Silver-catalyzed regioselective synthesis of acridines, quinolines, and naphthalenes from 3-(2-alkynyl)aryl-β-ketoesters

Article abstract of DOI:10.1016/j.tet.2012.08.068

A facile, efficient, and general synthetic method for a wide range of medicinally useful 2-carboxylate derivatives of acridinols, quinolinols, and naphthalenols has been developed via silver-catalyzed electrophilic cyclization of 3-(2-alkynyl)aryl-β-ketoesters. The designed reaction involved selective C-C bond formation on more electrophilic alkynyl carbon, which resulted in the regioselective 6-endo-dig cyclized product, as confirmed by X-ray crystallographic studies. The deuterium labeling experiments were performed to support the proposed mechanism. The synthetic methodology accommodates wide functional group variations on alkyne, which proves to be highly advantageous for structural and biological activity assessments.

Full text of DOI:10.1016/j.tet.2012.08.068

Tetrahedron 68 (2012) 9035e9044
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Silver-catalyzed regioselective synthesis of acridines, quinolines,
and naphthalenes from 3-(2-alkynyl)aryl-
b-ketoesters
,
,
Satya Prakash Shukla a, Rakesh Tiwari a b, Akhilesh Kumar Verma a
*
a Department of Chemistry, University of Delhi, Delhi 110007, India
b Department of Biomedical & Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 June 2012
Received in revised form 11 August 2012
Accepted 21 August 2012
Available online 30 August 2012
A facile, efficient, and general synthetic method for a wide range of medicinally useful 2-carboxylate
derivatives of acridinols, quinolinols, and naphthalenols has been developed via silver-catalyzed elec-
trophilic cyclization of 3-(2-alkynyl)aryl-b-ketoesters. The designed reaction involved selective CeC bond
formation on more electrophilic alkynyl carbon, which resulted in the regioselective 6-endo-dig cyclized
product, as confirmed by X-ray crystallographic studies. The deuterium labeling experiments were
performed to support the proposed mechanism. The synthetic methodology accommodates wide
functional group variations on alkyne, which proves to be highly advantageous for structural and bi-
ological activity assessments.
Keywords:
Electrophilic cyclization
Regioselective
Enolates
Ó 2012 Elsevier Ltd. All rights reserved.
Diketoacid
Silver-catalyzed
1. Introduction
heterocyclic compounds with requisite DKAs functionality under
mild reaction condition still have to be explored. The most common
Transition-metal-catalyzed electrophilic cyclization of alkynes
and carbonecarbon bond formation using enolates have made
a large contribution in organic chemistry for the synthesis of a va-
riety of natural products, heterocycles, and carbocycles.1 Among the
various transition metals employed, silver-catalyzed reactions have
gathered remarkable importance because of their ability to activate
approaches for the synthesis of acridines proceed via correspond-
ing acridones,12 aminobenzannulation13 cycloisomerisation,14 and
[4þ2] annulations of benzynes.15 Most of the methods for the
synthesis of acridines require rather harsh conditions.16
various p
-systems at low-catalyst loading.2
O
N
OH
O
N
OMe
OH
O
The biochemical properties and therapeutic applications of
polycyclic compounds largely depend on substituents in the basic
structure. Acridines, quinolines and naphthalenes, have demon-
strated significant biological activity against cancer,3 viruses,4
bacteria,5 parasites,6 fungus,7 Alzheimer’s disease,8 and HIV/
AIDS.9 Substrates with diketoacid (DKAs) functionality have been
disclosed as promising HIV-1 integrase (IN) inhibitor.10 Acridine
based alkaloids, such as Glyfoline, Acronycine (Fig. 1, A and B), and
quinoline based compound C with analogous DKAs functionality,
have found their application as potential antitumor and anti-HIV
agents.11 Thus, the development of novel and efficient routes for
rapid access to such functionalized heterocycles under mild con-
ditions are of high demand.
OMe
OMe
N
Bn
HO
O
OMe
OMe
A
Glyfoline (antitumor)
B
Acronycine (antitumor)
C
anti-HIV
Fig. 1. Selected biologically active acridines and quinolines.
Prompted by importance of these heterocycles and in continu-
ation of our ongoing efforts in the synthesis of heterocycles17 by the
electrophilic cyclization of alkynes, we herein, report a straight
forward approach for the synthesis of acridinol, quinolinol, naph-
thalenol and benzothiophenol via silver-catalyzed electrophilic
Although several reports are available for synthesis of these
heterocycles, yet the efficient and general routes to synthesize such
cyclization of 3-(2-alkynyl)aryl-
DKAs functionality in excellent regioselectivity at room tempera-
ture. ortho-Alkynyl- -keto esters 3 required for the reaction were
b-ketoesters (3aet) with requisite
b
readily prepared from easily accessible ortho-alkynyl aldehydes 1,
by reacting it with ethyl 2-diazoacetate 2 using NbCl5 in CH2Cl2 at
* Corresponding author. E-mail address: averma@acbr.du.ac.in (A.K. Verma).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.08.068

9036
S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
25 ꢀC.18 Alkynes 3 were then subjected to electrophilic cyclization
using AgOTf as a catalyst in CH2Cl2 to afford the desired product 4
(Scheme 1, C).
instead of AgNO3, afforded the desired product 4a in 58% yield
(entry 4). Various solvents like CH3CN, CH2Cl2, H2O, DMSO, DMF,
and methanol were screened at low and elevated temperatures to
find an appropriate system for the proposed reaction. From entries
5e10 in Table 1, it is apparent that CH2Cl2 was found to be quite
successful for the transformation, as compound 4a was obtained in
a 75% yield. The use of AgOAc afforded the desired product 4a only
in 45% yield; whereas, other triflates like CuOTf and HOTf were
found to be ineffective (entries 11e13). The combination of AgOTf
(10.0 mol %) in CH2Cl2 (2.0 mL) at 25 ꢀC was found to be most
suitable for the reaction.
A. Synthesis of naphthalenols by Ciufolini and Wiess
OH
OH
OH
COOMe
R
COOMe
COOMe
i, ii
iii
I
R
(i)
, cat. CuCl, Cat. Pd(PPh ) , t-BuNH , PhMe, RT
3 4 2
R
H
(ii) PCC, CH2Cl2, RT (iii) CHCl3, CSA, reflux
Table 1
B (i). Attempt to synthesize acridinols by Belmont and co-workers
Optimization of reaction conditiona
O
OH
COOEt
COOEt
CHCl3, CSA, reflux
15 % yield
N
N
n-Bu
n-Bu
B (ii). Synthesis of acridinols derivative by Belmont and co-workers
TBS
Entry
Solvent
Catalyst (mol %)
T
ꢀC
Time (h)
Yieldb (%)
TBS
O
O
O
1
2
3
4
5
6
7
8
CHCl3
CHCl3
CHCl3
CHCl3
CH3CN
CH2Cl2
H2O
DMSO
DMF
MeOH
CH2Cl2
CH2Cl2
CH2Cl2
AgNO3 (5)
AgNO3 (5)
AgNO3 (10)
AgOTf (10)
AgOTf (10)
AgOTf (10)
AgOTf (10)
AgOTf (10)
AgOTf (10)
AgOTf (10)
AgOAc (10)
CuOTf (10)
HOTf (10)
25
25
25
25
25
25
80
3 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
5 h
22
30
44
58
48
75
68
28
32
Trace
45
Trace
Trace
CH2
R
H
[Rh(CO)2Cl]2
toluene,
120 °C, 60-70%
N
N
I
N
R
C. Our designed reaction pathway
O
OH
O
120
120
70
N2
COOEt
CHO
COOEt
AgOTf
(10 mol %)
9
2
OEt
10
11
12
13
NbCl5
CH2Cl2, 25 °C,
12-16 h
X
X
CH2Cl2, 3-5 h
25 °C, 64-83%
X
Y
25
25
25
1
Y
Y
4
3
X = CH, N, S: Y = aryl, alkyl
this work
a
All reactions were performed using 0.5 mmol of the alkyne 3a, in 2.0 mL of
Scheme 1. Previous approaches and our designed reaction pathway.
solvent.
b
Isolated yields.
Previously, Ciufolini and Weiss19 have reported electrophilic
cyclization on the parent benzaldehyde moiety using camphor
sulphonic acid (CSA) in CHCl3 under reflux condition for 8e12 h
(Scheme 1, A). However, the methodology failed on quinoline-
carbaldehyde moiety when Belmont and co-workers20 used same
reaction condition and ended up only with the 15% yield of the
desired product {Scheme 1, B(i)}. This forced them to design a new
strategy for the synthesis of acridinol derivatives14,20 {Scheme 1,
B(ii)}. Our designed strategy accomodates various substrates like
quinolinecarbaldehyde, nicotinaldehyde, benzaldehyde and ben-
zothiophenecarbaldehyde, which afforded various 2-carboxylate
derivative of acridinols, quinolinols, naphthalenols and benzo-
thiophenols, respectively, under mild reaction condition in good
yields. Reaction afforded the 6-endo-dig cyclized products by se-
lective CeC bond formation on the more electrophilic alkynyl car-
bon (Scheme 1, C).
The scope and limitation of this silver-catalyzed electrophilic
cyclization process were next examined by employing various al-
kynes bearing different substituents. The alkyne 3a bearing phenyl
substituent, afforded the desired cyclized product 4a in 75% yield
(Table 2, entry 1). Substrates 3bed bearing electron-releasing
methyl, ethyl, and methoxy groups on the phenyl, para to the tri-
ple bond resulted 6-endo-dig cyclized product 4bed in 78e83%
yields (entries 2e4). Alkyne bearing biphenyl substituent 3e pro-
vided the cyclized product 4e in 76% yield (entry 5). Alkyne 3f
bearing an electron-withdrawing CF3 group on phenyl, para to the
triple bond, afforded the product 4f in 64% yield (entry 6). Having
studied the effect of phenyl ring, we further employed the protocol
for alkyne bearing an electron-rich heterocycle, i.e., thiophene,
afforded the desired product 4g in 82% yield (entry 7). Alkynes
3hej having alicyclic and alkyl substituents were found successful
for the reaction, and the desired cyclized products 4hej were ob-
tained in 70e72% yields (entries 8e10). The propargylphenoxy
substituted alkyne 3k was also subjected to this cyclization and we
were pleased to obtain cyclized product 4k in 69% yield (entry 11).
After obtaining the successful results with ortho-alkynylquino-
lines 3aek, we further extended the scope of this reaction on other
substrates bearing electron-deficient (3len), neutral (3oes) and
electron-rich (3t) heterocyclic nucleus. Alkynes ethyl 3-oxo-3-(2-
(arylethynyl)pyridin-3-yl)propanoate bearing p-tolyl and 1,3-
dimethoxybenzene 3l,m afforded the desired cyclized product
4l,m in 72e79% yields (Table 3, entries 1e2). Furthermore, ethyl 3-
oxo-3-(3-(p-tolylethynyl)pyridin-4-yl)propanoate 3n provided the
product 4n in 73% yield (entry 3).
2. Results and discussion
In order to find the optimal reaction condition, we first analyzed
various factors affecting reaction by using ethyl 3-oxo-3-(2-(phe-
nylethynyl)quinolin-3-yl)propanoate 3a (0.5 mmol) as a starting
substrate. First of all, the reaction was performed with 5.0 mol %
AgNO3 in 2.0 mL of CHCl3 at 25 ꢀC, the cyclized product 4a was
obtained in only 22% yield after 3 h (Table 1, entry 1). However,
when the reaction was further allowed to stir for 5 h, the product 4a
was obtained in 30% yield (Table 1, entry 2). Increasing the amount
of AgNO3 from 5 mol % to 10 mol %, led to the formation of 4a in 44%
yield (entry 3). Further efforts were made to come up with better
conditions, which could afford the product in good yield. Among
the various factors, we first varied silver salt. Employing AgOTf
Further exploring the developed protocol to ethyl 3-oxo-3-(2-
(arylethynyl)phenyl)propanoate 3oes, the desired products 4oes
were obtained in moderate to good yields (Table 3, entries 4e8). The

S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
9037
Table 2
Table 3
Synthesis of 3-aryl/alkylacridinol-2-carboxylatesa
Synthesis of naphthalenes, quinolines, and dibenzothiophenes with DKAs
functionalitya
Entry
Substrate 3
Product 4
Yieldb (%)
Entry
1
Substrate 3
Product 4
Yield (%)b
79
3l
4l
R1
R1
1
2
3
4
5
6
H
Me
Et
OMe
Ph
CF3
3a
3b
3c
3d
3e
3f
H
Me
Et
OMe
Ph
CF3
4a
4b
4c
4d
4e
4f
75
79
78
83
76
64
2
3
3m
4m
72
73
7
3g
3h
3i
4g
4h
4i
82
70
72
3n
4n
8
R2
H
Me
OMe
R2
H
Me
OMe
4
5
6
3o
3p
3q
4o
4p
4q
70
74
79
9
7
3r
4r
80
10
3j
4j
70
69
8
3s
4s
69
11
3k
4k
a
All reactions were performed with 0.5 mmol of the alkynes 3aek, AgOTf
(10.0 mol %) in CH2Cl2 (2.0 mL) at 25 ꢀC for 3e5 h.
b
Isolated yields.
9
3t
4t
75
methyl and methoxygroup present at para of alkynes 3peq, resulted
the cyclized products 4peq, in 74% and 79% yields, respectively
(entries 5e6). The electron-rich thiophene substituted alkyne 3r,
proved favorable for the reaction and afforded desired product 4r in
80% yield (entry 7). The substitution at meta position of the phenyl
ringaffordedthecyclized product 4s in comparativelylower, i.e., 69%
yield (entry 8). Electron-rich alkyneethyl-3-(3-((4-methoxy phenyl)
ethynyl)benzo-[b]thiophen-2-yl)-3-oxopropano
a
All reactions were performed with 0.50 mmol of the alkynes 3let, AgOTf
(10.0 mol %) in CH2Cl2 (2.0 mL) at 25 ꢀC for 3e5 h.
b
Isolated yields.
ate 3t afforded the desired cyclized product 4t in 75% yield (entry 9).
All the synthesized products were fully characterized by the 1H
and 13C NMR method and mass spectroscopic data. The regiose-
lective 6-endo-dig cyclization was unambiguously confirmed by X-
ray crystallographic studies of compounds 4f and 4p (Figs. 2 and 3).
To support the proposed mechanism, reaction of alkyne 3d was
performed in CHCl3 and quenched with D2O, product 5 was ob-
served (Scheme 2). Similar result was obtained, when we per-
formed the reaction in CDCl3 and quenched it with D2O/CD3OD. The
product 4d was obtained when the same reaction was carried out in
CDCl3 and quenched with H2O.21 However, when the reaction was
carried out in CDCl3 with 10.0 equiv of CD3OD, both the compounds
5 and 6 were obtained in 2:3 ratios. Whereas, the formation of
compound 6 occurred because of the presence of Dþ ion in the
reaction medium, sourced by CD3OD. These experiments indicate
that Hþ ion, which replaces Agþ ion, is being accomplished before
workup.
Fig. 2. X-ray crystallographic ORTEP drawing of compound 4f.

9038
S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
Subsequently, replacement of silver ion by Hþ ion and keto-enol
tautomerization of V led to desired cyclized product 4.
3. Conclusions
In summary, a mild and efficient approach for the direct syn-
thesis of medicinally important acridinol, naphthalenol, quinolinol
and benzothiophenol bearing 2-carboxylate group have been
demonstrated. This milder and feasible silver-catalyzed electro-
philic cyclization have been advantageously employed to tolerate
high functional group variation, thereby achieving diversity and
regioselectivity in good yields, which makes it ideal for the gen-
eration of libraries of functionally-substituted scaffolds. The
regioselective 6-endo-dig formation was confirmed by X-ray crys-
tallographic studies. The deuterium labeling experiments proved to
be an additional support for the proposed mechanism.
Fig. 3. X-ray crystallographic ORTEP drawing of compound 4p.
4. Experimental section
4.1. General method
OD
O
COOEt
COOEt
a, b
1H NMR (300 MHz or 400 MHz) and 13C NMR (75 MHz or
100 MHz) spectra were recorded in CDCl3 or in DMSO as specified
and were obtained using Jeol JNM ECX400P (400 MHz) spectrom-
eter and Bruker AV300 (300 MHz) spectrometer. Chemical shifts for
protons are reported in parts per million from tetramethylsilane
with the residual CHCl3 resonance as internal reference. Chemical
shifts for carbons are reported in ppm from tetramethylsilane and
are referenced to the carbon resonance of the solvent. Data are
reported as follows: chemical shift, multiplicity (s¼singlet,
d¼doublet, t¼triplet, q¼quartet, m¼multiplet, dd¼doublet of
doublet), coupling constants in hertz, and integration. High-
resolution mass spectra were recorded on Applied Biosystems
QSTARÒ Elite Hybrid (QqTOF) from Department of Biomedical &
Pharmaceutical Sciences, College of Pharmacy, University of Rhode
Island, Kingston-02881, Rhode Island, USA. Crystal structure anal-
ysis was accomplished on Oxford diffraction (Xcaliber S) single
crystal X-ray diffractometer. TLC analysis was performed on com-
mercially prepared 60 F254 silica gel plates and visualized by either
UV irradiation or by staining with I2. Anhydrous forms of all re-
agents, such as diethyl ether, hexanes, ethyl acetate, CH2Cl2, 2-
chloroquinoline-3-carbaldehyde, 2-bromonicotinaldehyde, 3-
bromoisonicotin aldehyde, 2-bromobenzaldehyde, 3-bromobenzo
[b] thiophene-2-carbaldehyde, ethyl diazoacetate, terminal al-
kynes, Et3N, and the silver salts were used directly as obtained
commercially unless otherwise noted.
N
N
5
3d
OMe
OMe
a = reaction in CHCl3 and quenched with D2O/CD3OD
b = reaction in CDCl3 and quenched with D2O/CD3OD
O
OH
COOEt
COOEt
c
N
N
3d
4d
OMe
OMe
c = reaction in CDCl3 and quenched with H2O
O
OD
P
COOEt
COOEt
d
N
N
3d
OMe
OMe
5: P = H; 6: P = D (2:3 ratio)
d = reaction in CDCl3 with 10 equiv of CD3OD
Scheme 2. Deuterium-labeling experiments.
On the basis of above observations, along with deuterium la-
beling experiments, an assumed pathway for the formation of
cyclized product 4 is illustrated in Scheme 3. Firstly, the AgOTf
coordinates to the triple bond of 3 to form a
undergoes intramolecular nucleophilic attack by the C2 position of
-keto ester onto alkynyl carbon to form the species U.
p
-complex T,14 which
4.2. General procedure for the niobium-catalyzed formation
of the ortho-alkynyl-b-keto esters (3aet)
b
To a solution of CH2Cl2 (10.0 mL), NbCl5 (10.0 mol %) and ortho-
alkynyl aldehydes (1 mmol), ethyl 2-diazoacetate (1.2 mmol) was
added and the reaction mixture was allowed to stir at 25 ꢀC for
12e16 h. The reaction mixture was filtered and diluted with ethyl
acetate and washed with brine solution. The combined organic
fractions were dried over anhydrous Na2SO4 and concentrated
under vacuum to yield the crude product. The crude product was
purified by column chromatography on silica gel using ethyl ace-
tate/hexane as the eluent.
OH
O
O
O
O
O
+Ag
-H
OEt
OEt
OEt
X
X
X
Y
Y
Y
Ag
3
T
O
O
O
O
OH
4.2.1. Ethyl 3-oxo-3-(2-(phenylethynyl)quinolin-3-yl)propanoate (3a).
The product was obtained as a brown oil (247.2 mg, 72%); Rf (15%
ethyl acetate/hexane) 0.33; the compound was obtained as a mixture
COOEt
-Ag
+H
OEt
OEt
H
Y
H
Y
Keto-enol
X
X
X
Y
tautomerization
of keto and enol forms in the ratio of 2:1, 1H NMR (400 MHz, CDCl3)
d:
Ag
U
V
4
12.58 (s, 0.4H, OH) (enol), 8.51 (d, J¼2.9 Hz, 1H, CHaromatic) (keto),
Scheme 3. Proposed mechanism.
8.17e8.10 (m, 1.4H, CHaromatic) (ketoþenol), 7.83e7.70 (m, 2.8H,

S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
9039
CHaromatic) (ketoþenol), 7.67e7.63 (m, 2.8H, CHaromatic) (ketoþenol),
7.54e7.47 (m, 2.0H, CHaromatic) (ketoþenol), 7.35e7.30 (m, 4.4H,
CHaromatic) (ketoþenol), 6.33 (s, 0.4H, C]CH) (enol), 4.30e4.24 (m,
2.8H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.12 (q, J¼7.3 Hz, 2H,
CH2CH3) (keto),1.30 (t, J¼7.3 Hz,1.6H, CH2CH3) (enol),1.13 (t, J¼7.3 Hz,
48.5, 14.3, 14.0; HRMS calcd for C23H19NO4 (Mþ) 373.1314; found
373.1314.
4.2.5. Ethyl 3-(2-(biphenyl-4-ylethynyl)quinolin-3-yl)-3-oxopro-
panoate (3e). The product was obtained as a brown oil (293.6 mg,
70%); Rf (15% ethyl acetate/hexane) 0.28; the compound was ob-
tained as a mixture of keto and enol forms in the ratio of 2:1, 1H
3H, CH2CH3) (keto); 13C NMR (100 MHz, CDCl3)
d: 193.5, 172.7, 171.2,
168.3, 166.9, 163.6, 148.7, 147.9, 147.0, 139.9, 139.7, 138.1, 136.5, 136.3,
132.8, 132.2, 132.1, 131.3, 129.6, 129.63, 129.55, 129.35, 128.8, 128.76,
128.67, 128.3, 128.25, 128.17, 128.0, 127.1, 127.29, 127.22, 126.1, 121.84,
121.79, 124.4, 106.0, 94.3, 93.7, 93.1, 88.47, 88.41, 88.0, 61.4, 61.0, 60.4,
48.3, 14.1, 13.8; HRMS calcd for C22H18NO3 ([MþH]þ) 344.1287; found
344.1296.
NMR (400 MHz, CDCl3)
1.5H, CHaromatic
(ketoþenol), 8.10e8.00 (m, 3.1H, CHaromatic
(ketoþenol), 7.86e7.64 (m, 4.8H, CHaromatic) (ketoþenol), 7.62e7.49
d: 12.55 (s, 0.5H, OH) (enol), 8.54e8.48 (m,
)
)
(m, 8.3H, CHaromatic) (ketoþenol), 7.35e7.28 (m, 8.0H, CHaromatic
)
(ketoþenol), 6.31 (s, 0.5H, C]CH) (enol), 4.29e4.24 (m, 2.8H, C]
OCH2C]OþCH2CH3) (ketoþenol), 4.10 (q, J¼7.3 Hz, 2H, CH2CH3)
(keto), 1.30 (t, J¼7.3 Hz, 1.6H, CH2CH3) (enol), 1.12 (t, J¼7.3 Hz, 3H,
4.2.2. Ethyl
3-oxo-3-(2-(p-tolylethynyl)quinolin-3-yl)propanoate
(3b). The product was obtained as a brown oil (268.0 mg, 75%); Rf
(15% ethyl acetate/hexane) 0.31; the compound was obtained as
a mixture of keto and enol forms in the ratio of 2:1, 1H NMR
CH2CH3) (keto); 13C NMR (100 MHz, CDCl3)
d: 193.9, 173.4, 171.5,
167.7, 149.8, 148.5, 144.3, 140.8, 139.6, 136.7, 135.2, 132.5, 130.1,
129.8, 129.20, 129.08, 128.7, 128.29, 128.26, 128.06, 128.01, 126.31,
126.12, 125.88, 125.72, 125.4, 125.0, 124.2, 123.9, 123.4, 121.2, 118.6,
96.2, 95.0, 92.1, 86.1, 85.8, 61.4, 61.2, 47.5, 13.2, 13.0; HRMS calcd for
(400 MHz, CDCl3) d: 12.62 (s, 0.5H, OH) (enol), 8.60e8.55 (m, 1.5H,
CHaromatic) (ketoþenol), 8.19e8.00 (m, 3H, CHaromatic) (ketoþenol),
7.92e7.78 (m, 4.2H, CHaromatic) (ketoþenol), 7.63e7.52 (m, 6H,
CHaromatic) (ketoþenol), 7.40e7.21 (m, 6.2H, CHaromatic) (ketoþenol),
6.41 (s, 0.5H, C]CH) (enol), 4.38e4.31 (m, 3H, C]OCH2C]
OþCH2CH3) (ketoþenol), 4.18 (q, J¼7.3 Hz, 2H, CH2CH3) (keto), 2.68
(s, 4.5H, PhCH3) (ketoþenol), 1.38 (t, J¼7.3 Hz, 1.7H, CH2CH3) (enol),
C
28H22NO3 ([MþH]þ) 420.1600; found 420.1598.
4.2.6. Ethyl 3-oxo-3-(2-((4-(trifluoromethyl)phenyl) ethynyl)quino-
lin-3-yl)propanoate (3f). The product was obtained as a brown oil
(284.1, 69%); Rf (15% ethyl acetate/hexane) 0.28; the compound was
obtained as a mixture of keto and enol forms in the ratio of 2.5:1, 1H
1.21 (t, J¼7.3 Hz, 3H, CH2CH3) (keto); 13C NMR (100 MHz, CDCl3)
d:
194.8,173.1,171.6,162.4,161.4,150.9,149.7,143.5,143.0,134.9,134.2,
131.8, 130.8, 130.0, 129.2, 127.9, 127.1, 126.5, 126.0, 125.8, 124.8,
122.3, 121.8, 118.6, 95.5, 94.6, 91.8, 86.3, 86.1, 61.2, 60.2, 60.7, 21.4,
16.3, 15.9; HRMS calcd for C23H20NO3 (Mþ) 357.1365; found
357.1366.
NMR (400 MHz, CDCl3)
d
: 12.63 (s, 0.4H, OH) (enol), 8.61 (d, J¼6.6 Hz,
1H, CHaromatic) (Keto), 8.53e8.37 (m, 0.4H, CHaromatic) (enol),
8.23e8.10 (m, 1.9H, CHaromatic) (ketoþenol), 7.95e7.87 (m, 2.9H,
CHaromatic) (ketoþenol), 7.86e7.78 (m, 2.8H, CHaromatic) (ketoþenol),
7.69e7.58 (m, 4.6H, CHaromatic) (ketoþenol), 6.29 (s, 0.4H, C]CH)
(enol), 4.37e4.30 (m, 2.9H, C]OCH2C]OþCH2CH3) (ketoþenol),
4.17 (q, J¼7.3 Hz, 2H, CH2CH3) (keto),1.38 (t, J¼7.3 Hz, 2.0H, CH2CH3)
(enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3) (keto); 13C NMR (100 MHz,
4.2.3. Ethyl 3-(2-((4-ethylphenyl)ethynyl)quinolin-3-yl)-3-oxopro-
panoate (3c). The product was obtained as
a brown oil
(278.4 mg, 75%); Rf (15% ethyl acetate/hexane) 0.31; the compound
CDCl3) d: 194.2, 173.4, 171.1, 163.1, 162.4, 150.9, 149.3, 146.6, 144.8,
was obtained as a mixture of keto and enol forms in the ratio of
141.7, 140.2, 135.8, 134.7, 134.3, 132.1, 131.0, 129.13, 129.09, 128.5,
127.7,126.16,126.14,125.6,124.51,124.47,124.43,122.9,122.5,120.3,
119.3, 118.8, 96.2, 94.9, 91.6, 87.8, 87.3, 61.4, 61.2, 48.4, 13.7, 12.7;
HRMS calcd for C23H17F3NO3 ([MþH]þ) 412.1161; found 412.1156.
1.3:1, 1H NMR (300 MHz, CDCl3)
d: 12.53 (s, 0.7H, OH) (enol),
7.85e7.79 (m, 1.7H, CHaromatic) (ketoþenol), 7.66e7.59 (m, 1.7H,
CHaromatic) (ketoþenol), 7.55e7.49 (m, 4.4H, CHaromatic) (keto-
þenol), 7.48e7.41 (m, 2.7H, CHaromatic) (ketoþenol), 7.40e7.20 (m,
4.1H, CHaromatic
)
(ketoþenol), 6.26 (s, 0.7H, C]CH) (enol),
4.2.7. Ethyl 3-oxo-3-(2-(thiophen-3-ylethynyl) quinolin-3-yl)prop-
anoate (3g). The product was obtained as a brown oil (255.0 mg,
73%); Rf (15% ethyl acetate/hexane) 0.33; the compound was ob-
tained as a mixture of keto and enol forms in the ratio of 2.5:1 1H
4.36e4.29 (m, 3.4H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.19 (q,
J¼7.2 Hz, 2H, CH2CH3) (keto), 2.69 (q, J¼7.2 Hz, 3.7H, CH2CH3)
(ketoþenol), 1.38 (t, J¼7.3 Hz, 2.2H, CH2CH3) (enol), 1.30e1.20 (m,
8.6H, CH2CH3) (keto); 13C NMR (75 MHz, CDCl3)
d
: 194.9, 173.2,
NMR (400 MHz, CDCl3)
1.4H, CHaromatic
(ketoþenol), 7.62e7.55 (m, 2.8H, CHaromatic
(ketoþenol), 7.51e7.47 (m, 1.4H, CHaromatic) (ketoþenol), 7.43e7.37
d: 12.50 (s, 0.4H, OH) (enol), 7.81e7.76 (m,
170.4, 167.6, 145.6, 145.1, 139.2, 135.2, 133.9, 133.6, 131.8, 131.6,
131.5, 129.9, 129.2, 128.28, 128.13, 128.07, 127.95, 122.1, 121.4, 120.2,
119.7, 96.2, 95.2, 92.2, 87.7, 87.3, 61.3, 60.3, 48.6, 28.9, 15.3, 14.3,
)
)
(m, 2.8H, CHaromatic) (ketoþenol), 7.33e7.30 (m, 1.5H, CHaromatic
)
14.0; HRMS calcd for
372.1576.
C
24H22NO3 ([MþH]þ) 372.1600; found
(ketoþenol), 7.24e7.21 (m, 1.8H, CHaromatic) (ketoþenol), 6.18 (s,
0.4H, C]CH) (enol), 4.27 (q, J¼7.3 Hz, 0.8H, CH2CH3) (enol), 4.25 (s,
2H, C]OCH2C]O) (keto), 4.17 (q, J¼7.3 Hz, 2H, CH2CH3) (keto), 1.34
(t, J¼7.3 Hz, 1.2H, CH2CH3) (enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3)
4.2.4. Ethyl 3-(2-((4-methoxyphenyl)ethynyl) quinolin-3-yl)-3-oxo-
propanoate (3d). The product was obtained as brown oil
a
(keto); 13C NMR (100 MHz, CDCl3)
d: 194.1, 171.5, 169.6, 163.7, 162.6,
(280.0 mg, 75%); Rf (15% ethyl acetate/hexane) 0.25; the compound
was obtained as a mixture of keto and enol forms in the ratio of
150.8, 149.6, 146.4, 143.1, 141.8, 140.8, 139.8, 137.1, 135.4, 134.2, 131.9,
130.7, 129.16, 129.07, 128.1, 127.6, 127.3, 127.0, 126.3, 126.0, 125.9,
122.3, 118.7, 95.1, 94.6, 92.8, 85.4, 84.9, 61.0, 60.8, 48.1, 14.1, 13.9;
HRMS calcd for C20H15NO3S (Mþ) 349.0773; found 349.0773.
2.5:1, 1H NMR (400 MHz, CDCl3)
d
: 12.54 (s, 0.4H, OH) (enol), 8.52
(d, J¼5.8 Hz, 1H, CHaromatic) (keto), 8.08e8.06 (m, 1.4H, CHaromatic
(ketoþenol), 7.84e7.70 (m, 2.8H, CHaromatic) (ketoþenol), 7.59e7.58
)
(m, 2.7H, CHaromatic) (ketoþenol), 7.53e7.48 (m, 1.4H, CHaromatic
)
4.2.8. Ethyl 3-(2-(cyclohexylethynyl)quinolin-3-yl)-3-oxopropanoate
(3h). The product was obtained as a brown oil (258.6 mg, 74%);
Rf (15% ethyl acetate/hexane) 0.31; the compound was obtained as
a mixture of keto and enol forms in the ratio of 1.8:1, 1H NMR
(ketoþenol), 7.19 (s, 0.4H, CHaromatic) (enol), 6.86e6.82 (m, 2.8H,
CHaromatic) (ketoþenol), 6.34 (s, 0.4H, C]CH) (enol), 4.30e4.25 (m,
2.8H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.11 (q, J¼7.3 Hz, 2H,
CH2CH3) (keto), 3.77 (s, 4.4H, PhOCH3) (ketoþenol), 1.38 (t,
J¼6.6 Hz, 1.4H, CH2CH3) (enol), 1.13 (t, J¼7.3 Hz, 3H, CH2CH3) (keto);
(400 MHz, CDCl3) d: 12.50 (s, 0.5H, OH) (enol), 8.76e8.64 (m, 1.6H,
CHaromatic) (ketoþenol), 8.13e8.09 (m, 1.6H, CHaromatic) (ketoþenol),
7.54e7.52 (m, 1.8H, CHaromatic) (ketoþenol), 7.38e7.17 (m, 4.2H,
CHaromatic) (ketoþenol), 6.35 (s, 0.5H, C]CH) (enol), 4.34e4.29 (m,
3H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q, J¼7.3 Hz, 2H,
13C NMR (100 MHz, CDCl3)
d: 193.9, 172.9, 168.5, 167.2, 160.8, 160.6,
148.9, 147.9, 138.2, 133.95, 133.92, 133.3, 128.92, 128.83, 128.3, 127.9,
127.7, 126.2, 125.9, 114.2, 114.0, 113.5, 93.2, 87.3, 61.5, 60.5, 55.3,

9040
S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
CH2CH3) (keto), 3.55e3.50 (m,1.3H, CH) (ketoþenol), 2.05e2.02 (m,
2.2H, CH2) (ketoþenol), 1.93e1.90 (m, 2H, CH2) (ketoþenol),
1.82e1.79 (m, 1.3H, CH2) (ketoþenol), 1.65e1.56 (m, 2.2H, CH2)
(ketoþenol), 1.42e1.25 (m, 7.8H, CH2þCH2CH3) (ketoþenol),
1.24e1.18 (m, 4.1H, CH2þCH2CH3) (ketoþenol); 13C NMR (100 MHz,
Rf (15% ethyl acetate/hexane) 0.21; the compound was obtained as
a mixture of keto and enol forms in the ratio of 1.6:1, 1H NMR
(400 MHz, CDCl3)
CHaromatic
(ketoþenol), 8.12e8.10 (m, 1.6H, CHaromatic
þenol), 7.55e7.42 (m, 3.3H, CHaromatic) (ketoþenol), 7.39e7.31 (m,
1.6H, CHaromatic )
d: 12.51 (s, 0.6H, OH) (enol), 8.76e8.65 (m, 1.6H,
)
)
(keto-
CDCl3)
d
: 194.4, 172.6, 172.3, 166.9, 166.6, 149.8, 133.8, 128.3, 126.3,
)
(ketoþenol), 7.26e7.17 (m, 3.6H, CHaromatic
126.0, 125.6, 125.2, 124.7, 121.8, 121.5, 119.1, 118.8, 108.8, 100.6, 99.4,
99.2, 92.1, 61.2, 61.0, 32.2, 29.7, 25.8, 24.7, 13.9, 13.7; HRMS calcd for
(ketoþenol), 6.36 (s, 0.6H, C]CH) (enol), 4.34e4.29 (m, 3.2H, C]
OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q, J¼7.3 Hz, 2H, CH2CH3)
(keto), 2.39 (s, 4.9H, PhCH3) (ketoþenol), 1.37 (t, J¼7.3 Hz, 1.9H,
CH2CH3) (enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3) (keto); 13C NMR
C
22H23NO3 (Mþ) 349.1678; found 349.1678.
4.2.9. Ethyl 3-(2-(cyclopentylethynyl)quinolin-3-yl)-3-oxopro-
panoate (3i). The product was obtained as a brown oil (238.1 mg,
71%); Rf (15% ethyl acetate/hexane) 0.31; the compound was ob-
tained as a mixture of keto and enol forms in the ratio of 2.5:1, 1H
(100 MHz, CDCl3) d: 194.0, 172.9, 168.1, 167.1, 152.6, 150.9, 141.1,
140.2, 139.8, 137.0, 135.8, 135.5, 132.0, 131.7, 129.3, 129.2, 122.6,
122.3, 122.0, 118.9, 118.3, 96.0, 94.9, 93.1, 87.4, 87.0, 61.5, 60.6, 48.4,
21.6, 14.3, 13.9; HRMS calcd for C19H17NO3 (Mþ) 307.1208; found
307.1208.
NMR (400 MHz, CDCl3)
d: 12.58 (s, 0.4H, OH) (enol), 8. 51 (d, J¼4.2 Hz,
0.4H, CHaromatic), 8.07e8.03 (m,1.4H, CHaromatic) (ketoþenol), 7.91 (s,
1H, CHaromatic) (Keto), 7.84e7.64 (m, 3.5H, CHaromatic) (ketoþenol),
7.54e7.46 (m, 1.8H, CHaromatic) (ketoþenol), 7.28e7.25 (m, 1.4H,
CHaromatic) (ketoþenol), 6.81 (s, 0.4H, C]CH) (enol), 4.32e4.25 (m,
2.8H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q, J¼7.3 Hz, 2H,
CH2CH3) (enol), 3.87e3.79 (m, 1.3H, CH) (ketoþenol), 2.05e1.95 (m,
3H, CH2) (ketoþenol),1.80e1.77 (m, 6H, CH2) (ketoþenol),1.67e1.62
(m, 3H, CH2þCH2CH3) (ketoþenol), 1.23e1.18 (m, 6.5H) (ketoþenol,
4.2.13. Ethyl 3-(2-((3,5-dimethoxyphenyl)ethynyl) pyridin-3-yl)-3-
oxopropanoate (3m). The product was obtained as light brown
oil (257.9 mg, 73%); Rf (15% ethyl acetate/hexane) 0.18; the com-
pound was obtained as a mixture of keto and enol forms in the
ratio of 2.5:1, 1H NMR (400 MHz, CDCl3)
d
: 12.50 (s, 0.4H, OH)
(enol), 7.81e7.76 (m, 1.4H, CHaromatic) (ketoþenol), 7.62e7.55 (m,
2.8H, CHaromatic
(ketoþenol), 7.51e7.47 (m, 1.4H, CHaromatic
(ketoþenol), 7.43e7.37 (m, 2.8H, CHaromatic) (ketoþenol), 7.33e7.30
)
)
CH2þCH2CH3); 13C NMR (100 MHz, CDCl3)
d: 193.5, 172.3, 171.8,
160.5,159.2,141.9,133.7,132.9,128.3,127.6,126.8,124.7,121.5,118.8,
108.8, 102.9, 100.7, 99.4, 98.4, 70.7, 61.9, 61.8, 33.4, 30.8, 24.9, 14.1,
13.9; HRMS calcd for C21H21NO3 (Mþ) 335.1521; found 335.1521.
(m, 1.5H, CHaromatic) (ketoþenol), 7.24e7.21 (m, 1.8H, CHaromatic
)
(ketoþenol), 6.18 (s, 0.6H, C]CH) (enol), 4.27 (q, J¼7.3 Hz, 0.8H,
CH2CH3) (enol), 4.25 (s, 2H, C]OCH2C]O) (keto), 4.17 (q, J¼7.3 Hz,
2H, CH2CH3) (keto), 3.85 (s, 8.6H, PhOCH3) (ketoþenol), 1.34 (t,
J¼7.3 Hz, 1.2H, CH2CH3) (enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3)
4.2.10. Ethyl 3-(2-(hex-1-ynyl)quinolin-3-yl)-3-oxo propanoate (3j). The
product was obtained as a brown oil (239.3 mg, 74%); Rf (15% ethyl
acetate/hexane) 0.31; the compound was obtained as a mixture of keto
(keto); 13C NMR (100 MHz, CDCl3)
d: 194.4, 174.3, 171.6, 168.7,
159.7, 158.8, 150.8, 149.6, 143.0, 135.3, 134.2, 129.3, 129.13, 129.01,
125.8, 119.3, 118.6, 113.8, 113.0, 96.2, 94.9, 91.6, 85.2, 84.8, 61.2,
60.7, 55.3, 48.7, 13.8, 13.2; HRMS calcd for C20H19NO5 ([M]þ)
353.1263; found 353.1264.
and enol forms in the ratio of 2.5:1, 1H NMR (400 MHz, CDCl3)
d: 12.60
(s, 0.4H, OH) (enol), 8.58e8.27 (m, 1.3H, CHaromatic) (ketoþenol),
8.25e8.09 (m, 2.9H, CHaromatic) (ketoþenol), 8.04e7.90 (m, 3.7H, CHar-
)
(ketoþenol), 7.76e7.68 (m, 2.2H, CHaromatic
)
(ketoþenol),
omatic
7.51e7.42 (m, 0.5H, CHaromatic) (ketoþenol), 6.29 (s, 0.4H, C]CH) (enol),
4.31e4.18 (m, 3H, C]OCH2C]OþCH2CH3) (ketoþenol), 3.98e3.93 (m,
2H, CH2CH3) (keto), 2.58e2.44 (m, 3.4H, CH2) (ketoþenol), 1.76e1.60
(m, 6.6H, CH2) (ketoþenol), 1.76e160 (m, 6.6H, CH2) (ketoþenol),
1.58e1.42 (m, 2.4H, CH2) (ketoþenol), 1.35e1.10 (m, 5H, CH2þCH2CH3)
(ketoþenol), 1.00e0.92 (m, 4.9H, CH2þCH2CH3) (ketoþenol); 13C NMR
4.2.14. Ethyl
3-oxo-3-(3-(p-tolylethynyl)pyridin-4-yl)propanoate
(3n). The product was obtained as light brown oil (215.1 mg, 70%);
Rf (15% ethyl acetate/hexane) 0.22; the compound was obtained as
a mixture of keto and enol forms in the ratio of 1.7:1, 1H NMR
(400 MHz, CDCl3)
CHaromatic
(ketoþenol), 7.80e7.73 (m, 1.5H, CHaromatic) (keto-
þenol), 7.57e7.51 (m, 3.6H, CHaromatic) (ketoþenol), 7.37e7.30 (m,
1.6H, CHaromatic )
d: 12.50 (s, 0.6H, OH) (enol), 8.13e7.90 (m, 1.7H,
)
(100 MHz, CDCl3) d: 194.8, 173.2, 171.6, 168.0, 159.6, 141.8, 133.8, 129.5,
128.3, 127.1, 126.0, 124.8, 121.5, 119.3, 118.8, 108.9, 103.1, 102.8, 102.20,
102.12, 92.1, 71.0, 61.9, 61.0, 30.4, 21.9, 144.1, 13.9, 13.6; HRMS calcd for
)
(ketoþenol), 7.22e7.17 (m, 3.3H, CHaromatic
(ketoþenol), 6.36 (s, 0.6H, C]CH) (enol), 4.35e4.29 (m, 3.2H, C]
OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q, J¼7.3 Hz, 2H, CH2CH3)
(keto), 2.39 (s, 5.2H, PhCH3) (ketoþenol), 1.37 (t, J¼7.3 Hz, 1.7H,
CH2CH3) (enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3) (keto); 13C NMR
C
20H22NO3 ([MþH]þ) 324.1600; found 324.1599.
4.2.11. Ethyl 3-oxo-3-(2-(3-phenoxyprop-1-ynyl) quinolin-3-yl)
propanoate (3k). The product was obtained as brown oil
a
(100 MHz, CDCl3) d: 194.2, 173.0, 167.9, 166.9, 152.6, 151.2, 141.2,
(257.6 mg, 69%); Rf (15% ethyl acetate/hexane) 0.25; the compound
140.1, 139.8, 137.0, 136.0, 135.5, 132.0, 131.9, 131.7, 129.3, 129.2,
122.6, 122.4, 121.8, 118.9, 118.3, 95.9, 94.6, 92.9, 87.6, 87.2, 61.5,
60.5, 48.4, 21.6, 14.3, 13.9; HRMS calcd for C19H18NO3 ([MþH]þ)
308.1287; found 308.1291.
was obtained as a mixture of keto and enol forms in the ratio of
1.6:1, 1H NMR (400 MHz, CDCl3)
d: 13.26 (s, 0.7H, OH) (enol),
8.18e8.08 (m, 1.4H, CHaromatic) (ketoþenol), 8.02e7.77 (m, 4.6H)
(ketoþenol, CHaromatic), 7.71e7.38 (m, 4.7H, CHaromatic) (ketoþenol),
7.24e7.20 (m, 1.6H, CHaromatic) (ketoþenol), 6.99e6.89 (m, 4.1H,
CHaromatic) (ketoþenol), 6.19 (s, 0.7H, C]CH) (enol), 5.41 (s, 3.2H,
PhOCH2) (ketoþenol), 4.39 (q, J¼7.3 Hz, 2H, CH2CH3) (keto),
4.20e4.06 (m, 5.2H, C]OCH2C]OþCH2CH3) (ketoþenol), 1.29 (t,
J¼7.3 Hz, 2.6H, CH2CH3) (enol), 1.23e1.11 (m, 3H, CH2CH3) (keto);
4.2.15. Ethyl 3-oxo-3-(2-(phenylethynyl)phenyl) propanoate (3o). The
product was obtained as a brown oil (207.5 mg, 71%); Rf (10% ethyl
acetate/hexane) 0.35; the compound was obtained as a mixture of
keto and enol forms in the ratio of 2.5:1, 1H NMR (300 MHz, CDCl3)
d:
12.53 (s, 0.5H, OH) (enol), 7.75e7.69 (m,1.4H, CHaromatic) (ketoþenol),
7.57e7.53 (m, 1.2H, CHaromatic) (ketoþenol), 7.50e7.41 (m, 4.3H,
CHaromatic) (ketoþenol), 7.37e7.26 (m, 6.2H, CHaromatic) (ketoþenol),
6.12 (s, 0.4H, C]CH) (enol), 4.25e4.18 (m, 2.8H, C]OCH2C]
OþCH2CH3) (ketoþenol), 4.08 (q, J¼7.2 Hz, 2H, CH2CH3) (keto), 1.27
(t, J¼7.2 Hz, 1.4H, CH2CH3) (enol), 1.12 (t, J¼7.2 Hz, 3H, CH2CH3)
13C NMR (100 MHz, CDCl3)
d: 194.6, 171.8, 169.6, 167.3, 160.7, 159.7,
143.5, 140.7, 139.1, 133.2, 132.2, 132.9, 128.2, 126.6, 125.4, 125.3,
125.2, 124.78, 124.57, 123.3, 122.7, 122.4, 120.9, 119.8, 119.4, 113.8,
95.7, 82.1, 82.0, 72.4, 72.3, 61.6, 61.0, 47.6, 14.2, 13.9; HRMS calcd for
C
23H20NO4 ([MþH]þ) 374.1393; found 374.1389.
(keto); 13C NMR (75 MHz, CDCl3)
d: 194.8, 173.1, 170.4, 167.5, 139.3,
4.2.12. Ethyl
3-oxo-3-(2-(p-tolylethynyl)pyridin-3-yl)propanoate
135.4, 134.0, 131.8, 131.61, 131.53, 129.9, 129.1, 128.9, 128.60, 128.46,
128.35,128.1, 123.0, 122.5, 121.8, 121.1, 97.7, 94.8, 92.3, 88.3, 87.8, 61.3,
(3l). The product was obtained as light brown oil (224.3 mg, 73%);

S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
9041
60.3, 48.5, 14.3, 14.0; HRMS calcd for C19H16O3 (Mþ) 292.1099; found
292.1088.
(ketoþenol), 4.16 (q, J¼7.2 Hz, 2H, CH2CH3) (keto), 2.36 (s, 4.5H,
PhCH3) (ketoþenol), 1.35 (t, J¼7.2 Hz, 1.8H, CH2CH3) (enol), 1.20 (t,
J¼7.2 Hz, 3H, CH2CH3) (keto); 13C NMR (75 MHz, CDCl3)
d: 194.9,
4.2.16. Ethyl 3-oxo-3-(2-(p-tolylethynyl)phenyl) propanoate (3p).
The product was obtained as a brown oil (223.6 mg, 73%); Rf (10%
ethyl acetate/hexane) 0.33; the compound was obtained as
a mixture of keto and enol forms in the ratio of 3.3:1, 1H NMR
173.2, 170.4, 167.5, 139.3, 138.2, 135.3, 134.0, 133.7, 132.13, 132.09,
131.9, 129.95, 129.89, 129.5, 129.2, 128.9, 128.73, 128.63, 128.38,
128.26, 128.16, 122.9, 122.4, 122.0, 121.2, 96.1, 95.1, 92.2, 87.9, 61.3,
60.3, 48.6, 21.2, 14.3, 14.0; HRMS calcd for
306.1256; found 306.1259.
C
20H18O3 (Mþ)
(300 MHz, CDCl3) d: 12.50 (s, 0.3H, OH) (enol), 7.82e7.76 (m, 1.3H,
CHaromatic) (ketoþenol), 7.63e7.59 (m, 1.3H, CHaromatic) (keto-
þenol), 7.52e7.37 (m, 5.1H, CHaromatic) (ketoþenol), 7.19e7.15 (m,
4.2.20. Ethyl 3-(3-((4-methoxyphenyl)ethynyl) benzo[b]thiophen-2-
yl)-3-oxopropanoate (3t). The product was obtained as a yellow
semi solid (295.2 mg, 78%); Rf (10% ethyl acetate/hexane) 0.18;
the compound was obtained as a mixture of keto and enol forms
2.5H, CHaromatic
)
(ketoþenol), 6.22 (s, 0.3H, C]CH) (enol),
4.30e4.26 (m, 2.8H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q,
J¼7.2 Hz, 2H, CH2CH3) (keto), 2.38 (s, 3.8H, PhCH3) (ketoþenol),
1.35 (t, J¼7.2 Hz, 1.4H, CH2CH3) (enol), 1.20 (t, J¼7.2 Hz, 3H,
in the ratio of 2.5:1, 1H NMR (400 MHz, CDCl3)
d
: 13.52 (s, 0.4H,
OH) (enol), 8.12e8.07 (m, 0.9H, CHaromatic) (ketoþenol), 7.86e7.76
(m, 1.2H, CHaromatic) (ketoþenol), 7.62e7.59 (m, 2.3H, CHaromatic
CH2CH3) (keto); 13C NMR (75 MHz, CDCl3)
d: 194.9, 173.1, 170.4,
167.6, 139.3, 136.8, 133.9, 133.6, 131.9, 131.52, 131.43, 129.9, 129.25,
129.17, 128.27, 128.13, 122.1, 121.3, 120.0, 119.6, 96.1, 95.1, 92.2, 87.7,
87.7, 87.3, 61.3, 60.3, 48.6, 21.6, 14.4, 14.0; HRMS calcd for C20H18O3
(Mþ) 306.1256; found 306.1255.
)
(ketoþenol), 7.54e7.45 (m, 3.3H, CHaromatic
)
(ketoþenol),
6.96e6.88 (m, 2.8H, CHaromatic) (ketoþenol), 4.26e4.17 (m, 5.4H,
C]OCH2C]OþCH2CH3) (ketoþenol), 3.86 (s, 3H, PhOCH3) (keto),
3.83 (s, 0.8H, PhOCH3) (enol), 1.29 (t, J¼7.2 Hz, 3H, CH2CH3)
(keto), 1.20 (t, J¼7.2 Hz, 1H, CH2CH3) (enol); 13C NMR (100 MHz,
4.2.17. Ethyl 3-(2-((4-methoxyphenyl)ethynyl) phenyl)-3-oxopro-
panoate (3q). The product was obtained as
a
brown oil
CDCl3) d: 187.1, 169.7, 167.4, 160.9, 143.5, 140.5, 140.4, 133.5, 133.1,
(238.5 mg, 74%); Rf (10% ethyl acetate/hexane) 0.25; the compound
128.3, 125.41, 125.33, 125.20, 124.6, 123.3, 122.8, 122.1, 114.3,
114.0, 113.8, 101.5, 81.8, 68.2, 61.5, 61.0, 55.4, 47.6, 39.4, 14.14,
13.99; HRMS calcd for
378.0924.
was obtained as a mixture of keto and enol forms in the ratio of
2.5:1, 1H NMR (300 MHz, CDCl3)
d: 12.50 (s, 0.4H, OH) (enol),
C
22H18O4S (Mþ) 378.0926; found
7.82e7.79 (m, 1.3H, CHaromatic) (ketoþenol), 7.62e7.58 (m, 1.4H,
CHaromatic) (ketoþenol), 7.50e7.47 (m, 4.3H, CHaromatic) (ketoþenol),
7.42e7.36 (m, 2H, CHaromatic) (ketoþenol), 6.91e6.86 (m, 3.2H,
CHaromatic) (ketoþenol), 6.22 (s, 0.4H, C]CH) (enol), 4.31e4.26 (m,
2.8H, C]OCH2C]OþCH2CH3) (ketoþenol), 4.17 (q, J¼7.2 Hz, 2H,
CH2CH3) (keto), 3.84 (s, 4.5H, PhOCH3) (ketoþenol), 1.35 (t,
J¼7.2 Hz, 1.1H, CH2CH3) (enol), 1.18 (t, J¼7.2 Hz, 3H, CH2CH3) (keto);
4.3. General procedure for the silver-catalyzed formation of
the 2-carboxylate-acridinols, quinolinols, naphthlenols, and
benzothiophenol (4aet)
To a solution of CH2Cl2 (2 mL), and AgOTf (10 mol %), ortho-
alkynyl-b-keto esters (3aet) (0.5 mmol) were added and the re-
13C NMR (75 MHz, CDCl3)
d
: 194.9, 173.2, 170.5, 167.6, 160.2, 159.2,
139.1, 133.8, 133.4, 133.15, 133.01, 131.8, 129.9, 129.1, 128.1, 127.9,
122.3, 114.6, 114.12, 114.01, 96.1, 95.1, 92.1, 87.2, 86.8, 61.2, 60.3, 55.3,
48.6, 14.3, 14.0; HRMS calcd for C20H18O4 (Mþ) 322.1205; found
322.1207.
action mixture was allowed to stir at 25 ꢀC for 3e5 h. The com-
pletion of reaction was monitored by TLC. The reaction mixture was
filtered and diluted with ethyl acetate and washed with brine so-
lution. The combined organic fractions were dried over anhydrous
Na2SO4 and concentrated under vacuum to yield the crude product.
The crude product was purified by column chromatography on
silica gel using ethyl acetate/hexane as the eluent.
4.2.18. Ethyl 3-oxo-3-(2-(thiophen-3-ylethynyl) phenyl)propanoate
(3r). The product was obtained as a brown oil (226.7 mg, 76%); Rf
(10% ethyl acetate/hexane) 0.33; the compound was obtained as
a mixture of keto and enol forms in the ratio of 2.5:1, 1H NMR
4.3.1. Ethyl 1-hydroxy-3-phenylacridine-2-carboxylate (4a). The
product was obtained as brown crystals in hexane/CH2Cl2
(128.7 mg, 75%); mp 140e144 ꢀC; Rf (10% ethyl acetate/hexane)
(400 MHz, CDCl3)
d
: 12.50 (s, 0.4H, OH) (enol), 8.59 (d, J¼7.2 Hz,
1H, CHaromatic) (keto), 8.14 (t, J¼7.2 Hz, 1H, CHaromatic) (keto),
7.92e7.72 (m, 3.2H, CHaromatic) (ketoþenol), 7.66e7.61 (m, 5H,
0.46; 1H NMR (400 MHz, CDCl3)
d: 12.67 (s, 1H, OH), 9.30 (s, 1H,
CHaromatic
)
(ketoþenol), 7.26 (s, 1.6H, CHaromatic
)
(ketoþenol),
CHaromatic), 8.12 (d, J¼8.8 Hz, 1H, CHaromatic), 8.02 (d, J¼8.8 Hz, 1H,
CHaromatic), 7.77 (t, J¼7.3 Hz, 1H, CHaromatic), 7.52e7.48 (m, 2H,
CHaromatic), 7.33e7.28 (m, 5H, CHaromatic), 3.99 (q, J¼6.6 Hz, 2H,
CH2CH3), 0.73 (t, J¼6.6 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
6.94e6.90 (m, 3.9H, CHaromatic) (ketoþenol), 6.41 (s, 0.4H, C]CH)
(enol), 4.37e4.33 (m, 3.0H, C]OCH2C]OþCH2CH3) (ketoþenol),
4.18 (q, J¼7.3 Hz, 2H, CH2CH3) (keto), 1.38 (t, J¼7.3 Hz, 1.5H,
CH2CH3) (enol), 1.20 (t, J¼7.3 Hz, 3H, CH2CH3) (keto); 13C NMR
d: 171.5, 162.6, 150.9, 149.6, 143.4, 142.9, 134.2, 131.9, 129.1, 128.2,
(100 MHz, CDCl3)
d
: 194.7, 173.1, 170.4, 167.5, 139.1, 135.2, 133.9,
127.6, 126.8, 126.0, 125.9, 122.4, 118.7, 104.5, 61.2, 12.9; HRMS calcd
133.4, 131.8, 129.9, 125.6, 129.16, 128.96, 128.34, 128.21, 128.13,
125.6, 125.4, 122.1, 121.9, 121.6, 121.1, 92.1, 91.1, 90.2, 87.8, 87.4, 61.3,
60.3, 48.5, 14.3, 13.9; HRMS calcd for C17H14O3S (Mþ) 298.0664;
found 298.0668.
for C22H18NO3 ([MþH]þ) 344.1287; found 344.1285. IR
n )
(cmꢁ1
(liquid film): 2920, 2850, 1654, 1514, 1463, 1401, 1375, 1324, 1260,
1161, 1097, 1019, 800.
4.3.2. Ethyl 1-hydroxy-3-p-tolylacridine-2-carboxylate (4b). The
product was obtained as light yellow crystalline solid from hexane/
CH2Cl2 (141.2 mg, 79%); mp 155e157 ꢀC; Rf (10% ethyl acetate/
4.2.19. Ethyl 3-oxo-3-(2-(m-tolylethynyl)phenyl) propanoate (3s).
The product was obtained as a brown oil (220.5 mg, 72%); Rf (10%
ethyl acetate/hexane) 0.31; the compound was obtained as
a mixture of keto and enol forms in the ratio of 1.8:1, 1H NMR
hexane) 0.41; 1H NMR (400 MHz, CDCl3)
d: 12.19 (s, 1H, OH), 9.32 (S,
1H, CHaromatic), 8.20 (d, J¼6.88 Hz, 1H, CHaromatic), 8.00 (d, J¼8.2 Hz,
1H, CHaromatic), 7.81e7.77 (M,1H, CHaromatic), 7.56 (M,1H, CHaromatic),
7.53e7.49 (M, 1H, CHaromatic), 7.19 (d, J¼8.7 Hz, 2H, CHaromatic), 7.13
(d, J¼6.9 Hz, 2H, CHaromatic), 4.02 (q, J¼6.4 Hz, 2H, CH2CH3), 2.35 (s,
3H, PhCH3), 0.75 (t, J¼7.2 Hz, 3H, CH2CH3); 13C NMR (100 MHz,
(300 MHz, CDCl3) d: 12.53 (s, 0.5H, OH) (enol), 7.82e7.77 (m, 1.4H,
CHaromatic) (ketoþenol), 7.64e7.59 (m, 1.5H, CHaromatic) (keto-
þenol), 7.50e7.48 (m, 1H, CHaromatic) (keto), 7.44e7.36 (m, 4.8H,
CHaromatic) (ketoþenol), 7.29e7.22 (m, 1.8H, CHaromatic) (keto-
þenol), 7.20e7.15 (m, 1.5H, CHaromatic) (ketoþenol), 6.22 (s, 0.5H,
C]CH) (enol), 4.33e4.26 (m, 2.9H, C]OCH2C]OþCH2CH3)
CDCl3) d: 171.5, 162.4, 149.8, 148.4, 144.5, 139.6, 136.7, 135.2, 132.5,
129.2, 128.3, 128.1, 126.1, 125.8, 121.5, 118.6, 104.9, 61.4, 21.8, 13.0;

9042
S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
HRMS calcd C23H20NO3 (Mþ) 357.1365; found 357.1366. IR
n
(cmꢁ1
)
419.1521. IR n
(cmꢁ1) (liquid film): 2923, 2852, 1615, 1373, 1269,
(liquid film): 3075, 2981, 2927, 2855, 1633, 1619, 1561, 1513, 1495,
1102, 1019, 845, 754, 694.
1444, 1374, 1263, 1068, 960, 822, 703, 677, 624.
4.3.6. Ethyl 1-hydroxy-3-(4-(trifluoromethyl) phenyl)acridine-2-
carboxylate (4f). The product was obtained as yellow crystals in
hexane/CH2Cl2 (131.7 mg, 64%); mp 173e175 ꢀC; Rf (10% ethyl
4.3.3. Ethyl 3-(4-ethylphenyl)-1-hydroxyacridine-2-carboxylate
(4c). The product was obtained as brown crystals in hexane/
CH2Cl2 (144.7 mg, 78%); mp 138e141 ꢀC; Rf (10% ethyl acetate/
acetate/hexane) 0.37; 1H NMR (400 MHz, CDCl3)
d: 12.89 (s, 1H,
hexane) 0.43; 1H NMR (400 MHz, CDCl3)
d: 12.60 (s, 1H, OH), 9.29
OH), 9.33 (s, 1H, CHaromatic), 8.17 (d, J¼8.8 Hz, 1H, CHaromatic), 8.03
(d, J¼8.1 Hz, 1H, CHaromatic), 7.85e7.81 (m, 1H, CHaromatic), 7.66 (d,
J¼8.0 Hz, 2H, CHaromatic), 7.58e7.54 (m, 1H, CHaromatic), 7.52 (s, 1H,
CHaromatic), 7.48 (d, J¼8.0 Hz, 2H, CHaromatic), 4.05 (q, J¼7.3 Hz, 2H,
CH2CH3), 0.77 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz,
(s, 1H, CHaromatic), 8.12 (d, J¼8.8 Hz, 1H, CHaromatic), 8.00 (d,
J¼8.1 Hz, 1H, CHaromatic), 7.78e7.74 (m, 1H, CHaromatic), 7.52e7.49
(m, 2H, CHaromatic), 7.22 (d, J¼8.1 Hz, 2H, CHaromatic), 7.15 (d,
J¼8.1 Hz, 2H, CHaromatic), 4.09 (q, J¼7.3 Hz, 2H, CH2CH3), 2.64 (q,
J¼7.0 Hz, 2H, CH2CH3), 1.22 (t, J¼7.3 Hz, 3H, CH2CH3), 0.73 (t,
CDCl3) d: 171.1, 163.1, 150.9, 149.3, 146.6, 141.7, 134.3, 132.1, 129.13,
J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d
: 171.6, 162.5,
129.09, 128.5, 126.2, 126.1, 124.51, 124.47, 124.43, 122.5, 118.8,
150.9, 149.7, 143.5, 143.0, 140.0, 134.2, 131.8, 129.2, 128.2, 127.1,
126.0, 125.8, 122.3, 118.7, 104.7, 61.2, 28.6, 15.9, 12.9; HRMS calcd
103.7, 61.4, 12.8; HRMS calcd for C23H16F3NO3 (Mþ) 411.1082;
found 411.1082. IR
n
(cmꢁ1) (KBr): 2924, 1653, 1615, 1513, 1371,
for C24H22NO3 ([MþH]þ) 372.1600; found 372.1589. IR
n
(cmꢁ1
)
1337, 1311, 1240, 1101, 962, 877, 748, 588, 536. Crystallographic
data for 4f have been deposited with the Cambridge Crystallo-
graphic Data Centre. CCDC 864805, contain all crystallographic
details of this publication and is available free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html or can be ordered
from the following address: Cambridge Crystallographic Data
Centre, 12 Union Road, GB-Cambridge CB21EZ; fax: (þ44)1223-
336-033; or email: deposit@ccdc.cam.ac.uk.
(liquid film): 2925, 2853, 1617, 1515, 1440, 1396, 1338, 1263, 1180,
1100, 963, 807, 747.
4.3.4. Ethyl 1-hydroxy-3-(4-methoxyphenyl)acridine-2-carboxylate
(4d). The product was obtained as brown crystals in hexane/
CH2Cl2 (154.9 mg, 83%); mp 170e172 ꢀC; Rf (10% ethyl acetate/
hexane) 0.23; 1H NMR (400 MHz, CDCl3)
d: 12.61 (s,1H, OH), 9.28 (s,
1H, CHaromatic), 8.11 (d, J¼8.8 Hz, 1H, CHaromatic), 7.99 (d, J¼8.0 Hz,
1H, CHaromatic), 7.76 (t, J¼8.1 Hz, 1H, CHaromatic) 7.50e7.46 (m, 2H,
CHaromatic), 7.23 (d, J¼8.8 Hz, 2H, CHaromatic), 6.87 (d, J¼8.8 Hz, 2H,
CHaromatic), 4.02 (q, J¼7.3 Hz, 2H, CH2CH3), 3.80 (s, 3H, PhOCH3),
4.3.7. Ethyl 1-hydroxy-3-(thiophen-3-yl)acridine-2-carboxylate
(4g). The product was obtained as brown crystals in hexane/
CH2Cl2 (143.2 mg, 82%); mp 147e150 ꢀC; Rf (10% ethyl acetate/
0.81 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 171.6,
hexane) 0.46; 1H NMR (400 MHz, CDCl3)
d: 12.69 (s,1H, OH), 9.28 (s,
162.5, 158.8, 150.8, 149.6, 143.1, 135.3, 134.2, 131.9, 129.31, 129.13,
129.01, 125.96, 125.81, 122.2, 118.6, 113.0, 104.7, 61.3, 55.3, 13.2;
1H, CHaromatic), 8.11 (d, J¼8.8 Hz, 1H, CHaromatic), 7.99 (d, J¼8.1 Hz,
1H, CHaromatic), 7.76 (t, J¼7.3 Hz, 1H, CHaromatic), 7.56 (s, 1H, CHar-
omatic), 7.49 (t, J¼7.3 Hz,1H, CHaromatic), 7.24e7.21 (m, 2H, CHaromatic),
7.02 (d, J¼5.9 Hz, 1H, CHaromatic) 4.07 (q, J¼7.3 Hz, 2H, CH2CH3), 0.91
HRMS calcd C23H20NO4 ([MþH]þ) 374.1393; found 374.1395. IR
n
(cmꢁ1) (liquid film): 2924, 2853, 1617, 1512, 1441, 1374, 1339, 1232,
1264, 1181, 1101, 1019, 961, 810, 748, 698.
(t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 171.5, 162.6,
150.9, 149.6, 142.9, 138.0, 134.2, 131.9, 129.17, 129.12, 128.98, 126.07,
125.96, 124.1, 122.5, 121.5, 118.8, 104.5, 61.4, 13.2; HRMS calcd for
4.3.4.1. Procedure for the silver-catalyzed formation of compound
(5þ6). To a solution of CDCl3 (2 mL), and AgOTf (10 mol %), ethyl
3-(2-((4-methoxyphenyl)ethynyl)quinolin-3-yl)-3-oxopropanoate
(3d) (0.5 mmol) was added followed by 10 equiv of CD3OD and
reaction mixture was allowed to stir at 25 ꢀC for 5 h and the
resulting solution was filtered and washed with D2O and
extracted with ethyl acetate (3ꢂ10 mL). The combined organic
fractions was dried over anhydrous Na2SO4 and concentrated
under vacuum to yield the crude product. The crude product was
purified by column chromatography on silica gel using ethyl ac-
etate/hexane as the eluent. The product was obtained as brown
crystals in hexane/CH2Cl2; mp 175e176 ꢀC; Rf (10% ethyl acetate/
C
20H15NO3S (Mþ) 349.0773; found 349.0779. IR (cmꢁ1) (liquid
n
film): 3060, 2920, 2850, 2658, 1723, 1614, 1574, 1514, 1372, 1251,
1131, 1016, 857, 757, 691, 660.
4.3.8. Ethyl 3-cyclohexyl-1-hydroxyacridine-2-carboxylate (4h). The
product was obtained as green needle crystals in hexane/CH2Cl2
(122.3 mg, 70%); mp 80e85 ꢀC; Rf (10% ethyl acetate/hexane) 0.44;
1H NMR (400 MHz, CDCl3)
d: 13.06 (s, 1H, OH), 9.31 (s, 1H, CHar-
omatic), 8.15 (d, J¼8.8 Hz, 1H, CHaromatic), 8.04 (d, J¼8.1 Hz, 1H,
CHaromatic), 7.84e7.80 (m, 1H, CHaromatic), 7.62 (s, 1H, CHaromatic),
7.55e7.51 (m, 1H, CHaromatic), 4.53 (q, J¼6.6 Hz, 2H, CH2CH3),
3.57e3.49 (m, 1H, CH), 2.50e2.02 (m, 2H, CH2), 1.93e1.90 (m, 2H,
CH2), 1.82e1.79 (m, 1H, CH2), 1.56e1.40 (m, 5H, CH2), 1.36e1.24 (m,
hexane) 0.24; 1H NMR (400 MHz, CDCl3)
d: 9.36 (s, 1H, CHaromatic),
8.22 (d, J¼8.4 Hz, 1H, CHaromatic), 8.05 (d, J¼8.1 Hz, 1H, CHaromatic),
7.83 (t, J¼7.3 Hz, 1H, CHaromatic), 7.60 (s, 0.4H, CHaromatic), 7.55 (t,
J¼7.3 Hz, 1H, CHaromatic), 7.28 (d, J¼8.0 Hz, 2H, CHaromatic), 6.82 (d,
J¼8.8 Hz, 2H, CHaromatic), 4.08 (q, J¼6.6 Hz, 2H, CH2CH3), 3.85 (s,
3H, PhOCH3), 0.86 (t, J¼7.3 Hz, 3H, CH2CH3).
3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 172.3,164.4, 142.4,139.1,
136.1, 132.8, 130.9, 129.5, 128.8, 128.0, 127.1, 125.5, 118.4, 106.1, 62.0,
48.0, 34.3, 29.7, 25.0, 14.4. HRMS calcd for C22H23NO3 (Mþ)
349.1678; found 349.1675. IR
n
(cmꢁ1) (liquid film): 2957, 2922,
2852, 1731, 1634, 1608, 1515, 1402, 1379, 1326, 1179, 1112, 1016, 956,
853, 832, 772, 617.
4.3.5. Ethyl 3-(biphenyl-4-yl)-1-hydroxyacridine-2-carboxylate
(4e). The product was obtained as brown crystals in hexane/
CH2Cl2 (159.4 mg, 76%); mp 173e175 ꢀC; Rf (10% ethyl acetate/
4.3.9. Ethyl 3-cyclopentyl-1-hydroxyacridine-2-carboxylate
(4i). The product was obtained as green needle crystals in hex-
ane/CH2Cl2 (120.7 mg, 72%); mp 87e88 ꢀC; Rf (10% ethyl acetate/
hexane) 0.30; 1H NMR (400 MHz, CDCl3)
d: 12.69 (s,1H, OH), 9.31 (s,
1H, CHaromatic), 8.13 (d, J¼8.8 Hz, 1H, CHaromatic), 8.00 (d, J¼8.8 Hz,
1H, CHaromatic), 7.79e7.75 (m, 1H, CHaromatic), 7.60e7.56 (m, 5H,
CHaromatic), 7.49 (t, J¼7.3 Hz, 1H, CHaromatic), 7.42e7.37 (m, 4H,
CHaromatic), 7.30 (t, J¼7.3 Hz, 1H, CHaromatic), 4.01 (q, J¼7.3 Hz, 2H,
CH2CH3), 0.74 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
hexane) 0.44; 1H NMR (400 MHz, CDCl3)
d: 12.86 (s,1H, OH), 9.23 (s,
1H, CHaromatic), 8.11 (d, J¼8.7 Hz, 1H, CHaromatic), 7.94 (d, J¼8.1 Hz,
1H, CHaromatic), 7.74 (t, J¼7.7 Hz, 1H, CHaromatic), 7.55 (s, 1H, CHar-
omatic), 7.44 (t, J¼7.3 Hz, 1H, CHaromatic), 4.44 (q, J¼7.3 Hz, 2H,
CH2CH3), 3.46e3.41 (m, 1H, CH), 1.95e1.92 (m, 2H, CH2), 1.84e1.81
(m, 2H, CH2), 1.73e1.70 (m, 1H, CH2), 1.48e1.22 (m, 6H,
d: 171.5, 162.7, 149.6, 143.0, 141.9, 140.8, 139.8, 134.3, 131.9, 129.16,
129.07, 128.8, 128.6, 127.3, 127.0, 126.3, 126.0, 125.9, 122.3, 118.7,
104.5, 61.0, 14.1; HRMS calcd for C28H21NO3 (Mþ) 419.1521; found
CH2þCH2CH3); 13C NMR (100 MHz, CDCl3)
d: 172.3, 162.9, 150.1,

S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
9043
147.8, 139.5, 134.3, 131.8, 129.7, 129.2, 128.8, 125.5, 117.3, 105.5,
103.4, 61.2, 43.8, 34.2, 25.0, 13.9; HRMS calcd for C21H22NO3
J¼2.9 Hz, 1H, CHaromatic), 7.70 (d, J¼8.0 Hz, 1H, CHaromatic), 7.44e7.41
(m, 2H, CHaromatic), 7.24e7.18 (m, 4H, CHaromatic), 4.06 (q, J¼7.3 Hz,
([MþH]þ) 336.1600; found 336.1589. IR
n
(cmꢁ1) (liquid film): 2961,
2H, CH2CH3), 2.42 (s, 3H, PhCH3), 0.81 (t, J¼7.3 Hz, 3H, CH2CH3); 13
C
2924, 2855, 1716, 1633, 1615, 1558, 1511, 1463, 1337, 1374, 1262,
1099, 1019, 861, 844, 796, 750, 628.
NMR (100 MHz, CDCl3) d: 171.5, 160.9, 153.7, 149.9, 143.6, 140.1,
136.7, 131.9, 128.2, 128.1, 122.5, 120.6, 119.2, 106.5, 61.7, 20.6, 11.9;
HRMS calcd C19H17NO3 (Mþ) 307.1208; found 307.1205. IR (cmꢁ1
n
)
4.3.10. Ethyl 3-butyl-1-hydroxyacridine-2-carboxylate (4j). The
product was obtained as greenish yellow needle crystals in hexane/
CH2Cl2 (113.2 mg, 70%); mp 100e103 ꢀC; Rf (10% ethyl acetate/
(liquid film): 2925, 2852, 1733, 1630, 1615, 1515, 1445, 1372, 1266,
1243, 1101, 1020, 963, 831, 749.
hexane) 0.38; 1H NMR (400 MHz, CDCl3)
d: 13.33 (s, 1H, OH), 9.31 (s,
4.3.15. Ethyl 1-hydroxy-3-phenyl-2-naphthoate (4o). The product
was obtained as light yellow semi solid (102.3 mg, 70%); Rf (5% ethyl
1H, CHaromatic), 8.16 (d, J¼8.8 Hz, 1H, CHaromatic), 8.03 (d, J¼8.1 Hz,
1H, CHaromatic), 7.84e7.80 (m, 1H, CHaromatic), 7.53 (t, J¼7.3 Hz, 1H,
CHaromatic), 7.49 (s, 1H, CHaromatic), 4.52 (q, J¼7.3 Hz, 2H, CH2CH3),
3.12 (t, J¼7.3 Hz, 2H, CH2), 1.70e1.62 (m, 2H, CH2), 1.50e1.41 (m, 5H,
CH2þCH2CH3), 0.96 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz,
acetate/hexane) 0.78; 1H NMR (400 MHz, CDCl3)
d: 12.27 (s, 1H,
OH), 8.17 (d, J¼8.8 Hz, 1H, CHaromatic), 8.00 (d, J¼8.8 Hz, 1H, CHar-
omatic), 7.78 (t, J¼8.0 Hz, 1H, CHaromatic), 7.50 (t, J¼7.3 Hz, 1H, CHar-
omatic), 7.36e7.29 (m, 5H, CHaromatic), 7.19 (s, 1H, CHaromatic), 3,98 (q,
J¼7.3 Hz, 2H, CH2CH3), 0.72 (t, J¼6.6 Hz, 3H, CH2CH3); 13C NMR
CDCl3) d: 172.4, 164.0, 150.8, 150.0, 144.3, 134.4, 131.8, 129.2, 128.9,
125.8, 125.5, 121.1, 118.5, 104.3, 61.9, 37.1, 33.7, 22.8, 14.10, 14.06;
(100 MHz, CDCl3) d: 171.8, 161.1, 140.6, 139.4, 136.1, 135.5, 129.7,
HRMS calcd for C20H22NO3 ([MþH]þ) 324.1600; found 324.1598. IR
128.3, 128.1, 127.3, 125.6, 123.94, 123.89, 121.2, 106.1, 61.0, 13.0;
n
(cmꢁ1) (liquid film): 2952, 2924, 2858, 1630, 1615, 1458, 1371,
HRMS calcd C19H16O3 (Mþ) 292.1099; found 292.1089. IR (cmꢁ1
n )
1338, 1264, 1107, 818, 744.
(liquid film): 2923, 2852, 1630, 1457, 1258, 1018, 751.
4.3.11. Ethyl 1-hydroxy-3-(phenoxymethyl)acridine-2-carboxylate
(4k). The product was obtained as green semi solid (128.8 mg,
69%); Rf (10% ethyl acetate/hexane) 0.25; 1H NMR (400 MHz, CDCl3)
4.3.16. Ethyl 1-hydroxy-3-p-tolyl-2-naphthoate (4p). The product
was obtained as white crystals in hexane/CH2Cl2 (113.3 mg, 74%);
mp 114e116 ꢀC; Rf (5% ethyl acetate/hexane) 0.72; 1H NMR
d
: 13.32 (s, 1H, OH), 9.37 (s, 1H, CHaromatic), 8.21 (d, J¼8.8 Hz, 1H,
(300 MHz, CDCl3)
d
: 12.21 (s, 1H, OH), 8.41 (d, J¼7.8 Hz, 1H, CHar-
CHaromatic), 8.07 (d, J¼8.8 Hz, 1H, CHaromatic), 7.96 (s, 1H, CHaromatic),
7.85 (t, J¼7.3 Hz, 1H, CHaromatic), 7.57 (t, J¼7.7 Hz, 1H, CHaromatic),
7.33e7.29 (m, 2H, CHaromatic), 7.03e6.96 (m, 3H, CHaromatic), 5.48 (s,
2H, CH2OPh), 4.04 (q, J¼7.3 Hz, 2H, CH2CH3), 1.36 (t, J¼7.3 Hz, 3H,
omatic), 7.72 (d, J¼7.2 Hz, 1H, CHaromatic), 7.60e7.58 (m, 1H, CHar-
omatic), 7.54e7.49 (m, 2H, CHaromatic), 7.36e7.19 (m, 4H, CHaromatic),
4.04 (q, J¼6.9 Hz, 2H, CH2CH3), 2.41 (s, 3H, PhCH3), 0.79 (t, J¼7.2 Hz,
3H, CH2CH3); 13C NMR (75 MHz, CDCl3)
d: 171.8, 161.1, 140.6, 139.4,
CH2CH3); 13C NMR (100 MHz, CDCl3)
d
: 171.8, 169.7, 164.2, 158.7,
136.1, 135.5, 131.8, 129.6, 128.8, 128.1, 127.3, 125.6, 123.9, 121.1, 106.1,
143.2, 140.0, 137.8, 135.4, 134.6, 132.2, 129.5, 129.1, 126.1, 120.9,
119.5, 119.0, 114.7, 102.8, 68.2, 61.0, 14.1; HRMS calcd for C23H19NO4
61.0, 21.1, 13.0; HRMS calcd C20H18O3 (Mþ) 306.1256; found
306.1251. IR
n
(cmꢁ1) (liquid film): 2924, 2854, 1731, 1660, 1651,
(Mþ) 373.1314; found 373.1314. IR
n
(cmꢁ1) (KBr): 2984, 2931, 1655,
1608, 1514, 1373, 1305, 1261, 1108, 1020, 831, 805, 733. Crystallo-
graphic data for 4p have been deposited with the Cambridge
Crystallographic Data Centre. CCDC 847471, contain all crystallo-
graphic details of this publication and is available free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html or can be ordered from
the following address: Cambridge Crystallographic Data Centre, 12
Union Road, GB-Cambridge CB21EZ; fax: (þ44)1223-336-033; or
email: deposit@ccdc.cam.ac.uk.
1631, 1617, 1229, 1509, 1371, 1327, 1280, 1161, 1116, 849, 754, 637.
4.3.12. Ethyl 5-hydroxy-7-p-tolylquinoline-6-carboxylate (4l). The
product was obtained as brown needle crystals in hexane/CH2Cl2
(121.4 mg, 79%); mp 107e110 ꢀC; Rf (10% ethyl acetate/hexane)
0.25; 1H NMR (400 MHz, CDCl3)
d: 12.19 (s, 1H, OH), 8.98 (dd, J¼1.5,
4.4 Hz, 1H, CHaromatic), 8.72e8.70 (m, 1H, CHaromatic), 7.48 (s, 1H,
CHaromatic), 7.44e7.40 (m, 1H, CHaromatic), 7.23e7.18 (m, 4H, CHar-
omatic), 4.03 (q, J¼7.3 Hz, 2H, CH2CH3), 2.36 (s. 3H, PhCH3), 0.81 (t,
4.3.17. Ethyl 1-hydroxy-3-(4-methoxyphenyl)-2-naphthoate (4q).
The product was obtained as white crystals in hexane/CH2Cl2
(127.3 mg, 79%); mp 127e129 ꢀC; Rf (5% ethyl acetate/hexane) 0.52;
J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 171.4, 160.8,
153.5, 149.9, 143.3, 139.8, 136.5, 132.4, 128.26, 128.16, 122.5, 120.6,
119.2, 106.8, 61.3, 21.2, 13.0; HRMS calcd for C19H17NO3 (Mþ)
1H NMR (300 MHz, CDCl3)
d: 12.16 (s, 1H, OH), 8.33 (d, J¼8.1 Hz, 1H,
307.1208; found 307.1208. IR
1515, 1374, 1321, 1258, 1155, 1094, 1020, 799, 614.
n
(cmꢁ1) (liquid film): 2926, 1645,
CHaromatic), 7.64 (d, J¼7.8 Hz, 1H, CHaromatic), 7.53 (t, J¼6.9 Hz, 2H,
CHaromatic), 7.46e7.41 (m, 1H, CHaromatic), 7.18e7.14 (m, 2H, CHar-
omatic), 6.84 (d, J¼8.4 Hz, 2H, CHaromatic), 3.98 (q, J¼7.2 Hz, 2H,
CH2CH3), 3.79 (s, 3H, PhOCH3), 0.77 (t, J¼7.2 Hz, 3H, CH2CH3); 13C
4.3.13. Ethyl 7-(3,5-dimethoxyphenyl)-5-hydroxy quinoline-6-
carboxylate (4m). The product was obtained as light yellow crys-
tals in hexane/CH2Cl2 (127.2 mg, 72%); mp 260e265 ꢀC; Rf (10%
NMR (75 MHz, CDCl3) d: 170.8, 160.2, 157.5, 137.9, 135.1, 134.4, 128.6,
128.4, 126.2, 124.6, 122.8, 120.2, 111.9, 105.1, 60.0, 54.4, 12.2; HRMS
ethyl acetate/hexane) 0.10; 1H NMR (400 MHz, CDCl3)
d: 12.16 (s,
calcd C20H18O4 (Mþ) 322.1205; found 322.1205. IR (cmꢁ1) (liquid
n
1H, OH), 8.92 (dd, J¼1.4, 2.2 Hz, 1H, CHaromatic), 8.65 (dd, J¼1.4,
8.8 Hz, 1H, CHaromatic), 7.44 (s, 1H, CHaromatic), 7.39e7.35 (m, 1H,
CHaromatic), 6.43e6.37 (m, 3H, CHaromatic), 4.04 (q, J¼7.3 Hz, 2H,
CH2CH3), 3.74 (s, 6H, PhOCH3), 1.18 (t, J¼7.3 Hz, 3H, CH2CH3); 13C
film): 2924, 2851, 1629, 1401, 1326, 1280, 1242, 1179, 1111, 1016,
822, 772.
4.3.18. Ethyl 1-hydroxy-3-(thiophen-3-yl)-2-naphthoate (4r). The
product was obtained as yellow crystals in hexane/CH2Cl2
(119.3 mg, 80%); mp 90e94 ꢀC; Rf (5% ethyl acetate/hexane) 0.76; 1H
NMR (100 MHz, CDCl3) d: 171.2, 160.8, 160.1, 153.5, 149.8, 144.6,
143.1, 138.5, 132.5, 122.1, 120.8, 119.4, 106.7, 99.2, 61.3, 60.4, 55.4,
14.1; HRMS calcd for C20H19NO5 (Mþ) 353.1263; found 353.1268. IR
NMR (400 MHz, CDCl3)
d
: 12.25 (s, 1H, OH), 8.34 (d, J¼8.1 Hz, 1H,
n
(cmꢁ1) (liquid film): 2922, 2852, 1636, 1401, 1326, 1280, 1242,
CHaromatic), 7.64 (d, J¼8.1 Hz, 1H, CHaromatic), 7.55e7.51 (m, 1H,
CHaromatic), 7.46e7.42 (m, 1H, CHaromatic), 7.21e7.19 (m, 1H, CHar-
omatic), 7.17 (s, 1H, CHaromatic), 7.11e7.09 (m, 1H, CHaromatic), 6.96 (d,
J¼5.9 Hz, 1H, CHaromatic), 4.04 (q, J¼7.3 Hz, 2H, CH2CH3), 0.89 (t,
1179, 1111, 1016, 832, 722.
4.3.14. Ethyl 5-hydroxy-7-p-tolylisoquinoline-6-carboxylate (4n).
The product was obtained as yellow needle crystals in hexane/
CH2Cl2 (112.2 mg, 73%); 110e112 mp ꢀC; Rf (10% ethyl acetate/
J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 171.7, 161.3,
143.6, 135.5, 133.9, 129.7, 129.3, 127.2, 125.8, 124.2, 123.93, 123.81,
hexane) 0.28; 1H NMR (400 MHz, CDCl3)
d: 12.22 (s,1H, OH), 7.97 (d,
121.4, 120.9, 106.0, 61.1, 13.1; HRMS calcd C17H14O3S ([M ꢁ H]þ)

9044
S.P. Shukla et al. / Tetrahedron 68 (2012) 9035e9044
Tetrahedron 2011, 67, 6057e6064; (i) Yamamoto, Y.; Noda, M.; Ohno, M.; Eguchi,
297.0650; found 297.0625. IR
n
(cmꢁ1) (liquid film): 3109, 2923,
S. J. Org. Chem. 1997, 62, 1292e1298; (j) Patil, N. T.; Yamamoto, Y. J. Org. Chem.
2004, 69, 6478e6481; (k) Inga, C. Tetrahedron Lett. 2009, 50, 2570e2572; (l)
Ackermann, L. Org. Lett. 2005, 7, 439e442; (m) Rodriguez, A. L.; Koradin, C.;
Dohle, W.; Knochel, P. Angew. Chem., Int. Ed. 2000, 39, 2488e2490; (n) Worlikar,
S. A.; Kesharwani, T.; Yao, T.; Larock, R. C. J. Org. Chem. 2007, 72, 1347e1353; (o)
Yao, T.; Campo, M. A.; Larock, R. C. Org. Lett. 2004, 6, 2677e2680; (p) Yao, T.;
Larock, R. C. J. Org. Chem. 2005, 70, 1432e1437; (q) Zhao, L.; Xie, F.; Cheng, G.;
Hu, Y. Angew. Chem., Int. Ed. 2009, 48, 6520e6523.
2853, 1636, 1441, 1402, 1369, 1274, 1168, 1102, 1013, 834, 807,
770, 670.
4.3.19. Ethyl 1-hydroxy-3-m-tolyl-2-naphthoate (4s). The product
was obtained as white needle crystals in hexane/CH2Cl2 (105.7 mg,
69%); mp 109e111 ꢀC; Rf (5% ethyl acetate/hexane) 0.74; 1H NMR
2. (a) Weibel, J. M.; Blanc, A.; Pale, P. Chem. Rev. 2008, 108, 3149e3173; (b)
Corral, M. A.; Dorado, M. M.; Garcia, I. R. Chem. Rev. 2008, 108, 3174e3198;
(c) Yu, X.; Ye, S.; Wu, J. Adv. Synth. Catal. 2010, 352, 2050e2056; (d) Ding, Q.;
Wu, J. Org. Lett. 2007, 9, 4959e4962; (e) Chen, Z.; Yang, X.; Wu, J. Chem.
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Belmont, P. Chem.dEur. J. 2007, 13, 5632e5641; (g) Godet, T.; Bosson, J.;
Belmont, P. Synlett 2005, 2786e2790; (h) Parker, E.; Leconte, N.; Godet, T.;
Belmont, P. Chem. Commun. 2011, 343e345; (i) Belmont, P.; Parker, E. Eur. J.
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3. (a) Oppegard, L. M.; Ougolkov, A. V.; Luchini, D. N.; Schoon, R. A.; Goodell, J. R.;
Kaur, H.; Billadeau, D. D.; Ferguson, D. M.; Hiasa, H. Eur. J. Pharmacol. 2009, 602,
223e229; (b) Goodell, J. R.; Ougolkov, A. V.; Hiasa, H.; Kaur, H.; Remmel, R.;
Billadeau, D. D.; Ferguson, D. M. J. Med. Chem. 2008, 51, 179e182; (c) Kapuriya,
N.; Kapuriya, K.; Zhang, X.; Chou, T. C.; Kakadiya, R.; Wu, Y. T.; Tsai, T. H.; Chen,
Y. T.; Lee, T. C.; Shah, A.; Naliapara, Y.; Su, T. L. Bioorg. Med. Chem. 2008, 16,
5413e5423; (d) Nelson, E. M.; Tewey, K. M.; Liu, L. F. Proc. Natl. Acad. Sci. U.S.A.
1984, 81, 1361e1365.
(400 MHz, CDCl3)
d
: 12.24 (s, 1H, OH), 8.42 (d, J¼8.1 Hz, 1H, CHar-
omatic), 7.72 (d, J¼8.1 Hz, 1H, CHaromatic), 7.60 (t, J¼6.6 Hz, 1H, CHar-
omatic), 7.51 (t, J¼7.3 Hz,1H, CHaromatic), 7.27e7.23 (m, 2H, CHaromatic),
7.15e7.09 (m, 3H, CHaromatic), 4.03 (q, J¼7.3 Hz, 2H, CH2CH3), 2.36 (s,
3H, PhCH3), 0.79 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz,
CDCl3) d: 171.9, 161.2, 143.4, 139.5, 137.0, 135.4, 129.7, 129.2, 127.4,
127.3, 127.1, 125.7, 125.5, 123.9, 121.1, 106.0, 60.9, 21.4, 13.0; HRMS
calcd for C20H18O3 (Mþ) 306.1256; found 306.1248. IR (cmꢁ1
n
)
(KBr): 2926, 1618, 1508, 1374, 1232, 1101, 1018, 958, 823, 785,
749, 613.
4.3.20. Ethyl 4-hydroxy-2-(4-methoxyphenyl)dibenzo[b,d]thiophene-
3-carboxylate (4t). The product was obtained as yellow crystals in
hexane/CH2Cl2 (141.9 mg, 75%); mp 122e125 ꢀC; Rf (5% ethyl ace-
4. (a) Pinskaya, M.; Romanova, E.; Volkov, E.; Deprez, E.; Leh, H.; Brochon, J.-C.;
Mouscadet, J.-F.; Gottikh, M. Biochemistry 2004, 43, 8735e8743; (b) El-Sabbagh,
O. I.; Rady, H. M. Eur. J. Med. Chem. 2009, 44, 3680e3686.
tate/hexane) 0.41; 1H NMR (400 MHz, CDCl3)
d: 11.66 (s, 1H, OH),
5. (a) Wainwright, M. J. Antimicrob. Chemother. 2001, 47, 1e13; (b) Kavitha, H. P.
Asian J. Chem. 2004, 16, 1191e1193; (c) Patel, C. L.; Parekh, H. J. Indian Chem. Soc.
1988, 65, 282e284.
8.02 (d, J¼8.0 Hz, 1H, CHaromatic), 7.84 (d, J¼8.1 Hz, 1H, CHaromatic),
7.48 (s, 1H, CHaromatic), 7.44e7.41 (m, 1H, CHaromatic), 7.40e7.36 (m,
1H, CHaromatic), 7.19e7.16 (m, 2H, CHaromatic), 6.86 (d, J¼8.8 Hz, 2H,
CHaromatic), 3.99 (q, J¼7.3 Hz, 2H, CH2CH3), 3.80 (s, 3H, PhOCH3),
6. (a) Giorgio, C. D.; Shimi, K.; Boyer, G.; Delmas, F.; Galy, J. P. Eur. J. Med. Chem.
2007, 42, 1277e1284; (b) Chauhan, P. M. S.; Srivastava, S. K. Curr. Med. Chem.
2001, 8, 1535e1542; (c) Fattorusso, C.; Campiani, G.; Kukreja, G.; Persico, M.;
Butini, S.; Romano, M. P.; Altarelli, M.; Ros, S.; Brindisi, M.; Savini, L.; Novellino,
E.; Nacci, V.; Fattorusso, E.; Parapini, S.; Basilico, N.; Taramelli, D.; Yardley, V.;
Croft, S.; Borriello, M.; Gemma, S. J. Med. Chem. 2008, 51, 1333e1343.
7. Patel, N. A.; Sruthi, S. C.; Patel, R. D.; Patel, M. P. Phosphorus, Sulfur, Silicon Relat.
Elem. 2008, 183, 2191e2203.
0.79 (t, J¼7.3 Hz, 3H, CH2CH3); 13C NMR (100 MHz, CDCl3)
d: 171.3,
158.7, 157.4, 141.7, 140.9, 139.6, 135.9, 135.2, 129.6, 127.8, 126.2,
124.6, 123.2, 122.6, 115.8, 113.0, 108.7, 61.2, 55.4, 13.2; HRMS calcd
C
22H18O4S (Mþ) 378.0926; found 378.0925. IR (cmꢁ1) (liquid
n
film): 2953, 2853, 1731, 1651, 1608, 1463, 1394, 1372, 1304, 1260,
1175, 1018, 945, 831, 805, 783.
8. Dolphin, G. T.; Chierici, S.; Ouberai, M.; Dumy, P.; Garcia, J. ChemBioChem 2008,
9, 952e963.
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Guare, J. P.; Vacca, J. P.; Hazuda, D. J.; Felock, P. J.; Wolfe, A. L.; Stillmock, K. A.;
Witmer, M. V.; Moyer, G.; Schleif, W. A.; Gabryelski, L. J.; Leonard, Y. M.; Lynch,
J. J.; Michelson, S. R.; Young, S. D. J. Med. Chem. 2003, 46, 453e456.
11. Chen, C.-H.; Lin, Y.-W.; Kakadiya, R.; Kumar, A.; Chen, Y.-T.; Lee, T.-C.; Su, T.-L.
Tetrahedron 2011, 67, 5883e5893.
12. (a) Acheson, R. M. An Introduction to the Chemistry of Heterocyclic Compounds,
3rd ed.; Wiley-Interscience: New York, NY, 1976; (b) Sourdon, V.; Mazoyer, S.;
Pique, V.; Galy, J. Molecules 2001, 6, 673e682.
Acknowledgements
We gratefully acknowledge the Department of Science and
Technology, New Delhi, India and University of Delhi for financial
support. The University Science Instrumentation Centre, University
of Delhi, is also gratefully acknowledged for NMR and XRD facilities.
S.P.S. is thankful to the Council of Scientific and Industrial Research,
New Delhi, India, for a fellowship.
13. (a) Belmont, P.; Belhadj, T. Org. Lett. 2005, 7, 1793e1795; (b) Tiano, M.; Belmont,
P. J. Org. Chem. 2008, 73, 4101e4109.
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147e155; (b) Gowda, R. R.; Chakraborty, D.; Ramkumar, V. Inorg. Chim. Acta
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Bioorg. Med. Chem. Lett. 1993, 3, 2789e2792; (d) Patel, H. S.; Oza, K. K. E -J Chem.
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Supplementary data
Supplementary data (1H and 13C NMR spectra, HRMS, IR) associ-
ated with this article can be found. Supplementary data related to this
article can be found at http://dx.doi.org/10.1016/j.tet.2012.08.068.
These data include MOL files and InChIKeys of the most important
compounds described in this article.
References and notes
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