NHC-Copper-Catalyzed Tandem Hydrocupration and Allylation of Alkenyl Boronates

Article abstract of DOI:10.1055/s-0036-1588811

A tandem hydrocupration/allylation of alkenyl boronates efficiently proceeds with NHC-copper catalysts using hydrosilane and allyl phosphate as reagents. In the presence of IMes-Cu catalyst, the allylation of in situ generated Β-α-copper intermediates smoothly occurs to give homoallylic boronates in high yields, despite competitive side reaction pathways. Mono- and disubstituted alkenyl boronates were effective in the reaction with terminal allyl phosphates, but trisubstituted substrates showed limited reactivity.

Full text of DOI:10.1055/s-0036-1588811

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–F
special topic
A
en
W. J. Jang et al.
Special Topic
Synthesis
NHC-Copper-Catalyzed Tandem Hydrocupration and Allylation of
Alkenyl Boronates
Won Jun Jang
Jung Tae Han
Jaesook Yun*
O
Bpin
CuIMes
OP(OEt)2
Bpin
IMes–CuCl
Bpin
R
R
R
Si
H
H
H
Department of Chemistry and Institute of Basic Science,
Sungkyunkwan University, Suwon 16419, Korea
jaesook@skku.edu
homoallylic boronate
R = aryl, heteroaryl,
H, alkyl
• 14 examples
• up to 97% yield
Published as part of the Special Topic Modern Strategies for Borylation
in Synthesis
Received: 03.03.2017
Accepted after revision: 04.04.2017
Published online: 03.05.2017
DOI: 10.1055/s-0036-1588811; Art ID: ss-2017-c0138-st
LCu
H
(a)
(c)
hydrocupration/
allylation
Bpin
R
LG
Bpin
Abstract A tandem hydrocupration/allylation of alkenyl boronates ef-
ficiently proceeds with NHC-copper catalysts using hydrosilane and allyl
phosphate as reagents. In the presence of IMes–Cu catalyst, the allyla-
tion of in situ generated Β-α-copper intermediates smoothly occurs to
give homoallylic boronates in high yields, despite competitive side reac-
tion pathways. Mono- and disubstituted alkenyl boronates were effec-
tive in the reaction with terminal allyl phosphates, but trisubstituted
substrates showed limited reactivity.
R
+
via
target molecule
Bpin
CuL
R
(b)
[Cu]
R
B-α-organocopper
intermediate
(a) hydrocupration of alkenyl boronates
(b) direct allylation of alkenyl boronates
(c) Cu–H reaction with the allyl electrophile
Key words allylic substitution, copper, homoallylic boronates, hydro-
cupration, N-heterocyclic carbenes, tandem reaction
competitive reactions
Scheme 1 Overview of CuH-catalyzed hydroallylation of alkenyl boro-
nates and possible competitive reaction pathways
Copper-catalyzed allylic substitution has recently made
great progress with organoboron nucleoophiles.1 In com-
parison with highly reactive organometallic nucleophiles
such as Grignard, organozinc, and organoaluminum re-
agents,2 mild organoboron reagents have been widely ex-
plored due to their merits of high functional group compat-
ibility, wide accessibility, and easy handling. Alkylboranes
and aryl, alkenyl, allenyl, and propargyl boronates have
been utilized to deliver new organic nucleophiles to an al-
lylic electrophile in copper-catalyzed C–C bond formation.3
Due to the significance of organoboron compounds in
organic synthesis, development of their synthetic methods
in a stereodefined manner is considered valuable.4 More-
over, the synthetic versatility of the olefin functional group
makes the installation of an allylic moiety desirable among
various C–C coupling partners. For this reason, diboron5
and 1,1-diboron-containing organic reagents6 have recently
been utilized in copper-catalyzed allylic substitutions,
where a boron moiety or a boron-containing organic group
is delivered through copper-catalyzed activation of the di-
boron reagent. While these methods afford organoboron
compounds with different skeletons, they discard one bo-
ron moiety during the activation process, and the scope of
1,1-diborylalkane substrates is limited. We recently report-
ed a highly selective, bisphosphine-copper-catalyzed hy-
i-Pr
i-Pr
N
N
N
N
N
N
N
N
Mes
Mes
i-Pr
i-Pr
Cu
Cl
Cl–
Cu
Cl–
Cl
ICy·HCl
IMes·HCl
IPr−CuCl
IMes−CuCl
Figure 1 NHC ligands screened
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

B
W. J. Jang et al.
Special Topic
Synthesis
Table 2 IMesCu-Catalyzed Hydroallylation of Alkenyl Boronates
Table 1 Screening of NHC–Cu Catalysts
Bpin
R'
5 mol% NHC−CuCl
5 mol% IMes-CuCl
4 equiv LiOt-Bu
4 equiv PMHS
Bpin
Bpin
4 equiv LiOt-Bu
OP(O)(OEt)2
R
Bpin
OP(O)(OEt)2
n-Bu
n-Bu
+
R
+
4 equv PMHS
R"
1a
(1 equiv)
2a
R'
R"
(1 equiv)
THF, 40 °C, 12 h
THF, 40 °C, 12 h
(2 equiv)
2
(2 equiv)
1
R', R" = H, Me
R = aryl, alkyl
Entry
Cu catalysta
Yield (%)b
1
ICy·HCl/CuCl
IMes·HCl/CuCl
IMes–CuCl
IPr–CuCl
86
90
95
72
84
Entry
1
2
Yield (%)a
83
2
Bpin
Bpin
3
1
2
4
1b
2b
5c
IMes–CuCl
Bpin
a See Figure 1 for structures.
b Isolated yield.
BnO
Bpin
95
94
89
97
BnO
1c
c 2 equiv each of LiOt-Bu and PMHS were used.
2c
Bpin
Bpin
droallylation of alkenyl boronates and boramides7 (Scheme
1). In this process, hydrocupration of alkenyl boronates – an
addition of Cu–H across the olefinic bond – regioselectively
generated a variety of Β-α-organocopper intermediates,
and their sequential reaction with an allylic electrophile
produced secondary homoallylic boronates in good to high
yields. However, alkenyl boronates generally produced 10–
20% lower yields than alkenyl boramides, which could be
attributed to competitive reaction pathways such as direct
allylation of alkenyl boronates (b)3d and reaction of the Cu–
H catalyst with the allyl electrophile (c)8 (Scheme 1).
Ph
3
4
5
2
Ph
3
1d
2d
Bpin
Bpin
1e
2e
Bpin
Bpin
Bpin
1f
2f
Bpin
In search of a more efficient catalytic system for alkenyl
boronates, we started our investigation by employing N-
heterocyclic carbene (NHC)-bound copper catalysts. We en-
visioned that an NHC-coordinated Cu–H catalyst9 would be
a good candidate for more chemoselective and reactive hy-
droallylation of alkenyl boronates. Facile generation of Cu–
H species with tight coordination by the NHC ligand could
reduce the undesirable direct allylation pathway of alkenyl
boronates and facilitate hydrocupration of the more substi-
tuted, but electron-deficient alkenyl boronates over the al-
lyl electrophile. 1-Hexenylboronic acid pinacol ester (1a)
was used as the model substrate under conditions applied
to the previously reported bisphosphine-Cu catalytic sys-
tem (Table 1, Figure 1). The use of either NHC salt/CuCl or
NHC–Cu complexes improved the efficiency of the tandem
reaction, giving the desired product in high yield (Table 1,
entries 1–3). The most effective catalyst was IMes–CuCl
{chloro[1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene]-
copper}, which afforded 2a in 95% yield (entry 3), while the
bulkier IPr–CuCl catalyst resulted in a decreased yield (en-
try 4). Reduction in the amounts of base and poly(methyl-
hydrosiloxane) (PMHS) to 2 equivalents was also efficient
despite a slight decrease in yield (entry 5).
6
7
92
81
F
1g
2g
F
Bpin
Bpin
2h
1h
Bpin
Bpin
Bpin
N
S
8
9
81
97
N
1i
1j
2i
Bpin
S
2j
Bpin
Bpin
10b
11
36c
33d
Ph
Ph
Ph
1k
2k
Bdan
Ph
Bdan
2l-Bdan
1l-Bdan
a Isolated yield.
b The reaction was carried out at 60 °C.
Using the optimized conditions, we explored the scope
and limitations of the reaction using various alkenyl boro-
nates (Table 2). A range of alkenyl boronates from simple vi-
c Full conversion, ratio of syn/anti = 77:23.
d 56% conversion and NMR yield.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

C
W. J. Jang et al.
Special Topic
Synthesis
Table 3 Hydroallylation of Alkenyl Boronates with an Internal Allyl Phosphate
Bpin
R
syn-4
anti-4
5 mol% IMes-CuCl
4 equiv LiOt-Bu
4 equiv PMHS
Ph
Bpin
Ph
OP(O)(OEt)2
R
+
+
THF, 40 °C, 12 h
1
3
Bpin
R
Ph
Entry
Alkenyl boronate 1
Product
Yield (%)a
Ratio (syn-4/anti-4)b
1
2
3
1b (R = H)
4b
4a
4f
96
81
87
34:66
71:29
83:17
1a (R = n-Bu)
1f (R = Ph)
a Isolated yield of combined syn-4 and anti-4.
b Ratio determined by 1H NMR analysis.
nyl boronate to those with primary and tertiary alkyl sub-
stituents were efficient substrates, affording the allyl-cou-
pled products 2b–e in good to excellent yields. Substrates
with aromatic and heteroaromatic substituents also suc-
cessfully underwent the reaction to furnish homoallylic bo-
ronates 2f–j in high yields. The yields with this catalytic
system were generally higher than those obtained under
previous conditions using bisphosphine ligands. In addition
to disubstituted alkenyl boronates, trisubstituted alkenyl
boronate 1k and alkenyl boramide 1l-Bdan (dan: 1,8-diami-
nonaphthyl) afforded products in moderate yields. Consid-
ering the steric congestion around the double bond of 1k
and 1l compared to the terminal allyl phosphate, these re-
sults demonstrate higher reactivity and chemoselectivity of
the current IMes–Cu catalytic system than the previous sys-
tem. For example, 1k and 1l were completely inactive, and
none of the desired product was observed with the previ-
ous bisphosphine-Cu catalytic system.7
As shown in Table 3, disubstituted allyl phosphates
could also be utilized in the tandem reaction. Perfect regi-
oselectivity and good yields were obtained in the reaction,
but a diastereomeric mixture of products was formed. The
reaction of simple vinyl boronate (1b) formed products in
high yield with the anti-isomer as the major product,10 but
disubstituted alkenyl boronates 1a and 1f produced the
syn-isomer as the major product (Table 3, entries 1–3).11 As
the steric bulk of R increased, the syn to anti ratio gradually
improved.
ever, no chirality transfer was observed, resulting in a race-
mic product formation (see, Scheme S1 in the Supporting
Information).
5 mol% CuCl/NHC
4 equiv LiOt-Bu
Bpin
OP(O)(OEt)2
4 equiv PMHS
Bpin
Ph
1f
+
Ph
THF, 40 °C, 12 h
(S)-2f
30% yielda
Ph
Ph
N
Ph
N
conv. 85%: 35% yielda
(25% ee)
NHC =
BF4
Scheme 2 Asymmetric hydroallylation with a Chiral NHC–Cu catalyst.
a NMR yield determined with an internal standard.
Since the alkenylboron compounds 1 can be easily pre-
pared by copper-catalyzed hydroboration of alkynes,13 one-
pot, sequential hydroboration-hydroallylation reaction was
carried out starting from a terminal alkyne (Scheme 3). For
the one-pot reaction, the IPr–CuCl complex was chosen as
the precatalyst due to its higher regioselectivity than IMes–
CuCl in the hydroboration. The reaction proceeded well to
furnish the desired 2f in 63% yield without isolation of the
alkenyl boronate intermediate.
5 mol% IPr−CuCl
10 mol% LiOt-Bu
Bpin
Ph
HBpin
+
Ph
THF, rt, 2 h
1f
Next, we briefly conducted an asymmetric hydroallyla-
tion with a chiral NHC salt/CuCl (Scheme 2). The chiral cat-
alyst used in the study was less efficient than the non-chiral
IMes–CuCl catalyst, and a substantial amount of reduced
product from the alkenyl boronate was produced. This sys-
tem needs further improvement, and related investigations
are underway. Furthermore, a chiral secondary allyl phosh-
phate 512 was applied to the catalytic conditions to check
the degree of chirality transfer in the hydroallylation. How-
OP(O)(OEt)2
2 equiv
4 equiv LiOt-Bu
4 equiv PMHS
THF, 40 °C, 12 h
Bpin
Ph
conv. > 98%
yield = 63%
2f
Scheme 3 One-pot hydroboration and hydroallylation
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

D
W. J. Jang et al.
Special Topic
Synthesis
In conclusion, we have demonstrated that the tandem
hydroallylation of alkenyl boronates proceeds efficiently
with an electron-donating IMes–Cu complex. This protocol
provides a straightforward approach to secondary homoal-
lylic boronates, which could be transformed into a variety
of organic derivatives. Further studies on catalytic tandem
coupling reactions using challenging substrates are in prog-
ress.
The characterization data for 2b were concordant with those previ-
ously reported in the literature.7
2-[1-(Benzyloxy)hex-5-en-3-yl]-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (2c)
Yield: 150 mg (95%); colorless oil.
1H NMR (500 MHz, CDCl3): δ = 7.35–7.30 (m, 4 H), 7.27–7.24 (m, 1 H),
5.79 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.00 (dd, J = 17.0, 2.0 Hz, 1 H),
4.94 (dd, J = 10.0, 2.0 Hz, 1 H), 4.50 (s, 2 H), 3.46 (t, J = 7.0 Hz, 2 H),
2.20 (dt, J = 14.0, 7.5 Hz, 1 H), 2.12 (dt, J = 14.0, 7.0 Hz, 1 H), 1.80–1.66
(m, 2 H), 1.19 (d, J = 1.5 Hz, 12 H), 1.21–1.15 (m, 1 H).
CuCl, LiOt-Bu, PMHS, diethyl allyl phosphate, and other commercial
reagents were purchased from Aldrich and used as received. Com-
pounds 1a–l, 3,7 and 512 were prepared by following the literature
procedures. Reactions with oxygen- and moisture-sensitive materials
were carried out with standard Schlenk technique. Flash chromatog-
raphy was performed on silica gel from Merck (70–230 mesh). IR
spectra were recorded on a Nicolet 205 FT-IR in cm–1. High-perfor-
mance liquid chromatography (HPLC) was performed using a Young-
lin Acme 9100 series. All 1H NMR spectra were obtained on Bruker at
500 MHz systems and reported in parts per million (ppm) downfield
from TMS. 13C NMR spectra are reported in ppm referenced to CDCl3
(77.16 ppm). High-resolution mass spectra (HRMS) were obtained at
Sogang Center for Research Facilities of Sogang University and report-
ed in the form of m/z (relative intensity).
13C NMR (125 MHz, CDCl3): δ = 138.7, 138.3, 128.3, 127.7, 127.4,
115.1, 83.0, 72.8, 69.7, 35.4, 30.7, 24.79, 24.75, 20.2 (C–B).
The characterization data for 2c were concordant with those previ-
ously reported in the literature.7
4,4,5,5-Tetramethyl-2-(8-phenyloct-1-en-4-yl)-1,3,2-dioxaboro-
lane (2d)
Yield: 148 mg (94%); colorless oil.
IR (neat): 3064, 3026, 1640, 1464, 1371, 1144 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 7.27–7.24 (m, 2 H), 7.17–7.13 (m, 3 H),
5.79 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.00 (dd, J = 17.0, 2.0 Hz, 1 H),
4.92 (dd, J = 10.0, 2.0 Hz, 1 H), 2.59 (t, J = 7.5 Hz, 2 H), 2.19–2.07 (m, 2
H), 1.66–1.57 (m, 2 H), 1.46–1.30 (m, 2 H), 1.20 (s, 12 H), 1.08–1.04
(m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 142.9, 138.7, 128.4, 128.2, 125.5,
114.8, 83.0, 35.9, 35.6, 31.6, 30.8, 28.7, 24.8, 23.6 (C–B).
NHC-Copper-Catalyzed Tandem Hydrocupration and Allylation of
Alkenyl Boronates; General Procedure
A mixture of IMes–CuCl (5 mol %, 0.025 mmol) and LiOt-Bu (2 mmol)
in anhyd THF (0.5 mL) were stirred for 5 min in a Schlenk tube under
an atmosphere of N2. PMHS (2 mmol) was added to the reaction mix-
ture and stirred for another 15 min at r.t. Substrate 1 dissolved in THF
(0.5 mL) and diethyl allyl phosphate were added. The reaction mix-
ture was stirred at 40 °C and the progress of the reaction was moni-
tored by TLC. Upon completion of the reaction, the reaction mixture
was diluted with Et2O (10 mL) and quenched with HCl (0.5 M in
MeOH, 4 mL) over 30 min. The aqueous layer was extracted with Et2O,
the combined organic layers were dried (Na2SO4), and concentrated in
vacuo. The product was purified by silica gel chromatography.
HRMS (ESI): m/z [M + Na]+ calcd for C20H31BO2Na: 337.2313; found:
337.2313.
2-(6,6-Dimethylhept-1-en-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (2e)
Yield: 112 mg (89%); colorless oil.
IR (neat): 3077, 2978, 1640, 1469, 1381, 1145 cm–1
.
1H NMR (500 MHz, CDCl3): δ = 5.78 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H),
5.01 (dd, J = 17.0, 2.0 Hz, 1 H), 4.95 (d, J = 10.0, 2.0 Hz, 1 H), 2.16 (dt,
J = 14.5, 7.5 Hz, 1 H), 2.05 (dt, J = 14.0, 7.0 Hz, 1 H), 1.51 (dd, J = 13.5,
10.5 Hz, 1 H), 1.23 (d, J = 2.0 Hz, 12 H), 1.17 (dd, J = 13.5, 2.5 Hz, 1 H),
1.11–1.04 (m, 1 H), 0.87 (s, 9 H).
13C NMR (125 MHz, CDCl3): δ = 142.9, 138.7, 128.4, 128.2, 125.5,
114.8, 83.0, 35.9, 35.6, 31.6, 30.8, 28.7, 24.8, 23.6 (C–B).
4,4,5,5-Tetramethyl-2-(non-1-en-4-yl)-1,3,2-dioxaborolane (2a)
Yield: 120 mg (95%); pale yellow oil.
1H NMR (500 MHz, CDCl3): δ = 5.80 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H),
5.00 (dd, J = 17.0, 1.5 Hz, 1 H), 4.92 (dd, J = 10.0, 1.5 Hz, 1 H), 2.20–
2.08 (m, 2 H), 1.43–1.25 (m, 8 H), 1.23 (s, 12 H), 1.10–1.03 (m, 1 H),
0.87 (t, J = 7.0 Hz, 3 H).
HRMS (ESI): m/z [M + Na]+ calcd for C15H29BO2Na: 275.2156; found:
275.2155.
13C NMR (125 MHz, CDCl3): δ = 138.6, 114.4, 82.7, 35.4, 31.9, 30.7,
28.6, 24.6, 23.3 (C–B), 22.4, 13.8.
4,4,5,5-Tetramethyl-2-(1-phenylpent-4-en-2-yl)-1,3,2-dioxaboro-
lane (2f)
The characterization data for 2a were concordant with those previ-
Yield: 132 mg (97%); pale yellow oil.
ously reported in the literature.7
1H NMR (500 MHz, CDCl3): δ = 7.26–7.20 (m, 4 H), 7.17–7.13 (m, 1 H),
5.83 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.04 (dd, J = 17.0, 2.0 Hz, 1 H),
4.97 (d, J = 10.0 Hz, 1 H), 2.73 (dd, J = 14.0, 9.0 Hz, 1 H), 2.69 (dd, J =
14.0, 7.5 Hz, 1 H), 2.18 (t, J = 7.0 Hz, 2 H), 1.51–1.45 (m, 1 H), 1.17 (s, 6
H), 1.14 (s, 6 H).
13C NMR (125 MHz, CDCl3): δ = 142.0, 138.2, 128.9, 128.1, 125.6,
115.2, 83.1, 36.7, 35.2, 25.3 (C–B), 24.8, 24.7
4,4,5,5-Tetramethyl-2-(pent-4-en-2-yl)-1,3,2-dioxaborolane (2b)
Yield: 81 mg (83%); pale yellow oil.
1H NMR (500 MHz, CDCl3): δ = 5.81 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H),
5.00 (dd, J = 17.0, 2.0 Hz, 1 H), 4.94 (d, J = 10.0, 2.0 Hz, 1 H), 2.21 (dt,
J = 14.0, 7.0 Hz, 1 H), 2.05 (dt, J = 14.0, 7.0 Hz, 1 H), 1.23 (s, 12 H),
1.15–1.08 (m, 1 H), 0.97 (dt, J = 7.5 Hz, 3 H).
The characterization data for 2f were concordant with those previ-
13C NMR (125 MHz, CDCl3): δ = 138.7, 114.8, 83.0, 37.3, 24.8, 16.9 (C–
B), 15.1
ously reported in the literature.7
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

E
W. J. Jang et al.
Special Topic
Synthesis
2-[1-(3-Fluorophenyl)pent-4-en-2-yl]-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2g)
1H NMR (500 MHz, CDCl3): δ (major isomer) = 7.29–7.27 (m, 1 H),
7.24–7.15 (m, 4 H), 5.75–5.67 (m, 1 H), 4.94–4.86 (m, 2 H), 2.79–2.72
(m, 1 H), 1.99–1.86 (m, 2 H), 1.40–1.35 (m, 1 H), 1.27 (s, 12 H), 1.26 (d,
J = 7.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3): δ (major isomer) = 147.3, 138.2 128.3,
127.3, 125.9, 114.9, 83.2, 41.4, 34.7, 25.1, 25.0, 22.8. The signal for the
boron-bound carbon was not observed due to quadrupolar relaxation.
Yield: 133 mg (92%); pale yellow oil.
1H NMR (500 MHz, CDCl3): δ = 7.21–7.16 (m, 1 H), 6.98–6.82 (m, 3 H),
5.81 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.03 (dd, J = 17.0, 1.5 Hz, 1 H),
4.98 (dd, J = 10.0, 1.0 Hz, 1 H), 2.74–2.65 (m, 2 H), 2.22–2.14 (m, 2 H),
1.47–1.41 (m, 1 H), 1.16 (s, 6 H), 1.14 (s, 6 H).
13C NMR (125 MHz, CDCl3): δ = 162.8 (d, J = 244.8 Hz), 144.8 (d, J = 7.1
Hz), 137.9, 129.4 (d, J = 8.3 Hz), 124.6 (d, J = 2.7 Hz), 115.7 (d, J = 20.7
Hz), 115.5, 112.5 (d, J = 21.0 Hz), 83.2, 36.5, 35.2, 25.1 (C–B), 24.78,
24.75.
HRMS (ESI): m/z [M + Na]+ calcd for C18H27BO2Na: 309.2000; found:
309.2001.
4,4,5,5-Tetramethyl-2-(3-phenylnon-1-en-4-yl)-1,3,2-dioxaboro-
lane (4a)
The characterization data for 2g were concordant with those previ-
ously reported in the literature.7
Yield: 133 mg (81%); colorless oil.
1H NMR (500 MHz, CDCl3): δ (major isomer) = 7.32–7.27 (m, 1 H),
7.24–7.11 (m, 4 H), 5.83 (ddd, J = 17.0, 10.0, 9.0 Hz, 1 H), 4.99–4.93
(m, 2 H), 3.23 (dd, J = 10.5, 9.0 Hz, 1 H), 1.61–1.27 (m, 9 H), 0.96 (s, 6
H), 0.92 (s, 6 H), 0.88 (t, J = 7.0 Hz, 3 H).
4,4,5,5-Tetramethyl-2-[1-(o-tolyl)pent-4-en-2-yl]-1,3,2-dioxaboro-
lane (2h)
Yield: 116 mg (81%); pale yellow oil.
13C NMR (125 MHz, CDCl3): δ (major isomer) = 144.9, 142.8, 128.3,
128.0, 126.1, 114.2, 82.8, 52.7, 32.1, 30.0, 29.0, 24.6, 24.5, 22.6, 14.0.
The signal for the boron-bound carbon was not observed due to quad-
rupolar relaxation.
1H NMR (500 MHz, CDCl3): δ = 7.19–7.17 (m, 1 H), 7.10–7.04 (m, 3 H),
5.83 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.05 (ddd, J = 17.0, 2.0 Hz, 1 H),
4.97 (dd, J = 10.0, 2.0 Hz, 1 H), 2.71 (dd, J = 14.0, 9.0 Hz, 1 H), 2.65 (dd,
J = 14.0, 7.0 Hz, 1 H), 2.31 (s, 3 H), 2.26–2.16 (m, 2 H), 1.49–1.42 (m, 1
H), 1.17 (s, 6 H), 1.13 (s, 6 H).
The characterization data for 4a were concordant with those previ-
ously reported in the literature.7
13C NMR (125 MHz, CDCl3): δ = 140.2, 138.2, 136.2, 130.0, 129.3,
125.7, 125.5, 115.3, 83.1, 35.7, 34.0, 24.8, 24.7, 23.9 (C–B), 19.5.
4,4,5,5-Tetramethyl-2-(3-phenylpent-4-en-2-yl)-1,3,2-dioxaboro-
lane (4b)
The characterization data for 2h were concordant with those previ-
ously reported in the literature.7
Yield: 131 mg (96%); colorless oil.
3-[2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)pent-4-en-1-
yl]pyridine (2i)
1H NMR (500 MHz, CDCl3): δ (major isomer) = 7.30–7.27 (m, 2 H),
7.25–7.21 (m, 1 H), 7.19–7.17 (m, 2 H), 6.03 (ddd, J = 17.0, 10.0, 8.0
Hz, 1 H), 5.09–4.99 (m, 2 H), 3.27 (dd, J = 11.0, 8.0 Hz, 1 H), 1.52–1.45
(m, 1 H), 1.25 (s, 6 H), 1.24 (s, 6 H), 0.78 (d, J = 7.5 Hz, 3 H).
13C NMR (125 MHz, CDCl3): δ (major isomer) = 143.8, 142.5, 128.4,
128.0, 126.1, 113.9, 83.1, 52.9, 24.8, 24.7, 22.4 (C–B), 13.9.
Yield: 111 mg (81%); pale yellow oil.
1H NMR (500 MHz, CDCl3): δ = 8.49 (br s, 1 H), 8.43 (br s, 1 H), 7.53 (d,
J = 8.0 Hz, 1 H) 7.19–7.17 (m, 1 H), 5.86–5.77 (m, 1 H), 5.04 (dd, J =
17.0, 1.0 Hz, 1 H), 5.00 (dd, J = 10.0, 1.0 Hz, 1 H), 2.74–2.65 (m, 2 H),
2.24–2.14 (m, 2 H), 1.48–1.42 (m, 2 H), 1.16 (s, 6 H), 1.13 (s, 6 H).
The characterization data for 4b were concordant with those previ-
ously reported in the literature.6c
13C NMR (125 MHz, CDCl3): δ = 150.3, 147.1, 137.7, 137.3, 136.3,
123.0, 115.7, 83.3, 35.1, 33.7, 31.5 (C–B), 24.7.
2-(1,3-Diphenylpent-4-en-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (4f)
The characterization data for 2i were concordant with those previ-
ously reported in the literature.7
Yield: 151 mg (87%); colorless oil.
4,4,5,5-Tetramethyl-2-[1-(thiophen-3-yl)pent-4-en-2-yl]-1,3,2-di-
oxaborolane (2j)
IR (neat): 3083, 3026, 1636, 1601, 1377, 1143 cm–1
.
1H NMR (500 MHz, CDCl3): δ (major isomer) = 7.39–7.14 (m, 10 H),
6.12 (ddd, J = 17.0, 10.0, 8.5 Hz, 1 H), 5.18 (dd, J = 17.0, 1.5 Hz, 1 H),
5.06 (dd, J = 10.0, 1.0 Hz, 1 H), 3.48–3.44 (m, 1 H), 2.62–2.51 (m, 2 H),
2.01–1.95 (m, 1 H), 1.15 (s, 6 H), 1.06 (s, 6 H).
13C NMR (125 MHz, CDCl3): δ (major isomer) = 144.1, 142.4, 141.7,
128.8, 128.4, 128.0, 127.7, 126.4, 125.7, 114.8, 83.2, 52.8, 36.1, 24.5,
24.4144.9, 142.8, 128.3, 128.0, 126.1, 114.2, 82.8, 52.7, 32.1, 30.0,
29.0, 28.9, 24.6, 24.5, 22.6, 14.04. The signal for the boron-bound car-
bon was not observed due to quadrupolar relaxation.
Yield: 135 mg (97%); pale yellow oil.
1H NMR (500 MHz, CDCl3): δ = 7.20–7.19 (m, 1 H), 6.95 (d, J = 4.0 Hz, 2
H), 5.82 (ddt, J = 17.0, 10.0, 7.0 Hz, 1 H), 5.03 (dd, J = 17.0, 2.0 Hz, 1 H),
4.97 (dd, J = 10.0, 2.0 Hz, 1 H), 2.75 (dd, J = 14.5, 9.0 Hz, 1 H), 2.69 (dd,
J = 14.5, 7.0 Hz, 1 H), 2.20–2.17 (m, 2 H), 1.50–1.44 (m, 1 H), 1.16 (s, 6
H), 1.14 (s, 6 H).
13C NMR (125 MHz, CDCl3): δ = 142.4, 138.1, 128.6, 124.8, 120.5,
115.3, 83.1, 35.3, 31.1, 24.8, 24.74, 24.71. The signal for the boron-
bound carbon was not observed due to quadrupolar relaxation.
HRMS (ESI): m/z [M + Na]+ calcd for C23H29BO2Na: 371.2157; found:
371.2159.
The characterization data for 2j were concordant with those previ-
ously reported in the literature.7
Funding Information
4,4,5,5-Tetramethyl-2-(2-phenylhex-5-en-3-yl)-1,3,2-dioxaboro-
lane (2k)
National
Research
Foundation
of
Korea
grant
(NRF-
Yield: 52 mg (36%); colorless oil.
2016R1A2B4011719) funded by the Korean government (MEST).
IR (neat): 3076, 3028, 1639, 1451, 1378, 1143 cm–1
.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

F
W. J. Jang et al.
Special Topic
Synthesis
Supporting Information
(5) (a) Ito, H.; Ito, S.; Sasaki, Y.; Matsuura, K.; Sawamura, M. J. Am.
Chem. Soc. 2007, 129, 14856. (b) Guzman-Martinez, A.;
Hoveyda, A. H. J. Am. Chem. Soc. 2010, 132, 10634.
(6) (a) Kim, J.; Park, S.; Park, J.; Cho, S. H. Angew. Chem. Int. Ed. 2016,
55, 1498. (b) Shi, Y.; Hoveyda, A. H. Angew. Chem. Int. Ed. 2016,
55, 3455. (c) Zhang, Z.-Q.; Zhang, B.; Lu, X.; Liu, J.-H.; Lu, X.-Y.;
Xiao, B.; Fu, Y. Org. Lett. 2016, 18, 952.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1588811.
S
u
p
p
ortiInfogrmoaitn
S
u
p
p
ortioInfgrmoaitn
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F