Straightforward synthesis of substituted dibenzyl derivatives

Article abstract of DOI:10.1016/j.tet.2013.04.073

The C-C bond formation by homogeneous catalysis is a powerful tool in organic synthesis. The replacement of noble metal by cheaper one for already reported methodologies is of interest for an economical purpose. The attractivity of such replacement is also enhanced if a first raw transition metal is found to be active in several processes. This work demonstrates that a common nickel complex can be used for a two-step cross-coupling procedure, namely a homocoupling reaction of benzyl derivatives and a subsequent Suzuki reaction. These consecutive reactions permit the synthesis of new polyfunctionalized dibenzyl compounds.

Full text of DOI:10.1016/j.tet.2013.04.073

Tetrahedron 69 (2013) 4875e4882
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Straightforward synthesis of substituted dibenzyl derivatives
a
,
b
,
,
b
,
,
b
,
c
,
,b,c
Cleve D. Mboyi c, Sylvain Gaillard a c, Mbaye D. Mabaye a
d, Nicolas Pannetier a
,
ꢀ
Jean-Luc Renaud a
a Normandie University, France
,b,c,
*
b
ꢁ
ꢁ
Universite de Caen Basse Normandiie, Laboratoire de Chimie Moleculaire et Thioorganique, 14050 Caen, France
c CNRS, UMR 6507, 14050 Caen, France
d University of Ziguinchor, BP 523 Ziguinchor, Senegal
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 March 2013
Received in revised form 11 April 2013
Accepted 12 April 2013
Available online 19 April 2013
The CeC bond formation by homogeneous catalysis is a powerful tool in organic synthesis. The re-
placement of noble metal by cheaper one for already reported methodologies is of interest for an eco-
nomical purpose. The attractivity of such replacement is also enhanced if a first raw transition metal is
found to be active in several processes.
This work demonstrates that a common nickel complex can be used for a two-step cross-coupling
procedure, namely a homocoupling reaction of benzyl derivatives and a subsequent Suzuki reaction.
These consecutive reactions permit the synthesis of new polyfunctionalized dibenzyl compounds.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Nickel
Homogeneous catalysis
Homocoupling reaction
Suzuki reaction
Benzylic halide
1. Introduction
Concerning catalytic systems, the first example was reported in
1961 in the presence of FeCl3 as catalyst and magnesium to gen-
The CeC bond formation by homogeneous catalysis is a power-
ful tool in organic synthesis.1 Metals, such as palladium and nickel
have played a central role in the development of these cross-
coupling reactions and have shown wide applicability in the in-
dustrial synthesis of fine chemicals, pharmaceutically active com-
pounds, and agricultural chemicals, as well as in natural product
synthesis. Those carbonecarbon bond formations involved mainly
Csp or Csp2. Coupling reactions between two Csp3-hybridized car-
bon centers are much more rare.2 Two main reasons for this under
represented field in organic synthesis are the usually slow oxidative
addition of alkyl halides to the organometallics species and the fast
erate in situ a Grignard reagent from a benzylic halide derivative.11
Later on, several transition metal, such as nickel,12 palladium
complexes,13 manganese,14 titanium complex,15 iron,16 and cobalt
salts17 were used as catalyst to produce dibenzyl compounds via
a homocoupling reaction. However, all these methods suffered
from some drawbacks: (i) the use of expensive noble metal,13b (ii)
the use of stoichiometric amount of Grignard or organozinc re-
agent,12,14,16 (iii) the use of inorganic salt as additive,12a (iv) the use
of organic compounds as oxidant,13b and (v) harsh reaction condi-
tions in some case.12c
Based on the previous procedures, and on the proposed mech-
anism, we postulated that if a transition metal is able to catalyze
homocoupling reaction, the benzyl derivatives may serve both as
a nucleophile (half equivalent generated in situ in the presence of
Zn, Mn or Mg) and as an electrophile (the other half equivalent).
Our working hypothesis is highlighted in Scheme 1.
Now, considering the new economic and environmental race,
the use of first raw transition metal (very abundant on earth and
consequently among the most inexpensive, usually easy to handle
and environmentally friendly metal derivatives), we focussed our
attention to nickel complexes. Furthermore, based on our working
hypothesis, if a nickel(0) is the catalytic active species in the
homocoupling reaction of benzyl halide derivatives 1, this species
might also act in a further cross-coupling reaction18 creating either
competitive b-hydride elimination of the formed alkyleMeX in-
termediate.3 Dibenzyl compounds are usually obtained by homo-
coupling reactions between two benzylic halides and are usually
considered as side products in coupling reactions involving ben-
zylic fragment. However, these dibenzyl derivatives are key build-
ing blocks for the synthesis of dyes, polymers, agrochemicals, and
pharmaceuticals.4 These homocoupling reactions, mediated by
stoichiometric amount of metal, such as vanadium,5 manganese,6
cobalt,7 nickel,8 indium,9 and chrome10 were already reported.
* Corresponding author. E-mail address: jean-luc.renaud@ensicaen.fr (J.-L.
Renaud).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.04.073

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C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
2a in 86% isolated yield (Table 1, entries 1, 2, and 3). Concerning the
solvent, the reaction in toluene required heating at 80 ꢀC to reach
complete conversion whereas the coupling can be performed at
room temperature in THF or dioxane whatever the catalyst used
(Table 1, entries 1, 4, 5, 6, 7, and 8). Finally, the catalytic activity of
[NiCl2(PPh3)2] and [NiCl(napth)(PPh3)2] were found quite similar,
except a slight difference in THF (Table 1, entry 1 vs. 6). Compared
with previous reports,12 our reaction conditions were milder in the
presence of either commercially available or easily prepared nickel
complexes and half equivalent of reducing agent. Interestingly,
simple iron salts, such as FeCl3 and FeCl2, revealed a good catalytic
activity although lower than nickel complexes. With these salts, 2a
was observed in 70% and 82% conversion, respectively, in the
presence of 0.55 equiv of magnesium in dry THF after 15 min at
room temperature. Nevertheless, as our main goal was to find
a common catalyst for both homocoupling of halogenobenzylic
halide and Suzuki coupling, this work was pursued with nickel
complexes. For this purpose, the scope and limitation study was
carried out in the presence of [NiCl2(PPh3)2], the simplest nickel
catalyst, and zinc in degassed THF.21 Nevertheless, when conver-
sions and yields of the homocoupling reactions appeared not sat-
isfactory in the presence of zinc, manganese powder, and
magnesium dust were evaluated.
Scheme 1. Postulated mechanism for the benzyl halides homocoupling reaction.
additional CeC bonds,19 via for example a Suzuki reaction, or CeN
bonds.20
This may afford original polyfunctionalized dibenzyl derivatives
via a sequential synthesis from simple benzyl derivatives as showed
in Scheme 2.
Results of the scope and limitation study were collected in
Table 2. Zinc dust was found to be the most efficient metal yielding
dibenzyl derivatives 2 in moderate to high yields (Table 2, entries
1e4, 13, 15e16, 19, and 24). Magnesium dust was also efficient and
can be used as alternative to zinc dust, though with slightly lower
isolated yields (Table 2, entries 6, 9, 18, and 21). Noteworthy, in the
case of benzyl chloride derivatives 1e and 1f, manganese provided
better yields of 2d (Table 2, entries 7 vs. 8 and 10 vs. 11). Until now,
we have no clear evidence to explain the difference of reactivity
between the three metals but it might be due to their different
redox potentials. Of note, steric hindrance has almost no influence
on the reactivity (entries 1e3 and 8, 11, Table 1), however meta
substituted benzylic bromide compound 1b afforded lower yields
than the two other substituted aromatic position (Table 1, entries 1
vs. 2 vs. 3). All aromatic halide derivatives were generally well
tolerated in these reaction conditions and no reduction of these
functions was observed. Nevertheless, the reactivity of 2-
iodobenzylchloride 1h can be highlighted. Indeed, when chloride
atom is present at the benzylic position (Table 1, entry 14), the
expected compound 2g was not obtained. However, with bromide
derivative 1i, 2g was obtained in 41% isolated yield (Table 1, entry
15). For other benzyl bromides 1je1m bearing bulky alkyl frame-
works or ether group, the best results were obtained with both zinc
and magnesium dust as metal source (Table 1, entries 16e24). In
these reaction conditions, with electron-withdrawing group, such
as ester, the catalytic activity was maintained and yielded the
dibenzyl derivatives 2l, 2m, and 2n in 76, 78, and 64%, respectively.
Moreover, no reduced product was observed when 1n and 1p were
engaged (Table 2, entries 25e27).
Scheme 2. Retrosynthetic approach to polyfunctionalized dibenzyl derivatives.
In this work, we report on an improvement of the nickel-
catalyzed homocoupling reaction of benzylic halides derivatives 1
and the synthesis of polyfunctionalized dibenzyl derivatives 4 via
a Suzuki coupling reaction.
2. Results and discussion
4-Bromobenzyl bromide 1a was chosen as a model reagent,
to define the optimized reaction conditions (catalyst, solvent,
temperature). Based on previous works, the selected solvents
for the screening were toluene, dioxane, and THF. As catalysts,
[NiCl2(PPh3)2] and [NiCl(napht)(PPh3)2] were evaluated in the
presence of zinc, magnesium or manganese as reductive metal.
Results for the homocoupling reaction were summarized in Table 1.
We were pleased to find that 0.55 equiv of metal (zinc or magne-
sium) provided the expecting homocoupling product 2a from
benzyl bromide derivative 1a (Table 1, entries 1 and 2). Among all
evaluated metal, zinc appeared to be the most efficient leading to
Table 1
Optimization of the reaction conditions for the formation of 2a
Keeping in mind that nickel complexes could catalyze both
homocoupling reaction of 1 and Suzuki cross coupling with 2,18 we
took advantage of the presence of another halide on the aromatic
ring to begin the second step of this study, namely a Suzuki reaction
in the presence of the same nickel complexes. As previously men-
tioned, THF, toluene, and dioxane were investigated in the reaction
between compound 2a and phenylboronic acid 3a (Scheme 3).
However, but not surprisingly, no reaction was observed with
the simple [NiCl2(PPh3)2] complex. Gratifyingly, full conversion of
2a into compound 4a was obtained in the presence of 5 mol % of
[NiCl(napht)(PPh3)2],10 mol % of triphenylphosphine and 8 equiv of
K2CO3 in toluene at 100 ꢀC overnight. In these reaction conditions,
4a was isolated in 81% yield. Then, a rapid study of the scope of this
reaction with compounds 2a, 2b, and 2c was undertaken.
Entry
[Ni] cat.
Solvent
Metal
T (ꢀC)
Conv. (%)b
1
2
3
4
5
6
7
8
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
NiCl2(PPh3)2
THF
THF
THF
Toluene
Dioxane
THF
Toluene
Dioxane
Zn
Mg
Mn
Zn
Zn
Zn
Zn
Zn
rt
rt
rt
80
rt
rt
80
rt
100 (86)c
85 (50)c
15
100
100
95
100
100
NiCl2(PPh3)2
NiCl(napth)(PPh3)2
NiCl(napth)(PPh3)2
NiCl(napth)(PPh3)2
a
Reaction conditions: 4-bromobenzyl bromide 1a (1 mmol), metal (0.55 mmol),
nickel complex (0.05 mmol) solvent (c¼0.66 M) at temperature indicated in the
table for 18 h.
b
Conversion into 2a determined by 1H NMR spectroscopy.
Isolated yield.
c

C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
Table 2 (continued )
4877
Table 2
Nickel complexes-catalyzed homocoupling reaction of 1a
Entry
Substrate
Metal Yield Entry
(%)b
Substrate
Metal Yield
(%)b
13
Zn
Zn
2f, 90 27
Zn
2n, 64
1p
Entry
Substrate
Metal Yield Entry
(%)b
Substrate
Metal Yield
(%)b
1g
1h
14
0, 2g
1
Zn
2a, 86 15
Zn
2g, 41
a
Reaction conditions: halogenobenzyl halide 1 (1 mmol), metal (0.55 mmol),
[NiCl2(PPh3)2] (0.05 mmol) THF (c¼0.66 M) at room temperature for 18 h.
1i
1a
b
Isolated yield.
2
3
Zn
Zn
2b, 59 16
2c, 79 17
Zn
2h, 85
2h, 15
1b
1c
1j
1j
Mn
Scheme 3. Suzuki cross-coupling.
4
5
6
7
8
9
Zn
2d, 90 18
2d, 0 19
2d, 88 20
2d, 10 21
2d, 93 22
2d, 80 23
Mg
Zn
2h, 73
2i, 95
2i, 30
2i, 92
2j, 89
2j, 90
1j
1d
1d
1d
1e
1e
Results on the Suzuki cross coupling reaction were presented in
Table 3. The more sophisticated dibenzyl products 4 were obtained
in moderate to good yields (Table 3). The scope of the Suzuki
coupling was successfully expanded to ortho, meta, and para
bromo-substituted dibenzyl compounds 2aec with phenylboronic
acid 3a (Table 3, entries 1, 2, and 3). Unfortunately, alkyl and bulky
aromatic boronic acid failed to react with compound 2a in these
conditions (Table 3, entries 6 and 7). However, naphthyl and larger
aromatic framework, such as anthracenyl group yielded the cor-
responding functionalized derivatives 4e and 4h (Table 3, entries 6
and 8). Noteworthy, electron-withdrawing groups, such as ester
substituent, were well tolerated in these reaction conditions and
here again no reduced product was observed (Table 3, entries
9e12). Nevertheless, a higher catalyst loading (10 mol %) was
necessary to achieve full conversion and the desired products 4ie4l
(Table 3, entries 9e12) were obtained in good yields ranging from
64 to 75%. Interestingly, the 1H NMR spectroscopy show that
compounds 4l was obtained as a 1:1 mixture of atropoisomers.
Having demonstrated that a nickel complex, such as [NiCl(napht)
(PPh3)2] could catalyzed two different cross-coupling reactions
(Tables 1 and 3), we next tried these two reactions in a sequential
one pot reaction, as depicted in Scheme 4. However, whatever the
conditions applied, only intermediate 2a was recovered at the end of
these sequences. Addition of various reducing agents, such as zinc or
butyl lithium, did not lead to any improvement.
Mn
Mg
Zn
1k
1k
1k
1l
Mn
Mg
Zn
Mn
Mg
Mg
These results seem to indicate that two different catalytic active
nickel species were present in these reactions. Our first hypothesis
for the homocoupling reaction of 1 was based on the plausible
mechanism depicted in Scheme 5 and on the usually proposed
Ni(0)/Ni(II) intermediates. Insertion of the zinc metal into the
benzylic CeX bond might lead to the corresponding organozinc
reagent. A ligand exchange followed by a reductive elimination
might generate the nickel(0) and liberate the benzylnaphthalene.
Alternatively, the nickel(0) synthesis might be also explained by
a direct reduction of the nickel(II) by zinc metal. Then, the nickel(0)
species might enter in the catalytic cycle and react with benzyl
halide 1 via an oxidative addition furnishing an equilibrium be-
1e
1l
10
11
Zn
2e, 65 24
2e, 89 25
Zn
Zn
2k, 76
2l, 76
1m
1n
1f
1f
Mn
tween an
h h
1-benzyl (I) and an 3-benzyl (II) ligated nickel(II)
12
Mg
2e, 60 26
Zn
2m, 78
complex as recently reported by Louie.22 Substitution of the chlo-
ride on the metal center by the organozinc reagent might lead to
1f
1o

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C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
Table 3 (continued)
Table 3
Nickel complexes-catalyzed Suzuki coupling reaction of 2 with boronic acids 3a
Entry
Substrate
Boronic acid
Yieldb (%)
12
4l, 74c
Entry
1
Substrate
Boronic acid
Yieldb (%)
2n
3c
a
Reaction conditions: 1,2-bis-(bromophenyl)ethane 2 (1 mmol), boronic acid 3
(3 mmol), K2CO3 (8 mmol), [NiCl(napth)(PPh3)2] (5 mol %), triphenylphosphine
(10 mol %), toluene (c¼0.1 M) at 100 ꢀC for 18 h.
4a, 81
b
2a
2b
2c
3a
3a
3a
Isolated yield.
c
[NiCl(napth)(PPh3)2] (10 mol %) and triphenylphosphine (20 mol %) at 100 ꢀC for
24 h.
2
3
4
4b, 97
4c, 71
4d, 56
Scheme 4. One-pot synthesis attempts of 4a from 1a.
2a
2a
3b
3c
5
6
4e, 85
4f, 0
2a
3d
3e
7
8
4g, 0
2a
2b
4h, 86
Scheme 5. Proposed mechanism for the homocoupling reaction of benzyl halides 1
catalyzed by [NiCl(1-naphthyl)(PPh3)2].
3f
the dibenzyl nickel(II) complex (III). Finally, a reductive elimination
might regenerate the active nickel(0) species and afford the ex-
pected product 2.
9
4i, 75c
4j, 64c
4k, 70c
Nevertheless, another mechanism cannot be excluded as the
detection of benzaldehyde21 indicates that radical species are in-
volved in this mechanism. Thus, radical mechanism, which was
already proposed in several Ni-catalyzed cross-coupling re-
actions,23 cannot be ruled out. The mechanism involved in this case
either Ni(I)/Ni(III) or Ni(II)/Ni(III) species, as plausible organonickel
intermediates.23b Oxidative addition of the aryl halide on Ni(I)
could occur to afford a Ni(III) species bearing one benzyl ligand and
two halide ligands. Transmetalation with the benzylmetal nucleo-
phile and reductive elimination would liberate the active Ni(I)
species and the dibenzyl derivative. Furthermore, if such nickel
intermediate species are present in the homocoupling reaction, the
usually postulated nickel(0) species, required for the Suzuki cross
coupling, might not be present (Scheme 6).
3a
2n
2n
10
11
2n
3b

C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
4879
Then, such relevant clues allow us to postulate that two
different mechanisms occurred in these two consecutive se-
quences: the homocoupling reaction may follow a radical pro-
cess whereas a classical Ni(0)/Ni(II) mechanism may be involved
in the Suzuki coupling. This explains also why the one pot se-
quence cannot be carried out successfully in the presence of
these nickel complexes.
3. Conclusion
In conclusion, we have improved and broadened the scope of the
homocoupling reaction, we have also demonstrated that only
0.55 equiv of metal (Zn, Mn or Mg) was necessary for the nickel-
catalyzed homocoupling reaction of benzyl halides 1 derivatives.
We have also shown that a common nickel complex could both
catalyzed the homocoupling reaction of benzyl halides 1 and the
cross-coupling Suzuki reaction if the resulting compound 2 bears an
aromatic halide leading to new polyfunctionalized dibenzyl de-
rivatives 4. Unfortunately, attempts to make a sequential one-pot
synthesis of 4 starting from 1 failed. Nevertheless, as ligands have
been reported to have a crucial effect on the mechanism pathway in
cross coupling reaction catalyzed by nickel complexes,25 the de-
velopment of new nickel(II) complexes for this sequential one pot
synthesis of compounds 4 is under investigations in our laboratories.
Scheme 6. Alternative mechanism for the nickel-catalyzed homocoupling reaction of
benzyl halides.
4. Experimental section
4.1. General
Similarly, for the Suzuki coupling, two mechanisms may be
proposed: (i) a classical coupling involving Ni(0)/Ni(II) organome-
tallic intermediates and (ii) a second one invoking formation of
Ni(I)/Ni(III), via again a radical type mechanism.15 In the later, ox-
idative addition of the aryl halide could occur to afford a NiIII spe-
cies bearing one aryl ligand and two halide ligands.
Transmetalation with the boronic acid and reductive elimination
could complete the cycle (Scheme 7).
All reactions were carried out under nitrogen atmosphere. Sol-
vents were distilled and degassed before use. Other reagents were
purchased from commercial sources and used without any further
purification.
4.1.1. Synthesis of [NiCl2(PPh3)2].26 In a flask, triphenylphosphine
(2 equiv, 20 mmol) in acetic acid (60 mL) was stirred and heated at
100 ꢀC until complete dissolution. NiCl2$6H2O was dissolved in
water (1 mmol/3 mL). This solution was added to the previous hot
solution. The reaction mixture was stirred at 100 ꢀC for 40 min. The
black solid was collected on a sintered-glass funnel and succes-
sively washed with water (3ꢁ5 mL), ethanol (3ꢁ5 mL), and ether
(3ꢁ5 mL). The dark-green solid (41%) was dried under vacuum.
4.1.2. Synthesis of [NiCl(1-naph)(PPh3)2].19b In a flamed Schlenk
tube under nitrogen atmosphere, a stirred mixture of NiCl2$6H2O
(7 mmol), triphenylphosphine (14 mmol) in absolute ethanol
(30 mL) was heated at 80 ꢀC until a gentle reflux started. Then, 1-
chloronaphthalene (10 mmol) was added follow by zinc dust
(7 mmol) over 5 min. The dark-green mixture turned yellow. After
stirring and heating under reflux for 1 h (under an atmosphere of
nitrogen), the mixture was cooled down to room temperatures.
Hydrochloric acid (37% aqueous solution, 2ꢁ1.3 mL) was added
over 10 min. After stirring for 1.5 h, the solid was filtered off on
a sintered-glass funnel and successively washed with ethanol
(7 mL), hydrochloric acid (2ꢁ7 mL), ethanol (2ꢁ7 mL), diethyl ether
(2ꢁ7 mL), pentane (2ꢁ7 mL). The yellow solid (40%) was dried in
vacuum a temperature below 45 ꢀC. 31P NMR (162 MHz, CDCl3),
Scheme 7. Proposed mechanism for the nickel-catalyzed Suzuki reaction.
d
21.5 (s, 1P) ppm.
4.2. General procedure for the homocoupling reaction of
halogenobenzyl halide 1
In order to determine, which mechanism operated, we un-
dertook some crude 1H NMR analysis. Thus for example with 4a, we
were pleased to observe a chemical shift at 4.51 ppm corresponding
to the CH2 fragment in benzylnaphthalene, integrating for 0.1
proton (so namely, a 5 mol % CH2 fragment).24 In the view of such
a result, a classical Ni(0)/Ni(II) mechanism may be suggested.
In a flamed Schlenk tube under nitrogen atmosphere, [NiCl(1-
naph)(PPh3)2] (0.05 mmol, 0.05 equiv) was introduced with metal
dust (0.55 mmol, 0.55 equiv) and halogenobenzyl halide derivatives 1
(1 mmol, 1 equiv) in anhydrous and degassed THF (3 mL,

4880
C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
c¼0.66 mol Lꢂ1). The reaction mixture was stirred at room tempera-
ture under nitrogen atmosphere for 18 h. Water (3 mL) was added and
aqueous layer was extracted with ethyl acetate (3ꢁ5 mL). Combined
organic layers were combined and washed with saturated aqueous
solution of NaCl (5 mL) and dried over MgSO4. After filtration, solvent
was removed under vacuum to give the crude product 2, which was
purified by flash chromatography on silica gel with pentane as eluent.
powder. 1H NMR (400 MHz, CDCl3):
d 2.94 (s, 4H), 7.17e7.23 (m,
6H), 7.27e7.32 (m, 4H) ppm.
4.2.9. 1,2-Bis-(4-tert-butylphenyl)ethane 2i.30 Starting from 1k and
using the general procedure with zinc dust as metal, pure com-
pound 2i (0.475 mmol, 95%) was obtained as a white powder.
Starting from 1k and using the general procedure with magnesium
dust as metal, pure compound 2i (0.46 mmol, 92%) was obtained as
4.2.1. 1,2-Bis-(4-bromophenyl)ethane 2a.14d Starting from 1a and
using the general procedure with zinc dust as metal, pure com-
pound 2a (0.430 mmol, 86%) was obtained as a white powder.
Starting from 1a and using general procedure with magnesium dust
as metal, pure compound 2a (0.365 mmol, 73%) was obtained as
a white powder. 1H NMR (500 MHz, CDCl3):
d 1.40 (s, 18H), 2.96 (s,
4H), 7.23e7.28 (m, 4H), 7.38e7.42 (m, 4H) ppm.
4.2.10. 1,2-Bis-(3,5-di-tert-butylphenyl)ethane 2j. Starting from 1l
and using the general procedure with zinc dust as metal, pure com-
pound 2j (0.445 mmol, 89%) was obtained as awhite powder. Starting
from 1l and using the general procedure with magnesium dust as
metal, pure compound 2j (0.45 mmol, 90%) was obtained as a white
a white powder. 1H NMR (400 MHz, CDCl3):
d 2.84 (s, 4H), 6.99 (d,
J¼6.6 Hz, 4H), 7.38 (d, J¼6.6 Hz, 4H) ppm.
4.2.2. 1,2-Bis-(3-bromophenyl)ethane 2b.27 Starting from 1b and
using the general procedure with zinc dust as metal, pure com-
pound 2b (0.245 mmol, 59%) was obtained as a white powder. 1H
powder. Mp: 89e90 ꢀC. 1H NMR (400 MHz, CDCl3):
d 1.36 (s, 36H),
2.96 (s, 4H), 7.09 (d, J¼1.8 Hz, 4H), 7.30 (t, J¼1.8 Hz, 2H) ppm.13C NMR
(125 MHz, CDCl3):
d
31.5 (qꢁ 12), 34.8 (tꢁ 2), 38.7 (sꢁ 4),119.9 (dꢁ2),
NMR (400 MHz, CDCl3):
J¼6.4 Hz, 2H), 7.34 (m, 4H) ppm.
d
2.87 (s, 4H), 7.07 (d, J¼6.4 Hz, 2H), 7.15 (t,
122.7 (dꢁ 4), 141.1 (sꢁ 2), 150.6 (sꢁ 4) ppm. IR (neat):
n 3054, 3026,
2951, 2864, 1598, 1479, 1457, 1362, 1248, 869, 806, 710 cmꢂ1. HRMS
(m/z): [M]þ calculated for C30H46, 406.3600; found, 406.3615.
4.2.3. 1,2-Bis-(2-bromophenyl)ethane 2c.13b Starting from 1c and
using the general procedure with zinc dust as metal, pure com-
pound 2c (0.395 mmol, 79%) was obtained as a white powder. 1H
4.2.11. 1,2-Bis-(3-methoxyphenyl)ethane 2k.31 Starting from 1m
and using the general procedure with zinc dust as metal, pure
compound 2k (0.38 mmol, 76%) was obtained as a colorless liquid
after purification by flash chromatography on silica gel (pentane/
NMR (400 MHz, CDCl3):
2H), 7.17e7.24 (m, 4H), 7.61 (dd, J¼1.0, 8.0 Hz, 2H) ppm.
d
3.04 (s, 4H), 7.07 (ddd, J¼2.3, 6.8, 8.0 Hz,
ether, 98:2). 1H NMR (400 MHz, CDCl3):
d 2.90 (s, 4H), 3.79 (s, 6H),
4.2.4. 1,2-Bis-(4-chlorophenyl)ethane 2d.14d Starting from 1d and
using the general procedure with zinc dust as metal, pure com-
pound 2d (0.45 mmol, 90%) was obtained as a white powder.
Starting from 1d and using the general procedure with magnesium
dust as metal, pure compound 2d (0.44 mmol, 88%) was obtained as
a white powder. Starting from 1e and using the general procedure
with manganese dust as metal, pure compound 2d (0.465 mmol,
93%) was obtained as a white powder. Starting from 1d and using
the general procedure with magnesium dust as metal, pure com-
pound 2d (0.40 mmol, 80%) was obtained as a white powder. 1H
6.73e6.77 (m, 4H), 6.80 (d, J¼7.5 Hz, 2H), 7.21 (t, J¼7.5 Hz, 2H) ppm.
4.2.12. 1,2-Bis-(m-methyl benzoate)ethane 2l. Starting from 1o and
using the general procedure with zinc dust as metal, pure com-
pound 2l (0.38 mmol, 76%) was obtained as a white powder after
purification by flash chromatography on silica gel (pentane/ether,
95:5). Mp: 78e79 ꢀC. 1H NMR (400 MHz, CDCl3):
d
2.98 (s, 4H), 3.91
(s, 6H), 7.30e7.36 (m, 4H), 7.85e7.90 (m, 4H) ppm. 13C NMR
(125 MHz, CDCl3):
37.5 (tꢁ 2), 52.1 (qꢁ 2), 127.4 (dꢁ 2), 128.4 (dꢁ
2), 129.5 (dꢁ 2), 130.2 (sꢁ 2), 133.1 (dꢁ 2), 141.5 (sꢁ 2), 167.2 (sꢁ2)
d
NMR (400 MHz, CDCl3):
J¼6.4 Hz, 4H) ppm.
d
2.89 (s, 4H), 7.09 (d, J¼6.4 Hz, 4H), 7.27 (d,
ppm. IR (neat): n 3028, 2951, 1720, 1588, 1434, 1285, 1201, 1106,
1082, 984, 753, 694 cmꢂ1. HRMS (m/z): [MþNa]þ calculated for
C18H18O4, 321.1103; found, 321.1100.
4.2.5. 1,2-Bis-(2-chlorophenyl)ethane 2e.13b Starting from 1f and
using the general procedure with zinc dust as metal, pure com-
pound 2e (0.325 mmol, 65%) was obtained as a white powder.
Starting from 1f and using the general procedure with manganese
dust as metal, pure compound 2e (0.445 mmol, 89%) was obtained
4.2.13. 1,2-Bis-(p-methyl benzoate)ethane 2m.32 Starting from 1p
and using the general procedure with zinc dust as metal, pure
compound 2m (0.39 mmol, 78%) was obtained as a white powder
after purification by flash chromatography on silica gel (pentane/
as a white powder. 1H NMR (400 MHz, CDCl3):
d
3.04 (s, 4H),
ether, 95:5). Mp: 119e120 ꢀC. 1H NMR (400 MHz, CDCl3):
d 2.98 (s,
7.14e7.19 (m, 6H), 7.39e7.34 (m, 2H) ppm.
4H), 3.89 (s, 6H), 7.18 (d, J¼8.2 Hz, 4H), 7.92 (d, J¼8.2 Hz, 4H) ppm.
4.2.6. 1,2-Bis-(4-fluororophenyl)ethane 2f.28 Starting from 1g and
using the general procedure with zinc dust as metal, pure com-
pound 2f (0.45 mmol, 90%) was obtained as a white powder. 1H
4.2.14. 1,2-Bis-(methyl 2-bromo-5-benzoate)ethane 2n. Starting
from 1q and using the general procedure with zinc dust as metal,
pure compound 2n (0.32 mmol, 64%) was obtained as a white
powder after purification by flash chromatography on silica gel
(pentane/ether, 95:5). Mp: 158e159 ꢀC. 1H NMR (400 MHz, CDCl3):
NMR (400 MHz, CDCl3):
JHeH¼8.7 Hz, 4H), 7.08 (dd, JHeF¼5.5, JHeH¼8.7 Hz, 4H) ppm.
d
2.87 (s, 4H), 7.00 (dd, JHeF¼8.7,
d
3.10 (s, 4H), 3.91 (s, 6H), 7.63 (d, J¼8.3 Hz, 2H), 7.74 (dd, J¼2.1, 8.3 Hz,
4.2.7. 1,2-Bis-(2-iodophenyl)ethane 2g.28 Starting from 1i and using
the general procedure with zinc dust as metal, pure compound 2g
(0.205mmol, 41%)wasobtainedasawhitepowder.1H NMR (400 MHz,
2H), 7.88 (d, J¼2.1 Hz, 2H) ppm.13C NMR (100 MHz, CDCl3):
36.3 (tꢁ
d
2), 52.3 (qꢁ 2), 128.9 (dꢁ 2), 129.6 (sꢁ 2), 130.0 (sꢁ 2), 131.5 (dꢁ 2),
133.1 (dꢁ 2), 140.7 (sꢁ 2), 166.5 (sꢁ 2) ppm. IR (neat):
n 3027, 2955,
CDCl3):
d
3.00 (s, 4H), 6.91 (dt, J¼1.8, 7.6 Hz, 2H), 7.22 (dd, J¼1.8, 7.6 Hz,
1715,1575,1439,1303,1262,1203; 1107,1023, 760 cmꢂ1. HRMS (m/z):
[MþNa]þ calculated for C18H16Br2O4Na, 476.9313; found, 476.9303.
2H), 7.27 (dt, J¼1.1, 7.6 Hz, 2H), 7.83 (dd, J¼1.1, 7.6 Hz, 2H) ppm.
4.2.8. 1,2-Bis-phenylethane 2h.29 Starting from 1j and using the
general procedure with zinc dust as metal, pure compound 2h
(0.425 mmol, 85%) was obtained as a white powder. Starting from
1j and using the general procedure with magnesium dust as metal,
pure compound 2h (0.365 mmol, 73%) was obtained as a white
4.3. General procedure for the Suzuki coupling
In a flamed Schlenk tube under nitrogen atmosphere, K2CO3
(2.4 mmol), [NiCl(1-naph)(PPh3)2] (5 mol %), PPh3 (10 mol %), aryl
boronic acid 3 (0.9 mmol), and 1,2-bis(n-bromophenyl)ethane 2

C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
4881
(0.3 mmol) were introduced in dryand degassed toluene (3 mL). The
reaction mixture was heated at 100 ꢀC under nitrogen atmosphere
for 18 h. After being quenched with water (3 mL), the reaction
mixture was extracted with ethyl acetate (3ꢁ5 mL). Combined or-
ganic layers were washed with brine and dried over MgSO4. After
filtration, solvent was removed under vacuum. The pure product 4
was purified by column chromatography on silica gel.
chromatography on silica gel (pentane). Mp: 83e84 ꢀC. 1H NMR
(500 MHz, CDCl3):
d
3.12 (s, 4H), 7.32e7.35 (td, J¼1.3, 7.6 Hz, 2H),
7.37 (t, J¼1.5 Hz, 2H), 7.40 (td, J¼1.4, 7.6 Hz, 2H), 7.43e7.48 (m, 4H),
7.58e7.68 (m, 8H), 7.84 (d, J¼7.6 Hz, 4H), 8.72 (d, J¼8.2 Hz, 2H), 8.76
(d, J¼8.2 Hz, 2H) ppm. 13C NMR (125.7 MHz, CDCl3):
d
37.9 (tꢁ 2),
122.5 (dꢁ 2), 122.8 (dꢁ 2), 126.4 (dꢁ 2), 126.5 (dꢁ 4), 126.8 (dꢁ 2),
126.9 (dꢁ 2), 127.4 (dꢁ 2), 127.6 (dꢁ 2), 127.7 (dꢁ 2), 128.3 (dꢁ 2),
128.6 (dꢁ 2), 129.9 (sꢁ 2), 130.3 (dꢁ 2), 130.5 (sꢁ 2), 131.1 (sꢁ 2),
4.3.1. 1,2-Bis-(diphenyl-4-yl)ethane 4a. Starting from 2a and 3a and
following the general procedure, pure compound 4a (0.243 mmol,
81%) was obtained as a white powder by flash chromatography on
silica gel (pentane). Mp: 191e192 ꢀC. 1H NMR (400 MHz, CDCl3):
131.5 (sꢁ 2), 138.8 (sꢁ 2), 140.8 (sꢁ 2), 141.6 (sꢁ 2) ppm. IR (neat):
n
3054, 3026, 2919, 2864, 1598, 1501, 1449, 1362, 1247, 1006, 807, 749,
698 cmꢂ1. HRMS (m/z): [M]þ calculated for C42H30, 534.2348;
found, 534.2330.
d
3.01 (s, 4H), 7.29 (t, J¼8.0 Hz, 4H), 7.34 (t, J¼7.4 Hz, 2H), 7.44 (t,
J¼7.4 Hz, 4H), 7.53 (d, J¼8.0 Hz, 4H), 7.60 (d, J¼7.4 Hz, 4H) ppm. 13C
4.3.7. 1,2-Bis-(methyl 2-phenyl-5-benzoate)ethane 4i. Starting from
2n (30 mg, 0.067 mmol) and 3a (25 mg, 0.20 mmol) and following
the general procedure with [NiCl(1-naph)(PPh3)2] (10 mol %), PPh3
(20 mol %), pure compound 4i (0.05 mmol, 75%) was obtained as
a white powder by flash chromatography on silica gel (pentane/
NMR (125.7 MHz, CDCl3):
d
37.5 (tꢁ 4), 127.0 (dꢁ 4), 127.0 (dꢁ 2),
127.1 (dꢁ 4), 127.1 (dꢁ 4), 128.7 (dꢁ 4), 128.9 (dꢁ 4), 138.9 (sꢁ 2),
140.8 (sꢁ 2), 141.0 (sꢁ 2) ppm. IR (neat):
n 3055, 3029, 2951, 2919,
2852, 1599, 1443, 1005, 833, 759, 723, 687 cmꢂ1. HRMS (m/z): [M]þ
calculated for C26H22, 334.1722; found, 334.1729.
ether: 95:5). Mp: 131e132 ꢀC. 1H NMR (400 MHz, CDCl3):
d 2.79 (s,
4H), 3.92 (s, 6H), 7.00e7.04 (m, 4H), 7.17 (d, J¼7.9 Hz, 2H), 7.32e7.36
4.3.2. 1,2-Bis-(diphenyl-3-yl)ethane 4b. Starting from 2b and 3a
and following the general procedure, pure compound 4b
(0.291 mmol, 97%) was obtained as a white powder by flash chro-
matography on silica gel (pentane). Mp: 104e105 ꢀC. 1H NMR
(m, 6H), 7.67 (d, J¼1.7 Hz, 2H), 7.85 (dd, J¼1.7, 7.9 Hz, 2H) ppm. 13C
NMR (100 MHz, CDCl3):
d
34.3 (tꢁ 2), 52.1 (qꢁ 2),127.0 (dꢁ 2),127.3
(dꢁ 4), 128.2 (dꢁ 4), 128.7 (dꢁ 2), 129.1 (sꢁ 2), 130.2 (dꢁ 2), 130.6
(dꢁ 2), 138.9 (sꢁ 2), 140.6 (sꢁ 2), 146.6 (sꢁ 2), 167.0 (sꢁ 2) ppm. IR
(500 MHz, CDCl3):
6H), 7.48e7.54 (m, 4H), 7.64e7.68 (m, 6H) ppm. 13C NMR
(125.7 MHz, CDCl3):
34.9 (tꢁ 2), 125.8 (dꢁ 2), 126.8 (dꢁ 2), 127.3
(dꢁ 2), 128.1 (dꢁ 4), 129.2 (dꢁ 4), 129.3 (dꢁ 2), 130.0 (dꢁ 2), 139.2
d
3.04 (s, 4H), 7.26e7.32 (m, 2H), 7.42e7.48 (m,
(neat): n 2941, 1719, 1575, 1435, 1292, 1253, 11,194; 1116, 757,
703 cmꢂ1. HRMS (m/z): [MþNa]þ calculated for C30H26O4Na,
d
473.1729; found, 473.1721.
(sꢁ 2), 141.8 (sꢁ 2), 142.0 (sꢁ 2) ppm. IR (neat):
n
3026, 2966, 2872,
4.3.8. 1,2-Bis-[methyl 2-(4-fluorophenyl)-5-benzoate]ethane 4j.
Starting from 2n (60 mg, 0.132 mmol) and 3a (55 mg, 0.40 mmol)
and following the general procedure with [NiCl(1-naph)(PPh3)2]
(10 mol %), PPh3 (20 mol %), pure compound 4i (0.085 mmol, 64%)
was obtained as a white powder by flash chromatography on silica
gel (pentane/ether: 95:5). Mp: 175e176 ꢀC. 1H NMR (400 MHz,
1597, 1475, 1007, 806, 749, 707 cmꢂ1. HRMS (m/z): [M]þ calculated
for C26H22, 334.1722; found, 334.1726.
4.3.3. 1,2-Bis-(diphenyl-2-yl)ethane 4c. Starting from 2c and 3a and
following the general procedure, pure compound 4c (0.213 mmol,
71%) was obtained as a white powder by flash chromatography on
silica gel (pentane). Mp: 100e101 ꢀC. 1H NMR (500 MHz, CDCl3):
CDCl3):
d 2.77 (s, 4H), 3.93 (s, 6H), 6.95 (pseudo dd,
JHF¼5.4JHH¼8.6 Hz, 4H), 7.01 (pseudo t, JHF¼JHH¼8.6 Hz, 4H), 7.14 (d,
d
3.08 (s, 4H), 7.24 (d, J¼7.3 Hz, 2H), 7.35e7.50 (m, 12H), 7.60 (d,
J¼7.9 Hz, 2H), 7.67 (d, J¼1.7 Hz, 2H), 7.85 (dd, J¼1.7, 7.9 Hz, 2H) ppm.
J¼7.5 Hz, 4H) ppm. 13C NMR (125.7 MHz, CDCl3):
d
38.1 (tꢁ 2), 124.9
13C NMR (100 MHz, CDCl3):
d
34.3 (tꢁ 2), 52.1 (qꢁ 2), 115.1 (d,
(dꢁ 2), 127.2 (dꢁ 6), 127.4 (dꢁ 2), 127.5 (dꢁ 2), 128.7 (dꢁ 4), 127.8
JCF¼21.4 Hz, 2CH), 127.1 (dꢁ 4), 129.4 (sꢁ 2), 130.3 (dꢁ 2), 130.3 (d,
JCF¼12.0 Hz, 2CH), 130.7 (dꢁ 4), 136.4 (d, JCF¼3.4 Hz, 2C), 138.9 (sꢁ
2), 145.4 (sꢁ 2), 162.2 (d, JCF¼246.7 Hz, 2CF), 166.8 (sꢁ 2) ppm. IR
(dꢁ 2), 141.3 (sꢁ 4), 142.1 (sꢁ 2) ppm. IR (neat):
n 3055, 3026, 2951,
1595, 1476, 1261, 1073, 805, 755, 692 cmꢂ1. HRMS (m/z): [M]þ cal-
culated for C26H22, 334.1722; found, 334.1728.
(neat): n 2955, 1722, 1602, 1518, 1484, 1438, 1291, 1219, 1194; 1157,
1125, 1093, 833, 765 cmꢂ1. HRMS (m/z): [MþNa]þ calculated for
4.3.4. 1,2-Bis-(40-methylbiphenyl-4-yl)ethane 4d. Starting from 2c
and 3b and following the general procedure, pure compound 4d
(0.168 mmol, 56%) was obtained as a white powder by flash chro-
matography on silica gel (pentane). Mp: 209e210 ꢀC. 1H NMR
C30H24O4F2Na, 509.1540; found, 509.1554.
4.3.9. 1,2-Bis-[methyl 2-(4-methylphenyl)-5-benzoate]ethane 4k.
Starting from 2n (60 mg, 0.132 mmol) and 3a (54 mg, 0.40 mmol)
and following the general procedure with [NiCl(1-naph)(PPh3)2]
(10 mol %), PPh3 (20 mol %), pure compound 4i (0.092 mmol, 70%)
was obtained as a white powder by flash chromatography on silica
gel (pentane/ether: 95:5). Mp: 118e120 ꢀC. 1H NMR (400 MHz,
(500 MHz, CDCl3):
7.29 (d, J¼8.1 Hz, 4H), 7.51 (d, J¼8.0 Hz, 4H), 7.53 (d, J¼8.1 Hz, 4H)
ppm. 13C NMR (125.7 MHz, CDCl3):
21.1 (qꢁ 2), 37.5 (tꢁ 2), 126.8
(dꢁ 4), 126.9 (dꢁ 4), 128.8 (dꢁ 4), 129.4 (dꢁ 4), 136.8 (sꢁ 2), 138.1
d
2.41 (s, 6H), 3.01 (s, 4H), 7.26 (d, J¼8.0 Hz, 4H),
d
(sꢁ 2), 138.8 (sꢁ 2), 140.6 (sꢁ 2) ppm. IR (neat):
n
3025, 2918, 2854,
CDCl3):
7.16 (t, J¼8.0 Hz, 6H), 7.69 (d, J¼1.7 Hz, 2H), 7.83 (dd, J¼1.7, 8.0 Hz, 2H)
ppm. 13C NMR (100 MHz, CDCl3):
d
2.41 (s, 6H), 2.81 (s, 4H), 3.92 (s, 6H), 6.93 (d, J¼8.0 Hz, 4H),
1500, 1260, 1112, 1004, 805, 759 cmꢂ1. HRMS (m/z): [M]þ calculated
for C28H26, 362.2035; found, 362.2018.
d
21.2 (qꢁ 2) 34.3 (tꢁ 2), 52.0 (qꢁ
2),126.9 (dꢁ 2),128.6 (dꢁ 4),128.8 (dꢁ 4),128.9 (sꢁ 2),130.2 (dꢁ 2),
4.3.5. 1,2-Bis-(4-(naphtalen-1-yl)phenyl)ethane 4e.33 Starting from
2a and 3c and following the general procedure, pure compound 4e
(0.255 mmol, 85%) was obtained as a white powder by flash chro-
matography on silica gel (pentane). 1H NMR (500 MHz, CDCl3):
130.6 (dꢁ 2), 136.9 (sꢁ 2), 137.7 (sꢁ 2), 139.0 (sꢁ 2), 146.6 (sꢁ 2),
167.0 (sꢁ 2) ppm. IR (neat):
n 2949, 1720, 1607, 1522, 1487, 1435,
1250, 1194; 1158, 1110, 1006, 819, 770 cmꢂ1. HRMS (m/z): [MþNa]þ
calculated for C32H30O4Na 501.2042; found, 501.2032.
d
3.14 (s, 4H), 7.40 (d, J¼6.4 Hz, 4H), 7.45e7.47 (m, 6H), 7.49e7.51
(m, 4H), 7.53e7.55 (m, 2H), 7.89 (d, J¼8.2 Hz, 2H), 7.94 (d, J¼9.1 Hz,
2H), 7.99 (d, J¼8.4 Hz, 2H) ppm.
4.3.10. 1,2-Bis-[methyl 2-(4-naphtyl)-5-benzoate]ethane 4l. Starting
from 2n (60 mg, 0.132 mmol) and 3a (68 mg, 0.40 mmol) and fol-
lowing the general procedure with [NiCl(1-naph)(PPh3)2]
(10 mol %), PPh3 (20 mol %), pure compound 4i (0.092 mmol, 70%)
was obtained as a white powder by flash chromatography on silica
gel (pentane/ether: 95:5). 1H NMR (400 MHz, CDCl3)
4.3.6. 1,2-Bis-(3-(phenanthren-9-yl)phenyl)ethane 4h. Starting from
2b and 3f and following the general procedure, pure compound 4h
(0.258 mmol, 86%) was obtained as a white powder by flash

4882
C.D. Mboyi et al. / Tetrahedron 69 (2013) 4875e4882
2093e2098; (c) Prinsell, M. R.; Everson, D. A.; Weix, D. J. Chem. Commun. 2010,
diastereomeric mixture:
d 2.34e2.48 (m, 4H), 2.52e2.62 (m, 4H),
5743e5745.
3,93 (s, 6H), 3.94 (s, 6H), 6.71 (dd, J¼1.0, 7.0 Hz, 2H), 6.85 (dd, J¼1.0,
7.0 Hz, 2H), 7.13 (d, J¼8.5 Hz, 4H), 7.16 (d, J¼7.9 Hz, 4H), 7.21e7.30
(m, 6H), 7.36 (dd, J¼7.0, 8.2 Hz, 2H), 7.42e7.49 (m, 4H), 7.58 (d,
J¼1.7 Hz, 4H), 7.81 (d, J¼8.2 Hz, 2H), 7.82e7.90 (m, 10H) ppm. 13C
9. Ranu, B. C.; Dutta, P.; Sarkar, A. Tetrahedron Lett. 1998, 39, 9557e9558.
10. Okude, Y.; Hiyama, T.; Hitosi, N. Tetrahedron Lett. 1977, 18, 3829e3830.
11. Lindsay, W. S.; Stokes, P.; Humber, L. G.; Boekelheide, V. J. Am. Chem. Soc. 1961,
83, 943e949.
12. (a) Iyoda, M.; Sakaitani, M.; Otsuka, H.; Oda, M. Chem. Lett. 1985, 127e130; (b)
Goldup, S. M.; Leigh, D. A.; McBurney, R. T.; McGonigal, P. R.; Plant, A. Chem. Sci.
2010, 1, 383e386; (c) Chen, T.; Yang, L.; Li, L.; Huang, K.-W. Tetrahedron 2012,
68, 6152e6157.
NMR (100 MHz, CDCl3) diastereomeric mixture:
d
34.5 (tꢁ 2), 34.6
(tꢁ 2), 52.0 (qꢁ 2), 52.1 (qꢁ 2), 125.0 (dꢁ 2), 125.1 (dꢁ 2), 125.5 (dꢁ
2), 125.6 (dꢁ 2), 125.8 (dꢁ 4), 126.2 (dꢁ 2), 126.2 (dꢁ 2), 126.4 (dꢁ
4),126.9 (dꢁ 2),127.0 (dꢁ 2),127.8 (dꢁ 4),128.2 (dꢁ 4),129.4 (sꢁ 2),
129.5 (sꢁ 2), 130.3 (dꢁ 2), 130.3 (dꢁ 2), 130.8 (dꢁ 4), 131.6 (sꢁ 2),
131.6 (sꢁ 2), 133.3 (sꢁ 4), 137.8 (sꢁ 2), 137.9 (sꢁ 2), 140.2 (sꢁ 2),
13. For a review on activation of benzylic derivatives by palladium complexes, see:
ꢁ
(a) Liegault, B.; Renaud, J.-L.; Bruneau, C. Chem. Soc. Rev. 2008, 37, 290e299 For
the syntheses of dibenzyl derivatives from benzylic zinc halides, see: (b) Lei, A.;
Zhang, X. Org. Lett. 2002, 4, 2285e2288.
14. (a) Cahiez, G.; Moyeux, A.; Buendia, J.; Duplais, C. J. Am. Chem. Soc. 2007, 129,
13788e13789; (b) Yuan, Y.; Bian, Y. Appl. Organomet. Chem. 2008, 22, 15e18; (c)
Zhou, Z.; Xue, W. J. Organomet. Chem. 2009, 694, 599e603 For an example of the
use of half equivalent of a highly activated manganese, see: (d) Suh, Y.-S.; Lee,
J.-S.; Kim, S.-H.; Rieke, R. D. J. Organomet. Chem. 2003, 684, 20e36.
15. Barrero, A. F.; Herrador, M. M.; Quílez del Moral, J. F.; Arteaga, P.; Akssira, M.; El
140.3 (sꢁ 2), 144.7 (sꢁ 2), 144.8 (sꢁ 2), 167.0 (sꢁ 4) ppm. IR (neat):
n
2949, 1721, 1607, 1435, 1407, 1291, 1255, 1195, 1113, 986, 910, 849,
779 cmꢂ1. HRMS (m/z): [MþH]þ calculated for C38H30O4, 551.2222;
found, 551.2247.
ꢁ
ꢁ
Hanbali, F.; Arteaga, J. F.; Dieguez, H. R.; Sanchez, E. M. J. Org. Chem. 2007, 72,
2251e2254.
Acknowledgements
16. Xu, X.; Cheng, D.; Pei, W. J. Org. Chem. 2006, 71, 6637e6639.
17. Chen, S.-Y.; Zhang, J.; Li, Y.-H.; Wen, J.; Bian, S.-Q.; Yu, X.-Q. Tetrahedron Lett.
2009, 50, 6795e6797.
The authors thank Oril Industries for a Post-Doc. fellowship for
18. (a) Rosen, B. M.; Quasdorf, K. W.; Wilson, D. A.; Zhang, N.; Resmerita, A.-M.;
Garg, N. K.; Percec, V. Chem. Rev. 2011, 111, 1346e1416; (b) Jeganmohan, M.;
Cheng, C.-H. Chem.dEur. J. 2008, 14, 10876e10886; (c) Ho, C.-Y.; He, L.; Chan,
C.-W. Synlett 2011, 1649e1653; (d) Montgomery, J. Angew. Chem., Int. Ed. 2004,
43, 3890e3908; (e) Johnson, J. B.; Rovis, T. Acc. Chem. Res. 2008, 41, 327e338.
19. For nickel-catalyzed Suzuki cross-coupling reaction, see: (a) Chen, C.; Yang,
L.-M. Tetrahedron Lett. 2007, 48, 2427e2430; (b) Fan, X.-H.; Yang, L.-M. Eur. J.
Org. Chem. 2010, 2457e2460; (c) Fan, X.-H.; Yang, L.-M. Eur. J. Org. Chem. 2011,
1467e1471 For a recent example of Suzuki reaction catalyzed by nickel com-
plex on fluorinated aromatic compounds, see: (d) Tobisu, M.; Xu, T.; Shimasaki,
T.; Chatani, N. J. Am. Chem. Soc. 2011, 133, 19505e19511.
N.P. This work has also been performed within the ‘CRUNCH’ in-
ꢀ
terregional network. The ‘Ministere de la Recherche et des Nouvelles
Technologies’, CNRS (Centre National de la Recherche Scientifique),
ꢁ
the ‘Region Basse-Normandie’ and the European Union (FEDER
funding) are gratefully acknowledged for financial supports.
References and notes
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