Notes
J . Org. Chem., Vol. 65, No. 20, 2000 6759
D
dioxide 4a (1.24 g, 38%): mp 148-149 °C (from EtOH); [R]20
reactions for every example in this study (Tables 1, 2,
and 3). Although this might seem to be expected since
the hydroperoxyamine should have the same configura-
tion at the peroxyaminal carbon atom as the correspond-
ing carbon atom in the related oxaziridine, it would only
be so if the formation of the R-hydroperoxyamine were
stereospecific and if the mechanism and transition state
of O-transfer from the R-hydroperoxyamines and oxaziri-
dines were essentially the same, a situation which would
require the oxygen atom attached to the peroxyaminal/
oxaziridine carbon atom to be transferred in both cases.
We have already shown that, in sulfoxidations mediated
by camphorsulfonylimine, the major sense of asymmetric
induction is opposite to that found in oxidations brought
about by the derived oxaziridine.8d This difference in
behavior between the camphor-derived systems and those
based on pseudosaccharin is a continuing puzzle that will
require further investigation.
-71.4 (c 1.12 in CHCl3) (Found: C, 67.14; H, 7.63; N, 4.56;
C
17H23NO2S requires C, 66.85; H, 7.60; N, 4.59%); νmax (Nujol)/
cm-1 1606 and 1175; δH (300 MHz; CDCl3) 0.75 (3 H, d, J ) 7),
0.91 (3 H, d, J ) 7), 0.95 (3 H, d, J ) 6), 1.1-1.4 (3 H, m), 1.4-
1.6 (2 H, s), 1.65-2.1 (5 H, m), 3.1 (1 H, m, J ) 5), and 7.6-8.0
(4 H, m); δC (75 MHz; CDCl3) 16.3, 21.3, 22.1, 24.3, 28.5, 32.8,
34,4, 40.7, 45.1, 122.8, 123.8, 133.6, 133.8 and 179.8; m/z (EI)
306 (M+, 0.78%).
(+)-3-[(1′S)-1′-Men th yl]-1,2-ben zisoth ia zole 1,1-d ioxid e
4b (0.41 g, 13%) was also isolated as a colorless crystalline solid
from the product mixture by flash column chromatography using
n-hexane-dichloromethane (1:2) as eluent: mp 202-204 °C
D
(from EtOH), [R]20 +63.29 (c 0.79 in CHCl3) (Found: C, 66.65;
H, 7.61; N; 4.55. C17H23NO2S requires C, 66.85; H, 7.59; N,
4.59%); δH (300 MHz; CDCl3) 0.18-0.78 (9 H, m), 1.08-2.04 (9
H, m), 3.70 (1 H, s), and 7.60-8.00 (4 H, m); δC (75 MHz; CDCl3)
16.8, 20.6, 21.9, 23.7, 26.7, 31.4, 34.0, 39.9, 47.4, 83.6, 121.9,
123.3, 133.4, 134.0 and 176.8; m/z (EI) 305 (M+, 0.2%).
Compound 4c was isolated from the above reaction mixture
by flash column chromatography using n-hexane-dichlo-
romethane (1:2) as eluent and shown to be 3-[(1′R)-menthoxy]-
1,2-benzisothiazole 1,1-dioxide (0.51 g, 15%). Crystallization gave
Exp er im en ta l Section
D
colorless needles: mp 121-122 °C (from EtOH), [R]20 -92.9 (c
3.11 in CHCl3) (Found: C, 63.47; H, 7.23; N, 4.34. C17H23NO3S
requires C, 63.52; H, 7.22; N, 4.36%); νmax (Nujol)/cm-1 1614 and
1173; δH (300 MHz; CDCl3) 0.8-1.4 (12 H, m), 1.4-2.2 (5 H, m),
2.2-2.6 (1 H, m), 5.0-5.2 (1 H, m) and 7.6-8.0 (4 H, m); δC (75
MHz; CDCl3) 16.8, 20.5, 21.8, 23.7, 26.7, 31.4, 34.0, 39.9, 47.4,
83.6, 121.8, 123.3, 133.3, 133.9 and 168.6; m/z (EI) 321 (M+,
0.04%).
Gen er a l. All moisture-sensitive reactions were carried out
in round-bottomed flasks, which were baked at 150 °C for a
minimum of 2 h. The flasks were allowed to cool in a desiccator
and were purged with nitrogen prior to being sealed with septum
caps. Other apparatus such as syringes, needles, cannulas, and
magnetic stirrer bars were dried under similar conditions and
allowed to cool in a desiccator. Tetrahydrofuran and cyclohexane
were freshly distilled under an atmosphere of nitrogen from the
sodium benzophenone ketyl radical, and chloroform was distilled
from CaH2 prior to use. Aqueous hydrogen peroxide (30% w/v
aqueous solution) and other reagents were used as supplied.
Saccharin derivatives, chloro, ethoxy, and t-Bu, were synthesized
as reported previously.3
Flash column chromatography was performed using Merck
9385 Kieselgel 60 silica gel (230-400 mesh); compressed air was
used to supply any necessary pressure to the column. Thin-layer
chromatography was carried out on aluminum plates coated with
a 0.25 mm layer of silica gel containing fluorescence indicator
(Merck). UV-inactive compounds were visualized by exposure
to iodine mixed with silica gel or by spraying with aqueous
potassium permanganate (10 g in 1 L of water containing 5 g of
Na2CO3) followed by heating.
3-(2-Bor n yl)-1,2-ben zisoth ia zole 1,1-Dioxid e [5]. 3-(2-
Bornyl)-1,2-benzisothiazole 1,1-dioxide 5 was prepared using the
same procedure as described for (-)-3-[(1′R)-1′-menthyl]-1,2-
benzisothiazole 1,1-dioxide 4a above using (-)-bornyl chloride
9 (2.0 g, 11.5 mmol, 1.0 equiv), magnesium (1.0 g, 41.1 mmol),
ethyl bromide (0.05 mL), and 3-chloro-1,2-benzisothiazole 1,1-
dioxide 8 (2.3 g, 11.4 mmol). Bornyl chloride was purified before
use by sublimation under reduced pressure, followed by recrys-
tallization from methanol and vacuum-drying for several hours.
3-(2-Bornyl)-1,2-benzisothiazole 1,1-dioxide 5 was isolated from
the reaction mixture by flash column chromatography using
petroleum ether-dichloromethane (1:1) as eluent (0.9 g, 26%).
All attempts to prepare diastereoisomerically pure 3-(2-bornyl)-
1,2-benzisothiazole 1,1-dioxide by column chromatography or
crystallization using different mixtures of solvents proved dis-
appointing. The 1H NMR spectrum indicated the presence of a
54:46 ratio of 3-[(2′S)-2′-bornyl)-1,2-benzisothiazole 1,1-dioxide
5a and 3-[(2′R)-2′-bornyl)]-1,2-benzisothiazole 1,1-dioxide 5b,
determined by integration of the triplets for the methine proton
adjacent to the heterocyclic ring and appearing at 3.20 and 3.55
ppm. The isomeric mixture had mp 158-160 °C (from EtOH):
The chiral shift reagent used to determine enantiomeric
excesses from nuclear magnetic resonance (1H, 13C) spectra was
(R)-(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol.12
P r oced u r es. (-)-3-[(1′R)-1′-Men th yl]-1,2-ben zisoth ia zole
1,1-Dioxid e [4a ], (+)-3-[(1′S)-1′-Men t h yl]-1,2-b en zisot h ia -
zole 1,1-Dioxid e [4b ], a n d 3-[(1′R)-Men t h oxy]-1,2-b en z-
isoth ia zole 1,1-Dioxid e [4c]. In a 100 mL three-necked round-
bottomed flask equipped with a magnetic stirrer bar, argon inlet,
rubber septum, condenser, and dropping funnel was placed
magnesium (340 mg, 13 mmol) and dry tetrahydrofuran (4 mL).
The mixture was treated with ethyl bromide (0.4 mL), and after
the reaction had progressed for a few minutes, a solution of (-)-
menthyl chloride (2.0 mL, 1.87 g, 10 mmol) in tetrahydrofuran
(4 mL) was added, portionwise, over a period of 4 h at 50 °C,
followed by reflux for 30 min. This solution was added via
syringe to a separate 250 mL round-bottom flask equipped with
an argon inlet and rubber septum and containing 3-chloro-1,2-
benzisothiazole 1,1-dioxide 8 (2.01 g, 10 mmol), in dry tetrahy-
drofuran (60 mL) cooled to 0 °C. The resulting mixture was
stirred overnight and quenched by adding water (50 mL). The
solution was diluted with ether (45 mL), and the organic layer
was washed with 10% aqueous HCl (35 mL), water (3 × 45 mL),
and dried over MgSO4. Removal of the solvent in vacuo gave a
mixture of (-)-3-[(1′R)-1′-menthyl]-1,2-benzisothiazole 1,1-
dioxide 4a and (+)-3-[(1′S)-1′-menthyl]-1,2-benzisothiazole 1,1-
dioxide 4b (3:1) determined by integration from the NMR
spectrum, together with a third, unknown compound, 4c. The
crude material was separated by flash column chromatography
using n-hexane-dichloromethane (1:2) as eluent to give as a
colorless solid (-)-3-[(1′R)-1′-menthyl]-1,2-benzisothiazole 1,1-
D
[R]20 +49.4 (c 0.89 in CH2Cl2) (Found: C, 67.05; H, 7.01; N,
4.53. C17H21NO2S requires C, 67.30; H, 6.98; N, 4.62%); νmax
(Nujol)/cm-1 1602 and 1171; δH (300 MHz; CDCl3) 0.85-1.17 (6
H, m) 1.20-2.08 (9 H, m), 2.10-2.60 (1 H, m), 3.20 (1 H, t, J )
9), 3.55 (1 H, m, J ) 5) and 7.45-8.60 (4 H, m); δC (75 MHz;
CDCl3) 14.4, 18.8, 20.1, 27.5, 29.2, 34.0, 40.3, 45.3, 48.5, 51.6,
122.4, 124.7, 133.3 and 133.6; m/z (EI) 305 (M+, 0.45%).
(1R,4R)-1-Ch lor o-3,3-d im eth yl-2-m eth ylen ebicyclo[2.2.1]-
h eptan e [10]. (1R,4R)-1-Chloro-3,3-dimethyl-2-methylenebicyclo-
[2.2.1]heptane, 10, was prepared as previously described.7 In a
dry 250 mL round-bottomed flask equipped with a magnetic
stirrer was placed D-camphor (15.2 g, 0.10 mol) in dichlomethane
(25 mL). The flask was chilled in an ice bath, and phosphorus
trichloride (12.8 g) and phosphorus pentachloride (22.2 g) were
added in small portions. After 2 h the reaction mixture was
allowed to reach room temperature for 10 h. The reaction
mixture was poured onto ice and extracted with petroleum ether
(2 × 40 mL). The extract was washed with water (2 × 30 mL)
and evaporated to leave a clear, colorless liquid (15 g) which
was refluxed for 12 h with potassium acetate (20 g) in ethanol-
water (100 mL, 75:25). The solution was then poured into water
(100 mL) and extracted with petroleum ether (2 × 40 mL). The
combined organic extracts were washed with water (2 × 40 mL),
dried over MgSO4, and evaporated in vacuo. Distillation of the
residue under reduced pressure (72-78 °C, 1 mmHg) gave a