Facile microwave-assisted michael addition of diphenacyl sulfides to chalcones under solvent-free conditions: Generation of symmetrical and unsymmetrical 1,5-diketones

Article abstract of DOI:10.1080/00397911.2011.593106

The article describes an efficient and environmentally friendly Michael addition of 2-[(2-oxo-2-phenylethyl)sulfanyl]-1-phenyl-1-ethanones (diphenacyl sulfides) to substituted chalcones using microwave irradiation under solvent-free conditions, affording

Full text of DOI:10.1080/00397911.2011.593106

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Facile Microwave-Assisted Michael
Addition of Diphenacyl Sulfides
to Chalcones Under Solvent-Free
Conditions: Generation of Symmetrical
and Unsymmetrical 1,5-Diketones
Nidhin Paul a , Muniyappapillai Jeganathan Shanmugam a &
Shanmugam Muthusubramanian a
a Department of Organic Chemistry, School of Chemistry, Madurai
Kamaraj University, Madurai, India
Accepted author version posted online: 01 Feb 2012. Version of
record first published: 05 Sep 2012
To cite this article: Nidhin Paul, Muniyappapillai Jeganathan Shanmugam & Shanmugam
Muthusubramanian (2013): Facile Microwave-Assisted Michael Addition of Diphenacyl Sulfides to
Chalcones Under Solvent-Free Conditions: Generation of Symmetrical and Unsymmetrical 1,5-
Diketones, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 43:1, 129-138
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Synthetic Communications1, 43: 129–138, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.593106
FACILE MICROWAVE-ASSISTED MICHAEL ADDITION
OF DIPHENACYL SULFIDES TO CHALCONES UNDER
SOLVENT-FREE CONDITIONS: GENERATION OF
SYMMETRICAL AND UNSYMMETRICAL
1,5-DIKETONES
Nidhin Paul, Muniyappapillai Jeganathan Shanmugam, and
Shanmugam Muthusubramanian
Department of Organic Chemistry, School of Chemistry, Madurai Kamaraj
University, Madurai, India
GRAPHICAL ABSTRACT
Abstract The article describes an efficient and environmentally friendly Michael addition of
2-[(2-oxo-2-phenylethyl)sulfanyl]-1-phenyl-1-ethanones (diphenacyl sulfides) to substi-
tuted chalcones using microwave irradiation under solvent-free conditions, affording differ-
ently substituted 1,3,5-triarylpentan-1,5-diones in moderate to good yields of 74–83%.
Keywords 1,5-Diketones; diphenacyl sulphide; Michael addition; microwave reaction
INTRODUCTION
Michael addition of enolates to a,b-unsaturated carbonyl compound is an
effective method for the synthesis of 1,5-dicarbonyl compounds through the forma-
tion of C-C bond which can be further transformed to multifunctional molecules via
Robinson annulation.[1] 1,5-Diketones are extremely important synthetic intermedi-
ates and are desirable starting materials for generating many heterocyclic and poly-
functional compounds.[2] Many of these compounds have potential applications
in coordination chemistry, molecular sensing, catalytic reactions, chemical
Received April 22, 2011.
Address correspondence to Shanmugam Muthusubramanian, Department of Organic Chemistry,
School of Chemistry, Madurai Kamaraj University, Madurai, Tamil Nadu 625021, India. E-mail:
muthumanian2001@yahoo.com
129

130
N. PAUL, M. J. SHANMUGAM, AND S. MUTHUSUBRAMANIAN
modification of electrodes, and redox active self-assembly devices.[2d,e] Barium
hydroxide or barium alkoxide like barium isopropoxide catalysed tandem cross
coupling reaction of aryl methyl ketones with aromatic aldehydes,[3] reaction of
chalcones with cyclohexanone[4]=trimethyl silyl enol ethers[5]=deoxybenzoin[6] are
described in literature for the preparation of 1,5-diones. The conjugate addition of
diethyl malonate to chalcones is also an efficient approach.[7] The use of microwave
irradiation[8] for carrying out organic reactions is a well-established procedure and
has emerged as a promising synthetic technique because the reactions are clean, fast,
and economical with easy workup. Microwave irradiation under solvent-free con-
dition[9] enables organic reactions to occur expeditiously at ambient pressure, result-
ing in accelerated reaction rate, reduced reaction time, and relatively good yields.[10]
RESULTS AND DISCUSSION
In continuation of our work on the synthesis of novel heterocyclic
compounds[11] and the reactions of diphenacyl sulfide with electrophilic reagents,[12]
we have explored the reaction of diphenacyl sulfide with a, b-unsaturated carbonyl
compounds. Previously, a related reaction of chalcone with the nitrogen analogs of
diphenacyl sulfide, diphenacylaniline, has led to the formation of a highly substituted
piperidine derivative, (4-benzoyl-5-hydroxy-1,3,5-triphenyl-2-piperidyl)(phenyl)-
methanone.[13] In the present case, we expect such a domino reaction, involving a
Michael addition–aldol condensation sequence, to take place, yielding (4-benzoyl-
5-hydroxy-3,5-diphenyltetrahydro-2H-2-thiopyranyl) (phenyl)methanone 4. Inter-
estingly, the reaction between diphenacyl sulfide and chalcone in the presence of
ethoxide has not gone as expected. The products obtained have been found to be
symmetrical or unsymmetrical 1,3,5-triarylpentane-1,5-diones. The reaction is also
selective as (5-benzoyl-3-phenyl-2-thienyl) (phenyl) methanone 5, a self-condensation
product of diphenacyl sulfide 1 obtained previously in basic medium,[14] has not been
obtained in the present case. The influences of different bases on the reaction have
also been systematically investigated (Table 1). A 1:1.5 molar ratio of diphenacyl sul-
fide and chalcone respectively with 1.5 equivalents of sodium ethoxide as base under
a microwave power of 120 W at 80–85 ꢀC for 2 min has been found to be the opti-
mized condition for the reaction to yield the diketones. It is observed that the yield
of product depends on the molar ratio of the reactants, and a 1:1 molar ratio of
diphenacyl sulfide and chalcone has led to a worse yield than a 1:1.5 molar ratio.
When the ratio is changed to 1:1.8 or 1:2, there is no appreciable change in the yield
of the product. To illustrate the scope of the reaction, different chalcones were
allowed to react with differently substituted diphenacyl sulfides, and in almost all
the reactions, the yields of diketones were appreciable. The reactions were also per-
formed using the conventional method with diethyl ether as the solvent (Table 2).
It is interesting that the reaction has led to the formation of a simple diketone
instead of the routine Michael addition or subsequent intramolecular–aldol ring for-
mation through 6. The formation of the product can be explained by an elimination
involving ArCOCHS, with the acidity of methylene hydrogen being increased by the
sodium ethoxide (Scheme 2). A six-membered cyclic transition state, 7, can be visua-
lized like other popular cis elimination reactions. It must be mentioned that our
attempt to identify the by-product ArCOCHS in the reaction mixture in support

SYMMETRICAL AND UNSYMMETRICAL 1,5-DIKETONES
131
Table 1. Screening of bases and chalcone mole ratio in the formation of 3a
Entry
Catalyst
MW power (W)
Time (min)
Base equiv.
Chalcone equiv.
Yield (%)
a
1
2
K2CO3
NaOH
KOH
120
120
100
80
15
3
5
1.5
1.5
1.5
1
2
—
1.5
1.5
1.5
1.5
1
65b
69c
76c
43b
67c
80c
78c
78c
64b
58b
3
3
4
NaOEt
NaOEt
NaOEt
NaOEt
NaOEt
NaOEt
t-BuOK
Ba(OH)2
N(Et)3
2
5
120
120
120
120
150
120
80
3
6
2
1.5
1.5
1.5
2
7
2
1.5
1.8
2
8
3
9
3
10
11
12
13
14
15
3
2
1.5
1.7
2
6
2
a
100
110
110
110
6
2
—
a
Pyridine
Morpholine
Pyrrolidine
15
15
15
4
2
—
a
—
3
1.5
2
a
6
—
aNo recognizable product was isolated.
bSeparation through wash column.
cAfter recrystallization from ethanol-ethyl acetate mixture.
of the proposed mechanism (either by trapping the proposed intermediate, 2-oxo-2-
phenylethanethial, with diene or by preparing its derivatives) was not successful,
though an awful smell characteristic of thio compounds was noticed during
the workup. 2-Oxo-phenylethanethial had been previously obtained in situ by
Table 2. Yield of 1,3,5-triaryl-1,5-pentanediones 3
Yield (%)
Entry
R2
R3
R1
Compound obtained
MW time (min)
MW
Conventionalc
1
2
H
Cl
H
H
H
H
H
3a
3b
3c
3b
3d
3e
3f
2
1.5
1.5
2
80a
83a
81a
79a
74b
78a
76b
78a
79a
74b
75a
82a
76a
83a
75a
57
60
57
53
50
52
51
57
56
48
50
59
55
62
49
3
H
Ph
Cl
Me
H
4
H
H
5
Me
H
H
2
6
Me
OMe
Me
H
2
7
H
H
1.5
1.5
2
8
H
Cl
H
3g
3c
3h
3i
9
Ph
Me
Me
Cl
H
10
11
12
13
14
15
Cl
Cl
H
2
Me
Me
Me
H
2
Cl
Cl
3j
2
3h
3g
3j
1.5
1.5
2
Cl
Me
Me
Cl
Cl
aRecrystallization from ethanol–ethyl acetate mixture.
bSeparation through wash column.
cPurified through column chromatography.

132
N. PAUL, M. J. SHANMUGAM, AND S. MUTHUSUBRAMANIAN
Scheme 1. Synthesis of 1,3,5-triaryl-1,5-pentanediones 3.
thermolysis of a heteroaryl phenacyl sulfoxide and trapped by Diels–Alder reac-
tion.[15] The acidity of methylene hydrogens adjacent to the sulfur is more than that
of the other methylene hydrogens, and hence the cyclization yielding 4 has not
occurred.
In the NMR spectrum of 1,5-diketones 3 (Fig. 1), when R1 ¼ R2, the methylene
protons Ha and Hc (and Hb and Hd) are diastereotopic in nature. Thus Ha and Hc
give a 2H doublet of doublet and same is the case with Hb and Hd. He appears as
a quintet. When R1 ¼ R2, it is observed that Ha, Hb, Hc, and Hd all appear as sep-
arate doublets of doublets. In some cases (for example, 3j), even though R1 ¼ R2,
the chemical shift differences between Ha and Hc and between Hb and Hd are so close
that in the former case a single doublet of doublet is noticed and in the latter case the
middle peaks merge together and appear as a deceptive triplet.
This article describes the reaction of diphenacyl sulfides with substituted chal-
cones using sodium ethoxide as the base under solvent-free microwave radiation,
yielding symmetrically and unsymmetrically substituted 1,3,5-pentane-1,5-diones
by Michael addition, an alternate efficient route for this class of compounds.
EXPERIMENTAL
Melting points were measured in open capillary tubes and are uncorrected. A
CEM Discover microwave synthesizer (Model No. 908010) operating at 180=264 V
and 50=60 Hz with microwave power maximum level of 300 W and microwave

SYMMETRICAL AND UNSYMMETRICAL 1,5-DIKETONES
133
Scheme 2. Mechanism for the formation of 1,3,5-triaryl-1,5-pentanediones 3. (Figure is provided in color
online.)
frequency of 2455 MHz was employed for the microwave-assisted experiments done
1
in this work. The H and 13C NMR spectra were recorded on a Bruker (Avance)
300-MHz NMR instrument using tetramethylsilane (TMS) as internal standard
and CDCl3 as solvent. Standard Bruker software was used throughout. Chemical
shifts are given in parts per million (d scale), and the coupling constants are given
in hertz. Silica-gel G plates (Merck) were used for thin-layer chromatographic
Figure 1. Structure of 1,3,5-triaryl-1,5-pentanedione. (a) R1 ¼ R2 ¼ R3 ¼ H; (b)R1 ¼ R3 ¼ H, R2 ¼ Cl; (c)
R1 ¼ Ph, R2 ¼ R3 ¼ H; (d) R1 ¼ R2 ¼ CH3, R3 ¼ H; (e) R1 ¼ R2 ¼ H, R3 ¼ CH3; (f) R1 ¼ R2 ¼ H,
R3 ¼ OCH3; (g) R1 ¼ Cl, R2 ¼ H, R3 ¼ CH3; (h) R1 ¼ H, R2 ¼ CH3, R3 ¼ Cl; (i) R1 ¼ R2 ¼ CH3, R3 ¼ Cl;
and (j) R1 ¼ CH3, R2 ¼ R3 ¼ Cl.

134
N. PAUL, M. J. SHANMUGAM, AND S. MUTHUSUBRAMANIAN
(TLC) analysis with a mixture of petroleum ether (60–80 ꢀC) and ethyl acetate as elu-
ent. Elemental analyses were performed on a Perkin-Elmer 2400 Series II Elemental
CHNS analyzer. Infrared (IR) spectra were recorded on a Jasco Fourier transform
(FT)–IR instrument (KBr pellet method).
General Procedure for the Synthesis of 1,5-Diketones (3)
Microwave method. A well-ground mixture of diphenacyl sulfide 1
(1 mmol), chalcone 2 (1.5 mmol), and NaOEt (1.5 mmol), were taken in a 10-mL
microwave tube and was irradiated in a CEM Discover microwave synthesizer
according to the time and power shown in Table 1, and the progress of the reaction
was monitored TLC. At the end of the reaction, water was added to the mixture and
stirred for a while, and the product was collected by filtration and washed with cold
water. The pure products were obtained by crystallization from ethanol–ethyl acet-
ate (4:1) except for 3d, 3f, and 3h, which were purified by a wash column.
Conventional method. A mixture of diphenacyl sulfide 1 (1 mmol) and chal-
cone 2 (1.5 mmol) were taken in a 50-mL conical flask and dissolved in 10-mL ether.
Freshly prepared sodium ethoxide (1.5 mmol) was added to this solution and stirred
for 30 min. After completion of the reaction (monitored by TLC), the mixture was
concentrated under vacuum, and the residue was subjected to column chromato-
graphy using a petroleum ether = ethyl acetate mixture (3:1; v=v) as eluent to afford
the pure products 3.
Spectral and Analytical Data
1,3,5-Triphenyl-1,5-pentanedione (3a). Isolated as colorless solid. Spectro-
scopic data are in the literature.[16]
1-(4-Chlorophenyl)-3,5-diphenyl-1,5-pentanedione (3b). Isolated as col-
1
orless solid; mp 96–97 ꢀC; IR (KBr): 3062, 3026, 2890, 1674, 1679 cmꢁ1; H NMR
(300 MHz, CDCl3) dH: 3.30 (dd, 1H, J ¼ 16.8, 6.9 Hz, CH), 3.35 (dd, 1H, J ¼ 16.8,
6.9 Hz, CH), 3.48 (dd, 2H, J ¼ 16.8, 6.9 Hz, CH2), 4.04 (qnt, 1H, J ¼ 6.9 Hz, CH),
7.15–7.31 (m, 5H, Ar-H), 7.36–7.47 (m, 4H, Ar-H), 7.53–7.58 (m, 1H, Ar-H), 7.89
(d, 2H, J ¼ 8.7 Hz, Ar-H), 7.94 (d, 2H, J ¼ 8.7 Hz, Ar-H); 13C NMR (75 MHz,
CDCl3) dC: 37.1, 44.7, 44.8, 126.8, 127.4, 128.1, 128.5, 128.6, 128.9, 129.6, 133.1,
135.1, 136.8, 139.5, 143.5, 197.4, 198.5. Anal. calcd. for C23H19ClO2: C, 76.13; H,
5.28%. Found: C, 76.09; H, 5.24%.
1-(Biphenyl-4-yl)-3,5-diphenyl-1,5-pentanedione (3c). Isolated as color-
1
less solid; mp 98–99 ꢀC; IR (KBr): 3058, 3029, 2882, 1676, 1683 cmꢁ1; H NMR
(300 MHz, CDCl3) dH: 3.37 (dd, 1H, J ¼ 16.5, 6.9 Hz, CH), 3.38 (dd, 1H, J ¼ 16.5,
6.9 Hz, CH), 3.51 (dd, 1H, J ¼ 16.5, 6.9 Hz, CH), 3.53 (dd, 1H, J ¼ 16.5, 6.9 Hz,
CH), 4.10 (qnt, 1H, J ¼ 6.9 Hz, CH), 7.19–7.21 (m, 1H, Ar-H), 7.28–7.35 (m, 3H,
Ar-H), 7.37–7.55 (m, 7H, Ar-H), 7.62 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.66 (d, 2H,
J ¼ 8.4 Hz, Ar-H), 7.96 (d, 2H, J ¼ 8.4 Hz, Ar-H), 8.02 (d, 2H, J ¼ 8.4 Hz, Ar-H);
13C NMR (75 MHz, CDCl3) dC: 37.2, 44.8, 44.9, 126.7, 127.2, 127.3, 127.4, 128.1,

SYMMETRICAL AND UNSYMMETRICAL 1,5-DIKETONES
135
128.2, 128.5, 128.6, 128.7, 128.9, 133.1, 135.5, 136.8, 139.8, 143.8, 145.7, 198.2, 198.6.
Anal. calcd. for C29H24O2: C, 86.11; H, 5.98%. Found: C, 86.06; H, 5.95%.
1,5-Di(4-methylphenyl)-3-phenyl-1,5-pentanedione (3d). Isꢁo1lated as col-
orless solid; mp 110–111 ꢀC; IR (KBr): 3061, 3026, 2890, 1678 cm
;
1H NMR
(300 MHz, CDCl3) dH: 2.40 (s, 6H, 2CH3), 3.31 (dd, 2H, J ¼ 16.2, 6.9 Hz, CH2),
3.46 (dd, 2H, J ¼ 16.2, 6.9 Hz, CH2), 4.05 (qnt, 1H, J ¼ 6.9 Hz, CH), 7.25–7.28 (m,
9H, Ar-H), 7.83–7.90 (m, 4H, Ar-H); 13C NMR (75 MHz, CDCl3) dC: 21.6, 37.3,
44.8, 126.6, 127.4, 128.2, 128.6, 129.2, 129.6, 134.4, 143.8, 198.2. Anal. calcd. for
C25H24O2: C, 84.24; H, 6.79%. Found C, 84.21; H, 6.76%.
3-(4-Methylphenyl)-1,5-diphenyl-1,5-pentanedione (3e)[3b]. Isolated as
1
colorless solid; mp 106–107 ꢀC; IR (KBr): 3059, 3027, 2894, 1679 cmꢁ1; H NMR
(300 MHz, CDCl3) dH: 2.28 (s, 3H, CH3), 3.32 (dd, 2H, J ¼ 16.5, 7.2 Hz, CH2),
3.48 (dd, 2H, J ¼ 16.5, 7.2 Hz, CH2), 4.03 (qnt, 1H, J ¼ 7.2 Hz, CH), 7.08 (d, 2H,
J ¼ 8.1 Hz, Ar-H), 7.17 (d, 2H, J ¼ 8.1 Hz, Ar-H), 7.41–7.46 (m, 4H, Ar-H),
7.51–7.57 (m, 2H, Ar-H), 7.93–7.97 (m, 4H, Ar-H); 13C NMR (75 MHz, CDCl3)
dC: 21.0, 36.7, 45.0, 127.2, 128.1, 128.5, 129.3, 133.0, 136.1, 136.8, 140.7, 198.7.
3-(4-Methoxyphenyl)-1,5-diphenyl-1,5-pentanedione (3f)[3b]. Isolated as
1
colorless solid; mp 89–90 ꢀC; IR (KBr): 3056, 3025, 2895, 1676 cmꢁ1; H NMR
(300 MHz, CDCl3) dH: 3.31 (dd, 2H, J ¼ 16.5, 7.2 Hz, CH2), 3.47 (dd, 2H,
J ¼ 16.5, 7.2 Hz, CH2), 3.75 (s, 3H, OCH3), 4.02 (qnt, 1H, J ¼ 7.2 Hz, CH), 6.81
(d, 2H, J ¼ 8.7 Hz, Ar-H), 7.20 (d, 2H, J ¼ 8.7 Hz, Ar-H), 7.41–7.46 (m, 4H,
Ar-H), 7.51–7.57 (m, 2H, Ar-H), 7.93–7.96 (m, 4H, Ar-H); 13C NMR (75 MHz,
CDCl3) dC: 36.4, 45.1, 55.1, 113.9, 128.1, 128.4, 128.6, 133.0, 135.7, 136.8, 158.1,
198.7.
1-(4-Chlorophenyl)-3-(4-methylphenyl)-5-phenyl-1,5-pentanedione
(3g). Isolated as colorless solid; mp 59–60 ꢀC; IR (KBr): 3058, 3026, 2891, 1676,
;
1680 cmꢁ1 1H NMR (300 MHz, CDCl3) dH: 2.27 (s, 3H, CH3), 3.26 (dd, 1H,
J ¼ 16.8, 6.9 Hz, CH), 3.32 (dd, 1H, J ¼ 16.8, 6.9 Hz, CH), 3.46 (dd, 2H, J ¼ 16.5,
6.9 Hz, CH2), 4.00 (qnt, 1H, J ¼ 6.9 Hz, CH), 7.07 (d, 2H, J ¼ 7.8 Hz, Ar-H), 7.15
(d, 2H, J ¼ 7.8 Hz, Ar-H), 7.37–7.45 (m, 4H, Ar-H), 7.53 (t, 1H, J ¼ 7.2 Hz), 7.88
(d, 2H, J ¼ 7.5 Hz, Ar-H), 7.94 (d, 2H, J ¼ 7.5 Hz, Ar-H); 13C NMR (75 MHz,
CDCl3) dC: 21.0, 36.7, 44.8, 44.9, 127.2, 128.0, 128.5, 128.8, 129.3, 129.5, 133.1,
135.1, 136.2, 136.7, 139.4, 140.5, 197.4, 198.5. Anal. calcd. for C24H21ClO2: C,
76.49; H, 5.62%. Found: C, 76.43; H, 5.56%.
3-(4-Chlorophenyl)-1-(4-methylphenyl)-5-phenyl-1,5-pentanedione (3h).
Isolated as colorless solid; mp 112–113 ꢀC; IR (KBr): 3062, 3027, 2894, 1674,
;
1679 cmꢁ1 1H NMR (300 MHz, CDCl3) dH: 2.38 (s, 3H, CH3), 3.25 (dd, 1H,
J ¼ 16.5, 6.9 Hz, CH), 3.33 (dd, 1H, J ¼ 16.5, 6.9 Hz, CH), 3.42 (dd, 1H, J ¼ 16.8,
6.9 Hz, CH), 3.48 (dd, 1H, J ¼ 16.8, 6.9 Hz, CH), 4.05 (qnt, 1H, J ¼ 6.9 Hz, CH),
7.21 (s, 6H, Ar-H), 7.39–7.55 (m, 3H, Ar-H), 7.83 (d, 2H, J ¼ 7.2 Hz, Ar-H), 7.92
(d, 2H, J ¼ 7.2 Hz, Ar-H); 13C NMR (75 MHz, CDCl3) dC: 21.3, 36.4, 44.3, 44.4,
127.8, 128.0, 128.4(2C), 128.7, 129.0, 131.9, 132.9, 134.1, 136.6, 142.3, 143.7,
197.5, 197.9. Anal. calcd. for C24H21ClO2: C, 76.49; H, 5.62%. Found: C, 76.44;
H, 5.57%.

136
N. PAUL, M. J. SHANMUGAM, AND S. MUTHUSUBRAMANIAN
3-(4-Chlorophenyl)-1,5-di(4-methylphenyl)-1,5-pentanedione (3i). Isolated
as colorless solid; mp 108–109 ꢀC; IR (KBr): 3063, 3024, 2897, 1675 cmꢁ1; 1H NMR
(300 MHz, CDCl3) dH: 2.40 (s, 6H, 2CH3), 3.28 (dd, 2H, J ¼ 16.5, 6.9 Hz, CH2), 3.44
(dd, 2H, J ¼ 16.5, 6.9 Hz, CH2), 4.03 (qnt, 1H, J ¼ 6.9 Hz, CH), 7.22–7.26 (m, 8H,
Ar-H), 7.84 (d, 4H, J ¼ 7.8 Hz, Ar-H); 13C NMR (75 MHz, CDCl3) dC: 21.6, 36.6,
44.6, 128.2, 128.6, 128.9, 129.3, 132.2, 134.2, 142.4, 144.0, 197.9. Anal. calcd. for
C25H23ClO2: C, 76.81; H, 5.93%. Found: C, 76.75; H, 5.91%.
1,3-Di(4-chlorophenyl)-5-(4-methylphenyl)-1,5-pentanedione (3j). Iso-
lated as colorless solid; mp 101–102 ꢀC; IR (KBr): 3060, 3026, 2890, 1675,
;
1679 cmꢁ1 1H NMR (300 MHz, CDCl3) dH: 2.40 (s, 3H, CH3), 3.25 (dd, 1H,
J ¼ 16.5, 7.2 Hz, CH), 3.29 (dd, 1H, J ¼ 16.5, 7.2 Hz, CH), 3.43 (dd, 1H, J ¼ 16.5,
7.2 Hz, CH), 3.48 (dd, 1H, J ¼ 16.5, 7.2 Hz, CH), 4.02 (qnt, 1H, J ¼ 7.2 Hz, CH),
7.19–7.26 (m, 6H, Ar-H), 7.42 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.83 (d, 2H, J ¼ 8.1 Hz,
Ar-H), 7.88 (d, 2H, J ¼ 8.1 Hz, Ar-H); 13C NMR (75 MHz, CDCl3) dC: 21.6, 36.5,
44.5, 44.6, 128.2, 128.7, 128.8, 128.9, 129.3, 129.5, 132.3, 134.2, 134.9, 139.6,
142.1, 144.1, 197.1, 197.8. Anal. calcd. for C24H20Cl2O2: C, 70.08; H, 4.90%. Found
C, 70.06; H, 4.85%.
ACKNOWLEDGMENTS
The authors thank the Department of Science and Technology for funds under
the IRHPA program used for the high-resolution NMR spectrometer. Financial sup-
port from the University Grants Commission, New Delhi, to N.P. is gratefully
acknowledged.
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