Organometallics
Article
MHz, CDCl3; selected peaks): δ 3.96 (d, J = 6.0 Hz, 1H), 2.01 (m,
1H), 0.36−0.18 (m, 2H). A comparison of the intensity of the
resonances at δ 2.01 and δ 1.76 corresponding to the diastereotopic
protons β to gold established ≥95% deuterium incorporation at one
of the two positions β to gold.
was placed in the probe of an NMR spectrometer precooled at −78
°C and analyzed by 1H NMR spectroscopy. The yields for
cyclopropanation and protodeauration were determined by integrat-
ing the H NMR resonances for 3 at δ 0.93 or δ 0.63 and for 4 at δ
3.99 relative to the resonance of nitrobenzene at δ 8.20 or CH2Br2 at
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δ 4.96 in the H NMR spectrum. The H NMR spectra of 3 and 4
were consistent with published data.49,50
(P)AuCHDCHDCH(OMe)Ph (1-1,2-d2). Isotopomer 1-1,2-d2 was
synthesized from boronic esters threo-2-1,2-d2 or erythro-2-1,2-d2 by
employing procedures analogous to that used to synthesize erythro-1-
2-d1 in 72% yield (from threo-2-1,2-d2) and 14% yield (from erythro-2-
For 3. 1H NMR (−20 °C, 500 MHz, CD2Cl2; aliphatic
resonances): δ 1.85 (tt, J = 8.8, 5.1 Hz, 1H), 0.94 (m, 2H), 0.65
(m, 2H).
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1,2-d2) as white solids. The H NMR spectra of 1-1,2-d2 prepared
For 4. 1H NMR (−20 °C, 500 MHz, CD2Cl2; aliphatic
resonances): δ 3.97 (t, J = 6.7 Hz, 1H), 3.13 (s, 3H), 1.73 (m,
2H), 0.83 (m, 3H).
from both threo-2-1,2-d2 and erythro-2-1,2-d2 were indistinguishable as
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were homonuclear H−1H decoupling experiments, thus confirming
the scrambling of the Cα stereocenter. 1H NMR (500 MHz, CDCl3):
δ 7.85 (dd, J = 7.5, 4.9 Hz, 1H), 7.41 (t, J = 7.5 Hz, 2H), 7.34−7.18
(m, 8H), 7.16−7.06 (m, 3H), 3.96 (d, J = 6.8 Hz, 1H), 3.20 (s, 3H),
2.06−1.97 (m, 0.5H), 1.80−1.70 (m, 0.5H), 1.38 (d, J = 14.2 Hz,
18H), 0.36−0.27 (m, 0.5H), 0.27−0.17 (m, 0.5H).
Cyclopropanation of erythro-1-2-d1. A solution of erythro-1-2-d1
(11 mg, 1.7 × 10−2 mmol) in CD2Cl2 (0.2 mL) was added via syringe
to an NMR tube containing a solution of CH2Br2 (2.5 × 10−3 mmol;
internal standard) and AlCl3 (2.7 mg, 2.0 × 10−2 mmol) in CD2Cl2
(0.3 mL) at −78 °C, and the tube was washed with additional CD2Cl2
(0.2 mL). The tube was placed in the probe of an NMR spectrometer
precooled at −78 °C. The yields of cis-3-d1 and 4-2-d1 were
determined by integrating the resonances at δ 1.84 and δ 0.82
corresponding to the benzylic proton of cis-3-d1 and the methyl
resonance of 4-2-d1, respectively, relative to the resonance of CH2Br2
at δ 4.96 in the 1H NMR spectrum. Integration of the resonances at δ
1.84 and δ 0.66 corresponding to the benzylic and cis hydrogen
resonances of cis-3-d1 gave a ratio of 1.00:1.01, indicating complete
deuteration of one of the positions cis to the phenyl group.51 The
relative configuration of cis-3-d1 was further established by
(P)AuCH2CH2CH(SMe)Ph (5). A solution of (3-bromo-1-
phenylpropyl)(methyl)sulfane (50.1 mg, 0.20 mmol) in diethyl
ether (0.8 mL) was added dropwise to a solution of tBuLi (0.40
mmol) in diethyl ether (0.7 mL) at −78 °C and stirred for 5 min. To
the resulting light yellow solution, a solution of (P)AuCl (105 mg,
0.20 mmol) in CH2Cl2 (0.7 mL) was added dropwise at −78 °C to
form a colorless solution that was warmed slowly to 0 °C and stirred
at room temperature for 30 min. The resulting slightly murky solution
was concentrated under vacuum to give a white solid. The crude solid
was dissolved in hexanes−EtOAc (9:1), and the resulting mixture was
filtered through basic alumina. The filtrate was concentrated,
triturated with pentanes, and dried under vacuum to give 5 (46.4
mg, 35%) as a white solid. 1H NMR (500 MHz, CDCl3): δ 7.85 (ddd,
J = 7.6, 5.8, 1.8 Hz, 1H), 7.46−7.37 (m, 2H), 7.33−7.14 (m, 9H),
7.10 (d, J = 7.4 Hz, 1H), 7.08 (d, J = 7.4 Hz, 1H), 3.55 (dd, J = 8.3,
6.0 Hz, 1H), 2.01 (dtd, J = 11.9, 8.2, 5.9 Hz, 2H), 1.85 (s, 3H), 1.38
(d, J = 14.1 Hz, 8H), 1.37 (d, J = 14.1 Hz, 9H), 0.42−0.31 (m, 2H).
13C{1H} NMR (125 MHz, CDCl3): δ 150.6 (d, J = 17.4 Hz), 144.1,
143.4, 135.5, 132.9 (d, J = 7.8 Hz), 129.8, 129.5, 128.6, 128.1, 127.1,
126.5 (d, J = 3.8 Hz), 126.4, 57.9 (d, J = 6.9 Hz), 37.4 (d, J = 17.3
Hz), 37.3 (d, J = 16.5 Hz), 31.2 (d, J = 4.6 Hz), 31.1, 27.7 (d, J = 91.6
Hz), 14.9. 31P{1H} NMR (162 MHz, CDCl3): δ 65.5. HRMS (ESI)
calcd. (found) for C30H41AuPS (MH)+: 661.2327 (661.2326).
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comparison of the H NMR data to the reported values and by
selective homonuclear 1H−1H decoupling experiments (see the
Cyclopropanation of cis-7. A solution of CH2Br2 (0.73 mg, 4.2 ×
10−3 mmol; internal standard), TMSOTf (3.5 mg, 1.6 × 10−2 mmol),
and pyridine (0.20 μL, 2.6 × 10−3 mmol) in CD2Cl2 (0.3 mL) was
added to a solution of cis-7 (8 mg, 1.3 × 10−2 mmol) in CD2Cl2 (0.2
mL) at −78 °C, and the tube was washed with additional CD2Cl2
(0.15 mL). The tube was placed in the probe of an NMR
spectrometer precooled at −78 °C and monitored by 1H NMR
spectroscopy. Consumption of cis-7 was complete within 15 min to
form a mixture of TMSOMe, bicyclo[3.1.0]hexane (82%), and
cyclohexyl methyl ether (16%). The yields of bicyclo[3.1.0]hexane
and cyclohexyl methyl ether were determined by integrating the exo
cyclopropyl proton of bicyclo[3.1.0]hexane52 at δ 0.26 and the
methoxy resonance of cyclohexyl methyl ether53 at δ 3.28 relative to
cis-(P)AuCHCH2CH(OMe)CH2CH2CH2(cis-7). A slurry of magnesi-
um powder (100 mg. 4.1 mmol) and 1,2-dibromoethane (30 μL) in
THF (1 mL) was stirred at 50 °C for 20 min. A solution of cis-1-
chloro-3-methoxycyclohexane (300 mg, 2.0 mmol) in THF (0.8 mL)
was added to the slurry, and the resulting suspension was heated at
reflux for 5 h. After cooling to room temperature and allowing the
excess Mg to settle, 0.6 mL of the dark gray solution was transferred
to a solution of (P)AuOTf (120 mg, 0.19 mmol) in THF (10 mL)
and stirred for 12 h at 25 °C. The resulting mixture was concentrated,
filtered through a thin pad of basic alumina with hexanes−EtOAc
(9:1), concentrated, redissolved in pentane, and recrystallized at −20
°C to give cis-7 as a slightly off white solid (23.0 mg, 20% from
(P)AuOTf). 1H NMR (500 MHz, CDCl3): δ 7.85 (ddd, J = 7.5, 5.5,
2.1 Hz, 1H), 7.45−7.34 (m, 5H), 7.20 (ddd, J = 7.5, 4.1, 1.9 Hz, 1H),
7.15 (dd, J = 7.0, 2.3 Hz, 2H), 3.33 (s, 3H), 2.76 (tt, J = 10.3, 3.6 Hz,
1H), 2.09 (dq, J = 12.4, 3.1 Hz, 1H), 1.93−1.84 (m, 1H), 1.70 (dq, J
= 9.3, 3.1 Hz, 1H), 1.35 (dt, J = 14.0, 2.4 Hz, 17H), 0.58 (tdt, J =
12.5, 9.0, 3.1 Hz, 1H). 13C{1H} NMR (125 MHz, CDCl3): δ 143.2,
135.6, 132.8 (d, J = 7.4 Hz), 129.9 (d, J = 25 Hz), 129.8, 129.6, 128.5
(d, J = 5.2 Hz), 128.1, 127.1, 126.4 (d, J = 3.3 Hz), 83.3 (d, J = 9.4
Hz), 55.5, 42.7 (d, J = 99.2 Hz), 42.3, 37.2 (d, J = 16.1 Hz), 36.3 (d, J
= 4.5 Hz), 33.8, 31.2 (d, J = 7.7 Hz), 29.5 (d, J = 9.3 Hz). 31P{1H}
NMR (162 MHz, CDCl3): δ 63.5.
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the resonance of CH2Br2 at δ 4.96 in the H NMR spectrum.
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
Experimental procedures, spectroscopic data, and scans
AUTHOR INFORMATION
Corresponding Author
■
Ross A. Widenhoefer − Department of Chemistry, French
Family Science Center, Duke University, Durham, North
Author
Cyclopropanation of Gold Alkyl Complexes. General
Procedure for Cyclopropanation of 1. A solution of 1 (14.4 mg,
2.23 × 10−2 mmol) in CD2Cl2 (0.25 mL) was added dropwise with
constant agitation to a silanized NMR tube containing Lewis acid
(1.5−2.0 equiv) and nitrobenzene or CH2Br2 (internal standard) in
CD2Cl2 (0.35 mL) at −78 °C to give a colorless solution. The tube
Nana Kim − Department of Chemistry, French Family Science
Center, Duke University, Durham, North Carolina 27708,
United States
Complete contact information is available at:
F
Organometallics XXXX, XXX, XXX−XXX