Selenoether ligand assisted Heck catalysis

Article abstract of DOI:10.1016/j.jorganchem.2011.03.047

Selenoether ligands, 2,2′-methylenebis(selanediyl)bis(2,1-phenylene) dimethanol (5), (2,2′-(ethane-1,2-diylbis(selanediyl))bis(2,1-phenylene)) dimethanol (6) and (2-(benzylselanyl)phenyl)methanol (7) have been synthesized by reducing di-o-formylphenyl diselenide and reacting the in situ generated selenolate with dibromomethane, 1,2-dibromoethane and benzyl chloride, respectively. The ligands, bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl) phenylselanyl)methane (8) and 1,2-bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl) phenylselanyl)ethane (9) have been synthesized similarly from bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide using electrophiles dibromomethane and 1,2-dibromoethane, respectively. Activity of ligands 5-9 along with 2-(2-(benzylselanyl)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (10) and 1-(2-(benzylselanyl)phenyl)-N,N-dimethylmethanamine (11) were examined for the Heck reaction of aryl halides with olefins. Bidentate Se,N ligand 11 was found to be the best one in the series and constitutes an efficient phosphine-free catalytic system with PdCl₂. The catalytic system showed moderate activity for the coupling of activated aryl chlorides in the presence of tetra-n-butyl ammonium bromide (TBAB). Complexes [10-PdCl₂] (12) and [11-PdCl₂] (13) have shown marginally better activity in comparison to the in situ generated catalysts from PdCl₂ and 10 and 11, respectively in the coupling of 4-bromoacetophenone with n-butylacrylate. Ligand 9 and complex 13 have been characterized by single crystal X-ray diffraction analysis.

Full text of DOI:10.1016/j.jorganchem.2011.03.047

Journal of Organometallic Chemistry 696 (2011) 2559e2564
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Selenoether ligand assisted Heck catalysis
,
b
Tapash Chakraborty a, Kriti Srivastava a, Harkesh B. Singh a , Ray J. Butcher
*
a Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
b Department of Chemistry, Howard University, Washington, DC 20059, USA
a r t i c l e i n f o
a b s t r a c t
Selenoether ligands, 2,20-methylenebis(selanediyl)bis(2,1-phenylene)dimethanol (5), (2,20-(ethane-1,
2-diylbis(selanediyl))bis(2,1-phenylene))dimethanol (6) and (2-(benzylselanyl)phenyl)methanol (7) have
been synthesized by reducing di-o-formylphenyl diselenide and reacting the in situ generated selenolate
with dibromomethane, 1,2-dibromoethane and benzyl chloride, respectively. The ligands, bis(2-(4,
4-dimethyl-4,5-dihydrooxazol-2-yl)phenylselanyl)methane (8) and 1,2-bis(2-(4,4-dimethyl-4,5-dihy-
drooxazol-2-yl)phenylselanyl)ethane (9) have been synthesized similarly from bis[2-(4,4-dimethyl-2-
oxazolinyl)phenyl] diselenide using electrophiles dibromomethane and 1,2-dibromoethane, respectively.
Activity of ligands 5e9 along with 2-(2-(benzylselanyl)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (10)
and 1-(2-(benzylselanyl)phenyl)-N,N-dimethylmethanamine (11) were examined for the Heck reaction
of aryl halides with olefins. Bidentate Se,N ligand 11 was found to be the best one in the series and
constitutes an efficient phosphine-free catalytic system with PdCl2. The catalytic system showed
moderate activity for the coupling of activated aryl chlorides in the presence of tetra-n-butyl ammonium
bromide (TBAB). Complexes [10-PdCl2] (12) and [11-PdCl2] (13) have shown marginally better activity in
comparison to the in situ generated catalysts from PdCl2 and 10 and 11, respectively in the coupling of
4-bromoacetophenone with n-butylacrylate. Ligand 9 and complex 13 have been characterized by single
crystal X-ray diffraction analysis.
Article history:
Received 9 January 2011
Received in revised form
18 March 2011
Accepted 29 March 2011
Keywords:
Selenoether
Selenide
Heck reaction
Palladium
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
Among the recent examples are amino acids [21], benzothiazoles
[22], imidazolines [23], phenylureas [24], pyridylpyrazoles [25],
Palladium catalyzed arylation or vinylation of olefins, known as
the Heck or the MizorokieHeck reaction, has evolved as a powerful
tool in organic synthesis for CeC bond formation [1e14]. A
conventional Heck reaction involves coupling of an aryl halide and
a terminal olefin bearing an electron withdrawing group catalyzed
by 1e5 mol% of a palladium catalyst in presence of a phosphine
ligand and a suitable base [15e18]. However, the phosphine ligands
are generally expensive and air-sensitive. A number of phosphine-
free catalysts have been employed in the Heck reaction. Among
them the palladacycle catalysts [19] and N-heterocyclic carbene
(NHC) ligands [20] have shown excellent activity. Other phosphine-
free catalyst systems involve nitrogen, oxygen and sulfur ligated
complexes of palladium either as preformed catalysts or as in situ
catalysts generated from an added ligand and a suitable palladium
precursor. Although not much explored, these types of ligands have
been shown to have interesting applications in the Heck reaction.
and thiadiazolidine-1-oxides [26].
The use of selenium containing ligands in the Heck reaction is
much rarer. Recently, the use of selenium ligated palladacycles and
palladium complexes in the Heck reaction has shown great
potential [27]. These catalysts (1ae1c, Chart 1) are reported to
outperform the phosphorus and sulfur ligated catalysts including
the best in the business like Herrmann palladacycle [28] and Mil-
stein’s catalysts [29]. Recently, Singh and co-workers have used
palladium complexes of SeNSe pincer ligands (2a, 2b, Chart 2) and
selenoe and telluroether ligands containing benzotriazole moiety
in the Heck and SuzukieMiyaura coupling reactions [30,31]. More
recently, they have demonstrated that air and moisture stable
palladacycle generated from Se,N ligand in the SuzukieMiayura
coupling reactions show high catalytic activity [32]. We envisaged
that the use of bidentate or tetradentate, heteroleptic selenoether
ligands incorporating nitrogen or oxygen can show interesting
catalytic properties in the Heck reaction. Herein, we report the
synthesis of selenoether ligands derived from di-o-formylphenyl
diselenide [33] and bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] dis-
elenide [34]. Utility of these ligands and other related ligands in the
Heck reaction is described.
* Corresponding author. Tel.: þ91 22 2576 7190; fax: þ91 22 2576 7152.
E-mail addresses: tapashc@gmail.com (T. Chakraborty), akriti@chem.iitb.ac.in
(K. Srivastava), chhbsia@chem.iitb.ac.in (H.B. Singh).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.03.047

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T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2559e2564
Cl
OAc
tBuSe Pd
OH
O
(i)
Cl
Pd
Cl
2
Ph
Se Pd SePh
Se
Se
(ii)/(iii)/(iv)
)
)
Se
Se
R
n
2
5
, n = 2, R = -CH2-, (ii)
6, n = 2, R = -CH2CH2-, (iii)
3
1a
1b
Chart 1. Selenium ligated catalysts.
1c
7
, n = 1, R = PhCH2-, (iv)
O
O
N
N
(i)
(ii)/(iii)/(iv)
)
)
R
n
Se
Se
2. Results and discussion
2
8, n = 2, R = -CH2-, (ii)
4
9
2.1. Synthesis of ligands
, n = 2, R = -CH2CH2-, (iii)
10, n = 1, R = PhCH2-, (iv)
Selenoether ligands 5e9 were synthesized by reducing the
diselenides viz. di-o-formylphenyl diselenide (3) [33] and bis[2-
(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide (4) [34] with NaBH4
and reacting the resulting selenolates with various electrophiles
shown in Scheme 1. The newly synthesized ligands were charac-
terized by elemental analysis and NMR (1H, 13C and 77Se) spec-
troscopy. The 77Se NMR spectroscopic data are given in the
following table (Table 1).
NMe2
Se )2
(i)
NMe2
(iv)
SeCH2Ph
11
Scheme 1. (i) NaBH4, EtOH; (ii) CH2Br2, (iii) Br(CH2)2Br, (iv) PhCH2Cl.
2.3. Crystallographic studies
The eOH peak in the 1H NMR spectrum of 5 in CDCl3 appeared
as a broad band at
NMR spectrum of 7 appeared as a sharp triplet at
d
2.34 ppm. However, the eOH peak in the 1H
2.3.1. Molecular structure of 9
d
1.91 ppm in
The molecular structure of 9 is shown in Fig. 1. The geometry
around the two selenium atoms is V-shaped. The intramolecular
Se/N distance (2.830 Å) is less than the sum of their van der Waals
radii (3.40 Å) [36] showing significant secondary bonding interac-
tion and is comparable with the Se/N distances observed in [2-
(4,4-dimethyl-2-oxazolinyl)phenyl]benzyl selenide (2.798 Å) [35]
and bis[2-(4,4-dimethyl-2- oxazolinyl)phenyl]diselenide (2.819 Å,
2.705 Å) [34]. Seleniumecarbon(sp2) distance, SeeC1 [1.9141(18)
Å] is shorter than the seleniumecarbon(sp3) distance, SeeC
[1.9652(17) Å] and also shorter than the corresponding distances in
[2-(4,4-dimethyl-2-oxazolinyl)phenyl]benzyl selenide [1.916(3) Å]
and bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl]diselenide [1.946(9)
Å, 1.940(9) Å]. Torsion angles, C1eSeeCeCi [172.50(15)ꢀ],
CeSeeC1eC6 [174.96(13)ꢀ], CeSeeC1eC2 [e5.30(15)ꢀ] are close to
180ꢀ or 0ꢀ showing the molecule to be almost planar.
CDCl3. The reason may be the presence of strong intramolecular
interaction in this case. The chemical shifts in the 77Se NMR spectra
of the ligands 5e7 [
upfield shift with respect to the parent diselenide 3 (
[33]. Similarly, the 77Se chemical shift of the ligands 8 (
d 287 (5), 280 (6) and 320 ppm (7)] showed an
d
468 ppm)
d
325) and 9
(350 ppm) showed an upfield shift with respect to the parent dis-
elenide 4 ( 454 ppm) [34]. Ligands 10 and 11 were prepared by
d
reducing the corresponding diselenides with NaBH4 and reacting
the resulting selenolates with PhCH2Cl. This represents a minor
modification of the reported method for synthesis of the ligands
where they were synthesized from the selenolates, generated in
situ from the ortho-lithiated derivatives [35].
2.2. Synthesis of complexes
Palladium complexes 12 and 13 were synthesized as shown in
Scheme 2. The complexes were obtained by stirring the ligands
and metal precursor at room temperature. Any unreacted metal
precursor was separated from the synthesized complexes by
crystallizing from dichloromethane/hexane. The complexes were
characterized by 1H and 77Se NMR spectroscopy and elemental
2.3.2. Molecular structure of 13
The molecular structure is depicted in Fig. 2. The geometry
around the palladium center is distorted square planar with the
four coordinations being defined by selenium, nitrogen and two cis-
chloro donors. Trans-angle, Cl1ePdeSe [169.79(2) Å] deviates more
than the other angle, NePdeCl2 [176.53(7) Å] from linearity. The
bite angle, NePdeSe is 95.94(7) Å. The PdeCl2 bond distance
[2.2898(8) Å], trans to nitrogen is slightly longer than the PdeCl1
bond distance [2.2674(8) Å], trans to selenium. PdeN [2.065(2) Å]
and PdeCl [2.2674(8) Å, 2.2898(8) Å] bond lengths are comparable
to the corresponding distances in the similar structures [37e44].
analysis. The methylene protons appeared as doublets at
d 3.94
and 4.20 ppm having coupling constant 12.0 Hz in the 1H NMR
spectrum of 12 showing their diastereotopic nature. A similar
splitting pattern was observed in the 1H NMR spectrum of 13 (at
d
3.06 and 4.58 with coupling constant 12.0 Hz). The 77Se NMR
chemical shift of 12 appeared downfield by 54 ppm with respect
to the free ligand 10 (
421 ppm). However, the 77Se NMR signal of
13 was upfield shifted by 78 ppm with respect to the free ligand 11
321 ppm) [35].
d
Table 1
(d
77Se NMR of ligands and complexes.
Compound
77Se NMR (
d)
5
6
7
8
9
12
13
287a
280a
320a
325b
350b
367b
399b
.
Na[Pd(Cl)L][PdCl4]
[PdCl(L)]Cl H2O
2b
2a
L =
N
Ph Se
Se Ph
a
In CD3OD.
In CDCl3.
b
Chart 2. SeNSe pincer ligands.

T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2559e2564
2561
O
O
N
(i)
N
Cl
Pd
Se
Se
Cl
Ph
Ph
12
10
NMe2
(i)
NMe2
Cl
Se
Pd
Se
Cl
Ph
11
Ph
13
Scheme 2. (i) Pd(CH3CN)2Cl2, CH2Cl2.
Fig. 2. Molecular structure of complex 13; thermal ellipsoids are drawn at the 70%
probability level; hydrogen atoms are removed for clarity. Significant bond lengths (Å)
and bond angles (ꢀ): PdeSe 2.3166(6), PdeN 2.065(2), PdeCl1 2.2674(8), PdeCl2
2.2898(8), SeeC1 1.879(3), SeeC10 1.949(3) Å; NePdeCl1 93.19(7), NePdeCl2
176.53(7), Cl1ePdeCl2 89.93(3), NePdeSe 95.94(7), Cl1ePdeSe 169.79(2), Cl2ePdeSe
81.07(2), C1eSeeC10 99.28(13), C1eSeePd 109.07(9), C10eSeePd 101.25(9)ꢀ.
PdeSe bond length [2.3166(6) Å] is shorter than that in the similar
reported structures [38,41e43]. The selenium atom is in a near
pyramidal coordination with the bond angles around it being
99.28(13)ꢀ, 101.25(9)ꢀ and 109.07(9)ꢀ.
2.4. Arylation of olefins: Heck coupling
The results are summarized in Table 4. Since the above reaction
conditions were optimized under ligand free conditions, these were
compared with other reaction conditions including using different
sources of palladium in presence of the ligands 6, 7, 9e11 which gave
best results under above conditions. The results are presented in the
following table (Table 5). Thus, on comparing Table 4 and Table 5, it
was seen that the combination of NMP as the solvent, NaOAc as the
base and PdCl2 as the source of palladium gives the best result. Also,
ligands are necessary for the higheractivityof the catalystsince lesser
yields were obtained under ligand-free conditions. The ligands con-
taining benzyl groups i.e.10 (93%),11 (95%) and 7 (89%) gave the best
yields (Table 4: entry 6, 7 and 3). The bulkier ligands 6 and 9 where
two selenium atoms are separated by two carbons afforded better
yields compared to ligands 5 and 8 where two seleniums are sepa-
rated by a methylene group. All of them were, however, inferior
compared to the ligands 10 and 11. It was also observed that the Se,N
ligands, 8e11 were more efficient compared to the Se,O ligands, 5e7.
Among the Se,N ligands, Se,N(amine) ligand,11 was found to be more
activecomparedtoSe,N(imine)ligands, 8, 9 and 10. Althoughentry18
and 22 in Table 5 shows same yield with PdCl2 and PdCl2(MeCN)2,
solvents and bases used were different making the comparison
between PdCl2 and PdCl2(MeCN)2 in the two entries irrelevant. In the
present study, under the optimized conditions, 11 þ PdCl2 was found
to constitute as the best catalytic system.
2.4.1. Optimization of reaction conditions
To start with, the reaction conditions for the Heck coupling were
optimized. In a typical Heck reaction of p-bromoacetophenone with
butylacrylate in presence of K2CO3 as base catalyzed by PdCl2 at
120 ꢀC for 12 h (Eq. (1)), solvents N-methylpyrrolidone (NMP) and
N,N-dimethylacetamide (DMA) were found to be of similar activity
and more active than the other solvents like N,N-dimethylforma-
mide (DMF), dioxane and toluene under ligand free condition
(Table 2). The next step was to optimize the conditions to select the
best base from the commonly used ones, which was done using
NMP as the solvent and using the conditions as shown in Eq. (1).
The results are summarized in the Table 3. Among the bases tested
under ligand free conditions NaOAc was found to be the most
suitable.
2.4.2. Performance of the ligands 5e11 in the Heck reaction
Next, we set out to evaluate the efficiency of the selenoether
ligands 5e11. The reactions were performed under aerobic condition.
2.4.3. Evaluation of 11 þ PdCl2 in the Heck reactions of different
aryl bromides and chlorides with olefins
The results of coupling reactions using the catalytic system
11 þ PdCl2 (1 mol%), in the Heck coupling of 4-substituted and
Table 2
Optimization of solvents for the above reaction.a
Entry
Solvent
Yield (%)b
1
2
3
4
5
NMP
DMA
DMF
Dioxane
Toluene
61
59
56
39
Fig. 1. Molecular structure of ligand 9; thermal ellipsoids are drawn at the 70%
probability level; hydrogen atoms are removed for clarity. Selected bond lengths (Å)
and bond angles and torsion angles(ꢀ): SeeC1 1.9141(18), SeeC 1.9652(17), Se/N
2.830 Å; C1eSeeC 99.69(7), SeeCeCi 106.34(15), CeSe/N 174.69ꢀ; C1eSeeCeCi
172.51(17), CeSeeC1eC6 175.03(14)ꢀ.
Trace
a
Reaction condition: p-bromoacetophenone (1 mmol), butylacrylate (1.5 mmol),
K2CO3 (2 mmol), PdCl2 (1 mol %), solvent (5 mL), 120 ꢀC, 12 h.
b
GC yield with respect to the aryl bromide.

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T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2559e2564
Table 3
Table 5
Optimization of base.a
Experimental conditions and yields of the coupling reactions.
Entry
Base
Yield (%)b
Entry
Ligand
Solvent
Base
Pd source
Yield (%)a
1
2
3
4
5
6
K2CO3
Na2CO3
NaOAc
Et3N
Cs2CO3
K3PO4
61
58
65
45
50
47
1
2
3
4
5
6
7
8
6
6
6
6
7
7
7
7
9
DMA
DMA
DMF
DMF
DMA
DMA
DMF
DMF
DMA
DMA
DMF
DMF
DMA
DMA
DMF
DMF
DMA
DMA
DMF
DMF
NMP
NMP
NMP
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
Na2CO3
K2CO3
NaOAc
NaOAc
NaOAc
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
Pd(OAc)2
Pd(CH3CN)2Cl2
Pd(COD)Cl2
73
75
70
72
76
81
68
77
75
81
70
76
79
87
83
85
79
88
81
77
72
88
57
a
Reaction conditions: NMP (5 mL), bases (2 mmol) other conditions same as in
Table 2.
9
b
GC yield with respect to the aryl bromide.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
9
9
9
unsubstituted aryl bromides and chlorides with olefins, n-butyla-
crylateandstyrene are showninTable6. Activatedarylbromidewith
electron withdrawing substituent gave good yield of the Heck
product (entry 1 and 4). However, turnover numbers (TON) and
turnover frequencies (TOF) were low because of comparatively
higher catalyst concentration and longer reaction times. Non-
activated, electron neutral aryl bromide, i.e., bromobenzene and
deactivated aryl bromide with electron donating substituent affor-
ded yields in the range of 70e81% of the products (entry 2, 3, 5 and
6). Aryl chlorides were unreactive under the reaction conditions
(entry 7, 8 and 9). Use of tetra-n-butylammonium bromide (TBAB)
afforded moderate yield of the product for the activated aryl chlo-
rides (entry 7 and 8). Reducing the catalyst loading to 0.1 mol% did
not affect the yield of the reactions involving aryl bromide with
n-butylacrylate significantly, although a longer reaction period of
20 h was required increasing the TONs (entry 1, 2 and 3). Rate of
increase of TOFs was comparatively low because of longer reaction
times.
10
10
10
10
11
11
11
11
11
11
11
a
GC yield with respect to aryl bromide. Reaction conditions same as in Table 4.
system showed moderate activity for the coupling of activated aryl
chlorides in presence of TBAB. Isolated complexes 12 and 13 have
shown marginally better activity in comparison to the in situ
catalysts 10 þ PdCl2 and 11 þ PdCl2, respectively in the coupling of
4-bromoacetophenone with n-butylacrylate.
Additional investigations were carried out for the Heck coupling
of 4-bromoacetophenone with n-butylacrylate in presence of
palladium complexes 12 and 13 (entry 11). The isolated palladium
complexes 12 (95%) and 13 (98%) afforded better yields of coupled
products compared to the in situ generated catalysts from the
ligands 10 (93%) and 11 (95%) [entry 11 of Table 6 vs entry 6 and 7 of
Table 4]. Presumably, the in situ catalyst did not form complex
quantitatively and some unreacted PdCl2 was left resulting in
a lower yield.
4. Experimental
All the reactions were carried out under nitrogen or argon using
standard vacuum-line techniques unless mentioned otherwise.
Solvents were purified and dried by standard procedures and were
distilled prior to use. Ligands 3 [34] and 4 [35] were prepared by the
reported procedures. Melting points were recorded on a Veego
VMP-I melting point apparatus in capillary tubes and were uncor-
rected. Nuclear magnetic resonance spectra, 1H (400 MHz) and 13
C
(100.57 MHz) were recorded on a Varian Mercury plus 400 MHz
spectrometer and a 77Se (57.22 MHz) on a Varian VXR 300S spec-
trometer. Chemical shifts are cited with respect to Me4Si as internal
standard (1H, 13C) and Me2Se as external standard (77Se). Elemental
analyses were performed on a Carlo Erba elemental analyser model
1106. Gas chromatographic analyses were carried out on a Shi-
madzu 15A gas chromatograph. Temperature was programmed to
run the analysis for 30 min reaching a maximum of 230 ꢀC starting
from 50 ꢀC. Primary gas (nitrogen) flow rate was 40 mL/min. Yields
were measured with respect to the conversion of the aryl halides.
3. Conclusion
Ligands 5e11 constitute an effective phosphine-free catalytic
system in the presence of PdCl2 for the Heck coupling of various
aryl bromides under aerobic conditions. Among them, the Se,N
bidentate ligands 8e11 were found to be more efficient ligands in
comparison to the Se,O ligands 5e7. Ligands containing benzyl
group, 10, 11 and 7 were better in comparison to the rest of the
ligands. Bulkier ligands 6 and 9 were better in comparison to their
lighter counterparts 5 and 8 respectively. Bidentate Se,N ligand 11
afforded the highest yield of the coupled product. The catalytic
4.1. Synthesis of ligands
Table 4
4.1.1. General method for synthesis of ligands
Performance of the ligands in the Heck reaction.a
To a solution of the diselenide (2 mmol) in 50 mL of dry ethanol
was added NaBH4 in excess at 0 ꢀC. After stirring for 30 min the pale
yellow color of the diselenide disappeared. To the colorless solution
of the resulting selenolate was added dibromomethane/benzyl
chloride (5 mL, excess) at 0 ꢀC and stirred for 2 h. The reaction
mixture was warmed to room temperature. It was then poured into
brine (50 mL) and extracted with 75 mL (3 ꢁ 25) of dichloro-
methane. The organic extract was dried over anhydrous Na2SO4,
concentrated under vacuum. The crude solid obtained was recrys-
tallized from CHCl3/hexane (1:1) mixture to give white solid of the
product.
Entry
Ligand
Ligand:Pd
Yield (%)b
1
2
3
4
5
6
7
5
6
7
8
9
2:1
2:1
1:1
2:1
2:1
1:1
1:1
70
85
89
79
87
93
95
10
11
a
GC yield with respect to the aryl bromide.
p-bromoacetophenone (1 mmol), butylacrylate (1.5 mmol), NaOAc (2 mmol),
b
PdCl2 (1 mol%), NMP (5 mL), 120 ꢀC, 12 h.

T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2559e2564
2563
Table 6
Yields of the coupled products using 11 þ PdCl2.
Entry
Aryl halide
Olefin
Yield (%)a
TON
TOF
1
2
3
4
4-Bromoacetophenone
Bromobenzene
4-Methoxybromobenzene
4-Bromoacetophenone
Bromobenzene
n-Butylacrylate
n-Butylacrylate
n-Butylacrylate
Styrene
95/91b
83/76b
72/66b
97
95/910b
83/760b
72/660b
97
7.92/45.50b
6.92/38.00b
3.60/33.00b
8.08
5
Styrene
88
88
7.33
6
7
8
9
10
11
4-Methoxybromobenzene
4-Chloroacetophenone
4-Chloroacetophenone
Chlorobenzene
4-Methoxychlorobenzene
4-Bromoacetophenone
Styrene
n-Butylacrylate
Styrene
n-Butylacrylate
n-Butylacrylate
n-Butylacrylate
76
76
6.33
Trace/45c
Trace/52c
Trace
Trace
95d/98e
0/45c
0/52c
0
0/3.75
0/4.33
0
0
0
95d/98e
7.92d/8.17e
a
Isolated yield.
b
c
In presence of 0.1 mol% of Pd and 20 h of reaction time.
In presence of 20 mol% TBAB at 140 ꢀC.
In presence of 12.
d
e
In presence of 13.
4.1.1.1. Synthesis of 5. Yield: 706 mg (91%), mp 182e184 ꢀC. Anal.
4.1.1.4. Synthesis of 8. Yield: 832 mg (80%), mp 210e212 ꢀC. Anal.
Calcd for C15H16O2Se2: C, 46.65; H, 4.18. Found: C, 46.93; H, 3.86. 1H
Calcd for C23H26N2O2Se2: C, 53.08; H, 5.04; N, 5.38 Found: C, 52.70;
NMR(CDCl3):
d
2.34 (b, eOH, 2H), 4.21 (s, SeCH2Se, 2H), 4.69 (s,
H, 4.76; N, 5.51. 1H NMR(CDCl3):
d 1.39 (s, 12H), 4.00 (s, SeCH2, 2H),
CH2OH, 4H), 7.21e7.42 (m, 2H), 7.56 (d, J ¼ 1.2 Hz,1H), 7.58 (d, 0.8 Hz).
4.07 (s, CH2O, 4H), 7.19e7.23 (dt, J ¼ 8 Hz, 1.2 Hz, 1H), 7.36e7.40 (dt,
J ¼ 7.6 Hz,1.2 Hz,1H), 7.58 (d, J ¼ 7.6 Hz,1H), 7.79e7.81 (dd, J ¼ 8 Hz,
1.2 Hz,1H). 13C NMR (CDCl3): 17.4 (CMe2), 28.8 (SeCH2), 68.7 (CMe2),
78.9 (CH2O), 124.9, 126.9, 127.9, 129.9, 131.2, 137.3, (aromatic C),
13C NMR (CD3OD): 20.9 (SeCH2Se), 65.3(CH2OH), 128.8, 129.1, 129.3,
132.3, 134.4, 143.9 (aromatic C). 77Se NMR (CD3OD):
d 287.
4.1.1.2. Synthesis of 6. Yield: 627 mg (78%), mp 196e198 ꢀC. Anal.
161.39 (C]N). 77Se NMR (CDCl3):
d 325.
Calcd for C16H18O2Se2: C, 48.01; H, 4.53; Found: C, 48.08; H, 4.08. 1H
4.1.1.5. Synthesis of 9. Yield: 641 mg (61%), mp 218e220 ꢀC. Anal.
NMR (CD3OD):
d 3.08 (s, SeCH2, 2H), 4.68 (s, CH2OH, 2H), 4.69 (s,
Calcd for C24H28N2O2Se2: C, 53.94; H, 5.28; N, 5.24 Found: C, 53.68; H,
CH2OH, 4H), 7.13e7.17 (dt, J ¼ 7.2 Hz, 1.6 Hz, 1H), 7.26e7.30 (dt,
J ¼ 7.6 Hz, 1.2 Hz, 1H), 7.36e7.38 (dd, 8.0 Hz, 1.2 Hz), 7.44e7.47 (dd,
7.6 Hz, 1.2 Hz). 13C NMR (CD3OD): 27.9 (SeCH2), 65.2 (CH2OH), 128.7,
5.47;N,5.61.1HNMR(CDCl3):
d1.43(s,12H), 3.19(s, SeCH2, 4H),4.08(s,
CH2O, 4H), 7.21 (t, J ¼ 7.2 Hz, 1H), 7.32 (t, J ¼ 7.2 Hz, 1H), 7.38 (t,
J ¼ 8.0 Hz, 1H), 7.79 (d, J ¼ 8.0 Hz, 1H). 13C NMR (CDCl3): 24.8 (CMe2),
28.8 (SeCH2), 68.8 (CMe2), 78.9 (CH2O),125.2,128.1,128.4,130.4,131.1,
129.1,129.2,130.2,134.5,144.4(aromaticC). 77SeNMR(CD3OD):
d280.
134.4, (aromatic C), 161.6 (C]N). 77Se NMR (CDCl3):
d 350.
4.1.1.3. Synthesis of 7. Yield: 1.05 g (95%), mp 160e162 ꢀC. Anal.
Calcd for C14H14OSe: C, 60.66; H, 5.09; Found: C, 60.40; H, 4.51. 1H
4.2. Synthesis of complexes
NMR(CDCl3):
d
1.91 (t, J ¼ 6.4 Hz, eOH, 1H), 4.05 (s, SeCH2, 2H), 4.57
(d, J ¼ 6.4 Hz, CH2OH, 2H), 7.10e7.12 (m, 2H), 7.14e7.31 (m, 5H),
7.35e7.38 (dd, J ¼ 7.6 Hz, 1.6 Hz, 1H), 7.54e7.56 (dd, J ¼ 7.6 Hz,
1.2 Hz, 1H). 13C NMR (CDCl3): 32.7 (SeCH2), 65.4 (CH2OH), 127.1,
128.3,128.5,128.6,128.8,129.8,135.4,138.6,143.3 (aromatic C). 77Se
4.2.1. General method for synthesis of complexes
To a solution of 2-(4,4-dimethyl-2-oxazolinyl) phenyl benzyl-
selenide/N,N-dimethylaminobenzylselenide [35] (1 mmol) in
20 mL of dry dichloromethane was added Pd(CH3CN)2Cl2 (259 mg,
1 mmol) and stirred at room temperature for 2 h. The solution was
filtered through a celite pad and concentrated to ca. 2 mL. It was
then layered with 1 mL of hexane and kept at 0 ꢀC overnight when
orange crystals of the title compound were obtained.
NMR (CDCl3):
d 320.
Table 7
Crystal data and structure refinement for 9 and 13.
9
13
4.2.1.1. Synthesis of 12. Yield: 500 mg (96%), mp 225e227 ꢀC. Anal.
Calcd for C18H19Cl2NOPdSe: C, 41.45; H, 3.67; N, 2.69. Found: C,
Empirical formula
Fw
Crystal system
Space group
a [Å]
C24H28N2O2Se2
534.40
Monoclinic
C2/c
26.8382(16)
9.0050(4)
9.8683
90
105.385
90
2299.5(2)
4
C16H19Cl2NPdSe
81.58
Orthorhombic
Pna21
12.070(3)
23.358(5)
5.7323(12)
90
90
90
1616.1(6)
4
1.979
41.87; H, 3.49; N, 3.03. 1H NMR(CDCl3):
d 1.83 (s, NMe2, 6H), 1.92(s,
NMe2, 6H), 3.94 (d, J ¼ 12.0 Hz, SeCH2, 1H), 4.20 (d, J ¼ 12.0 Hz,
SeCH2, 1H), 4.41e4.47 (m, CH2O, 2H), 6.95 (d, J ¼ 10.8 Hz, 2H),
7.18e7.27 (m, 3H), 7.36 (d, J ¼ 8.0 Hz, 1H), 7.44e7.49 (m, 1H),
b [Å]
c [Å]
7.61e7.65 (m, 1H), 7.88e7.89 (m, 1H). 77Se NMR (CDCl3):
d 367.
a
b
g
[ꢀ]
[ꢀ]
[ꢀ]
4.2.1.2. Synthesis of 13. Yield: 430 mg (90%), mp 201e203 ꢀC. Anal.
Calcd for C16H19Cl2NPdSe: C, 39.90; H, 3.98; N, 2.91. Found: C, 40.13;
V [Å3]
H, 3.55; N, 3.20. 1H NMR(CDCl3):
d 2.46e2.82 (2 broad bands, NMe2,
Z
Dcalcd. [mgmꢂ3
Temp [K]
]
1.544
12H), 3.06 (d, J ¼ 12.0 Hz, CH2NMe2, 2H), 4.58 (d, J ¼ 12.0 Hz, SeCH2,
2H), 7.20e7.22 (m, 1H), 7.30e7.36 (m, 5H), 7.44e7.51 (m, 2H), 7.58
273(2)
4.72e32.74
3.239
0.0294
0.0434
3800/0/138
0.958
123(2)
3.11e28.29
3.723
0.0210
0.0258
q
range [ꢀ]
(d, J ¼ 8.0 Hz, 1H). 77Se NMR (CDCl3):
d
399.
Abs. coeff. [mmꢂ1
Final R(F) [I > 2
(I)]a
wR(F2) indices [I > 2
]
s
4.3. General method for optimization of the catalytic reaction
condition using gas chromatography
s(I)]
Data/restraints/parameters
3752/1/192
1.007
Goodness of fit on F2
P
P
P
a
2
jjFoj e jFcjj/ jFoj and wR(Fo2) ¼ { [w(Fo e Fc2)]2/
A two-necked round-bottomed flask was charged with aryl
bromide (1 mmol), olefin (1.5 mmol), base (2 mmol), solvent (5 mL)
Definitions: R(Fo) ¼
P
[w(Fc2)2]}1/2
.

2564
T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2559e2564
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a specified time at the specified temperature. Then the reaction
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¼ 0.71073 Ǻ). The data were
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We are thankful to the Department of Science and Technology
(DST), India for funding this work. Additional help from the
Sophisticated Analytical Instrument Facility (SAIF), Indian Institute
of Technology, Bombay, for 300 MHz NMR spectroscopy is grate-
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and Industrial Research, India for providing fellowship.
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CCDC 792015 and 792016 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
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