4356
M. Schulz et al. / Tetrahedron: Asymmetry 9 (1998) 4341–4360
1
were not isolated, they were identified from the crude mixture by comparing with the racemic products
1
(
GC and H NMR analyses). 17c: Elemental analysis: calc. (found) C: 74.34 (74.34), H: 11.50 (10.98).
H NMR (300 MHz): 1.02 (s, 9H, t-Bu), 1.24 (s, 9H, t-Bu), 1.40–2.10 (m, 6H, 3CH ), 4.42 (m, 1H,
CHO), 5.50 (m, 1H, CHolef). C NMR (75 MHz): 19.3 (CH ), 24.7 (CH ), 26.5 (CH ), 26.9 (CH ), 28.8
CH ), 35.5 (C), 77.7 (CH), 79.7 (C), 115.45 (CH), 152.8 (C). GC–MS (EI): m/z 137 (100, M −C H O ).
1
2
13
2
2
3
2
+
(
3
4
9
2
(b) (Entry 10 of Table 1): The analogous oxidation of 13c (3.32 g, 20 mmol) at 0°C (14 d, conv. of
t-BuOOH: 69%) led to 226 mg (73% rel. to conv.) of the mixture of isomeric peroxides 16c–18c (ratio
1
6c:17c:18c=5:75:15), from which 180 mg (58%) pure 17c {[α]D27.5 −9.2 (c 0.44, CHCl ); ee 8% (S),
3
see above} was isolated by chromatography.
Reduction of 17c: As described for the peroxide 2, 215 mg (0.95 mmol) 17c in 3 ml n-hexane was
treated with 2 mmol DIBAH (50°C, 10 h). Chromatographic purification (n-hexane:EtOAc 10:1) yielded
1
07 mg (73%) 1-tert-butyl-1-cyclohexen-3-ol. Reduction of 17c {[α]D22 −20 (c 1.93, CHCl ); exp. (a)}
3
afforded the allylic alcohol with an ee value of 16% [chiral GC: temp. 150°C, t 15.3 min (R), 15.6 min
R
27.5
(S)]. From the reduction of 17c {[α]
−9.2 (c 0.44, CHCl ); exp. (b)}, 1-tert-butyl-1-cyclohexen-3-ol
3
D
25
with 8% ee and [α]D −5.2 (c 0.57, CHCl ) was obtained.
3
3.11. Peroxidation of (−)-(1S,5S)-2-pinene 23a
According to the general procedure, 1.36 g (10 mmol) 23a was oxidized in a solvent mixture of
MeCN:acetone (1:1) using 180 mg (2 mmol) t-BuOOH (98%), 70 mg (0.25 mmol) Cu(I)OTf and 114
mg (0.375 mmol) 3 at 0°C (10 d, conv. of t-BuOOH: 85%). After usual work up and chromatography
(
n-pentane:Et O 100:1), 100 mg (58% rel. to conv.) of the mixture of peroxides 24a–30a [product
2
composition: 24a (16.4%), 25a (0.8%), 26a (46.7%), 27a (21.8%), 28a (8.3%), 29a (1.4%), 30a (4.5%);
GC–MS analysis] was obtained. The main product 26a was isolated in pure form as a colourless oil
{
yield: 32 mg, 17% rel. to conv.; [α]D25 −0.1 (c 0.86, CH Cl )} by chromatographic separation (n-
2
2
pentane:Et O 100:1). The other isomers were obtained as enriched samples of the following purities
2
1
13
(GC analyses): 24a (90%), 27a (80%) and 28a (60%). They were identified by H and C NMR
1
1
1
1
1
13
spectroscopy ( H, H-COSY, H, H-NOESY, APT and H, C-HETCOR experiments). The peroxides
2
see below), 29a (GC–MS analysis) and 30a ( H NMR, C NMR and GC–MS analysis) were identified
1
5a (comparison of the H and GC–MS data with those of the isolated enantiomeric compound 25b,
1
13
directly from the crude mixture.
1
(1R,2S,5R)-2-tert-Butylperoxy-3-pinene (24a): H NMR (500 MHz): 0.95 (s, 3H, CH , H-9), 1.19 (s,
3
9
H, t-Bu), 1.35 (s, 3H, CH , H-8), 1.39 (s, 3H, CH , H-10), 1.77 (d, 1H, H-7exo, J 8.8 Hz), 2.14 (q, 1H,
3 3
H-5, J 6.2 Hz), 2.21 (td, 1H, H-1, J 6.3 Hz, J 2 Hz), 2.27 (dt, 1H, H-7 , J 9 Hz, J 5.7 Hz), 5.48
1
2
endo
1
2
13
(
dm, 1H, H-3, J 8.8 Hz), 6.33 (dd, 1H, H-4, J 9 Hz, J 6.5 Hz). C NMR (100 MHz): 24.05 (C-9),
1 2
2
5.9 (C-10), 26.70 (t-Bu), 27.58 (C-8), 32.41 (C-7), 42.55 (C-5), 46.39 (C-6), 50.46 (C-1), 126.75 (C-3),
+
139.84 (C-4). GC–MS (EI): m/z 135 (3, M − C H O ).
4
9
1
2
(
1R,2R,5R)-2-tert-Butylperoxy-3-pinene (25a): H NMR (500 MHz): 1.06 (s, 3H, CH ), 1.19 (s, 9H,
3
t-Bu), 1.30 (s, 3H, CH , H-9), 1.33 (s, 3H, CH ), 1.40 (d, 1H, H-7exo, J 9 Hz), 2.10–2.14 (m, 2H, H-1
3
3
and H-5), 2.47 (dt, 1H, H-7endo, J 9 Hz, J 5.3 Hz), 5.68 (dd, 1H, H-3, J 9 Hz, J 1.5 Hz), 6.24 (dd, 1H,
1
2
1
2
+
H-4, J 9 Hz, J 6.5 Hz). GC–MS (EI): m/z 135 (3, M −C H O ).
1
2
4
9
2
1
(
1S,4R,5S)-4-tert-Butylperoxy-2-pinene (26a): H NMR (500 MHz): 0.87 (s, 3H, CH , H-9), 1.23 (s,
3
9
H, t-Bu), 1.33 (s, 3H, CH , H-8), 1.40 (dt, 1H, H-7exo, J 9 Hz, J 1.4 Hz), 1.71 (t, 3H, CH , H-10, J 1.5
3 1 2 3
Hz), 2.0 (td, 1H, H-1, J 5.1 Hz, J 1.3 Hz), 2.21 (dt, 1H, H-7 , J 9 Hz, J 5.6 Hz), 2.43 (m, 1H, H-5),
1
2
endo
1
2
13
4
.52 (m, 1H, H-4), 5.30 (m, 1H, H-3). C NMR (100 MHz): 20.36 (C-9), 22.80 (C-10), 26.46 (t-Bu),