Iodine-mediated neighboring group assisted synthesis of unsymmetrical 1,2-diketone/benzil derivatives from o-(alkynyl)benzamides

Article abstract of DOI:10.1055/s-0030-1260155

A facile synthesis of 1,2-diketone derivatives have been achieved from o-(alk-1-ynyl)benzamide derivatives in good to excellent yields by molecular iodine-catalyzed electrophilic reaction. The reaction proceeds via formation of an (isochromenylidene)benze

Full text of DOI:10.1055/s-0030-1260155

PAPER
2951
Iodine-Mediated Neighboring Group Assisted Synthesis of Unsymmetrical
1,2-Diketone/Benzil Derivatives from o-(Alkynyl)benzamides
U
nsymmetrical 1,2
.
-Diketone/B
C
enzil
D
erivatives. Majumdar,*a,b,1 Inul Ansary,a Rajendra Narayan De,a B. Roya
a
Department of Chemistry, University of Kalyani, Kalyani 741235, W. B., India
Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784024, Assam, India
E-mail: kcm_ku@yahoo.co.in
b
Received 20 May 2011; revised 24 June 2011
(pyridin-4-yl)-1,3-oxazine with acid chlorides and esters31
have been reported to give 1-aryl-2-(pyridin-4-yl)ethane-
1,2-diones. Although there are many methods available
for the synthesis of 1,2-diketones, several drawbacks are
Abstract: A facile synthesis of 1,2-diketone derivatives have been
achieved from o-(alk-1-ynyl)benzamide derivatives in good to ex-
cellent yields by molecular iodine-catalyzed electrophilic reaction.
The reaction proceeds via formation of an (isochromenylidene)ben-
zenaminium intermediate formed by the intramolecular neighbor- associated with some of these protocols, such as high tox-
ing group assistance of the ortho-amide group.
icity and environmental burden, the requirment for special
equipment, high cost performance, and/or low yields etc.
In recent years, iodocyclization has emerged as an effec-
tive protocol for the preparation of a variety of heterocy-
clic and carbocyclic compounds.32–39 Very recently
Srinivasan et al.40 have reported the synthesis of a series
of tricarbonyl compounds by the oxidation of o-alkynyl-
arenecarbaldehydes in an iodine/water system. In contin-
uation of our interest in the electrophilic iodocyclization
strategy41 we have independently made a similar observa-
tion while investigating the synthesis of medium-ring-size
azepinone42 or azocinone43 derivatives; instead of the de-
sired products we obtained unsymmetrical 1,2-diketones/
benzil derivatives. The results are reported herein.
Key words: molecular iodine, o-(alkynyl)benzamides, 1,2-dike-
tones, benzil
1,2-Diketones are of interest in general synthesis,2 they
are frequently found as structural motifs in molecules of
biological and/or medicinal interest,3 and they have been
used as important synthetic intermediates in organic syn-
thesis.4 Benzils (1,2-diarylethane-1,2-diones) are an im-
portant class of compounds for organic synthesis as the
synthetic studies of both symmetrical and unsymmetrical
benzils have been reported.5,6 Some benzils exhibited var-
ious potential biological activity including inhibition of
mammalian carboxylesterases (CE).3a,7 Moreover, a vari-
ety of biologically active heterocyclic compounds, such as
imidazoles, triazines, and quinoxalines, can be synthe-
sized from benzil derivatives.8 Many protocols have been
developed for the synthesis of 1,2-diketones involving ox-
idation of various precursors: (a) olefins with selenium
dioxide9 or potassium permanganate;10 (b) a-hydroxy ke-
tones or tautomeric 1,2-dihydroxyolefins by atmospheric
oxygen,11 iodine,12 sodium hypobromite,13 or triphenylan-
timony dibromide;14 (c) alkynes with potassium perman-
ganate,6b N-bromosuccinimide/dimethyl sulfoxide,15
palladium(II) chloride/dimethyl sulfoxide,6d chromium16
or manganese oxidants,17 ozonolysis,18 sulfur trioxide–
dioxane complex,19 dioxiranes,20 iodine reagents, such
as N-iodosuccinimide21 or orthoperiodic acid,22
[Ru(cymene)Cl2]2,23 or palladium on carbon;24 (d) meth-
ylene ketones by selenium dioxide,6c,9a,b,25 hypervalent
iodine compounds,26 hydrobromic acid/dimethyl
sulfoxide,9a,b,27 bismuth nitrate–copper(II) acetate,28 or
oxygen in the presence of Fe(III)–EDTA;29 (e) a-benzo-
triazolyl ketones6e with oxygen in dimethyl sulfoxide in
the presence of sodium hydrogen carbonate or potassium
carbonate ; and (f) aryl benzyl ethers30 with dioxirane.
Among non-oxidative methods, the reaction of lithiated 2-
The starting materials 2a–k were prepared in 71–90%
yields by reaction of the corresponding 2-iodobenzamide
derivatives 1a–g with substituted alkynes under
Sonogashira reaction conditions [PdCl2(PPh3)2 (3 mol%),
CuI (3 mol%), Et3N, DMF, r.t., 5 h] (Scheme 1). We used
compound 2a as a model substrate for our investigations.
R2
R1
O
R2
R1
O
N
N
(i)
R3
I
1a–g
2a–k
3 = Ph, Pr, Bu
R3
R1 = Me, Et
R2 = aryl, heterocycle
R
Scheme 1 Reagents and conditions: (i) PdCl2(PPh3)2 (3 mol%), CuI
(3 mol%), Et3N, DMF, r.t., 5 h.
When compound 2a was subjected to iodocyclization
with iodine (3 equiv) and sodium hydrogen carbonate (3
equiv) in acetonitrile at 25 °C for six hours, the desired cy-
clized product, either azocinone derivative 4a or azepi-
none derivative 5a, was not formed, instead the
uncyclized oxidation product, i.e. benzil derivative 3a,
was isolated in only 15% yield (Scheme 2).
Under the circumstances we diverted our investigation to
improve the yield of benzil derivative 3a and our initial
studies were aimed at finding the optimal reaction condi-
tions for the synthesis of 1,2-diketones via iodine-cata-
SYNTHESIS 2011, No. 18, pp 2951–2958
Advanced online publication: 05.08.2011
DOI: 10.1055/s-0030-1260155; Art ID: Z53511SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
1
1

2952
K. C. Majumdar et al.
PAPER
Et
O
water (9:1) resulted in no improvement in the yield of 3a
(entry 5). Other solvents such as dichloromethane, ni-
tromethane, and methanol were also investigated and
proved to be far less effective (entries 6–8). Reducing the
amount of both iodine and sodium hydrogen carbonate
from 3 to 1.5 equivalents gave a reduced yield of 3a (entry
9). In the absence of base, the reaction gave a very poor
yield of 3a even over ten hours (entry 10). In the absence
of iodine the starting material 2a remained unchanged
(entry 11). Using potassium carbonate as the base instead
of sodium hydrogen carbonate also did not improve the
yield of 3a (entry 12). Based on the above optimization ef-
forts, the combination of iodine (3 equiv), sodium hydro-
gen carbonate (3 equiv) and the use of acetonitrile–water
(19:1) at 45 °C was found to be satisfactory.
Et
N
Et
N
N
i
O
O
O
O
2a
Ph
I
3a
Ph
Ph
4a, not found
found, 15%
Et
O
N
Ph
5a, not found
I
Scheme 2 Reagents and conditions: (i) I2 (3 equiv), NaHCO3 (3
equiv), MeCN, 25 °C, 6 h.
lyzed electrophilic reactions of o-(alkynyl)benzamides
2a–k (Table 1). When the reaction was attempted using 2-
(phenylethynyl)benzamide derivative 2a, iodine (3 equiv)
and sodium hydrogen carbonate (3 equiv) in acetonitrile–
water (19:1) at 25 °C for six hours, the benzil derivative
3a was obtained in 52% yield (entry 2). By increasing the
reaction temperature from 25 °C to 45 °C the yield of the
product 3a increased sharply from 52% to 88% over two
hours (entry 3). Further increase in the reaction tempera-
ture from 45 °C to 70 °C resulted in a lower yield of the
benzil derivative 3a (55%) and a 20% yield of the enol de-
rivative 6a (entry 4). Increasing the proportion of water in
acetonitrile from acetonitrile–water (19:1) to acetonitrile–
To test the generality of the reaction, other substrates 2b–k
were allowed to react under the optimized reaction condi-
tions to afford the corresponding 1,2-diketone derivatives
3b–k in good to excellent yields (Table 2).
All the products were characterized by spectroscopic
techniques, especially 13C NMR spectra in which two keto
carbonyl carbons appeared at dC = 190–200. The mecha-
nism for the oxidation reactions of o-(alkynyl)benzamides
2a–k is believed to proceed via initially formed iodonium
intermediates 7a–k, which undergo cyclization, by in-
tramolecular neighboring group assistance by the ortho-
Table 1 Optimization of Iodine-Catalyzed Reactions
R2
R1
R1
N
R1
N
N
O
O
R1 = Et
R2 = Ph
R3 = Ph
R2
O
R2
H
O
R3
R3
OH
R3
O
2a
3a
6a
Entry
I2 (equiv)
Base (equiv)
Solvent
Temp (°C)
Time (h)
Yielda (%)
1
2
3b
4
5
6
7
8
9
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
1.5
3.0
–
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (3.0)
NaHCO3 (1.5)
–
MeCN
25
25
45
70
45
45
45
45
45
45
45
45
6
6
15
52
88
55c
85
65
48
MeCN–H2O (19:1)
MeCN–H2O (19:1)
MeCN–H2O (19:1)
MeCN–H2O (9:1)
CH2Cl2–H2O (19:1)
MeNO2–H2O (19:1)
MeOH–H2O (19:1)
MeCN–H2O (19:1)
MeCN–H2O (19:1)
MeCN–H2O (19:1)
MeCN–H2O (19:1)
2
2
2
2
2
d
2
–
2
36
<5
10
10
12
2
e
11
12
NaHCO3 (3.0)
K2CO3 (3.0)
–
3.0
86
a Isolated yield of the compound 3a.
b Optimized reaction conditions.
c Compound 6a was also isolated in 20% yield.
d Several unidentified spots (TLC) were formed.
e No reaction occurred.
Synthesis 2011, No. 18, 2951–2958 © Thieme Stuttgart · New York

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Unsymmetrical 1,2-Diketone/Benzil Derivatives
2953
Table 2 Iodine-Catalyzed Synthesis of 1,2-Diketone Derivatives
R1
N
R2
R1
N
O
R2
O
O
R3
I2, NaHCO3
MeCN–H2O (19:1)
45 °C, 2–3 h
O
2a–k
R3
3a–k
Entry
R1
Et
R2
Ph
Ph
Ph
Ph
Ph
R3
Ph
Bu
Bu
Pr
Time (h)
Product
3a
Yield (%)
1
2
3
4
5
6
7
8
2
3
2
3
2
2
2
2
88
84
70
78
63
75
67
72
Me
Et
3b
3c
Me
Et
3d
Pr
3e
Et
4-MeC6H4
4-MeC6H4
4-MeOC6H4
O
Ph
Pr
3f
Et
3g
Et
Ph
3h
Me
N
9
Me
Ph
3
3i
92
O
N
Me
O
Me
O
N
10
11
Et
Ph
Pr
3
2
3j
90
81
N
Me
Me
3k
O
O
amide involving the nitrogen lone pair and the carbonyl When 2-(phenylethynyl)benzylamine 12 was treated un-
group in a 6-endo-dig fashion, to produce (isochrome- der the optimized reaction conditions, decomposition of
nylidene)benzenaminium intermediates 8a–k. The inter- the starting material occurred. On the other hand, when 1-
mediates 8a–k may then react with a molecule of water to methoxy-4-(phenylethynyl)benzene (13) was subjected to
afford the isochromenol intermediates 9a–k. These may iodine-catalyzed electrophilic reaction under the opti-
again react with another molecule of iodine to generate mized reaction conditions, 1,2-diiodoethene 14 was iso-
the diiodo intermediates 11a–k, which may then react lated in 90% yield (Scheme 4).
with water to form the 1,2-diketone derivatives 3a–k
(Scheme 3).
Ph
N
(i)
decomposition of the starting
material occurred
Et
I
R2
R1
OH
O
12
Ph
R2
R1
O
R2
R1
O
I
N
I
N
N
(i)
OH2
OMe
I2
OMe
H2O, base
– HI
6-endo-dig
I
13
14, 90%
R3
I
R3
I
R3
I
I
Scheme 4 Reagents and conditions: (i) I2 (3 equiv), NaHCO3 (3
equiv), MeCN–H2O (19:1), 45 °C, 3 h.
7a–k
R2
8a–k
R2 R1
9a–k
R1
R1
I
N
N
N
O
R2
The aforesaid two reactions clearly indicate that the oxi-
dation reaction for the formation of 1,2-diketone deriva-
tives from o-(alkynyl)benzamides 2a–k necessitates the
occurrence of neighboring group assistance by the ortho-
amide carbonyl group. Like the amide (CONR1R2) group,
O
base
– HI
O
H2O
OH
O
R3
O
R3
O
I
I
I
R3
I
10a–k
11a–k
3a–k
Scheme 3 Possible reaction mechanism for the iodine-catalyzed the ester (CO2R) group could also act as a neighboring
synthesis of 1,2-diketone derivatives
Synthesis 2011, No. 18, 2951–2958 © Thieme Stuttgart · New York

2954
K. C. Majumdar et al.
PAPER
13C NMR (100 MHz, CDCl3): d = 13.1, 44.4, 87.6, 93.0, 120.6,
123.1, 127.1, 127.7, 128.2, 128.4, 128.5, 128.8, 129.0, 129.6, 131.6,
131.9, 140.2, 141.9, 169.3.
HRMS: m/z [M + Na]+ calcd for C23H19NNaO: 348.1364; found:
348.1369.
group. When methyl 2-pent-1-ynylbenzoate (15) was sub-
jected to our optimized reaction condition, isochrome-
none derivative 16 was obtained in 93% yield with out any
contamination by the 1,2-diketone derivative 17
(Scheme 5).
2-Hex-1-ynyl-N-methyl-N-phenylbenzamide (2b)
Gummy; yield: 84%.
IR (neat): 1652, 2231, 2957 cm–1.
O
O
1H NMR (400 MHz, CDCl3): d = 0.96 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.51–1.62 [m, 4 H, (CH2)2CH3], 2.46 (t, J = 7.2 Hz, 2 H, C≡CCH2),
3.50 (s, 3 H, NCH3), 7.03–7.21 (m, 9 H, HAr).
OMe
I
O
(i)
16, 93%
MeO
O
O
MS (ESI): m/z = 314 [M + Na]+.
15
Anal. Calcd for C20H21NO: C, 82.44; H, 7.26; N, 4.81. Found: C,
82.31; H, 7.25; N, 5.02.
O
17
N-Ethyl-2-hex-1-ynyl-N-phenylbenzamide (2c)
Gummy; yield: 78%.
IR (neat): 1651, 2230, 2931 cm–1.
Scheme 5 Reagents and conditions: (i) I2 (3 equiv), NaHCO3 (3
equiv), MeCN–H2O (19:1), 45 °C, 3 h.
1H NMR (400 MHz, CDCl3): d = 0.96 (t, J = 6.7 Hz, 3 H, CH2CH3),
1.25 (t, J = 7.3 Hz, 3 H, NCH2CH3), 1.50–1.54 (m, 2 H, CH2CH3),
1.59–1.64 (m, 2 H, C≡CCH2CH2), 2.47 (t, J = 7.3 Hz, 2 H,
C≡CCH2), 3.96–4.00 (m, 2 H, NCH2), 6.99–7.02 (m, 2 H, HAr),
7.05–7.13 (m, 3 H, HAr), 7.15–7.19 (m, 4 H, HAr).
A somewhat similar observation by Srinivasan et al.40
came to our notice while preparing this manuscript.
In conclusion, we have developed a straightforward, envi-
ronmentally benign, metal-free procedure for the oxida-
tion of o-(alkynyl)benzamides to the corresponding 1,2-
diketone derivatives. The reaction proceeds via the forma-
MS (ESI): m/z = 306 [M + H]+.
Anal. Calcd for C21H23NO: C, 82.58; H, 7.59; N, 4.59. Found: C,
tion of an (isochromenylidene)benzenaminium intermedi- 82.41; H, 7.63; N, 4.70.
ate formed by intramolecular neighboring group
N-Methyl-2-pent-1-ynyl-N-phenylbenzamide (2d)
Gummy; yield: 71%.
IR (neat): 1652, 2233, 2963 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.08 (t, J = 6.8 Hz, 3 H, CH2CH3),
1.64–1.68 (m, 2 H, CH2CH3), 2.44 (t, J = 6.8 Hz, 2 H, C≡CCH2),
3.50 (s, 3 H, NCH3), 7.08–7.41 (m, 9 H, HAr).
participation of the ortho-amide group. The reaction is
easy to perform and isolation of the final product from the
reaction mixture is also simple.
Melting points were determined in open capillaries and are uncor-
rected. IR spectra were run for KBr discs (and neat for liquid sam-
ples) on a Perkin-Elmer 120-000A apparatus and 1H NMR spectra
were determined for solns in CDCl3 with TMS as internal standard
on a Bruker DPX-400 and Jeol ECS-400. 13C NMR spectra were de-
termined for solns in CDCl3 on a Bruker DPX-400. Mass spectra
were recorded on a Qtof-Micro instrument. CHN was recorded on
2400 series II CHN analyzer Perkin-Elmer. Silica gel (60–120
mesh) and (230–400 mesh) were used for chromatographic separa-
tion. Silica gel-G [E-Mark (India)] was used for TLC. Petroleum
ether (PE) has bp 60–80 °C.
MS (ESI): m/z = 300 [M + Na]+.
Anal. Calcd for C19H19NO: C, 82.28; H, 6.90; N, 5.05. Found: C,
82.06; H, 6.86; N, 5.23.
N-Ethyl-2-pent-1-ynyl-N-phenylbenzamide (2e)
White solid; yield: 79%. mp 63–64 °C.
IR (KBr): 1643, 2230, 2963 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.08 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.24 (t, J = 7.2 Hz, 3 H, NCH2CH3), 1.63–1.72 (m, 2 H, CH2CH3),
2.45 (t, J = 7.2 Hz, 2 H, C≡CCH2), 3.97–4.00 (m, 2 H, NCH2), 7.02–
7.22 (m, 9 H, HAr).
N-Ethyl-N-phenyl-2-(phenylethynyl)benzamide (2a); Typical
Procedure for 2a–k and 15
To a stirred soln of 1a (500 mg, 1.42 mmol), PdCl2(PPh3)2 (30 mg,
3 mol%), and CuI (8 mg, 3 mol%) in DMF–Et3N (4:1, 10 mL), a
soln of phenylacetylene (174 mg, 0.18 mL, 1.70 mmol) in DMF (0.5
mL) was added dropwise at r.t. and the mixture was stirred for 5 h.
The mixture was diluted to 50 mL with CH2Cl2, washed with H2O
(3 × 20 mL) and brine (20 mL), and dried (Na2SO4). The solvent
was removed under reduced pressure and the crude product was pu-
rified by column chromatography (silica gel, 60–120 mesh, EtOAc–
PE, 1:9) to give 2a as a white solid; yield: 76%; mp 85–86 °C.
MS (ESI): m/z = 314 [M + Na]+.
Anal. Calcd for C20H21NO: C, 82.44; H, 7.26; N, 4.81. Found: C,
82.39; H, 7.11; N, 4.67.
N-Ethyl-N-(4-methylphenyl)-2-(phenylethynyl)benzamide (2f)
Gummy; yield: 79%.
IR (neat): 1651, 2218, 2973 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.25 (t, J = 7.2 Hz, 3 H,
NCH2CH3), 2.22 (s, 3 H, CH3), 3.94–4.02 (m, 2 H, NCH2), 6.80–
6.64 (m, 1 H, HAr), 6.93–6.96 (m, 1 H, HAr), 6.98–7.02 (m, 2 H,
HAr), 7.06–7.09 (m, 1 H, HAr), 7.11–7.15 (m, 2 H, HAr), 7.33–7.38
(m, 3 H, HAr), 7.55–7.57 (m, 2 H, HAr), 7.65 (d, J = 8.0 Hz, 1 H,
HAr).
IR (KBr): 1637, 2238, 2972 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.26 (t, J = 6.8 Hz, 3 H,
NCH2CH3), 4.01–4.03 (m, 2 H, NCH2), 7.06–7.20 (m, 8 H, HAr),
7.34–7.38 (m, 4 H, HAr), 7.55–7.57 (m, 2 H, HAr).
MS (ESI): m/z = 362 [M + Na]+.
Synthesis 2011, No. 18, 2951–2958 © Thieme Stuttgart · New York

PAPER
Unsymmetrical 1,2-Diketone/Benzil Derivatives
2955
Anal. Calcd for C24H21NO: C, 84.92; H, 6.24; N, 4.13. Found: C,
85.05; H, 6.11; N, 4.37.
3.50 (s, 3 H, NCH3), 6.38 (d, J = 7.9 Hz, 1 H, HAr), 7.10 (br s, 3 H,
HAr), 7.22 (br s, 1 H, HAr), 7.24–7.32 (m, 1 H, HAr), 7.37 (br s, 2 H,
HAr), 7.51 (d, J = 6.7 Hz, 1 H, HAr).
N-Ethyl-N-(4-methylphenyl)-2-pent-1-ynylbenzamide (2g)
Gummy; yield: 72%.
MS (ESI): m/z = 368 [M + Na]+.
Anal. Calcd for C22H19NO3: C, 76.50; H, 5.54; N, 4.06. Found: C,
76.67; H, 5.48; N, 3.87.
IR (neat): 1652, 2230, 2955 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.03 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.15 (t, J = 7.2 Hz, 3 H, NCH2CH3), 1.66–1.75 (m, 2 H, CH2CH3),
2.33 (s, 3 H, CH3), 2.47 (t, J = 7.2 Hz, 2 H, C≡CCH2), 3.95–3.98 (m,
2 H, NCH2), 7.08–7.28 (m, 4 H, HAr), 7.35–7.41 (m, 3 H, HAr), 7.52
(d, J = 7.2 Hz, 1 H, HAr).
Methyl 2-Pent-1-ynylbenzoate (15)
Colorless oil; yield: 80%.
IR (neat): 1748, 2230, 3015 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.07 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.62–1.69 (m, 2 H, CH2CH3), 2.46 (t, J = 7.2 Hz, 2 H, C≡CCH2),
3.92 (s, 3 H, OCH3), 7.31 (td, J = 7.6, 0.8 Hz, 1 H, HAr), 7.41 (td,
J = 7.6, 1.2 Hz, 1 H, HAr), 7.51 (dd, J = 8.0, 0.8 Hz, 1 H, HAr), 7.88
(dd, J = 7.6, 0.8 Hz, 1 H, HAr).
MS (ESI): m/z = 328 [M + Na]+.
Anal. Calcd for C21H23NO: C, 82.58; H, 7.59; N, 4.59. Found: C,
82.61; H, 7.43; N, 4.52.
N-Ethyl-N-(4-methoxyphenyl)-2-(phenylethynyl)benzamide
(2h)
Gummy; yield: 80%.
IR (neat): 1652, 2232, 2965 cm–1.
MS (ESI): m/z = 225 [M + Na]+.
Anal. Calcd for C13H14O2: C, 77.20; H, 6.98. Found: C, 76.97; H,
7.10.
1H NMR (400 MHz, CDCl3): d = 0.95 (t, J = 7.3 Hz, 3 H,
NCH2CH3), 3.55–3.63 (m, 1 H, NCHaHb), 3.73 (s, 3 H, OCH3),
4.41–4.51 (m, 1 H, NCHaHb), 6.31 (d, J = 7.9 Hz, 1 H, HAr), 6.71
(dd, J = 8.5, 2.4 Hz, 1 H, HAr), 6.77–6.81 (m, 1 H, HAr), 6.92–6.97
(m, 2 H, HAr), 7.10 (d, J = 9.2 Hz, 1 H, HAr), 7.15–7.21 (m, 1 H,
HAr), 7.24–7.35 (m, 2 H, HAr), 7.41–7.46 (m, 3 H, HAr), 7.79 (dd,
J = 8.5, 7.9 Hz, 1 H, HAr).
2-(1,2-Dioxo-2-phenylethyl)-N-ethyl-N-phenylbenzamide (3a);
Typical Procedure for 3a–k and 16
A mixture of 2a (150 mg, 0.46 mmol), NaHCO3 (116 mg, 1.38
mmol), and I2 (351 mg, 1.38 mmol) in MeCN–H2O (19:1, 5 mL)
was stirred at 45 °C for 2 h. The mixture was quenched with 10%
aq Na2S2O3 soln and then it was extracted with CH2Cl2 (3 × 20 mL),
washed with H2O (2 × 10 mL) and brine (10 mL), and dried
(Na2SO4). The solvent was removed under reduced pressure and
the crude product was purified by column chromatography (silica
gel, 230–400 mesh, EtOAc–PE, 1:19) to give 3a as a white solid;
yield: 88%; mp 124–125 °C.
MS (ESI): m/z = 378 [M + Na]+.
Anal. Calcd for C24H21NO2: C, 81.10; H, 5.96; N, 3.94. Found: C,
80.84; H, 6.07; N, 3.76.
IR (KBr): 1622, 1663, 1678, 2970 cm–1.
N-(1,3-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-
N-methyl-2-(phenylethynyl)benzamide (2i)
Gummy; yield: 88%.
IR (neat): 1652, 1667, 1705, 2230, 2966 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.19 (s, 3 H, NCH3), 3.23 (s, 3 H,
NCH3), 3.35 s, 3 H, NCH3), 7.25–7.30 (m, 3 H, two HAr, uracil C6-
H), 7.35–7.45 (m, 5 H, HAr), 7.51–7.53 (m, 2 H, HAr).
1H NMR (400 MHz, CDCl3): d = 1.01 (t, J = 6.8 Hz, 3 H,
NCH2CH3), 3.84 (q, J = 6.8 Hz, 2 H, NCH2CH3), 6.95 (d, J = 7.6
Hz, 1 H, HAr), 7.19–7.23 (m, 2 H, HAr), 7.27–7.31 (m, 2 H, HAr),
7.34–7.38 (m, 3 H, HAr), 7.53 (t, J = 7.6 Hz, 2 H, HAr), 7.63–7.67
(m, 1 H, HAr), 7.81 (d, J = 7.6 Hz, 1 H, HAr), 8.15 (d, J = 7.6 Hz, 2
H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.5, 45.5, 127.3, 128.0, 128.6,
129.0, 129.3, 129.4, 130.6, 131.1, 131.5, 133.4, 134.1, 135.1, 137.7,
142.7, 168.5, 191.3, 193.2.
MS (ESI): m/z = 396 [M + Na]+.
Anal. Calcd for C22H19N3O3: C, 70.76; H, 5.13; N, 11.25. Found: C,
70.54; H, 5.16; N, 11.33.
HRMS: m/z [M + Na]+ calcd for C23H19NNaO3: 380.1263; found:
380.1266.
N-(1,3-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-
N-ethyl-2-(phenylethynyl)benzamide (2j)
Gummy; yield: 90%.
IR (neat): 1650, 1663, 1709, 2230, 2962 cm–1.
2-(1,2-Dioxohexyl)-N-methyl-N-phenylbenzamide (3b)
White solid; yield: 84%; mp 62–63 °C.
IR (KBr): 1620, 1695, 1714, 2963 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.24 (t, J = 7.2 Hz, 3 H,
NCH2CH3), 3.19 (s, 3 H, NCH3), 3.22 (s, 3 H, NCH3), 3.34–3.41 (m,
1 H, NCHaHb), 4.21–4.26 (m, 1 H, NCHaHb), 7.25–7.31 (m, 3 H, 2
HAr, uracil C6-H), 7.38–7.40 (m, 4 H, HAr), 7.43–7.45 (m, 1 H, HAr),
7.52–7.55 (m, 2 H, HAr).
1H NMR (400 MHz, CDCl3): d = 0.97 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.40–1.48 (m, 2 H, CH2CH3), 1.63–1.71 (m, 2 H, COCH2CH2), 3.02
(t, J = 7.2 Hz, 2 H, COCH2), 3.43 (s, 3 H, NCH3), 6.83 (br s, 1 H,
HAr), 7.13 (br s, 1 H, HAr), 7.20–7.23 (m, 1 H, HAr), 7.30 (t, J = 7.2
Hz, 2 H, HAr), 7.36–7.40 (m, 3 H, HAr), 7.70 (d, J = 7.2 Hz, 1 H,
HAr).
MS (ESI): m/z = 410 [M + Na]+.
13C NMR (100 MHz, CDCl3): d = 14.0, 22.3, 25.0, 37.1, 38.5,
126.8, 127.1, 128.5, 129.4, 130.0, 130.4, 130.5, 135.9, 136.8, 144.6,
168.9, 192.8, 201.2.
Anal. Calcd for C23H21N3O3: C, 71.30; H, 5.46; N, 10.85. Found: C,
71.46; H, 5.40; N, 10.76.
MS (ESI): m/z = 346 [M + Na]+.
N-Methyl-N-(2-oxo-2H-1-benzopyran-6-yl)-2-pent-1-ynyl-
benzamide (2k)
Gummy; yield: 85%.
IR (neat): 1650, 1733, 2232, 2964 cm–1.
Anal. Calcd for C20H21NO3: C, 74.28; H, 6.55; N, 4.33. Found: C,
74.03; H, 6.51; N, 4.45.
1H NMR (400 MHz, CDCl3): d = 0.88 (t, J = 7.3 Hz, 3 H, CH2CH3),
1.60–1.65 (m, 2 H, CH2CH3), 2.44 (t, J = 6.7 Hz, 2 H, C≡CCH2),
2-(1,2-Dioxohexyl)-N-ethyl-N-phenylbenzamide (3c)
Gummy; yield: 70%.
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K. C. Majumdar et al.
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IR (neat): 1624, 1687, 1710, 2960 cm–1.
Anal. Calcd for C24H21NO3: C, 77.61; H, 5.70; N, 3.77. Found: C,
77.79; H, 5.72; N, 3.65.
1H NMR (400 MHz, CDCl3): d = 0.96 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.16 (t, J = 7.2 Hz, 3 H, NCH2CH3), 1.40–1.49 (m, 2 H, CH2CH3),
1.65–1.72 (m, 2 H, COCH2CH2), 3.04 (t, J = 7.2 Hz, 2 H, COCH2),
3.92 (q, J = 7.2 Hz, 2 H, NCH2), 6.82 (d, J = 7.2 Hz, 1 H, HAr),
7.07–7.11 (m, 1 H, HAr), 7.21–7.24 (m, 1 H, HAr), 7.29–7.35 (m, 3
H, HAr), 7.46 (d, J = 7.6 Hz, 2 H, HAr), 7.67 (d, J = 7.6 Hz, 1 H, HAr).
2-(1,2-Dioxopentyl)-N-ethyl-N-(4-methylphenyl)benzamide
(3g)
White solid; yield: 67%; mp 58–59 °C.
IR (KBr): 1623, 1685, 1710, 2960 cm–1.
13C NMR (100 MHz, CDCl3): d = 12.6, 13.9, 22.4, 25.0, 37.1, 45.7,
112.3, 127.2, 127.8, 128.5, 129.4, 130.0, 130.4, 136.3, 137.0, 143.0,
168.6, 192.7, 200.8.
1H NMR (400 MHz, CDCl3): d = 1.03 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.15 (t, J = 7.2 Hz, 3 H, NCH2CH3), 1.68–1.78 (m, 2 H, CH2CH3),
2.31 (s, 3 H, CH3), 3.02 (t, J = 7.2 Hz, 2 H, COCH2), 3.88 (q,
J = 7.2 Hz, 2 H, NCH2), 6.84 (d, J = 7.6 Hz, 1 H, HAr), 7.08–7.12
(m, 3 H, HAr), 7.27 (d, J = 8.0 Hz, 2 H, HAr), 7.31–7.35 (m, 1 H,
HAr), 7.66 (d, J = 7.6 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.6, 13.8, 16.4, 21.0, 39.2, 45.7,
127.6, 128.5, 129.8, 130.0, 130.4, 136.3, 137.1, 140.3, 168.5, 192.8,
200.6.
MS (ESI): m/z = 360 [M + Na]+.
Anal. Calcd for C21H23NO3: C, 74.75; H, 6.87; N, 4.15. Found: C,
74.58; H, 6.99; N, 4.25.
2-(1,2-Dioxopentyl)-N-methyl-N-phenylbenzamide (3d)
White solid; yield: 78%; mp 64–65 °C.
IR (KBr): 1625, 1687, 1709, 2964 cm–1.
MS (ESI): m/z = 360 [M + Na]+.
Anal. Calcd for C21H23NO3: C, 74.75; H, 6.87; N, 4.15. Found: C,
74.77; H, 6.86; N, 4.24.
1H NMR (400 MHz, CDCl3): d = 1.03 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.69–1.77 (m, 2 H, CH2CH3), 3.0 (t, J = 7.2 Hz, 2 H, COCH2), 3.43
(s, 3 H, NCH3), 6.83 (br s, 1 H, HAr), 7.13 (br s, 1 H, HAr), 7.20–7.23
(m, 1 H, HAr), 7.28–7.34 (m, 2 H, HAr), 7.36–7.40 (m, 3 H, HAr),
7.70 (d, J = 7.2 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 13.7, 16.4, 38.5, 39.2, 126.8,
127.1, 128.5, 129.4, 130.0, 130.4, 130.6, 136.9, 138.9, 144.6, 169.4,
192.8, 201.0.
2-(1,2-Dioxo-2-phenylethyl)-N-ethyl-N-(4-methoxyphe-
nyl)benzamide (3h)
White solid; yield: 72%; mp 88–89 °C.
IR (KBr): 1625, 1662, 1684, 2947 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.05 (t, J = 7.3 Hz, 3 H,
NCH2CH3), 3.25–3.32 (m, 1 H, NCHaHb), 3.79 (s, 3 H, OCH3),
4.26–4.33 (m, 1 H, NCHaHb), 6.83–6.88 (m, 1 H, HAr), 6.91 (dd,
J = 8.5, 3.0 Hz, 1 H, HAr), 7.06 (dd, J = 8.5, 3.0 Hz, 1 H, HAr), 7.21–
7.29 (m, 2 H, HAr), 7.35–7.38 (m, 1 H, HAr), 7.42–7.55 (m, 2 H,
HAr), 7.59–7.72 (m, 2 H, HAr), 7.82–7.88 (m, 1 H, HAr), 8.01 (d,
J = 7.3 Hz, 1 H, HAr), 8.15 (d, J = 8.5 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.6, 45.7, 55.4, 125.7, 127.9,
128.3, 128.8, 129.1, 129.8, 130.5, 131.5, 132.4, 134.7, 136.4, 138.7,
144.2, 150.2, 168.8, 191.4, 193.2.
MS (ESI): m/z = 332 [M + Na]+.
Anal. Calcd for C19H19NO3: C, 73.77; H, 6.19; N, 4.53. Found: C,
74.03; H, 6.12; N, 4.39.
2-(1,2-Dioxopentyl)-N-ethyl-N-phenylbenzamide (3e)
Gummy; yield: 63%.
IR (neat): 1620, 1695, 1714, 2936 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.03 (t, J = 7.6 Hz, 3 H, CH2CH3),
1.16 (t, J = 7.2 Hz, 3 H, NCH2CH3), 1.69–1.78 (m, 2 H, CH2CH3),
3.02 (t, J = 7.2 Hz, 1 H, COCH2), 3.92 (q, J = 7.2 Hz, 2 H, NCH2),
6.82 (d, J = 7.2 Hz, 1 H, HAr), 7.07–7.11 (m, 1 H, HAr), 7.20–7.25
(m, 1 H, HAr), 7.29–7.35 (m, 3 H, HAr), 7.40 (d, J = 7.6 Hz, 2 H,
HAr), 7.67 (d, J = 7.6 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.6, 13.8, 16.4, 39.2, 45.7,
114.5, 127.2, 127.8, 128.5, 129.4, 130.0, 130.4, 134.2, 136.3, 144.3,
168.3, 192.8, 201.3.
MS (ESI): m/z = 410 [M + Na]+.
Anal. Calcd for C24H21NO4: C, 74.40; H, 5.46; N, 3.62. Found: C,
74.63, H, 5.58; N, 3.34.
N-(1,2-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-
2-(1,2-dioxo-2-phenylethyl)-N-methylbenzamide (3i)
Yellow solid; yield: 92%; mp 208–209 °C.
IR (KBr): 1623, 1662, 1677, 1709, 2944 cm–1.
1H NMR (400 MHz, CDCl3): d = 3.19 (s, 3 H, NCH3), 3.31 (s, 3 H,
NCH3), 3.36 (s, 3 H, NCH3), 7.31–7.33 (m, 1 H, HAr), 7.45–7.49 (m,
2 H, HAr), 7.52–7.56 (m, 2 H, HAr), 7.65–7.69 (m, 1 H, HAr), 7.72 (s,
1 H, uracil C6-H), 7.84–7.86 (m, 1 H, HAr), 8.07 (d, J = 8.0 Hz, 2 H,
HAr).
13C NMR (100 MHz, CDCl3): d = 28.4, 36.1, 37.3, 118.4, 126.7,
128.9, 129.9, 130.4, 131.4, 132.7, 132.9, 133.4, 134.8, 137.7, 143.0,
150.9, 160.7, 170.2, 192.7, 194.0.
MS (ESI): m/z = 346 [M + Na]+.
Anal. Calcd for C20H21NO3: C, 74.28; H, 6.55; N, 4.33. Found: C,
74.43; H, 6.47; N, 4.27.
2-(1,2-Dioxo-2-phenylethyl)-N-ethyl-N-(4-methylphenyl)benz-
amide (3f)
White solid; yield: 75%; mp 118–119 °C.
IR (KBr): 1647, 1669, 1679, 2974 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.0 (t, J = 7.2 Hz, 3 H,
NCH2CH3), 2.30 (s, 3 H, CH3), 3.80 (q, J = 6.8 Hz, 2 H, NCH2),
6.96 (d, J = 7.2 Hz, 1 H, HAr), 7.07 (d, J = 8.0 Hz, 2 H, HAr), 7.19–
7.26 (m, 3 H, HAr), 7.31–7.35 (m, 1 H, HAr), 7.52 (t, J = 7.6 Hz, 2 H,
HAr), 7.63 (t, J = 7.2 Hz, 1 H, HAr), 7.80 (d, J = 7.6 Hz, 1 H, HAr),
8.81 (d, J = 7.6 Hz, 2 H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.8, 21.1, 44.4, 127.3, 127.9,
128.3, 128.6, 129.5, 129.6, 129.9, 130.6, 131.1, 131.6, 134.1, 137.3,
139.0, 142.6, 169.7, 191.3, 193.3.
MS (ESI): m/z = 428 [M + Na]+.
Anal. Calcd for C22H19N3O5: C, 65.18; H, 4.72; N, 10.37. Found: C,
65.15; H, 4.73; N, 10.41.
N-(1,2-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-
2-(1,2-dioxo-2-phenylethyl)-N-ethylbenzamide (3j)
Yellow solid; yield: 90%; mp 191–192 °C.
IR (KBr): 1624, 1663, 1680, 1709, 2940 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.00 (t, J = 7.2 Hz, 3 H,
NCH2CH3), 3.11–3.20 (m, 1 H, NCHaHb), 3.30 (s, 3 H, NCH3), 3.37
(s, 3 H, NCH3), 4.02–411 (m, 1 H, NCHaHb), 7.29–7.31 (m, 1 H,
MS (ESI): m/z = 394 [M + Na]+.
Synthesis 2011, No. 18, 2951–2958 © Thieme Stuttgart · New York

PAPER
Unsymmetrical 1,2-Diketone/Benzil Derivatives
2957
HAr), 7.45–7.48 (m, 2 H, HAr), 7.53 (t, J = 7.6 Hz, 2 H, HAr), 7.64–
7.68 (m, 1 H, HAr), 7.73 (s, 1 H, uracil C6-H), 7.88–7.90 (m, 1 H,
HAr), 8.08 (d, J = 8.0 Hz, 2 H, HAr).
13C NMR (100 MHz, CDCl3): d = 12.2, 28.4, 37.4, 42.5, 116.4,
126.4, 128.7, 130.0, 130.6, 131.3, 132.9, 133.1, 133.4, 134.7, 137.8,
143.4, 151.0, 160.8, 169.8, 192.2, 193.4.
(4) (a) Deng, X.; Mani, N. S. Org. Lett. 2006, 8, 269.
(b) Wolkenberg, S. E.; Wisnoski, D. D.; Leister, W. H.;
Wang, Y.; Zhao, Z.; Lindsley, C. W. Org. Lett. 2004, 6,
1453. (c) McKenna, J. M.; Halley, F.; Souness, J. E.;
McLay, I. M.; Pickett, S. D.; Collis, A. J.; Page, K.; Ahmed,
I. J. Med. Chem. 2002, 45, 2173. (d) Herrera, A. J.; Rondon,
M.; Suarez, E. J. Org. Chem. 2008, 73, 3384.
MS (ESI): m/z = 442 [M + Na]+.
(5) For the synthesis of symmetrical benzil, see:
(a) Schraufstatter, E. Chem. Ber. 1948, 235.
Anal. Calcd for C23H21N3O5: C, 65.86; H, 5.05; N, 10.02. Found: C,
65.77; H, 5.10; N, 9.99.
(b) Schraufstatter, E. Chem. Ber. 1948, 240. (c) VanAllan,
J. A. J. Org. Chem. 1958, 23, 1679. (d) Mohr, B.;
Enkelmann, V.; Wegner, G. J. Org. Chem. 1994, 59, 635.
(e) Nudelman, N.; Schulz, H. J. Chem. Res., Synop. 1999,
422. (f) Kwon, T. W.; Song, S. J.; Kwon, Y. U.; Chung, S.
K. Bull. Korean Chem. Soc. 2003, 24, 229. (g) Yasuike, S.;
Kishi, Y.; Kawara, S.-i.; Kurita, J. Chem. Pharm. Bull. 2005,
53, 425.
2-(1,2-Dioxopentyl)-N-methyl-N-(2-oxo-2H-1-benzopyran-6-
yl)benzamide (3k)
Gummy; yield: 81%.
IR (neat): 1631, 1688, 1732, 1737, 2964 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.04 (t, J = 7.2 Hz, 3 H, CH2CH3),
1.67–1.76 (m, 2 H, CH2CH3), 3.00 (t, J = 7.2 Hz, 2 H, COCH2), 3.44
(s, 3 H, NCH3), 6.43 (d, J = 9.6 Hz, 1 H, HAr), 6.81 (dd, J = 8.8, 2.8
Hz, 1 H, HAr), 7.17 (d, J = 8.0 Hz, 1 H, HAr), 7.29 (d, J = 8.4 Hz, 1
H, HAr), 7.37–7.41 (m, 1 H, HAr), 7.59–7.63 (m, 3 H, HAr), 7.74 (d,
J = 6.8 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 13.7, 16.4, 31.0, 39.3, 107.7,
116.7, 117.5, 117.9, 118.1, 119.2, 125.9, 128.2, 130.2, 130.3, 130.8,
142.8, 143.6, 152.4, 160.2, 168.7, 192.4, 201.3.
(6) For the synthesis of unsymmetrical benzil, see:
(a) Suginome, H. J. Org. Chem. 1958, 23, 1044. (b) Walsh,
C. J.; Mandal, B. K. J. Org. Chem. 1999, 64, 6102.
(c) Chang, L. L.; Sidler, K. L.; Cascieri, M. A.; de Laszlo, S.;
Koch, G.; Li, B.; MacCoss, M.; Mantlo, N.; O’Keefe, S.;
Pang, M.; Rolando, A.; Hagmann, W. K. Bioorg. Med.
Chem. Lett. 2001, 11, 2549. (d) Yusubov, M. S.;
Zholobova, G. A.; Vasilevsky, S. F.; Tretyakov, E. V.;
Knight, D. W. Tetrahedron 2002, 58, 1607. (e) Katritzky,
A. R.; Zhang, D.; Kirichenko, K. J. Org. Chem. 2005, 70,
3271.
(7) (a) Harada, T.; Nakagawa, Y.; Wadkins, R. M.; Potter, P.
M.; Wheelock, C. E. Bioorg. Med. Chem. 2009, 17, 149.
(b) Edwards, C. C.; Hyatt, J. L.; Tsurkan, L.; Bai, F.; Fraga,
C.; Morton, C. L.; Howard-Williams, E. L.; Potter, P. M.;
Redinbo, M. R. J. Mol. Biol. 2005, 352, 165.
(8) Shipe, W. D.; Yang, F.; Zhao, Z.; Wolkenberg, S. E.; Nolt,
M. B.; Lindsley, C. W. Heterocycles 2006, 70, 655.
(9) (a) Fitzi, K. DE 2,221,546, 1972; Chem. Abstr. 1973, 78,
58428. (b) Fitzi, K. US 3,929,807, 1975. (c) Buehler, C. A.;
Harris, J. O.; Arendale, W. F. J. Am. Chem. Soc. 1950, 72,
4953.
(10) (a) Kozlov, N. S.; Shmanal, G. S. Chem. Heterocycl. Compd.
(Engl. Transl.) 1974, 974. (b) Barta, T. E.; Stealey, M. A.;
Collins, P. W.; Weier, R. M. Bioorg. Med. Chem. Lett. 1998,
8, 3443.
(11) (a) Cremlyn, R. J.; Lynch, J. M.; Swinbourne, F. J.
Phosphorus, Sulfur Silicon Relat. Elem. 1991, 57, 173.
(b) Fischer, E. Justus Liebigs Ann. Chem. 1882, 211, 214.
(c) Buehler, C. A.; Harris, J. O. J. Am. Chem. Soc. 1950, 72,
5015. (d) Katritzky, A. R.; Lang, H.; Wang, Z.; Zhang, Z.;
Song, H. J. Org. Chem. 1995, 60, 7619.
(12) (a) Bark, T.; Weyhermuller, T.; Heirtzler, F. Chem.
Commun. 1998, 1475. (b) Heirtzler, F. R. Synlett 1999,
1203. (c) Heirtzler, F.; Neuburger, M.; Kulike, K. J. Chem.
Soc., Perkin Trans. 1 2002, 809. (d) Heirtzler, F. R.;
Neuburger, M.; Zehnder, M.; Constable, E. C. Liebigs Ann./
Recl. 1997, 297.
MS (ESI): m/z = 400 [M + Na]+.
Anal. Calcd for C22H19NO5: C, 70.02; H, 5.07; N, 3.71. Found: C,
69.83; H, 5.10; N, 3.69.
4-Iodo-3-propyl-1H-2-benzopyran-1-one (16)
Gummy; yield: 93%.
IR (neat): 1737, 3076 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.04 (t, J = 7.6 Hz, 3 H, CH2CH3),
1.74–1.84 (m, 2 H, CH2CH3), 2.91 (t, J = 7.6 Hz, 2 H, CH2CH2),
7.51 (td, J = 8.0, 1.2 Hz, 1 H, HAr), 7.72–7.79 (m, 2 H, HAr), 8.23
(dd, J = 8.0, 1.2 Hz, 1 H, HAr).
13C NMR (100 MHz, CDCl3): d = 13.6, 20.8, 39.1, 119.9, 128.6,
129.6, 130.4, 135.6, 137.9, 157.9, 161.3.
MS (ESI): m/z = 337 [M + Na]+.
Anal. Calcd for C12H11IO2: C, 45.88; H, 3.53. Found: C, 45.97; H,
3.61.
Acknowledgment
We thank CSIR (New Delhi) and DST (New Delhi) for financial as-
sistance. I.A. and R.N.D. are grateful to UGC (New Delhi) for their
research fellowships. We also thank DST (New Delhi) for provi-
ding Bruker 400 MHz NMR, Perkin-Elmer CHN-analyzer, IR and
UV-Vis spectrometers under the DST-FIST programme.
References
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