ReactiVity of Epoxides with LTMP
chromatography (SiO2, 100% petrol) to give alkene 14b (123 mg,
93%, E/Z ) 98:2, by GC-MS analysis, tR Z-14b 13.02 min, tR
E-14b 14.22 min, initial temp 80 °C, max temp 280 °C, rate 10
°C/min) as a colorless oil; Rf 0.48 (100% petrol); IR (neat)/cm-1
3025m, 2956s, 2925s, 2853s, 1625w, 1599w, 1494w, 1466m, 927s;
1H NMR (400 MHz) δ 7.38-7.29 (m, 4H), 7.21 (tt, J ) 7.5, 1.5,
1H), 6.41 (d, J ) 16, 1H), 6.26 (dt, J ) 16, 7, 1H), 2.22 (dt, J )
7, 7, 2H), 1.53-1.45 (m, 2H), 1.40-1.25 (m, 14H), 0.92 (t, J )
6.5, 3H); 13C NMR (100 MHz) δ 138.0, 131.3, 129.7, 128.5, 126.7,
125.9, 33.1, 32.0, 29.7, 29.6, 29.4, 29.4, 29.3, 22.7, 14.1; MS m/z
(CI) 245 (M + H+, 18), 244 (57), 117 (47), 104 (100), 91 (14);
HRMS calcd for C18H29 (M + H+) 245.2269, found 245.2267.
(18), 121 (25); HRMS calcd for C19H31O (M + H+) 275.2375,
found 275.2373.
General Procedure C: Optimized Conditions for Allylsilane
Formation via LTMP-Modified Reductive Alkylation Using
r-Silyllithiums Generated in Situ, Described for (E)-(1-Pentyl-
tridec-2-en-1-yl)trimethylsilane 14m. To a solution of vinyltri-
methylsilane (84 mg, 84 mmol) in THF (1 mL) at -78 °C was
added n-BuLi (1.6 M in hexanes; 0.44 mL, 0.70 mmol) dropwise.
The reaction mixture was stirred at this temperature for 2 h and
then at -30 °C for 2 h. The reaction mixture was warmed to 0 °C
(ice bath), and a solution of LTMP (prepared from the addition of
n-BuLi (1.6 M in hexanes; 0.44 mL, 0.70 mmol) to 2,2,6,6-
tetramethylpiperidine (99 mg, 0.70 mmol) in hexane (7 mL) at 0
°C) was added dropwise. After 5 min, 1,2-epoxydodecane 13 (100
mg, 0.54 mmol) was added, and the reaction mixture was stirred
for 2 h at 0 °C. After being quenched with saturated brine solution
(10 mL), the layers were separated. The aqueous layer was extracted
with Et2O (2 × 10 mL), the combined organic layers were dried
(MgSO4), and solvent was evaporated in vacuo. The residue was
purified by reverse-phase column chromatography27 (C18 silica, 15%
Et2O in MeCN) to give allylsilane 14m (130 mg, 74%, E-only by
GC-MS analysis, E-14m 10.18 min, initial temp 80 °C, max temp
280 °C, rate 20 °C/min) as a colorless oil; Rf 0.13 (C18 silica, 15%
Et2O in MeCN); IR (neat)/cm-1 2924s, 2854s, 1467m, 1378w,
1258m, 969m, 861m; 1H NMR (400 MHz) δ 5.24-5.12 (m, 2H),
1.99 (dt, J ) 6.5, 6.5, 2H), 1.42-1.16 (m, 25 H), 0.91-0.86 (m,
6H), -0.01 (s, 9H); 13C NMR (100 MHz) δ 131.5, 128.2, 32.9,
32.9, 31.9, 31.8, 30.1, 29.7, 29.6, 29.5, 29.4, 29.1, 29.0, 28.9, 22.7,
22.6, 14.2, 14.1, -3.1; MS m/z (CI) 325 (M + H+, 34), 251 (13),
(8), 250 (48), 90 (100), 73 (25); HRMS calcd for C21H45Si (M +
H+) 325.3291, found 325.3287.
General Procedure B: Optimized Conditions for Alkene
Formation via LTMP-Modified Reductive Alkylation Using
Organolithiums Generated in Situ via Halogen-Lithium Ex-
change, Described for (E)-1-Dodec-1-enyl-4-methoxybenzene
14c. To a solution of 4-bromoanisole (131 mg, 0.70 mmol) in THF
(1 mL) at -78 °C was added t-BuLi (1.5 M in pentane; 0.94 mL,
1.40 mmol) dropwise. The reaction mixture was stirred at this
temperature for 30 min and then warmed to 0 °C (ice bath). After
5 min, a solution of LTMP (prepared by the addition of n-BuLi
(1.6 M in hexanes; 0.68 mL, 1.08 mmol) to 2,2,6,6-tetramethylpi-
peridine (153 mg, 1.08 mmol) in hexane (8 mL) at 0 °C) was added
dropwise. The reaction was left for a further 5 min at 0 °C, and
then 1,2-epoxydodecane 13 (100 mg, 0.54 mmol) was added. The
ice bath was removed, and the reaction mixture was stirred for a
further 2 h. After being quenched with saturated brine solution (10
mL), the layers were separated. The aqueous layer was extracted
with Et2O (2 × 10 mL), the combined organic layers were dried
(MgSO4), and solvent was evaporated in vacuo. The residue was
purified by column chromatography (SiO2, 2% Et2O in petrol) to
give alkene 14c (104 mg, 70%, E/Z ) 98:2 by GC-MS analysis,
tR Z-14c 14.35 min, tR E-14c 16.78 min, initial temp 100 °C,
max temp 280 °C, rate 10 °C/min) as a white solid; Rf 0.48
(10% Et2O in petrol); mp 36-39 °C; IR (CHCl3)/cm-1 2954m,
2920s, 2850m, 1608w, 1513w, 1465w, 1251w, 1176w, 1023w,
962w; 1H NMR (400 MHz) δ 7.31 (d, J ) 9, 2H), 6.87 (d, J ) 9,
2H), 6.35 (d, J ) 16, 1H), 6.12 (dt, J ) 16, 7, 1H), 3.82 (s, 3H),
2.21 (q, J ) 7, 2H), 1.52-1.44 (m, 2H), 1.41-1.25 (m, 14H), 0.92
(t, J ) 7, 3H); 13C NMR (400 MHz) δ 158.6, 130.8, 129.1, 129.0,
127.0, 113.9, 55.2, 33.1, 31.9, 29.7, 29.6, 29.6, 29.4, 29.3, 22.7,
14.1; MS m/z (CI) 275 (M + H+, 100), 274 (69), 147 (63), 134
Acknowledgment. We thank the EPSRC and GlaxoSmith-
Kline for a CASE award, the EPSRC for a research grant (GR/
S46789/01), and the EPSRC National Mass Spectrometry
Service Centre for mass spectra.
Note Added after ASAP Publication. There were errors in
Table 10 in the version published May 26, 2007; the corrected
version was published May 29, 2007.
Supporting Information Available: Experimental procedures
and characterization for all products. This material is available free
JO070291V
(27) Farina, V. J. Org. Chem. 1991, 56, 4985-4987.
J. Org. Chem, Vol. 72, No. 13, 2007 4773