C. J. Sanders et al. / Tetrahedron: Asymmetry 12 (2001) 1055–1061
1059
syringe pump. The reaction mixture was stirred for an
additional 15 min, filtered through a silica plug, washed
with dichloromethane (2×15 mL) and concentrated.
The excess alkene was either removed in vacuo or by
column chromatography (hexane/ethyl acetate). The
product was identified by comparison of the NMR
spectra with those reported in the literature; cis/trans
ratios were calculated from NMR and from GC–MS,
and e.e.s were calculated from chiral GC–MS as
described.
cm−1: 3058, 3025, 2979, 2929, 2904, 1725, 1602, 1496,
1445, 1400, 1382, 1296, 1267, 1238, 1178, 1117, 1086,
1067, 1023, 968, 900, 849, 763, 737. Chiral GC–MS
(80°C, 4°/min): tRcis 16.48 (minor), 16.74 (major) min;
tRtrans 17.78 (major), 17.96 (minor) min.
4.3.4. tert-Butyl 2-methyl-2-phenylcyclopropane-1-car-
boxylate. Obtained as a colourless oil from the reaction
t
1
of a-methylstyrene with BDA. Yield: 84%. H NMR
(CDCl3) trans isomer: l 7.31–7.18 (m, 5H, Ph), 1.90 (m,
1H, H-C1), 1.49 (s, 9H, C(CH3)3), 1.35 (m, 2H, H2-C3),
1
1.13 (s, 3H, CCH3); H NMR (CDCl3) cis isomer: l
4.3. Data for cyclopropane products
7.31–7.18 (m, 5H, Ph), 1.80 (m, 1H, H-C1), 1.70 (m,
1H, H-C3), 1.51 (s, 9H, C(CH3)3), 1.44 (s, 3H, CCH3),
1.07 (m, 1H, H-C3); IR (thin film) w cm−1: 3059, 3004,
2978, 2929, 1721 (s), 1602, 1497, 1478, 1446, 1391,
1367, 1295, 1245, 1208, 1151 (s), 1118, 1086, 1068,
1029, 847, 763, 739, 700. Chiral GC–MS (80°C, 4°C/
min): tRcis 17.95 (minor), 18.13 (major) min; tRtrans 19.62
min.
4.3.1. Ethyl 2-phenylcyclopropane-1-carboxylate.3b Ob-
tained as a colourless oil from the reaction of styrene
1
with EDA. Yield: 94%. H NMR (CDCl3) trans isomer:
l 7.08–7.31 (m, 5H, Ar-H), 4.17 (q, J=7, 2H,
CH2CH3), 2.46–2.55 (m, 1H, H-C1), 1.86–1.93 (m, 1H,
H-C2), 1.54–1.62 (m, 1H, H-C3), 1.28 (t, J=7, 4H,
1
CH2CH3/H-C3); H NMR (CDCl3) cis isomer: l 7.08–
7.31 (m, 5H, Ph), 3.87 (q, J=7.2, 1H, CH3CH2), 2.46–
2.55 (m, 1H, H-C1), 2.03–2.11 (m, 1H, H-C2),
1.68–1.75 (m, 1H, H-C3), 1.54–1.62 (m, 1H, H-C3),
0.97 (t, J=7.2, 1H, CH2CH3). IR (thin film) w cm−1:
3063, 3030, 2982, 2936, 2906, 2873, 1725, 1605, 1498,
1460, 1439, 1408, 1386, 1366, 1337, 1325, 1306, 1266,
1221, 1186, 1078, 1042, 1018, 936, 850, 755, 723, 698.
4.3.5. Ethyl 2-methyl-3-phenylcyclopropane-1-carboxy-
late.27 A colourless oil obtained from the reaction of
b-methylstyrene with EDA. Yield: 63%. 1H NMR
(CDCl3) trans isomer: l 7.35–7.06 (m, 5H, Ph), 4.16 (q,
2H, J=7, CH2CH3), 2.69–1.64 (m, 3H, H-C1/H-C2/H-
C3), 1.35 (d, 3H, J=8, CH-CH3), 1.28 (t, 3H, J=7,
1
CH2CH3); H NMR (CDCl3) cis isomer: l 7.35–7.06
MS (EI+) m/z: 190 (M+), 162 (PhCH(CH2)CHCO2 ),
+
(m, 5H, Ph), 3.87 (q, 1H, J=7, CH2CH3), 2.69–1.64 (m,
3H, H-C1/H-C2/H-C3), 1.32 (d, 3H, J=8, CH-CH3),
(t, 3H, J=8, CH2CH3); IR (thin film) w cm−1: 3060,
3025, 2959, 2931, 2872, 1726 (s), 1603, 1496, 1443,
1371, 1349, 1266, 1179 (s), 1135, 1101, 1050, 1034, 963,
850, 736 (s), 696 (s), 588, 520, 499. Chiral GC–MS
(80–120°C, 0.5°C/min, 120–200°C, 10°C/min): tRcis
61.85 (minor), 62.84 (major) min; tRtrans 73.10 (minor),
73.62 (major) min.
145 (PhCH(CH2)CHCO+), 117 (PhCH(CH2)CH+). Chi-
ral GC–MS (80°C, 4°C/min): tRcis 18.0 (minor), 18.3
(major) min; tRtrans 18.9 (major), 19.1 (minor) min.
4.3.2. tert-Butyl 2-phenylcyclopropane-1-carboxylate.26
Obtained as a colourless oil from the reaction of sty-
t
1
rene with BDA. Yield: 81%. H NMR (CDCl3) trans
isomer: l 7.28–7.07 (m, 5.0H, Ph), 2.40–2.45 (m, 1H,
H-C1), 1.80–1.85 (m, 1H, H-C2), 1.49–1.54 (m, 1H,
H-C3), 1.46 (s, 9H, C(CH3)3), 1.19–1.25 (m, 1H, H-C3);
1H NMR (CDCl3) cis isomer: l 7.28–7.07 (m, 5H, Ph),
2.49–2.55 (m, 1H, H-C1), 1.94–2.00 (m, 1H, H-C2),
1.61–1.66 (m, 1H, H-C3), 1.26–1.31 (m, 0.27H, H-C3),
1.13 (s, 9H, C(CH3)3). IR (thin film) w cm−1: 3005, 2978,
2933, 1721 (s), 1606, 1498, 1457, 1438, 1402, 1367,
1342, 1327, 1287, 1256, 1231, 1208, 1152 (s), 1077,
1031, 969, 937, 844, 782, 757, 744, 723, 697.
4.3.6. tert-Butyl 2-methyl-3-phenylcyclopropane-1-car-
boxylate. Obtained as a colourless oil from the reaction
t
1
of b-methylstyrene with BDA. Yield: 96%. H NMR
(CDCl3) trans isomer: l 7.26–7.05 (m, 5H, Ph), 2.35–
1.47 (m, 3H, H-C1/H-C2/H-C3), 1.47 (s, 9H, C(CH3)3),
1.32 (d, 3H, J=8, CH-CH3); 1H NMR (CDCl3) cis
isomer: l 7.26–7.05 (m, 5H, Ph), 2.35–1.47 (m, 3H,
H-C1/H-C2/H-C3), 1.24 (d, 3H, J=8, CH-CH3), 1.14
(s, 9H, C(CH3)3); IR (thin film) w cm−1: 3062, 3027,
3005, 2977, 2931, 2872, 1720 (s), 1605, 1497, 1457,
1437, 1391, 1366, 1290, 1256, 1209, 1154 (s), 1102,
1078, 1045, 963, 845, 738, 697. Chiral GC–MS (80°C,
4°C/min): tRcis 18.99 (minor), 20.81 (major) min; tRtrans
19.14 (minor), 21.35 (major) min.
2-Phenylcyclopropanecarboxylic acid tert-butyl ester
was hydrolysed by TFA/C6H6 to give the free acid,
which was then analysed by chiral GC–MS. Chiral
GC–MS (80°C, 4°C/min): tRtrans 26.40 (major), 26.74
(minor) min; tRcis 27.48 (major), 28.10 (minor) min.
4.3.3. Ethyl 2-methyl-2-phenylcyclopropane-1-carboxy-
late.10a Obtained as a colourless oil from the reaction of
a-methylstyrene with EDA. Yield: 99%. 1H NMR
(CDCl3) trans isomer: l 7.36–7.20 (m, 5H, Ph), 4.19
(qd, J=2, 7, 2H, CH2CH3), 1.88–1.99 (m, 1H, H-C1),
1.75–1.79 (m, 1H, H-C3), 1.52 (s, 3H, CCH3), 1.39–1.45
4.3.7. Ethyl 2,2-diphenylcyclopropane-1-carboxylate.5
Obtained as a colourless oil from the reaction of 1,1%-
diphenylethylene with EDA. Yield: 89%. 1H NMR
(CDCl3): l 7.35–7.13 (m 10H, Ph), 3.83–3.99 (m, 2H,
CH2CH3), 2.55 (dd, J=6, 8, 1H, H-C1), 2.17 (dd, J=5,
6, 1H, H-C3), 1.59 (dd, J=5, 8, 1H, H-C3), 1.00 (t,
J=8, 3H, CH2CH3); IR (CH2Cl2) w cm−1: 3058, 3025,
2980, 2251, 1729, 1660, 1600, 1494, 1446, 1397, 1381,
1268, 1180, 1096, 1026, 748, 732, 702. Chiral HPLC
analysis (hexane, 0.5 mL/min): tR=21.1, (major), 23.2
(minor).
1
(m, 1H, H-C3), 1.30 (t, J=7, 3H, CH2CH3); H NMR
(CDCl3) cis isomer: l 7.36–7.20 (m, 5H, Ph), 3.83 (qd,
J=4, 8, 2H, CH2CH3), 1.88–1.99 (m, 1H, H-C1), 1.75–
1.79 (m, 1H, H-C3), 1.46 (s, 3H, CCH3), 1.12–1.16 (m,
1H, H-C3), 0.94 (t, J=8, 3H, CH2CH3); IR (CH2Cl2) w