PSiP-pincer type palladium-catalyzed dehydrogenative borylation of alkenes and 1,3-Dienes

Article abstract of DOI:10.1246/bcsj.20130004

Dehydrogenative borylation of alkenes and 1,3-dienes was realized by carrying out the reaction in the presence of bis(pinacolato)diboron (B2pin2) and a catalytic amount of PSiP-pincer palladium complex. This protocol has the following notable features. 1)

Full text of DOI:10.1246/bcsj.20130004

784
Bull. Chem. Soc. Jpn. Vol. 86, No. 7, 784-799 (2013)
© 2013 The Chemical Society of Japan
BCSJ Award Article
PSiP-Pincer Type Palladium-Catalyzed Dehydrogenative
Borylation of Alkenes and 1,3-Dienes
Naohiro Kirai,1,2 Shoichiro Iguchi,1,2 Tatsuyoshi Ito,1,2 Jun Takaya,1,2 and Nobuharu Iwasawa*1,2
1Department of Chemistry, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551
2CREST-JST, O-okayama, Meguro-ku, Tokyo 152-8551
Received January 5, 2013; E-mail: niwasawa@chem.titech.ac.jp
Dehydrogenative borylation of alkenes and 1,3-dienes was realized by carrying out the reaction in the presence
of bis(pinacolato)diboron (B2pin2) and a catalytic amount of PSiP-pincer palladium complex. This protocol has the
following notable features. 1) Monoanionic nature of the PSiP-pincer ligand prevents the formation of boryl(hydrido)- or
dihydridopalladium species, enabling synthesis of various vinyl- or dienylboronic esters in good yield from a 1:1 mixture
of B2pin2 and alkenes or 1,3-dienes without forming hydroboration or hydrogenation products. 2) Due to the strong
trans influence of the silicon atom, PSiP-pincer palladium complex showed high activity toward migratory insertion.
3) Suppression of these side-reactions and the high reactivity of the PSiP-pincer palladium complex enabled an efficient,
successive dehydrogenative borylation to give 1,1- or 1,2-diborylated products depending on the kind of substituent on
alkenes by using more than 2 equivalents of B2pin2. Mechanistic study revealed that PSiP-pincer borylpalladium complex
was generated from hydridopalladium complex and B2pin2, and this complex underwent alkene insertion followed by ¢-
hydride elimination to give alkenylboronic ester with regeneration of the hydridopalladium complex.
Alkenyl boronic esters are an important class of compounds,
the utility of dehydrogenative borylation, development of a
novel catalytic system which excludes the generation of boryl-
(hydrido)- or dihydrido complexes and shows high reactivity
is highly desirable. Recently, NCN-pincer palladium-catalyzed
dehydrogenative borylation was reported by Szabó et al.15 This
system involved a Pd(II)-Pd(IV) cycle which excluded the
generation of boryl(hydrido)- or dihydrido complex, affording
alkenylboronic esters without concomitant formation of hydro-
boration or hydrogenation products. However, this reaction still
necessitated the use of an excess amount of alkenes along with
two molar equivalents of PhI(OAc)2 as oxidant.
We previously reported the synthesis of PSiP-pincer type
palladium complex for the catalytic hydrocarboxylation reac-
tion of allenes and 1,3-dienes.16 We envisioned that PSiP-pincer
ligand would prevent the formation of boryl(hydrido)- or
dihydridopalladium species, because monoanionic character of
the PSiP-pincer ligand permits the palladium(II) center to bind
only one additional anionic ligand (Figure 1). Furthermore, the
strong trans influence of the silicon atom would enhance the
reactivity of the palladium complex toward migratory insertion.
We expected that these features would enable development of a
novel and efficient dehydrogenative borylation of alkenes. In
this paper, we report detailed study of PSiP-pincer type palla-
dium complex catalyzed dehydrogenative borylation, which
allows synthesis of mono- and diborylalkenes or 1,3-dienes
without accompanying hydroboration or hydrogenation.17
which have been widely employed in the synthesis of natural
products, functional molecules, and functional polymers as a
component of metal-catalyzed cross-coupling reactions.1 There
have been reported various methods for the preparation of
alkenylboronic esters, such as alkenylation of trialkylborate
with alkenyllithium or magnesium reagents, Ishiyama-Miyaura
borylation of alkenyl halides with diboron2 or borane,3 and
hydroboration of alkynes.4 However, these methods need pre-
functionalization of the alkenyl group or are unsuitable for
the synthesis of ¢,¢-disubstituted or cyclic alkenylboronic
esters. Transition-metal-catalyzed dehydrogenative borylation
of alkenes is an alternative straightforward method for the syn-
thesis of alkenylboronic esters, which could formally convert
alkene C-H bonds to C-B bonds directly.5 The reaction does
not require the preparation of alkenyl halides and is expected
to be applicable to the synthesis of ¢,¢-disubstituted or cyclic
alkenylboronic esters. However, previously reported reactions
catalyzed by Rh(I),6 Ir(I),7 Ru(III),8 Pd(II),9 Pt(II),10 or Ti(IV)11
have several disadvantages; the reaction is often accompanied
by hydrogenation and/or hydroboration of alkenes caused by
boryl(hydrido)- or dihydrido complex intermediates, and thus
an excess amount of alkenes is usually required.12-14 Addition-
ally, substrate scope of alkenes was rather poor in many of
these reactions, and it is common that the reaction proceeded
smoothly only with styrene derivatives. Therefore, to expand
Published on the web April 20, 2013; doi:10.1246/bcsj.20130004

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
785
1, B2pin2, and AlEt3 via formation of hydridopalladium 4.
Following insertion of alkene 5 to borylpalladium 2, followed
by ¢-hydride elimination would produce alkenylboronic ester
6 with regeneration of hydridopalladium 4. This hydridopalla-
dium 4 would react again with diboron to regenerate boryl-
palladium 2. Importantly, this proposed catalytic cycle does
not include boryl(hydrido)- or dihydridopalladium species, thus
should prevent the formation of undesirable hydroboration or
hydrogenation products.
Results and Discussion
Preparation of PSiP-Pincer Borylpalladium Complex.
First, we examined the synthesis of PSiP-pincer borylpalladium
complex, which was expected to be an active species of
dehydrogenative borylation. We selected palladium triflate 1a
bearing Ph groups on phosphorus as a palladium complex and
bis(pinacolato)diboron (B2pin2) or pinacolborane (HBpin) as
a boron source. When palladium triflate 1a was mixed with
B2pin2 or HBpin in benzene-d6, no formation of a new complex
was observed by 31P NMR spectra. However, after several
attempts, it was found that the addition of 2 molar equivalents
of AlEt3, which was employed as a reductant in the hydro-
carboxylation reaction, to a mixture of palladium triflate 1a
and 20 molar equivalents of B2pin2 afforded the desired boryl-
palladium complex 2a in 62% yield (Scheme 1). A similar
reaction of palladium triflate 1a and AlEt3 using HBpin instead
of B2pin2 did not generate the complex 2a.
Unfortunately, our attempt to isolate complex 2a was unsuc-
cessful due to decomposition during the process of removing
solvent in the presence of aluminum reagent. After examina-
tion of other reductants, we found that addition of n-BuLi also
generated the same complex 2a cleanly, and isolation of boryl-
palladium complex 2a was successfully achieved in 84% yield
by the reaction of palladium chloride 3a, B2pin2, and n-BuLi
in a ratio of 1:4:2.4. The structure of 2a was confirmed as the
PSiP-pincer borylpalladium by X-ray analysis (Figure 2). Due
to the strong trans influence of the silicon atom,18 the Pd-B bond
length elongated to 2.12 ¡, which is the longest among the
borylpalladium complexes ever reported.19 Thus, high reactivity
of this borylpalladium toward alkene insertion was expected.
Although the exact mechanism of the generation of boryl-
palladium 2a is not clear, it is thought to be generated by the
reaction of hydridopalladium and B2pin2, and hydridopalla-
dium could be generated by transmetalation of palladium
triflate with AlEt3 followed by ¢-hydride elimination.16a,16c
From these results, we expected that PSiP-pincer palladium-
catalyzed dehydrogenative borylation would become possible
according to the following successive reactions (Scheme 2).
At first, borylpalladium 2 is generated from palladium triflate
Optimization of Reaction Conditions. At first, styrene
5a and B2pin2 were selected as substrates for optimization of
the catalytic dehydrogenative borylation. As expected, when
2 mol % each of PSiP-pincer palladium triflate 1a bearing
phenyl groups on phosphorus and AlEt3 was used as catalyst,
dehydrogenative borylation proceeded regio- and stereoselec-
tively to afford desired (E)-styrylboronic ester 3a in 24% yield
after 6 h at 60 °C (Table 1, Entry 1). Notably, neither hydro-
boration nor hydrogenation products were observed in the
crude reaction mixture. Addition of AlEt3 was essential and no
formation of the product was observed when palladium triflate
1a was used alone (Entry 2). Employment of pinacolborane did
not afford 3a (Entry 3). Then, we examined other PSiP-pincer
Pd complexes to improve catalytic activity of the reaction.
When the reaction was carried out in the presence of palladium
triflate 1b bearing p-anisyl groups on phosphorus, the yield
of 3a was decreased (Entry 4). Sterically demanding o-tolyl-
substituted complex 1c did not show any catalytic activity
(Entry 5). 2-Furyl-substituted complex 1d did not show high
activity either, but palladium complex 1e bearing 4-CF3C6H4
groups on phosphorus improved the yield dramatically (Entries
6 and 7). Furthermore, it was found that 3,5-(CF3)2C6H3-
substituted complex 1f was quite efficient for this reaction and
3a was obtained in high yield as a single stereoisomer even
at room temperature.
X
no formation of
H
Pd
Ar2P
PAr2
H
H
or
Ln Pd
Ln Pd
Si
Bpin
Me
X = H or Bpin
Figure 2. ORTEP plot of borylpalladium 2a. Hydrogen
atoms are omitted for clarity.
Figure 1. PSiP-pincer palladium complex.
OTf
Bpin
20 equiv B2pin2
2.0 equiv AlEt3
Pd
Ph2P
PPh2
Pd
Ph2P
PPh2
Si
Si
benzene-d6
rt, 2 h
Me
Me
2a; 62% (NMR yield)
Scheme 1. Generation of borylpalladium 2a.
1a

786
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
Bpin
Pd
OTf
Pd
H
AlEt3
Ar2P
PAr2
Pd
Ar2P
PAr2
Ar2P
PAr2
Si
Me
2
Si
Si
Me
4
AlEt2OTf
+
B2pin2
HBpin
Me
1
R
Bpin
Ar2P
Pd
Si
PAr2
Me
Bpin
R
R
6
5
Scheme 2. Strategy for PSiP-pincer palladium-catalyzed dehydrogenative borylation.
Table 1. Optimization of Reaction Conditions
(PSiP)PdOTf =
2 mol% AlEt3
OTf
2 mol% (PSiP)PdOTf
Bpin
+
B2pin2
Pd
Ar2P
PAr2
Ph
Ph
toluene
60 °C, 6 h or rt, 24 h
(1.0 equiv)
Si
Me
1
5a
6a
(PSiP)PdOTf
(Ar on Phosphorus atom)
Entry
Reductant
Boron source
Temp/°C
Yielda)/%
1
2
3
4
5
6
7
8
9
1a (Ph)
1a (Ph)
1a (Ph)
1b (4-MeOC6H4)
1c (2-MeC6H4)
1d (2-furyl)
1e (4-CF3C6H4)
1f (3,5-(CF3)2C6H3)
1f (3,5-(CF3)2C6H3)
AlEt3
none
B2pin2
B2pin2
HBpin
B2pin2
B2pin2
B2pin2
B2pin2
B2pin2
B2pin2
60
60
60
60
60
60
60
60
rt
24
0
0
7
0
12b)
AlEt3
AlEt3
AlEt3
AlEt3
AlEt3
AlEt3
AlEt3
quant.
quant.
quant. (92c))
a) NMR yield. b) (PSiP)PdCl was used. c) Isolated yield.
This higher catalytic activity of 3,5-(CF3)2C6H3-substituted
ence of a catalytic amount of palladium triflate 1f and AlEt3
(Table 2). ¡- or ¢-Substituted styrenes 5b-5d were applicable
to this reaction and corresponding alkenylboronic esters were
stereoselectively obtained in high yields even with 1 mol %
catalyst loading at room temperature (Table 2, Entries 1-3).
Importantly, 1,1-disubstituted alkenyl boronic ester 6b, which
cannot be synthesized by hydroboration of alkyne, was easily
available by this method. Similarly, vinylferrocene (5e) could
be employed although it required 5 mol % of 1f and heating
(Entry 4). Moreover, this selective synthesis of monoboryl-
alkenes was also applicable to other simple terminal alkenes.
The reaction of allylcyclopentane (5f) or 2-methyl-4-phenyl-1-
butene (5g) afforded alkenylboronates 6f or 6g in good yields
(Entries 5 and 6). This reaction was applicable to 1-octene (5h),
a simple straight chain alkene, although use of 3 equivalents of
alkene was necessary due to partial isomerization of the double
bond of the starting material (Entry 7). We also examined
the reaction of simple internal alkenes such as (E)- and (Z)-4-
octene, however, the reaction did not give the desired alkenyl-
complex 1f was explicitly shown in the stoichiometric reac-
tion of borylpalladium 2a or 2f and ¢-methylstyrene (5d)
(Scheme 3). Borylpalladium 2f was prepared in situ from the
reaction of palladium chloride 3f, 10 equivalents of B2pin2
and n-BuLi, because isolation of 2f was unsuccessful due to
its high solubility. While borylpalladium 2a did not react with
¢-methylstyrene (5d) at room temperature, borylpalladium
2f bearing 3,5-(CF3)2C6H3 moiety immediately reacted with
¢-methylstyrene (5d) at room temperature to give 6d quan-
titatively as a single geometric isomer. Thus, by decreasing
electron-donating ability of phosphorus atoms, migratory inser-
tion was facilitated, leading to high catalytic activity. It should
be noted that from (E)-¢-methylstyrene (5d), (Z)-alkenyl-
boronic ester 6d was obtained selectively, suggesting that the
reaction proceeded via syn-borylpalladation, followed by syn-
¢-hydride elimination.
Scope and Limitation. Then, substrate scope of alkenes
was examined by using 1 equivalent of B2pin2 in the pres-

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
787
Bpin
Pd
Bpin
Ar2P
PAr2
+
Si
benzene-d6
rt, 1 h
Me
5d
6d
2a (Ar = Ph)
or
2f (Ar = 3,5-(CF3)C6H3)
(prepared in situ)
(1.0 equiv)
with 2a ; No reaction
with 2f ; quant.
Scheme 3. Reaction of borylpalladium with (E)-¢-methylstyrene.
Table 2. Dehydrogenative Borylation of Alkenes
OTf
Pd
x mol% AlEt3
x mol% (PSiP)PdOTf 1f
Ar2P
PAr2
R1
Si
Alkene
+
B2pin2
Bpin
R2
toluene
rt, 24 h or 60 °C, 6 h
(1.0 equiv)
Me
R3
1f
(Ar = 3,5-(CF3)2C6H3)
Entry
Substrates
x
Temp/°C
Product
Yield/%
E:Z
Bpin
Bpin
1
2
3
1
rt
87
quant.
89
E only
Ph
Ph
5b
Ph
6b
Ph
1
1
rt
rt
®
Ph
Ph
5c
6c
Ph
Ph
Z only
Bpin
5d
6d
Fe
Fe
Bpin
4
5
5
60
60
93
E only
E only
5e
6e
10
43a)
Bpin
5f
6f
Ph
Ph
6
7
8
5
5
5
rt
82
37:63
93:7
Bpin
Bpin
5g
6g
n-C6H13
n-C6H13
60
60
87b),c)
5h
6h
Bpin
98
Z only
5i
6i
Me3Si
Me3Si
Bpin
Bpin
9
10
11
1
1
60
60
60
58d)
84e)
88f)
87:13
75:25
E only
5j
Ph3Si
5k
6j
Ph3Si
Ph3Si
6k
Bpin
Ph3Si
5l
10
6l
TBSO
TBSO
Ph
62a)
88:12
Bpin
12
10
60
Ph
5m
6m
Continued on next page:

788
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
Continued:
Entry
Substrates
x
Temp/°C
Product
Yield/%
E:Z
Bpin
Cl
Cl
13
10
60
53a)
92:8
5n
NC
5o
6n
Bpin
NC
O
14
15
16
5
5
5
60
60
60
64f),g)
87g)
70
62:38
86:14
56:44
6o
O
O
O
O
O
Bpin
5p
6p
6q
PhO2S
5q
O
PhO2S
Bpin
O
Bpin
N
N
17
10
60
91
E only
O
O
5r
6r
a) 3-15% of diborylation product was obtained. b) 3 equivalents of 1-octene were used. c) The reaction
was carried out in THF. d) Obtained as a mixture with 13% of 9j. e) (Z)-Isomer was obtained as a mixture
with a small amount of 1-propenyltriphenylsilane and some isomers. f) 2 equivalents of B2pin2 were used.
g) NMR yield.
β-Hydride
elimination
H
H
Bpin
Bpin
H
+ (PSiP)PdH
Pd(PSiP)
H
H
H
H
Allylboronic ester
β-Hydride
elimination
H
Bpin
Insertion
H
+ (PSiP)PdH
H
H
H
Bpin
Pd(PSiP)
Alkenylboronic ester
Scheme 4. Proposed mechanism of the generation of cycloheptenylboronic ester 6i.
boronic esters in good yield.20 This is a limitation of this
protocol, however, selective synthesis of the above alkenyl-
boronic ester 6h was achieved successfully, because isomerized
internal alkene did not react to afford internal alkenylboronic
esters. Cycloheptenylboronic ester 6i, which could not be
synthesized by hydroboration of alkyne, was obtained in good
yield (Entry 8).
Then functional group compatibility of this reaction
was examined next. Synthesis of functionalized boryl alkenes
was hardly examined in previously reported dehydrogenative
borylation reactions. Allyl- or vinylsilanes 5j, 5k, and 5l were
allowed to react with B2pin2, affording bifunctional compounds
6j, 6k, and 6l, which could be utilized for further reactions
of organoboron and silicon compounds (Entries 9-11). Alkenyl
boronic esters 6m-6p which contained silyl ether, chloro,
cyano, and acid anhydride groups were obtained in reasonable
yield without loss of these functional groups, although forma-
tion of a small amount of diborylated products was observed
in some cases (Entries 12-15). Sulfone or imide functionality
was also compatible under these reaction conditions (Entries 16
and 17).
In most cases, sterically less hindered (E)-alkenylboronic
esters were obtained in good to high selectivity. This selec-
tivity was thought to be realized at the stage of the ¢-hydride
elimination from the alkylpalladium intermediate through the
less sterically congested conformer, but in some case, there
seems to be an equilibrium between (E)- and (Z)-alkenylboronic
esters through a hydropalladation/¢-hydride elimination se-
quence. Actually, we believe that cycloheptenylboronic ester 6i
was obtained through isomerization of initially produced
allylboronic ester via hydropalladation followed by ¢-hydride
elimination (Scheme 4). A similar mechanism was proposed in
Rh-catalyzed dehydrogenative borylation of cyclic alkenes.6g
Next, we focused on the application of the current catalytic
system toward the preparation of dienylboronic esters. Al-
though dienyl boronic esters are a useful building block for
synthesis of natural products and ³-conjugated molecules,21
only one example was reported for dehydrogenative borylation

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
789
Table 3. Dehydrogenative Borylation of 1,3-Diene
OTf
x mol% 1f or 1g
R2 R4
R2 R4
Pd
Ar2P
PAr2
x mol% AlEt3
+
B2pin2
Bpin
Si
R1
R1
toluene, 60 °C, 6 h
R3
R3
Me
R
R
y equiv
R = H; 1f, R = CF3; 1g
Ar = 3,5-(CF3)2C6H3
Entry
Substrates
x (1f or 1g)
2.5 (1g)
y
Product
Yield/%
E/Z
Bpin
Ph
Ph
8a
Ph
1
2
2
80
58:42
7a (E only)
Ph
Bpin
Bpin
2.5 (1f)
2.5 (1f)
2.5 (1f)
1
1
1
98
87:13
86:14
74:26
Ph
Ph
7b
Me
8b
Me
3
4
5
98b)
93b)
Ph
3
Ph
1
3
7c (E:Z = 8:2)
8c
Me
Me
Bpin
Ph
Ph
Ph
1
7d (E:Z = 7:3)
Ph
8d
Bpin
2.5 (1f)
1
91
85:15
7e
8e
Ph
Ph
Bpin
Bpin
Ph
Me
7f
Ph
Ph
6
7
2.5 (1f)
2.5 (1g)
2
2
90
®
Me
8f
46a)
62:38
Ph
7g
8g
a) The reaction was carried out in THF. b) Contained ca. 5% of isomers (1Z, 3E/Z)-8.
of 1,3-dienes using silylborane with Ni catalyst.22 In this reac-
tion, hydrosilylation of 1,3-diene also proceeded, and 2 molar
equivalents of 1,3-diene were needed to obtain dienylboronic
ester in good yield.
substituted diene 7a was low, but in contrast, the reaction of
1,1,2-trisubstituted diene 7f gave 8f as a single isomer probably
due to steric repulsion between the Me group and boryl group.
As summarized above, this protocol showed high activity
and wide generality for dehydrogenative borylation, suppress-
ing the hydroboration and hydrogenation completely. In most
cases, monoborylalkenes were obtained from a 1:1 mixture
of substrate and B2pin2. These notable features prompted us to
examine the successive dehydrogenative borylation by using
2 equivalents of B2pin2. We expected that dehydrogenative
borylation of monoborylalkenes would proceed to give 1,1-23
or 1,2-diborylalkenes8c,15,24 depending on the regioselectivity
of the second borylation (Scheme 5). Such diborylalkenes
are useful building blocks for the synthesis of ³-conjugated
material because two boryl groups could be utilized for suc-
cessive cross-coupling reaction to afford various trisubstituted
alkenes.25 It should be noted that most reported dehydrogen-
ative borylations necessitate the use of excess amounts of
alkenes due to accompanying hydroboration or hydrogenation,
which renders realization of successive dehydrogenative
borylations difficult. Only one report describes the synthesis
of diborylalkenes by a Rh-catalyzed successive reaction, in
which only two examples were reported.12b
Unfortunately, the reaction of 1-phenyl-1,3-butadiene (7a)
in the presence of 2.5 mol % palladium triflate 1f and AlEt3
afforded 4-phenylbutadienylboronic ester 8a only in 11% yield
even when 2 equivalents of B2pin2 were used. However we
have succeeded in improving the yield by introducing CF3 to
the phenylene backbone of the pincer palladium complex.
When 2.5 mol % of newly synthesized PSiP-pincer palladium
triflate 1g was used, dienylboronic ester 8a was obtained
in 80% yield (Table 3, Entry 1). Neither hydroboration- nor
hydrogenation product was detected in the reaction mixture.
Similarly, the reaction of 1,1-disubstituted dienes 7b-7e also
underwent dehydrogenative borylation, affording the corre-
sponding dienyl boronic esters 8b-8e in high yield by using
palladium triflate 1f or 1g and 1 equivalent of B2pin2 (Entries
2-5). 1,1,2- or 1,3-substituted dienes 7f and 7g were also appli-
cable for this reaction to give corresponding boronic esters
in moderate to good yields. The geometry of the obtained
dienylboronic esters was thought to be dependent on the steric
environment. The stereoselectivity of the reaction of mono-

790
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
Bpin
Bpin
R
cat. (PSiP)Pd
1 equiv B2pin2
1,1-diborylalkene
1 equiv B2pin2
Bpin
or
R
R
Bpin
R
Bpin
1,2-diborylalkene
Scheme 5. Successive dehydrogenative borylation.
2 mol% AlEt3
2 mol% 1f
Bpin
Bpin
9a; 90%
Ph
+
B2pin2
Ph
toluene
(2.0 equiv)
rt, 24 h
5a
Scheme 6. Successive dehydrogenative borylation of styrene 5a.
5 mol% AlEt3
Bpin
5 mol% 1g
Ph3Si
Ph3Si
+
B2pin2
toluene
60 °C, 6 h
(2.0 equiv)
Bpin
9k; 90%
(Z only)
5k
Scheme 7. Successive dehydrogenative borylation of triphenylallylsilane (5k).
located trans) was obtained mainly from (E)-monoborylalkene
through syn-borylpalladation followed by syn-¢-hydride elim-
ination, and the remaining less reactive (Z)-monoborylalkene
would have isomerized to (E)-monoborylalkene during the
course of the reaction through a hydropalladation/¢-hydride
elimination sequence as described before, although the possi-
bility of isomerization of 1,2-diborylated alkene product cannot
be ruled out (Scheme 8).26 Then we examined the substrate
scope and the regioselectivity of successive dehydrogenative
borylation reaction.
As a result, it was found that the reaction of terminal alkenes
bearing a bulky substituent or a conjugated substituent such
as an aryl and alkenyl group afforded 1,1-diborylated products
selectively (Table 4). The reaction of vinylferrocene (5e) and
N-vinylphthalimide (5r) gave 1,1-diborylalkenes 9e and 9r in
high yield by using palladium complex 1g (Table 4, Entries 1
and 2). While our attempt to synthesize diborylalkenes from
other styrenes such as ¡-methylstyrene (5b) or ¢-methylstyrene
(5d) was not successful, a 1:2 mixture of 1,1-disubstituted
dienes 7b-7e and B2pin2 also gave 1,1-diboryldienes 10b-10e
in high yield in the presence of 2.5 mol % of palladium triflate
1a or 1g and AlEt3 (Table 3, Entries 3-6). These are the first
diboryldiene synthesis by dehydrogenative borylation.27 Al-
though the reason is not obvious, diboryldiene synthesis from
monosubstituted diene 7a, 1,1,2- or 1,3-substituted diene 7f
or 7g was not successful and monoboryldienes were obtained
in these cases.
Figure 3. ORTEP plot of 9k. Hydrogen atoms are omitted
for clarity.
We then examined whether such successive dehydrogenative
borylation was possible or not by using our protocol. When
styrene 5a and 2 equivalents of B2pin2 were treated with
2 mol % of palladium triflate 1f and AlEt3, the desired 1,1-
diborylstyrene 9a was obtained in high yield (Scheme 6). Inter-
estingly, when triphenylallylsilane (5k) was employed under
similar conditions, (Z)-1,2-diboryl alkene 9k, the opposite
regioisomer for the reaction of styrene, was obtained selec-
tively (Scheme 7). Regio- and stereochemistry of compound
9k was confirmed by X-ray analysis (Figure 3). As shown in
Table 2, the intermediate monoborylalkene 6k was obtained as
a mixture of stereoisomers with E:Z = 75:25. We believe that
(Z)-9k (trans-1,2-diborylated alkene in which two boryl groups
In contrast to these results, the reaction of sterically less
demanding, unconjugated terminal alkenes such as allylcyclo-

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
791
Bpin
R
Bpin
R
Bpin
H
H
H
Pd(PSiP)
Bpin
Bpin
R
R
Pd(PSiP)
Bpin
(PSiP)PdBpin
(PSiP)PdBpin
Bpin
H
(PSiP)PdH
trans-1,2-diborylalkene
Bpin
R
Bpin
R
Bpin
Bpin
R
H
H
Bpin
Pd(PSiP)
Pd(PSiP)
H
R
Bpin
H
Bpin
Scheme 8. Proposed mechanism of the generation of (E)-1,2-diborylalkene 9k.
Table 4. Dehydrogenative 1,1-Diborylation
cis-1,2-diborylalkene
OTf
Pd
x mol% 1f or 1g
x mol% AlEt3
Ar2P
PAr2
Bpin
Bpin
+
B2pin2
R
R
Si
toluene, 60 °C, 6 h
2.0 equiv
Me
R
R
R = H; 1f, R = CF3; 1g
Ar = 3,5-(CF3)2C6H3
Entry
1
Substrates
x (1f or 1g)
5 (1g)
Product
Yield/%
E:Z
di:monob)
½50:1
Bpin
Fe
Fe
Bpin
92
®
5e
O
9e
O
Bpin
Bpin
N
N
2
3
5 (1g)
94a)
98
®
®
½50:1
½50:1
O
O
5r
Ph
9r
Ph
Bpin
Ph
Ph
Ph
2.5 (1f)
7b
10bBpin
Me
Me
Bpin
Ph
4
5
6
2.5 (1f)
2.5 (1g)
2.5 (1g)
93
95
89
®
73:27
®
½50:1
½50:1
½50:1
7c (E:Z = 8:2)
10c Bpin
Me
Me
Bpin
Bpin
Ph
Ph
Ph
7d (E:Z = 7:3)
10d
Ph
Bpin
Bpin
7e
10e
a) 3.0 equivalents of B2pin2 were used. b) The ratio of diborylalkene and monoborylalkene was determined
by crude NMR spectrum.
pentane (5f) and 1-octene (5h) gave 1,2-diborylalkenes with
good trans selectivity (Table 5, Entries 1 and 2). This reaction
also showed good compatibility of functional groups, and
functionalized (Z)-1,2-diborylalkenes 9j-9p (trans-1,2-diboryl)
were obtained in moderate to good yield under appropriate
conditions, suggesting our protocol is applicable to the syn-
thesis of multifunctionalized compounds (Entries 3-6). These
results clearly demonstrated that 1,2-selectivity was general for
the reaction of electronically nonactivated alkenes. It should be
noted that, in previously reported Rh-catalyzed successive
dehydrogenative borylation, the reaction of 1-octene gave 1,1-
diborylalkene and Pt-catalyzed diborylation of alkynes afford-
ed cis-1,2-diborylalkenes.28 Our protocol is the first general
method for the synthesis of trans-1,2-diborylalkenes by suc-
cessive dehydrogenative borylation. Moreover, the current
protocol allowed the synthesis of 1,2-diborylcyclooctene 9s
which could not be synthesized by Pt-catalyzed diborylation
of alkyne (Scheme 9). This compound was also thought to be
generated by double bond migration as discussed in the mono-
borylation of cycloheptene (5i). However, successive dehydro-

792
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
Table 5. Dehydrogenative 1,2-Diborylation
OTf
Pd
Ar2P
PAr2
x mol% AlEt3
x mol% 1f or 1g
Bpin
Si
+
B2pin2
R
R
toluene, 60 °C, 6 h
Me
R
R
(2.0 equiv)
Bpin
R = H; 1f, R = CF3; 1g
Ar = 3,5-(CF3)2C6H3
Entry
1
Substrates
x (1f or 1g)
Product
Yield/%
E:Z
di:monoc)
½50:1
Bpin
10 (1f)
10 (1f)
85a)
22:78
Bpin
Bpin
5f
9f
n-C6H13
2
3
63a),b)
19:81
4:96
½50:1
½50:1
n-C6H13
Bpin
5h
9h
Bpin
Me3Si
Me3Si
1 (1g)
82
Bpin
Bpin
5j
9j
TBSO
Ph
TBSO
Ph
4
5
10 (1f)
10 (1f)
68
49
11:89
11:89
½50:1
½50:1
Bpin
5m
9m
Bpin
Cl
Cl
5n
Bpin
9n
O
O
O
O
Bpin
O
O
6
10 (1f)
52
Z only
½50:1
Bpin
5p
9p
a) 3.0 equiv of B2pin2. b) The reaction was carried out in THF. c) The ratio of diborylalkene and
monoborylalkene was determined by crude NMR spectrum.
5 mol% AlEt3
5 mol% 1f
Bpin
Bpin
Bpin
+
B2pin2
+
toluene, 60 °C, 6 h
(2.0 equiv)
9s; 69%
(Z only)
6s; 30%
(Z only)
5s
Scheme 9. Successive dehydrogenative borylation of cyclooctene (5s).
genative borylation of cyclic alkenes showed poor generality,
and the reaction of cycloheptene (5i) or cyclopentene gave
several compounds including allylboronic esters probably due
to isomerization of double bonds. Cyclohexene did not react at
all although the reason was not obvious.
lytic cycle excludes formation of boryl(hydrido)- or dihydrido
complex, thus selective synthesis of alkenyl- or dienylboronic
ester could be realized.
Conclusion
A proposed mechanism of this reaction is summarized
in Scheme 10. At first, the palladium triflate complex 1 reacts
with AlEt3 in the presence of B2pin2 to give the mono-
borylpalladium complex 2 and HBpin. The borylpalladium 2
undergoes alkene insertion and ¢-hydride elimination to give
the monoborylation product with generation of the palladium
hydride 4, which reacts with B2pin2 to regenerate the boryl-
palladium 2. Second, borylation in the presence of excess
B2pin2 gives the diborylation product with high regioselectivity
depending on the substituent on the terminal alkenes. This cata-
In summary, we successfully developed PSiP-pincer
type palladium-catalyzed dehydrogenative borylation. Various
alkenes and 1,3-dienes are applicable to this reaction and
synthetically useful mono- and diborylalkenes or dienes are
obtained selectively without hydroboration or hydrogenation.
Experimental
General. All operations except workup and purification
1
were performed under an argon atmosphere. H and 13C NMR
spectra were recorded on a Bruker DRX-500 (500 MHz for

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
793
Bpin
R
R
[Pd]
Bpin
R
Bpin
H
HBpin
Pd
Si
Pd
Si
Ar2P
PAr2
Ar2P
PAr2
B2pin2
Me
Me
2
4
Bpin
Bpin
R
[Pd]
[Pd]
Bpin
pinB
Bpin
or
H
R
R
Bpin
R
H
or
Bpin
Bpin
(R = Ar, vinyl, imide)
(R = CH2X)
R
Bpin
Scheme 10. Proposed mechanism of PSiP-pincer palladium-catalyzed dehydrogenative borylation.
1H, 125 MHz for 13C) spectrometer, a JEOL ECX-500 (500
for 24 h at room temperature or for 6 h at 60 °C. After the
solvent was removed under reduced pressure (Caution! The
reaction affords pinacolborane as a by-product, which pro-
duces hydrogen gas by reacting with water. This manipulation
should be conducted carefully in a well-ventilated hood.),
the resulting crude product was purified by silica gel column
chromatography (hexanes/AcOEt) to give alkenylboronic ester
6 (43%-93% yield). In most cases, column chromatography
was carried out at low temperature by using a column fitted
with an outer jacket (the column temperature was maintained
below ca. ¹40 °C by filling dry ice/acetone in the outer jacket)
since some alkenylboronic esters were unstable to protodebo-
ration on the silica gel.
1
MHz for H, 125 MHz for 13C), a JEOL ECX-400 (400 MHz
1
for H, 100 MHz for 13C), a JEOL Lambda-400 (400 MHz for
H1 and 100 MHz for 13C), a JEOL AL-400 (400 MHz for H1
and 100 MHz for 13C) or a JEOL AL-300 (300 MHz for H1 and
75 MHz for 13C) spectrometer in CDCl3 (99.8% atom enriched,
Acros Co., Ltd.). Chemical shifts are expressed in parts per
million (ppm) downfield from tetramethylsilane and are refer-
enced to residual solvents (dH 7.26 and dC 77.0). IR spectra
were recorded on an FT/IR-460 plus (JASCO Co., Ltd.). Silica
Gel 60 (Kanto Chemical Co., Inc.) was used for flash column
chromatography. Merck Kieselgel 60 F254 (0.25 mm thickness,
coated on glass 20 © 20 cm2) plate was used for analytical
thin layer chromatography (TLC), and Wakogel B-5F coated on
glass with a thickness of 0.9 mm was used for preparative TLC.
Elemental analyses were performed on an Elementar Vario
MICRO. THF and toluene were purified by Glass-Contour
solvent purification system. AlEt3 (0.95 M solution in toluene)
was purchased from Kanto Chemicals. Bis(pinacolato)diboron
was purchased from Aldrich and purified by recrystallization
from hexane before use. Pd complexes 1a,16a 1f,17 and 1g,17
were prepared according to a previously reported method.
Alkenes 5m29 and 5n30 and 1,3-dienes 7a,31 7b,32 7c,33 7d,16c
7e,16c 7f,34 and 7g35 were known compounds in literature
and others were commercially available. The geometry of the
obtained boronic esters was determined by coupling constants
between two olefinic protons or by NOE measurement.
(E)-4,4,5,5-Tetramethyl-2-styryl-1,3,2-dioxaborolane (6a):
1
105.8 mg, 0.46 mmol from 0.50 mmol of 5a. H NMR (CDCl3,
500 MHz): ¤ 1.31 (12H, s), 6.16 (1H, d, J = 9.1 Hz), 7.27-
7.35 (3H, m), 7.39 (1H, d, J = 9.1 Hz), 7.48 (2H, d, J = 7.9
Hz). Spectral data were in good agreement with literature
values.36
(E)-4,4,5,5-Tetramethyl-2-(2-phenylprop-1-en-1-yl)-1,3,2-
dioxaborolane (6b): 106.6 mg, 0.437 mmol from 0.50 mmol
1
of 5b. H NMR (CDCl3, 500 MHz): ¤ 1.32 (12H, s), 2.41 (3H,
s), 5.76 (1H, s), 7.27-7.34 (3H, m), 7.48-7.52 (2H, m). Spectral
data were in good agreement with literature values.12b
2-(2,2-Diphenylvinyl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (6c): 64.1 mg, 0.20 mmol from 0.20 mmol of 4d.
1H NMR (CDCl3, 500 MHz): ¤ 1.18 (12H, s), 6.03 (1H, s),
7.27-7.36 (10H, m). Spectral data were in good agreement with
literature values.37
General Procedure for Dehydrogenative Monoborylation
of Alkene. To a solution of bis(pinacolato)diboron (50.8 mg,
0.20 mmol) and palladium catalyst 1f (2.7-27.3 mg, 0.002-
0.02 mmol) in toluene (2.0 mL) were added AlEt3 (0.95 M in
toluene, 2.0-21.0 ¯L, 0.02-0.02 mmol) and an alkene 5 (0.20
mmol) at room temperature in a 30-mL two-necked flask
equipped with a three-way stopcock. The mixture was stirred
(Z)-4,4,5,5-Tetramethyl-2-(1-phenylprop-1-en-2-yl)-1,3,2-
dioxaborolane (6d): 108.2 mg, 0.443 mmol from 0.50 mmol
1
of 4f. H NMR (CDCl3, 500 MHz): ¤ 1.32 (12H, s), 1.99 (3H,
s), 7.22-7.27 (2H, m), 7.32-7.40 (4H, m). Spectral data were in
good agreement with literature values.38

794
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
(E)-2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)ferro-
cene (6e): 62.8 mg, 0.186 mmol from 0.20 mmol of 5e.
1H NMR (CDCl3, 500 MHz): ¤ 1.30 (12H, s), 4.11 (5H, s), 4.27
(2H, s), 4.43 (2H, s), 5.72 (1H, d, J = 18.2 Hz), 7.22 (1H, d,
J = 18.2 Hz). Spectral data were in good agreement with
literature values.8a
1H NMR (CDCl3, 500 MHz): ¤ 1.22 (12H, s), 2.56 (2H, d,
J = 8.0 Hz), 5.34 (1H, d, J = 17.7 Hz), 6.73 (1H, dt, J =
17.7, 8.0 Hz), 7.33-7.37 (6H, m), 7.39-7.43 (3H, m), 7.49-
7.52 (6H, m); 13C NMR (CDCl3, 125 MHz): ¤ 24.67, 24.79,
82.8, 127.8, 129.6, 134.3, 135.7, 150.0 (the olefinic carbon
atom connected to B is missing); (Z)-isomer: 1H NMR (CDCl3,
500 MHz): ¤ 1.14 (12H, s), 2.93 (2H, d, J = 8.5 Hz), 5.26
(1H, d, J = 13.3 Hz), 6.58 (1H, dt, J = 13.3, 8.5 Hz), 7.32-
7.41 (9H, m), 7.51-7.56 (6H, m); 13C NMR (CDCl3, 125
MHz): ¤ 21.5, 24.8, 82.6, 127.7, 129.4, 134.6, 135.9, 150.6
(the olefinic carbon atom connected to B is missing); Anal.
Calcd for C27H31BO2Si: C, 76.05; H, 7.33%. Found: C, 76.07;
H, 7.09%.
2-(3-Cyclopentylprop-1-en-1-yl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (6f): E:Z = 93:7, 20.6 mg, 0.0872 mmol
from 0.20 mmol of 5f. IR (neat): 2951, 1637, 1362, 1318, 1145
1
cm¹1; H NMR (CDCl3, 500 MHz): (E)-isomer: ¤ 1.09-1.16
(2H, m), 1.26 (12H, m), 1.44-1.62 (4H, m), 1.70-1.78 (2H, m),
1.87-1.94 (1H, m), 2.16 (2H, td, J = 6.9, 1.5 Hz), 5.41 (1H, dt,
J = 17.9, 1.5 Hz), 6.62 (1H, dt, J = 17.9, 6.9 Hz); character-
istic resonances of the (Z)-isomer: 2.39 (1H, t, J = 8.0 Hz), 5.33
(1H, d, J = 13.0 Hz), 6.40-6.47 (1H, m); 13C NMR (CDCl3, 125
MHz): ¤ 24.8, 25.1, 32.4, 39.0, 42.4, 83.0, 154.1 (the olefinic
carbon atom connected to B is missing); Anal. Calcd for
C14H25BO2: C, 71.20; H, 10.67%. Found: C, 71.08; H, 10.40%.
4,4,5,5-Tetramethyl-2-(2-methyl-4-phenylbut-1-en-1-yl)-
1,3,2-dioxaborolane (6g): E:Z = 37:63, 44.8 mg, 0.165 mmol
(E)-Triphenyl[2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)vinyl]silane (6l): 72.6 mg, 0.176 mmol from 0.20 mmol
¹1
of 7k. IR (neat): 3066, 2965, 1588, 1427, 1325, 1261 cm
;
1H NMR (CDCl3, 500 MHz): ¤ 1.28 (12H, s), 6.38 (1H, d, J =
21.7 Hz), 7.33-7.37 (6H, m), 7.38-7.43 (3H, m), 7.51-7.54 (6H,
m), 7.58 (1H, d, J = 21.7 Hz); 13C NMR (CDCl3, 125 MHz): ¤
24.8, 83.5, 127.8, 129.5, 133.8, 136.1, 150.5 (the olefinic carbon
atom connected to B is missing); Anal. Calcd for C26H29BO2Si:
C, 75.72; H, 7.09%. Found: C, 75.58; H, 6.93%.
1
from 0.20 mmol of 6g. H NMR (CDCl3, 500 MHz): ¤ 1.26
((Z), 12H, s), 1.28 ((E), 12H, s), 1.91 ((Z), 3H, s), 2.04 ((E),
3H, s), 2.38-2.43 ((E), 2H, m), 2.66-2.75 ((Z), 4H, m), 2.75-
2.79 ((E), 2H, m), 5.17 ((Z), 1H, s), 5.21 ((E), 1H, s), 7.15-
7.20 (both isomers, 2H, m), 7.23-7.30 (both isomers, 3H, m).
Spectral data were in good agreement with literature values.39
4,4,5,5-Tetramethyl-2-(oct-1-en-1-yl)-1,3,2-dioxaborolane
(6h): E:Z = 93:7, 40.6 mg, 0.170 mmol from 0.20 mmol of
tert-Butyldimethyl{[1-phenyl-4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)but-3-en-1-yl]oxy}silane (6m):
E:Z =
88:12, 48.4 mg, 0.125 mmol from 0.20 mmol of 5m. IR (neat):
¹1
2957, 2929, 2857, 1638, 1361, 1321, 1257 cm
;
1H NMR
(CDCl3, 500 MHz): ¤ ¹0.13 ((E), 3H, s), ¹0.11 ((Z), 3H, s),
0.01 ((E), 3H, s), 0.02 ((Z), 3H, s), 0.87 (both isomers, 9H, s),
1.25 (both isomers, 12H, s), 2.42-2.48 ((E), 1H, m), 2.52 ((E),
1H, dt, J = 14.2, 7.0 Hz), 2.72-2.87 ((Z), 2H, m), 4.70 ((E), 1H,
dd, J = 8.0, 4.6 Hz), 4.72-4.75 ((Z), 1H, m), 5.41 ((Z), 1H, d,
J = 13.5 Hz), 5.46 ((E), 1H, d, J = 18.1 Hz), 6.39-6.44 ((Z),
1H, m), 6.64 ((E), 1H, dt, J = 18.1, 7.0 Hz), 7.20-7.32 (both
isomers, 5H, m); 13C NMR (CDCl3, 125 MHz): ¤ ¹4.9, ¹4.6,
18.3, 24.70, 24.74, 25.8, 47.7, 74.8, 83.0, 125.8, 127.0, 128.0,
145.2, 151.2 (the olefinic carbon atom connected to B is
missing); Anal. Calcd for C22H37BO3Si: C, 68.03; H, 9.60%.
Found: C, 67.89; H, 9.31%.
1
7h. IR (neat): 2926, 1638, 1361, 1318, 1143 cm¹1; H NMR
(CDCl3, 500 MHz): (E)-isomer: ¤ 0.82-0.92 (3H, m), 1.27
(12H, s), 1.22-1.34 (6H, m), 1.36-1.44 (2H, m), 2.14 (2H, q,
J = 8.1 Hz), 5.43 (1H, d, J = 18.8 Hz), 6.62 (1H, dt, J = 18.8,
8.1 Hz). 13C NMR (CDCl3, 125 MHz): ¤ 14.1, 22.6, 24.8, 28.2,
28.9, 31.7, 35.8, 83.0, 154.8 (the olefinic carbon atom con-
nected to B is missing). Characteristic resonances of the (Z)-
isomer: 2.33-2.42 (2H, m), 5.32 (1H, d, J = 13.4 Hz), 6.38-
6.46 (1H, m). Spectral data of both isomers were in good
agreement with literature values.36,40
2-(Cyclohept-1-en-1-yl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
2-(3-Chloroprop-1-en-1-yl)-4,4,5,5-tetramethyl-1,3,2-di-
oxaborolane (6n): E:Z = 92:8, 19.5 mg, 0.107 mmol from
0.20 mmol of 5n. IR (neat): 2978, 1638, 1362, 1319, 1140
borolane (6i):
43.7 mg, 0.197 mmol from 0.20 mmol of
1
7i. H NMR (CDCl3, 500 MHz): ¤ 1.26 (12H, s), 1.43-1.50
(4H, m), 1.71-1.77 (2H, m), 2.20-2.28 (4H, m), 6.77 (1H,
t, J = 5.6 Hz). Spectral data were in good agreement with
literature values.41
1
cm¹1; H NMR (CDCl3, 500 MHz): (E)-isomer: ¤ 1.27 (12H,
s), 2.62 (2H, q, J = 7.0 Hz), 3.57 (2H, t, J = 7.0 Hz), 5.55 (1H,
d, J = 18.0 Hz), 6.57 (1H, dt, J = 18.0, 7.0 Hz); characteristic
resonances of the (Z)-isomer: 2.87 (2H, q, J = 7.5 Hz), 5.52
(1H, d, J = 13.0 Hz), 6.40-6.48 (1H, m); 13C NMR (CDCl3,
125 MHz): ¤ 24.8, 38.6, 42.8, 83.3, 148.8 (the olefinic carbon
atom connected to B is missing); Anal. Calcd for C10H18-
BClO2: C, 55.47; H, 8.38%. Found: C, 55.23; H, 8.08%.
4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)but-3-
enenitrile (6o): E:Z = 62:38. The (E)-isomer was roughly
purified by silica gel column chromatography at low tem-
perature, and its spectral data are shown below. On the other
hand, the (Z)-isomer was not obtained after column chroma-
tography probably due to its instability to silica gel. Therefore,
Trimethyl[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)allyl]silane (6j): E:Z = 87:13, obtained as a mixture with
9j (6j:9j = 82:18), 37.5 mg, 0.117 mmol of 6j from 0.20 mmol
1
of 5j. H NMR (CDCl3, 500 MHz): ¤ ¹0.02 ((Z), 9H, s), 0.02
((E), 9H, s), 1.24 ((Z), 12H, s), 1.25 ((E), 12H, s), 1.69 ((E), 2H,
d, J = 8.2 Hz), 2.04 ((Z), 2H, d, J = 9.0 Hz), 5.18 ((Z), 1H, d,
J = 12.2 Hz), 5.23 ((E), 1H, dt, J = 17.7, 1.2 Hz), 6.48-6.55
((Z), 1H, m), 6.66 ((E), 1H, dt, J = 17.7, 8.2 Hz). Spectral data
were in good agreement with literature values.15
Triphenyl[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)allyl]silane (6k): E:Z = 75:25, (Z)-isomer was obtained
as a mixture with a small amount of 1-propenyltriphenyl-
silane and some isomers of alkenylboronic ester (less than
4%). (E)-6k: 53.5 mg, 0.126 mmol from 0.20 mmol of 5k.
IR (neat): 2975, 1622, 1427, 1358, 1325 cm¹1; (E)-isomer:
1
the yield and the E:Z ratio of 6o were determined by H NMR
of the crude mixture using tetrachloroethane as an internal
standard. (E)-isomer: IR (neat): 2979, 1643, 1362, 1330, 1279,
1138 cm¹1; 1H NMR (CDCl3, 500 MHz): ¤ 1.27 (12H, s), 3.19-

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
795
3.22 (2H, m), 5.87 (1H, d, J = 17.8 Hz), 6.42 (1H, dt, J =
17.8, 5.0 Hz); 13C NMR (CDCl3, 125 MHz): ¤ 23.2, 24.7, 83.7,
116.5, 138.6 (the olefinic carbon atom connected to B is miss-
ing); (Z)-isomer: 1H NMR (CDCl3, 500 MHz): ¤ 1.27 (12H, s),
3.54 (2H, dd, J = 7.1, 1.6 Hz), 5.65 (1H, brd, J = 11.7 Hz),
6.30-6.38 (1H, m).
chromatography (hexanes/AcOEt) at low temperature to give
dienylboronic.
4,4,5,5-Tetramethyl-2-(4-phenylbuta-1,3-dien-1-yl)-1,3,2-
dioxaborolane (8a):
(1E, 3E):(1Z, 3E) = 58:42, 20.6 mg,
0.080 mmol, 80%. IR (neat): 1584, 1453, 1424, 1372, 1335,
¹1
1255, 1135 cm
;
1H NMR (CDCl3, 300 MHz): ¤ 1.30 ((E),
3-[3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)allyl]-
dihydrofuran-2,5-dione (6p): E:Z = 86:14. A part of the (E)-
isomer was purified by silica gel column chromatography at
low temperature, and its spectral data are shown below. Most
of (E)- and (Z)-isomer were obtained as a mixture with some
unidentified compounds derived from the Pd-complex after
column chromatography, and therefore the yield and the E:Z
12H, s), 1.33 ((Z), 12H, s), 5.48 ((Z), 1H, d, J = 13.3 Hz),
5.68 ((E), 1H, d, J = 17.8 Hz), 6.65 ((Z), 1H, d, J = 15.3 Hz),
6.70 ((E), 1H, d, J = 15.8 Hz), 6.86 (1H, dd, J = 10.3,
15.8 Hz), 7.02 ((Z), 1H, dd, J = 11.3, 13.3 Hz), 7.18 ((E), 1H,
dd, J = 10.3, 17.8 Hz), 7.22-7.51 (both isomers, 5H, m);
13C NMR (CDCl3, 100 MHz): ¤ 24.7, 24.9, 83.1, 83.2, 126.8,
127.9, 128.1, 128.5, 128.6, 129.3, 130.5, 136.0, 136.3, 136.7,
137.1, 149.7, 150.3 (the olefinic carbon atom connected to B
is missing); HRMS Calcd for C16H21BO2, 256.1635, found
256.1624.
1
ratio of 6p were determined by H NMR of the crude mixture
using tetrachloroethane as an internal standard. (E)-isomer:
IR (neat): 2979, 1861, 1774, 1364 cm¹1; 1H NMR (CDCl3, 500
MHz): ¤ 1.27 (12H, s), 2.48-2.56 (1H, m), 2.70 (1H, dd,
J = 18.9, 6.6 Hz), 2.77-2.93 (1H, m), 3.07 (1H, dd, J = 18.9,
9.9 Hz), 3.22-3.29 (1H, m), 5.57 (1H, d, J = 17.9 Hz), 6.47
(1H, dt, J = 17.9, 6.6 Hz); 13C NMR (CDCl3, 125 MHz):
¤ 24.74, 24.77, 33.4, 36.4, 39.6, 83.5, 146.3, 169.6, 173.0
(the olefinic carbon atom connected to B is missing); Anal.
Calcd for C13H19BO5: C, 58.68; H, 7.20%. Found: C, 58.64;
2-(4,4-Diphenylbuta-1,3-dien-1-yl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (8b):
E:Z = 87:13, 26.5 mg, 0.098
mmol, 98%. IR (neat): 2974, 1605, 1445, 1378, 1371, 1326,
¹1
1254, 1142 cm
;
1H NMR (CDCl3, 300 MHz): E-isomer: ¤
1.22 (12H, s), 5.75 (1H, d, J = 17.7 Hz), 6.74 (1H, d, J = 11.1
Hz), 7.09 (1H, dd, J = 11.1, 17.7 Hz), 7.20-7.39 (10H, m);
characteristic resonances of the (Z)-isomer: ¤ 1.31 (12H, s),
5.41 (1H, d, J = 13.8 Hz), 6.93 (1H, dd, J = 12.0, 13.8
Hz), 7.63 (1H, d, J = 12.0 Hz); 13C NMR (CDCl3, 100 MHz):
¤ 24.7, 83.1, 127.6, 127.8, 127.9, 128.2, 130.1, 130.5, 139.4,
142.2, 145.9, 146.9 (the olefinic carbon atom connected to B
is missing); HRMS Calcd for C22H25BO2, M + H 333.2026,
found 333.2024.
4,4,5,5-Tetramethyl-2-(4-phenylpenta-1,3-dien-1-yl)-1,3,2-
dioxaborolane (8c): The geometry of the two isomers (1E,
3E)-8c and (1E, 3Z)-8c was determined by the observation
of NOE between the methyl protons and the olefinic proton
of 3-position or 2-position, (1E, 3E):(1E, 3Z) = 86:14. This
compound contained small amounts of other stereoisomers
1
H, 6.90%. Characteristic resonances of (Z)-isomer: H NMR
(CDCl3, 500 MHz): ¤ 5.62 (1H, d, J = 13.5 Hz), 6.29-6.36
(1H, m).
4,4,5,5-Tetramethyl-2-[3-(phenylsulfonyl)prop-1-en-1-yl]-
1,3,2-dioxaborolane (6q): E:Z = 56:44, 42.3 mg, 0.137 mmol
from 0.20 mmol of 5q. IR (neat): 2979, 1629, 1447, 1421,
1
1308, 1281, 1263 cm¹1; H NMR (CDCl3, 500 MHz): ¤ 1.14
((Z), 12H, s), 1.23 ((E), 12H, s), 3.88 ((E), 2H, d, J = 7.5
Hz), 4.34 ((Z), 2H, d, J = 7.8 Hz), 5.51 ((E), 1H, d, J = 16.9
Hz), 5.66 ((Z), 1H, d, J = 13.4 Hz), 6.36-6.43 ((Z), 1H, m),
6.49 ((E), 1H, dt, J = 16.9, 7.5 Hz), 7.49-7.65 (both isomers,
3H, m), 7.84-7.90 (both isomers, 2H, m); 13C NMR (CDCl3,
125 MHz): (E)-isomer: ¤ 24.7, 62.6, 83.6, 128.4, 129.0, 133.8,
137.3, 138.7 (the olefinic carbon atom connected to B is
missing); (Z)-isomer: 24.7, 58.7, 83.4, 128.6, 128.8, 133.4,
136.6, 138.6 (the olefinic carbon atom connected to B is
missing); Anal. Calcd for C15H21BO4S: C, 58.46; H, 6.87; S,
10.40%. Found: C, 58.28; H, 6.59; S, 10.61%.
(1Z, 3E/Z)-8c (ca. 5%), 26.5 mg, 0.098 mmol, 98%. IR (neat):
¹1
2981, 2360, 2343, 1617, 1592, 1355, 1336, 1259, 1137 cm
;
1H NMR (CDCl3, 500 MHz): ¤ 1.22 ((Z), 12H, s), 1.30 ((Z),
12H, s), 2.15 ((Z), 3H, s), 2.26 ((E), 3H, d, J = 1.1 Hz), 5.54
((Z), 1H, d, J = 17.6 Hz), 5.67 ((E), 1H, d, J = 17.2 Hz), 6.23
((Z), 1H, d, J = 10.9 Hz), 6.55 ((E), 1H, d, J = 10.9 Hz), 7.05
((Z), 1H, dd, J = 10.9, 17.6 Hz), 7.22-7.39 (both isomers,
3H, m), 7.45 ((E), 1H, dd, J = 10.9, 17.2 Hz), 7.43-7.53 (both
isomers, 2H, m); 13C NMR (CDCl3, 100 MHz): ¤ 16.3, 24.7,
83.2, 125.8, 127.6, 128.3, 129.1, 140.3, 142.6, 145.8 (the
olefinic carbon atom connected to B is missing); HRMS Calcd
for C17H23BO2, 270.1791, found 270.1796.
(E)-2-[2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-
vinyl]isoindoline-1,3-dione (6r):
54.1 mg, 0.181 mmol
from 0.20 mmol of 5r. IR (neat): 2978, 1725, 1625, 1345,
1
1309 cm¹1; H NMR (CDCl3, 500 MHz): ¤ 1.30 (12H, s), 6.45
(1H, d, J = 16.9 Hz), 7.47 (1H, d, J = 16.9 Hz), 7.74-7.78 (2H,
m), 7.88-7.91 (2H, m); 13C NMR (CDCl3, 125 MHz): ¤ 24.8,
83.4, 123.8, 131.6, 133.7, 134.7, 166.2 (the olefinic carbon
atom connected to B is missing); Anal. Calcd for C16H18BNO4:
C, 64.24; H, 6.07; N, 4.68%. Found: C, 64.16; H, 5.80; N,
4.42%.
General Procedure for Dehydrogenative Monoborylation
of 1,3-Diene. To a solution of bis(pinacolato)diboron (25.4
mg, 0.10 mmol) and palladium catalyst 1f or 1g (0.025 mmol)
in toluene (1.0 mL) were added AlEt3 (0.95 M in toluene,
2.6 ¯L, 0.025 mmol) and 1,3-diene 7 (0.10 mmol) at room tem-
perature in a 30-mL flask. The mixture was stirred for 6 h at
60 °C. After the solvent was removed under reduced pressure,
the resulting crude product was purified by silica gel column
4,4,5,5-Tetramethyl-2-(4-methyl-6-phenylhexa-1,3-dien-
1-yl)-1,3,2-dioxaborolane (8d): The geometry of the two
isomers (1E, 3E)-8d and (1E, 3Z)-8d was determined by the
observation of NOE between the olefinic proton of 3-position
and the methylene protons or the methyl protons, (1E, 3E):
(1E, 3Z) = 74:26. This compound contained small amounts of
other stereoisomers (1Z, 3E/Z)-8d (ca. 5%), 27.7 mg, 0.093
mmol, 93%. IR (neat): 2977, 1638, 1599, 1364, 1336, 1315,
1
1143 cm¹1; H NMR (CDCl3, 500 MHz): ¤ 1.22 ((Z), 12H, s),
1.30 ((Z), 12H, s), 2.15 ((Z), 3H, s), 2.26 ((E), 3H, d, J =
1.1 Hz), 5.54 ((Z), 1H, d, J = 17.6 Hz), 5.67 ((E), 1H, d, J =
17.2 Hz), 6.23 ((Z), 1H, d, J = 10.9 Hz), 6.55 ((E), 1H, d, J =

796
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
10.9 Hz), 7.05 ((Z), 1H, dd, J = 10.9, 17.6 Hz), 7.22-7.39
(both isomers, 3H, m), 7.45 ((E), 1H, dd, J = 10.9, 17.2 Hz),
7.43-7.53 (both isomers, 2H, m); 13C NMR (CDCl3, 125 MHz):
¤ 17.3, 24.7, 34.4, 41.9, 83.0, 125.8, 127.7, 128.3, 141.8,
143.2, 145.3, 145.9 (the olefinic carbon atom connected to B
is missing); HRMS Calcd for C19H27BO2, 298.2104, found
298.2084.
2,2¤-(2-Phenylethene-1,1-diyl)bis(4,4,5,5-tetramethyl-1,3,2-
dioxaborolane) (9a): 161 mg, 0.451 mmol from 0.50 mmol of
5a. 1H NMR (CDCl3, 500 MHz): ¤ 1.28 (12H, s), 1.31 (12H, s),
7.25-7.31 (3H, m), 7.46-7.50 (2H, m), 7.71 (1H, s). Spectral
data were in good agreement with literature values.42
2,2¤-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2yl)ferro-
cene (9e): 43.2 mg, 0.0923 mmol from 0.10 mmol of 5e. IR
(neat): 2977, 1597, 1460, 1409, 1389, 1370, 1346, 1313, 1286,
4,4,5,5-Tetramethyl-2-[3-(4-phenylcyclohexylidene)prop-
1-en-1-yl]-1,3,2-dioxaborolane (8e): E:Z = 85:15, 28.6 mg,
1
1262, 1236 cm¹1; H NMR (CDCl3, 500 MHz): ¤ 1.27 (12H,
0.091 mmol, 91%. IR (neat): 2974, 1640, 1599, 1380, 1343,
1317, 1141 cm
s), 1.35 (12H, s), 4.14 (5H, s), 4.26 (2H, s), 4.51 (2H, s), 7.46
(2H, s); 13C NMR (CDCl3, 125 MHz): ¤ 24.87, 24.88, 68.9,
69.4, 69.6, 82.9, 83.3, 84.1, 154.3 (the olefinic carbon atom
connected to B is missing); Anal. Calcd for C24H34B2FeO4: C,
62.13; H, 73.9%. Found: C, 62.02; H, 7.09%.
2-[2,2-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
vinyl]isoindoline-1,3-dione (9r): 73.1 mg, 0.172 mmol from
0.20 mmol of 5r. IR (neat): 2973, 1728, 1628, 1329, 1306
cm¹1; 1H NMR (CDCl3, 500 MHz): ¤ 1.27 (12H, s), 1.36 (12H,
s), 7.53 (1H, s), 7.72-7.76 (2H, m), 7.85-7.89 (2H, m);
13C NMR (CDCl3, 125 MHz): ¤ 24.8, 25.3, 83.3, 83.5, 123.8,
131.7, 134.5, 134.8, 166.2 (the olefinic carbon atom connected
to B is missing); Anal. Calcd for C22H29B2NO6: C, 62.16; H,
6.88; N, 3.29%. Found: C, 62.01; H, 6.59; N, 2.99%.
¹1
;
1H NMR (CDCl3, 400 MHz): ¤ 1.34 ((E),
12H, s), 1.36 ((Z), 12H, s), 1.50-1.72 (both isomers, 2H, m),
2.00-2.12 (both isomers, 2H, m), 2.30-2.56 (both isomers, 2H,
m), 2.72-2.84 (both isomers, 2H, m), 3.20-3.40 (both isomers,
1H, m), 5.37 ((Z), 1H, d, J = 13.7 Hz), 5.56 ((E), 1H, d, J =
17.7 Hz), 6.03 (1H, d, J = 11.3 Hz), 6.76 (1H, d, J = 11.2 Hz),
7.20-7.40 (both isomers, 5H, m), 7.32-7.36 (2H, m), 7.41 ((E),
1H, d, J = 17.7 Hz); 13C NMR (CDCl3, 100 MHz): ¤ 24.7,
29.3, 35.0, 35.6, 37.1, 44.5, 83.0, 125.2, 126.0, 126.8, 128.4,
145.3, 146.5, 146.9 (the olefinic carbon atom connected to B
is missing); HRMS Calcd for C21H29BO2, 324.2261, found
324.2241.
(E)-4,4,5,5-Tetramethyl-2-(3-methyl-4,4-diphenylbuta-
1,3-dien-1-yl)-1,3,2-dioxaborolane (8f):
31.2 mg, 0.090,
2,2¤-(4,4-Diphenylbuta-1,3-diene-1,1-diyl)bis(4,4,5,5-tetra-
90%. IR (neat): 3326, 2979, 1600, 1379, 1339, 1322, 1141,
methyl-1,3,2-dioxaborolane) (10b):
98%. IR (neat): 2979, 1371, 1327, 1279, 1258, 1142 cm
44.8 mg, 0.098 mmol,
1
¹1
1022 cm¹1; H NMR (CDCl3, 300 MHz): ¤ 1.23 (12H, s), 1.93
;
(3H, s), 5.74 (1H, d, J = 18.0 Hz), 7.10-7.14 (4H, m), 7.20-
7.34 (7H, m); 13C NMR (CDCl3, 100 MHz): ¤ 16.7, 24.7, 83.0,
126.8, 127.0, 129.9, 130.8, 132.6, 141.8, 143.2, 145.3, 150.1
(the olefinic carbon atom connected to B is missing); HRMS
Calcd for C23H27BO2, 346.2104, found 346.2114.
4,4,5,5-Tetramethyl-2-(2-methyl-4-phenylbuta-1,3-dien-
1-yl)-1,3,2-dioxaborolane (8g): The geometry of the two
isomers (1E, 3E)-8g and (1Z, 3E)-8g was determined by the
observation of NOE between the olefinic proton of 1-position
and the olefinic proton of 3-position or the methyl protons,
1H NMR (CDCl3, 300 MHz): ¤ 1.18 (12H, s), 1.36 (12H, s),
7.15 (1H, d, J = 11.6 Hz), 7.30-7.40 (11H, m); 13C NMR
(CDCl3, 100 MHz): ¤ 24.7, 24.8, 82.9, 83.3, 127.6, 127.8,
128.0, 128.1, 129.3, 130.8, 139.1, 142.6, 147.0, 154.0 (the
olefinic carbon atom connected to B is missing); HRMS Calcd
for C28H36B2O4, 458.2800, found 458.2794.
(E)-2,2¤-(4-Phenylpenta-1,3-diene-1,1-diyl)bis(4,4,5,5-
tetramethyl-1,3,2-dioxaborolane) (10c): The geometry of
the product was determined by the observation of an NOE
between the methyl protons and the olefinic proton of 2-
position, 36.9 mg, 0.093 mmol, 93%. IR (neat): 2979, 1609,
(1E, 3E):(1Z, 3E) = 62:38, 12.5 mg, 0.046 mmol, 46%. IR
¹1
1
(neat): 2977, 1602, 1449, 1363, 1322, 1289, 1257, 1141 cm
;
1540, 1370, 1325, 1288, 1255, 1139 cm¹1; H NMR (CDCl3,
1H NMR (CDCl3, 300 MHz): (E)-isomer: ¤ 1.30 ((E), 12H, s),
1.32 ((Z), 12H, s), 2.11 ((Z), 3H, s), 2.23 ((E), 3H, s), 5.41 ((Z),
1H, s), 5.47 ((E), 1H, s), 6.69 (both isomers, 1H, d, J = 16.0
Hz), 6.87 ((E), 1H, d, J = 16.0 Hz), 7.21-7.50 (both isomers,
10H, m), 7.87 ((Z), 1H, J = 16.0 Hz); 13C NMR (CDCl3, 100
MHz): ¤ 16.6, 24.8, 82.9, 126.7, 126.8, 127.8, 128.6, 130.6,
134.8, 155.3 (the olefinic carbon atom connected to B is miss-
ing); HRMS Calcd for C17H23BO2, 270.1791, found 270.1795.
General Procedure for the Dehydrogenative Diborylation
of Alkenes and 1,3-Dienes. To a solution of bis(pinacolato)-
diboron (101.6 mg, 0.40 mmol) and the palladium catalyst 1f
(2.7-27.3 mg, 0.002-0.02 mmol) or 1g (3.0-30.0 mg, 0.002-
0.02 mmol) in toluene (2.0 mL) were added AlEt3 (0.95 M
in toluene, 2.0-21.0 ¯L, 0.02-0.02 mmol) and alkene 5 (0.20
mmol) or diene 7 (0.10 mmol) at room temperature in a 30-mL
two-necked flask equipped with three-way stopcock. The
mixture was stirred for 24 h at room temperature or 6 h at
60 °C. After the solvent was removed under reduced pressure,
the resulting crude product was purified by silica gel column
chromatography (hexanes/AcOEt) at low temperature to give
diborylalkenes 9 or dienes 10 (48%-98% yield).
300 MHz): ¤ 1.26 (12H, s), 1.34 (12H, s), 2.26 (3H, s), 6.95
(1H, d, J = 11.6 Hz), 7.23-7.45 (3H, m), 7.47 (2H, d, J =
7.0 Hz); 13C NMR (CDCl3, 100 MHz): ¤ 15.9, 24.7, 24.8,
82.9, 83.2, 125.9, 127.5, 128.2, 128.5, 141.4, 143.0, 152.9 (the
olefinic carbon atom connected to B is missing); HRMS Calcd
for C23H34B2O4, M + H 397.2721, found 397.2729.
2,2¤-(4-Methyl-6-phenylhexa-1,3-diene-1,1-diyl)bis(4,4,5,5-
tetramethyl-1,3,2-dioxaborolane) (10d): The geometry of
the two isomers were determined by the observation of NOE
between the methyl protons and the olefinic proton of 2- or 3-
position, E:Z = 73:17, 40.3 mg, 0.095 mmol, 95%. IR (neat):
¹1
2977, 1559, 1370, 1321, 1140 cm
;
1H NMR (CDCl3, 500
MHz): ¤ 1.24 ((E), 12H, s), 1.27 ((Z), 12H, s), 1.29 ((E), 12H, s),
1.31 ((Z), 12H, s), 2.36-2.41 ((E), 2H, m), 2.56-2.60 ((Z),
2H, m), 2.70-2.79 (both isomers, 2H, m), 6.29 ((Z), 1H, dd, J =
1.4, 11.8 Hz), 6.32 ((E), 1H, dd, J = 1.3, 11.4 Hz), 7.14-7.30
(both isomers, 5H, m), 7.58 ((Z), 1H, d, J = 11.8 Hz), 7.61 ((Z),
1H, d, J = 11.4 Hz); 13C NMR (CDCl3, 125 MHz): ¤ 17.3, 24.7,
24.8, 34.0, 42.1, 82.8, 83.1, 125.8, 126.7, 128.2, 128.3, 142.0,
144.9, 153.1 (the olefinic carbon atom connected to B is miss-
ing); HRMS Calcd for C25H38B2O4, 424.2956, found 424.2967.

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
797
2,2¤-[3-(4-Phenylcyclohexylidene)prop-1-ene-1,1-diyl]bis-
(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (10e): 39.8 mg,
0.089 mmol, 89%. IR (neat): 2977, 2928, 2360, 2341, 1559,
¹1.30, 24.8, 24.9, 26.0, 82.6, 83.5 (the olefinic carbon atoms
connected to B are missing); Anal. Calcd for C18H36B2O4Si: C,
59.04; H, 9.91%. Found: C, 59.01; H, 9.61%.
1
1370, 1320, 1140 cm¹1; H NMR (CDCl3, 400 MHz): ¤ 1.31
tert-Butyldimethyl{[1-phenyl-3,4-bis(4,4,5,5-tetramethyl-
1,3,2-dioxaborolan-2-yl)but-3-en-1-yl]oxy}silane (9m):
E:Z = 11:89, the geometry of the minor product was confirmed
to be E by the observation of an NOE between the methylene
protons and the olefinic proton, 69.9 mg, 0.136 mmol from
0.20 mmol of 5m. IR (neat): 2979, 2925, 2855, 1616, 1471,
(12H, s), 1.36 (12H, s), 1.52-1.78 (2H, m), 1.98-2.15 (2H, m),
2.30-2.52 (2H, m), 2.72-2.78 (2H, m), 3.16-3.30 (1H, m), 6.36
(1H, d, J = 11.9 Hz), 7.17-7.45 (5H, m), 7.74 (1H, d, J =
11.9 Hz); 13C NMR (CDCl3, 100 MHz): ¤ 24.7, 24.8, 28.9,
34.8, 35.5, 37.6, 44.6, 82.8, 83.1, 124.8, 126.0, 126.8, 128.3,
146.6, 148.4, 152.3 (the olefinic carbon atom connected to B
is missing); HRMS Calcd for C27H40B2O4, 450.3113, found
450.3120.
1
1346, 1328, 1311 cm¹1; H NMR (CDCl3, 500 MHz): ¤ ¹0.16
((E), 3H, s), ¹0.15 ((Z), 3H, s), ¹0.01 ((Z), 3H, s), 0.01 ((E),
3H, s), 0.84 (both isomers, 9H, s), 1.20 ((Z), 12H, s), 1.23 ((Z),
12H, s), 1.25 ((E), 12H, s), 1.29 ((E), 12H, s), 2.48-2.58 ((E),
2H, m), 2.73 ((Z), 1H, dd, J = 12.2, 6.4 Hz), 3.00 ((Z), 1H, dd,
J = 12.2, 7.6 Hz), 4.80 ((E), 1H, dd, J = 7.6, 5.6 Hz), 4.85-
4.89 ((Z), 1H, m), 5.82 ((E), 1H, s), 6.34 ((Z), 1H, s), 7.14-7.18
(both isomers, 1H, m), 7.22-7.32 (both isomers, 4H, m);
13C NMR (CDCl3, 125 MHz): (Z)-isomer: ¤ ¹4.67, ¹4.57,
18.3, 24.7, 24.8, 24.9, 25.0, 26.0, 44.9, 75.5, 82.9, 83.4, 126.4,
126.5, 127.6, 145.8 (the olefinic carbon atoms connected to
B are missing); Anal. Calcd for C28H48B2O5Si: C, 65.38; H,
9.41%. Found: C, 65.22; H, 9.14%.
(Z)-[2,3-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
allyl]triphenylsilane (9k): 88.8 mg, 0.161 mmol from 0.20
mmol of 5j. IR (neat): 2980, 1604, 1427, 1338, 1313, 1249,
1
1134 cm¹1; H NMR (CDCl3, 500 MHz): ¤ 0.97 (12H, s), 1.02
(12H, s), 3.12 (2H, s), 6.12 (1H, s), 7.27-7.37 (9H, m), 7.47-
7.52 (6H, m); 13C NMR (CDCl3, 125 MHz): ¤ 23.0, 24.5, 24.7,
82.5, 83.4, 127.3, 129.0, 135.2, 136.5 (the olefinic carbon
atoms connected to B are missing); Anal. Calcd for C33H42-
B2O4Si: C, 71.75; H, 7.66%. Found: C, 71.65; H, 7.40%.
2,2¤-(3-Cyclopentylprop-1-ene-1,2-diyl)bis(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolane) (9f): E:Z = 22:78, the geom-
etry of the minor product was confirmed to be E by the obser-
vation of an NOE between the methylene protons and the
olefinic proton, 61.6 mg, 0.170 mmol from 0.20 mmol of 5f.
2,2¤-(3-Chloroprop-1-ene-1,2-diyl)bis(4,4,5,5-tetramethyl-
1,3,2-dioxaborolane) (9n):
E:Z = 9:91, the geometry of
the minor product was confirmed to be E by the observation
of an NOE between the methylene protons and the olefinic
proton. This compound was obtained as a mixture with 6n and
dechlorinated product, 37.2 mg, 0.097 mmol from 0.20 mmol of
1
IR (neat): 2977, 2946, 1615, 1329, 1308, 1136 cm¹1; H NMR
(CDCl3, 500 MHz): ¤ 1.14-1.30 (both isomers, 2H, m), 1.237
((Z), 12H, s), 1.242 ((Z), 12H, s), 1.26 ((E), 12H, s), 1.31 ((E),
12H, s), 1.42-1.76 (both isomers, 6H, m), 1.87-1.99 (both
isomers, 1H, m), 2.23 ((E), 2H, d, J = 7.4 Hz), 2.47 ((Z), 2H, d,
J = 7.4 Hz), 5.83 ((E), 1H, s), 6.24 ((Z), 1H, s); 13C NMR
(CDCl3, 125 MHz): (E)-isomer: ¤ 24.87, 24.89, 24.98, 32.6,
39.0, 46.4, 83.2, 83.6 (the olefinic carbon atoms connected to
B are missing); (Z)-isomer: 24.7, 24.8, 25.00, 32.1, 39.3, 40.8,
82.8, 83.4 (the olefinic carbon atoms connected to B are
missing); Anal. Calcd for C20H36B2O4: C, 66.34; H, 10.02%.
Found: C, 66.09; H, 9.73%.
1
5n. IR (neat): 2979, 1610, 1371, 1313, 1138 cm¹1; H NMR
(CDCl3, 500 MHz): (E)-isomer: ¤ 1.27 (24H, s), 2.66 (2H, t,
J = 7.5 Hz), 3.56 (2H, t, J = 7.5 Hz), 6.01 (1H, s); (Z)-isomer:
¤ 1.24 (12H, s), 1.25 (12H, s), 2.92 (2H, t, J = 7.3 Hz), 3.59
(2H, t, J = 7.3 Hz), 6.42 (1H, s); 13C NMR (CDCl3, 125 MHz):
(Z)-isomer: ¤ 24.7, 24.8, 36.3, 45.0, 83.2, 83.7 (the olefinic
carbon atoms connected to B are missing); Anal. Calcd for
C16H29B2ClO4: C, 56.11; H, 8.54%. Found: C, 56.03; H, 8.26%.
(Z)-3-[2,3-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)allyl]dihydrofuran-2,5-dione (9p): 46.3 mg, 0.118 mmol
from 0.20 mmol of 5p. IR (neat): 2978, 1860, 1777, 1348,
2,2¤-(Oct-1-ene-1,2-diyl)bis(4,4,5,5-tetramethyl-1,3,2-di-
1
oxaborolane) (9h): E:Z = 19:81, 46.1 mg, 0.127 mmol from
1326, 1308, 1279, 1261 cm¹1; H NMR (CDCl3, 500 MHz): ¤
¹1
0.20 mmol of 7h. IR (neat): 2977, 2927, 1323, 1141 cm
;
1.27 (24H, s), 2.81-2.93 (3H, m), 2.99 (1H, dd, J = 12.7,
5.3 Hz), 3.36-3.43 (1H, m), 6.48 (1H, s); 13C NMR (CDCl3,
125 MHz): ¤ 24.68, 24.74, 24.78, 24.80, 33.3, 34.4, 40.7, 83.6,
84.1, 170.7, 173.6 (the olefinic carbon atoms connected to B
are missing); Anal. Calcd for C19H30B2O7: C, 58.21; H, 7.71%.
Found: C, 57.92; H, 7.45%.
1H NMR (CDCl3, 500 MHz): (Z)-isomer: ¤ 0.82-0.92 (3H, m),
1.24 (24H, s), 1.20-1.44 (8H, m), 2.46 (2H, t, J = 8.1 Hz), 6.23
(1H, s); 13C NMR (CDCl3, 125 MHz): ¤ 14.1, 22.5, 24.7, 24.8,
29.0, 30.5, 31.7, 33.6, 82.8, 83.4 (the olefinic carbon atoms
connected to B are missing); HRMS Calcd for C20H39B2O4,
M + H 365.3034, found 365.3011. Characteristic resonances
(Z)-1,2-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
1
of the (E)-isomer: H NMR (CDCl3, 500 MHz): ¤ 2.21 (2H, t,
cyclooct-1-ene (9s): 49.7 mg, 0.137 mmol from 0.20 mmol of
¹1
J = 8.1 Hz), 5.84 (1H, s). Spectral data of (E)-isomer were in
good agreement with literature values.28a
[2,3-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
5s. IR (neat): 2977, 2926, 1616, 1472, 1378, 1335, 1298 cm ;
1H NMR (CDCl3, 500 MHz): ¤ 1.27 (24H, s), 1.40-1.45 (4H,
m), 1.46-1.53 (4H, m), 2.29-2.34 (4H, m); 13C NMR (CDCl3,
125 MHz): ¤ 24.8, 26.4, 28.8, 29.2, 83.1 (the olefinic carbon
atoms connected to B are missing); Anal. Calcd for C20H36-
B2O4: C, 66.34; H, 10.02%. Found: C, 66.15; H, 9.74%.
(Z)-2-(Cyclooct-1-en-1-yl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (6s): 17.2 mg, 0.0728 mmol from 0.20 mmol of 5s.
1H NMR (CDCl3, 500 MHz): ¤ 1.25 (12H, s), 1.40-1.52 (8H,
m), 2.18-2.30 (4H, m), 6.58 (1H, t, J = 8.0 Hz). Spectral data
were in good agreement with literature values.15
allyl]trimethylsilane (9j):
E:Z = 4:96, the geometry of
the minor product was confirmed to be E by the observation
of an NOE between the methylene protons and the olefinic
proton, 60.2 mg, 0.164 mmol from 0.20 mmol of 5j. IR (neat):
¹1
2978, 1602, 1309, 1247 cm
;
1H NMR (CDCl3, 500 MHz):
(E)-isomer: ¤ 0.02 (9H, s), 1.30 (24H, s), 1.79 (2H, s), 5.62
(1H, s); (Z)-isomer: ¹0.01 (9H, s), 1.24 (24H, s), 2.21 (2H, s),
6.07 (1H, s); 13C NMR (CDCl3, 125 MHz): (Z)-isomer: ¤

798
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013) BCSJ AWARD ARTICLE
12 Rh-catalyzed dehydrogenative borylation without hydro-
Crystallographic data have been deposited with The
Cambridge Crystallographic Data Centre: Deposition numbers
CCDC-853574 and 853878 for compound 2a and 9k. Copies
of the data can be obtained free of charge via www.ccdc.cam.
ac.uk/data_request/cif (or from The Cambridge Crystallograph-
ic Data Centre, 12, Union Road, Cambridge, CB2 1EZ, UK;
e-mail: data_request@ccdc.cam.ac.uk).
boration and hydrogenation was reported. See: a) R. B. Coapes,
F. E. S. Souza, R. L. Thomas, J. J. Hall, T. B. Marder, Chem.
Commun. 2003, 614. b) I. A. I. Mkhalid, R. B. Coapes, S. N. Edes,
D. N. Coventry, F. E. S. Souza, R. L. Thomas, J. J. Hall, S.-W. Bi,
Z. Lin, T. B. Marder, Dalton Trans. 2008, 1055.
13 Intramolecular dehydrogenative borylation using silyl-
borane was reported. See: T. Ohmura, Y. Takasaki, H. Furukawa,
M. Suginome, Angew. Chem., Int. Ed. 2009, 48, 2372.
14 Ir-catalyzed vinylic C-H borylation of cyclic vinyl ethers
was reported. See: a) T. Kikuchi, J. Takagi, T. Ishiyama, N.
Miyaura, Chem. Lett. 2008, 37, 664. b) T. Kikuchi, J. Takagi, H.
Isou, T. Ishiyama, N. Miyaura, Chem.®Asian J. 2008, 3, 2082.
15 N. Selander, B. Willy, K. J. Szabó, Angew. Chem., Int. Ed.
2010, 49, 4051.
16 a) J. Takaya, N. Iwasawa, J. Am. Chem. Soc. 2008, 130,
15254. b) J. Takaya, N. Iwasawa, Organometallics 2009, 28, 6636.
c) J. Takaya, K. Sasano, N. Iwasawa, Org. Lett. 2011, 13, 1698.
17 Preliminary communication: J. Takaya, N. Kirai, N.
Iwasawa, J. Am. Chem. Soc. 2011, 133, 12980.
18 a) T. G. Appleton, H. C. Clark, L. E. Manzer, Coord. Chem.
Rev. 1973, 10, 335. b) J. Zhu, Z. Lin, T. B. Marder, Inorg. Chem.
2005, 44, 9384.
19 a) S.-y. Onozawa, Y. Hatanaka, T. Sakakura, S. Shimada,
M. Tanaka, Organometallics 1996, 15, 5450. b) S.-y. Onozawa, M.
Tanaka, Organometallics 2001, 20, 2956. c) H. Braunschweig, K.
Gruss, K. Radacki, K. Uttinger, Eur. J. Inorg. Chem. 2008, 1462.
20 The reaction of (E)- and (Z)-4-octene using catalyst 1f
did not proceed, but the same reaction using catalyst 1g gave
a complex mixture of borylated products probably due to the
migration of the double bond during the reaction.
21 Recent synthetic applications see: a) R. S. Coleman, M. C.
Walczak, Org. Lett. 2005, 7, 2289. b) M. Tortosa, N. A. Yakelis,
W. R. Roush, J. Am. Chem. Soc. 2008, 130, 2722. c) X. Gao, D. G.
Hall, Tetrahedron Lett. 2003, 44, 2231. d) F. Tripoteau, T. Verdelet,
A. Hercouet, F. Carreaux, B. Carboni, Chem.®Eur. J. 2011, 17,
13670. e) S. Fujii, S. Y. Chang, M. D. Burke, Angew. Chem., Int.
Ed. 2011, 50, 7862.
This research was supported by a Grant-in-Aid for Scien-
tific from Ministry of Education, Culture, Sports, Science and
Technology of Japan.
Supporting Information
Synthesis of palladium complexes 1b-1e and 2a and spec-
tral data of these compounds are provided. This material is
available free of charge on the web at http://www.csj.jp/
journals/bcsj/.
References
1
Boronic Acids: Preparation and Applications in Organic
Synthesis and Medicine, ed. by D. G. Hall, Wiley, Weinheim,
2005. doi:10.1002/3527606548.
2
a) T. Ishiyama, M. Murata, N. Miyaura, J. Org. Chem.
1995, 60, 7508. b) T. Ishiyama, Y. Itou, T. Kitano, N. Miyaura,
Tetrahedron Lett. 1997, 38, 3447.
3
a) M. Murata, S. Watanabe, Y. Masuda, J. Org. Chem.
1997, 62, 6458. b) M. Murata, T. Oyama, S. Watanabe, Y. Masuda,
J. Org. Chem. 2000, 65, 164. c) M. Murata, T. Oyama, S.
Watanabe, Y. Masuda, Synthesis 2000, 778. d) M. Murata, S.
Watanabe, Y. Masuda, Tetrahedron Lett. 2000, 41, 5877.
4
Reviews see: a) C. F. Lane, G. W. Kabalka, Tetrahedron
1976, 32, 981. b) K. Burgess, M. J. Ohlmeyer, Chem. Rev. 1991,
91, 1179. c) I. Beletskaya, A. Pelter, Tetrahedron 1997, 53, 4957.
5
I. A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy,
J. F. Hartwig, Chem. Rev. 2010, 110, 890.
a) J. M. Brown, G. C. Lloyd-Jones, J. Chem. Soc., Chem.
6
Commun. 1992, 710. b) S. A. Westcott, T. B. Marder, R. T.
Baker, Organometallics 1993, 12, 975. c) J. M. Brown, G. C.
Lloyd-Jones, J. Am. Chem. Soc. 1994, 116, 866. d) M. Murata, S.
Watanabe, Y. Masuda, Tetrahedron Lett. 1999, 40, 2585. e) C. M.
Vogels, P. G. Hayes, M. P. Shaver, S. A. Westcott, Chem. Commun.
2000, 51. f) N. Iwadate, M. Suginome, Chem. Lett. 2010, 39, 558.
g) A. Kondoh, T. F. Jamison, Chem. Commun. 2010, 46, 907.
22 M. Gerdin, C. Moberg, Org. Lett. 2006, 8, 2929.
23 a) T. Hata, H. Kitagawa, H. Masai, T. Kurahashi, M.
Shimizu, T. Hiyama, Angew. Chem., Int. Ed. 2001, 40, 790.
b) D. S. Matteson, Synthesis 1975, 147.
24 a) Y. Gu, H. Pritzkow, W. Siebert, Eur. J. Inorg. Chem.
2001, 373. b) M. J. Bayer, H. Pritzkow, W. Siebert, Eur. J. Inorg.
Chem. 2002, 1293.
7
a) V. J. Olsson, K. J. Szabó, Angew. Chem., Int. Ed. 2007,
25 Selected synthetic applications see: a) M. Shimizu, C.
Nakamaki, K. Shimono, M. Schelper, T. Kurahashi, T. Hiyama,
J. Am. Chem. Soc. 2005, 127, 12506. b) S. J. Lee, K. C. Gray, J. S.
Paek, M. D. Burke, J. Am. Chem. Soc. 2008, 130, 466. c) C.-L. Li,
S.-J. Shieh, S.-C. Lin, R.-S. Liu, Org. Lett. 2003, 5, 1131.
26 The possibility of isomerization of diborylated product was
examined under the standard reaction conditions using (E)-1,2-
diboryl-1-hexene as substrate, and isomerization was found to
proceed slowly (after 6 h at 60 °C, 20% of (Z)-isomer was formed).
27 For the synthesis of 1,1-diboryldienes by the reaction of
1-halo-1-lithio-1,3-butadiene with diboron, see Ref. 23a.
28 a) T. Ishiyama, N. Matsuda, N. Miyaura, A. Suzuki, J. Am.
Chem. Soc. 1993, 115, 11018. Recently, Cu-catalyzed diborylation
of alkynes was reported. See: b) H. Yoshida, S. Kawashima, Y.
Takemoto, K. Okada, J. Ohshita, K. Takaki, Angew. Chem., Int. Ed.
2012, 51, 235.
46, 6891. b) V. J. Olsson, K. J. Szabó, Org. Lett. 2008, 10, 3129.
c) V. J. Olsson, K. J. Szabó, J. Org. Chem. 2009, 74, 7715.
8
a) M. Murata, K. Kawakita, T. Asana, S. Watanabe, Y.
Masuda, Bull. Chem. Soc. Jpn. 2002, 75, 825. b) A. Caballero, S.
Sabo-Etienne, Organometallics 2007, 26, 1191. c) B. Marciniec,
M. Jankowska, C. Pietraszuk, Chem. Commun. 2005, 663.
Stoichiometric reaction was reported. See: d) R. T. Baker, J. C.
Calabrese, S. A. Westcott, T. B. Marder, J. Am. Chem. Soc. 1995,
117, 8777.
9
D. E. Kadlecek, P. J. Carroll, L. G. Sneddon, J. Am. Chem.
Soc. 2000, 122, 10868.
10 T. Davan, E. W. Corcoran, Jr., L. G. Sneddon, Organo-
metallics 1983, 2, 1693.
11 a) D. H. Motry, M. R. Smith, III, J. Am. Chem. Soc. 1995,
117, 6615. b) D. H. Motry, A. G. Brazil, M. R. Smith, III, J. Am.
Chem. Soc. 1997, 119, 2743.
29 M.-A. Hiebel, B. Pelotier, O. Piva, Tetrahedron 2007, 63,

N. Kirai et al.
Bull. Chem. Soc. Jpn. Vol. 86, No. 7 (2013)
799
7874.
37 K. Itami, K. Tonogaki, Y. Ohashi, J.-i. Yoshida, Org. Lett.
2004, 6, 4093.
38 H. R. Kim, I. G. Jung, K. Yoo, K. Jang, E. S. Lee, J. Yun,
S. U. Son, Chem. Commun. 2010, 46, 758.
39 C. Wang, T. Tobrman, Z. Xu, E.-i. Negishi, Org. Lett. 2009,
11, 4092.
30 J. S. Denis, J. P. Oliver, T. W. Dolzine, J. B. Smart,
J. Organomet. Chem. 1974, 71, 315.
31 R. J. Ely, J. P. Morken, Org. Lett. 2010, 12, 4348.
32 J. A. Barltrop, H. A. J. Carless, J. Am. Chem. Soc. 1971, 93,
4794.
33 K.-L. Yeh, B. Liu, C.-Y. Lo, H.-L. Huang, R.-S. Lin, J. Am.
Chem. Soc. 2002, 124, 6510.
40 T. Ohmura, Y. Yamamoto, N. Miyaura, J. Am. Chem. Soc.
2000, 122, 4990.
34 L.-X. Shao, M. Shi, Org. Biomol. Chem. 2005, 3, 1828.
35 H. Lebel, D. Guay, V. Paquet, K. Huard, Org. Lett. 2004, 6,
3047.
41 J. Takagi, K. Takahashi, T. Ishiyama, N. Miyaura, J. Am.
Chem. Soc. 2002, 124, 8001.
42 R. J. Moody, D. S. Matteson, J. Organomet. Chem. 1978,
152, 265.
36 C. Morrill, R. H. Grubbs, J. Org. Chem. 2003, 68, 6031.