4224
L. Minuti et al. / Tetrahedron: Asymmetry 11 (2000) 4221–4225
The EtOH filtrate, containing the diastereoisomer (S,R)-6, was evaporated and then recrystal-
lized twice from 95% EtOH to afford 0.46 g (69%) of diastereomerically pure (S,R)-6 as white
1
needles. [h] = +521 (c 0.29, CHCl ); mp 108–110°C (95% EtOH); H NMR (CDCl ) l 1.77 (m,
D
3
3
1
H, H-3%), 1.92–2.01 (m, 2H, Hs-4%), 2.13 (m, 1H, H-3%), 2.28 (s, 3H, ꢀCH ), 2.55 (ddd, 1H,
3
J=9.6, 7.3, 8.6 Hz, H-5%), 2.85 (ddd, 1H, J=12.6, 9.8, 6.5 Hz, H-2), 2.91–3.17 (m, 6H, Hs-1,
Hs-9, Hs-10), 3.40 (m, 1H, H-5%), 3.41 (dd, 1H, J=9.2, 7.0 Hz, ꢀOCH ꢀ), 3.42 (s, 3H, ꢀOCH ),
3
H-2), 6.44 (ddd, 1H, J=7.9, 1.5, 1.5 Hz, H-12), 6.45 (dd, 1H, J=7.8, 1.7 Hz, H-7), 6.48 (d, 1H,
J=7.8 Hz, H-8), 6.55 (dd, 2H, J=1.5, 1.5 Hz, H-15, H-16), 6.58 (d, 1H, J=1.7 Hz, H-5).
2
3
.59 (m, 1H, H-2%), 3.63 (dd, 1H, J=9.2, 4.2 Hz, ꢀOCH ꢀ), 3.89 (ddd, 1H, J=12.6, 9.6, 3.5 Hz,
2
13
C
NMR (CDCl ) l 18.99 (ꢀCH ), 22.87 (C-4%), 27.00 (C-3%), 35.27 (C-2), 35.30 (C-1), 35.44 (C-10),
3
3
3
1
5.77 (C-9), 54.49 (C-5%), 59.43 (ꢀOCH ), 66.95 (C-2%), 76.31 (ꢀOCH ꢀ), 131.13 (C-13 or C-12),
3
2
31.81 (C-7, C-15 or C-16), 132.00 (C-12 or C-13), 132.40 (C-5), 132.67, 132.86 (C-7, C-15 or
C-16), 136.24 (C-8), 137.88 (C-3), 139.11, 139.21 (C-11, C-14), 139.96, 140.01 (C-4, C-6), 159.49
(
ꢀCꢁNꢀ).
An aqueous saturated solution of oxalic acid (3.12 ml) was added to an ethereal solution (21
6
c
ml) of (S,S)-6 (0.52 g, 1.44 mmol). The resulting mixture was vigorously stirred at room
temperature for 3 days. Usual work up gave a residue which was purified by flash column
chromatography on silica gel. Elution with a 9:1 hexane/EtOAc solution gave 0.22 g (0.86
4,8
mmol) of pure (S)-3 (60%); [h] =+65 (c=0.26, CHCl ); mp: 129–130°C (heptane) [lit. [h] =
D
3
D
+
65 (c 0.5, CHCl ); mp 120–124°C].
3
Hydrolysis of (S,R)-6 (0.46 g) followed by column chromatography (SiO , 9:1 hexane/EtOAc)
2
of the crude residue afforded 0.46 g (1.27 mmol, 63%) of (R)-3; [h] =−65 (c 0.35, CHCl ); mp
D
3
4
,8
1
27–128°C (heptane) [lit. [h] = −65 (c 1, CHCl ); mp 127–128°C].
D
3
3
.3. (+)-(S)-4-Ethenyl[2.2]paracyclophane 1
A solution of 0.11 g of NaBH in 2 ml of H O was added to a refluxing solution of (S)-3 (0.22
4
2
g, 0.86 mmol) in EtOH (11 ml) and the reflux was continued for 2 h. The reaction mixture was
then poured into water and extracted three times with CHCl . The combined extracts were
3
washed with brine, dried (Na SO ) and evaporated under vacuum to obtain 0.21 g of a mixture
2
4
9
of alcohols (99%) which was used without further purification for the next step.
A solution of PBr (0.06 ml) in dry CH Cl (3 ml) was added dropwise and under nitrogen to
3
2
2
a stirred solution of the above mixture of alcohols (0.21 g, 0.85 mmol) in DMF (5 ml) at
1
0
−
10°C. The mixture was then warmed to 0°C and stirred at this temperature for 3 h. After
that, 0.43 g of LiBr and 0.57 g of Li CO were added and the resulting mixture was stirred at
2
3
1
00°C for 3 h. After that, the reaction mixture was cooled, poured into 2N aq. HCl solution and
extracted three times with Et O. The combined extracts were washed with brine and dried
2
(
Na SO ). The solvent was evaporated at reduced pressure and the residue was chro-
2
4
matographed on silica gel. Elution with hexane afforded 0.19 g (0.82 mmol, 96%) of pure (S)-1;
4,5
[
h] = +440 (c 0.14, CHCl ); mp 78–79°C (hexane) [lit. [h] = +443 (CHCl ); mp 78°C
D
3
D
3
(
petroleum ether)].
3
.4. (−)-(R)-4-Ethenyl[2.2]paracyclophane 1
R)-1 was obtained in 96% yield using the procedure described above, from 0.2 g (0.8 mmol)
(
4
of (R)-3; [h] = −440 (c 0.14, CHCl ); mp 81–82°C [lit. [h] = −330 (CHCl ); mp 95–98°C].
D
3
D
3