8804
A. Kamal, G. Chouhan / Tetrahedron Letters 45 (2004) 8801–8805
2002, 692–693; (h) Reetz, M. T.; Wiesenhofer, W.;
Francio, G.; Leitner, W. Chem. Commun. 2002, 992–993.
CDCl3): d = 2.10 (s, 3H), 4.10 (dd, 1H, J = 11.89, 8.68Hz),
4.20 (dd, 1H, J = 11.89, 3.39Hz), 4.90 (dd, 1H, J = 8.25,
3.39Hz), 7.2–7.4 (m, 5H); EIMS m/z = 120 (M+ ꢁ 60).
Elemental anal. calcd for C10H12O3: C, 66.65; H, 6.71.
Found: C, 66.35; H, 6.62%.
13. Lee, K. J.; Kim, M.-J. J. Org. Chem. 2002, 67, 6845–6847.
14. (a) Erbeldinger, M.; Mesiano, A. J.; Russell, A. Biotech-
nol. Prog. 2000, 16, 1129–1131; (b) Lau, R. M.; Rantwijk,
F. V.; Seddon, K. R.; Sheldon, R. A. Org. Lett. 2001, 2,
4189–4191; (c) Kim, K.-W.; Song, B.; Choi, M.-Y.; Kim,
M.-J. Org. Lett. 2001, 3, 1507–1509; (d) Itoh, T.; Akasaki,
E.; Kudo, K.; Shirakami, S. Chem. Lett. 2001, 262–263; (e)
Scho¨fer, S. H.; Kaftzik, N.; Wasserscheid, P.; Kragl, U.
Chem. Commun. 2001, 425–426; (f) Park, S.; Kazlauskas,
R. J. J. Org. Chem. 2001, 66, 8395–8401.
15. (a) Pei, W.; Li, S.; Nie, X.; Li, Y.; Pei, J.; Chen, B.; Wu, J.;
Ye, X. Synthesis 1998, 1298–1304; (b) Sakuragi, H.;
Koyama, T.; Sakurazawa, M.; Yasui, N.; Tokumaru, K.;
Ueno, K. Bull. Chem. Soc. Jpn. 1994, 67, 1769–1772; (c)
Miller, J. M.; Brindel, I. D.; Cater, S. R.; So, K.-H.; Clark,
J. H. Anal. Chem. 1980, 52, 2430–2432; (d) DeGraw, J. I.
Tetrahedron 1972, 28, 967–972; (e) Levin, R. H.; Magerlin,
B. J., Jr.; McIntosh, A. V.; Hanze, A. R.; Fonken, G. S.;
Thompson, J. L.; Searcy, A. M.; Scheri, M. A.; Gutsell, E.
S. J. Am. Chem. Soc. 1954, 76, 546–547.
16. In a typical procedure, to a-chloroacetophenone (1mmol)
in the ionic liquid [bmim]Br (1.5mL) was added KOAc
(1.2mmol) at room temperature. The reaction mixture was
stirred for 30min then ether (3 · 5mL) was added to the
reaction mixture with vigorous stirring for 5min. The
reaction mixture was allowed to stand for a further 5min
and the clear supernatant liquid was decanted. The ether
layers were concentrated in vacuo to obtain the a-acetoxy
acetophenone which was sufficiently pure for the next step.
The remaining ionic liquid was dissolved in CH2Cl2
(2mL), filtered to remove solid materials and CH2Cl2
was removed in vacuo to afford the ionic liquid, which
could be recycled in subsequent runs.
17. (a) Kamal, A.; Damayanthi, Y.; Reddy, B. S. N.;
Laxminarayana, B.; Reddy, B. S. P. Chem. Commun.
1997, 1015–1016; (b) Kamal, A.; Ramana, K. V.; Rao, M.
V. J. Org. Chem. 2001, 66, 997–1001; (c) Kamal, A.;
Khanna, G. B. R.; Ramu, R.; Krishnaji, T. Tetrahedron
Lett. 2003, 44, 4783–4787; (d) Kamal, A.; Shaik, A. A.;
Sandbhor, M.; Malik, M. S. Tetrahedron: Asymmetry
2004, 15, 935–939.
(S)-2-Methylcarbonyloxy-1-phenylethyl
acetate
5a11
25
Yield: 46%; ½aꢀD +54.2 (c 1, CHCl3, >99% ee); IR (neat,
cmꢁ1): 1740; 1H NMR (200MHz, CDCl3): d = 2.10 (s,
3H), 2.15 (s, 3H), 4.20 (dd, 1H, J = 11.89, 8.17Hz), 4.30
(dd, 1H, J = 11.89, 3.71Hz), 6.0 (dd, 1H, J = 8.17,
3.71Hz), 7.25–7.40 (m, 5H); EIMS m/z 162 (M+ ꢁ 60).
Elemental anal. calcd for C12H14O4: C, 64.85; H, 6.35.
Found: C, 64.50; H, 6.29%.
(R)-2-Hydroxy-2-(4-bromophenyl)ethyl acetate 4b. Yield:
25
45%; ½aꢀD ꢁ27.3 (c 1, CHCl3, >99% ee); IR (neat,
cmꢁ1): 3440, 1735; 1H NMR (300MHz, CDCl3):
d = 2.10 (s, 3H), 4.10 (dd, 1H, J = 11.89, 8.30Hz), 4.20
(1H, dd, J = 11.89, 3.39Hz), 4.85 (m, 1H), 7.20 (d, 2H,
J = 8.68Hz), 7.45 (d, 2H, J = 8.68Hz); EIMS m/z = 200
(M+ ꢁ 59). Elemental anal. calcd for C10H11BrO3: C,
46.36; H, 4.28. Found: C, 46.25; H, 4.23%.
(S)-2-Methylcarbonyloxy-1-(4-bromophenyl)ethyl acetate
25
5b. Yield: 41%; ½aꢀD +55 (c 1.7, CHCl3, >99% ee);
IR (neat, cmꢁ1): 1740; 1H NMR (200MHz, CDCl3):
d = 2.00 (s, 3H), 2.10 (s, 3h), 4.2 (dd, 1H, J = 11.89,
8.17Hz), 4.30 (dd, 1H, J = 11.89, 3.71Hz), 5.90 (dd, 1H,
J = 8.17, 3.71Hz), 7.20 (d, 2H, J = 8.17Hz), 7.50 (d, 2H,
J = 8.17Hz); EIMS m/z = 242 (M+ ꢁ59). Elemental anal.
calcd for C12H13BrO4: C, 47.86; H, 4.35. Found: C, 47.70;
H, 4.30%.
(R)-2-Hydroxy-2-(4-methylphenyl)ethylacetate 4c. Yield:
25
42%; ½aꢀD ꢁ34.1 (c 1.5, CHCl3, >99% ee); IR (neat,
1
cmꢁ1): 3450, 1730; H NMR (200MHz, CDCl3): d = 2.10
(s, 3H), 2.30 (s, 3H), 4.10 (dd, 1H, J = 11.89, 8.17Hz), 4.20
(dd, 1H, J = 11.89, 3.71Hz), 4.9 (dd, 1H, J = 8.25,
3.71Hz), 7.10 (d, 1H, J = 8.17Hz), 7.20 (d, 1H,
J = 8.17Hz); EIMS m/z = 194 (M+). Elemental anal. calcd
for C11H14O3: C, 68.02; H, 7.26. Found: C, 67.93; H, 7.18%.
(S)-2-Methylcarbonyloxy-1-(4-methylphenyl)ethyl acetate
25
5c. Yield: 45%; ½aꢀD +70.2 (c 1.5, CHCl3, >99% ee);
IR (neat, cmꢁ1): 1730; 1H NMR (300MHz, CDCl3):
d = 2.0 (s, 3H), 2.15 (s, 3H), 2.40 (s, 3H), 4.15 (dd, 1H,
J = 11.89, 8.17Hz), 4.30 (dd, 1H, J = 11.89, 3.71Hz), 5.90
(dd, 1H, J = 8.17, 3.71Hz), 7.10 (d, 2H, J = 8.17Hz), 7.20
(d, 2H, J = 8.17Hz); EIMS m/z = 236 (M+). Elemental
anal. calcd for C13H16O4: C, 66.09; H, 6.83. Found: C,
65.93; H, 6.66%.
18. (a) Moussou, P.; Archelas, A.; Baratti, J.; Furstoss, R. J.
Org. Chem. 1998, 63, 3532–3537; (b) Weijers, C. A. G. M.
Tetrahedron: Asymmetry 1997, 8, 639–647; (c) Tsujigami,
T.; Sugai, T.; Ohta, H. Tetrahedron: Asymmetry 2001, 12,
2543–2549.
(R)-2-Hydroxy-2-(4-methoxyphenyl)ethylacetate
4d.
25
19. General procedure for the resolution of 1,2-diols 3a–d. To
a stirred solution of the appropriate 1,2-diol (50mg) in the
ionic liquid [bmim]PF6 (0.5mL) was added vinyl acetate
(6equiv) and lipase PS-C (0.5equiv w/w) at room temper-
ature. The mixture was stirred at room temperature for the
appropriate time (see Table 3). After about 50% conver-
sion of the reaction as indicated by HPLC/TLC, ether
(3 · 3mL) was added to the reaction mixture with stirring
for 5min. The mixture was allowed to stand for a further
5min and the clear supernatant liquid was decanted. The
ether layers were concentrated in vacuum to give an oily
residue, which was purified by silica gel column chroma-
tography (eluent: ethyl acetate–n-hexane) to afford the
monoacetate and diacetate products. The products were
analyzed by HPLC using a chiral column (details of the
chiral columns are given in the footnotes of Table 3) to
determine their optical purity and measure the enantio-
meric excess (ee).
Yield: 60% ½aꢀD ꢁ27 (c 1.2, CHCl3, >99% ee); IR (neat,
1
cmꢁ1): 3400, 1730; H NMR (200MHz, CDCl3): d = 2.10
(s, 3H), 3.80 (s, 3H), 4.10 (dd, 1H, J = 11.15, 8.17Hz), 4.20
(dd, 1H, J = 11.15, 3.71Hz), 4.80 (dd, 1H, J = 8.17,
3.17Hz), 6.85 (d, 2H, J = 8.92Hz) 7.30 (d, 2H,
J = 8.92Hz); EIMS m/z = 210 (M+). Elemental anal. calcd
for C11H14O4: C, 62.85; H, 6.71. Found: C, 62.81; H,
6.68%.
(S)-2-Methylcarbonyloxy-1-(4-methoxyphenyl)ethyl acetate
25
5d. Yield: 34%; ½aꢀD +81.4 (c 1, CHCl3, >99% ee); IR
1
(neat, cmꢁ1): 1730; H NMR (200MHz, CDCl3): d = 2.05
(s, 3H), 2.10 (s, 3H), 3.80 (s, 3H), 4.20–4.30 (m, 2H), 5.95
(dd, 1H, J = 11.89, 3.71Hz), 6.85 (d, 2H, J = 8.92 Hz),
7.30 (d, 2H, J = 8.92Hz); EIMS m/z = 252 (M+). Elemen-
tal anal. calcd for C13H16O5: C, 61.90; H, 6.39. Found: C,
61.85; H, 6.32%.
20. General procedure for the hydrolysis of 4a–d. In a typical
experiment K2CO3 (1.5mmol) was added to a solution of
4a–d (1mmol) in methanol (10mL). The mixture was
stirred for 3–4h, and then acidified with 1N HCl. The
mixture was evaporated and then extracted with diethyl
Spectroscopic data: (R)-2-Hydroxy-2-phenylethyl ace-
25
tate 4a.11 Yield: 43%; ½aꢀD ꢁ26.8 (c 1.1, CHCl3, >99%
ee); IR (neat, cmꢁ1): 3450, 1740; 1H NMR (300MHz,