624
P. T. Baraldi et al. / Tetrahedron: Asymmetry 13 (2002) 621–624
(216 mg, 1.24 mmol) in diethyl ether (2 mL) at 0–5°C.
After stirring for 12 h at rt, the mixture was cooled and
water (0.33 mL) was added followed by 10% aqueous
NaOH (0.24 mL). The resulting mixture was filtered
through Celite using diethyl ether (10 mL) as eluent.
The organic layer was dried over MgSO4 and concen-
trated in vacuum. The residue was purified on a silica
gel column, using hexane:ethyl acetate 60:40 as eluent.
bromide (65.3 mL, 0.875 mmol). After disappearance of
the metal, this solution was transferred via a cannula to
a solution containing tosylate 6 (50 mg, 0.18 mmol) in
dry diethyl ether (2 mL) at –100°C under nitrogen. Then
a 0.10 M solution of lithium tetrachlorocuprate in THF
(13 mL, 0.013 mmol) was added. The mixture was
allowed to warm to room temperature and stirred for 12
h. Then, the mixture was washed with saturated aqueous
solution of NH4Cl (2 mL). The aqueous layer was
extracted with diethyl ether (3×2 mL), then the combined
organic layers were washed with H2O (1 mL), dried over
MgSO4 and concentrated in vacuum. The residue was
purified by column chromatography using hexane:ethyl
acetate 8:2 as eluent, affording the desired alcohol 1 (17
mg, 70%). IR (wmax, film, cm−1): 3350, 2964, 2928, 1468,
1367, 1026. 1H NMR (200 MHz-CDCl3) l: 0.90 (d, J=6.6
Hz, 3H), 0.92 (d, J=6.6 Hz, 3H), 1.27–1.41 (m, 11H),
1.74–1.71 (m, 1H), 3.6–3.7 (m, 1H). 13C NMR (50
MHz-CDCl3) l: 14.0, 22.0, 22.7, 23.4, 24.6, 27.8, 37.8,
46.8, 69.9. Anal calcd. for C9H20O: C, 74.94; H, 13.97.
Found: C, 74.74; H, 13.84. (R)-1: [h]2D5=−10.4 (c 0.5,
CHCl3), lit.4 [h]D23=−10.5 (c 1.17 CHCl3). (S)-1: [h]D25=
+11.5 (1.04, MeOH), lit.4 [h]D22=+11.6 (c 1.04, MeOH).
Diol 5 was obtained in 85% yield (106 mg). IR (wmax
,
film, cm−1): 3407; 2943; 2871; 1727; 1635; 1475. 1H
NMR (200 MHz-CDCl3) l: 0.93 (d, J=6.6 Hz, 6H),
1.4–1.7 (m, 5 H), 3.8–4.0 (m, 3H). 13C NMR (50
MHz-CDCl3) l: 14.2, 19.3, 22.1, 23.30, 24.35, 38.6,
46.9, 61.8, 70.3. MS (% rel. intensity) m/z: 114 (1.2), 85
(26), 75 (100), 57 (94). Anal. calcd for C7H16O2: C,
63.59; H, 12.19. Found: C, 63.74; H, 12.34. (S)-5:
[h]D25=+16.3 (c 1.9, CHCl3). (R)-5: [h]2D5=−15.4 (c 1.5,
CHCl3).
3.5. (S)- and (R)-3-Hydroxy-5-methylhexyl-p-tolueno-
sulfonate 6
A solution of 5 (250 mg, 1.9 mmol) in anhydrous
triethylamine (0.4 mL, 2.85 mmol) and dry dichloro-
methane (10 mL) was cooled at 0–5°C and then was
added in portions p-toluenesulfonyl chloride (4×100 mg,
2.28 mmol) during 6 h. The mixture was maintained at
this temperature for 24 h. The reaction was quenched with
ice–water (3 mL) and the aqueous layer was extracted with
ether (3×2 mL). The combined ether extracts were washed
with saturated NaHCO3 (3 mL) and brine (3 mL), then
dried over anhydrous Na2SO4, and evaporated to dryness
under reduced pressure. The residue was purified on a
silica gel column, using hexane:ethyl acetate 70:30 as
eluent to afford tosylate 6 (430 mg, 80%). IR (wmax, film,
cm−1): 3531, 2956, 2933, 1598, 1357, 1189, 966, 917, 765.
1H NMR (200 MHz-CDCl3) l: 0.88 (d, J=6.6 Hz, 3H),
0.90 (d, J=6.6 Hz, 3H), 1.17 (ddd, J=4.4; 8.1; 13.1 Hz,
1H), 1.39 (ddd, J=5.3; 8.7, 13.1 Hz, 1H), 1.57–1.91 (m,
3H), 2.4 (s, 3H), 3.74–3.81 (m, 1H), 4.13 (ddd, J=4.8;
5.9; 10.0 Hz, 1H), 4.28 (ddd, J=5.1; 8.7; 10.0 Hz, 1H),
7.3 (d, J=8 Hz, 2H), 7.8 (d, J=6.5 Hz, 2H). 13C NMR
(50 MHz-CDCl3) l: 21.6, 22.0, 23.3, 24.6, 36.9, 46.7, 66.6,
67.9, 127.9, 129.9, 133.2, 144.8. Anal. calcd for
C14H22O4S: C, 58.71; H, 7.74; S, 11.19. Found: C, 58.58;
H, 7.77; S, 11.38%. (S)-7: [h]2D5=−5.2 (c 0.4, CHCl3).
(R)-7: [h]2D5=+5.0 (c 0.5, CHCl3).
Acknowledgements
The authors are grateful to FAPESP, CAPES and CNPq
(Brazil), and IFS (Sweden) for financial support.
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3.6. (S)- and (R)-2-Methyl-4-octanol 1
To a mixture of magnesium turnings (21 mg, 0.875 mmol)
in anhydrous diethyl ether (6 mL) was added ethyl