4548 J. Am. Chem. Soc., Vol. 118, No. 19, 1996
Charette and Marcoux
NMR probe for the study shown in Figures 4, 5a, and 6a: 1H NMR
(400 MHz, CD2Cl2, 158 K) δ 3.95-3.83 (m, 8H, THF), 1.95-1.84
(m, 8H, THF), 1.34 (br s, 2H); 13C NMR (100 MHz, CD2Cl2, 158 K)
δ 69.7 (THF), 24.7 (THF), 19.8 (CH3CH2I), 1.8 (CH3CH2I), -17.4.
Formation and NMR Analysis of the Zn(CH2I)2‚THF Complex
(Figures 5b and 6b). To a vacuum-dried NMR tube sealed with a
septum and Teflon tape and purged several times with argon were added
at room temperature CD2Cl2 (1.30 mL), THF (142 µL, 1.75 mmol),
and CH2I2 (142.0 µL, 1.76 mmol). The NMR tube was cooled to -78
°C, and Et2Zn (90 µL, 0.88 mmol) was then slowly added. The tube
was then warmed to room temperature for about 20 s to dissolve the
white precipitate and then cooled back to -78 °C. The NMR tube
was then directly transferred to the precooled NMR probe for the study
shown in Figures 5b and 6b: 1H NMR (400 MHz, CD2Cl2, 158 K) δ
3.81-3.65 (m, 8H), 1.88-1.74 (m, 8H), 1.33-1.18 (m, 4H); 13C NMR
(100 MHz, CD2Cl2, 158 K) δ 68.7 (THF), 24.8 (THF), 19.8 (CH3-
CH2I), 1.8 (CH3CH2I), -17.3.
Formation of a Mixture of IZnCH2I‚THF and Zn(CH2I)2‚THF
(Figure 7). The complexes were independently prepared as described
above and were transferred into a dry NMR tube via a Teflon cannula
under argon at -78 °C. The NMR tube was then directly transferred
to the precooled NMR probe for the study shown in Figure 7.
Formation and NMR Analysis of the (1R)-exo,exo-2,3-Dimethoxy-
1,7,7-trimethylbicyclo[2.2.1]heptane‚Zinc Iodide Complex (4) (Fig-
ure 8). Diether 3 (68 mg, 0.35 mmol) and iodine (175 mg, 0.69 mmol)
were placed in a vacuum-dried NMR tube. The tube was then sealed
with a septum and Teflon tape and purged with argon. CD2Cl2 (1.30
mL) was added via a dried syringe, and the NMR tube was cooled to
-78 °C. Neat Et2Zn (35.0 µL, 0.35 mmol) was then slowly added,
and the tube was allowed to reach room temperature until there was a
complete disappearance of iodine. The solution was then placed in
the NMR probe for analysis: 1H NMR (400 MHz, CD2Cl2, 298 K) δ
3.89 (d, J ) 7 Hz, 1H), 3.75 (s, 3H), 3.70 (d, J ) 7 Hz, 1H), 3.56 (s,
3H), 2.09 (d, J ) 5 Hz, 1H), 1.85-1.74 (m, 1H), 1.52 (dt, J ) 5, 12
Hz, 1H), 1.10 (t, J ) 8 Hz, 3H), 1.07 (s, 3H), 1.03 (s, 3H), 0.88-1.02
(m, 2H), 0.82 (s, 3H), 0.24 (q, J ) 8 Hz, 2H); 13C NMR (100 MHz,
CD2Cl2, 298 K) δ 90.8, 86.5, 62.3, 58.0, 50.3, 47.4, 45.3, 23.4, 20.1,
13.4, 3.9.
NMR Spectra of the (1R)-exo,exo-2,3-Dimethoxy-1,7,7-trimethyl-
bicyclo[2.2.1]heptane‚Diethylzinc Complex (5) (Figure 9). Diether
3 (98 mg, 0.49 mmol) was placed in a vacuum-dried NMR tube sealed
with a septum and Teflon tape and purged with argon. CD2Cl2 (1.30
mL) and Et2Zn (50 µL, 0.49 mmol) were added via a dried syringe.
The solution was then placed in the NMR probe for analysis: 1H NMR
(400 MHz, CD2Cl2, 298 K) δ 3.45-3.22 (m, 1H), 3.43 (br s, 3H),
3.37 (s, 3H), 3.21 (d, J ) 7 Hz, 1H), 1.87 (d, J ) 5 Hz, 1H), 1.74-
1.66 (m, 1H), 1.49 (dt, J ) 4, 12 Hz, 1H), 1.15 (br t, J ) 8 Hz, 6H),
1.11-0.88 (m, 2H), 1.09 (s, 3H), 0.94 (s, 3H), 0.81 (s, 3H), 0.25 (q, J
) 4, 8 Hz, 4H); 13C NMR (100 MHz, CD2Cl2, 298 K) δ 91.2, 87.5,
60.7, 57.9, 49.7, 47.8, 46.9, 34.2, 24.4, 21.3, 20.7, 11.8, 10.7, 5.8.
NMR Spectra of the (1R)-exo,exo-2,3-Dimethoxy-1,7,7-trimethyl-
bicyclo[2.2.1]heptane‚Ethylzinc Iodide Complex (6) (Figure 10).
Diether 3 (123 mg, 0.62 mmol) and iodine (157 mg, 0.62 mmol) were
placed in a vacuum-dried NMR tube. The tube was then sealed with
a septum and Teflon tape and purged with argon. CD2Cl2 (1.00 mL,
0.62 M) was added via a dried syringe, and the NMR tube was cooled
to -78 °C. Neat Et2Zn (49 µL, 0.48 mmol) was then slowly added,
and the tube was allowed to reach room temperature until there was a
complete disappearance of the iodine to form a homogeneous, colorless
solution. The solution was then placed in the NMR probe for
analysis: 1H NMR (400 MHz, CD2Cl2, 298 K) δ 3.80 (d, J ) 7 Hz,
1H), 3.66 (br s, 3H), 3.61 (d, J ) 7 Hz, 1H), 3.50 (br s, 3H), 2.05 (d,
J ) 5 Hz, 1H), 1.80-1.70 (m, 1H), 1.50 (dt, J ) 5, 12 Hz, 1H), 1.09
(t, J ) 8 Hz, 3H), 1.06 (s, 3H), 1.03 (s, 3H), 1.02-0.91 (m, 2H), 0.82
(s, 3H), 0.23 (q, J ) 8 Hz, 2H); 13C NMR (100 MHz, CD2Cl2, 298 K)
δ 90.8, 86.5, 62.3, 58.0, 50.3, 47.4, 45.3, 23.4, 21.2, 20.8, 20.1, 13.4,
12.0, 3.9. -0.3; 13C NMR (100 MHz, CD2Cl2) δ (ZnCH2CH3) (223
K) 2.8 (br), (223 K) 2.1, (163 K) 1.5; δ (ZnCH2CH3) (223 K) 12.0,
(223 K) 11.8, (163 K) 11.6.
times with argon. CD2Cl2 (0.70 mL) and CH2I2 (64 µL, 0.78 mmol)
were successively added via a syringe. The NMR tube was cooled to
-78 °C, and Et2Zn (40 µL, 0.39 mmol) was then slowly added. The
tube was warmed to room temperature (ca. 20 s) to completely dissolve
the white precipitate and was cooled back to -78 °C. The NMR tube
was then directly transferred to the precooled NMR probe for
analysis: 1H NMR (400 MHz, CD2Cl2, 273 K) δ 3.79 (d, J ) 7 Hz,
1H), 3.59 (s, 3H), 3.56-3.53 (m, 1H), 3.53 (s, 3H), 1.97 (d, J ) 5 Hz,
1H), 1.72-1.61 (m, 1H), 1.45 (dt, J ) 4, 12 Hz, 1H), 1.38-1.32 (m,
1
4H), 1.05-0.86 (m, 2H), 0.98 (s, 3H), 0.97 (s, 3H), 0.75 (s, 3H); H
NMR (400 MHz, CD2Cl2, 173 K) δ 3.86-3.81 (m, 1H), 3.55 (s, 3H),
3.56-3.50 (m, 1H), 3.51 (s, 3H), 1.95-1.93 (m, 1H), 1.64-1.54 (m,
1H), 1.45-1.32 (m, 3H), 1.17-1.11 (m, 2H), 1.14 (s, 3H), 1.00-0.80
(m, 2H), 0.93 (s, 3H), 0.85 (s, 3H); 13C NMR (100 MHz, CD2Cl2, 253
K) δ 90.9, 87.1, 61.6, 58.5, 49.8, 46.9, 45.2, 33.1, 23.4, 21.0 (CH3-
CH2I), 20.6, 19.9, 11.9, 0.4 (CH3CH2I), -17.8; 13C NMR (100 MHz,
CD2Cl2, 173 K) δ 89.8, 86.5, 61.0, 58.2, 49.2, 46.5, 43.8, 31.8, 22.5,
20.3, 20.0 (CH3CH2I), 19.2, 11.4, 11.9, 1.7 (CH3CH2I), -15.1, -17.4;
13C NMR (100 MHz, CD2Cl2) δ (Zn(CH2I)2) (173 K) -15.1, -17.4,
(193 K) -15.6, -17.8, (203 K) -15.8 (br), -18.0, (br), (213 K) -16.1
(br), -18.1 (br), (223 K) -17.4 (coalescent), (233 K) -17.5 (br), (253
K) -17.8.
NMR Spectra of (1R)-exo,exo-2,3-Dimethoxy-1,7,7-trimethyl-
bicyclo[2.2.1]heptane‚(Iodomethyl)Zinc Iodide (8) (Figure 12). Di-
ether 3 (95 mg, 0.48 mmol) and iodine (122 mg, 0.48 mmol) were
placed in a vacuum-dried NMR tube. The tube was then sealed with
a septum and Teflon tape and purged with argon. CD2Cl2 (0.70 mL)
was added via a dried syringe, and the NMR tube was cooled to -78
°C. Neat Et2Zn (49 µL, 0.48 mmol) was then slowly added, and the
tube was allowed to reach room temperature until there was a complete
disappearance of the iodine to form a colorless solution. CH2I2 (39
µL, 0.48 mmol) was then added at -78 °C. The NMR tube was directly
transferred to the precooled NMR probe for analysis: 1H NMR (400
MHz, CD2Cl2, 273 K) δ 3.84 (d, J ) 7 Hz, 1H), 3.73 (s, 3H), 3.66 (d,
J) 7 Hz, 1H), 3.60 (s, 3H), 2.07 (d, J ) 5 Hz, 1H), 1.84-1.70 (m,
1H), 1.51 (dt, J ) 4, 12 Hz, 1H), 1.42 (br s, 2H), 1.06 (s, 3H), 1.03 (s,
1
3H), 0.98-0.79 (m, 2H), 0.81 (s, 3H); H NMR (400 MHz, CD2Cl2,
163 K) δ 3.72 (br d, J ) 7 Hz, 1H), 3.64 (br s, 3H, 3.58 (br d, J ) 7
Hz, 1H,), 3.53 (br s, 3H), 2.05-2.00 (m, 1H), 1.70-1.59 (m, 1H),
1.45-1.32 (m, 3H), 1.05-0.70 (m, 2H), 0.98 (br s, 3H), 0.88 (br s,
3H), 0.70 (br s, 3H); 13C NMR (100 MHz, CD2Cl2, 163 K) δ 88.7,
84.9, 62.7, 59.0, 49.1, 46.6, 43.4, 31.6, 22.0, 19.9 (CH3CH2I), 19.6,
11.5, 1.9 (CH3CH2I), -19.3; 13C NMR (100 MHz, CD2Cl2) δ (ZnCH2I)
(163 K) -19.3, (193 K) -19.5, (233 K) -19.6, (273 K) -19.8.
Preparation of a Mixture of 3‚IZnCH2I and 3‚Zn(CH2I)2 (Figure
13). The complexes 3‚IZnCH2I and 3‚Zn(CH2I)2 were independently
prepared as described above and were transferred into a dry NMR tube
via a Teflon cannula under argon at -78 °C. The NMR tube was then
directly transferred to the precooled NMR probe for analysis.
Preparation of 3‚IZnCH2I from 3‚Zn(CH2I)2 and 3‚ZnI2 (Figure
14). The complexes 3‚Zn(CH2I)2 and 3‚ZnI2 were independently
prepared as described above, and equimolar amounts were transferred
into a dry NMR tube via a Teflon cannula under argon at -78 °C. The
NMR tube was then directly transferred to the precooled NMR probe
for analysis.
NMR Spectra of (1R)-exo,exo-2,3-Dimethoxy-1,7,7-trimethyl-
bicyclo[2.2.1]heptane‚(Iodomethyl)ethylzinc (9) (Figure 15). Diether
3 (79 mg, 0.40 mmol) was placed in a vacuum-dried NMR tube sealed
with a septum and Teflon tape and purged with argon. CD2Cl2 (0.70
mL) and CH2I2 (32 µL, 0.40 mmol) were then successively added via
purged syringes. The NMR tube was cooled to -78 °C, and neat Et2-
Zn (41 µL, 0.40 mmol) was then slowly added. The white precipitate
was allowed to dissolve by shaking the tube at room temperature for
about 20 s, and it was then cooled back to -78 °C. The NMR tube
was directly transferred to the precooled NMR probe for analysis: 1H
NMR (400 MHz, CD2Cl2, 273 K) δ 3.66-3.62 (m, 1H), 3.53 (br s,
3H), 3.47-3.39 (m, 1H), 3.46 (s, 3H), 1.97-1.92 (m, 1H), 1.74-1.64
(m, 1H), 1.46 (dt, J ) 4, 12 Hz, 1H), 1.38 (dd, J ) 11, 14 Hz, ca. 1H),
1.33 (m, ca. 1H), 1.10 (br t, J ) 8 Hz, 3H), 1.05-0.86 (m, 2H), 1.01
(s, 3H), 0.97 (s, 3H), 0.77 (s, 3H), 0.35-0.01 (m, 2H); 13C NMR (100
MHz, CD2Cl2, 203 K) δ 89.9, 86.1, 60.1, 57.4, 49.2, 46.5, 44.5, 32.6,
23.0, 20.6, 20.0 (CH3CH2I), 19.4, 12.3, 11.7, 11.3, 4.5, 1.1 (CH3CH2I),
-1.5, -13.3, -16.0, -18.1; 13C NMR (100 MHz, CD2Cl2, 163 K) δ
NMR Spectra of the (1R)-exo,exo-2,3-Dimethoxy-1,7,7-trimethyl-
bicyclo[2.2.1]heptane‚Bis(iodomethyl)zinc Complex (7) (Figure 11).
Diether 3 (78 mg, 0.39 mmol) was placed in a NMR tube, and the
tube was sealed with a septum and Teflon tape and purged several