.98 12.07 (1H, d, J = 12.0 Hz), 7.90 (2H, dd, J = 7.8, 1.8 Hz),
(1H, d, J = 7.8 Hz), 2.30 (3H, s); 13C NMR (150 MHz, CDCl3) 7.50–7.48 (1H, m), 7.45–7.42 (3H, m), 7.25 (1H, s), 7.19–7.16
δ 190.8, 145.3, 139.3, 137.8, 133.4, 131.4, 130.2, 128.4, 127.2, (2H, m), 7.00–6.98 (1H, m), 6.04 (1H, d, J = 7.8 Hz); 13C NMR
116.4, 93.2, 20.7; IR (ATR) 3235, 3050, 2990, 1648, 1600, 1540, (150 MHz, CDCl3)
δ 191.4, 144.1, 141.7, 138.9, 131.8,
1473, 1258, 961, 816, 759 cm−1; HRMS m/z (M+) calcd for 131.0, 128.5, 127.4, 126.4, 123.5, 119.0, 115.1 94.6; IR
C16H15NO: 237.1154. Found: 237.1151.
(ATR) 3256, 1640, 1538, 1457, 1252, 1033, 970, 808, 762 cm−1
;
(Z)-3-((4-Isopropylphenyl)amino)-1-phenylprop-2-en-1-one (5c). HRMS m/z (M+) calcd for C15H12BrNO: 301.0102. Found:
The title compound (5c) was prepared according to the general 301.0099.
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(Z)-3-((4-Bromophenyl)amino)-1-phenylprop-2-en-1-one (5h).
The title compound (5h) was prepared according to the
general procedure. The product was obtained as a yellow solid,
mp 172–173 °C. Yield: 67% (201 mg). 1H NMR (600 MHz,
CDCl3) δ 12.10 (1H, d, J = 10.8 Hz), 7.90 (2H, d, J = 8.4 Hz),
7.50–7.47 (1H, m), 7.44–7.39 (5H, m), 6.95 (2H, d, J = 7.8 Hz),
6.02 (1H, d, J = 7.8 Hz); 13C NMR (150 MHz, CDCl3) δ 191.2,
144.3, 139.3, 138.9, 132.6, 131.7, 128.4, 127.3, 117.7, 116.1,
94.3; IR (ATR) 3258, 1648, 1534, 1458, 1255, 1036, 972, 811,
758 cm−1; HRMS m/z (M+) calcd for C15H12BrNO: 301.0102.
Found: 301.0099.
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(Z)-3-(Naphthalen-1-ylamino)-1-phenylprop-2-en-1-one (5i).
The title compound (5i) was prepared according to the general
procedure. The product was obtained as a yellow solid, mp
1
130–133 °C. Yield: 63% (171 mg). H NMR (600 MHz, CDCl3)
δ 13.06 (1H, d, J = 11.4 Hz), 8.24 (1H, d, J = 8.4 Hz), 7.99 (2H,
d, J = 8.4 Hz), 7.85 (1H, d, J = 7.8 Hz), 7.71–7.67 (1H, m),
7.62–7.59 (2H, m), 7.53 (1H, t, J = 7.2 Hz), 7.50 (1H, d, J =
6.6 Hz), 7.47–7.42 (3H, m), 7.26 (1H, d, J = 7.2 Hz), 6.14 (1H, d,
J = 7.8 Hz); 13C NMR (150 MHz, CDCl3) δ 191.4, 146.1, 139.2,
136.4, 134.3, 131.6, 128.4, 127.4, 126.7, 126.6, 125.8, 124.8,
124.1, 121.0, 110.9, 94.7; IR (ATR) 3248, 1641, 1564, 1468,
1305, 1225, 1026, 971, 811, 767 cm−1; HRMS m/z (M+) calcd for
C19H15NO: 273.1154. Found: 273.1153.
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There are no conflicts to declare.
Acknowledgements
This work was supported by the National Research Foundation
of Korea (NRF) grant funded by the Korea government (MSIT)
(2018R1A2B2004432) and the Priority Research Centers
Program (2014R1A6A1031189). This research was supported by
the Nano Material Technology Development Program of the
Korean National Research Foundation (NRF) funded by the
Korean Ministry of Education, Science, and Technology
(2012M3A7B4049675).
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