768
M. Nour et al. / Tetrahedron: Asymmetry 12 (2001) 765–769
2H), 3.71 (s, 3H), 6.95–7.05 (m, 2H), 7.14–7.20 (m, 3H);
13C NMR (50 MHz, CDCl3) l 204.9 (C), 201.3 (C),
171.1 (C), 139.4 (C), 130.7 (2 CH), 128.1 (2 CH), 125.7
(CH), 60.9 (C), 52.3 (CH3), 39.7 (CH2), 36.1 (CH2),
29.4 (CH2), 26.4 (CH3), 23.1 (CH3). Anal. calcd for
C16H20O4: C, 69.54; H, 7.30. Found: C, 69.68; H,
7.17%.
1.78–1.95 (m, 1H), 2.0 (d, J=1 Hz, 3H), 2.10–2.50 (m,
3H), 2.80 (d, J=14 Hz, 1H), 3.45 (d, J=14 Hz, 1H),
3.70 (s, 3H), 5.9 (d, J=1 Hz, 1H), 7.0–7.1 (m, 2H),
7.15–7.25 (m, 3H); 13C NMR (50 MHz, CDCl3) l 194.6
(C), 171.4 (C), 162.2 (C), 136.5 (C), 130.7 (2 CH), 128.1
(2 CH), 126.7 (CH), 126.0 (CH), 56.9 (C), 52.4 (CH3),
39.8 (CH2), 29.5 (CH2), 28.8 (CH2), 24.1 (CH3). Anal.
calcd for C16H18O3: C, 74.39; H, 7.02. Found: C, 74.52;
H, 7.29%.
3.4. General procedure for synthesis of Hagemann’s
ester cyclisation
To the adduct (0.010 mol) was added piperidine (0.008
mol) and acetic acid (0.0095 mol). The mixture was
stirred at 80°C for 1.5 h, dissolved in diethyl ether (20
mL), and the organic phase washed with water (3×15
mL). The aqueous layer was extracted with diethyl
ether (2×30 mL). The combined organic extracts were
dried over sodium sulfate and concentrated in vacuo
and the evaporation residue was purified by flash chro-
matography [silica gel, ethyl acetate:hexane (2:8)].
Acknowledgements
The authors are grateful to the Ballu company for the
generous gift of optically active 1-phenylethylamine and
Nadia Pelligrini for her technical assistance.
References
3.4.1. (R)-1,2-Dimethyl-4-oxo-cyclohex-2-enecarboxylic
acid ethyl ester 2a. Oil; yield 78%; [h]D=+108.3 (c=4.1,
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1
CHCl3); IR (film, cm−1): 1734, 1678, 1627; H NMR
(200 MHz, CDCl3) l 1.25 (t, J=7 Hz, 3H), 1.40 (s,
3H), 1.95 (d, J=1 Hz, 3H), 2.00–2.30 (m, 2H), 2.40–
2.60 (m, 2H), 4.20 (q, J=7 Hz, 2H), 5.90 (q, J=1 Hz,
1H); 13C NMR (50 MHz, CDCl3) l 197.8 (C), 173.5
(C), 161.1 (C), 127.7 (CH), 60.9 (CH2), 46.9 (C), 33.9
(CH2), 33.9 (CH2), 21.9 (CH3), 19.8 (CH3), 13.7 (CH3).
Anal. calcd for C11H16O3: C, 67.32; H, 8.22. Found: C,
67.20; H, 8.35%.
3.4.2.
(R)-1-Ethyl-2-methyl-4-oxo-cyclohex-2-enecar-
boxylic acid ethyl ester 2b. Oil; yield 68%; [h]D=+109.7
(c=6.2, CHCl3); IR (film, cm−1): 1714, 1675, 1652; H
1
NMR (200 MHz, CDCl3) l 0.86 (t, J=7 Hz, 3H), 1.26
(t, J=7 Hz, 3H), 1.65–1.74 (m, 2H) 1.98 (d, J=1 Hz,
3H), 1.98–2.10 (m, 2H), 2.30–2.60 (m, 2H), 4.18 (q,
J=7 Hz, 2H), 5.95 (q, J=1 Hz, 1H); 13C NMR (50
MHz, CDCl3) l 195.0 (C), 170.5 (C), 162.1 (C), 126.7
(CH), 60.8 (CH2), 55.1 (C), 29.5 (CH2), 28.0 (CH2),
22.9 (CH2), 24.8 (CH3), 13.9 (CH3), 9.8 (CH3). Anal.
calcd for C12H18O3: C, 68.54; H, 8.63. Found: C, 68.42;
H, 8.27%.
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3.4.3. (S)-1-Allyl-2-methyl-4-oxo-cyclohex-2-enecar-
boxylic acid methyl ester 2c. Syrup; yield 79%; [h]D=
1
+88.4 (c=12.8, CHCl3); IR (film, cm−1): 1731, 1678; H
NMR (200 MHz, CDCl3) l 1.96 (d, J=1 Hz, 3H),
2.00–2.07 (m, 1H), 2.25–2.45 (m, 3H), 2.50–2.70 (m,
2H), 3.69 (s, 3H), 5.09–5.15 (m, 2H), 5.60–5.75 (m, 1H),
5.90 (q, J=1 Hz, 1H); 13C NMR (50 MHz, CDCl3) l
198.1 (C), 173.0 (C), 159.9 (C), 132.8 (CH), 129.4 (CH),
119.4 (CH2), 55.7 (C), 50.4 (CH3), 39.9 (CH2), 34.1
(CH2), 30.4 (CH2), 21.3 (CH3). Anal. calcd for
C12H16O3: C, 69.21; H, 7.74. Found: C, 69.18; H,
7.77%.
3.4.4. (S)-1-Benzyl-2-methyl-4-oxo-cyclohex-2-enecar-
boxylic acid methyl ester 2d. White powder; mp 40–
43°C; yield 65%; [h]D=−62.5 (c=3.2, CCl4); IR (film,
cm−1): 3100, 1740, 1680; 1H NMR (200 MHz, CDCl3) l