One-pot carboboration of alkynes using lithium borylcyanocuprate and the subsequent Suzuki-Miyaura cross-coupling of the resulting tetrasubstituted alkenylborane

Article abstract of DOI:10.1002/ejoc.201100373

We have developed a one-pot carboboration of internal alkynes using lithium borylcyanocuprates 3. Isolation of single crystals of 3·(thf) ₃ enabled us to estimate its structural and spectroscopic features. Simple mixing of 3 with ester-substituted alkynes and alkynylarenes was followed by trapping of the resulting intermediate with electrophiles to give tetrasubstituted borylalkenes 4, 5, and 8 in moderate to good yields. Ligand exchange of 8ba from diamine to pinacol allowed us to explore further application of obtained pinacol ester 10ba to subsequent Suzuki-Miyaura cross-coupling reactions to give all-carbon substituted alkene 9ba. Copyright

Full text of DOI:10.1002/ejoc.201100373

FULL PAPER
DOI: 10.1002/ejoc.201100373
One-Pot Carboboration of Alkynes Using Lithium Borylcyanocuprate and the
Subsequent Suzuki–Miyaura Cross-Coupling of the Resulting Tetrasubstituted
Alkenylborane
Yuri Okuno,[a] Makoto Yamashita,*[a] and Kyoko Nozaki*[a]
Keywords: Boron / Copper / Cuprates / Alkenes / Cross-coupling / Alkynes
We have developed a one-pot carboboration of internal al-
kynes using lithium borylcyanocuprates 3. Isolation of single
crystals of 3·(thf)3 enabled us to estimate its structural and
spectroscopic features. Simple mixing of 3 with ester-substi-
tuted alkynes and alkynylarenes was followed by trapping
of the resulting intermediate with electrophiles to give tetra-
substituted borylalkenes 4, 5, and 8 in moderate to good
yields. Ligand exchange of 8ba from diamine to pinacol al-
lowed us to explore further application of obtained pinacol
ester 10ba to subsequent Suzuki–Miyaura cross-coupling re-
actions to give all-carbon substituted alkene 9ba.
ylborated, and stannylborated alkenes require further acti-
vation for subsequent reactions. On the other hand, we re-
cently reported the one-pot carboboration of ynoate by ad-
dition of lithium borylcyanocuprate [3a·(thf)3], generated
from an anionic boron nucleophile, boryllithium (2a),[14]
and copper cyanide [Equation (1)].[15] This reaction con-
tains carbon electrophiles in contrast to the previously re-
ported carboboration that involves a nucleophilic carbon
reagent.[6–8] Herein, we report further exploration of the
carboboration of alkynes using lithium borylcyanocuprate
3a and carbon electrophiles and a crystal structure of new
lithium borylcyanocuprate 3b having a C–C saturated bond
in the boron-containing five-membered ring; the carbobor-
ation of arylalkynes using 3b and subsequent Suzuki–
Miyaura cross-coupling using the obtained tetrasubstituted
alkenylborane are also reported.
Introduction
Organoboron compounds are very useful reagents in syn-
thetic chemistry.[1] Among them, organoboronic acid deriv-
atives are one of the most important synthons for organic
synthesis[2] because they react with carbon- or heteroatom-
containing substrates to form new C–C or C–heteroatom
bonds in the presence of transition metal catalysts. Recently,
various organoboronic acid derivatives have become com-
mercially available from chemical companies. In contrast to
arylboronic acids, the number of alkenylboronic acid deriv-
atives, especially tetrasubstituted ones, is much lower owing
to the limited number of strategies used to prepare these
useful compounds. For the syntheses of tetrasubstituted
boronic acid derivatives, several strategies have been devel-
oped: (i) 1,2-Addition of boron-containing reagents, such as
diborane(4),[3] silylborane,[4] stannylborane,[5] cyanobor-
ane,[6] and alkynylborane[7] to alkynes. (ii) Transmetalative
carboboration of alkynes by using chloroborane and
organometallic reagents.[8] (iii) 1,1-Geminal diboration or
silaboration of 1,1-geminal dihaloalkenes[9] or 1,1-geminal
dihalocyclopropane followed by Rh-catalyzed rearrange-
ment.[10] (iv) Borodesilylation of tetrasubstituted alkenylsil-
anes.[11] (v) Metal-catalyzed carbozinconation of alkynyl-
boronic esters.[12] (vi) Addition of diborylmethide to
ketones.[13] Among them, “carboboration” reactions[6–8]
can be considered as the most reasonable method to synthe-
size tetrasubstituted borylalkenes because the diborated, sil-
(1)
[a] Department of Chemistry and Biotechnology,
Graduate School of Engineering, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, 113-8656, Tokyo, Japan
Fax: +81-3-5841-7262
Results and Discussion
Lithium borylcyanocuprate 3a generated in situ reacted
with ethyl 2-butynoate and diethyl acetylenedicarboxylate
(DEAD) followed by reaction with three electrophiles (eth-
anol, allyl bromide, and benzyl chloride; Table 1) to trap the
E-mail: makotoy@chembio.t.u-tokyo.ac.jp
nozaki@chembio.t.u-tokyo.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201100373.
Eur. J. Org. Chem. 2011, 3951–3958
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Y. Okuno, M. Yamashita, K. Nozaki
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possible intermediate β-borylalkenylcuprate. Reaction with ture (Table 1, Entries 2, 4, 5, 7, and 9), the major syn adduct
ethyl 2-butynoate followed by trapping with ethanol at is directly formed from syn-6. Isomerization from syn-6 to
room temperature afforded β-borylated product 4aa as a anti-6 may proceed through lithium allenolate intermediate
syn/anti mixture with a ratio of 81:19 (Table 1, Entry 1). 7. Allenolate 7 was directly observed by NMR spec-
The regioselectivity for β-borylation could be explained as troscopy, and it was suggested to have intramolecular al-
conjugate addition of a boron nucleophile. Lowering the kene coordination to copper.[17] Steric repulsion between
temperature did not have a significant influence on the yield the bulky boryl group and the cyanocuprate moiety would
or syn/anti stereoselectivity (Table 1, Entry 2). In the case lead to isomerization at room temperature to give a higher
of trapping with allyl bromide at room temperature, syn- yield of the anti isomers. Direct comparison between En-
4ab was obtained as a major product (Table 1, Entry 3). tries 3 and 6 (Table 1) suggests isomerization through the
Lowering temperature with allyl bromide improved the syn allenolate intermediate may be faster for the case with more
selectivity, but a slight decrease in the chemical yield for electron-poor DEAD compared to the case with ethyl 2-
4ab was observed (Table 1, Entry 4). The data previously butynoate. The difference in reaction rate probably comes
reported in our communication are cited for comparison in from the difference in the strength of π-backdonation from
Entries 6–9 (Table 1). Reaction of DEAD followed by trap- copper to the allenic double bond in allenolate intermediate
ping with ethanol afforded a mixture of hydroborated prod- 7.
ucts syn-/anti-5aa with a ratio of 70:30 (Table 1, Entry 5),
which is similar to the case of ethyl 2-butynoate. Trapping
with allyl bromide at room temperature gave anti-5ab as a
major product in contrast to the case of ethyl 2-butynoate
(Table 1, Entry 6). Lowering the temperature again gave
syn-5ab as a dominant product (Table 1, Entry 7). Trapping
with benzoyl chloride at room temperature afforded anti-
5ac as a major product with a syn/anti ratio of 1:Ͼ99
(Table 1, Entry 8). The remarkably high selectivity may
come from steric repulsion between a bulky boryl group
and benzoyl chloride. Reaction at –78 °C did not give any
carboborated product; instead, hydroborated isomeric mix-
ture 5aa was obtained. This result is slightly different in the
syn/anti selectivity from Entry 5 (Table 1) probably due to
the presence of benzoyl chloride.
Scheme 1. Possible mechanism for the formation of the syn and
anti adducts.
As we previously reported[14e] that saturation of the C–C
bond in the boron-containing five-membered ring would
lead to a higher Lewis acidity on the boron center due to
lack of aromaticity. Therefore, we also tried to use borylcya-
nocuprate 3b possessing a C–C single bond in the ring
backbone (vide infra for further conversion of the boryl
substituent). Boryllithium 2b was treated with CuCN·2LiCl
to give the corresponding lithium borylcyanocuprate 3b in
60% isolated yield as single crystals (Scheme 2). X-ray crys-
tallographic analysis revealed a linear structure of 3b·(thf)3
with co-solvation of three thf molecules to the lithium cat-
ion (Figure 1). All the obtained structural parameters are
similar to those of previously characterized 3a·(thf)3 in
which the C–C bond is unsaturated. The 1H and 13C NMR
spectra of isolated 3b indicate its solution structure has D2d
symmetry. The 11B NMR spectra showed a broad singlet
resonance at δB = 45.4 ppm, which is close to those of other
borylcopper species.[14b,14d,16] The negative mode of the
Table 1. Sequential reaction of 3a with ynoate and an electrophile.
Entry
R
T
[°C]
Electrophile Product Isolated
yield [%]
syn/anti
1
2
3
4
Me
Me
Me
r.t.
–78
r.t.
–78
–78
r.t.
–78
r.t.
–78
EtOH
EtOH
allylBr
allylBr
EtOH
allylBr
allylBr
PhCOCl
PhCOCl
4aa
4aa
4ab
4ab
5aa
5ab
5ab
5ac
5aa
83
85
90
73
82
96
93
71
80
81:19
82:18
79:21
Ͼ99:1
70:30
38:62
Ͼ99:1
1:Ͼ99
60:40
Me
5
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
6[a]
7[a]
8[a]
9[a]
[a] Data taken from ref.[15]
A possible mechanism for the carboboration of ynoates
is illustrated in Scheme 1. Lithium borylcyanocuprate 3a re-
acts with the ynoate to form syn-6 as an initial intermediate
through syn-borylcupration. In the reaction at low tempera- Scheme 2. Synthesis of lithium borylcyanocuprate 3b.
3952 Eur. J. Org. Chem. 2011, 3951–3958
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Suzuki–Miyaura Cross-Coupling of Tetrasubstituted Alkenylboranes
ESI-TOF mass spectrum of 3b showed a strong signal cor- Table 2. Carboboration of 1-arylalkyne derivatives with borylcya-
nocuprates 3a,b and allyl bromide.
responding to an aggregated dinuclear species [2(3b–
Li·3THF)–CN–]–.
Entry
R
RЈ
Product
Yield [%]
1[a]
2
3
4
5
6
7
8
9
Me
Me
Et
tBu
Me
Me
Me
Me
Me
H
H
H
8aa
8ba
8bb
–
8bc
8bd
8be
8bf
8bg
84
90
90
0
66
50
84
76
73
H
CN
CF3
Me
OMe
NMe2
[a] Reaction time was 4+5 h.
Figure 1. ORTEP drawing of 3b·(thf)3 (50% thermal ellipsoids, hy-
drogen atoms and minor parts of disordered thf molecules and iso-
propyl groups are omitted for clarity); selected bond lengths [Å]
and angles [°]: B1–Cu1 1.997(5), B1–N1 1.452(6), B1–N2 1.445(6),
Cu1–C3 1.902(5), C3–N3 1.164(6), N3–Li1 1.974(9), Li1–O 1.913
(av.), N1–B1–N2 103.7(4), B1–Cu1–C3 176.8(2), Cu1–C3–N3
179.0(5), C3–N3–Li1 172.0(5).
Tetrasubstituted alkenylboranes 8aa and 8ba were ap-
plied to Suzuki–Miyaura cross-coupling reactions
(Scheme 3). In the presence of Pd(PtBu3)2 and KOH aq.,
neither alkenylborane 8aa nor 8ba reacted with p-iodonitro-
benzene to give coupled product 9. The bulkiness of the
Dip groups or effective π-donation of the nitrogen atoms
may suppress the transmetalation of the boryl group to pal-
ladium. Therefore, the bulky Dip-substituted diamino
group in 8aa and 8ba was converted into a pinacolate group
in 10, and this substrate was subjected to the cross-coupling
reaction as follows. According to the previously reported
conditions for the deprotection of the diamino substituents
on the boron center,[6b] 8aa and 8ba were treated with pina-
col and p-toluenesulfonic acid monohydrate in thf at 40 °C
to give tetrasubstituted alkenylboronic acid pinacol ester
10. Using 8ba having a C–C single bond in the boron-con-
taining five-membered ring gave a better yield of 10 (65%)
despite of shorter reaction time of 5 h, compared to the
case of 8aa (20 h, 23%). In the presence of a palladium
1-Arylalkynes were also subjected to the carboboration
reaction using lithium borylcyanocuprates 3a,b and allyl
bromide. In the reaction of 3a with 1-phenylpropyne, car-
boborated product 8aa was obtained in 84% yield (Table 2,
Entry 1). Saturation of the C–C bond in the boron-contain-
ing five-membered ring gave a slightly better yield of 8ba
(90%; Table 2, Entry 2), indicating that 3a and 3b have sim-
ilar reactivity for the carboboration of arylalkynes. Selective
formation of the β-borylated product in both cases could
be explained by the electron-withdrawing nature of the aryl
group. Furthermore, syn selectivity, confirmed by X-ray
crystallography (for 8aa, 8bb, and 8bg, see Supporting In-
formation), of the addition was also explained by a lack
of a strong electron-withdrawing group such as a carbonyl
substituent to induce the isomerization of the alkenylcupr-
ate intermediate. Changing the methyl substituent to an
ethyl substituent did not hamper the reaction to give 8bb
(Table 2, Entry 3). However, introduction of a bulky tert-
butyl group completely suppressed the reaction (Table 2,
Entry 4). On the contrary, the electronic effect of the aryl
ring slightly affected the chemical yield (Table 2, Entries 5–
9). Introduction of an electron-withdrawing substituent
such as nitrile and trifluoromethyl groups on the benzene
ring lowered the chemical yield of carboborated products
8bc and 8bd (Table 2, Entries 5 and 6). Using a 1-arylalkene
substituted with an electron-donating group resulted in
slightly higher yields of 8be–8bg (Table 2, Entries 7–9). Al-
though the reason for the electronic effect is not clear so
far, electron-donating substituents may enhance the reactiv-
ity of the borylated alkenylcuprate intermediate to facilitate
its reaction with allyl bromide.
Scheme 3. Ligand exchange of 8ba and subsequent Suzuki–
Miyaura cross-coupling reaction.
Eur. J. Org. Chem. 2011, 3951–3958
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3953

Y. Okuno, M. Yamashita, K. Nozaki
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1.03 mmol). To the cooled mixture at –35 °C, precooled thf
(10.0 mL, –35 °C) was added. The mixture was stirred at –35 °C
for 12 h. After the solution of 2a was quickly filtered through a
pad of Celite at room temperature, a solution of CuCN (448 mg,
5.00 mmol) and LiCl (425 mg, 10.0 mmol) in thf (7.00 mL) was
added to the filtrate at –35 °C. The resulting mixture was stirred at
–35 °C for 1 h, and then the solution was diluted to 25 mL with
Na/K-dried thf using a volumetric flask to give a 0.200 m solution
of borylcyanocuprate 3a.
catalyst, 10 was successfully coupled with p-iodonitroben-
zene to form tetrasubstituted alkene 9 possessing four dif-
ferent carbon substituents in 88% yield.[18,19]
Conclusions
In this paper, we reported the one-pot carboboration of
alkynes by their reaction with lithium borylcyanocuprate
followed by addition of an electrophile. New borylcopper
species, lithium borylcyanocuprates 3a,b, were synthesized
and structurally characterized to show a linear arrangement
of the boryl group, copper atom, cyanide, and lithium
atom. It could react with ynoates or 1-arylalkynes to gener-
ate the borylalkenylcuprate. Trapping of this intermediate
with electrophiles afforded the corresponding alkenylbor-
General Procedure for the Borylcupration of Ethyl 2-Butynoate and
Sequential Reaction with Electrophile (Table 1): In a glove box, a
20-mL Schlenk flask equipped with a glass-coated stir bar was
charged with a 0.200 m thf solution of 3a (1.00 mL, 0.200 mmol).
After the Schlenk flask was removed from the glove box, the
Schlenk flask was cooled to –78 °C or kept at room temperature. To
the reaction mixture was added a thf solution of ethyl 2-butynoate
(1.00 m, 150 μL, 0.150 mmol) at –78 °C or at room temperature,
ane product. The regio- and stereochemistry and chemical and the resulting mixture was stirred at –78 °C or room tempera-
ture for 3 h. Then a thf solution of allyl bromide (0.225 m, 1.00 mL,
0.225 mmol) was added to the mixture at –78 °C or room tempera-
ture and stirred for 5 h. At the same temperature, EtOH (100 μL,
1.71 mmol) was added to the reaction mixture. All volatiles were
removed under reduced pressure, and hexane was added to the mix-
ture. The crude product was purified by recycling preparative
HPLC.
yields of the product were varied by substrate, reaction tem-
perature, and electrophile. By exchanging the diamino sub-
stituents on the resulting borylated alkene to give an alken-
ylboronic pinacol ester, this substrate could be utilized in
Suzuki–Miyaura cross-coupling reactions to give tetrasub-
stituted alkenes with four different carbon substituents.
This reaction sequence would enhance the usefulness of
borylcopper species for organic synthesis.
anti-4aa: Yield: 17% (14.5 mg, 29.0 μmol). Pale yellow oil. 1H
NMR (500 MHz, CDCl3): δ = 1.17 (d, J = 7 Hz, 3 H), 1.18 (d, J
= 6 Hz, 12 H), 1.19 (d, J = 6 Hz, 12 H), 1.66 (d, J = 1 Hz, 3 H),
3.30 (sept., J = 6 Hz, 4 H), 4.03 (q, J = 7 Hz, 2 H), 5.87 (d, J =
1 Hz, 1 H), 6.23 (s, 2 H), 7.18 (d, J = 8 Hz, 4 H), 7.28 (d, J = 8 Hz,
2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 14.4 (CH3), 23.3
(CH3), 24.9 (CH3), 26.6 (CH3), 27.9 (CH), 59.3 (CH2), 119.8 (CH),
123.4 (CH), 127.1 (CH), 129.0 (CH), 138.7 (Cq), 146.8 (Cq), 154.1
(br. s, B-C), 165.5 (Cq) ppm. HRMS (ESI-TOF): calcd. for
C32H45BN2O2Na [4aa + Na] 523.3477, 524.3507; found 523.3456,
524.3482.
Experimental Section
General: All manipulations were carried out by using standard
Schlenk techniques under an atmosphere of argon purified by pass-
ing through a hot column packed with BASF catalyst R3–11 or in
an argon-filled glove box (Miwa MFG). Low-temperature reac-
tions at –35 °C performed in the glove box were performed by using
refrigeration. Purification with GPC was performed by LC-928 re-
cycling preparative HPLC (JAI), equipped with JAI GEL 1H-2H
column and eluted with CHCl3. The 1H, 7Li{1H}, 13C, and
11B{1H} NMR spectra were recorded with 500 MHz spectrometers.
Chemical shifts are reported in ppm relative to residual protonated
solvent for 1H, deuterated solvent for 13C, external LiBr in D2O
syn-4aa: Yield: 73% (48.3 mg, 96.5 μmol). Pale yellow oil. 1H
NMR (500 MHz, CDCl3): δ = 1.10 (t, J = 7 Hz, 3 H), 1.17 (d, J =
7 Hz, 12 H), 1.19 (d, J = 7 Hz, 12 H), 1.71 (d, J = 2 Hz, 3 H), 2.98
(sept., J = 7 Hz, 4 H), 3.94 (q, J = 7 Hz, 2 H), 5.52 (d, J = 2 Hz,
1 H), 6.20 (s, 2 H), 7.21 (d, J = 8 Hz, 4 H), 7.32 (t, J = 8 Hz, 2 H)
ppm. 13C NMR (125 MHz, CDCl3): δ = 14.3 (CH3), 17.7 (CH3),
23.4 (CH3), 25.3 (CH3), 28.5 (CH), 59.3 (CH2), 120.1 (CH), 123.7
(CH), 127.0 (CH), 127.6 (CH), 138.9 (Cq), 145.7 (Cq), 151.0 (br. s,
B-C), 166.5 (Cq) ppm. 11B NMR (160 MHz, CDCl3): δ = 24.3 (br.
s) ppm. HRMS (ESI-TOF): calcd. for C32H45BN2O2Na [4aa + Na]
523.3477, 524.3507; found 523.3454, 524.3483.
7
for Li, and external BF3·OEt2 for 11B nuclei used as a reference.
High-resolution mass spectrometry (ESI-TOF, thf or MeOH solu-
tion) was measured with a JEOL AccuTOF JMS-T100LP instru-
ment with calibration by using PEG or YOKUDELNA (JEOL) as
an external reference. Hexane and thf were purified by passing
through a solvent purification system (Grass Contour). Melting
points were measured with a MPA100 Optimelt automated melting
point system. For dilution of a boryllithium solution, thf was fur-
ther dried with Na/K alloy and then filtered through a pad of silica
gel prior to use. [D6]Benzene was vacuum distilled from sodium/
benzophenone. Lithium dispersion (Kanto Chemical) was washed
with hexane to make a lithium powder containing 1% of sodium.
Naphthalene was used as received. Bromoboranes 1a,b were syn-
thesized according to literature procedures.[14a,14e] 1-Arylalkynes
were synthesized by using a literature procedure[20] and their NMR
spectra were identical to those of the previously reported com-
pounds.[21]
anti-4aa: Yield: 15% (13.2 mg, 26.4 μmol).
syn-4aa: Yield: 70% (52.8 mg, 0.105 mmol).
anti-4ab: Yield: 17% (14.0 mg, 25.9 μmol). Pale yellow oil. 1H
NMR (500 MHz, CDCl3): δ = 1.146 (t, J = 7 Hz, 3 H), 1.148 (d,
J = 7 Hz, 24 H), 1.55 (s, 3 H), 2.90 (d, J = 6 Hz, 2 H), 3.06–3.54
(br., 4 H), 3.99 (q, J = 7 Hz, 2 H), 4.49 (dd, J = 17, 2 Hz, 1 H),
4.67 (dd, J = 10, 2 Hz, 1 H), 5.51 (ddt, J = 17, 10, 6 Hz, 1 H), 6.17
(s, 2 H), 7.13 (d, J = 8 Hz, 4 H), 7.23 (t, J = 8 Hz, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 14.3 (CH3), 19.5 (CH3), 23.3 (CH3),
26.6 (CH3), 27.8 (CH), 32.5 (CH2), 59.9 (CH2), 114.5 (CH2), 119.4
(CH), 123.4 (CH), 126.9 (CH), 134.9 (Cq), 136.0 (CH), 139.1 (Cq),
146.8 (Cq), 166.6 (Cq) ppm. HRMS (ESI-TOF): calcd. for
C35H49BN2O2Na [4ab + Na] 563.3791, 564.3821; found 563.3769,
564.3796.
Preparation of a Stock Solution of Lithium Borylcyanocuprate 3a:
In a glove box, a 20-mL vial equipped with a glass-coated stir bar
was charged with bromoborane 1a (2.35 g, 5.02 mmol), lithium
powder (176 mg, 25.4 mmol), and naphthalene (132 mg,
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Suzuki–Miyaura Cross-Coupling of Tetrasubstituted Alkenylboranes
1
syn-4ab: Yield: 73% (58.7 mg, 0.109 mmol). Yellow oil. H NMR and DMSO (6.0 mL) was stirred at 110 °C for 2 h. The reaction
(500 MHz, CDCl3): δ = 1.12 (t, J = 7 Hz, 3 H), 1.19 (d, J = 7 Hz,
12 H), 1.22 (d, J = 7 Hz, 12 H), 1.52 (s, 3 H), 2.69 (d, J = 6 Hz, 2 with CH2Cl2 (2ϫ20 mL). The combined CH2Cl2 extracts were
H), 3.07 (sept., J = 7 Hz, 4 H), 4.00 (q, J = 7 Hz, 2 H), 4.48 (ddt, washed with H2O, dried with Na2SO4, and filtered. The solvent
J = 17, 10, 6 Hz, 1 H), 4.66 (dd, J = 10, 2 Hz, 1 H), 4.70 (dd, J = was removed under vacuum. Purification by silica-gel column
mixture was poured into sat. NH4Cl aq. (20 mL) and was extracted
17, 2 Hz, 1 H), 6.29 (s, 2 H), 7.21 (d, J = 8 Hz, 4 H), 7.29 (t, J =
chromatography (hexane/CH2Cl2, 3:1) afforded 4-propynylbenzoni-
8 Hz, 2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 14.3 (CH3),
trile as a colorless solid (350 mg, 2.48 mmol, 83%). 1H NMR
19.8 (CH3), 22.9 (CH3), 26.2 (CH3), 28.4 (CH), 39.4 (CH2), 59.7 (500 MHz, CDCl3): δ = 2.08 (s, 3 H), 7.45 (d, J = 8 Hz, 2 H), 7.56
(CH2), 116.4 (CH2), 119.8 (CH), 123.9 (CH), 127.1 (CH), 133.9
(br. s, B-C), 135.0 (CH), 138.7 (Cq), 145.4 (Cq), 169.3 (Cq) ppm.
11B NMR (160 MHz, CDCl3): δ = 25.5 (br. s) ppm. HRMS (ESI-
TOF): calcd. for C35H49BN2O2Na [4ab + Na] 563.3791, 564.3821;
found 563.3769, 564.3797.
(d, J = 8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 4.6
(CH3), 78.7 (Cq), 91.2 (Cq), 111.0 (Cq), 118.8 (CN), 129.2 (Cq),
132.1 (CH), 132.2 (CH) ppm.
4-Propynylbenzotrifluoride: A similar procedure for nitrile deriva-
tive was applied to the synthesis of the CF3 derivative here. Color-
syn-4ab: Yield: 73% (58.8 mg, 0.109 mmol). Yellow oil.
1
less oil (587 mg, 2.91 mmol, 58%). H NMR (500 MHz, CDCl3):
δ = 2.07 (s, 3 H), 7.47 (d, J = 8 Hz, 2 H), 7.53 (d, J = 8 Hz, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 4.4, 78.8, 88.9, 124.2 (q,
J = 272 Hz), 125.3 (q, J = 4 Hz), 128.1, 129.5 (q, J = 33 Hz),
131.9 ppm. 19F NMR (470 MHz, CDCl3): δ = –62.66 (s) ppm.
Isolation of Lithium Borylcyanocuprate 3b·(thf)3: In a glove box, a
20-mL vial equipped with a glass-coated stir bar was charged with
bromoborane 1b (470 mg, 1.00 mmol), lithium powder (35.3 mg,
5.09 mmol), and naphthalene (25.6 mg, 0.200 mmol). To the cooled
mixture at –35 °C, precooled thf (10.0 mL, –35 °C) was added. The
resulting mixture was stirred at –35 °C for 12 h. After the solution
was quickly filtered through a pad of Celite at room temperature,
a precooled –35 °C solution of CuCN (94.0 mg, 1.05 mmol) and
LiCl (93.3 mg, 2.20 mmol) in thf (1.0 mL) was added to the filtrate
at –35 °C. The reaction mixture was stirred at room temperature
for 1 h. All volatiles were removed under reduced pressure, and
hexane was added to the mixture. The added hexane was again
evaporated to remove thf completely. The residue was extracted
with hexane, and the resulting suspension was filtered through a
pad of Celite to remove the inorganic salts. The crude product was
recrystallized (hexane/thf, 30:1) at –35 °C to give colorless crystals
(421 mg, 0.600 mmol, 60%) of 3b·(thf)3. M.p. 142.1–144.9 °C (de-
comp.). 1H NMR (500 MHz, C6D6): δ = 1.32–1.35 (m, 24 H), 1.45
(d, J = 7 Hz, 12 H), 3.36 (t, J = 7 Hz, 12 H), 3.67 (sept., J = 7 Hz,
4 H), 6.45 (s, 2 H), 7.20 (s, 6 H) ppm. 13C NMR (100 MHz, C6D6):
δ = 24.4 (CH3), 25.5 (CH2), 26.2 (CH3), 28.5 (thf, CH2), 55.1
(CH2), 68.1 (thf, CH2), 123.3 (CH), 125.4 (CH), 146.0 (Cq), 148.4
(Cq), 157.3 (CN) ppm. 11B NMR (160 MHz, C6D6): δ = 45.4 (br.
s) ppm. 7Li NMR (194 MHz, C6D6): δ = –1.34 (s) ppm. IR
4-Propynyltoluene:
A
mixture of Pd(PPh3)2Cl2 (176 mg,
0.250 mmol),
1,4-bis(diphenylphosphanyl)butane (214 mg,
0.501 mmol), 4-iodotoluene (720 μL, 5.54 mmol), 2-butynoic acid
(562 mg, 5.01 mmol), DBU (2.30 mL, 15.4 mmol), and DMSO
(5.0 mL) was stirred at 80 °C for 12 h. The reaction was poured
into sat. NH4Cl aq. (20 mL) and extracted with CH2Cl2
(2ϫ20 mL). The combined CH2Cl2 extracts were washed with
H2O, dried with Na2SO4, and filtered. The solvent was removed
under vacuum. Purification by silica gel column chromatography
(hexane) afforded 4-propynyltoluene as a yellow oil (610 mg,
1
4.68 mmol, 93%) H NMR (500 MHz, CDCl3): δ = 2.05 (s, 3 H),
2.34 (s, 3 H), 7.09 (d, J = 8 Hz, 2 H), 7.29 (d, J = 8 Hz, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 4.4 (CH3), 21.5 (CH3), 79.9 (Cq),
85.1 (Cq), 121.1 (Cq), 129.1 (CH), 131.5 (CH), 137.6 (Cq) ppm.
4-Propynylanisole:
A
mixture of Pd(PPh3)2Cl2 (176 mg,
0.250 mmol),
1,4-bis(diphenylphosphanyl)butane (215 mg,
0.503 mmol), 4-bromoanisole (700 μL, 5.59 mmol), 2-butynoic acid
(562 mg, 5.00 mmol), DBU (2.30 mL, 15.4 mmol), and DMSO
(5.0 mL) was stirred at 80 °C for 12 h. The reaction mixture was
poured into sat. NH4Cl aq. (20 mL) and extracted with CH2Cl2
(2ϫ20 mL). The combined CH2Cl2 extracts were washed with
H2O, dried with Na2SO4, and filtered. The solvent was removed
under vacuum. Purification by silica gel column chromatography
(hexane) afforded 4-propynylanisole as a colorless oil (591 mg,
4.04 mol, 81%). 1H NMR (500 MHz, CDCl3): δ = 2.03 (s, 3 H),
3.79 (s, 3 H), 6.81 (d, J = 8 Hz, 2 H), 7.33 (d, J = 8 Hz, 2 H) ppm.
13C NMR (125 MHz, CDCl3): δ = 4.4 (CH3), 55.4 (CH3), 79.6 (Cq),
84.2 (Cq), 114.0 (CH), 116.3 (Cq), 132.9 (CH), 159.1 (Cq) ppm.
(KBr): ν = 2129 (CϵN) cm–1. HRMS (ESI-TOF): calcd. for
˜
C53H76B2Cu2N5 [2(3b–Li+)–CN–]– 930.4897, 933.4888; found
930.4797, 932.4854.
Preparation of a Stock Solution of Lithium Borylcyanocuprate 3b:
In a glove box, a 20-mL vial equipped with a glass-coated stir bar
was charged with bromoborane 1b (2.35 g, 5.02 mmol), lithium
powder (175 mg, 25.2 mmol), and naphthalene (128 mg,
1.00 mmol). To the cooled mixture at –35 °C was added precooled
thf (10.0 mL, –35 °C). The mixture was stirred at –35 °C for 12 h.
After the solution of 2b was quickly filtered through a pad of Celite
at room temperature, a solution of CuCN (450 mg, 5.03 mmol) and
LiCl (430 mg, 10.2 mmol) in thf (7.00 mL) was added to the filtrate
at –35 °C. The resulting mixture was stirred at –35 °C for 1 h, and
then the solution was diluted to 25 mL with Na/K-dried thf using
a volumetric flask to give a 0.200 m solution of borylcyanocuprate
3b.
4-Propynyl-N,N-dimethylaniline:
A
mixture of Pd(PPh3)2Cl2
(175 mg, 0.250 mmol), 1,4-bis(diphenylphosphanyl)butane
(214 mg, 0.503 mmol), 4-bromo-N,N-dimethylaniline (1.05 g,
5.26 mmol), 2-butynoic acid (566 mg, 5.04 mmol), DBU (2.30 mL,
15.4 mmol), and DMSO (5.0 mL) was stirred at 80 °C for 36 h.
The reaction mixture was poured into sat. NH4Cl aq. (20 mL) and
extracted with CH2Cl2 (2ϫ20 mL). The combined CH2Cl2 extracts
were washed with H2O, dried with Na2SO4, and filtered. The sol-
vent was removed under vacuum. Purification by silica gel column
chromatography (hexane/CH2Cl2, 7:1) afforded 4-propynyl-N,N-di-
methylaniline as a colorless solid (346 mg, 2.17 mmol, 43%). 1H
NMR (500 MHz, CDCl3): δ = 2.03 (s, 3 H), 2.95 (s, 6 H), 6.62 (d,
J = 9 Hz, 2 H), 7.27 (d, J = 9 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 4.5 (CH3), 40.5 (CH3), 80.3 (Cq), 83.1 (Cq), 111.4 (Cq),
112.1 (CH), 132.6 (CH), 149.8 (Cq) ppm.
Syntheses of 1-Arylalkyne Derivatives: The following 1-arylalkynes
were synthesized according to the literature procedure.[20] The
NMR spectra of these compounds were identical to those of known
compounds.[21]
4-Propynylbenzonitrile:
34.3 μmol), 1,4-bis(diphenylphosphanyl)butane
A
mixture of Pd(PPh3)2Cl2 (24.1 mg,
(29.9 mg,
70.1 μmol), 4-bromobenzonitrile (554 mg, 3.04 mmol), 2-butynoic
acid (252 mg, 3.00 mmol), TBAF (1.0 m in thf, 6.0 mL, 6.0 mmol),
Eur. J. Org. Chem. 2011, 3951–3958
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3955

Y. Okuno, M. Yamashita, K. Nozaki
FULL PAPER
8aa: In a glove box, 2b (469 mg, 1.00 mmol), lithium (21.3 mg,
3.07 mmol), and naphthalene (25.6 mg, 0.200 mmol) were placed
in a 20-mL vial. To the mixture, precooled thf (3.0 mL, –35 °C)
was added. The resulting mixture was stirred at –35 °C for 12 h.
After the solution was quickly filtered through a pad of Celite at
room temperature, a precooled –35 °C solution of CuCN (89.5 mg,
1.00 mmol) and LiCl (91.0 mg, 2.15 mmol) in thf (1.0 mL) was
added to the filtrate at –35 °C. The reaction mixture was stirred at
room temperature for 1 h. To the mixture was added 1-phenylpro-
pyne (116 mg, 1.00 mmol) at room temperature. After the resulting
mixture was stirred for 3 h, allyl bromide (218 mg, 1.80 mmol) was
added, and then, the mixture was further stirred at room tempera-
ture for 5 h. Volatiles were removed under reduced pressure, and
the residue was extracted with hexane. The resulting suspension
was filtered through a pad of Celite, and the solvents were evapo-
rated under reduced pressure. The crude product was purified by
silica gel chromatography (hexane/CH2Cl2, 1:0.05 to 1:0.2) to give
a pale yellow solid of 8aa (456 mg, 0.844 mmol, 84%). M.p. 109.3–
111.8 °C. 1H NMR (500 MHz, C6D6): δ = 1.20 (d, J = 7 Hz, 12
H), 1.30 (d, J = 7 Hz, 12 H), 1.44 (s, 3 H), 3.00 (d, J = 7 Hz, 2 H),
3.36 (sept., J = 7 Hz, 4 H), 4.62 (dd, J = 11, 1 Hz, 2 H), 4.82 (ddt,
J = 17, 10, 2 Hz, 1 H), 6.33 (s, 2 H), 6.84 (dd, J = 8, 1 Hz, 2 H),
6.94 (t, J = 8 Hz, 1 H), 7.04 (t, J = 8 Hz, 2 H), 7.18 (m, 4 H), 7.23
(dd, J = 8, 6 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
19.5 (CH3), 22.9 (CH3), 26.0 (CH3), 28.3 (CH), 44.0 (CH2), 115.6
(CH2), 119.5 (CH), 123.6 (CH), 125.7 (CH), 126.9 (CH), 127.6
(CH), 128.4 (CH), 136.4 (CH), 139.3 (Cq), 142.6 (Cq), 145.5 (Cq),
146.5 (Cq) ppm. 11B NMR (160 MHz, C6D6): δ = 27 (br. s) ppm.
C38H49BN2 (544.62): calcd. C 83.66, H 9.32, N 4.99; found C 83.80,
H 9.07, N 5.14.
126.2 (CH), 127.5 (CH), 128.3 (CH), 136.5 (CH), 141.0 (Cq), 142.9
(Cq), 147.0 (Cq), 147.6 (Cq) ppm. 11B NMR (160 MHz, CDCl3): δ
= 32.1 (br. s) ppm. C39H53BN2 (560.66): calcd. C 83.55, H 9.53, N
5.00; found C 83.17, H 9.56, N 4.78.
8bc: Purified by silica gel column chromatography (hexane/CH2Cl,
3:1), colorless solid (56.6 mg, 0.099 mmol, 66%). M.p. 150.0–
1
151.0 °C. H NMR (500 MHz, CDCl3): δ = 1.07 (s, 3 H), 1.23 (d,
J = 7 Hz, 12 H), 1.29 (d, J = 7 Hz, 12 H), 2.79 (d, J = 4 Hz, 2 H),
3.45 (sept., J = 7 Hz, 4 H), 3.63 (s, 4 H), 4.40–4.46 (m, 2 H), 4.50–
4.55 (m, 1 H), 6.75 (d, J = 8 Hz, 2 H), 7.17 (d, J = 7 Hz, 4 H),
7.23 (dd, J = 8, 7 Hz, 2 H), 7.40 (d, J = 8 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.2 (CH3), 23.7 (CH3), 26.7 (CH3), 28.2
(CH), 43.5 (CH2), 53.6 (CH2), 109.7 (Cq), 116.5 (CH2), 119.2 (CN),
124.1 (CH), 126.4 (CH), 128.8 (br. s, B-C), 129.4 (CH), 131.6 (CH),
135.8 (CH), 140.2 (Cq), 144.6 (Cq), 146.9 (Cq), 148.0 (Cq) ppm. 11
B
NMR (160 MHz, CDCl3): δ = 31.4 (br. s) ppm. HRMS (ESI-TOF):
calcd. for C39H50BN3 [7c + H] 594.4002; found 594.4025.
8bd: Purified by silica gel column chromatography (hexane/CH2Cl,
3:1), colorless solid (46.1 mg, 0.075 mmol, 50%). M.p. 122.0–
1
123.1 °C. H NMR (500 MHz, CDCl3): δ = 1.07 (s, 3 H), 1.24 (d,
J = 7 Hz, 12 H), 1.29 (d, J = 7 Hz, 12 H), 2.80 (d, J = 3 Hz, 2 H),
3.47 (sept., J = 7 Hz, 4 H), 3.63 (s, 4 H), 4.42–4.54 (m, 3 H), 6.77
(d, J = 8 Hz, 2 H), 7.17 (d, J = 7 Hz, 4 H), 7.23 (dd, J = 8, 7 Hz,
2 H), 7.36 (d, J = 8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 19.3 (CH3), 23.8 (CH3), 26.8 (CH3), 28.2 (CH), 43.8 (CH2),
53.7 (CH2), 116.3 (CH2), 124.1 (CH), 124.4 (q, J = 532 Hz, CF3),
124.7 (q, J = 4 Hz, CH), 126.4 (CH), 128.1 (q, J = 64 Hz, Cq),
128.9 (CH), 136.1 (CH), 140.4 (Cq), 145.1 (Cq), 146.6 (Cq), 147.0
(Cq). 11B NMR (160 MHz, CDCl3): δ = 31.2 (br. s) ppm. 19F NMR
(470 MHz, CDCl3): δ = –63.32 (s) ppm. HRMS (ESI-TOF): calcd.
for C39H50BF3N2Na [7d + Na] 637.3924; found 637.3952.
General Procedure for the Borylcupration of 1-Arylalkynes and Se-
quential Reaction with Allyl Bromide (Table 2, Entries 2–9): In a
glove box, the alkyne (0.150 mmol) and a thf solution of 3b
(0.200 m, 1.00 mL, 0.200 mmol) were stirred in a 5-mL vial at room
temperature for 3 h. Then, a thf solution of allyl bromide (0.225 m,
1.00 mL, 0.225 mmol) was added into the solution, and the mixture
was stirred at room temperature for 5 h. The crude product was
purified by silica gel column chromatography or by recycling pre-
parative HPLC.
8be: Purified by silica gel column chromatography (hexane/CH2Cl,
3:1), colorless solid (70.6 mg, 0.126 mmol, 84%). M.p. 104.7–
1
106.0 °C. H NMR (500 MHz, CDCl3): δ = 1.10 (s, 3 H), 1.24 (d,
J = 7 Hz, 24 H), 1.29 (d, J = 7 Hz, 24 H), 2.21 (s, 3 H), 2.78 (d, J
= 5 Hz, 2 H), 3.48 (sept., J = 7 Hz, 4 H), 3.62 (s, 4 H), 4.46–4.58
(m, 3 H), 6.56 (d, J = 8 Hz, 2 H), 6.91 (d, J = 8 Hz, 2 H), 7.16 (d,
J = 7 Hz, 4 H), 7.21 (dd, J = 8, 7 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.3 (CH3), 21.2 (CH3), 23.8 (CH3), 26.8
(CH3), 28.2 (CH), 44.0 (CH2), 53.7 (CH2), 115.5 (CH2), 124.0
(CH), 126.2 (CH), 128.3 (CH), 135.1 (Cq), 136.9 (Cq), 139.7 (Cq),
140.6 (Cq), 146.3 (CH), 147.0 (Cq) ppm. 11B NMR (160 MHz,
CDCl3): δ = 31.3 (br. s) ppm. HRMS (ESI-TOF): calcd. for
C39H53BN2Na [7e + Na] 583.4206; found 583.4228.
8ba: Purified by recycling preparative HPLC, colorless solid
(73.8 mg, 0.135 mol, 90%). M.p. 120.5–122.9 °C. 1H NMR
(500 MHz, CDCl3): δ = 1.20 (s, 3 H), 1.36 (dd, J = 19, 7 Hz, 24
H), 2.90 (d, J = 5 Hz, 2 H), 3.56–3.61 (m, 4 H), 3.72 (s, 4 H), 4.54–
4.68 (m, 3 H), 6.76 (d, J = 7 Hz, 2 H), 7.10 (t, J = 7 Hz, 1 H), 7.18
(t, J = 7 Hz, 2 H), 7.25 (d, J = 7 Hz, 4 H), 7.30 (dd, J = 9, 6 Hz,
2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 19.2 (CH3), 23.8
(CH3), 26.8 (CH3), 28.2 (CH), 44.0 (CH2), 53.7 (CH2), 115.6 (CH2),
124.0 (CH), 125.8 (CH), 126.2 (CH), 126.9 (br. s, B-C), 127.6 (CH),
128.5 (CH), 136.7 (CH), 140.5 (Cq), 142.7 (Cq), 146.4 (Cq), 147.0
(Cq) ppm. 11B NMR (160 MHz, CDCl3): δ = 32.2 (br. s) ppm.
C38H51BN2 (546.64): calcd. C 83.49, H 9.40, N 5.12; found C 83.35,
H 9.42, N 4.94.
8bf: Purified by silica gel column chromatography (hexane/CH2Cl,
3:1), colorless solid (65.7 mg, 0.114 mmol, 76%). M.p. 97.0–
1
100.7 °C. H NMR (500 MHz, CDCl3): δ = 1.11 (s, 3 H), 1.25 (d,
J = 7 Hz, 11 H), 1.30 (d, J = 7 Hz, 12 H), 2.79 (d, J = 4 Hz, 2 H),
3.49 (sept., J = 7 Hz, 4 H), 3.63 (s, 4 H), 3.70 (s, 3 H), 4.45–4.59
(m, 3 H), 6.61 (d, J = 9 Hz, 2 H), 6.67 (d, J = 9 Hz, 2 H), 7.17 (m,
4 H), 7.22 (dd, J = 8, 7 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 19.2 (CH3), 23.8 (CH3), 26.8 (CH3), 28.2 (CH), 44.1
(CH2), 53.7 (CH2), 55.1 (CH), 113.0 (CH), 115.5 (CH2), 124.0
(CH), 126.2 (CH), 127.0 (br. s, B-C), 129.5 (CH), 135.0 (Cq), 136.9
(CH), 140.6 (Cq), 145.9 (Cq), 147.0 (Cq), 157.6 (Cq) ppm. 11B NMR
(160 MHz, CDCl3): δ = 31.6 (br. s) ppm. HRMS (ESI-TOF): calcd.
for C39H53BN2NaO [7f + Na] 599.4155; found 599.4157.
8bb: Purified by silica gel column chromatography (hexane/CH2Cl,
4:1), colorless solid (75.7 mg, 0.135 mol, 90%). M.p. 131.7–
133.8 °C. 1H NMR (500 MHz, CDCl3): δ = 0.12 (t, J = 7 Hz, 3 H),
1.29 (d, J = 7 Hz, 24 H), 1.55 (s, 2 H), 1.67 (q, J = 7 Hz, 2 H),
2.82 (d, J = 7 Hz, 2 H), 3.54 (sept., J = 7 Hz, 4 H), 3.63 (s, 4 H),
4.13–4.22 (m, 1 H), 4.31 (dt, J = 17, 1 Hz, 1 H), 4.38 (dd, J = 10,
2 Hz, 1 H), 6.74–6.74 (m, 2 H), 7.04 (t, J = 7 Hz, 1 H), 7.11 (t, J
8bg: Purified by silica gel column chromatography (hexane/CH2Cl2,
3:1), colorless solid (64.6 mg, 0.110 mmol, 73%). M.p. 157.9.0–
= 7 Hz, 2 H), 7.15–7.21 (m, 6 H) ppm. 13C NMR (126 MHz, 162.9 °C. H NMR (500 MHz, CDCl3): δ = 1.14 (s, 3 H), 1.24 (d,
CDCl3): δ = 13.7 (CH3), 23.7 (CH3), 25.4 (CH3), 26.9 (CH3), 28.2 J = 7 Hz, 12 H), 1.28 (d, J = 7 Hz, 12 H), 2.79 (d, J = 5 Hz, 2 H),
(CH), 44.9 (CH2), 53.7 (CH2), 115.7 (CH), 124.1 (CH), 125.8 (CH), 2.83 (s, 6 H), 3.48 (sept., J = 7 Hz, 4 H), 3.61 (s, 4 H), 4.48–4.62
1
3956
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 3951–3958

Suzuki–Miyaura Cross-Coupling of Tetrasubstituted Alkenylboranes
(m, 3 H), 6.51 (d, J = 9 Hz, 2 H), 6.59 (d, J = 9 Hz, 2 H), 7.15– Supporting Information (see footnote on the first page of this arti-
7.16 (m, 4 H), 7.21 (dd, J = 8, 7 Hz, 2 H) ppm. 13C NMR cle): Crystal and spectroscopic data.
(100 MHz, CDCl3): δ = 19.3 (CH3), 23.8 (CH3), 26.7 (CH3), 28.2
(CH), 40.8 (CH3), 44.0 (CH2), 53.7 (CH2), 112.0 (CH), 115.2
Acknowledgments
(CH2), 124.0 (CH), 126.1 (CH), 129.3 (CH), 131.3 (Cq), 137.3
(CH), 140.7 (Cq), 146.2 (Cq), 147.0 (Cq), 148.5 (Cq) ppm. 11B NMR
This work was supported by the Global COE Program (Chemistry
Innovation through Cooperation of Science and Engineering) and
by KAKENHI from the Ministry of Education, Culture, Sports,
Science and Technology, Japan (21245023 and 21685006).
(160 MHz, CDCl3): δ = 32.4 (br. s) ppm. HRMS (ESI-TOF): calcd.
for C40H56BN3 [7g + H] 590.4652; found 590.4668.
10: In a 5-mL vial, a mixture of 8ba (2.17 g, 4.97 mmol), pinacol
(881 mg, 7.46 mmol), thf (1 mL), and TsOH·H2O (1.42 g,
7.47 mmol) was stirred for 7 d at room temperature. The mixture
was passed through a pad of Celite, and the solvent was removed
in vacuo. The residue was purified by preparative TLC (hexane/
CH2Cl2, 1:1) to afford 10 as a colorless solid (902 mg, 3.70 mmol,
74%). M.p. 51.1–53.6 °C. 1H NMR (500 MHz, CDCl3): δ = 1.32
(s, 12 H), 1.58 (s, 3 H), 3.41 (d, J = 7 Hz, 2 H), 4.88 (dd, J = 10,
2 Hz, 1 H), 4.93 (ddd, J = 17, 3, 2 Hz, 1 H), 5.72 (ddt, J = 17, 10,
7 Hz, 1 H), 7.08 (dd, J = 8, 2 Hz, 2 H), 7.22 (t, J = 7 Hz, 1 H),
7.31 (t, J = 8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
18.4 (CH3), 25.0 (CH3), 42.5 (CH2), 83.3 (Cq), 115.2 (CH2), 123.9
(br. s, B-C), 126.4 (CH), 128.0 (CH), 128.2 (CH), 137.2 (CH), 143.2
(Cq), 152.6 (Cq) ppm.C18H25BO2 (284.20): calcd. C 76.07, H 8.87;
found C 76.38, H 9.03.
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9: In a 20-mL Schlenk flask, Pd2(dba)3 (18.9 mg, 20.6 μmol,
10 mol-%), PtBu3 (8.3 mg, 41 μmol), 4-nitroiodobenzene (58.1 mg,
0.233 mmol), 10 (57.6 mg, 0.203 mmol), and thf (2.00 mL) were
placed in the glove box. After the Schlenk flask was removed, de-
gassed KOH aq. (3.00 m, 200 μL, 0.600 mmol) was added, and the
resulting mixture was stirred for 12 h at room temperature under
an argon atmosphere. To the reaction mixture was added sat.
NH4Cl aq., and the resulting mixture was extracted with CH2Cl2.
The combined organic layer was washed with NaHCO3 and brine
and then dried with MgSO4. Filtration and evaporation afforded a
brown oil. The oily product was purified by preparative HPLC (sil-
ica gel; hexane/CH2Cl2, 5:1; two times) to afford 9 as a yellow oil
1
(49.7 mg, 0.178 mol, 88%). H NMR (500 MHz, CDCl3): δ = 1.89
(s, 3 H), 2.96 (d, J = 6 Hz, 2 H), 4.85 (dq, J = 17, 2 Hz, 1 H), 4.90
(dq, J = 10, 2 Hz, 1 H), 5.61 (ddt, J = 17, 10, 6 Hz, 1 H), 7.24 (dd,
J = 5, 3 Hz, 2 H), 7.29 (tt, J = 7, 1 Hz, 1 H), 7.39 (t, J = 8 Hz, 2
H), 7.45 (dt, J = 9, 2 Hz, 2 H), 8.24 (dt, J = 9, 2 Hz, 2 H) ppm.
13C NMR (126 MHz, CDCl3): δ = 22.5 (CH3), 40.2 (CH2), 116.1
(CH2), 123.8 (CH), 127.0 (CH), 128.4 (CH), 128.9 (CH), 129.2
(CH), 133.0 (Cq), 135.7 (CH), 137.6 (Cq), 141.7 (Cq), 146.7 (Cq),
151.3 (Cq) ppm. HRMS (ESI-TOF): calcd. for C36H34N2NaO4
[2ϫ9 + Na] 581.2416; found 581.2442.
X-ray Crystallography: Details of the crystal data and a summary
of the intensity data collection parameters for 3b·(thf)3, 8aa, 8bb,
and 8bg are listed in Table S1 (Supporting Information). A suitable
crystal was mounted with cooled mineral oil to the glass fiber and
transferred to the goniometer of a Rigaku Mercury CCD dif-
fractometer with graphite-monochromated Mo-Kα radiation (λ =
0.71070 Å) to 2θ max = 50°. The structures were solved by direct
methods with SIR-97[22] and refined by full-matrix least-squares
techniques against F2 SHELXL-97.[23] The intensities were cor-
rected for Lorentz and polarization effects. Non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were placed using
AFIX instructions.
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CCDC-816384 [for 3b·(thf)3], -821253 (for 8aa), -816385 (for 8bb),
and -816386 (for 8bg) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Eur. J. Org. Chem. 2011, 3951–3958
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3957

Y. Okuno, M. Yamashita, K. Nozaki
FULL PAPER
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1
in the H NMR spectrum (see Supporting Information).
[19] The product was an inseparable mixture consisting of syn-9ba,
isomerized 1,3-diene, and isomerized anti-9ba. The latter two
1
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Received: March 17, 2011
Published Online: May 17, 2011
3958
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 3951–3958