A palladium catalyzed atom-efficient cross-coupling reactivity of triarylbismuths with α,β-unsaturated acyl chlorides

Article abstract of DOI:10.1016/j.jorganchem.2008.05.012

An atom-efficient cross-coupling reactivity of triarylbismuths (1 equiv) was demonstrated by cross-coupling reaction with 3 equiv of α,β-unsaturated acyl chlorides under palladium catalysis in the synthesis of a series of functionalized α, β-unsaturated ketones in high isolated yields.

Full text of DOI:10.1016/j.jorganchem.2008.05.012

Journal of Organometallic Chemistry 693 (2008) 2494–2498
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
A palladium catalyzed atom-efficient cross-coupling reactivity
of triarylbismuths with a,b-unsaturated acyl chlorides
*
Maddali L.N. Rao , Varadhachari Venkatesh, Deepak N. Jadhav
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, Uttar Pradesh, India
a r t i c l e i n f o
a b s t r a c t
Article history:
An atom-efficient cross-coupling reactivity of triarylbismuths (1 equiv) was demonstrated by cross-cou-
Received 17 March 2008
Received in revised form 3 May 2008
Accepted 6 May 2008
pling reaction with 3 equiv of
a series of functionalized , b-unsaturated ketones in high isolated yields.
Ó 2008 Elsevier B.V. All rights reserved.
a,b-unsaturated acyl chlorides under palladium catalysis in the synthesis of
a
Available online 13 May 2008
Keywords:
Cross-coupling
Palladium
Triarylbismuths
a
,b-Unsaturated acyl chlorides
Chalcones
Atom-efficient
1. Introduction
protocols often produce unwanted side reactions in the presence
of additional acid or base sensitive groups [4].
The palladium catalyzed Suzuki-type cross-coupling reaction of
acyl chlorides with organometallic reagents proceeds, in general,
smoothly to furnish excellent yields of ketones [1]. Incidentally,
The organobismuths are important class of organometallic com-
pounds [7] with low or non-toxicity and are easily available by
known procedures. Although, use of these reagents for C–C bond
formations under metal catalyzed conditions are limited at present
[7–10], the applications of these reagents for C–N, C–O bond for-
mations is well known in organic synthesis [7]. In our quest for
developing atom-efficient organometallic reagents for C–C bond
formations we recently uncovered a high reactivity of the triaryl-
bismuths in cross-coupling reactions with a variety of electrophilic
coupling partners under palladium catalysis [10]. In particular, we
have disclosed the high atom-efficient cross-coupling reactivity of
triarylbismuths with acid chlorides under palladium catalysis to
give both diaryl and alkyl aryl ketones [10a]. Although we initially
the similar coupling reaction of
with arylboronic acids has been reported to proceed only slug-
gishly leading to poor yields of ,b-unsaturated ketones, despite
a,b-unsaturated acyl chlorides
a
some reports showing the synthesis of one or two examples of
chalcones as part of cross-coupling study involving acyl chlorides
[1–3]. In fact, this poor reactivity of a,b-unsaturated acyl chlorides
led to the change of strategy for the synthesis of chalcones by
involving aroyl chlorides and stryrylboronic acids as electrophilic
and nucleophilic coupling partners respectively in Suzuki-type
cross-coupling reaction [2b]. Compounds containing chalcone
functionality are well known for their important medicinal proper-
ties in addition to their utility for a variety of transformations in
organic synthesis [4]. In principle, the direct cross-coupling of
surmised the possibility of cross-coupling of a,b-unsaturated acyl
chlorides with triarylbismuths in analogous manner, the reported
poor reactivity of the former under Suzuki-type coupling condi-
tions deterred us from exploring further. Our recent experience
and the realization of relative facile reactivity of triarylbismuths
with electrophilic coupling partners [10] spurred us return to this
a
,b-unsaturated acyl chlorides with organometallic reagent under
metal catalysis is an ideal and a facile pathway to access chalcones,
since ,b-unsaturated acyl chlorides are easily obtainable sub-
a
strates [5,6]. Indeed, the traditional method of preparation of chal-
cones via Claisen–Schmidt reaction or Friedel–Crafts acylation
study involving
muths under palladium catalysis. To our surprise, we discovered
that the cross-coupling reaction of a variety of ,b-unsaturated acyl
a,b-unsaturated acyl chlorides with triarylbis-
a
chlorides with triarylbismuths is very facile and more efficient
under palladium catalyzed conditions. Herein, we report the
* Corresponding author. Tel./fax: +91 512 259 7532.
E-mail address: maddali@iitk.ac.in (M.L.N. Rao).
first versatile reactivity of
a,b-unsaturated acyl chlorides with
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.05.012

M.L.N. Rao et al. / Journal of Organometallic Chemistry 693 (2008) 2494–2498
2495
triarylbismuths under palladium catalysis for the facile synthesis
of diversely-substituted ,b-unsaturated ketones.
good conversion (entry 17). From this, it was emerged that the
cross-coupling reaction of triphenylbismuth (1 equiv) with model
substrate cinnamoyl chloride (4 equiv) was atom-efficient in 1,4-
dioxane solvent with triethylamine (1 equiv) under palladium
catalysis. This is very significant, as the corresponding reactivity
a
2. Results and discussion
of a,b-unsaturated acyl chloride was reported to be poor under Su-
As the reactivity of
type coupling conditions reported to be inefficient [2b], we were
tempted to screen the reactivity of ,b-unsaturated acyl chlorides
a,b-unsaturated acyl chlorides under Suzuki-
zuki-type coupling conditions [2b]. Hence, it is remarkable that the
present palladium catalyzed protocol is high yielding and atom-
efficient as 1 equiv of triphenylbismuth could effectively cross-
a
with triarylbismuths under similar conditions to our earlier
palladium protocol for acyl chlorides [10a]. So, for the initial study
we have carried out cross-coupling reaction of cinnamoyl chloride
with triphenylbismuth in the presence of PdCl2/PPh3 catalytic
system under different solvent, base conditions and the results are
summarized in Table 1. From this study, it was found that the
cross-coupling reaction produced moderate conversion in N,N-
dimethylacetamide (DMA), 1,2-dimethoxyethane (DME), N,N-
dimethylformamide (DMF) and tetrahydrofuran (THF) solvents
(entries 1–4). Under similar conditions, the conversion was good
in acetonitrile and 1,4-dioxane solvents furnishing 69–71% of iso-
lated yields of chalcone (entries 5–6). Additional screening in the
presence of inorganic bases produced 69–79% (entries 7–10), while
pyridine as a base produced 66% conversion under similar condi-
tions (entry 11). As a result, triethylamine found to be more suitable
and produced conversion up to 91% with 78% of the isolated yield of
chalcone (entry 12). A control reaction carried out in the absence of
palladium catalytic system but with triethylamine produced chal-
cone as cross-coupled product in 31% isolated yield (entry 13).
Another control reaction performed in the absence of both pal-
ladium catalyst and triethylamine produced 21% isolated yield of
the product (entry 14). Further, it was found that triethylamine
(1 equiv) is sufficient to obtain good cross-coupling conversion
(entries 12, 15 and 16). Further, a control reaction carried out with-
out triphenylphosphine furnished 46% of cross-coupled chalcone
revealing that the ligand is necessary for coupling reaction to yield
couple with 3 equiv of
obtainable conditions.
Hence, to further broaden the scope and versatility of this reac-
tion, a variety of electronically divergent ,b-unsaturated acyl
chlorides were employed for cross-coupling reaction with different
triarylbismuths under standardized conditions (Table 2). The
cross-coupling reaction of
ferent triarylbismuths proved to be efficient furnishing excellent
yields of the corresponding functionalized ,b-unsaturated ke-
tones. For example, the cross-coupling reaction of cinnamoyl chlo-
ride with three different triarylbismuths produced chalcones in
78–85% isolated yields (entries 1–3). Similarly, the other cinnam-
oyl chlorides with electron-rich substituents such as p-methyl,
p-methoxy, m-methoxy groups delivered high yields of the corre-
sponding chalcones (entries 4–12). Cinnamoyl chlorides having -
chloro substituent in -ortho, -meta and -para positions furnished
the corresponding chalcones in good to high yields (entries 13–
21). Further, the cross-coupling reaction of p-bromo and m-bro-
mo-cinnamoyl chlorides were found to be chemoselective giving
the corresponding chalcones in good yields (entries 22–27). The
reactivity of 3-furan-2-yl-acryloyl chloride was found to be excel-
lent with different triarylbismuths furnishing the corresponding
conjugated ketones in 79–86% yields (entries 28–30). The cross-
coupling reaction of electron-deficient cinnamoyl chloride with -
nitro substituent furnished the corresponding chalcone in 64%
yield (entry 31). Overall, it was demonstrated that the reactivity
of both electron-rich and -deficient cinnamoyl chlorides fared well
in cross-coupling reaction with different triarylbismuths giving
a,b-unsaturated acyl chlorides under easily
a
a,b-unsaturated acyl chlorides with dif-
a
Table 1
Screening conditionsa
good to excellent yields of variety of functionalized
rated ketones.
a,b-unsatu-
O
O
Cat. PdCl2 / PPh3
Cl
3
BiPh3
3
+
3. Conclusion
base, 80 oC, solvent
In conclusion, we have demonstrated the versatile atom-effi-
cient reactivity of triarylbismuths with ,b-unsaturated acyl chlo-
Conv. (%)b,c
a
Entry
Solvent
Base (equiv)
t/h
ride under palladium catalyzed conditions. This study is very
significant as the similar high reactivity was not known before
with electronically divergent a,b-unsaturated acyl chlorides under
Suzuki-type cross-coupling conditions. Additional advantage asso-
1
2
3
4
5
6
7
8
DMA
DMF
DME
THF
NEt3 (1)
NEt3 (1)
NEt3 (1)
NEt3 (1)
NEt3 (1)
NEt3 (1)
K3PO4 (1)
Cs2CO3 (1)
K2CO3 (1)
Na2CO3 (1)
Pyridine (1)
NEt3 (1)
NEt3 (1)
–
2
2
2
2
2
2
4
4
4
4
4
4
4
4
4
4
4
42
60
47
66
84 (71)
85 (69)
79 (62)
71
69
71
CH3CN
ciated with the present method is that 1 equiv of triarylbismuth
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
could be effectively cross-couple with 3 equiv of
a,b-unsaturated
acyl chloride. This will reduce the organometallic reagent loadings
to 1/3 amount effectively in bulk scale operations in such coupling
reactions. As triarylbismtuhs are readily accessible using standard
procedures, the present palladium catalyzed protocol provides an
9
10
11
12
13
14
15
16
17
66
91 (78)
(31)d
(21)e
73 (51)f
81 (76)
55 (46)g
easy access to a library of divergent
high yields. Hence, we believe that the first atom-efficient cross-
coupling reaction of triarylbismuths with ,b-unsaturated acyl
a,b-unsaturated ketones in
–
a
NEt3 (3)
NEt3 (1)
chloride reported here would further encourage the use of triaryl-
bismuths as atom-efficient organometallic reagents for C–C bond
formations in organic synthesis.
a
Equivalent ratios: BiPh3 (1 equiv); PdCl2 (9 mol%)/PPh3 (18 mol%), cinnamoyl
chloride (4.0 equiv), 80 °C.
b
Based on GC analysis.
Isolated yields are given in parentheses.
Control without PdCl2/PPh3.
Control without PdCl2/PPh3 and NEt3.
Control without NEt3.
Control without PPh3.
c
4. Experimental
d
e
f
General: All reactions were carried out in Schlenk tubes
under nitrogen atmosphere using anhydrous organic solvents.
g

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M.L.N. Rao et al. / Journal of Organometallic Chemistry 693 (2008) 2494–2498
Table 2
Cross-coupling reaction of triarylbismuths with
a,b-unsaturated acyl chlorides
O
O
[Pd]
Ar
3
Bi
R
3
+
Cl
Ar
3
R
Entry
ArCH@CHCOCl
a
,b-Unsaturated ketone
R
Yield (%)a,b
Ref.
1
2
3
1a
2a
3a
R = H
R = CH3
R = OCH3
78
85
81
[11a]
[11a]
[11a]
O
O
Cl
R
O
O
4
5
6
4a
5a
6a
R = H
R = CH3
R = OCH3
83
78
76
[11a]
[11b]
[11c]
Cl
H3C
H3C
R
O
O
7
8
9
7a
8a
9a
R = H
R = CH3
R = OCH3
80
87
90
[11d]
[11e]
[11f]
Cl
H3CO
H3CO
R
O
O
Cl
10
11
12
10a
11a
12a
R = H
R = CH3
R = OCH3
84
83
85
[12a]
–
[12b]
R
OCH3
OCH3
O
O
13
14
15
13a
14a
15a
R = H
R = CH3
R = OCH3
91
90
86
[12c]
[12d]
[11f]
Cl
Cl
Cl
R
O
O
O
O
Cl
Cl
16
17
18
16a
17a
18a
R = H
R = CH3
R = OCH3
81
79
81
[12e]
[12f,13a]
[12e,12f]
R
R
Cl
Cl
19
20
21
19a
20a
21a
R = H
R = CH3
R = OCH3
71
74
69
[11e]
[11e]
[13b]
Cl
Cl
O
O
22
23
24
22a
23a
24a
R = H
R = CH3
R = OCH3
80
75
75
[13c]
–
–
Cl
Br
Br
R
O
O
O
O
Cl
Cl
25
26
27
25a
26a
27a
R = H
R = CH3
R = OCH3
72
71
78
[13d,13e]
[12e]
[12e]
R
R
Br
O
Br
O
28
29
30
28a
29a
30a
R = H
R = CH3
R = OCH3
79
86
84
[13d,13f,13g]
[13f,13g]
[13f,13g]

M.L.N. Rao et al. / Journal of Organometallic Chemistry 693 (2008) 2494–2498
2497
[13h]
Table 2 (continued)
O
O
31
31a
R = H
64
Cl
O2N
Condition: BiAr3 (1 equiv),
O2N
R
a
a
,b-unsaturated acyl chloride (4 equiv), PdCl2 (9 mol%)/PPh3 (18 mol%), Et3N (1 equiv), 1,4-dioxane (3 mL), 80 °C, 4 h.
b
Isolated yields after column chromatography w.r.t BiAr3.
1,4-Dioxane was freshly distilled over sodium-benzophenone ketyl
prior to use and purged with nitrogen gas. All other solvents where
ever used were purified by standard procedures.
2H, J = 8.6 Hz, CHar); 13C NMR (100 MHz, CDCl3): d 55.2, 113.3,
116.2, 121.0, 122.3, 128.4, 128.5, 129.9, 132.7, 136.2, 138.1,
144.7, 159.8, 190.4; IR mmax (KBr, cmÀ1): 1663; HRMS (ES+) for
(M+H) C16H15O2 calcd: 239.1072; found: 239.1070.
3-(3-Methoxyphenyl)-1-(4-methylphenyl)-(2E)-2-propen-1-one,
11a: m.p. 65–67 °C; 1H NMR (400 MHz, CDCl3): d 2.36 (s, 3H, CH3),
3.78 (s, 3H, OCH3), 6.88-6.90 (m, 1H, CHar), 7.08 (s, 1H, CHar),
7.16–7.28 (m, 4H, CHar), 7.42–7.46 (d, 1H, J = 15.6 Hz, –CH@CH–
C@O), 7.67–7.71 (d, 1H, J = 15.6 Hz, –CH@CH–C@O), 7.85–7.87 (d,
2H, J = 8.3 Hz, CHar); 13C NMR (100 MHz, CDCl3): d 21.6, 55.2,
113.3, 116.1, 120.9, 122.3, 128.6, 129.2, 129.8, 135.5, 136.3,
143.6, 144.2, 159.8, 189.9; IR mmax (KBr, cmÀ1): 1662; HRMS (ES+)
for (M+H) C17H17O2 calcd: 253.1229; found: 253.1220.
Silica gel 60–120 (Acme, Mumbai) was used to perform column
chromatography using ethyl acetate/petroleum ether as an eluent
system. Aluminium sheets coated with silica gel 60 F254 (Merck)
were used to perform thin layer chromatography (TLC) and were
visualized under UV lamp. Melting points measured using JSGW
melting point apparatus (Jain Scientific Glass Works, Ambala cantt,
India) were uncorrected. The IR spectra were recorded on a Bruker
vector 22 FT-IR spectrophotometer. The 1H and 13C NMR spectra
were recorded on a JEOL-Lambda (400 MHz) spectrometer using
CDCl3 as a solvent. The chemical shifts (d) are quoted in parts per
million (ppm). The coupling constants (J) are reported in Hertz
3-(4-Chlorophenyl)-1-(4-methoxyphenyl)-(2E)-2-propen-1-one,
15a: m.p. 129–131 °C; 1H NMR (400 MHz, CDCl3): d 3.81 (s,
3H, OCH3), 6.89–6.92 (d, 2H, J = 8.8 Hz, CHar), 7.29–7.31 (d, 2H,
J = 8.3 Hz, CHar), 7.42–7.46 (d, 1H, J = 15.6 Hz, –CH@CH–C@O),
7.48–7.50 (d, 2H, J = 8.3 Hz, CHar), 7.65–7.69 (d, 1H, J = 15.6 Hz,
–CH@CH–C@O), 7.95–7.97 (d, 2H, J = 8.8 Hz, CHar); 13C NMR
(100 MHz, CDCl3): d 55.4, 113.8, 122.2, 129.1, 129.4, 130.7, 130.8,
(Hz).
a,b-Unsaturated acyl chlorides were prepared using the re-
ported procedures [6]. Triarylbismuths were prepared using stan-
dard protocols [7]. GC analysis of the crude reaction mixtures
was performed using Perkin–Elmer (Clarus 500) Gas Chromato-
graph. High resolution mass spectra were recorded using electro-
spray (ES) technique on Waters HAB213 Q-Tof Premier Micro
mass spectrometer.
133.5, 136.1, 142.3, 163.5, 188.3; IR m
max (KBr, cmÀ1): 1653; HRMS
(ES+) for (M+H) C16H14ClO2 calcd: 273.0682; found: 273.0687.
3-(3-Chlorophenyl)-1-phenyl-(2E)-2-propen-1-one, 16a: m.p.
68–70 °C [lit. 70 °C]; 1H NMR (400 MHz, CDCl3): d 7.25–7.31 (m,
2H, CHar), 7.40–7.55 (m, 6H, CHar and –CH@CH–C@O), 7.63–7.67
(d, 1H, J = 15.6 Hz, –CH@CH–C@O), 7.93–7.95 (d, 2H, J = 7.8 Hz,
CHar); 13C NMR (100 MHz, CDCl3): d 123.2, 126.7, 127.8, 128.5,
128.6, 130.1, 130.2, 132.9, 134.9, 136.7, 137.8, 142.9, 190.0; IR mmax
(KBr, cmÀ1): 1664; HRMS (ES+) for (M+H) C15H12ClO calcd:
243.0577; found: 243.0573.
3-(3-Chlorophenyl)-1-(4-methylphenyl)-(2E)-2-propen-1-one,
17a: m.p. 73–75 °C [lit. 80 °C]; 1H NMR (400 MHz, CDCl3): d 2.36 (s,
3H, CH3), 7.22-7.24 (d, 2H, J = 8.0 Hz, CHar), 7.26–7.28 (d, 2H,
J = 7.6 Hz, CHar), 7.40–7.47 (m, 2H, CHar and –CH@CH–C@O), 7.55
(s, 1H, CHar), 7.62–7.66 (d, 1H, J = 15.6 Hz, –CH@CH–C@O), 7.85–
7.87 (d, 2H, J = 8.3 Hz, CHar); 13C NMR (100 MHz, CDCl3): d 21.6,
123.2, 126.7, 127.8, 128.6,129.3, 130.1, 130.1, 134.9, 135.3, 136.8,
142.5, 143.8, 189.4; IR mmax (KBr, cmÀ1): 1663; HRMS (ES+) for
(M+H) C16H14ClO calcd: 257.0733, found: 257.0732.
4.1. Representative procedure
In a typical experiment, an oven-dried Schlenk tube under
nitrogen atmosphere was charged with cinnamoyl chloride
(0.166 g, 1 mmol), BiPh3 (0.11 g, 0.25 mmol), PdCl2 (0.004 g,
0.023 mmol), PPh3 (0.012 g, 0.045 mmol) and Et3N (0.025 g,
0.25 mmol) followed by the addition of anhydrous 1,4-dioxane
(3 mL) and the contents were heated at 80 °C for 4 h. Then, the
reaction mixture was cooled to room temperature and quenched
with water and extracted with ethyl acetate (2 Â 15 mL). The com-
bined ethyl acetate extract was washed with dilute HCl (5 mL), sat-
urated sodium bicarbonate solution (5 mL), brine (2 Â 5 mL) and
dried over MgSO4. The crude product mixture thus obtained after
removing the solvent was subjected to column chromatography
and the pure chalcone was isolated in 78% yield with respect to tri-
arylbismuth used. The product was characterized by 1H NMR, 13C
NMR, IR and mass spectral analysis.
3-(3-Chlorophenyl)-1-(4-methoxyphenyl)-(2E)-2-propen-1-one,
18a: m.p. 102–104 °C [lit. 95 °C]; 1H NMR (400 MHz, CDCl3): d 3.82
(s, 3H, OCH3), 6.90-6.92 (d, 2H, J = 8.8 Hz, CHar), 7.25–7.27 (d, 2H,
J = 7.8 Hz, CHar), 7.41–7.42 (m, 1H, CHar), 7.44–7.48 (d, 1H,
J = 15.6 Hz, –CH@CH–C@O), 7.55 (s, 1H, CHar),7.63–7.66 (d, 1H,
J = 15.6 Hz, –CH@CH–C@O), 7.95–7.98 (d, 2H, J = 8.8 Hz, CHar); 13C
NMR (100 MHz, CDCl3): d 55.4, 113.8, 123.0, 126.7, 127.7, 130.0,
130.1, 130.7, 130.8, 134.8, 136.9, 142.1, 163.5, 188.1; IR mmax
(KBr, cmÀ1): 1661; HRMS (ES+) for (M+H) C16H14ClO calcd:
273.0682; found: 273.0681.
3-(2-Chlorophenyl)-1-(4-methoxyphenyl)-(2E)-2-propen-1-one,
21a: m.p. 74–76 °C; 1H NMR (400 MHz, CDCl3): d 3.81 (s, 3H,
OCH3), 6.89–6.92 (d, 2H, J = 8.8 Hz, CHar), 7.22–7.26 (m, 2H, CHar),
7.35–7.37 (m, 1H, CHar), 7.39–7.43 (d, 1H, J = 15.6 Hz, –CH@CH–
C@O), 7.65–7.68 (m, 1H, CHar), 7.94-7.97 (d, 2H, J = 9.0 Hz, CHar),
8.06–8.10 (d, 1H, J = 15.6 Hz, –CH@CH–C@O); 13C NMR (100 MHz,
4.2. Spectral data
1,3-Bis(4-methoxyphenyl)-(2E)-2-propen-1-one, 9a: m.p. 94–
96 °C; 1H NMR (400 MHz, CDCl3): d 3.83 (s, 3H, OCH3), 3.86 (s,
3H, OCH3), 6.90–6.96 (m, 4H, CHar), 7.39–7.43 (d, 1H, J = 15.6 Hz,
–CH@CH–C@O), 7.57–7.59 (d, 2H, J = 8.8 Hz, CHar), 7.74–7.78 (d,
1H, J = 15.6 Hz, –CH@CH–C@O), 8.00–8.02 (d, 2H, J = 8.8 Hz, CHar);
13C NMR (100 MHz, CDCl3): d 55.3, 55.4, 113.7, 114.3, 119.4, 127.7,
130.0, 130.3, 130.6, 131.2, 143.7, 161.4, 163.2, 188.7; IR mmax (KBr,
cmÀ1): 1655; HRMS (ES+) for (M+H) C17H17O3 calcd: 269.1178;
found: 269.1176.
3-(3-Methoxyphenyl)-1-phenyl-(2E)-2-propen-1-one,
10a:
m.p. 49–51 °C; 1H NMR (400 MHz, CDCl3): d 3.77 (s, 3H, OCH3),
6.87–6.90 (m, 1H, CHar), 7.07–7.53 (m, 7H, CHar and –CH@CH–
C@O), 7.67–7.71 (d, 1H, J = 15.6 Hz, –CH@CH–C@O), 7.93–7.95 (d,

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M.L.N. Rao et al. / Journal of Organometallic Chemistry 693 (2008) 2494–2498
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(b) Y. Han, L. Fang, W.-T. Tao, Y.-Z. Huang, Tetrahedron Lett. 36 (1995)
1287;
CDCl3): d 55.4, 113.6, 113.8, 124.7, 127.0, 127.7, 130.2, 130.8,
130.9, 133.4, 135.3, 139.7, 163.5, 188.6; IR mmax (KBr, cmÀ1):
1660; HRMS (ES+) for (M+H) C16H14ClO2 calcd: 273.0682; found:
273.0681.
3-(4-Bromophenyl)-1-(4-methylphenyl)-(2E)-2-propen-1-one,
23a: m.p. 149–151 °C; 1H NMR (400 MHz, CDCl3): d 2.36 (s, 3H,
CH3), 7.21–7.23 (d, 2H, J = 8.0 Hz, CHar), 7.41–7.53 (m, 5H, CHar
and –CH@CH–C@O), 7.63–7.67 (d, 1H, J = 15.6 Hz, –CH@CH–
C@O), 7.84–7.86 (d, 2H, J = 8.3 Hz, CHar); 13C NMR (100 MHz,
CDCl3): d 21.6, 122.5, 124.6, 128.6, 129.3, 129.7, 132.1, 133.9,
135.4, 142.8, 143.8, 189.6; IR mmax (KBr, cmÀ1): 1657; HRMS (ES+)
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for (M+H)
C16H14BrO calcd: 301.0228; found: 301.0224 and
(M+2+H) C16H14BrO calcd: 303.0228; found: 303.0202.
3-(4-Bromophenyl)-1-(4-methoxyphenyl)-(2E)-2-propen-1-one,
24a: m.p. 137–139 °C; 1H NMR (400 MHz, CDCl3): d 3.81 (s, 3H,
OCH3), 6.89–6.91 (d, 2H, J = 8.6 Hz, CHar), 7.41–7.53 (m, 5H, CHar
and –CH@CH–C@O), 7.63–7.67 (d, 1H, J = 15.6 Hz, –CH@CH–
C@O), 7.94–7.96 (d, 2H, J = 8.3 Hz, CHar); 13C NMR (100 MHz,
CDCl3): d 54.4, 113.8, 122.3, 124.4, 129.6, 130.7, 132.1, 133.9,
142.4, 163.5, 188.3; IR mmax (KBr, cmÀ1): 1656; HRMS (ES+) for
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(M+H)
C16H14BrO2 calcd: 317.0177; found: 317.0175 and
(M+2+H) C16H14BrO2 calcd: 319.0177; found: 319.0165.
3-(3-Bromophenyl)-1-(4-methylphenyl)-(2E)-2-propen-1-one,
26a: m.p. 100–102 °C [lit. 80 °C]; 1H NMR (400 MHz, CDCl3): d 2.36
(s, 3H, CH3), 7.18–7.24 (m, 3H, CHar), 7.42–7.47 (m, 3H, CHar and
–CH@CH–C@O), 7.61–7.65 (d, 1H, J = 15.6 Hz, –CH@CH–C@O),
7.71 (s, 1H, CHar), 7.85–7.87 (d, 2H, J = 8.3 Hz, CHar); 13C NMR
(100 MHz, CDCl3): d 21.6, 123.0, 123.2, 127.2, 128.6, 129.3, 130.4,
130.7, 133.0, 135.2, 137.0, 142.4, 143.9, 189.4; IR mmax (KBr,
cmÀ1): 1664; HRMS (ES+) for (M+H) C16H14BrO calcd: 301.0228;
found: 301.0226 and (M+2+H) C16H14BrO calcd: 303.0228; found:
303.0211.
3-(3-Bromophenyl)-1-(4-methoxyphenyl)-(2E)-2-propen-1-one,
27a: m.p. 106–108 °C [lit. 108 °C]; 1H NMR (400 MHz, CDCl3): d
3.81 (s, 3H, OCH3), 6.90–6.92 (d, 2H, J = 8.8 Hz, CHar), 7.19–7.23
(m, 1H, CHar), 7.43–7.47 (m, 3H, CHar and CH@CH–C@O), 7.61–
7.65 (d, 1H, J = 15.6 Hz, –CH@CH–C@O), 7.71 (s, 1H, CHar), 7.95–
7.97 (d, 2H, J = 8.8 Hz, CHar); 13C NMR (100 MHz, CDCl3): d 55.4,
113.8, 123.0, 123.0, 127.1, 130.3, 130.6, 130.7, 130.8, 132.9,
137.2, 142.0, 163.5, 188.1; IR mmax (KBr, cmÀ1): 1660; HRMS (ES+)
for (M+H) C16H14BrO2 calcd: 317.0177; found: 317.0170 and
(M+2+H) C16H14BrO2 calcd: 319.0177; found: 319.0153.
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Acknowledgements
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The authors thank DST and IIT-Kanpur for financial support.
V.V. and D.N.J thank UGC, India and CSIR, India respectively, for
research fellowships.
(c) C. Peppe, R.P. das Chagas, J. Organomet.Chem. 691 (2006) 5856;
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