Cross coupling between sp3-carbon and sp3-carbon using a diborylmethane derivative at room temperature

Article abstract of DOI:10.1021/jo3004293

A novel example of the Suzuki-Miyaura cross-coupling reaction between sp³-carbon and sp³-carbon is described. The reaction of a diborylmethane derivative with allyl halides or benzyl halides proceeded efficiently in the presence of appropriate Pd-catalysts at room temperature. The present approaches provide functionalized homoallylboronates and alkylboronates with excellent regio- and chemoselectivities.

Full text of DOI:10.1021/jo3004293

Note
pubs.acs.org/joc
Cross Coupling between sp3-Carbon and sp3-Carbon Using a
Diborylmethane Derivative at Room Temperature
Kohei Endo,*,†,‡ Takahiro Ohkubo,§ Takafumi Ishioka,§ and Takanori Shibata*,§
†Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa
920-1192, Japan
‡PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan
§Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo
169-8555, Japan
S
* Supporting Information
ABSTRACT: A novel example of the Suzuki−Miyaura cross-
coupling reaction between sp3-carbon and sp3-carbon is
described. The reaction of a diborylmethane derivative with
allyl halides or benzyl halides proceeded efficiently in the
presence of appropriate Pd-catalysts at room temperature. The
present approaches provide functionalized homoallylboronates
and alkylboronates with excellent regio- and chemoselectiv-
ities.
ross-coupling reactions have been widely developed for
room temperature.10 The coupling of a diborylmethane
derivative and aryl halides provides benzylboronate derivatives,
which do not undergo a further coupling reaction. In the
present paper, we describe the expedient coupling using a
diborylmethane derivative and allyl or benzyl halides under
ambient conditions, which gives alkylboron compounds
chemoselectively (Figure 1).
1
Cthe synthesis of various compounds in organic chemistry.
Among the cross-coupling approaches, the Suzuki−Miyaura
cross-coupling reaction (SMC) contributes to a C−C bond
formation under mild conditions.2 While there have been
numerous reports on the SMC between organoboron
compounds and organohalides, the reaction between alkylbor-
on compounds and alkyl halides is typically difficult to achieve.
In 1992, Suzuki et al. reported the first example of the alkyl−
alkyl cross-coupling reaction between alkylboron compounds
and alkyl iodides.3 Fu et al. reported pioneering work on
efficient Ni- or Pd-catalyzed approaches for which secondary
alkyl halides could be available.4 Organ reported that the
originally developed Pd complexes, the PEPPSI series, could
catalyze the coupling of primary alkylboron compounds and
primary alkyl bromides in high to excellent yields.5,6 Molander
reported the Suzuki−Miyaura cross-coupling of cyclopropyl
and alkoxymethyltrifluoroborates with benzyl chlorides at 120
°C.7 However, the reaction of alkylboron compounds with
allyl(benzyl) halides is difficult due to the slow reaction rate of
transmetalation as well as the slow reductive elimination.8
Hence, the coupling reaction of alkylboron compounds and
allyl(benzyl) halides has been unfavorable for the following
reasons: (1) slow borate generation from alkylboron com-
pounds, (2) slow transmetalation step, (3) slow reductive
elimination step, and (4) a competitive pathway via β-hydride
elimination. These factors are still controversial but could
explain why there are only limited examples of the SMC of
alkylboron compounds with allyl(benzyl) halides.9 In our
ongoing study on the SMC, we discovered that the reaction of
diborylmethane derivatives, two boron atoms of which are
attached to the same carbon atom, realized unprecedented
chemoselective and regiospecific coupling with aryl halides at
Figure 1. SMC of Diborylmethane and Allyl(Benzyl)halides.
Allylation. Pd-catalyzed allylation is one of the most
powerful approaches to the synthesis of various functionalized
molecules.11 Although it has been shown to be useful in C−C
bond formation, the SMC of alkylboron compounds with allyl
halides has rarely been reported.12,13 Consequently, we report
here the alkyl−allyl SMC using a diborylmethane at room
temperature. The initial screening of catalyst precursors for the
coupling of diborylmethane derivative 1 and (E)-cinnamyl
bromide (2a) is described in Table 1. The palladium complex
Pd[P(t-Bu)3]2, which has been shown to be effective for
promoting various coupling reactions, realized the SMC
between diborylmethane 1 and (E)-cinnamyl bromide (2a) at
Received: February 29, 2012
© XXXX American Chemical Society
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dx.doi.org/10.1021/jo3004293 | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Note
Other leaving group, such as hydroxide, alkoxide, acetate and
triflate did not give the product. The starting materials were
recovered in each case. Thus, the further coupling reaction of
allyl bromides was carried out in the presence of Pd-PEPPSI-
IPr catalyst.
Table 1. Screening of Catalyst for Allylation
A variety of allyl bromides were examined under the
optimum reaction conditions (Table 2).17−19 The reaction of
Table 2. Scope of Allyl Bromide Derivatives
a
entry
R, R′
2a, Ph, H
time (h)
yield (%)
b
1
2
6
5
3a, 82 (85)
3b, 88
3c, 89
3d, 92
3e, 74
3f, 32
2b, 4-MePh, H
2c, 4-t-BuPh, H
2d, 4-MeOPh, H
2e, 4-ClPh, H
2f, 4-F3CPh, H
2g, 2-thienyl, H
2h, 2-Np, H
3
24
6
4
5
24
24
24
24
24
24
6
7
3g, 39
3h, 70
3i, 75
8
9
2i, Ph, Me
10
2j, (CH2)2Ph, H
3j, 51
a
b
2a−i (0..07−0.23 mmol) was used. The yield of reaction for 24 h
using 2a (5 mmol) is shown in parentheses.
(E)-cinnamyl bromide (2a) gave the product 3a in 82% yield;
the larger scale reaction (5 mmol of 2a) achieved 85% yield of
product 3a (entry 1). Electron-donating groups are compatible
with the reaction. The reaction of cinnamyl bromide derivatives
2b−d bearing a 4-methyl, 4-tert-butyl, or 4-methoxy group gave
the corresponding products 3b−d in high yields (entries 2−4).
In contrast, electron-withdrawing groups diminished the yield
of products 3e and 3f (entries 5 and 6). Furthermore, a
heteroaromatic substituent, such as thiophene, retarded the
reaction and generated unidentified byproduct (entry 7). The
naphthyl derivative 2h gave the product 3h in 70% yield (entry
8). To our delight, the reaction of (E)-(3-bromobut-1-en-1-
yl)benzene (2i) gave the product 3i regioselectively without the
generation of byproduct via β-hydride elimination (entry 9).20
The aliphatic allyl bromide 2j gave the desired product 3j in
moderate yield (entry 10).
Benzylation. The typical cross-coupling reaction of
arylboron compounds and benzyl halides has been envisaged
as a promising method for C−C bond formation.12a−d We
examined the reaction of diborylmethane 1 with benzyl
bromide (4a) for the synthesis of phenethylboronate 5a
(Table 3). The generation of η3-benzylpalladium complexes has
been proposed in the literature.21 The screening of catalyst
precursors was carried out. The use of Pd[P(t-Bu)3]2 gave the
desired product 5a in excellent yield (entry 1). Other palladium
complexes were less effective; the reaction in the presence of (t-
Bu)2MePH+BF4− with Pd(OAc)2 did not give the product at all
( e n t r y 2 ) . T h e u s e o f b i s [ d i - t e r t - b u t y l ( 4 -
dimethylaminophenyl)phosphine]dichloropalladium(II) gave
the product in low yield (entry 3). The reaction in the
presence of [bis(di-tert-butylphosphino)ferrocene]-
a
NMR yields.
room temperature, and gave the homoallylboronate 3a in
moderate yield; product 3a was obtained regioselectively as
(E)-isomer at the α-carbon of the allylic position (entry 1). The
efficient catalyst precursor, (t-Bu)2MePH+BF4− with Pd(OAc)2,
for the cross-coupling of alkyl bromides did not promote the
present reaction at all (entry 2).4b The use of bis[di-tert-
butyl(4-dimethylaminophenyl)phosphine]dichloropalladium-
(II) gave the desired product 3a, but in low yield (entry 3).14
The use of [bis(di-tert-butylphosphino)ferrocene]-
dichloropalladium(II) required a long reaction time (24 h)
and gave the product 3a in high yield (entry 4). Finally, Pd-
PEPPSI-IPr catalyst achieved the efficient cross-coupling
reaction; product 3a was obtained in almost quantitative yield
(entry 5). The precedent literatures suggested that mono-
dentate ligands could give a π-allylpalladium intermediate,
which undergoes subsequent transmetalation. In contrast,
bidentate ligands require rearrangement of a π-allylpalladium
intermediate to a relatively unstable σ-allylpalladium inter-
mediate before transmetalation, which seems to retard the
reaction rate.15 Thus, the NHC ligand in Pd-PEPPSI-IPr would
be superior to bis(di-tert-butylphosphino)ferrocene. The
reductive elimination step is another problem. Phosphorus
ligands would retard the reductive elimination step; thus, the
NHC ligand might work in the present reaction at room
temperature.8,16 We examined various leaving groups; the
reaction of cinnamyl diethyl phosphate and cinnamyl chloride
in the presence of Pd-PEPPSI-IPr catalyst gave the desired
product after 24 h in 11% yield and 12% yield, respectively.
B
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Note
Table 3. Screening of Catalyst for Benzylation
Table 4. Scope of Benzyl Halide Derivatives
a
entry
Ar
time (h)
yield (%)
b
1
2
3
4
5
6
7
8
9
4a, Ph
2.5
5
5a, 93 (89)
5b, 85
5c, 89
5d, 86
5e, 89
5f, 70
4b, 4-MePh
4c, 4-t-BuPh
4d, 4-ClPh
4e, 4-FPh
24
5
2
4f, 3-O2NPh
4g, 4-NCPh
4h, 4-MeO2CPh
4i, 2-Np
5
5
5g, 85
5h, 77
5i, 80
24
24
a
b
4a−i (0.1−0.15 mmol) was used. The yield of reaction for 24 h
using 4a (5 mmol) is shown in parentheses.
chemoselective coupling reaction proceeded under mild
conditions to give alkylboron compounds without the
generation of byproduct via protodeboronation or β-hydride
elimination. The present SMC realizes the incorporation of a
boronate moiety along with a C−C bond formation via
borylmethylation, which would be alternative to hydroboration
reactions of alkenes with a C−B and a C−H bond formation.
These characteristic features using diborylmethane derivatives
are promising for the further synthetic utility of facile Suzuki−
Miyaura cross-coupling approaches to a C−C bond formation.
EXPERIMENTAL SECTION
a
■
NMR yields.
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(4-phenylbut-3-en-1-
yl)-1,3,2-dioxaborolane (3a). To a solution of 1 (38.0 mg, 0.140
mmol, 2 equiv), 2a (13.8 mg, 0.070 mmol), and Pd-PEPPSI-IPr (2.5
mg, 3.5 μmol, 5 mol %) in dioxane 0.75 mL was added 8 N KOH aq
(18 μL, 0.14 mmol, 2 equiv) at room temperature. The mixture was
stirred for 6 h and filtered through a pad of silica gel with ether.
Concentration gave the residue, the NMR yield of which was
determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/ether = 10/1) gave the
product 3a in 0.057 mmol, 82% yield (14.8 mg/18.1 mg); the reaction
using 1 (2.68 g, 10 mmol, 2 equiv) and 2a (986 mg, 5 mmol) in the
presence of Pd-PEPPSI-IPr (170 mg, 0.25 mmol, 5 mol %) and 8 N
KOH aq (1.25 mL, 10 mmol, 2 equiv) in dioxane 50 mL for 24 h at
room temperature gave the product 3a in 4.25 mmol, 85% yield (1.1
dichloropalladium(II) did not improve the yield of the product
(entry 4). Unexpectedly, Pd-PEPPSI-IPr gave a trace amount of
product (entry 5). Thus, we determined that Pd[P(t-Bu)3]2 is a
suitable catalyst for the benzylation reaction. We examined
leaving groups; the reaction of benzyl chloride gave the desired
product 5a in 85% yield. Other leaving groups, such as
hydroxide, alkoxide, acetate, carbonate, triflate, phosphate, and
so on, were not suitable. The starting materials were recovered
along with a slow decomposition of diborylmethane.
A variety of benzyl bromide derivatives were examined under
the optimum reaction conditions (Table 4).19,22 The reaction
of benzyl bromide (4a) gave the desired product 5a in 93%
yield; the larger scale (5 mmol of 4a) reaction gave the desired
product 5a in 89% yield (entry 1).23 The reaction of benzyl
bromide derivatives 4b and 4c bearing an electron-donating
group at the 4-position gave the desired products 5b and 5c in
high yields (entries 2 and 3). Furthermore, electron-with-
drawing groups are compatible with the reaction. The reaction
of 4-chloro- and 4-fluorobenzyl bromides 4d and 4e gave the
desired products 5d and 5e in high yields (entries 4 and 5).
The incorporation of 3-nitro, 4-cyano, and 4-methoxycarbonyl
groups did not decrease the yields of the products 5f−h
(entries 6−8). The reaction of 2-(bromomethyl)naphthalene
(4i) gave the corresponding product 5i in 80% yield (entry 9).
In summary, we have achieved the efficient Suzuki−Miyaura
cross-coupling reaction of a diborylmethane derivative and allyl
halides or benzyl halides under ambient conditions. The
1
g/1.29 g): yellow oil; H NMR (CDCl3, 400 MHz) δ 7.36−7.16 (m,
5H), 6.39 (d, J = 15.6 Hz, 1H), 6.29 (dt, J = 6.4 Hz, 15.6 Hz, 1H),
2.37−2.32 (m, 2H), 1.25 (s, 12H), 0.99 (t, J = 7.6 Hz, 2H); 13C NMR
(CDCl3, 100 MHz) δ 137.9, 132.7, 128.8, 128.4, 126.6, 125.9, 83.1,
27.3, 24.8; 11B NMR (CDCl3, 128 MHz) δ 34.2; IR (neat, cm−1) 2978,
2929, 1445, 1323, 1145, 966, 848, 742; HRMS (FAB, positive) m/z
calcd for C16H2310BO2 257.1827, found 257.1829.
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(4-p-tolylbut-3-en-1-
yl)-1,3,2-dioxaborolane (3b). To a solution of 1 (55.0 mg, 0.21
mmol, 2 equiv), 2b (21.7 mg, 0.10 mmol), and Pd-PEPPSI-IPr (3.5
mg, 5.2 μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq
(25 μL, 0.21 mmol, 2 equiv) at room temperature. The mixture was
stirred for 5 h and filtered through a pad of silica gel with ether.
Concentration gave the residue, the NMR yield of which was
determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/ether = 20/1) gave the
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The Journal of Organic Chemistry
Note
product 3b in 0.091 mmol, 88% yield (24.5 mg/28.0 mg): yellow oil;
1H NMR (CDCl3, 400 MHz) δ 7.22 (d, J = 8.0 Hz, 2H), 7.08 (d, J =
residue, the NMR yield of which was determined to be 37% by the
integration ratio of the crude NMR with 1,1,2,2-tetrachloroethane as
an internal standard. Purification by silica gel column chromatography
(hexane/ether = 20/1) gave the product 3f in 0.068 mmol, 32% yield
8.0 Hz, 2H), 6.34 (d, J = 15.6 Hz, 1H), 6.22 (dt, J = 6.4 Hz, 15.6 Hz,
1H), 2.35−2.29 (m, 5H), 1.24 (s, 12H), 0.97 (t, J = 7.6 Hz, 2H); 13C
NMR (CDCl3, 100 MHz) δ 136.3, 135.2, 131.7, 129.1, 128.6, 125.8,
83.0, 27.3, 24.8, 21.1; 11B NMR (CDCl3, 128 MHz) δ 34.4; IR (neat,
cm−1) 2978, 2929, 1444, 1320, 1143, 966, 848; HRMS (FAB, positive)
m/z calcd for C17H2510BO2 271.1984, found 271.1976.
Synthesis of (E)-2-(4-(4-tert-Butylphenyl)but-3-en-1-yl)-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3c). To a solution of
1 (104 mg, 0.39 mmol, 2 equiv), 2c (49.1 mg, 0.19 mmol), and Pd-
PEPPSI-IPr (6.6 mg, 9.7 μmol, 5 mol %) in dioxane (1.9 mL) was
added 8 N KOH aq (46 μL, 0.39 mmol, 2 equiv) at room temperature.
The mixture was stirred for 6 h and filtered through a pad of silica gel
with ether. Concentration gave the residue, the NMR yield of which
was determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/ether = 20/1) gave the
product 3c in 0.173 mmol, 89% yield (54.1 mg/61.0 mg): yellow oil;
1H NMR (CDCl3, 400 MHz) δ 7.33−7.25 (m, 4H), 6.35 (d, J = 16.0
Hz, 1H), 6.23 (dt, J = 6.4 Hz, 16.0 Hz, 1H), 2.35−2.29 (m, 2H), 1.30
(s, 9H), 1.24 (s, 12H), 0.97 (t, J = 7.6 Hz, 2H); 13C NMR (CDCl3,
100 MHz) δ 149.6, 135.2, 132.0, 128.4, 125.6, 125.3, 83.0, 34.4, 31.3,
27.3, 24.8; 11B NMR (CDCl3, 128 MHz) δ 34.2; IR (neat, cm−1) 2966,
2929, 2359, 1372, 1323, 1146, 967, 847, 748; HRMS (FAB, positive)
m/z calcd for C20H3110BO2 313.2453, found 313.2445.
Synthesis of (E)-2-(4-(4-Methoxyphenyl)but-3-en-1-yl)-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3d). To a solution of
1 (107 mg, 0.4 mmol, 2 equiv), 2d (45.4 mg, 0.2 mmol), and Pd-
PEPPSI-IPr (6.8 mg, 10 μmol, 5 mol %) in dioxane (2.0 mL) was
added 8 N KOH aq (48 μL, 0.4 mmol, 2 equiv) at room temperature.
The mixture was stirred for 6 h and filtered through a pad of silica gel
with ether. Concentration gave the residue, the NMR yield of which
was determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/ether = 20/1) gave the
product 3d in 0.184 mmol, 92% yield (52.8 mg/57.4 mg): yellow oil;
1H NMR (CDCl3, 400 MHz) δ 7.27−7.25 (m, 2H), 6.82 (d, J = 8.4
1
(22.4 mg/69.2 mg): yellow oil; H NMR (CDCl3, 400 MHz) δ 7.52
(d, J = 8.0 Hz, 2H), 7.41 (d, J = 8.4 Hz, 2H), 6.40−6.39 (m, 2H),
2.37−2.35 (m, 2H), 1.25 (s, 12H), 1.00 (t, J = 7.6 Hz, 2H); 13C NMR
(CDCl3, 100 MHz) δ 141.4, 135.6, 128.5 (q, J = 32.3 Hz), 127.7,
126.0, 125.3 (q, J = 4.1 Hz), 124.3 (q, J = 272.3 Hz), 83.1, 27.3, 24.8;
11B NMR (CDCl3, 128 MHz) δ 34.4; 19F NMR (CDCl3, 470 MHz) δ
−64.4; IR (neat, cm−1) 2979, 2929, 1373, 1325, 1144, 968, 848, 749;
HRMS (FAB, positive) m/z calcd for C17H2210BF3O2 325.1701, found
325.1686.
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(4-(thiophene-2-yl)-
but-3-en-1-yl)-1,3,2-dioxaborolane (3g). To a solution of 1
(106.0 mg, 0.4 mmol, 2 equiv), 2g (40.5 mg, 0.2 mmol), and Pd-
PEPPSI-IPr (6.8 mg, 10 μmol, 5 mol %) in dioxane (2.0 mL) was
added 8 N KOH aq (47 μL, 0.4 mmol, 2 equiv) at room temperature.
The mixture was stirred for 24 h and filtered through a pad of silica gel
with ether. Concentration gave the residue, the NMR yield of which
was determined to be 48% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/ether = 20/1) gave the
product 3g in 0.078 mmol, 39% yield (20.8 mg/52.6 mg): yellow oil;
1H NMR (CDCl3, 400 MHz) δ 7.07 (d, J = 5.2 Hz, 1H), 6.94−6.90
(m, 1H), 6.86−6.83 (m, 1H), 6.50 (d, J = 15.6 Hz, 1H), 6.13 (dt, J =
6.4 Hz, 15.6 Hz, 1H), 2.31−2.29 (m, 2H), 1.25 (s, 12H), 0.97 (t, J =
7.6 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ 132.7, 128.8, 127.1,
124.0, 122.9, 122.1, 83.1, 27.0, 24.8; 11B NMR (CDCl3, 128 MHz) δ
34.3; IR (neat, cm−1) 2978, 2934, 1730, 1378, 1275, 1145, 965, 848,
749; HRMS (FAB, positive) m/z calcd for C14H2110BO2S 263.1392,
found 263.1392.
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(4-(naphthalen-2-yl)-
but-3-en-1-yl)-1,3,2-dioxaborolane (3h). To a solution of 1 (66.0
mg, 0.25 mmol, 2 equiv), 2h (30.6 mg, 0.12 mmol), and Pd-PEPPSI-
IPr (4.2 mg, 6.2 μmol, 5 mol %) in dioxane (1.2 mL) was added 8 N
KOH aq (29 μL, 0.25 mmol, 2 equiv) at room temperature. The
mixture was stirred for 24 h and filtered through a pad of silica gel with
ether. Concentration gave the residue, the NMR yield of which was
determined to be 80% by the integration ratio of the crude NMR with
1,1,2,2-tetrachloroethane as an internal standard. Purification by silica
gel column chromatography (hexane/ether = 20/1) gave the product
3h in 0.087 mmol, 70% yield (26.7 mg/38.2 mg): yellow oil; 1H NMR
(CDCl3, 400 MHz) δ 7.81−7.36 (m, 7H), 6.54 (d, J = 16.0 Hz, 1H),
6.42 (dt, J = 6.0 Hz, 16.0 Hz, 1H), 2.41−2.436 (m, 2H), 1.26 (s, 12H),
1.03 (t, J = 7.6 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ 135.4, 133.2,
132.6, 128.9, 128.8, 128.0, 127.8, 127.6, 126.0, 125.3, 125.3, 123.6,
83.1, 27.4, 24.8; 11B NMR (CDCl3, 128 MHz) δ 34.2; IR (neat, cm−1)
2977, 2927, 1735, 1372, 1322, 1145, 967, 847, 747; HRMS (FAB,
positive) m/z calcd for C20H26BO2 [M + H]+ 309.2026, found
309.2019.
Hz, 2H), 6.32 (d, J = 15.6 Hz, 1H), 6.13 (dt, J = 6.4 Hz, 15.6 Hz, 1H),
3.79 (s, 3H), 2.34−2.29 (m, 2H), 1.23 (s, 12H), 0.97 (t, J = 7.6 Hz,
2H); 13C NMR (CDCl3, 100 MHz) δ 158.5, 130.8, 130.6, 128.1,
127.0, 113.8, 83.0, 55.2, 27.3, 24.8; 11B NMR (CDCl3, 128 MHz) δ
33.5; IR (neat, cm−1) 2978, 2926, 1372, 1247, 1144, 967, 847, 749;
HRMS (FAB, positive) m/z calcd for C17H2510BO3 287.1933, found
287.1932.
Synthesis of (E)-2-(4-(4-Chlorophenyl)but-3-en-1-yl)-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane (3e). To a solution of 1 (64.0
mg, 0.24 mmol, 2 equiv), 2e (28.1 mg, 0.12 mmol), and Pd-PEPPSI-
IPr (4.1 mg, 6.1 μmol, 5 mol %) in dioxane (1.2 mL) was added 8 N
KOH aq (29 μL, 0.24 mmol, 2 equiv) at room temperature. The
mixture was stirred for 4 h and filtered through a pad of silica gel with
ether. Concentration gave the residue, the NMR yield of which was
determined to be 76% by the integration ratio of the crude NMR with
1,1,2,2-tetrachloroethane as an internal standard. Purification by silica
gel column chromatography (hexane/ether = 20/1) gave the product
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(2-methyl-4-phenyl-
but-3-en-1-yl)-1,3,2-dioxaborolane (3i). To a solution of 1 (122.0
mg, 0.46 mmol, 2 equiv), 2i (48.4 mg, 0.23 mmol), and Pd-PEPPSI-
IPr (7.8 mg, 11 μmol, 5 mol %) in dioxane 2.3 mL was added 8 N
KOH aq (54 μL, 0.46 mmol, 2 equiv) at room temperature. The
mixture was stirred for 24 h and filtered through a pad of silica gel with
ether. Concentration gave the residue; purification by silica gel column
chromatography (hexane/ether = 20/1) gave the product 3i in 0.172
1
3e in 0.90 mmol, 74% yield (26.3 mg/35.4 mg): yellow oil; H NMR
(CDCl3, 400 MHz) δ 7.25−7.21 (m, 4H), 6.33 (d, J = 16.0 Hz, 1H),
6.25 (dt, J = 6.0 Hz, 16.0 Hz, 1H), 2.35−2.29 (m, 2H), 1.23 (s, 12H),
0.98 (t, J = 7.6 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ 136.4, 133.5,
132.1, 128.5, 127.6, 127.1, 83.1, 27.3, 24.8; 11B NMR (CDCl3, 128
MHz) δ 34.0; IR (neat, cm−1) 2979, 2929, 2359, 1372, 1145, 967, 847,
748; HRMS (FAB, positive) m/z calcd for C16H22BClO2 292.1401,
found 292.1395.
Synthesis of (E)-4, 4,5, 5-Tetramethyl-2-(4-(4-
(trifluoromethyl)phenyl)but-3-en-1-yl)-1,3,2-dioxaborolane
(3f). To a solution of 1 (114.0 mg, 0.43 mmol, 2 equiv), 2f (56.6 mg,
0.21 mmol), and Pd-PEPPSI-IPr (7.2 mg, 10.7 μmol, 5 mol %) in
dioxane (2.1 mL) was added 8 N KOH aq (51 μL, 0.43 mmol, 2
equiv) at room temperature. The mixture was stirred for 24 h and
filtered through a pad of silica gel with ether. Concentration gave the
1
mmol, 75% yield (46.5 mg/62.3 mg): yellow oil; H NMR (CDCl3,
400 MHz) δ 7.38−7.14 (m, 5H), 6.37 (d, J = 15.6 Hz, 1H), 6.21 (dt, J
= 7.2 Hz, 15.6 Hz, 1H), 2.67−2.59 (m, 1H), 1.24 (s, 12H), 1.14 (d, J =
6.4 Hz, 3H), 0.97 (t, J = 8.0 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ
138.1, 137.9, 128.4, 126.8, 125.9, 83.0, 33.3, 24.8, 24.8, 22.9; 11B NMR
(CDCl3, 128 MHz) δ 34.2; IR (neat, cm−1) 2977, 2924, 1370, 1323,
1145, 966, 848, 748, 693; HRMS (FAB, positive) m/z calcd for
C17H2510BO2 271.1984, found 271.1994.
Synthesis of (E)-4,4,5,5-Tetramethyl-2-(2-methyl-4-phenyl-
but-3-en-1-yl)-1,3,2-dioxaborolane (3j). To a solution of diboryl-
methane 1a (102.4 mg, 0.38 mmol, 2 equiv), 2j (43.0 mg, 0.19 mmol),
D
dx.doi.org/10.1021/jo3004293 | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Note
and Pd-PEPPSI-IPr (6.6 mg, 9.7 μmol, 5 mol %) in dioxane (1.9 mL)
was added 8 N KOH aq (46 μL, 0.38 mmol, 2 equiv) at room
temperature. The mixture was stirred at 25 °C for 24 h and filtered
through a pad of silica gel with ether. Concentration gave the residue,
the NMR yield of which was determined to be 79% by the integration
ratio of the crude NMR with 1,1,2,2-tetrachloroethane as an internal
standard. Purification by silica gel column chromatography (hexane/
ether = 30/1) gave the product 3j in 0.0978 mmol, 51% yield (28.0
Synthesis of 2-(4-Fluorophenethyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (5e). To a solution of 1 (54 mg, 0.2 mmol,
2 equiv), 4e (19.2 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg, 5.0
μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24 μL,
0.2 mmol, 2 equiv) at room temperature. The mixture was stirred for 2
h and filtered through a pad of silica gel with ether. Concentration
gave the residue, the NMR yield of which was determined to be >98%
by the integration ratio of the crude NMR with 1,1,2,2-tetrachloro-
ethane as an internal standard. Purification by silica gel column
chromatography (hexane/EtOAc = 10/1) gave the product 5e in
1
mg/54.7 mg): yellow oil; H NMR (CDCl3, 400 MHz) δ 7.29−7.24
(m, 2H), 7.19−7.15 (m, 3H), 5.53−5.44 (m, 2H), 2.65 (t, J = 7.8 Hz,
2H), 2.32−2.25 (m, 2H), 2.14−2.07 (m, 2H), 1.24 (s, 12H), 0.85 (t, J
= 7.8 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ 142.2, 132.7, 128.4,
128.3, 128.2, 125.6, 82.9, 36.1, 34.4, 26.8, 24.8; 11B NMR (CDCl3, 128
MHz) δ 34.1; IR (neat, cm−1) 2980, 2928, 2853, 1372, 1321, 1146,
968, 748; HRMS (FAB, positive) m/z calcd for C17H27BO2 286.2104,
found 286.2115.
1
0.090 mmol, 89% yield (22.5 mg/25.4 mg): colorless oil; H NMR
(CDCl3, 400 MHz) δ 7.55 (m, 2H), 7.31 (m, 2H), 2.80 (t, J = 8.0 Hz,
2H), 1.21 (s, 12H), 1.14 (t, J = 8.0 Hz, 2H); 13C NMR (CDCl3, 100
MHz) δ 161.1 (d, J = 242 Hz), 139.9 (d, J = 3.3 Hz), 129.3 (d, J = 8.2
Hz), 114.8 (d, J = 20.7 Hz), 83.1, 29.1, 24.7; 11B NMR (CDCl3, 128
MHz) δ 34.2; 19F NMR (CDCl3, 470 MHz) δ −117.7; IR (neat,
cm−1) 2979, 2935, 1510, 1372, 1220, 1145, 968, 853, 840; HRMS
(FAB, positive) m/z calcd for C14H20BFO2 250.1540, found 250.1547.
Synthesis of 4,4,5,5-Tetramethyl-2-(3-nitrophenethyl)-1,3,2-
dioxaborolane (5f).26 To a solution of 1 (54 mg, 0.2 mmol, 2
equiv), 4f (21.4 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg, 5.0 μmol,
5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24 μL, 0.2
mmol, 2 equiv) at room temperature. The mixture was stirred for 5 h
and filtered through a pad of silica gel with ether. Concentration gave
the residue, the NMR yield of which was determined to be >98% by
the integration ratio of the crude NMR with 1,1,2,2-tetrachloroethane
as an internal standard. Purification by silica gel column chromatog-
raphy (hexane/EtOAc = 10/1) gave the product 5f in 0.069 mmol,
70% yield (19.2 mg/27.4 mg).
Synthesis of 4-(2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-
yl)ethyl)benzonitrile (5g). To a solution of 1 (54 mg, 0.2 mmol, 2
equiv), 4g (19.6 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg, 5.0 μmol,
5 mol %) in dioxane 1.0 mL was added 8 N KOH aq (24 μL, 0.2
mmol, 2 equiv) at room temperature. The mixture was stirred for 5 h
and filtered through a pad of silica gel with ether. Concentration gave
the residue, the NMR yield of which was determined to be 97% by the
integration ratio of the crude NMR with 1,1,2,2-tetrachloroethane as
an internal standard. Purification by silica gel column chromatography
(hexane/EtOAc = 10/1) gave the product 5g in 0.085 mmol, 85%
yield (21.9 mg/25.7 mg): colorless oil; 1H NMR (CDCl3, 400 MHz) δ
7.55 (m, 2H), 7.31 (m, 2H), 2.80 (t, J = 8.0 Hz, 2H), 1.21 (s, 12H),
1.14 (t, J = 8.0 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ 150.0, 132.0,
128.8, 119.2, 109.4, 83.3, 30.1, 24.8; 11B NMR (CDCl3, 128 MHz) δ
33.9; IR (neat, cm−1) 2974, 2934, 2361, 2338, 1364, 1276, 1217, 965,
767, 749; HRMS (FAB, positive) m/z calcd for C15H21BNO2 [M +
H]+ 258.1665, found 258.1665.
Synthesis of 4,4,5,5-Tetramethyl-2-phenethyl-1,3,2-dioxa-
borolane (5a).24 To a solution of 1 (79 mg, 0.3 mmol, 2 equiv),
4a (25.9 mg, 0.15 mmol), and Pd[P(t-Bu)3]2 (3.8 mg, 7.4 μmol, 5 mol
%) in dioxane (1.5 mL) was added 8 N KOH aq (36 μL, 0.3 mmol, 2
equiv) at room temperature. The mixture was stirred for 2.5 h and
filtered through a pad of silica gel with ether. Concentration gave the
residue, the NMR yield of which was determined to be >98% by the
integration ratio of the crude NMR with 1,1,2,2-tetrachloroethane as
an internal standard. Purification by silica gel column chromatography
(hexane/EtOAc = 20/1) gave the product 5a in 0.137 mmol, 93%
yield (31.8 mg/34.4 mg); the reaction of 1 (2.68 g, 10 mmol, 2 equiv)
and 4a (855 mg, 5 mmol) in the presence of Pd[P(t-Bu)3]2 (128 mg,
0.25 mmol, 5 mol %) and 8 N KOH aq (1.25 mL, 10 mmol, 2 equiv)
in dioxane 50 mL at room temperature for 24 h gave the product 5a in
4.45 mmol, 89% yield (1.03 g/1.16 g).
Synthesis of 4,4,5,5-tetramethyl-2-(4-methylphenethyl)-
1,3,2-dioxaborolane (5b).25 To a solution of 1 (54 mg, 0.2
mmol, 2 equiv), 4b (18.5 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg,
5.0 μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24
μL, 0.2 mmol, 2 equiv) at room temperature. The mixture was stirred
for 5 h and filtered through a pad of silica gel with ether.
Concentration gave the residue, the NMR yield of which was
determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/EtOAc = 10/1) gave the
product 5b in 0.085 mmol, 85% yield (21.2 mg/24.8 mg).
Synthesis of 2-(4-tert-Butylphenethyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (5c). To a solution of 1 (54 mg, 0.2 mmol, 2
equiv), 4c (22.6 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg, 5.0 μmol,
5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24 μL, 0.2
mmol, 2 equiv) at room temperature. The mixture was stirred for 24 h
and filtered through a pad of silica gel with ether. Concentration gave
the residue, the NMR yield of which was determined to be 92% by the
integration ratio of the crude NMR with 1,1,2,2-tetrachloroethane as
an internal standard. Purification by silica gel column chromatography
(hexane/EtOAc = 10/1) gave the product 5c in 0.087 mmol, 89%
yield (25.4 mg/28.5 mg): colorless oil; 1H NMR (CDCl3, 400 MHz) δ
7.22−7.19 (m, 2H), 7.09−7.07 (m, 2H), 2.64 (t, J = 8.0 Hz, 2H), 1.23
(s, 9H), 1.15 (s, 12H), 1.06 (t, J = 8.0 Hz, 2H); 13C NMR (CDCl3,
100 MHz) δ 148.3, 141.4, 127.7, 125.1, 83.1, 34.4, 31.5, 29.5, 24.9; 11B
NMR (CDCl3, 128 MHz) δ 33.6; IR (neat, cm−1) 2977, 2935, 1374,
1321, 1270, 1145, 969, 846, 748; HRMS (FAB, positive) m/z calcd for
C18H29BO2 288.2260, found 288.2267.
Synthesis of 2-(4-Chlorophenethyl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (5d).24 To a solution of 1 (54 mg, 0.2
mmol, 2 equiv), 4d (20.3 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg,
5.0 μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24
μL, 0.2 mmol, 2 equiv) at room temperature. The mixture was stirred
for 5 h and filtered through a pad of silica gel with ether.
Concentration gave the residue, the NMR yield of which was
determined to be >98% by the integration ratio of the crude NMR
with 1,1,2,2-tetrachloroethane as an internal standard. Purification by
silica gel column chromatography (hexane/EtOAc = 10/1) gave the
product 5d in 0.085 mmol, 86% yield (22.7 mg/26.4 mg).
Synthesis of Methyl 4-(2-(4,4,5,5-Tetramethyl-1,3,2-dioxa-
borolan-2-yl)ethyl)benzoate (5h). To a solution of 1 (54 mg, 0.2
mmol, 2 equiv), 4h (22.9 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg,
5.0 μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24
μL, 0.2 mmol, 2 equiv) at room temperature. The mixture was stirred
for 24 h and filtered through a pad of silica gel with ether.
Concentration gave the residue, the NMR yield of which was
determined to be 91% by the integration ratio of the crude NMR with
1,1,2,2-tetrachloroethane as an internal standard. Purification by silica
gel column chromatography (hexane/EtOAc = 10/1) gave the product
1
5h in 0.077 mmol, 77% yield (22.4 mg/29.0 mg): colorless oil; H
NMR (CDCl3, 400 MHz) δ 7.94−7.92 (m, 2H), 7.29−7.26 (m, 2H),
3.89 (s, 3H), 2.80 (t, J = 8.4 Hz, 2H), 1.21 (s, 12H), 1.18−1.13 (m,
2H); 13C NMR (CDCl3, 100 MHz) δ 167.2, 149.9, 129.6, 128.0,
127.5, 83.2, 51.9, 30.0, 24.8; 11B NMR (CDCl3, 128 MHz) δ 34.4; IR
(neat, cm−1) 2979, 2950, 1739, 1373, 1145, 1110, 968,704; HRMS
(FAB, positive) m/z calcd for C16H2410BO4 [M + H]+ 290.1804, found
290.1805.
Synthesis of 4,4,5,5-Tetramethyl-2-(2-(naphthalen-2-yl)-
ethyl)-1,3,2-dioxaborolane (5i).24 To a solution of 1 (54 mg, 0.2
mmol, 2 equiv), 4i (22.1 mg, 0.1 mmol), and Pd[P(t-Bu)3]2 (2.6 mg,
5.0 μmol, 5 mol %) in dioxane (1.0 mL) was added 8 N KOH aq (24
μL, 0.2 mmol, 2 equiv) at room temperature. The mixture was stirred
for 24 h and filtered through a pad of silica gel with ether.
E
dx.doi.org/10.1021/jo3004293 | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Note
Concentration gave the residue, the NMR yield of which was
determined to be 84% by the integration ratio of the crude NMR with
1,1,2,2-tetrachloroethane as an internal standard. Purification by silica
gel column chromatography (hexane/EtOAc = 10/1) gave the product
5i in 0.080 mmol, 80% yield (22.5 mg/28.2 mg).
Synthesis; Trost, B. M., Fleming, I., Pattenden, G., Eds.; Pergamon:
Oxford, 1991; Vol. 3, Chapter 2.2. (c) Magid, R. M. Tetrahedron 1980,
36, 1901. (d) Lipshutz, B. H.; Sengupta, S. Org. React. 1992, 41, 135.
(12) Recent examples of SMC between arylboron compounds and
allyl halide derivatives: (a) Botella, L.; Naj
2002, 663, 46. (b) Singh, R.; Viciu, M. S.; Kramareva, N.; Navarro, O.;
Nolan, S. P. Org. Lett. 2005, 7, 1829. (c) Alacid, E.; Najera, C. Org.
́
era, C. J. Organomet. Chem.
́
ASSOCIATED CONTENT
* Supporting Information
■
Lett. 2008, 10, 5011. (d) Ghosh, R.; Adarsh, N. N.; Sarkar, A. J. Org.
Chem. 2010, 75, 5320. (e) Lipshutz, B. H.; Ghorai, S.; Abela, A. R.;
Moser, R.; Nishikata, T.; Duplais, C.; Krasovskiy, A.; Gaston, R. D.;
Gadwood, R. C. J. Org. Chem. 2011, 76, 4379. Examples of SMC
between allylboron compounds and aryl halide derivatives: (f) Yama-
moto, Y.; Takada, S.; Miyaura, N.; Iyama, T.; Tachikawa, H.
Organometallics 2009, 28, 152. (g) Flegeau, E. F.; Schneider, U.;
Kobayashi, S. Chem.Eur. J. 2009, 15, 12247. (h) Glasspoole, B. W.;
Ghozati, K.; Moir, J. W.; Crudden, C. M. Chem. Commun. 2012, 48,
1230.
S
NMR spectra of products. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: kendo@se.kanazawa-u.ac.jp, tshibata@waseda.jp.
■
Notes
(13) Allyl−allyl coupling of an allylboronate and allyl halides:
(a) Zhang, P.; Brozek, L. A.; Morken, J. P. J. Am. Chem. Soc. 2010, 132,
10686. (b) Zhang, P.; Le, H.; Kyne, R. E.; Morken, J. P. J. Am. Chem.
Soc. 2011, 133, 9716. (c) Brozek, L. A.; Ardolino, M. J.; Morken, J. P. J.
Am. Chem. Soc. 2011, 133, 16778.
(14) He, A.; Falck, J. R. J. Am. Chem. Soc. 2010, 132, 2524.
(15) Nishikata, T.; Lipshutz, B. H. J. Am. Chem. Soc. 2009, 131,
12103.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the JST PRESTO program, Grant-
in-Aid for Young Scientists (B), from the Japan Society for the
Promotion of Science and a Waseda University Grant for
Special Research Project.
(16) The generation of a stable σ-allylpalladium complex bearing a
NHC ligand at room temperature was reported: Egbert, J. D.;
Chartoire, A.; Slawin, A. M. Z.; Nolan, S. P. Organometallics 2011, 30,
4494.
(17) The reaction of 1,1-diborylalkanes and (E)-cinnamyl bromide
(2a) did not proceed.
(18) The reaction of 3-bromo-1-propene did not proceed.
(19) Heteroaromatic coupling partners could not be compatible with
the reaction conditions; the desired products were obtained in less
than 10% yield.
(20) Li, C.; Xing, J.; Zhao, J.; Huynh, P.; Zhang, W.; Jiang, P.; Zhang,
Y. J. Org. Lett. 2012, 14, 390.
(21) (a) Kuwano, R. Synthesis 2009, 1049. (b) Legros, J.-Y.; Fiaud, J.-
C. Tetrahedron Lett. 1992, 33, 2509. (c) Kuwano, R.; Kondo, Y.;
Matsuyama, Y. J. Am. Chem. Soc. 2003, 125, 12104.
(22) The reaction of 1,1-diborylalkanes and benzyl bromide (4a) did
not proceed.
(23) The reaction of secondary alkyl halides, such as (1-bromoethyl)
benzene, did not give the desired product at all. Furthermore, the
reaction of aliphatic halides, such as (3-bromopropyl)benzene, did not
proceed.
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dx.doi.org/10.1021/jo3004293 | J. Org. Chem. XXXX, XXX, XXX−XXX