One-pot, three-component coupling reaction: Catalyst-free green synthesis of novel N-heteroaryl -naphthylglycines

Article abstract of DOI:10.1080/00397910903457407

A series of novel N-heteroaryl -arylglycines containing naphthol rings has been prepared by one-pot, three-component condensation reaction of glyoxalic acid, heteroaryl amines and naphthols in water at ambient temperature and under reflux conditions in moderate to high yields. The promising advantages such as removal of organic solvent, no need to catalyst, simplicity of the reaction procedure and easy product separation will be discussed in this article. Copyright

Full text of DOI:10.1080/00397910903457407

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One-Pot, Three-Component Coupling
Reaction: Catalyst-Free Green
Synthesis of Novel N-Heteroaryl α-
Naphthylglycines
Abolfazl Olyaei a , Esmat Chehrehgosha Parashkuhi a , Saeed
Raoufmoghaddam b & Mahdieh Sadeghpour c
a Department of Chemistry, Payame Noor University (PNU), Qazvin,
Iran
b School of Chemistry, University College of Science, University of
Tehran, Tehran, Iran
c Department of Chemistry, Islamic Azad University, Takestan
Branch, Qazvin, Iran
Published online: 09 Nov 2010.
To cite this article: Abolfazl Olyaei , Esmat Chehrehgosha Parashkuhi , Saeed Raoufmoghaddam &
Mahdieh Sadeghpour (2010): One-Pot, Three-Component Coupling Reaction: Catalyst-Free Green
Synthesis of Novel N-Heteroaryl α-Naphthylglycines, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 40:24, 3609-3617
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Synthetic Communications1, 40: 3609–3617, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903457407
ONE-POT, THREE-COMPONENT COUPLING
REACTION: CATALYST-FREE GREEN SYNTHESIS OF
NOVEL N-HETEROARYL a-NAPHTHYLGLYCINES
Abolfazl Olyaei,1 Esmat Chehrehgosha Parashkuhi,1
Saeed Raoufmoghaddam,2 and Mahdieh Sadeghpour3
1Department of Chemistry, Payame Noor University (PNU), Qazvin, Iran
2School of Chemistry, University College of Science, University of Tehran,
Tehran, Iran
3Department of Chemistry, Islamic Azad University, Takestan Branch,
Qazvin, Iran
A series of novel N-heteroaryl a-arylglycines containing naphthol rings has been prepared
by one-pot, three-component condensation reaction of glyoxalic acid, heteroaryl amines and
naphthols in water at ambient temperature and under reflux conditions in moderate to high
yields. The promising advantages such as removal of organic solvent, no need to catalyst,
simplicity of the reaction procedure and easy product separation will be discussed in this
article.
Keywords: Glyoxalic acid; heteroaryl amines; naphthols; a-naphthylglycines
INTRODUCTION
Amino acids are among the most important and indispensable materials for the
maintenance of human life.[1] In drug discovery, interest in non-proteinogenic
[2]
a-amino acids is continuously increasing as a result of their potential pharmaco-
logical properties and their utility as building blocks in the synthesis of biologically
active substances and naturally occurring compounds, such as vancomycin and
nocardicin.[3,4]
Several practical approaches to construct amino acid frameworks and their
derivatives have been developed by organic=medicinal chemists.[5] Friedel–Crafts
type reactions of electron-rich arenes with a glycine cation equivalent are among
the most useful tools in achievement of the facile preparation of these a-aromatic
amino acid derivatives. However, most of the electrophilic sources employed in
the Friedel–Crafts reaction have been limited to imines or imino esters.[6–9] Heaney
and co-workers developed an effective preparation of a-aryl-amino acid derivatives
using an N,O-acetal, in the presence of a typical silyl chloride, such as Me3SiCl;
Received September 7, 2009.
Address correspondence to Professor Abolfazl Olyaei, Department of Chemistry, University of
Payame Noor, Qazvin, Iran. E-mail: olyaei_a@pnu.ac.ir
3609

3610
A. OLYAEI ET AL.
Figure 1. Examples of the synthesized a-arylglycines.
however, most of the reactions required long reaction times to complete.[10] Risch
and coworkers[11] demonstrated the aminoalkylation of arenes with benzotriazolyl-
substituted N,N-aminals in the presence of stoichiometric amounts of AlCl3 and
TiCl4, leading to the formation of a-aryl-a-amino acid esters.
The Petasis reaction, or boronic Mannich reaction, involves the three-
component coupling of an amine, an aldehyde and an organoboron compound.
One of the most important uses of the Petasis reaction is the synthesis of arylglycines
employing glyoxylic acid as the aldehyde component and an arylboronic acid as the
organoboron derivative.[12–14] This reaction is ideally suited for combinatorial chem-
istry.[15] In general, this reaction is more efficient with secondary amines and steri-
cally hindered primary amines.[16,17] Examples of the synthesized a-arylglycine
derivatives are shown in Fig. 1.[18–20]
To the best of our knowledge, synthesis of N-heteroaryl-2-(2-hydroxynaphthalen-
1-yl)glycines and N-heteroaryl-2-(2,7-dihydroxynaphthalen-1-yl)glycines via conden-
sation of heteroarylamines, glyoxalic acid and naphthols has not previously been
reported in literature. As part of a continuous effort to develop new a-arylglycine
derivatives, we report here a convenient one-step synthesis of novel N-heteroaryl
a-naphthylglycines in water at ambient temperature and under reflux conditions.
RESULTS AND DISCUSSION
We have previously reported a one-pot three-component uncatalyzed quanti-
tative synthesis of new aminonaphthols (Betti bases).[21] One of the benefits of this
system is that the reaction proceeded well at room temperature without the require-
ment of any catalyst in water. Therefore, in this article our synthetic approach is
based on the Betti reaction employing glyoxalic acid as the aldehyde component.
In the beginning, a systematic study was carried out for the synthesis of
a-naphthylglycines in water as solvent in the absence of acid catalyst under two
coditions: at room temperature and under reflux conditions. Initially, the reaction
was conducted using b-naphthol, glyoxalic acid and 2-aminopyrimidine at room
temperature, which resulted the desired product 88% yield after 14 h (monitored
by a thin-layer chromatography, TLC). With the same substrates, the reaction under
reflux conditions, afforded the same product in 80% yield after 2.5 h. Therefore, we
decided to examine the other reactions under two conditions and investigated the
effects of temperature on the reaction times and yields of products.

GREEN SYNTHESIS OF N-HETEROARYL a-NAPHTHYLGLYCINES
3611
Table 1. Synthesis of N-heteroaryl a-naphthylglycines in water
Method A
Entry
Amine
Product
4
Time=h
Yield (%)
Mp (ꢀC)
184–185
1
4a
14
88
2
3
4
5
6
7
4b
4c
4d
4e
4f
3.5
17
4.5
20
5
85
78
89
85
90
83
196–198
176–178
179–180
170–171
159–161
4g
8
200–202
(Continued )

3612
A. OLYAEI ET AL.
Table 1. Continued
Method A
Time=h Yield (%)
Entry
Amine
Product
4
Mp (ꢀC)
169–170
8
4h
4
4
78
9
4i
75
132–134
One-pot three-component reaction of 2-naphthol (1a), 2,7-dihydroxy
naphthalene (1b), heteroaryl amines (2-aminopyrimidine 2a, 2-aminopyrazine 2b,
2-aminopyridine 2c, 3-aminopyridine 2d, 2-aminothiazole 2e and 3-amino-2-
chloropyridine 2f) 2a-f and aqueous glyoxalic acid (3) in water at room temperature
(method A) in appropriate times (see Table 1) directly afforded N-heteroaryl
a-naphthylglycines 4a–i in moderate to high yields (Scheme 1). Also, these reactions
were carried out under reflux conditions (method B). In this procedure, the products
4h and 4i not only were formed but also sticky mixtures were obtained. However,
these products were obtained at room temperature in 78% and 75% yields, respect-
ively. The results are summarized in Table 1.
Scheme 1. Synthesis of a-naphthylglycine derivatives 4.

GREEN SYNTHESIS OF N-HETEROARYL a-NAPHTHYLGLYCINES
3613
After screening two methods, method A has advantages such as efficient, gen-
erality and simplicity of the procedure, clean and easy products separation by fil-
tration. But, the formation of some products in this method needs a little longer
reaction time. Further studies showed that increasing temperature (method B) did
not improve the yields of the products. In this method, after completion of the reac-
tion, water was decanted and the white precipitated product was separated upon
addition of ethanol to the mixture. As shown in Table 1, with 2,7-dihydroxynaphtha-
lene, the reaction showed higher rate than 2-naphthol. In addition, when amines with
electron poor nature such as 2-aminopyrimidine were used, the reaction proceeded
relatively higher rate than other amines. Thus, the naphthols bearing electron-
donating and amines contaning withdrawing atoms in ortho position are desirable
substrates for these reactions.
To make insight into the reaction mechanism, we initially studied the reaction
of 2-naphthol with glyoxalic acid. No reaction progress was observed during several
hours. When the iminoacid product obtained from amine condensation with glyox-
alic acid was treated with 2-naphthol under the reaction conditions, the correspond-
ing N-heteroaryl a-naphthylglycine was obtained. In our one-pot reaction, it might
be concluded that iminoacid generated in situ from reaction of amine and glyoxalic
acid, reacts with 2-naphthol affording the a-naphthylglycine.
In summary, we described a convenient, efficient and environmentally greener
methodology for the synthesis of novel N-heteroaryl a-arylglycines containing naph-
thol rings in water in the absence of acid catalyst at room temperature (method A)
and under reflux conditions (method B) in moderate to high yields. In addition to the
efficiency and simplicity by method A, this protocol describes generality, clean, low
cost procedure and easy products separation for the synthesis of these products. To
the best of our knowledge, this is the first report on the synthesis of N-heteroaryl
a-naphthylglycine derivatives.
EXPERIMENTAL
All commercially available chemicals and reagents were used without further
purification. Melting points were determined with an Electrothermal model 9100
apparatus and are uncorrected. IR spectra were recorded on a Shimadzu 4300 spec-
trophotometer. The 1H and 13C NMR spectra were recorded in DMSO-d6 on Bruker
DRX-500 AVANCE spectrometers. Chemical shifts (d) are reported in ppm and are
referenced to the NMR solvent. Mass spectra of the products were obtained with a
HP (Agilent technologies) 5937 Mass Selective Detector. Elemental analyses were
carried out by a CHN-O-Rapid Heraeus elemental analyzer (Wellesley, MA).
General Procedure for the Synthesis of N-Heteroaryl-2-aryl
Glycines (Method A)
To a solution of heteroarylamine (5 mmol) and glyoxalic acid (50% aqueous
solution) (5 mmol) in water (10 mL) was added b-naphthol or 2,7-dihydroxy naph-
thalene (5 mmol) and the mixture was stirred for the appropriate times (see
Table 1) at ambient temperature. Reaction progress was monitored by TLC. After
completion of the reaction, the obtained precipitate was filtered, washed with cold

3614
A. OLYAEI ET AL.
EtOH, dried and purified by recrystallization from DMSO-H2O to give colorless
crystals of 4a-i.
General Procedure for the Synthesis of N-Heteroaryl-2-aryl
Glycines (Method B)
To a solution of heteroarylamine (5 mmol) and glyoxalic acid (50% aqueous
solution) (5 mmol) in water (10 mL) was added b-naphthol or 2,7-dihydroxy naph-
thalene (5 mmol) and the mixture was stirred for the appropriate times (see
Table 1) under reflux condition. Reaction progress was monitored by TLC. After
completion of the reaction, water was decanted and the white precipitated product
was separated upon addition of ethanol (10 mL) to the mixture with stirring, while
cooling at 0–5 ꢀC. The precipitate was filtered, washed with cold EtOH, dried and
purified by recrystallization from DMSO-H2O to give colorless crystals of 4a-g.
N-(2-Pyrimidyl)-2-(2-hydroxynaphthalen-1-yl) glycine (4a). IR (KBr):
3313, 3150–2466, 1712, 1595, 1573, 1531, 1232 cmꢁ1
;
1H NMR (500 MHz,
DMSO-d6): d 6.55 (d, 1H, J ¼ 8.6 Hz, methine-H), 6.67 (t, 1H, J ¼ 4.7 Hz,
pyrimidine-H5), 6.97 (d, 1H, J ¼ 8.6 Hz, NH), 7.2–8.09 (m, 6H, naphthalene-H),
8.35 (d, 2H, J ¼ 4.7 Hz, pyrimidine-H4 and H6), 10.24 (br, 1H, OH), 12.45 (br,
1
1H, COOH); H NMR (500 MHz, DMSO-d6 þ D2O): d 6.53 (s, 1H, methine-H),
6.67 (t, 1H, J ¼ 4.7 Hz, pyrimidine-H5), 7.2–8.06 (m, 6H, naphthalene-H), 8.33 (d,
2H, J ¼ 4.7 Hz, pyrimidine-H4 and H6);13C NMR (125 MHz, DMSO-d6): d 50.60,
111.90, 116.91, 119.08, 123.38, 123.44, 127.57, 129.09, 129.36, 130.36, 133.59,
154.21, 158.88, 162.53, 174.00; MS (EI): m=z 296 (M þ 1)þ, 295 (M)þ, 277, 251,
220, 156, 128; Anal. calcd. for C16H13N3O3: C, 65.08; H, 4.40; N, 14.22. Found:
C, 65.15; H, 4.35; N, 14.29.
N-(2-Pyrimidyl)-2-(2,7-dihydroxynaphthalen-1-yl)
glycine
(4b). IR
(KBr): 3396, 3211–2624, 1722, 1635, 1595, 1531, 1458, 1344, 1284, 1228, 1155cmꢁ1
;
1H NMR (500 MHz, DMSO-d6): d 6.40 (d, 1H, J ¼ 8.7 Hz, methine-H), 6.67 (t,
1H, J ¼ 4.7 Hz, pyrimidine-H5), 6.84 (d, 1H, J ¼ 8.7 Hz, NH), 6.87–7.67 (m, 5H,
naphthalene-H), 8.34 (d, 2H, J ¼ 4.7 Hz, pyrimidine-H4 and H6), 9.70 (s, 1H,
OH), 10.08 (br, 1H, OH), 12.36 (br, 1H, COOH); 13C NMR (125 MHz, DMSO-d6):
d 50.77, 105.30, 111.88, 115.09, 115.58, 115.91, 123.84, 130.16, 131.01, 135.37,
154.56, 157.10, 158.92, 162.62, 174.01; MS (EI): m=z 311 (M)þ, 293, 264, 248, 200,
172, 144, 115, 95; Anal. calcd. for C16H13N3O4: C, 61.73; H, 4.18; N, 13.50. Found:
C, 61.68; H, 4.20; N, 13.58.
N-(2-Pyridyl)-2-(2-hydroxynaphthalen-1-yl)glycine (4c). IR (KBr): 3255–
1
2563, 1662, 1625, 1573, 1512, 1442, 1386, 1247, 1164 cmꢁ1; H NMR (500 MHz,
DMSO-d6): d 6.46 (d, 1H, J ¼ 5.6 Hz, methine-H), 7.03 (d, 1H, J ¼ 5.6 Hz, NH),
6.54, 6.75, 7.14–8.09 (m, 10H, pyridine-H and naphthalene-H), 11.34 (br, 2H, OH
and COOH); 13C NMR (125 MHz, DMSO-d6): d 50.45, 110.20, 112.97, 117.71,
119.56, 123.36, 123.83, 127.30, 129.25, 129.30, 130.17, 133.73, 137.68, 147.60,
154.33, 158.67, 174.65; MS (EI): m=z 294 (M)þ, 276, 250, 184, 156, 144, 128, 115,
94; Anal. calcd. for C17H14N2O3: C, 69.38; H, 4.76; N, 9.52. Found: C, 69.44; H,
4.72; N, 9.56.

GREEN SYNTHESIS OF N-HETEROARYL a-NAPHTHYLGLYCINES
3615
N-(2-Pyridyl)-2-(2,7-dihydroxynaphthalen-1-yl)glycine (4d). IR (KBr):
3249, 3114–2684, 1666, 1625, 1602, 1539, 1487, 1454, 1384, 1307, 1220, 1163 cmꢁ1
;
1H NMR (500 MHz, DMSO-d6): d 6.34 (d, 1H, J ¼ 6.9 Hz, methine-H), 6.83 (d,
1H, J ¼ 6.9 Hz, NH), 6.53, 6.73, 6.87–8.03 (m, 9H, pyridine-H and naphthalene-H),
9.64 (s, 1H, OH), 10.25 (br, 1H, OH); 13C NMR (125 MHz, DMSO-d6): d 50.46,
105.93, 110.09, 112.89, 115.77, 115.80, 115.88, 123.93, 129.97, 130.83, 135.54,
137.55, 147.69, 154.58, 156.87, 158.78, 174.61; MS (EI): m=z 310 (M)þ, 292, 236,
200, 172, 165, 144, 137, 115, 94; Anal. calcd. for C17H14N2O4: C, 65.80; H, 4.51;
N, 9.03. Found: C, 65.84; H, 4.49; N, 9.10.
N-(3-Pyridyl)-2-(2-hydroxynaphthalen-1-yl)glycine (4e). IR (KBr): 3255–
1
2488, 1622, 1573, 1504, 1438, 1377, 1323, 1290, 1253, 1163, 1101 cmꢁ1; H NMR
(500 MHz, DMSO-d6): d 5.97 (s, 1H, methine-H), 6.45 (br, 1H, NH), 7.02–8.14
(m, 10H, pyridine-H and naphthalene-H); 13C NMR (125 MHz, DMSO-d6):
d ¼ 52.29, 116.39, 118.93, 119.26, 123.36, 124.00, 124.38, 127.29, 129.36, 129.37,
130.39, 133.36, 135.97, 137.62, 144.63, 154.12, 174.30; MS (EI): m=z 294 (Mþ),
257, 236, 149, 128, 115, 97; Anal. calcd. for C17H14N2O3: C, 69.38; H, 4.76;
N, 9.52. Found: C, 69.34; H, 4.79; N, 9.58.
N-(3-Pyridyl)-2-(2,7-dihydroxynaphthalen-1-yl)glycine (4f). IR (KBr):
1
3361–2437, 1620, 1571, 1541, 1377, 1294, 1234, 1197 cmꢁ1; H NMR (500 MHz,
DMSO-d6): d 5.79 (s, 1H, methine-H), 6.15 (br, 1H, NH), 6.85–8.10 (m, 9H,
pyridine-H and naphthalene-H), 9.62 (s, 1H, OH); 13C NMR (125 MHz, DMSO-d6):
d 52.44, 106.06, 108.05, 115.48, 115.73, 119.21, 123.97, 124.34, 129.92, 130.18,
135.16, 136.11, 137.72, 144.73, 154.41, 156.46, 174.28; MS (EI): m=z 311 (M þ 1)þ,
310 (M)þ, 292, 262, 236, 199, 151, 128, 115, 94; Anal. calcd. for C17H14N2O4: C,
65.80; H, 4.51; N, 9.03. Found: C, 65.75; H, 4.56; N, 9.10.
N-(3-Chloro-2-pyridyl)-2-(2-hydroxynaphthalen-1-yl)glycine
(4g). IR
(KBr): 3388, 3246–2569, 1704, 1627, 1583, 1490, 1436, 1380, 1288, 1253, 1147 cmꢁ1
;
1H NMR (500 MHz, DMSO-d6): d 6.07–8.19 (m, 11H, methine-H, pyridine-H and
naphthalene-H, NH), 10.48 (s, 1H, OH), 13.13 (s, 1H, COOH); 13C NMR
(125 MHz, DMSO-d6): d 52.15, 118.88, 119.52, 122.75, 123.14, 123.55, 124.68,
127.68, 129.28, 129.62, 130.78, 133.30, 136.94, 136.99, 140.28, 154.34, 173.88; MS
(EI): m=z 328 (M)þ, 310, 283, 247, 200, 183, 172, 156, 144, 128, 127, 115, 92; Anal.
calcd. for C17H13ClN2O3: C, 62.10; H, 3.95; N, 8.52. Found: C, 62.20; H, 4.02; N,
8.50.
N-(2-Thiazolyl)-2-(2,7-dihydroxynaphthalen-1-yl)glycine (4h). IR (KBr):
1
3203–2617, 1608, 1517, 1481, 1460, 1375, 1305, 1222, 1164, 1137 cmꢁ1; H NMR
(500 MHz, DMSO-d6): d 6.21 (s, 1H, methine-H), 6.61–7.96 (m, 8H, thiazole-H
and naphthalene-H, NH), 9.67 (s, 1H, OH), 10.25 (s, 1H, OH); 13C NMR
(125 MHz, DMSO-d6): d 53.58, 105.84, 107.62, 114.97, 115.72, 115.81, 123.84,
130.25, 130.87, 135.41, 138.81, 154.57, 156.93, 169.30, 173.83; MS (EI): m=z 298
(M-18)þ, 268, 253, 199, 172, 160, 144, 115, 100; Anal. calcd. for C15H12N2O4S: C,
56.96; H, 3.79; N, 8.86. Found: C, 56.89; H, 3.75; N, 8.90.
N-(2-Pyazyl)-2-(2-hydroxynaphthalen-1-yl)glycine (4i). IR (KBr): 3225–
1
2326, 1649, 1602, 1573, 1533, 1400, 1342, 1197, 1114 cmꢁ1; H NMR (500 MHz,

3616
A. OLYAEI ET AL.
DMSO-d6): d 6.45–8.15 (m, 11H, methine-H, pyrazine-H, NH and naphthalene-H),
10.25 (br, 1H, OH), 12.45 (s, 1H, COOH); 13C NMR (125 MHz, DMSO-d6): d 49.70,
109.50, 116.50, 119.09, 123.68, 127.51, 129.13, 129.36, 130.15, 130.42, 133.72, 134.86,
142.01, 154.22, 155.24, 174.14; MS (EI): m=z 295 (M)þ, 277, 261, 248, 234, 220, 183,
170, 152, 144, 128, 115, 95; Anal. calcd. for C16H13N3O3: C, 65.08; H, 4.40; N, 14.23.
Found: C, 65.02; H, 4.47; N, 14.29.
ACKNOWLEDGMENT
The authors wish to thank the Research Council of the Payame Noor
University of Qazvin for financial support.
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