Platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynesa

Article abstract of DOI:10.1002/cjoc.201400174

A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes is described. The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yields with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl₂/(S)-BINAP and an excess of zinc powder. The products were obtained exclusively with the relative cis-configuration of the ring substituents and the prevalent (1R,2S)-configuration of the stereocenters, as determined by single crystal X-ray diffraction analysis. Copyright

Full text of DOI:10.1002/cjoc.201400174

FULL PAPER
DOI: 10.1002/cjoc.201400174
Platinum-Catalyzed Asymmetric Ring-opening Reaction of
Oxabenzonorbornadiene with Terminal Alkynes
Yuhua Long,* Han Jiang, Zhifu Zou, Kaixuan Chen, and Yali Fang
School of Chemistry and Environment, South China Normal University, Guangzhou, Guangdong 510006, China
A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes
is described. The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yields
with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl2/(S)-BINAP and an excess of zinc
powder. The products were obtained exclusively with the relative cis-configuration of the ring substituents and the
prevalent (1R,2S)-configuration of the stereocenters, as determined by single crystal X-ray diffraction analysis.
Keywords platinum-catalyzed, asymmetric catalysis, ring-opening reaction, oxabenzonorbornadiene, terminal
alkyne
Introduction
cient catalysts for the reaction of oxabicyclic alkenes
with terminal alkynes to give mainly ring-opening
product together with addition product in a racemic way.
However, there is no report on platinum-catalyzed
asymmetric ring-opening reaction of oxabenzonorborna-
diene with terminal acetylene. Herein, we report the
asymmetric ring-opening reaction of oxabenzonorbor-
nadiene with terminal acetylenes catalyzed by
Pt(COD)Cl2 (COD＝cyclooctadiene) and optically pure
phosphines. This reaction offers a convenient method
for the construction of optically active cis-2-alkynyl-
1,2-dihydronaphthalen-1-ols in one pot from easily ac-
cessible starting materials.
Atom economical asymmetric ring-opening (ARO)
reactions can generate two chiral center in one step in
high yields and with high enantiomeric excesses.[1-3]
Oxabenzonorbornadiene can be feasibly activated by
transition metal complexes, and can undergo ring-
opening reaction to yield dihydronaphthalene skeleton
which is found in a wide range of naturally occurring
molecules.[4-7] Many metal catalysts have been investi-
gated for the ring-opening of oxabenzonorbornadiene,
such as Fe,[8] Ni,[9-11] Cu,[12,13] Ru,[14-16] Rh,[17,18] Pd,[19,20]
Ir,[21] etc. Very recently our research group[22] has de-
veloped the platinum catalyzed ring-opening addition of
arylboronic acids to oxabenzonorbornadienes. Many
nucleophiles, including organoboronic acids,[23,24] dial-
kylzinc reagents,[25] organolithium reagents,[26,27] or-
ganozinc halides,[28-30] Grignard reagents,[29] and al-
kynes[9,32-34] have been applied successfully in ARO.
Among these nucleophiles, alkynes are appealing car-
bon nucleophiles, because the furnished acetylene motif
can undertake potential transformation to various bioac-
tive compounds and new materials. Cheng and co-
workers[9] have reported the use of terminal alkynes for
the nickel-catalyzed ring-opening reactions of the oxa-
and azabicyclic alkenes, where racemic 2-alkynyl-1,2-
dihydronaphthalene derivatives were produced in high
yields with high diastereoselectivity. Hayashi and co-
workers[32] have reported the highly enantioselective
alkynylation of azabenzonorbornadienes by use of a
sterically bulky silylacetylene and an axially chiral
biarylbisphosphine/rhodium catalyst. Very recently,
Hou and co-workers[35] found palladacycles to be effi-
Experimental
General methods
All flasks were flame-dried under a stream of nitro-
gen and cooled before use. Solvents and solutions were
transferred with syringes and cannulae using standard
inert atmosphere techniques. NMR spectra were re-
corded at 400 MHz using a Varian INOVA NMR spec-
trometer with CDCl3 as reference standard (δ 7.26 for
1H NMR and δ 77.16 for 13C NMR). IR spectra were
obtained using a Nicolet DX FT-IR spectrometer as a
KBr pellet. HRMS spectra were recorded on a Thermo
Finnigan MAT95-XP high-resolution mass spectrometer
(EI). Melting points were taken on an XT4 binocular
micromelting point apparatus. HPLC analysis was per-
formed on an Agilent 1100 Series HPLC with a Chiral-
cel AD-H or OD-H column. Crystal structure determi-
nation was carried out on a Bruker SMART-1000 X-ray
*
E-mail: longyh@scnu.edu.cn; Tel.: 0086-020-39310258
Received March 24, 2014; accepted May 20, 2014; published online June 13, 2014.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201400174 or from the author.
Chin. J. Chem. 2014, 32, 613—618
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(1R,2S)-2-[(2-(3-Chlorophenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2c): Following the general
procedure, 2c was obtained as a light yellow solid (24.6
mg, 44%), Rf＝0.18 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶10). m.p. 82－84 ℃. The ee
was determined to be 43% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
90∶10, 1.0 mL/min, λ＝254 nm). Retention times were
diffraction apparatus. DME was distilled from sodium
benzophenone ketyl and stored. THF, dioxane, toluene,
and THP were distilled from sodium benzophenone
ketyl immediately prior to use. CH3CN was distilled
from calcium hydride. DMSO was dried over MgSO4
and stored over activated molecular sieves. Preparation
of oxabenzonorbornadiene 1a followed reference.[36]
1
General procedure for the asymmetric ring-opening
reaction of oxabenzonorbornadiene 1 with terminal
acetylene
9.814 min (major) and 15.576 min (minor). H NMR
(400 MHz, CDCl3) δ: 7.45 (d, J＝6.5 Hz, 1H), 7.38 (s,
1H), 7.28 (dt, J＝13.9, 6.5 Hz, 4H), 7.19 (d, J＝7.7 Hz,
1H), 7.14 (d, J＝6.5 Hz, 1H), 6.59 (d, J＝9.3 Hz, 1H),
5.97 (dd, J＝9.3, 3.5 Hz, 1H), 4.84 (s, 1H), 3.79 (s, 1H),
2.36 (s, 1H); 13C NMR (100 MHz, CDCl3) δ: 135.22,
134.02, 131.80, 131.74, 130.00, 129.47, 128.73, 128.50,
128.24, 128.09, 127.07, 126.84, 125.37, 124.57, 87.61,
82.61, 69.32, 35.37; IR (KBr) ν: 3320, 2960, 2918, 2852,
2370, 2332, 1598, 1432, 1050, 785 cm−1; HRMS (EI)
calcd for C18H13OCl 280.0649; found 280.0648.
An oven-dried Schlenk tube was charged with
Pt(COD)Cl2 (3.7 mg, 5 mol%) and (S)-BINAP (6.2 mg,
5.0 mol%) in anhydrous toluene (1.0 mL). After they
were stirred for about 30 min, 1 (0.2 mmol), Zn (0.55
mmol) and acetylene (0.4 mmol) were added. The reac-
tion mixture was heated with stirring at 90 ℃. After the
reaction was finished, the solvent was removed in vac-
cum and the crude mixture was purified by column
chromatography on silica gel to give the target product
2.
(1R,2S)-2-[(2-(2-Chlorophenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2d): Following the general
procedure, 2c was obtained as a light yellow solid (19.6
mg, 35%), Rf＝0.30 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶6). m.p. 92－93 ℃. The ee was
determined to be 50% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
90∶10, 1.0 mL/min, λ＝254 nm. Retention times were
(1R,2S)-2-(2-Phenyl-1-ethynyl)-1,2-dihydro-1-naph-
thalenol (2a): Following the general procedure, 2a was
obtained as a yellow oil (24.6 mg, 50%), Rf＝0.28 on
silica gel (ethyl acetate/petroleum ether, V∶V＝1∶10).
The ee was determined to be 92% using HPLC analysis
on a Chiralcel OD-H column (hexane/2-propanol, V∶
V＝80∶20, 1.0 mL/min, λ＝254 nm). Retention times
1
9.467 min (major) and 10.952 min (minor). H NMR
1
were 6.658 min (minor) and 10.993 min (major). H
(400 MHz, CDCl3) δ: 7.52－7.46 (m, 1H), 7.42 (d, J＝
7.3 Hz, 1H), 7.35 (d, J＝7.8 Hz, 1H), 7.32－7.26 (m,
2H), 7.18 (dt, J＝13.8, 7.2 Hz, 3H), 6.60 (d, J＝9.4 Hz,
1H), 6.01 (dd, J＝9.3, 3.8 Hz, 1H), 4.92 (t, J＝6.2 Hz,
1H), 3.84 (s, 1H), 2.57 (d, J＝7.5 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ: 136.06, 135.30, 133.19, 131.92,
129.25, 129.10, 128.59, 128.23, 128.20, 127.01, 126.75,
126.43, 125.11, 122.69, 91.70, 80.95, 69.34, 35.54; IR
(KBr) ν: 3690, 2928, 2924, 2864, 2347, 1620, 1460,
1053, 760, 682 cm−1; HRMS (EI) calcd for C18H13OCl
280.0649; found 280.0649.
NMR (400 MHz, CDCl3) δ: 7.45 (d, J＝4.5 Hz, 1H),
7.40 (d, J＝2.9 Hz, 2H), 7.33－7.21 (m, 5H), 7.14 (s,
1H), 6.58 (d, J＝9.4 Hz, 1H), 5.99 (dd, J＝8.8, 3.1 Hz,
1H), 4.85 (s, 1H), 3.80 (s, 1H), 2.40 (d, J＝6.2 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ: 135.27, 131.91, 131.87,
128.68, 128.27, 128.16, 127.91, 127.20, 126.79, 125.76,
125.02, 122.83, 86.03, 84.12, 69.30, 35.43; IR (KBr) ν:
3414, 3377, 3061, 2922, 1659, 1279, 756, 689 cm−1.
The physical and spectroscopic data of 2a are identical
with those reported previously.[9]
(1R,2S)-2-[(2-(4-Bromophenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2e): Following the general
procedure, 2e was obtained as a light yellow solid (27.2
mg, 42%), Rf＝0.23 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶10). m.p. 156－158 ℃. The ee
was determined to be 71% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
85∶15, 1.0 mL/min, λ＝254 nm. Retention times were
(1R,2S)-2-[(2-(4-Chlorophenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2b): Following the general
procedure, 2b was obtained as a light yellow solid (22.4
mg, 40%), Rf＝0.27 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶10). m.p. 162－164 ℃. The ee
was determined to be 50% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶ V＝
90∶10, 1.0 mL/min, λ＝254 nm). Retention times were
1
1
7.978 min (major) and 10.989 min (minor). H NMR
9.731 min (major) and 14.100 min (minor). H NMR
(400 MHz, CDCl3) δ: 7.45 (d, J＝6.1 Hz, 1H), 7.41 (d,
J＝7.9 Hz, 2H), 7.33－7.22 (m, 4H), 7.15 (d, J＝6.2 Hz,
1H), 6.60 (d, J＝9.3 Hz, 1H), 5.98 (dd, J＝9.1, 2.9 Hz,
1H), 4.85 (t, J＝5.6 Hz, 1H), 3.80 (s, 1H), 2.28 (d, J＝
7.2 Hz, 1H), 2.28 (d, J＝7.2 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ: 135.19, 133.30, 131.80, 131.48, 128.73,
128.21, 128.03, 127.12, 126.83, 125.42, 122.42, 121.80,
87.39, 82.98, 69.28, 35.44; IR (KBr) ν: 3353, 2920,
2852, 2360, 1494, 1420, 1252, 1110, 825, 758 cm−1;
HRMS (EI) calcd for C18H13OBr 324.0144; found
(400 MHz, CDCl3) δ: 7.44 (dd, J＝7.6, 5.4 Hz, 1H),
7.35－7.27 (m, 4H), 7.26－7.22 (m, 2H), 7.16－7.12
(m, 1H), 5.98 (dd, J＝9.5, 3.8 Hz, 1H), 4.85 (dd, J＝7.1,
5.5 Hz, 1H), 3.82－3.78 (m, 1H), 2.31 (d, J＝7.5 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ: 135.21, 134.20,
133.09, 131.81, 128.73, 128.56, 128.21, 128.02, 127.12,
126.83, 125.48, 121.34, 87.20, 82.92, 69.31, 35.41. IR
(KBr) ν: 3354, 3053, 2922, 2852, 2357, 1656, 1483,
1084, 824, 787 cm−1; HRMS (EI) calcd for C18H13OCl
280.0649; found 280.0649.
614
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 613—618

Asymmetric Ring-opening Reaction of Oxabenzonorbornadiene with Terminal Alkynes
324.0145.
(1R,2S)-2-[(2-(4-Nitrophenyl)-1-ethynyl]-1,2-dihy-
(1R,2S)-2-[(2-(4-Propylphenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2i): Following the general
procedure, 2i was obtained as a white solid (24.2 mg,
42%), Rf＝0.13 on silica gel (ethyl acetate/petroleum
ether, V∶V＝1∶10). m.p. 88－89 ℃. The ee was de-
termined to be 63% using HPLC analysis on a Chiralcel
OD-H column (hexane/2-propanol, V∶V＝90∶10, 1.0
mL/min, λ＝254 nm). Retention times were 6.657 min
dro-1-naphthalenol (2f): Following the general proce-
dure, 2f was obtained as a yellow solid (31.4 mg, 54%),
Rf＝0.3 on silica gel (ethyl acetate/petroleum ether, V∶
V＝1∶4). m.p. 151－152 ℃. The ee was determined
to be 61% using HPLC analysis on a Chiralcel OD-H
column (hexane/2-propanol, V ∶V ＝90 ∶10, 1.0
mL/min, λ＝254 nm). Retention times were 26.338 min
1
(major) and 13.103 min (minor). H NMR (400 MHz,
1
(major) and 33.657 min (minor). H NMR (400 MHz,
CDCl3) δ: 7.52－7.43 (m, 1H), 7.34 (d, J＝1.9 Hz, 1H),
7.33－7.28 (m, 3H), 7.15 (dd, J＝6.4, 2.1 Hz, 1H), 7.10
(dd, J＝8.0, 1.8 Hz, 2H), 6.63－6.57 (m, 1H), 6.01 (ddd,
J＝9.4, 3.8, 1.9 Hz, 1H), 4.86 (d, J＝4.8 Hz, 1H), 3.82
(dt, J＝5.7, 2.1 Hz, 1H), 2.57 (t, J＝7.6 Hz, 2H), 1.66－
1.58 (m, 2H), 0.96－0.90 (m, 3H); 13C NMR (100 MHz,
CDCl3) δ: 143.13, 135.25, 131.93, 131.73, 128.63,
128.42, 128.10, 127.81, 127.22, 126.75, 125.87, 119.93,
85.10, 84.34, 69.28, 37.90, 35.45, 24.36, 13.74; IR (KBr)
ν: 3345, 3032, 2924, 2862, 2357, 1506, 1072, 779, 711,
586 cm–1; HRMS (EI) calcd for C21H20O 288.1509;
found 288.1509.
CDCl3) δ: 8.20－8.04 (m, 2H), 7.53 (d, J＝8.7 Hz, 2H),
7.49－7.42 (m, 1H), 7.36－7.27 (m, 2H), 7.20－7.12
(m, 1H), 6.63 (dd, J＝9.5, 1.9 Hz, 1H), 5.99 (dd, J＝9.4,
3.8 Hz, 1H), 4.89 (t, J＝6.0 Hz, 1H), 3.88－3.82 (m,
1H), 2.27 (d, J＝7.5 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ: 146.93, 135.14, 132.61, 131.65, 129.93,
128.86, 128.36, 127.00, 126.94, 124.85, 123.48, 92.41,
82.11, 69.36, 35.53; IR (KBr) ν: 3364, 3063, 2922, 2855,
2359, 2220, 1595, 1528, 1342, 852, 752 cm−1; HRMS
(EI) calcd for C18H13O3N 291.0890; found 291.0890.
(1R,2S)-2-[(2-(4-Methylphenyl)-1-ethynyl]-1,2-
dihydro-1-naphthalenol (2g): Following the general
procedure, 2g was obtained as a white solid (31.2 mg,
60%), Rf＝0.13 on silica gel (ethyl acetate/petroleum
ether, V∶V＝1∶10). m.p. 134－136 ℃. The ee was
determined to be 61% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
85∶15, 1.0 mL/min, λ＝254 nm). Retention times were
(1R,2S)-2-[(2-(4-n-Pentylphenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2j): Following the general
procedure, 2j was obtained as a light yellow solid (32.2
mg, 51%), Rf＝0.13 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶10). m.p. 80－81 ℃. The ee
was determined to be 63% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
85∶15, 1.0 mL/min, λ＝254 nm). Retention times were
1
7.499 min (major) and 13.784 min (minor). H NMR
1
(400 MHz, CDCl3) δ: 7.45 (d, J＝6.2 Hz, 1H), 7.33－
7.25 (m, 4H), 7.13 (d, J＝6.4 Hz, 1H), 7.08 (d, J＝7.6
Hz, 2H), 6.58 (d, J＝9.4 Hz, 1H), 5.99 (dd, J＝9.2, 3.1
Hz, 1H), 4.84 (s, 1H), 3.80 (s, 1H), 2.38 (d, J＝4.8 Hz,
1H), 2.32 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
138.34, 135.24, 131.93, 131.74, 129.01, 128.65, 128.11,
127.81, 127.25, 126.77, 125.88, 119.70, 85.13, 84.29,
69.28, 35.45, 21.49; IR (KBr) ν: 3349, 2910, 2832, 2365,
1504, 1450, 1135, 812, 750 cm−1; HRMS (EI) calcd for
C19H16O 260.1196; found 260.1194.
6.006 min (major) and 10.179 min (minor). H NMR
(400 MHz, CDCl3) δ: 7.50－7.46 (m, 1H), 7.37－7.29
(m, 4H), 7.18－7.14 (m, 1H), 7.11 (d, J＝8.0 Hz, 2H),
6.61 (dd, J＝9.5, 2.0 Hz, 1H), 6.02 (dd, J＝9.5, 3.8 Hz,
1H), 4.87 (t, J＝5.4 Hz, 1H), 2.63－2.56 (m, 2H), 2.42
(d, J＝6.5 Hz, 1H), 1.60 (dt, J＝14.9, 7.5 Hz, 2H),
1.36－1.29 (m, 4H), 0.90 (t, J＝6.9 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ: 143.39, 135.28, 131.95, 131.76,
128.63, 128.38, 128.11, 127.82, 127.23, 126.76, 125.89,
119.90, 85.12, 84.34, 69.29, 35.83, 35.46, 31.41, 30.96,
22.54, 14.07; IR (KBr) ν: 3345, 3032, 2924, 2862, 2357,
1506, 1454, 1072, 779, 712, 595 cm−1; HRMS (EI)
calcd for C23H24O 316.1822; found 316.1822.
(1R,2S)-2-[(2-(4-Ethylphenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2h): Following the general
procedure, 2h was obtained as a light yellow solid (34.0
mg, 62%), Rf＝0.13 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶10). m.p. 72－73 ℃. The ee
was determined to be 51% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
85∶15, 1.0 mL/min, λ＝254 nm). Retention times were
(1R,2S)-2-[(2-(4-Methoxyphenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2k): Following the general
procedure, 2k was obtained as a light yellow solid (18.2
mg, 33%), Rf＝0.23 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶6). m.p. 102－103 ℃. The ee
was determined to be 30% using HPLC analysis on a
Chiralcel OD-H column (hexane/ 2-propanol, V∶V＝
90∶10, 1.0 mL/min, λ＝254 nm). Retention times were
1
6.984 min (major) and 12.778 min (minor). H NMR
(400 MHz, CDCl3) δ: 7.45 (d, J＝7.0 Hz, 1H), 7.33－
7.26 (m, 4H), 7.13－7.09 (m, 3H), 6.58 (d, J＝9.5 Hz,
1H), 5.99 (dd, J＝9.4, 3.6 Hz, 1H), 4.84 (s, 1H), 3.80 (s,
1H), 2.62 (q, J＝7.6 Hz, 2H), 2.39 (d, J＝5.8 Hz, 1H),
1.20 (t, J＝7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
144.67, 135.23, 131.93, 131.83, 128.64, 128.10, 127.82,
127.24, 126.76, 125.88, 119.93, 85.11, 84.32, 69.28,
35.45, 28.80, 15.41; IR (KBr) ν: 3312, 3043, 2973, 2926,
2349, 2310, 1628, 1107, 852, 784 cm−1; HRMS (EI)
calcd for C20H18O 274.1352; found 274.1353.
1
14.129 min (major) and 37.097 min (minor). H NMR
(400 MHz, CDCl3) δ: 7.46 (d, J＝5.8 Hz, 1H), 7.37－
7.25 (m, 4H), 7.14 (d, J＝5.9 Hz, 1H), 6.58 (d, J＝9.4
Hz, 1H), 5.99 (d, J＝6.6 Hz, 1H), 4.84 (s, 1H), 3.78 (s,
4H), 2.40 (d, J＝4.9 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ: 159.49, 135.26, 133.27, 131.93, 128.63,
128.09, 127.76, 127.23, 126.75, 125.96, 114.88, 113.84,
84.32, 84.03, 69.28, 55.28, 35.43; IR (KBr) ν: 3358,
Chin. J. Chem. 2014, 32, 613—618
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Long et al.
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3190, 2955, 2924, 2855, 2361, 2332, 1667, 1458, 1248,
1013, 833 cm−1; HRMS (EI) calcd for C19H16O2
276.1145; found 276.1146.
Table 1 Effect of ligand, and catalyst loading on the asymmet-
ric ring-opening of oxabenzonorbornadiene 1a with phenylacety-
lenea
(1R,2S)-2-[(2-(4-Ethoxyphenyl)-1-ethynyl)-1,2-
dihydro-1-naphthalenol (2l): Following the general
procedure, 2l was obtained as a light yellow solid (29.6
mg, 51%), Rf＝0.38 on silica gel (ethyl acetate/petro-
leum ether, V∶V＝1∶4). m.p. 80－81 ℃. The ee was
determined to be 50% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol, V∶V＝
85∶15, 1.0 mL/min, λ＝254 nm). Retention times were
H
O
Pt(COD)Cl2, ligand
Zn, toluene, 90 oC
+
OH
Ph
Ph
1a
2a
Ligands:
P( -Bu)
t
2
PPh2
PPh2
PPh2
PPh2
PPh2
1
Fe
8.883 min (major) and 15.021 min (minor). H NMR
Fe
(400 MHz, CDCl3) δ: 7.47 (d, J＝6.1 Hz, 1H), 7.38－
7.24 (m, 4H), 7.15 (d, J＝6.1 Hz, 1H), 6.80 (d, J＝8.4
Hz, 2H), 6.59 (d, J＝9.4 Hz, 1H), 6.00 (dd, J＝9.3, 3.4
Hz, 1H), 4.85 (s, 1H), 4.01 (dd, J＝13.8, 6.8 Hz, 2H),
3.81 (s, 1H), 2.42 (s, 1H), 1.41 (t, J＝6.9 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ: 158.90, 135.27, 133.26,
131.95, 128.62, 128.08, 127.75, 127.24, 126.74, 125.99,
114.68, 114.35, 84.21, 84.12, 69.28, 63.47, 35.44, 14.76;
IR (KBr) ν: 3354, 3010, 2955, 2850, 2361, 2332, 1647,
1558, 1248, 1063, 833 cm−1; HRMS (EI) calcd for
C20H18O2 290.1301; found 290.1304.
DPPF
(S)-BINAP
(R)-(S)-PPF-P(t-Bu)2
O
O
O
O
O
O
PAr2
PAr2
P(tol)2
P(tol)2
PPh2
PPh2
O
O
(S)-p-Tol-BINAP
(R)-SEGPHOS
(R)-DRBM-SEGPHOS
PAr2
PAr2
Ar =
Results and Discussion
The reaction of oxabenzonorbornadiene 1 with phe-
nylacetylene was tested in the presence of Pt(COD)Cl2
and bisphosphine ligand (Table 1). Achiral 1,1'-bis(di-
phenylphosphino)ferrocene (DPPF) was first chosen to
validate the catalytic activity of Pt(COD)Cl2. Unfortu-
nately, no reaction occurred (Table 1, Entry 1). Then we
retried the reaction with the addition of zinc powder.
The ring-opening product 2a was obtained in 79% yield
after 2 h (Table 1, Entry 2). Encouraged by this result,
we tested several chiral ligands, and the results were
summarized in Table 1. Among the ligands screened,
(S)-BINAP gave 2a in 50% yield with 92% ee (Table 1,
Entry 6). With (S)-xyl-BINAP as the ligand, the reaction
can give a high ee value (98%), but with a very poor
yield (21%). Substitution of ZnCl2 for Zn caused the
reaction to fail (Table 1, Entry 9). Changing the amount
of Zn from 2.75 to 1.5 or 3.5 equiv. caused lower yield
with lower ee (Table 1, Entries 10 and 11). We next
investigated the effect of catalyst loading on the reaction.
The results indicated that 5 mol% of Pt(COD)Cl2 with 5
mol% of (S)-BINAP gave the best values of yield and
enantioselectivity. Lowering the catalyst loading led to
the decrease in both the yield and ee value. On the other
hand, the increase of the catalyst loading improved nei-
ther the yield nor the ee value evidently (Entries 6, and
10－12).
(S)-(-)-XylBINAP
Pt(COD)Cl2/
Entry
Ligand/mol%
Time/h Yieldf/% eeg/%
mol%
1b DPPF (5)
5
5
24
2
n.r.
79
－
2
3
4
5
DPPF (5)
0
(R)-(S)-PPF-P(t-Bu)2
(5)
5
5
5
5
5
5
Trace －
(S)-Segphos (5)
(S)-DRBM-Segphos
(5)
49
57
62
72
6
7
(S)-BINAP (5)
5
5
6
6
50
21
92
98
(S)-xyl-BINAP (5)
(S)-p-Tol-BINAP
(5)
8
5
6
35
81
9c (S)-BINAP (5)
10d (S)-BINAP (5)
11e (S)-BINAP (5)
12 (S)-BINAP (1.5)
13 (S)-BINAP (3.5)
14 (S)-BINAP (10)
5
5
6
24
24
6
n.r
28
45
15
36
55
－
89
91
44
61
90
5
1.5
3.5
10
6
6
a
Unless stated otherwise, all reactions were carried out using
Pt(COD)Cl2 (0.01 mmol), ligand (0.01 mmol), Zn (0.55 mmol,
2.75 equiv.), oxabenzonorbornadiene (0.2 mmol), terminal acety-
lene (0.4 mmol), and toluene at 90 ℃. b No Zn was used. c ZnCl2
(0.1 mol•L−1 in THF）was used instead of Zn. d 0.3 mmol Zn (1.5
With the optimal chiral ligand and catalyst loading
in hand, the influence of solvent and temperature on the
reaction was investigated (Table 2). It was observed that
the reaction in CH3CN, 1,2-dichloroethane (DCE), or
dioxane gave excellent enantioselectivities (up to 96%
ee) but with poor conversion (Table 2, Entries 2－4).
e
f
equiv.) was used. 0.7 mmol Zn (3.5 equiv.) was used. Isolated
yield after silica gel column chromatography. g Determined by
HPLC with a Chiralcel OD-H column.
616
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 613—618

Asymmetric Ring-opening Reaction of Oxabenzonorbornadiene with Terminal Alkynes
The use of toluene gave the best result both in yield and
Table 3 Scope of the alkynesa
in enantioselectivity (Table 2, Entry 1). Other solvents,
such as tetrahydrofuran (THF), DMSO, DME, THP re-
sulted in no reaction or inferior results (Table 2, Entries
5－8). With toluene as the solvent, the reaction tem-
perature was tested. The best yield and ee was obtained
when the reaction temperature was at 90 ℃ (Table 2,
Entry 1). The reaction did not work at room temperature,
and a too high temperature led to a worse outcome in
yield and ee (Table 2, Entries 9, 10).
O
Pt(COD)Cl2, (S)-Binap
+
H
Zn, solvent, 90 oC, 6 h
R1
1
OH
R1
2
Table 2 Effect of solvent and temperature on the asymmetric
ring-opening of oxabenzonorbornadiene 1a with phenylacety-
lenea
Entry
R1
Product Yieldb/% eec/%
1
2
H
4-Cl
2a
2b
2c
2d
2e
2f
50
40
44
35
42
54
60
62
42
51
92
50
43
50
71
61
61
51
63
67
Ph
O
Pt(COD)Cl2, (S)-Binap
3
3-Cl
+
Zn, solvent, temperature
4
2-Cl
H
1a
OH
2a
Ph
5
4-Br
6
4-NO2
4-CH3
4-C2H5
4-C3H7
4-n-C5H11
Entry Solvent Temperature/℃ Time/h Yieldb/% eec/%
7
2g
2h
2i
1
2
3
4
5
6
7
8
9
Toluene
CH3CN
DCM
90
90
90
90
90
90
90
90
r.t.
60
120
6
7
50
15
19
19
35
7
92
95
93
95
46
69
－
－
－
51
10
8
9
7
10
2j
Dioxane
DME
5
11
12
13
14
15
4-OCH3
4-OCH2CH3
1-Pentyne
2k
2l
33
51
0
30
50
－
－
－
5
THP
5
2m
2n
2o
THF
5
－
－
－
10
39
3,3-Dimethylbut-1-yne
Ethynyltrimethylsilane
0
DMSO
Toluene
6
0
a Conditions: Pt(COD)Cl2 (0.01 mmol), ligand (0.01 mmol), Zn
(0.55 mmol), oxabenzonorbornadiene (0.2 mmol), terminal
acetylene (0.4 mmol) and toluene at 90 ℃ under N2. b Isolated
yield after silica gel column chromatography. c Determined by
HPLC with a Chiralcel OD-H column.
24
22
1
10 Toluene
11 Toluene
a
Unless stated otherwise, all reactions were carried out using
Pt(COD)Cl2 (0.01 mmol), ligand (0.01 mmol), Zn (0.55 mmol),
oxabenzonorbornadiene (0.2 mmol), terminal acetylene (0.4
mmol) at 90 ℃. b Isolated yield after silica gel column chromato-
graphy. c Determined by HPLC with a Chiralcel OD-H column.
(CCDC 909135). The single crystal was obtained by
solvent evaporation from a solution of CH2Cl2. The ab-
solute configuration was assigned as (1R,2S) as appears
in Figure 1.
Under the optimized reaction conditions, the scope
of this platinum-catalyzed ring opening reaction was
explored. Different substituents in the phenylacetylene
moiety were tolerated, including electron-donating
groups, such as 4-alkyl (Table 3, Entries 7－10) and
4-alkoxyl (Table 3, Entries 11, 12), electron-withdraw-
ing groups, such as Cl, Br, and NO2 (Entries 2－6). In
all cases, the reaction afforded cis-2-alkynyl-1,2-di-
hydronaphthalen-1-ols in moderate yield with moderate
to high enantioselectivities, and the starting material
oxabenzonorbornadiene was consumed and some un-
separated mess was obtained except the ring-opening
product. Additionally, three aliphatic terminal acety-
lenes were investigated for the reaction, but no ring-
opening product was obtained except some inseparable
mess (Table 3, Entries 13－15).
Figure 1 Crystal structure of 2e.
Conclusions
In conclusion, we have developed the first plati-
num(II)-catalyzed asymmetric ring-opening of oxaben-
zonorbornadiene with terminal aromatic alkynes. The
The configuration of the ring-opening product 2e
was confirmed by X-ray crystallography analysis
Chin. J. Chem. 2014, 32, 613—618
© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
617

Long et al.
FULL PAPER
[13] Zhang, W.; Wang, L.-X.; Shi, W.-J.; Zhou, Q.-L. J. Org. Chem.
2005, 70, 3734.
[14] Carreras, J.; Avenoza, A.; Busto, J. H.; Peregrina, J. M. Org. Lett.
2007, 9, 1235.
[15] Cortez, G. A.; Baxter, C. A.; Schrock, R. R.; Hoveyda, A. H. Org.
Lett. 2007, 9, 2871.
[16] Machin, B. P.; Howell, J.; Mandel, J.; Blanchard, N.; Tam, W. Org.
Lett. 2009, 11, 2077.
reaction can proceed smoothly with a variety of substi-
tuted phenylacetylene in the presence of Pt(COD)Cl2/
(S)-BINAP with the addition of zinc powder, and pro-
vides an optional approach to synthesize the optically
active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in
moderate yields and with moderate to high enantiose-
lectivity under mild conditions.
[17] Tsui, G. C.; Lautens, M. Angew. Chem., Int. Ed. 2012, 51, 5400.
[18] Zhu, J.-T.; Tsui, G. C.; Lautens, M. Angew. Chem., Int. Ed. 2012, 51,
12353.
Acknowledgement
[19] Cabrera, S.; Arrayás, R. G.; Carretero, J. C. Angew. Chem., Int. Ed.
2004, 43, 3944.
[20] Ogura, T.; Yoshida, K.; Yanagisawa, A.; Imamoto, T. Org. Lett.
2009, 11, 2245.
[21] Yang, D.; Long, Y.; Wang, H.; Zhang, Z. Org. Lett. 2008, 10, 4723.
[22] Pan, X.; Huang, G.; Long, Y.; Zuo, X.; Xu, X.; Gu, F.; Yang, D. J.
Org. Chem. 2014, 79, 187.
[23] Zhang, T.-K.; Mo, D.-L.; Dai, L.-X.; Hou, X.-L. Org. Lett. 2008, 10,
3689.
We thank the support of this work by the National
Natural Science Foundation of China (No. 41376149)
and the Guangzhou Pearl River New Star Plan of Sci-
ence and Technology Program (No. 2012J2200015).
References
[1] For reviews, see: (a) Rayabarapu, D. K.; Cheng, C.-H. Acc. Chem.
Res. 2007, 40, 971; (b) Lautens, M.; Fagnou, K.; Hiebert, S. Acc.
Chem. Res. 2003, 36, 48; (c) Fagnou, K.; Lautens, M. Chem. Rev.
2003, 103, 169; (d) Cheng, H.; Liang, X.; Li, X.; Long, Y.; Yang, D.
Chin. J. Org. Chem. 2012, 32, 433 (in Chinese).
[2] Bao, H.; Wang, Z.; You, T.; Ding, K. Chin. J. Chem. 2013, 31, 67.
[3] Kang, Q.; Wang, L.; Zheng, Z.; Li, J.; Tang, Y. Chin. J. Chem. 2014,
DOI: 10.1002/cjoc.201400053.
[4] Lautens, M.; Fagnou, K. Tetrahedron 2001, 57, 5067.
[5] Lautens, M.; Fagnou, K.; Taylor, M.; Rovis, T. J. Organomet. Chem.
2001, 624, 259.
[6] Synder, S. E. J. Med. Chem. 1995, 38, 2395.
[7] Perrone, R. J. Med. Chem. 1995, 38, 942.
[8] Nakamura, M.; Matsuo, K.; Inoue, T.; Nakamura, E. Org. Lett. 2003,
5, 1373.
[9] Rayabarapu, D. K.; Chiou, C.-F.; Cheng, C.-H. Org. Lett. 2002, 4,
1679.
[10] Wu, M.-S.; Rayabarapu, D. K.; Cheng, C.-H. J. Org. Chem. 2004,
69, 8407.
[11] Wu, M-S.; Jeganmohan, M.; Cheng, C-H. J. Org. Chem. 2005, 70,
9545.
[24] Zhang, T.-K.; Mo, D.-L.; Dai, L.-X.; Hou, X.-L. Org. Lett. 2008, 10,
5337.
[25] Lautens, M.; Hiebert, S. J. Am. Chem. Soc. 2004, 126, 1437.
[26] Hodgson, D. M.; Maxwell, C. R.; Miles, T. J.; Paruch, E.; Matthews,
I. R.; Witherington, J. Tetrahedron 2004, 60, 3611.
[27] Bos, P. H.; Rudolph, A.; Pérez, M.; Fañanás-Mastral, M.; Ha-
rutyunyan, S. R.; Feringa, B. L. Chem. Commun. 2012, 48, 1748.
[28] Feng, C.-C.; Nandi, M.; Sambaiah, T.; Cheng, C.-H. J. Org. Chem.
1999, 64, 3538.
[29] Li, M.; Yan, X.-X.; Hong, W.; Zhu, X.-Z.; Cao, B.-X.; Sun, J.; Hou,
X.-L. Org. Lett. 2004, 6, 2833.
[30] Chen, C.-L.; Martin, S. F. J. Org. Chem. 2006, 71, 4810.
[31] Arrayás, R. G.; Cabrera, S.; Carretero, J. C. Org. Lett. 2003, 5, 1333.
[32] Nishimura, T.; Tsurumaki, E.; Kawamoto, T.; Guo, X.-X.; Hayashi,
T. Org. Lett. 2008, 10, 4057.
[33] Chen, H.; Li, S.; Xu, J.; Yang, Q.; Liu, S.; Zhou, Y.; Huang, C.; Fan,
B. Acta Chim. Sinica 2013, 71, 1243 (in Chinese).
[34] Hu, J.; Yang, Q.; Xu, J.; Huang, C.; Fan, B.; Wang, J.; Lin, C.; Bian,
Z.; Chan, A. S. C. Org. Biomol. Chem. 2013, 11, 814.
[35] Mo, D.-L.; Chen, B.; Ding, C.-H.; Dai, L.-X.; Ge, G.-C.; Hou, X.-L.
Organometallics 2013, 32, 4465.
[12] Bertozzi, F.; Pineschi, M.; Macchia, F.; Arnold, L. A.; Minnaard, A.
J.; Feringa, B. L. Org. Lett. 2002, 4, 2703.
[36] Villeneuve, K.; Tam, W. Organometallics 2007, 26, 6082.
(Zhao, C.)
618
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© 2014 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2014, 32, 613—618