Studies on copper(I)-catalyzed highly regio- and stereo-selective hydroboration of alkynamides

Article abstract of DOI:10.1039/c4ob00979g

The copper(i)-catalyzed hydroboration of alkynamides with B ₂pin₂ afforded the alkenamide boronates in 66% to nearly quantitative yields with high regio- and stereo-selectivity. It was interesting to note that the regio-selectivity of the reaction is opposite to that observed in the carbometallation reaction of alkynamides, and the resulting alkenyl boronates provided access to α,-disubstituted (Z)-alkenamides through further elaboration. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ob00979g

Organic &
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Studies on copper(I)-catalyzed highly regio- and
stereo-selective hydroboration of alkynamides†
Cite this: Org. Biomol. Chem., 2014,
12, 5945
Guangke He, Shan Chen, Qiang Wang, Hai Huang, Qijun Zhang, Dongming Zhang,
Rong Zhang and Hongjun Zhu*
The copper(I)-catalyzed hydroboration of alkynamides with B2pin2 afforded the alkenamide boronates in
66% to nearly quantitative yields with high regio- and stereo-selectivity. It was interesting to note that the
regio-selectivity of the reaction is opposite to that observed in the carbometallation reaction of alkyn-
amides, and the resulting alkenyl boronates provided access to α,β-disubstituted (Z)-alkenamides through
further elaboration.
Received 13th May 2014,
Accepted 17th June 2014
DOI: 10.1039/c4ob00979g
www.rsc.org/obc
1. Introduction
Vinylboronates are essential building blocks in organic syn-
thesis.1 Their utility as partners in Suzuki–Miyaura coupling
reaction2 and their ability3 to undergo Rh-catalyzed3 and
metal-free4 conjugate additions make them highly versatile
intermediates in the construction of complex molecules.
Although several approaches to alkenyl boronates5 have been
disclosed in the past few years, hydroboration6 of alkynes7 is
still a direct and efficient method for obtaining vinylboronates
with regio- and stereo-selectivity.8
Renewed interest in the field has been spurred on by Cu(I)-
catalyzed hydroboration of functionalized internal alkynes
utilizing two different catalytic species ([LCuB] and [LCuH])
generated from bis(pinacolato)diboron (B2pin2) and pinacol-
borane (HBpin), respectively (Scheme 1). Recently, Yun,9
Carretero,10 McQuade11 and Zhu12 have developed the stereo-
selective addition of boryl copper species [LCuB] to functiona-
lized alkynes, affording the corresponding alkenyl boronates
with β-site regioselectivity predominantly. In the meantime,
Lipshutz13 and Tsuji14 have also described the copper hydride
species [LCuH] catalyzed stereoselective hydroboration of
unsymmetrical internal alkynes with high α-site regioselec-
tivity. However, the Cu-catalyzed borylation of N-(1-alkynyl)-
amides with borylating reagents, B2pin2 and HBpin, has not
been explored.15 In previous studies, we have demonstrated
that aryl- and TMS-substituted alkynamides could be cata-
Scheme 1 Cu(I)-catalyzed regio- and stereo-selective hydroboration of
alkynamides.
lytically reduced to (Z)-alkenamides with high stereoselectivity by
the boron addition-protonolysis protocol.16 Herein, we report
the copper(I)-catalyzed highly regio- and stereo-selective hydro-
boration of alkynamides and further elaboration of products.
2. Results and discussion
In the initial experiments, the CuCl/t-BuONa catalyzed hydro-
boration of 3-(2-phenylethynyl)oxazolidin-2-one (1a) with
B2pin2 was investigated in anhydrous toluene at room tempera-
ture with monodentate phosphine ligands (Table 1, entries
1–6). The experimental results showed that the reactions with
PPh3, P(Bu-n)3 and P(OEt)3 gave no desired α-site regio-
controlled alkenamide boronate (Z)-2a, but the mixture of the
β-site regio-isomer (Z)-3a and semi-reduced alkenamide (Z)-4a
(entries 1–3).16 When SPhos or XPhos was selected as the
ligand of the present system, the reaction only afforded (Z)-2a
in very poor yields, and the corresponding regio- and chemo-
Department of Applied Chemistry, College of Science, Nanjing Tech University,
Nanjing 211816, People’s Republic of China. E-mail: zhuhj@njtech.edu.cn;
Fax: +86-25-83172358; Tel: +86-25-83172358
†Electronic supplementary information (ESI) available: Copies of 1H NMR and
13C NMR spectra of compounds 1k, 1p, (Z)-2a–(Z)-2p, (Z)-5a and (Z)-5j. CCDC
944761. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c4ob00979g
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a
Table 1 Screening reaction conditions of Cu(I)-catalyzed hydroboration of 3-(2-phenylethynyl)oxazolidin-2-one (1a) with B2pin2
Entry
Catalyst
Ligand
Time (h)
NMR yield of (Z)-2ab
Ratio of (Z)-2a/(Z)-3a/(Z)-4ac
Recovery of 1a
1
2
3
4
5
6
7
8
CuCl
CuCl
CuCl
CuCl
CuCl
CuCl
CuCl
CuCl
CuBr
CuI
PPh3
P(Bu-n)3
P(OEt)3
SPhos
XPhos
LB-Phos·HBF4
Xantphos
DPEphos
Xantphos
Xantphos
Xantphos
2.5
15
0%
0%
0%
0/5/95
0/9/91
0/21/79
5/13/82
36/41/23
94/2/4
0%
3.5%
0%
5.5%
0%
0%
1.6
4.0
1.0
6.0
4.5
16
24
24
48
4%
29%
84%
84% (80%)d
64%
34%
11%
0%
95/5/0
0%
84/16/0
89.5/10.5/0
78.5/21.5/0
0/0/0
12%
58%
76%
92%
9
10
11
—
a Reaction conditions: 1a (0.3 mmol), B2pin2 (0.33 mmol), catalyst (0.03 mmol), ligand (0.036 mmol), t-BuONa (0.045 mmol), methanol
(0.6 mmol), toluene (1 mL), N2, rt. b NMR yield based on 1a using mesitylene as the internal standard. c The molar ratio of (Z)-2a/(Z)-3a/(Z)-4a was
determined by 1H NMR analysis of the crude product. d Isolated yield.
selectivity were not satisfactory (entries 4–5). Surprisingly, in
the case of LB-Phos·HBF4,17 the yield of the Cu(I)-catalyzed
hydroboration reaction could be dramatically increased to 84%
with good reactivity and selectivity (entry 6). Further screenings
indicated that bidentate phosphine ligands had a pronounced
effect on the reaction. To our delight, the reactivity was greatly
enhanced with the xantphos ligand while obtaining the excel-
lent α-site regioselectivity (entry 7). In contrast, DPEphos was
much less reactive and regioselective (entry 8). Other copper
salt catalysts, such as CuBr and CuI, cannot exhibit good cata-
lytic reactivity under otherwise identical conditions (entries
9–10). No reaction was observed without a catalyst (entry 11).
With the optimized conditions in hand (Table 1, entry 7),
we next investigated the scope and limitations of the Cu-cata-
lyzed hydyoboration. Notably, both N-arylalkynylated and
N-alkylalkynylated oxazolidinones were suitable for the α-site
regio-selective transformation (Table 2, entries 1–5). For N-aryl-
alkynyl substituted oxazolidinones, the alkynamide with a
strong electron-donating group on the arene exhibited higher
reactivity and required shorter time for completion than that
with a strong electron-withdrawing group (compare entry 2
with entry 3). However, the α-borylation of the sterically
demanding t-butyl substituted substrate with B2pin2 cannot
work well and gave the alkenamide boronate (Z)-2e in very
poor yield (entry 5). And oxazolidinones bearing different sub-
stituents, including phenyl and benzyl groups, also partici-
pated in the reaction with the desired alkenylamide boronates
being isolated in 75–82% yields (entries 6–9). Additionally, it
was observed that the phenyl-substituted acyclic sulfonamide
Table 2 Scope of the copper-catalyzed hydroboration of alkynamides
(1) with B2pin2
a
Isolated yield
of (Z)-2 (%)
Entry
R1
R2
Time (h)
1
2
3
Ph (1a)
6
6
12
12
24
36
24
80 (Z-2a)
85 (Z-2b)
66 (Z-2c)
76 (Z-2d)
12 (Z-2e)
75 (Z-2f)
82 (Z-2g)
p-MeOPh (1b)
p-NO2Ph (1c)
n-Pent (1d)
t-Bu (1e)
Ph (1f)
n-Pent (1g)
4
5b
6
7
8
9
Ph (1h)
n-Pent (1i)
24
18
75 (Z-2h)
82 (Z-2i)
10c
Ph (1j)
24
38 (Z-2j)
a Reaction conditions: 1 (0.30 mmol), B2pin2 (0.33 mmol), CuCl
(0.03 mmol), xantphos (0.036 mmol), t-BuONa (0.045 mmol),
methanol (0.6 mmol), toluene (1 mL), N2, rt. b 1e (54%) was recovered.
c 1j (61%) was recovered.
Therefore we attempted to re-evaluate the steric and elec-
(1j) can be also compatible with the conditions but with rela- tronic properties of various phosphine ligands in order to find
tively lower yield (entry 10).
the appropriate one for the acyclic alkynamides. Gratifyingly,
The initial condition screening showed that the reactivity the acylic alkenyl sulfonamide boronates can be obtained in
and regio-selectivity of the Cu-catalyzed hydroboration strongly nearly quantitative yields with high regio- and stereoselectivity
17
depended upon the nature of ligands (Table 1, entries 1–8).
using LB-Phos·HBF4
as the ligand (Table 3, entries 1, 2
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Table 3 The copper-catalyzed hydroboration of alkynamides (1) with
B2pin2 using LB-Phos·HBF4 as the liganda
Entry R1
R2
Time (h) Isolated yield of (Z)-2 (%)
1
2
3
Ph (1j)
n-Pent (1k)
H (1l)
12
18
6
100 (Z-2j)
76 (Z-2k)
74 (2l)
4b
5
Ph (1m)
H (1n)
72
12
90 (Z-2m)
85 (2n)
6
7
Ph (1o)
n-Pent (1p)
30
36
80 (Z-2o)
66 (Z-2p)
Fig. 1 ORTEP-drawing of the X-ray structure of (Z)-2j with 30% thermal
ellipsoids.
8
t-Bu (1e)
24
71 (Z-2e)
a Reaction conditions: 1 (0.30 mmol), B2pin2 (0.33 mmol), CuCl
(0.03 mmol), LB-Phos·HBF4 (0.036 mmol), t-BuONa (0.045 mmol),
methanol (0.6 mmol), toluene (1 mL), N2, rt. b CuCl (20 mol%) was
used and 1m (6%) was recovered.
and 4). As mentioned, N-alkynyl-3-acetylindoles would also be
transformed into the corresponding alkenylboronates in mod-
erate to good yields (entries 6–7). It is surprising that the yield
of sterically bulky alkynamide (1e) can be significantly
improved from 12% to 71% (Table 2, entry 5 vs. Table 3, entry
8). It is noteworthy that when the unsubstituted N-ethynyl-
amides were subjected to the present reaction conditions, the
single α-site regio-controlled alkenyl boronates were also
afforded in good yields with high stereoselectivity (entries 3
and 5), which were vastly different from the β-site regio-
controlled hydroboration of N-ethynylamides with borane in
the literature.15a,b The stereochemistry of the Cu-catalyzed
hydroboration was further confirmed by X-ray diffraction study
of (Z)-2j (Fig. 1).18
Scheme 2 Scale-up experiments.
Despite the Cu-catalyzed hydroboration was routinely con-
ducted at 0.3 mmol scale, we confirmed that the process is
amenable to 10-fold scale-up without compromising reactivity.
In addition, we found that the Cu(I) catalyst loading can be
reduced to 5% mol with comparable efficiency (Scheme 2).
The vinylboronates obtained in this study are useful
organic intermediates for the stereoselective synthesis of
α,β-disubstituted alkenamides (Scheme 3).19 The Suzuki–
Miyaura coupling was performed on ynamides (Z)-2a and (Z)-2j
in THF by using 1.1 equiv. of p-bromoacetophenone to furnish
the α,β-disubstituted (Z)-alkenamides (Z)-5a and (Z)-5j in 84%
and 91% isolated yields, respectively.
Scheme 3 Synthetic application of alkenylamide boronates: synthesis
of α,β-disubstituted (Z)-alkenamides via Suzuki–Miyaura coupling.
base,21 adds to the N-alkynylamide (1) in a syn-fashion with
the boronate moiety adding at the α-carbon to the amide
group, followed by protonolysis of the carbon–copper bond
providing the α-site regio-controlled alkenylamide boronate. It
is interesting to observe that the regio-selectivity is just opposite
to that observed in the carbometallation reaction of ynamides.22
In the latter case, the organometallic species adds to the
N-alkynylamide in a syn-fashion with the metal atom adding at
the α-carbon to the amide group because of the impressive
metal-coordinating ability of ynamido carbonyl oxygen
(Scheme 4). However, it is unclear what is responsible for the
In accordance with literature precedents,20 the hydrobora-
tion of alkynamides promoted by MeOH occurred in the fol-
lowing stages: a ligated and nucleophilic boryl-copper species,
generated from t-BuOCuL and B2pin2 in the presence of a
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4.1.1. Synthesis of starting materials
Typical procedure for the synthesis of ynamides. To a mixture
of N-nucleophiles (5 mmol), K2CO3 (10 mmol), CuSO4·5H2O
(0.5 mmol), and 1,10-phenanthroline (1.0 mmol) in a reaction
vial was added a solution of alkynyl bromides (5.5 mmol) in
toluene (5.0 mL). The reaction mixture was capped and heated
in an oil bath at 80 °C for the indicated time. Upon com-
pletion, the reaction mixture was cooled to room temperature
and diluted with ethyl acetate and filtered through Celite, and
the filtrate was concentrated under vacuum. The crude pro-
ducts were purified by flash chromatography on a silica gel
column with petroleum ether (PE) and ethyl acetate (EA) as the
eluent to afford the desired product.
Scheme 4 Regioselective addition comparison between the hydro-
boration and the carbometallation of alkynamides.
observed regioselectivity of borylcupration of alkynamide up to
now.23
(1) N-Benzyl-N-(hept-1-ynyl)methanesulfonamide (1k)
3. Conclusions
The reaction of CuSO4·5H2O (125.2 mg, 0.5 mmol), 1,10-
phenanthroline (180.0 mg, 1.0 mmol), K2CO3 (1.3208 g,
10.0 mmol), N-benzylmethanesulfonamide (925.7 mg,
5.0 mmol) and 1-heptynyl bromide (957.2 mg, 5.5 mmol) in
toluene (5.0 mL) at 80 °C for 12 h afforded 1k (1.3253 g, yield:
95%) as a colorless liquid. 1H NMR (400 MHz, CDCl3)
δ 7.46–7.32 (m, 5 H), 4.57 (s, 2 H), 2.86 (s, 3 H), 2.25 (t, J =
7.0 Hz, 2 H), 1.52–1.40 (m, 2 H), 1.36–1.21 (m, 4 H), 0.93–0.82
(m, 3 H); 13C NMR (100 MHz, CDCl3) δ 134.8, 128.9, 128.6,
128.5, 72.9, 71.4, 55.6, 38.2, 30.9, 28.5, 22.1, 18.4, 14.0; MS
(ESI) m/z (%) 280 (M+ + 1, 45.5), 302 (M+ + Na, 100); IR ν (KBr,
cm−1) 3032, 2957, 2932, 2861, 2045, 1683, 1535, 1455, 1357,
1163, 1078, 960. HRMS calcd for C15H22NO2S (M + H)+:
280.1366. Found: 280.1384.
In summary, we have developed the copper-catalyzed highly
regio- and stereo-selective hydroboration of alkynamides in the
presence of methanol. The protocol provided an efficient and
simple procedure to afford α-site regio-controlled alkenylamide
boronates in good to excellent yields from readily available
materials, thus allowing an easy access to α,β-disubstituted
(Z)-alkenamides through further elaboration. Further studies
on the factors controlling regioselectivity of the boryl-copper
complex addition to N-alkynylamides are underway in our
laboratory.
4. Experimental
4.1. General methods
(2) 1-(1-(Hept-1-ynyl)-1H-indol-3-yl)ethanone (1p)
The reaction of CuSO4·5H2O (125.3 mg, 0.5 mmol), 1,10-
phenanthroline (180.6 mg, 1.0 mmol), K2CO3 (1.3205 g,
10.0 mmol), 3-acetylindole (796.1 mg, 5.0 mmol) and 1-heptynyl
bromide (957.1 mg, 5.5 mmol) in toluene (5.0 mL) at 80 °C
for 27 h afforded 1p (316.3 mg, yield: 25%) as a light red solid.
Mp 70–71 °C (n-hexane–EA). 1H NMR (400 MHz, CDCl3)
δ 8.38–8.32 (m, 1 H), 7.81 (s, 1 H), 7.55–7.51 (m, 1 H),
7.41–7.30 (m, 2 H), 2.52 (s, 1 H), 2.48 (t, J = 7.1 Hz, 2 H),
1.73–1.63 (m, 2 H), 1.53–1.34 (m, 4 H), 0.95 (t, J = 7.2 Hz, 3 H);
13C NMR (100 MHz, CDCl3) δ 192.8, 138.7, 135.5, 124.9, 124.6,
123.9, 122.7, 119.0, 111.1, 72.0, 70.6, 31.1, 28.4, 27.6, 22.2,
All the reactions were carried out in anhydrous solvents and
under inert atmosphere. Melting points were taken in open-
end capillary tubes. Chemical shifts were reported relative to
tetramethylsilane for 1H and 13C. 1H NMR data are reported as
follows: chemical shift, multiplicity (s = singlet, d = doublet,
t = triplet, q = quartet, quint = quintet, br = broad, m = multi-
plet), coupling constants (Hz), integration. Mass spectra (MS)
were obtained at an ionizing voltage of 70 eV. HRMS were per-
formed on a time-of-flight mass spectrometer equipped with
an ESI source. Reactions were monitored by thin-layer
chromatography, carried out on 0.25 mm silica gel plates.
Flash column chromatography was performed using silica gel.
Characterization data for those compounds not described in
the literature are provided.
Copper(I) chloride, sodium tert-butoxide, B2pin2, xantphos,
3,3-dimethylbutyne, heptyne, phenylacetylene, p-methoxyl-
phenylacetylene, p-nitrophenylacetylene, trimethylsilylacetylene,
oxazolidin-2-one, (S)-4-phenyl-oxazolidin-2-one, (S)-4-benzylox-
azolidin-2-one, pyrrolidin-2-one and 3-acetylindole were pur-
chased from commercial sources and used as received.
Alkynyl bromides,24 2-bromotrimethylsilylethyne,25 old
compounds 1a–j, 1l–o and new compounds 1k and 1p were
prepared according to the reported procedure.26 Unless other-
wise noted, commercially available reagents were used without
purification. Toluene was freshly distilled from sodium/benzo-
phenone ketyl.
18.3, 14.0; MS (ESI) m/z (%) 254 (M+ + 1, 100); IR ν (KBr, cm−1
)
3101, 3043, 2959, 2930, 2854, 2268, 1751, 1649, 1532,
1460, 1375, 1298, 1219, 1141, 1101, 1010. Anal. calcd for
C17H19NO: C 80.60, H 7.56, N 5.53. Found: C 80.72, H 7.37,
N 5.19.
4.1.2. Cu(I)-catalyzed hydroboration of alkynamides with
B2pin2
Typical procedure. An oven-dried Schlenk tube was charged
with CuCl (0.05 mmol), t-BuONa (0.075 mmol), B2pin2
(0.55 mmol), L1 (xantphos) or L2 (LB-Phos·HBF4) (0.06 mmol),
and alkynamides 1 (0.5 mmol) and the Schlenk tube was purged
and backfilled with nitrogen (three times). To this mixture were
added toluene (1.5 mL) and MeOH (40 μL, 0.6 mmol), and the
resulting solution was stirred at room temperature until no start-
ing material was detected by TLC monitoring. Then, the reaction
was quenched by the addition of saturated aqueous NH4Cl
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(5.0 mL) and extracted with Et2O (20 mL × 3). The combined
(4) 3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-2-
organic extracts were washed with brine (5 mL) and dried over heptenyl]oxazolidin-2-one (Z-2d)
anhydrous Na2SO4. Filtration, evaporation, and chromato-
The reaction of CuCl (5.4 mg, 0.05 mmol), xantphos
graphy on silica gel column with petroleum ether (PE) and (34.2 mg, 0.06 mmol), t-BuONa (7.3 mg, 0.075 mmol), 1d
ethyl acetate (EA) as the eluent afforded the desired product (90.6 mg, 0.5 mmol), B2pin2 (140.0 mg, 0.55 mmol), and
(Z)-2.
(1) 3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-2- ture for 12 h afforded Z-2d (117.4 mg, yield: 76%) as a white
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
1
phenylethenyl]oxazolidin-2-one (Z-2a)
solid. Mp 78–79 °C (n-hexane–EA). H NMR (400 MHz, CDCl3)
The reaction of CuCl (5.1 mg, 0.05 mmol), xantphos δ 7.09 (s, 1 H), 4.40 (dd, J1 = 8.9 Hz, J2 = 7.0 Hz, 1 H), 4.06 (dd,
(34.6 mg, 0.06 mmol), t-BuONa (7.3 mg, 0.075 mmol), 1a J1 = 8.9 Hz, J2 = 7.0 Hz, 1 H), 2.20 (t, J = 7.5 Hz, 2 H), 1.42–1.20
(93.6 mg, 0.5 mmol), B2pin2 (139.9 mg, 0.55 mmol), and (m, 20 H), 0.88 (t, J = 6.7 Hz, 3 H); 13C NMR (100 MHz, CDCl3)
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- δ 156.7, 133.1, 83.2, 62.2, 45.0, 31.7, 31.3, 26.9, 24.7, 22.6, 14.0;
ture for 6.0 h afforded Z-2a (132.4 mg, yield: 80%) as a white MS (ESI) m/z (%) 310 (M+ + 1, 48.7), 322 (M+ + Na, 100); IR
solid. Mp 120–121 °C (n-hexane–EA). 1H NMR (400 MHz, ν (KBr, cm−1) 2929, 2866, 1748, 1628, 1489, 1376, 1283, 1219,
CDCl3) δ 7.42–7.38 (m, 2 H), 7.37–7.31 (m, 2 H), 7.31–7.25 (m, 1144, 1084, 1040, 963. Anal. calcd for C16H28BNO4: C 62.15, H
1 H), 6.85 (s, 1 H), 4.35 (t, J = 7.9 Hz, 2 H), 3.52 (t, J = 7.9 Hz, 9.13, N 4.53. Found: C 62.06, H 8.89, N 4.30.
2 H), 1.33 (s, 12 H). The carbon directly attached to the boron
(5) 3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-3,3-
atom was not detected by the 13C NMR technique due to quadru- dimethylbutenyl]-oxazolidin-2-one (Z-2e)
polar relaxation. 13C NMR (100 MHz, CDCl3) δ 157.8, 135.4,
The reaction of CuCl (5.1 mg, 0.05 mmol), xantphos
135.2, 129.0, 128.4, 128.3, 84.4, 62.9, 45.1, 24.7; MS (ESI) m/z (27.1 mg, 0.06 mmol), t-BuONa (7.2 mg, 0.075 mmol), 1e
(%) 315 (M+, 30.01), 316 (M+ + 1, 4.53), 257 (100); IR ν (KBr, (84.7 mg, 0.5 mmol), B2pin2 (139.8 mg, 0.55 mmol), and
cm−1) 2984, 2923, 1744, 1628, 1486, 1421, 1328, 1267, 1222, MeOH (40.0 μL, 1.0 mmol) in toluene (1.5 mL) at room temp-
1144, 1083, 1033, 991. Anal. calcd for C17H22BNO4: C 64.78, erature for 24 h afforded Z-2e (23.6 mg, yield: 12%) as a white
H 7.04, N 4.44. Found: C 64.83, H 6.81, N 4.29.
solid. Recovery of 1e was 50%. Mp 153–154 °C (n-hexane–
(2)
3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)- Et2O); 1H NMR (400 MHz, CDCl3) δ 6.39 (s, 1 H), 4.36 (t, J =
2-(4-methoxylphenyl)ethenyl]oxazolidin-2-one (Z-2b)
7.9 Hz, 2 H), 4.43 (t, J = 7.9 Hz, 2 H), 1.26 (s, 12 H), 1.17(s, 9
The reaction of CuCl (5.3 mg, 0.05 mmol), xantphos H); 13C NMR (100 MHz, CDCl3) δ 158.7, 157.8, 84.1, 62.1, 47.9,
(34.2 mg, 0.06 mmol), t-BuONa (7.3 mg, 0.075 mmol), 1b 34.9, 29.6, 24.8; MS (ESI) m/z (%) 318 (M+ + Na, 100), 613 (2M+
(108.6 mg, 0.5 mmol), B2pin2 (140.1 mg, 0.55 mmol), and + Na, 53.33); IR ν (KBr, cm−1) 2964, 1750, 1641, 1473, 1392,
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- 1332, 1265, 1220, 1148, 1084, 1036, 973. Anal. calcd for
ture for 24 h afforded Z-2b (146.6 mg, yield: 85%) as a yellow C15H26BNO4: C 61.03, H 8.88, N 4.75. Found: C 61.01, H 8.85,
solid. Mp 161–162 °C (n-hexane–EA). 1H NMR (400 MHz, N 4.38.
CDCl3) δ 7.43–7.37 (m, 2 H), 6.91–6.87 (m, 2 H), 6.86 (s, 1 H),
4.38 (t, J = 7.9 Hz, 2 H), 3.82 (s, 3 H), 3.60 (t, J = 7.9 Hz, 2 H), rolan-2-yl)-2-phenyl-ethenyl]oxazolidin-2-one (Z-2f)
1.32 (s, 12 H); 13C NMR (100 MHz, CDCl3) δ 159.8, 157.7,
The reaction of CuCl (5.4 mg, 0.05 mmol), xantphos
137.5, 130.7, 127.6, 113.9, 84.3, 62.8, 55.2, 45.2, 24.7; MS (ESI) (35.0 mg, 0.06 mmol), t-BuONa (7.5 mg, 0.075 mmol), 1f
m/z (%) 346 (M+ + 1, 100), 368 (M+ + Na, 59.3); IR ν (KBr, cm−1
(131.4 mg, 0.5 mmol), B2pin2 (139.6 mg, 0.55 mmol), and
(6) (S)-4-Phenyl-3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxabo-
)
2983, 2915, 1752, 1605, 1511, 1415, 1339, 1253, 1174, 1143, MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
1076, 986. Anal. calcd for C18H24BNO5: C 62.63, H 7.01, N 4.06. ture for 36 h afforded Z-2f (146.6 mg, yield: 75%) as a white
1
Found: C 62.66, H 6.88, N 3.81.
(3)
2-(4-nitrophenyl)ethenyl]oxazolidin-2-one (Z-2c)
solid. Mp 89–90 °C (n-hexane–EA). H NMR (400 MHz, CDCl3)
3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)- δ 7.39–7.14 (m, 8 H), 7.02–6.95 (m, 2 H), 6.87 (s, 1 H), 4.95 (t,
J = 8.5 Hz, 1 H), 4.60 (t, J = 8.7 Hz, 1 H), 4.17 (t, J = 8.4 Hz, 1 H),
The reaction of CuCl (5.4 mg, 0.05 mmol), xantphos 1.27 (s, 12 H); 13C NMR (100 MHz, CDCl3) δ 157.1, 138.5,
(34.6 mg, 0.06 mmol), t-BuONa (7.5 mg, 0.075 mmol), 1c 137.3, 135.6, 129.1, 128.5, 128.4, 128.3, 128.2, 127.6, 84.3, 70.7,
(116.1 mg, 0.5 mmol), B2pin2 (139.4 mg, 0.55 mmol), and 60.2, 24.8, 24.5; MS (ESI) m/z (%) 392 (M+ + 1, 100), 414 (M+ +
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- Na, 21.0); IR ν (KBr, cm−1) 3059, 2979, 2927, 1754, 1620, 1454,
ture for 24 h afforded Z-2c (113.4 mg, yield: 63%) as a yellow 1400, 1346, 1241, 1138, 1091, 1023, 973. Anal. calcd for
solid. Mp 191–193 °C (n-hexane–EA). 1H NMR (400 MHz, C23H26BNO4: C 70.60, H 6.70, N 3.58. Found: C 70.68, H 6.74,
CDCl3) δ 8.23–8.17 (m, 2 H), 7.56–7.50 (m, 2 H), 6.83 (s, 1 H), N 3.42.
4.40 (t, J = 7.9 Hz, 2 H), 3.58 (t, J = 7.9 Hz, 2 H), 1.34 (s, 12 H);
(7) (S)-4-Phenyl-3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
13C NMR (100 MHz, CDCl3) δ 157.2, 147.0, 142.1, 131.5, 129.6, lan-2-yl)-2-hepten-yl]oxazolidin-2-one (Z-2g)
123.6, 84.8, 63.0, 45.4, 24.7; MS (ESI) m/z (%) 360 (M+, 25.2),
The reaction of CuCl (5.4 mg, 0.05 mmol), xantphos
383 (M+ + Na, 100); IR ν (KBr, cm−1) 2987, 2913, 1749, 1618, (34.5 mg, 0.06 mmol), t-BuONa (7.0 mg, 0.075 mmol), 1g
1514, 1417, 1344, 1265, 1142, 1079, 1029, 993. Anal. calcd for (128.6 mg, 0.5 mmol), B2pin2 (139.5 mg, 0.55 mmol), and
C17H21BN2O6: C 56.69, H 5.88, N 7.78. Found: C 56.23, H 5.78, MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
N 7.54.
ture for 24 h afforded Z-2g (157.6 mg, yield: 82%) as a white
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solid. Mp 98–99 °C (n-hexane–EA). H NMR (400 MHz, CDCl3) 3 H), 7.21–7.15 (m, 5 H), 7.08 (s, 1 H), 4.46 (s, 2 H), 3.07 (s,
δ 7.43–7.30 (m, 3 H), 7.23–6.92 (m, 2 H), 6.96 (s, 1 H), 5.27 (dd, 3 H), 1.29 (s, 12 H); 13C NMR (100 MHz, CDCl3) δ 143.8, 136.0,
J1 = 8.5 Hz, J2 = 3.8 Hz, 1 H), 4.65 (t, J = 8.5 Hz, 1 H), 4.12 (dd, 134.6, 129.8, 129.0, 128.9, 128.3, 128.1, 127.7, 84.3, 52.9, 39.9,
J1 = 8.4 Hz, J2 = 3.8 Hz, 1 H), 2.00–1.86 (m, 2 H), 1.28–0.93 (m, 24.8; MS (ESI) m/z (%) 414 (M+ + 1, 26.67), 436 (M+ + Na, 100);
18 H), 0.84 (t, J = 7.1 Hz, 3 H); 13C NMR (100 MHz, CDCl3) δ IR ν (KBr, cm−1) 3064, 3031, 2984, 2934, 1626, 1455, 1382,
156.6, 139.1, 131.2, 129.3, 128.6, 125.4, 83.2, 70.3, 59.8, 31.9, 1333, 1141, 1050, 957. Anal. calcd for C22H28BNO4S: C 63.93, H
29.9, 27.7, 24.6, 22.6, 14.0; MS (ESI) m/z (%) 386 (M+ + 1, 100), 6.83, N 3.39. Found: C 63.74, H 6.80, N 3.26.
408 (M+ + Na, 39.1); IR ν (KBr, cm−1) 2983, 2952, 2861, 1748,
1632, 1372, 1312, 1212, 1144, 1080, 1044. Anal. calcd for oxaborolan-2-yl)ethenyl]methanesulfonamide (Z-2j)
(11) (Z)-N-Benzyl-N-[2-phenyl-1-(4,4,5,5-tetramethyl-1,3,2-di-
C22H32BNO4: C 68.58, H 8.37, N 3.64. Found: C 68.44, H 8.10,
N 3.51.
The reaction of CuCl (4.9 mg, 0.05 mmol), LB-Phos·HBF4
(27.3 mg, 0.06 mmol), t-BuONa (7.5 mg, 0.075 mmol), 1j
(8) (S)-4-Benzyl-3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro- (142.6 mg, 0.5 mmol), B2pin2 (140.1 mg, 0.55 mmol), and
lan-2-yl)-2-phenyl-ethenyl]oxazolidin-2-one (Z-2h) MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
The reaction of CuCl (5.0 mg, 0.05 mmol), xantphos ture for 12 h afforded Z-2j (206.4 mg, yield: 100%) as a white
(34.2 mg, 0.06 mmol), t-BuONa (7.4 mg, 0.075 mmol), 1h solid.
(138.6 mg, 0.5 mmol), B2pin2 (140.0 mg, 0.55 mmol), and
(12) (Z)-N-Benzyl-N-[1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- lan-2-yl)heptenyl]-methanesulfonamide (Z-2k)
ture for 24 h afforded Z-2h (151.9 mg, yield: 75%) as a colorless
The reaction of CuCl (5.4 mg, 0.05 mmol), LB-Phos·HBF4
liquid. 1H NMR (400 MHz, CDCl3) δ 7.50–7.42 (m, 2 H), (27.2 mg, 0.06 mmol), t-BuONa (7.1 mg, 0.075 mmol), 1k
7.41–7.29 (m, 3 H), 7.23–7.14 (m, 3 H), 7.00 (s, 1 H), 6.86–6.74 (139.5 mg, 0.5 mmol), B2pin2 (139.4 mg, 0.55 mmol), and
(m, 2 H), 4.21–4.01 (m, 3 H), 2.91 (dd, J1 = 13.6 Hz, J2 = 3.4 Hz, MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
1 H), 2.49 (dd, J1 = 13.4 Hz, J2 = 9.3 Hz, 1 H), 1.34 (s, 12 H); 13
C
ture for 18 h afforded Z-2k (143.8 mg, yield: 71%) as a white
1
NMR (100 MHz, CDCl3) δ 157.1, 137.1, 136.0, 135.4, 129.1, solid. Mp 97–98 °C (n-hexane–EA). H NMR (400 MHz, CDCl3)
128.9, 128.6, 128.5, 128.4, 126.8, 84.4, 67.7, 56.7, 38.4, 25.0, δ 7.32–7.20 (m, 5 H), 6.50 (t, J = 7.2 Hz, 1 H), 4.52 (s, 2 H), 2.98
24.5; MS (ESI) m/z (%) 405 (M+, 46.56), 428 (M+ + Na, 100); IR ν (s, 3 H), 2.05 (q, J = 7.6 Hz, 2 H), 1.30 (s, 12 H), 1.20–1.10 (m,
(KBr, cm−1) 3060, 2979, 2930, 1755, 1627, 1490, 1408, 1231, 2 H), 1.08–0.98 (m, 2 H), 0.96–0.86 (m, 2 H), 0.80 (t, J = 7.2 Hz,
1142, 1081, 1030, 974. HRMS calcd for C24H29BNO4 (M + H)+: 3 H); 13C NMR (100 MHz, CDCl3) δ 157.0, 136.6, 129.3, 128.2,
406.2184. Found: 406.2196.
(9) (S)-4-Benzyl-3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro- (ESI) m/z (%) 408 (M+ + 1, 100), 430 (M+ + Na, 45.2); IR ν (KBr,
lan-2-yl)-2-hepten-yl]oxazolidin-2-one (Z-2i)
cm−1) 2973, 2932, 2865, 1633, 1456, 1380, 1328, 1270, 1140,
127.6, 84.1, 53.3, 38.3, 31.6, 29.3, 27.8, 24.8, 22.4, 13.9; MS
The reaction of CuCl (5.3 mg, 0.05 mmol), xantphos 1053, 981. Anal. calcd for C21H34BNO4S: C 61.91, H 8.41,
(34.9 mg, 0.06 mmol), t-BuONa (7.5 mg, 0.075 mmol), 1i N 3.44. Found: C 61.93, H 8.19, N 3.16.
(135.6 mg, 0.5 mmol), B2pin2 (140.1 mg, 0.55 mmol), and
(13) N-Benzyl-N-[1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- 2-yl)ethenyl]methanesulfonamide (2l)
ture for 18 h afforded Z-2i (163.6 mg, yield: 82%) as a white
solid. Mp 86–87 °C (n-hexane–EA). H NMR (400 MHz, CDCl3) (27.0 mg, 0.06 mmol), t-BuONa (7.6 mg, 0.075 mmol), 1l
The reaction of CuCl (5.3 mg, 0.05 mmol), LB-Phos·HBF4
1
δ 7.38–7.24 (m, 3 H), 7.20–7.14 (m, 2 H), 6.96 (s, 1 H), (104.5 mg, 0.5 mmol), B2pin2 (140.2 mg, 0.55 mmol), and
4.50–4.40 (m, 1 H), 4.22–4.13 (m, 2 H), 3.17 (dd, J1 = 13.8 Hz, MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
J2 = 3.3 Hz, 1 H), 2.63 (dd, J1 = 13.8 Hz, J2 = 10.1 Hz, 1 H), ture for 6 h afforded 2l (124.7 mg, yield: 74%) as a colorless
2.38–2.20 (m, 2 H), 1.54–1.40 (m, 2 H), 1.38–1.30 (m, 4 H), 1.27 oil. 1H NMR (400 MHz, CDCl3) δ 7.33–7.23 (m, 5 H), 5.04 (s,
(s, 12 H), 0.90 (t, J = 6.9 Hz, 3 H); 13C NMR (100 MHz, CDCl3) δ 1 H), 4.98 (s, 1 H), 4.78 (s, 2 H), 3.09 (s, 3 H), 1.31 (s, 12 H);
156.1, 135.3, 131.8, 129.2, 129.0, 127.3, 83.4, 65.8, 56.8, 37.6, 13C NMR (100 MHz, CDCl3) δ 136.1, 128.5, 127.3, 127.0, 112.4,
31.8, 29.4, 28.0, 24.8, 24.7, 22.6, 14.0; MS (ESI) m/z (%) 400 84.4, 50.3, 39.8, 24.7; MS (ESI) m/z (%) 360 (M+ + Na, 100); IR
(M+ + 1, 48.7), 422 (M+ + Na, 100); IR ν (KBr, cm−1) 2958, 1751, ν (neat, cm−1) 3036, 2981, 2934, 1595, 1455, 1408, 1326, 1214,
1621, 1379, 1337, 1266, 1218, 1144, 1086, 1002, 965. Anal. 1144, 1984, 1061, 959. HRMS calcd for C16H24BNNaO4S
calcd for C23H34BNO4: C 69.18, H 8.58, N 3.51. Found: C 69.14, (M + Na)+: 360.1411. Found: 360.1407.
H 8.34, N 3.34.
(10) (Z)-N-Benzyl-N-[2-phenyl-1-(4,4,5,5-tetramethyl-1,3,2-di- oxaborolan-2-yl)ethenyl]-4-methylbenzenesulfonamide (Z-2m)
oxaborolan-2-yl)ethenyl]methanesulfonamide (Z-2j) The reaction of CuCl (10.3 mg, 0.10 mmol), LB-Phos·HBF4
(14) (Z)-N-Benzyl-N-[2-phenyl-1-(4,4,5,5-tetramethyl-1,3,2-di-
The reaction of CuCl (5.0 mg, 0.05 mmol), xantphos (54.5 mg, 0.12 mmol), t-BuONa (14.6 mg, 0.15 mmol), 1m
(34.6 mg, 0.06 mmol), t-BuONa (7.4 mg, 0.075 mmol), 1j (180.5 mg, 0.5 mmol), B2pin2 (140.2 mg, 0.55 mmol), and
(142.4 mg, 0.5 mmol), B2pin2 (139.5 mg, 0.55 mmol), and MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera-
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- ture for 72 h afforded Z-2m (220.1 mg, yield: 90%) as a white
ture for 24 h afforded Z-2j (78.4 mg, yield: 38%) as a white solid. Recovery of 1m was 6%. Mp 138–139 °C (n-hexane–EA).
solid. Recovery of 1j was 56%. Mp 122–123 °C (n-hexane–EA). 1H NMR (400 MHz, CDCl3) δ 7.89–7.82 (m, 2 H), 7.51–7.44 (m,
1H NMR (400 MHz, CDCl3) δ 7.62–7.56 (m, 2 H), 7.35–7.27 (m, 2 H), 7.32–7.26 (m, 2 H), 7.25–7.18 (m, 3 H), 7.15–7.08 (m,
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5 H), 7.07 (s, 1 H), 4.52 (s, 2 H), 2.43 (s, 3 H), 1.14 (s, 12 H); 13
C
(18)
3-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-
NMR (100 MHz, CDCl3) δ 145.7, 143.0, 136.7, 135.9, 134.8, 3,3-dimethylbutenyl]oxazolidin-2-one (Z-2e)
130.1, 129.3, 129.2, 128.9, 128.2, 127.9, 127.4, 83.8, 52.4, 24.6,
The reaction of CuCl (5.1 mg, 0.05 mmol), LB-Phos·HBF4
21.5; MS (ESI) m/z (%) 490 (M+ + 1, 100), 512 (M+ + Na, 62.2); (27.1 mg, 0.06 mmol), t-BuONa (7.2 mg, 0.075 mmol), 1e
IR ν (KBr, cm−1) 3055, 3026, 3000, 2971, 1621, 1494, 1447, (84.7 mg, 0.5 mmol), B2pin2 (139.8 mg, 0.55 mmol), and
1398, 1333, 1161, 1144, 1047, 981. Anal. calcd for MeOH (40.0 μL, 1.0 mmol) in toluene (1.5 mL) at room temp-
C28H32BNO4S: C 68.71, H 6.59, N 2.86. Found: C 68.81, H 6.52, erature for 24 h afforded Z-2e (139.6 mg, yield: 71%) as a white
N 2.63.
(15) N-Benzyl-N-[1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)ethenyl]-4-methylbenzenesulfonamide (2n)
The reaction of CuCl (5.2 mg, 0.05 mmol), LB-Phos·HBF4 ethenyl]oxazolidin-2-one (Z-2h)
solid.
4.1.3. Large scale reactions. (1) Synthesis of (S)-4-benzyl-
3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-phenyl-
(27.2 mg, 0.06 mmol), t-BuONa (7.1 mg, 0.075 mmol), 1n
An oven-dried Schlenk tube was charged with CuCl (20.6 mg,
(142.5 mg, 0.5 mmol), B2pin2 (139.4 mg, 0.55 mmol), and 0.2 mmol), t-BuONa (28.0 mg, 0.3 mmol), B2pin2 (1.1179 g,
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- 4.4 mmol), xantphos (138.4 mg, 0.24 mmol), and 1h (1.1082 g,
ture for 12 h afforded 2n (175.5 mg, yield: 85%) as a colorless 4.0 mmol) and the Schlenk tube was purged and backfilled with
1
oil. H NMR (400 MHz, CDCl3) δ 7.82–7.78 (m, 2 H), 7.32–7.27 nitrogen (three times). To this mixture were added toluene
(m, 2 H), 7.26–7.18 (m, 5 H), 5.15 (s, 1 H), 5.02 (s, 1 H), 4.52 (s, (13.0 mL) and MeOH (0.32 mL, 8.0 mmol), and the resulting
2 H), 2.42 (s, 3 H), 1.26 (s, 12 H); 13C NMR (100 MHz, CDCl3) δ solution was stirred at room temperature until no starting
143.4, 135.7, 135.6, 129.5, 128.3, 127.8, 127.4, 127.2, 116.5, material was detected by TLC monitoring. Then, the reaction
84.0, 49.8, 24.6, 21.5; MS (ESI) m/z (%) 414 (M+ + 1, 44.6), 436 was quenched by the addition of saturated aqueous NH4Cl
(M+ + Na, 100), 452 (M+ + K, 33.8); IR ν (neat, cm−1) 3132, (5.0 mL) and extracted with Et2O (20 mL × 3). The combined
2977, 2927, 1618, 1401, 1333, 1162, 1139, 1086, 815. HRMS organic extracts were washed with brine (5.0 mL) and dried
calcd for C22H29BNO4S (M + H)+: 414.1905. Found: 414.1900.
(16) 1-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-2- graphy on silica gel (eluent: petroleum ether–ethyl acetate =
over anhydrous Na2SO4. Filtration, evaporation, and chromato-
phenylethenyl-1H-indol-3-yl]ethanone (Z-2o)
10/1) afforded Z-2h (1.2509 g, yield: 77%) as a white solid.
(2) (S)-4-Benzyl-3-[(Z)-1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
The reaction of CuCl (5.3 mg, 0.05 mmol), LB-Phos·HBF4
(26.9 mg, 0.06 mmol), t-BuONa (7.5 mg, 0.075 mmol), 1o lan-2-yl)heptenyl]oxazolidin-2-one (Z-2i)
(129.6 mg, 0.5 mmol), B2pin2 (140.2 mg, 0.55 mmol), and
The reaction of CuCl (20.1 mg, 0.2 mmol), xantphos
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- (138.6 mg, 0.24 mmol), t-BuONa (28.8 mg, 0.3 mmol), 1i
ture for 30 h afforded Z-2o (154.8 mg, yield: 80%) as a white (1.0842 g, 4.0 mmol), B2pin2 (1.1175 g, 4.4 mmol), and MeOH
solid. Mp 137–138 °C (n-hexane–EA). 1H NMR (400 MHz, (0.32 ml, 8.0 mmol) in toluene (13.0 mL) at room temperature
CDCl3) δ 8.39 (d, J = 4.8 Hz, 1 H), 7.63 (s, 1 H), 7.47 (s, 1 H), for 18 h afforded Z-2i (1.3566 g, yield: 85%) as a white solid.
7.32–7.22 (m, 1 H), 7.21–7.02 (m, 5 H), 6.85–6.73 (m, 2 H), 2.47
4.1.4. Synthetic application of alkenylamide boronates:
(s, 3 H), 1.31 (s, 12 H); 13C NMR (100 MHz, CDCl3) δ 193.3, synthesis of α,β-disubstituted (Z)-alkenamides via Suzuki–
142.9, 136.0, 134.7, 133.3, 129.5, 129.4, 128.6, 126.2, 123.1, Miyauracoupling. (1) 3–[(Z)-1-(4-Acetylphenyl)-2-phenylethenyl]-
122.5, 122.3, 118.3, 111.5, 84.8, 27.6, 24.7; MS (ESI) m/z (%) oxazolidin-2-one (Z-5a)
387 (M+, 100); IR ν (KBr, cm−1) 3114, 2979, 1651, 1523, 1459,
The reaction of Pd(OAc)2 (5.7 mg, 0.025 mmol), PPh3
1379, 1351, 1208, 1139, 1093, 970. Anal. calcd for C24H26BNO3: (6.6 mg, 0.025 mmol), K2CO3 (138.2 mg, 1.0 mmol) and Z-2a
C 74.43, H 6.77, N 3.62. Found: C 74.09, H 6.66, N 3.24. (157.7 mg, 0.5 mmol) in THF (1.5 mL) refluxed for 6 h to
(17) 1-[(Z)-1-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-2- afford Z-5a (128.9 mg, yield: 84%) as a white solid. Mp
heptenyl-1H-indol-3-yl]ethanone (Z-2p)
147–148 °C (n-hexane–EA). 1H NMR (400 MHz, CDCl3) δ
The reaction of CuCl (5.4 mg, 0.05 mmol), LB-Phos·HBF4 8.05–7.95 (m, 2 H), 7.59–7.53 (m, 2 H), 7.49–7.36 (m, 4 H),
(27.3 mg, 0.06 mmol), t-BuONa (7.2 mg, 0.075 mmol), 1p 7.36–7.28 (m, 1 H), 6.96 (s, 1 H), 4.48 (dd, J1 = 8.8 Hz, J2
=
(124.8 mg, 0.5 mmol), B2pin2 (139.9 mg, 0.55 mmol), and 7.4 Hz, 2 H), 3.69 (dd, J1 = 8.7 Hz, J2 = 7.4 Hz, 2 H), 2.62 (s,
MeOH (40 μL, 1.0 mmol) in toluene (1.5 mL) at room tempera- 3 H); 13C NMR (100 MHz, CDCl3) δ 197.3, 156.3, 141.0, 137.0,
ture for 36 h afforded Z-2p (124.0 mg, yield: 66%) as a white 134.7, 133.7, 128.88, 128.85, 128.76, 128.6, 128.4, 125.9, 62.6,
1
solid. Mp 90–91 °C (n-hexane–EA). H NMR (400 MHz, CDCl3) 45.2, 26.6; MS (ESI) m/z (%) 308 (M+ + 1, 8.7), 330 (M+ + Na,
δ 8.42–8.34 (m, 1 H), 7.87 (s, 1 H), 7.48–7.40 (m, 2 H), 100); IR ν (KBr, cm−1) 3056, 2897, 1758, 1674, 1597, 1417,
7.36–7.28 (m, 2 H), 2.54 (s, 3 H), 2.35 (t, J = 7.7 Hz, 2 H), 1354, 1268, 1172, 1076, 1033, 958. Anal. calcd for C19H17NO3:
1.58–1.48 (m, 2 H), 1.33 (s, 12 H), 1.32–1.22 (m, 4 H), 0.86 (t, J C 74.25, H 5.58, N 4.56. Found: C 74.19, H 5.38, N 4.21.
= 7.0 Hz, 3 H); 13C NMR (100 MHz, CDCl3) δ 193.2, 137.3,
(2) (Z)-N-Benzyl-N-[2-phenyl-1-(4-acetylphenyl)ethenyl]meth-
133.9, 132.1, 125.7, 123.8, 123.2, 122.5, 118.6, 110.6, 83.9, 31.8, anesulfonamide (Z-5j)
29.1, 28.4, 27.5, 24.7, 22.4, 13.9; MS (ESI) m/z (%) 382 (M+ + 1,
The reaction of Pd(OAc)2 (5.6 mg, 0.025 mmol), PPh3
100); IR ν (KBr, cm−1) 2969, 2931, 2868, 1660, 1532, 1460, (6.5 mg, 0.025 mmol), K2CO3 (138.1 mg, 1.0 mmol) and Z-2j
1372, 1322, 1213, 1128, 1008, 962. Anal. calcd for C23H32BNO3: (206.5 mg, 0.5 mmol) in THF (1.5 mL) reflux for 24 h afforded
C 72.45, H 8.46, N 3.67. Found: C 72.64, H 8.24, N 3.34.
Z-5j (184.3 mg, yield: 91%) as a white solid. Mp 141–142 °C
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(n-hexane–EA). 1H NMR (400 MHz, CDCl3) δ 7.96–7.88 (m,
2 H), 7.45–7.40 (m, 2 H), 7.40–7.22 (m, 10 H), 6.84 (s, 1 H),
4.48 (s, 1 H), 2.60 (s, 3 H), 2.49 (s, 3 H); 13C NMR (100 MHz,
CDCl3) δ 197.4, 143.1, 137.7, 136.9, 135.8, 135.1, 130.9, 130.0,
128.9, 128.8, 128.70, 128.65, 128.5, 127.7, 53.2, 42.8, 26.7; MS
(ESI) m/z (%) 406 (M+ + 1, 29.0), 428 (M+ + Na, 100); IR ν (KBr,
cm−1) 3113, 3066, 3032, 2933, 1673, 1601, 1408, 1332, 1270,
1147, 1096, 1036, 976. Anal. calcd for C19H17NO3: C 71.09,
H 5.72, N 3.45. Found: C 71.02, H 5.52, N 3.18.
7 For a copper-catalyzed formal carboboration of alkynes,
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Financial support from the General Program of Natural
Science Foundation of Jiangsu Provincial Universities (no.
12KJB150011), Jiangsu Provincial Technology Support Program
(no. BE2012363) and National Natural Science Foundation of
China (no. 21373112) is greatly appreciated.
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rhombic, space group Pbca, final R indices [I > 2σ(I)]: R1 =
0.0680, wR2 = 0.1238, R indices (all data): R1 = 0.1949, wR2
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90.00°, V = 4563.4(16) Å3, T = 293(2) K, Z = 8, reflections col-
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vations [I> 2σ(I)]: 1686, parameters: 262. CCDC 944761
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