Multicomponent one-pot green synthesis of 1-Amidoalkyl-2-naphthols Promoted by p-nitrobenzoic acid under solvent-free condition

Article abstract of DOI:10.14233/ajchem.2014.16707

A series of sixteen 1-amidoalkyl-2-naphthols derivatives were synthesized by one-pot multicomponent condensation reaction of b-naphthol with various aromatic aldehydes and amides under thermal (hot plate and oil bath) and microwave irradiation techniques

Full text of DOI:10.14233/ajchem.2014.16707

Asian Journal of Chemistry; Vol. 26, No. 16 (2014), 5207-5211
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16707
Multicomponent One-pot Green Synthesis of 1-Amidoalkyl-2-naphthols
Promoted by p-Nitrobenzoic Acid Under Solvent-free Condition
1,†
1,†
2
3,*
TIANGANG LI , XING ZHAI , DHARAMVEER SINGH , RAJESH K. SINGH2,* and XUEGONG XU
1Beijing University of Chinese Medicine, Beijing 100029, P.R. China
2Department of Pharmaceutical Chemistry, Shivalik College of Pharmacy, Nangal-140 126, India
3Zhengzhou Traditional Chinese Medicine Hospital, Zhengzhou, P.R. China
*Corresponding authors: E-mail: rksingh244@gmail.com; xgxzhengzhou@126.com
†Both authors contributed equally to this paper.
Received: 16 November 2013;
Accepted: 2 January 2014;
Published online: 28 July 2014;
AJC-15663
A series of sixteen 1-amidoalkyl-2-naphthols derivatives were synthesized by one-pot multicomponent condensation reaction of β-naphthol
with various aromatic aldehydes and amides under thermal (hot plate and oil bath) and microwave irradiation techniques promoted by p-
nitrobenzoic acid and the corresponding products were obtained in good to excellent yield (82-92 %) under solvent-free condition.
Keywords: 1-Amidoalkyl-2-naphthol, p-Nitrobenzoic acid, Multicomponent one-pot reaction, Microwave irradiation, Solvent-free.
temperature, long reaction time, the use of expensive reagents,
low yields of products, high catalyst loading, corrosive reagents,
strongly acidic conditions and further purification of products.
Therefore development and introduction of convenient and
efficient methods for the preparation of 1-amidoalkyl-2-
naphthols is of practical importance is still in demand.
In recent years, green and sustainable chemistry has
become a subject of intensive research and the studies in this
area have led the development of cleaner and relatively benign
chemical processes.Among them, much effort has been devoted
towards multicomponent and microwave assisted organic
synthesis (MAOS)30.
INTRODUCTION
Since the last decade, there is a tremendous growth of
research in the field of one-pot multicomponent reactions for
the synthesis of wide variety of organic compounds. One of
the multicomponent reactions of current interest is synthesis
of 1-amidoalkyl-2-naphthols. The amidoalkyl-naphthols
derivatives were paid much attention in synthetic organic
chemistry for their various biological activities. It has been
reported that 1-amidoalkyl-2-naphthols can be converted to
biological active 1-aminoalkyl-2-naphthols derivatives by an
amide hydrolysis reaction exhibiting depressor and bradycardic
activities in humans1-2. In addition, 1-amidoalkyl-2-naphthols
can also be converted to 1,3-oxazine derivatives3-4 which has
widespread area of useful biological activities5-11. It has been
reported to be an essential synthons for drug design and disco-
very of potent drugs such as nucleoside antibiotics and HIV
In continuation of our earlier work in the development of
novel catalysts for the synthesis of various heterocyclic and
synthetic intermediates31, we now describe a simple, general
and efficient protocol for the synthesis of 1-amidoalkyl-2-
naphthols via one-pot condensation reaction using catalytic
amount of p-nitrobenzoic acid using thermal and microwave
techniques by Method A, B and C. The synthetic approach is
outlined in (Scheme-I).
protease inhibitors such as ritonavir and lipinavir12,13
.
During last few years various methods have been reported
for the synthesis of amidoalkyl-naphthols in the presence of
variety of catalysts such as chlorosulphonic acid14, p-toluene
The p-nitrobenzoic acid is readily available, inexpensive
reagents and environmentally benign light yellow crystals
which is stable and can conveniently be handled and removed
from the reaction mixture. Thus, the remarkable catalytic
activities together with their operational simplicity make them
the most suitable catalyst for the synthesis of 1-amidoalkyl-2-
naphthols. The p-nitrobenzoic acid has earlier been used for
the efficient synthesis of 1,5-benzodiazepines32.
sulphonic acid15, NaHSO4·H2O16, Fe(HSO4)3 , Sr(OTf)2 ,
iodine19, hetropoly acid K5CoW12O40·3H2O20, hetropoly acid
catalysts like cation-exchange resins21, silica supported
perchloric acid22,23, FeCl3·SiO224, montmorillonite K10 clay25,
silica sulfuric acid26, sulfamic acid27, N,N,N',N'-tetrabromo-
benzene-1,3-disulfonamide28 and ionic liquids29. However,
majority of them suffer from several limitations such as high
17
18

5208 Li et al.
Asian J. Chem.
CHO
p
-Nitrobenzoic acid
(0.3 mmol)
OH
O
+
+
NH
R1
H2N
R1
Method(A, B, C)
OH
O
R
R=Various functional groups
R1=Various amides
R
Method A: Microwave irradiation
Method B: Oil bath
Method C: Hot plate
Scheme-I: Synthesis of 1-amidoalkyl-2-naphthols
All the products were identified by their 1H NMR, IR and
CHN data and compared with literature reports.
Spectral data for 1-amidoalkyl-2-naphthols
EXPERIMENTAL
All the chemicals were purchased from commercial
suppliers. The melting points were determined on Veego-
programmable melting point apparatus (microprocessor based)
N-[(2-Hydroxynaphthalen-1-yl)-phenyl-methyl)]-
acetamide (4a): IR(KBr, νmax, cm-1): 3441 (O-H,Ar, str), 3177
(N-H 2 sec-amide, str), 3057 (C-H, Ar, str), 1694 (>C=O,
amide, str), 1555-1462 (C=C, Ar, str), 1243-1095 (C-N/C-O,
str), 770 (C-H,Ar, out of plane , bend), 746 (N-H, out of plane,
bend); 1H NMR (400 MHz, DMSO-d6): δ 9.85 (s, 1H, -CONH),
8.27 (d, J = 12 Hz, Ar-OH) 7.97 (t, J = 8 Hz, 1H, Ar-H), 7.75
(d, J = 8 Hz, 1H, Ar-H), 7.69 (d, J = 8 Hz, 1H, Ar-H), 7.40-
7.12 (m, 9H, Ar-H), 2.04 (s, 3H, -COCH3); Anal. calcd. (%)
for C19H17NO2: C 78.33, H 5.87, N 4.81; Found (%): C 77.47,
H 5.79, N 4.76.
1
and are uncorrected. H NMR spectra were obtained using
Brucker AC-400 F, 400 MHZ spectrometer. IR spectra were
obtained on Perkin Elmer 882 Spectrum and RXI, FT-IR.
Elemental analyses for C, H and N were performed on Thermo-
flash EA-1112 CHNS-OAnalyzer. Reactions were monitored
and the homogeneity of the products was checked by TLC.
All chemicals were dried and freshly prepared prior to use
according to standard procedure.
General procedure for synthesis of 1-amidoalkyl-2-naphthols
Method A: A mixture of substituted aromatic aldehydes
(1 mmol), 2-naphthol (1 mmol) and substituted amides (1.2
mmol) in the presence of effective amount of p-nitrobenzoic
acid (30 mol %, 0.3 mmol) were taken in 20 mL conical flask
and was subjected to microwave irradiation in microwave oven
(LG model MS1927C) at 450 W and each pulse was of 30 s
for the appropriate time to avoid overheating. The progress of
reactions was monitored by TLC (ethyl acetate/n-hexane =
2:8). After completion of the reaction, a solid was obtained. It
was washed with water and filtered. Then the solid residue
was recrystallized from ethanol to get purified product.
Method B: A mixture of substituted aromatic aldehydes
(1 mmol), 2-naphthol (1 mmol) and substituted amides (1.2
mmol) in the presence of effective amount of p-nitrobenzoic
acid (30 mol %, 0.3 mmol) were taken in 100 mL conical flask
and heated in an oil bath at 110-120 °C for the appropriate
time with occasionally stirring. The progress of the reaction
was monitored by TLC. After completion of reaction, mass
was cooled to room temperature, washed with water and filtered.
The solid residue was purified by recrystallization from EtOH
to get purified product.
N-[(4-Chlorophenyl)-(2-hydroxynaphthalen-1-yl)-
methyl)]urea (4d): IR (KBr, νmax, cm-1): 3320 (O-H, Ar, str),
3179 (N-H 2 sec-amide, str), 3022 (C-H,Ar, str), 1694 (>C=O,
amide, str), 1592-1431 (C=C, Ar, str), 1402-1107 (C-N/C-O,
str), 803 (C-H, Ar, out of plane, bend), 830 (C-Cl, str), 744
(N-H, out of plane, bend); 1H NMR (400 MHz, DMSO-d6): δ
8.75 (s,1H, -CONH ), 7.88-7.83 (m, 4H, Ar-H), 7.40-7.27 (m,
7H, Ar-H), 7.59 (d, J = 8 Hz, Ar-OH), 6.09 (bs, 2H, -NH2);
Anal. calcd. (%) for C18H15N2O2Cl: C 66.16, H 4.63, N 8.57;
Found (%): C 66.20, H 4.57, N 8.63.
N-[(4-Dimethylaminophenyl)-(2-hydroxynaphthalen-
1-yl)-methyl)]acetamide (4h): IR (KBr, νmax, cm-1): 3372
(O-H, Ar, str), 3248 (N-H 2 sec-amide, str), 3084 (C-H, Ar,
str), 2924 (C-H, alkane, str), 1652 (>C=O, amide, str), 1581-
1397 (C=C, Ar, str), 1372-1031 (C-N/C-O, str), 827 (C-H, Ar,
out of plane, bend), 698 (N-H, out of plane, bend); 1H NMR
(400 MHz, DMSO-d6): δ 9.68 (s, 1H, -CONH), 7.90 (d, J =
8Hz,Ar-OH), 7.89-7.06 (m, 10H, Ar-H), 6.73 (s, 1H, -CHNH),
3.10 (s, 6H, -N(CH3)2), 2.13 (s, 3H, -COCH3); Anal. calcd.
(%) for C21H22N2O2: C 75.44, H 6.58, N 8.38; Found (%): C
75.76, H 6.84, N 8.36.
Method C: A mixture of substituted aromatic aldehydes
(1 mmol), 2-naphthol (1 mmol) and substituted amides (1.2
mmol) in the presence of effective amount of p-nitrobenzoic
acid (30 mol %, 0.3 mmol) were crushed in mortar and pestle
to a fine powder and transferred into a china dish and heated
on hot plate at 110-120 °C for appropriate time with occasional
stirring. After completion of the reaction, water (10 mL) was
added, filtered and then residue recrystallized from ethyl
alcohol to get pure product.
N-[(4-Methyphenyl)-(2-hydroxy-naphthalen-1-yl)-
methyl)]benzamide (4k): IR (KBr, νmax, cm-1): 3414 (N-H 2
sec-amide, str), 3008 (O-H, Ar, str overlapping with C-H, Ar,
str), 2824 (C-H, alkane, str), 1630 (C=O, amide, str), 1529-
1483 (C=C, Ar, str), 1346-1248 (C-N/C-O, str), 817 (C-H, Ar,
out of plane, bend), 711 (N-H, out of plane, bend); 1H NMR
(400 MHz, DMSO-d6): δ 10.20 (s, 1H, -CONH), 8.93 (br d, J
= 8Hz,1H Ar-OH), 7.84-7.70 (m, 4H, Ar-H), 7.51-7.16 (m,
9H, Ar-H), 7.02 (d, J = 8Hz, 2H, Ar-H), 2.23 (s, 3H, -CH3);

Vol. 26, No. 16 (2014)
Green Synthesis of 1-Amidoalkyl-2-naphthols Promoted by p-Nitrobenzoic Acid 5209
Anal. calcd. (%) for C25H21NO2: C 81.72, H 5.76, N 3.81; Found
(%): C 81.63, H 5.68, N 3.88.
TABLE-1
OPTIMIZATION STUDY OF p-NITROBENZOIC ACID (PNBA)
FOR THE SYNTHESIS OF 1-AMIDOALKYL-2-NAPHTHOLS
N-[(3-Nitrophenyl)-(2-hydroxynaphthalen-1-yl)-
methyl)]urea (4l): IR (KBr, νmax, cm-1): 3636 (O-H, Ar, str),
3399-3316 (N-H 2 sec-amide, str), 3183-3076 (C-H, Ar, str),
1640 (>C=O, amide, str), 1481-1436 (C=C,Ar, str), 1346-1068
(C-N/C-O, str), 1528 (N-O, str), 810 (C-H, Ar, out of plane,
Method B
Method A
Time (min)/
yield (%)
Method C time
(min)/ yield (%)
(Hot-plate)
Time
(min)/
yield (%)
PNBA
(mmol)
Entry
(Microwave)
(Oil-bath)
1
bend), 744 (N-H, out of plane, bend); H NMR (400 MHz,
1.
2.
3.
4.
0.1
0.2
0.3
0.4
10/75
10/82
10/88
10/88
15/71
15/80
15/85
15/86
20/56
20/62
20/66
20/66
DMSO-d6): δ 8.93 (s, 1H, -CONH), 8.64 (d, J = 8Hz, Ar-OH),
8.11-7.60 (m, 7H, Ar-H), 7.59-7.23 (m, 3H, Ar-H), 6.88 (s, 2H,
-NH2), 6.36 (s, 1H, -CHNH);Anal. calcd. (%) for C18H15N3O4:
C 64.09, H 4.48, N 12.46; Found (%): C 64.16, H 4.56, N 12.38.
N-[(2,5-Dimethoxyphenyl)-(2-hydroxynaphthalen-1-
yl)-methyl)]acetamide (4o): IR (KBr, νmax, cm-1): 3367 (O-
H, Ar, str overlapping with N-H 2 sec-amide, str), 3056 (C-H,
Ar, str), 2927-2832 (C-H, alkane, str), 1640 (>C=O, amide,
str), 1595-1408 (C=C,Ar, str), 1235-1043 (C-N/C-O, str), 814
(C-H, Ar, out of plane, bend), 748 (N-H, out of plane, bend);
1H NMR (400 MHz, DMSO-d6): δ 9.68 (s, 1H, -CONH), 8.45
(d, J = 8Hz, 1H), -7.88-7.04 (m, 9H,Ar-H), 6.45 (s, 1H, -CHNH),
3.62 (s, 3H, -OCH3), 3.45 (s, 3H, -OCH3), 1.87 (s, 3H, -COCH3);
Anal. calcd. (%) for C21H21NO4: C 71.78, H 6.02, N 3.99; Found
(%): C 71.50, H 6.50, N 3.90.
TABLE-2
p-NITROBENZOIC ACID (PNBA) (0.3 mmol, 30 mol %)
CATALYZED SYNTHESIS OF 1-AMIDOALKYL-2-NAPHTHOLS
Time (min)/Yield (%)
m.p. (°C)
(Lit.)
Entry
R
R1 Producta
Method Method Method
A
B
C
1
2
3
4
5
6
H
CH3
10/88 15/85 20/66 242-245
(245-246)22
4a
4b
4c
4d
4e
4f
H
NH2
C6H5
NH2
CH3
C6H5
11/85 16/86 19/65 171-172
(170-173)29b
H
9/83 16/85 19/67 234-237
(234-236)15
4-Cl
4-Cl
4-Cl
8/90 16/88 25/72 165-167
(166-168)29b
N-[(4-Chloro-phenyl)-(2-hydroxynaphthalen-1-yl)-
methyl)]nicotinamide (4p): IR (KBr, νmax, cm-1): 3340 (N-H,
2 sec-amide, str), 3200 (O-H, Ar, str), 3057-3021(C-H, Ar, str),
1654 (>C=O, amide, str), 1596-1464 (C=C,Ar, str), 1371-1032
(C-N/C-O, str), 883-856 (C-H, Ar, out of plane, bend), 738
(C-Cl, str), 716 (N-H, out of plane, bend); 1H NMR (400 MHz,
DMSO-d6): δ 8.55 (d, J = 8Hz, Ar-OH), 7.89-7.85 (m, 4H, Ar-H),
7.62-7.13 (m, 10H, Ar-H), 6.66 (s, 1H, -CHNH); Anal. calcd. (%)
for C21H21NO4: C 71.78, H 4.37, N 7.20; Found (%): C 71.10,
H 4.51, N 7.95.
9/92 14/88 23/74 222-224
(223-225)22
8/91 13/87 21/74 173-175
(175-177)29b
7
8
4-N(CH3)2 NH2
4-N(CH3)2 CH3
11/87 20/85 25/70 205-207
14/84 26/82 28/64 122-124
(123-125)24
4g
4h
9
4-CH3
NH2
CH3
C6H5
NH2
CH3
C6H5
12/82 25/80 32/62 120-122
(118-120)17
4i
4j
10 4-CH3
11 4-CH3
12 3-NO2
13 3-NO2
14 3-NO2
14/83 22/82 30/61 222-224
(222-223)24
RESULTS AND DISCUSSION
12/82 24/79 23/60 1190-191
(190-192)29d
4k
4l
In order to optimize the quantity of p-nitrobenzoic acid,
we carried out the synthesis of N-[4-chloro-phenyl-(2-
hydroxynapthalene-1-yl)-methyl] acetamide by using 2-
naphthol, 4-chloro benzaldehyde and acetamide in the ratio
(1:1:1.2 mmol) with different quantities of p-nitrobenzoic acid
at same temperature and time under solvent free conditions. It
was found that the best result was obtained when the reaction
was carried in the presence of 0.3 mmol (30 mol %) of p-nitro-
benzoic acid (Table-1, Entry-3). The fewer amounts gave a
low yield even after long reaction time and the more amounts
could not cause the obvious increase for the yield of product.
Therefore, 0.3 mmol of catalyst was chosen as the optimal
quantity of p-nitrobenzoic acid.
8/92 13/89 20/72 192-194
(194-196)
9/92 16/88 22/65 242-243
(241-242)22
4m
4n
4o
4p
9/89 15/81 21/67 213-215
(214-216)29b
15 2,5-(OCH3)2 CH3
12/82 20/80 20/63 252-253
(251-253)22
16 4-Cl CH3
8/92 12/90 13/68 209-211
aAll known products have been reported previously inthe literature and were
characterized by comparison of IRand NMRspectra with authentic samples.
As reported in literatures, a mechanism for the synthesis
of 1-amidoalkyl-2-naphthols is shown in Scheme-II. A role
of p-nitrobenzoic acid has been proposed to activate the
aldehyde by binding H+ with the oxygen atom which ultimately
enhances the electrophilicity of the aldehyde and leads to
reduction in reaction time. The condensation of 2-naphthol
with the activated aldehyde give ortho-quinone (o-QMs) as a
highly reactive and ephemeral intermediate. The same ortho-
quinone methides, generated in situ, have been reacted with
amide to form 1-amidoalkyl-2-naphthol derivatives. Thus, the
2-naphthol acts as Michael acceptors and araldehydes as
nucleophile resulting in Michael adduct under the influence
Slight excess of amide was found to be advantageous.
Hence, molar ratio of aromatic aldehyde to amide was kept to
be (1:1.2 mmol). Encouraged by these results, a wide variety
of aromatic aldehydes and amides were treated with β-naphthol
using p-nitrobenzoic acid under the optimized conditions to
afford the corresponding 1-amidoalkyl-2-naphthols (Table-2)
in good to excellent yields at 110-120 °C without formation
of any side products such as dibenzoxanthenes, which are
normally observed under the influence of strong acids. It is
important to note that the synthesis of 1-amidoalkyl-2-naphthols
could not be achieved in the absence of catalyst.

5210 Li et al.
Asian J. Chem.
NO
2
H
OOC
O
R1
H
OH2
O
Enhances the electrophilicity
of aldehyde
R1 C H
O
PNBA
R1 C H
OH
NO
2
OOC
HOOC
H2O
NO
2
Act as nucleophile
R1
R1
NHCOCH3
OH
NH2COCH3
R1
O
O
Catalyst Regeneration
H
COOH
NO
2
OOC
OOC
o-QMs
NO
O N
2
2
Scheme-II: Mechanism of action of p-nitrobenzoic acid promoted synthesis of 1-amidoalkyl-2-naphthols
4. A.H. Kategaonkar, S.S. Sonar, K.F. Shelke, B.B. Shingate and M.S.
Shingare, Org. Commun., 3, 1 (2010).
of p-nitrobenzoic acid. The electron withdrawing groups
(EWD) substituted on benzaldehyde in o-QM intermediate
increase the rate of 1, 4-nucleophilic addition reaction because
of alkene LUMO is at lower energy in the neighboring with-
drawing groups than electron donating groups (EDG). Hence
benzene ring with electron withdrawing groups gave better
yield as compared to electron donating groups.
5. Y. Kusakabe, J. Nagatsu, M. Shibuya, O. Kawaguchi, C. Hirose and S.
Shirato, J. Antibiot., 25, 44 (1972).
6. J.B. Chylinska, T. Urbanski and M. Mordarski, J. Med. Chem., 6, 484
(1963).
7. J.L. Peglion, J.Vian, B. Goument, N. Despaux,V.Audinot and M.J. Millan,
Bioorg. Med. Chem. Lett., 7, 881 (1997).
8. H. Ren, S. Grady, D. Gamenara, H. Heinzen, P. Moyna, S. Croft, H. Kendrick,
V. Yardley and G. Moyna, Bioorg. Med. Chem. Lett., 11, 1851 (2001).
9. F. Benedini, G. Bertolini, R. Cereda, G. Doná, G. Gromo, S. Levi, J.
Mizrahi and A. Sala, J. Med. Chem., 38, 130 (1995).
10. R.D. Clark, J.M. Caroon, A.F. Kluge, D.B. Repke, A.P. Roszkowski,
A.M. Strosberg, S. Baker, S.M. Bitter and M.D. Okada, J. Med. Chem.,
26, 657 (1983).
Conclusion
In conclusion, we have found p-nitrobenzoic acid as the
best promoter for the synthesis of 1-amidoalkyl-2-naphthols
under solvent-free conditions. It is noted that the solvent-free
microwave irradiation can promote reactive pathways in very
convenient way from green chemical point of view compared
to the direct hot plate heating method. These advantages makes
this protocol an attractive and user friendly alternative for the
synthesis of 1-amidoalkyl-2-naphthols.
11. J.B. Chylinska, M. Janowiec and T. Urbanski, Br. J. Pharmacol., 43, 649
(1971).
12. S. Knapp, Chem. Rev., 95, 1859 (1995).
13. S.M. Vrouenraets, W.F. Wit, J. Tongeren and J.M. Lange, Expert Opin.
Pharmacother., 8, 851 (2007).
14. M. Anary-Abbasinejad, A. Hassanabadi, M. Kamali-Gharamaleki, A.
Saidipoor, H. Anaraki-Ardakani, J. Chem. Res., 644 (2007).
15. H.R. Shaterian and H. Yarahmadi, Synlett, 916 (2006).
16. H.R. Shaterian and H. Yarahmadi, ARKIVOC, 105 (2007).
17. H.R. Shaterian, H. Yarahmadi and M. Ghashang, Bioorg. Med. Chem.
Lett., 18, 788 (2008).
ACKNOWLEDGEMENTS
The authors gratefully acknowledged to College Managing
Committee and Principal, Shivalik College of Pharmacy,
Nangal, Punjab for constant encouragement and support. This
research was supported by Project of Beijing University of
Chinese Medicine (2014-JYB-JS078 hold by Tiangang Li) and
Project of Beijing University of Chinese Medicine (14013 hold
by Xing Zhai). Thanks are also due to SAIF, Panjab University,
Chandigarh for cooperation in getting the spectral data.
18. W.K. Su, W.Y. Tang, J.J. Li, J. Chem. Res., 123 (2008).
19. B. Das, K. Laxminarayana, B. Ravikanth and R. Rao, J. Mol. Catal.
Chem., 261, 180 (2007).
20. L. Nagarapu, M. Baseeruddin, S. Apuri and S. Kantevari, Catal.
Commun., 8, 1729 (2007).
21. S.B. Patil, P.R. Singh, M.P. Surpur and S.D. Samant, Synth. Commun.,
37, 1659 (2007).
22. H.R. Shaterian, H.Yarahmadi and M. Ghashang, Tetrahedron, 64, 1263
(2008).
23. B. Das, D.N. Kumar, K. Laxminarayana and B. Ravikanth, Helv. Chim.
Acta, 90, 1330 (2007).
REFERENCES
24. H.R. Shaterian and H. Yarahmadi, Tetrahedron Lett., 49, 1297 (2008).
25. S. Kantevari, S.V.N. Vuppalapati and L. Nagarapu, Catal. Commun., 8,
1857 (2007).
1. A.Y. Shen, C.T. Tsai and C.L. Chen, Eur. J. Med. Chem., 34, 877 (1999).
2. I. Szatmari and F. Fulop, Curr Org Synth, 1, 155 (2004).
3. M. Damodiran, N. Panneer Selvam and P.T. Perumal, Tetrahedron Lett.,
50, 5474 (2009).
26. G. Srihari, M. Nagaraju and M.M. Murthy, Helv. Chim. Acta, 90, 1497
(2007).

Vol. 26, No. 16 (2014)
Green Synthesis of 1-Amidoalkyl-2-naphthols Promoted by p-Nitrobenzoic Acid 5211
27. (a) S.B. Patil, P.R. Singh, M.P. Surpur and S.D. Samant, Ultrason.
Sonochem., 14, 515 (2007); (b) R.R. Nagawade and D.B. Shinde, Chin.
J. Chem., 25, 1710 (2007).
31. (a) R. Duvedi and R.K. Singh, Asian J. Chem., 24, 5665 (2012); (b) S.
Sharma, D.N. Prasad and R.K. Singh, J. Chem. Pharm. Res, 3, 382
(2011); (c)A. Sandhar, D.N. Prasad and R.K. Singh, Indian J. Heterocycl.
Chem., 21, 369 (2012); (c) A. Sandhar, D.N. Prasad, A. Kapoor and
R.K. Singh, Curr. Res. Chem., 4, 68 (2012); (d) S. Malik, S. Sharma
and R.K. Singh, Asian J. Chem., 24, 5669 (2012); (e) P. Kaur, H.
Sharma, R. Rana, D.N. Prasad and R.K. Singh, Asian J. Chem, 24,
5649 (2012); (f) A. Sandhar and R.K. Singh, Asian J. Chem., 24, 5643
(2012); (g) A. Sandhar and R.K. Singh, Chem. Sci. Trans., 2(S1), 176
(2012); (h) R.K. Singh, B. Singh, R. Duvedi and S. Kumar, Res. Chem.
Intermed., (2014); doi:10.1007/s11164-013-1513-5.
28. R. Ghorbani-Vaghei and S.M. Malaekehpour, Cent. Eur. J. Chem., 8,
1086 (2010).
29. (a) A. Kumar, M.S. Rao, I. Ahmad and B. Khungar, Can. J. Chem., 87,
714 (2009); (b) H. Khabazzadeh, K. Saidi and N. Seyedi, J. Chem.
Sci., 121, 429 (2009); (c) A.R. Hajipour, F. Ghayeb, N. Sheikhan and
A.E. Ruoho, Tetrahedron Lett., 50, 5649 (2009); (d) S.B. Sapkal, K.F.
Shelke, B.R. Madje, B.B. Shingate and M.S. Shingare, Bull. Korean
Chem. Soc., 30, 2887 (2009); (e) T.T. She, Z.L. Liu and K. Gong,
Chinese J. Appl. Chem., 27, 778 (2010).
32. R. Varala, R. Enugala and S.R. Adapa, J. Braz. Chem. Soc., 18, 291
(2007).
30. (a) P.T. Anastas and J.C. Warner, Green Chemistry: Theory and Practice;
Oxford University Press, Oxford, UK (1998); (b) P.T. Anastas and T.
Williamson, Green Chemistry, Frontiers in Benign Chemical Synthesis
and Process; Oxford University Press, Oxford, UK (1998).