Stereoselective epoxidation of vinyl sulfones and N-(p-tolylsulfonyl)-vinylsulfoximines derived from isopropylideneglyceraldehyde: Synthesis of chiral building blocks

Article abstract of DOI:10.1039/a807458e

Epoxidation of N-(p-tolylsulfonyl)vinylsulfoximines using metal alkyl peroxides proceeds with varying degrees of stereoselectivity, depending both on the metal cation and the steric bulk of the alkyl peroxide group. The stereochemical outcome of the epoxidation of substrates bearing an allylic asymmetric centre is also dependent upon the epoxidising agent, and very high levels of stereoselectivity may be obtained in the formation of sulfonyloxirane 8a. This oxirane was subsequently converted into the sulfonyloxirane 15, a precursor to a useful chiral functionalised acyl anion equivalent. In addition, the optically pure α-bromothioester 20 was also prepared.

Full text of DOI:10.1039/a807458e

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Stereoselective epoxidation of vinyl sulfones and N-(p-tolylsulfonyl)-
vinylsulfoximines derived from isopropylideneglyceraldehyde:
synthesis of chiral building blocks
Andrew D. Briggs,a Richard F. W. Jackson*a and Paul A. Brownb
a Department of Chemistry, Bedson Building, The University of Newcastle,
Newcastle upon Tyne, UK NE1 7RU
b Roche Products Limited, Research Centre, Welwyn Garden City, Hertfordshire, UK AL7 3AY
Received (in Cambridge) 24th September 1998, Accepted 26th October 1998
Epoxidation of N-(p-tolylsulfonyl)vinylsulfoximines using metal alkyl peroxides proceeds with varying degrees
of stereoselectivity, depending both on the metal cation and the steric bulk of the alkyl peroxide group. The
stereochemical outcome of the epoxidation of substrates bearing an allylic asymmetric centre is also dependent
upon the epoxidising agent, and very high levels of stereoselectivity may be obtained in the formation of
sulfonyloxirane 8a. This oxirane was subsequently converted into the sulfonyloxirane 15, a precursor to a useful
chiral functionalised acyl anion equivalent. In addition, the optically pure α-bromothioester 20 was also prepared.
We have been interested for some time in the stereoselective
preparation of heterosubstituted oxiranes using the nucleo-
Results and discussion
Epoxidation of the racemic vinylsulfoximine 1 with potassium
philic epoxidation of electron-deficient alkenes. Diastereo-
selective epoxidation of 1-(p-tolylthio)-1-nitroalkenes derived
from enantiomerically pure α-hydroxy- and α-amino-aldehydes,
followed by stereospecific ring-opening of the product epoxides,
has allowed the stereoselective preparation of derivatives
of β-hydroxy-α-amino acids1 and α-hydroxy-β-amino acids,2
respectively. We have also been interested in the epoxidation of
vinyl sulfones with allylic stereocentres, and have investigated
how the sense of diastereoselectivity is dependent upon the
nature of the epoxidising reagent and the substrate.3,4 In order
to avoid the need for an existing stereogenic centre within the
carbon backbone, we have investigated the low-temperature
epoxidation of N-(p-tolylsulfonyl)vinylsulfoximines using lith-
ium tert-butyl peroxide which gave N-(p-tolylsulfonyl)sulfox-
iminooxiranes with high diastereoselectivity.5 This process has
recently been extended to the corresponding vinyl sulfoxides by
the use of sodium tert-butyl peroxide as the oxidant.6,7
tert-butyl peroxide in tetrahydrofuran (THF) proceeded very
rapidly at Ϫ78 ЊC to give a mixture of the two stereoisomeric
oxiranes 2a and 2b (ratio 10:11). This result is in sharp contrast
to the results obtained using lithium tert-butyl peroxide, in
which oxirane 2a was formed with high stereoselectivity (the
sense of which was established by X-ray crystallography).5 The
fact that such a markedly different result was obtained under
reaction conditions which were closely comparable, provides
very strong support for the suggestion5 that there is an inter-
action between the lithium cation and the sulfoximine group
during lithium tert-butyl peroxide epoxidations. Epoxidation
with lithium triphenylmethyl peroxide proceeded with very high
diastereoselectivity to give 2a, whilst epoxidation with potas-
sium triphenylmethyl peroxide gave 2a and 2b with moderate
selectivity in favour of 2a (4:1) (Scheme 1). Our results are
summarised in Table 1.
These results raise the question as to how the overall stereo-
chemical outcome of a nucleophilic epoxidation of a substrate
containing both a stereogenic centre within the carbon back-
bone and a stereogenic centre within the electron-withdrawing
group might be controlled. Can an appropriate choice lead to
very high levels of stereochemical control? We have therefore
addressed this question by investigating the stereochemical
outcome of the nucleophilic epoxidation of a series of vinyl
sulfones and vinylsulfoximines derived from (R)-isopropyl-
ideneglyceraldehyde. The products of these reactions have then
been converted into useful chiral building blocks to illustrate the
potential value of the process.†
Ph
O
1
S
TolSO2N
i
Ph
O
O
Ph
O
O
S
S
TolSO2N
TolSO2N
2a
2b
Scheme 1 Reagents and conditions: i, MOOR, THF, Ϫ78 ЊC (see Table
1 for reagents).
Since one of the principal methods for controlling the stereo-
chemical outcome of nucleophilic epoxidation reactions
involves changing the nature of the epoxidising agent, we have
further investigated the nucleophilic epoxidation of N-(p-
tolylsulfonyl)vinylsulfoximines using potassium tert-butyl per-
oxide,9 as well as the bulkier reagents, lithium and potassium
triphenylmethyl peroxide.‡
Having established that the stereoselectivity was dependent
upon the choice of epoxidising agent, we set out to investigate
the epoxidation of substrates possessing an additional stereo-
genic centre. As initial substrates, we chose the vinyl sulfone 3
derived from (R)-isopropylideneglyceraldehyde, together with
the two diastereoisomeric N-(p-tolylsulfonyl)vinylsulfoximines
4 and 5 derived from (S)-(ϩ)- and (R)-(Ϫ)-S-methyl-S-phenyl-
N-(p-tolylsulfonyl)sulfoximines, 6 and 7 respectively. The vinyl
sulfone 3 was prepared using the general method reported by
Lee and Oh,11 and the vinylsulfoximines 4 and 5 were prepared
using our previously reported general procedure.5
† The majority of the work described in this manuscript has been
described in a preliminary communication (see ref. 8).
‡ The base catalysed epoxidation of an enone using triphenylmethyl
hydroperoxide has been reported (see ref. 10).
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102
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O
O
X
X
X
O
O
O
O
O
O
3, X = PhO2S
8a, X = PhO2S
8b, X = PhO2S
Ph
Ph
Ph
O
O
O
S
S
S
4, X = TolSO2N
Ph
9a, X = TolSO2N
9b, X = TolSO2N
O
O
O
Ph
Ph
S
S
S
5, X = TolSO2N
10b, X = TolSO2N
10a, X = TolSO2N
O
Ph
Ph
O
S
S
TolSO2N
TolSO2N
6
7
Table 1 Epoxidation of vinylsulfoximine 1
O
O
Reagent
Ratio 2a:2ba
Yield (%)b
O
LiOOtBu
LiOOCPh3
KOOtBu
25:1
25:1
10:11
4:1
97
73
76
74
13
ii
KOOCPh3
a Diastereoisomer ratios were determined from 1H NMR spectra of
crude reaction mixtures; a ratio of 25:1 implies that the minor isomer
could not be detected. b Yields are of purified material.
Ph
O
O
Br
i
S
HO
HO
TolSO2N
O
O
O
O
O
O
Epoxidation of the vinyl sulfone 3 with each of the four epox-
idising agents under our standard conditions at Ϫ20 ЊC in THF
gave a mixture of the anti oxirane 8a and the syn oxirane 8b,
with varying selectivity in favour of the anti compound (Table
2). Of special note was the excellent diastereoselectivity in
favour of 8a obtained using potassium triphenylmethyl per-
oxide, which allows easy access to a potentially useful chiral
building block (vide infra). The results for the epoxidation of
the vinylsulfoximines 4 and 5 at Ϫ78 to Ϫ55 ЊC are also
indicated in Table 2. The results obtained using both lithium
tert-butyl peroxide and lithium triphenylmethyl peroxide are
complex, and not easily rationalised. Clearly there are several
possible sites for lithium coordination in 4 and 5, and the com-
bination of stereogenic centres in 5 combines to make epoxid-
ation with lithium tert-butyl peroxide poorly stereoselective,
whilst the reaction with lithium triphenylmethyl peroxide seems
completely independent of the sulfoximine stereochemistry. In
contrast, epoxidation of all three substrates with potassium
tert-butyl peroxide demonstrates clear reinforcing stereo-
induction for 5 and non-reinforcing stereoinduction for 4.
The anti stereochemistry of 9a was established directly by
X-ray crystal structure analysis.8 Further corroboration of this
result was obtained by conversion of the sulfoximinooxirane 9a
into the corresponding bromohydrin 11 (68%) by our method
involving ring-opening with magnesium bromide–diethyl ether
(to give the α-bromoaldehyde) in the presence of tetra-n-
butylammonium borohydride as in situ reducing agent.12 Pro-
tected butane-1,2,4-triol 12 was obtained (21%) as a by-product
in this process. Treatment of 11 with sodium hydride in diethyl
ether gave the known oxirane 13 (Scheme 2), which was identi-
9a
11
12
Scheme 2 Reagents and conditions: i, MgBr2, Bu4NBH4, Et2O–CH2-
Cl2, 24 h, room temp.; ii, NaH, Et2O, room temp.
of the diol 14,8 obtained by cleavage of the isopropylidene
acetal (vide infra). Following our preliminary communication, a
closely related stereoslective epoxidation of the corresponding
(Z)-vinyl sulfone was reported.17 To illustrate one potential syn-
thetic application of the sulfonyloxirane 8a, we have established
a method for its conversion into (2S,3R)-2-phenylsulfonyl-3-
tert-butyldimethylsilyloxymethyloxirane 15. We have previously
established that the lithio-derivative of this compound, in
racemic form, is a versatile functionalised acyl anion equiv-
alent,18 and may be used for the preparation of unsubstituted
epoxyketones,19 for example. Thus, treatment of the diol 14
with sodium metaperiodate gave the aldehyde 16, which was
reduced with sodium borohydride to the alcohol 17 (Scheme 3).
The enantiomeric purity of the alcohol 17 was established by
conversion into the (R)- and (S)-camphanate esters§ 18a and
18b, which were shown to be diastereoisomerically pure within
1
the limits of detection by H NMR. Finally, protection of the
alcohol 17 as the tert-butyldimethylsilyl ether gave the target 15,
identical by comparison of spectroscopic data with the racemic
compound.18
1
fied by comparison of H NMR data with those in the liter-
ature.13 Other routes to oxirane 13 have been described.14–16
This result confirms unambiguously that the conversion of
9a into 11 occurs with inversion of configuration at C-2.
Analogous treatment of the 6:1 mixture of oxiranes 10a and
10b, obtained by potassium tert-butyl peroxide epoxidation of
5, gave a mixture of 11 and its C-2 epimer (in a ratio of 6:1),
thereby establishing that the major isomer had the same con-
figuration at C-2 as 9a, and therefore had structure 10a.
As further proof of the stereochemical course of these epox-
idation reactions, the α-thiophenyl sulfonyloxirane 19 [prepared
by treatment of 8a with n-BuLi and phenyl benzenethio-
sulfonate (PhSSO2Ph)] was treated with MgBr2 to afford the
corresponding syn α-bromo thioester 20 (Scheme 4). The struc-
ture of this compound was determined by comparison of its 1H
NMR spectra with the corresponding spectra of both diastereo-
The stereochemistry of the anti sulfonyloxirane 8a was estab-
lished by a single crystal X-ray crystallographic determination
§ The IUPAC name for camphanoic acid is hexahydro-3a,4-dimethyl-1-
oxocyclopenta[c]furan-4-carboxylic acid.
4098
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102

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Table 2 Epoxidation of vinyl sulfone 3, and vinylsulfoximines 4 and 5
Alkene
Oxirane
tBuOOLi
Ph3COOLi
tBuOOK
Ph3COOK
3
4
5
8a/8b
9a/9b
10a/10b
4:3 (85%)
25:1 (68%)
2:1 (75%)
5:4 (78%)
25:1 (65%)
25:1 (76%)
4:1 (68%)
2:1 (80%)
6:1 (80%)
25:1 (76%)
25:1 (67%)
7:4 (74%)
O
suspension was stirred at 0 ЊC for 30 min. Diethyl chlorophos-
phate (1.33 g, 1.11 ml, 7.68 mmol) was added dropwise at that
temp., and the yellow solution stirred at 0 ЊC for a further 30
min. The reaction mixture was cooled to Ϫ78 ЊC and (ϩ)-2,3-
O-isopropylidene--glyceraldehyde21,22 (1.0 g, 7.68 mmol) was
added. The resulting solution was stirred at Ϫ78 ЊC until all the
starting material had reacted as judged by TLC analysis. The
solution was quenched using aqueous NH4Cl (saturated, 70 ml)
and was allowed to warm to room temp. The aqueous phase
was extracted with ethyl acetate (2 × 70 ml), and the organic
phase dried and concentrated under reduced pressure. Purifi-
cation of the residue by flash chromatography using hexane–
ethyl acetate (starting with 10:1, then 5:1) gave the vinyl sul-
fone 3 (1.286 g, 4.8 mmol, 75%) as a colourless crystalline solid,
mp 29–30 ЊC, [α]D20 ϩ8.9 (c, 0.9 CH2Cl2). Spectroscopic data were
identical with those previously reported.23
O
PhO2S
i
PhO2S
O
OH
OH
O
8a
14
ii
O
O
iii
PhO2S
OH
PhO2S
CHO
17
iv
16
O
O
t
PhO2S
OSiMe2 Bu
15
(S*)-S-[(4S*)(E)-2-(2,2-Dimethyl-1,3-dioxolan-4-yl)ethenyl]-
N-[(4-methylphenyl)sulfonyl]-S-phenylsulfoximine 4
OR
PhO2S
18a, R = (R)-camphanyl
18b, R = (S)-camphanyl
(S)-S-Methyl-S-phenyl-N-(p-tolylsulfonyl)sulfoximine 6 (3.09
g, 10 mmol) was condensed with (ϩ)-2,3-O-isopropylidene--
glyceraldehyde using the method described in our previous pub-
lication,5 to give the pure vinylsulfoximine 4 as a colourless oil
(2.655 g, 6.3 mmol, 63%), [α]D20 ϩ18.2 (c, 2.0 CH2Cl2); δH (200
MHz, CDCl3) 1.36 (3H, s, MeAMeBC), 1.37 (3H, s, MeAMeBC),
2.40 (3H, s, MeC6H4SO2), 3.71 (1H, dd, 2J 8.5 and 3J 6.5,
CHAHBCH), 4.18 (1H, dd, 2J 8.5 and 3J 7.0, CHAHBCH), 4.72
Scheme 3 Reagents and conditions: i, p-TSA, THF–MeOH, 24 h,
room temp.; ii, NaIO4, MeOH, H2O, Ϫ25 ЊC; iii, NaBH4, MeOH,
Ϫ25 ЊC; iv, tBuMe2SiCl, imidazole, DMF, room temp.
O
i, ii
O
PhO2S
PhO2S
(1H, m, CH H CH), 6.70 (1H, dd, 3J 15.0 and 1.5, CH᎐CHS),
O
᎐
A
B
O
6.99 (1H, dd, 3J 15.0 and 5.0, CH᎐CHS), 7.23–7.27 (2H, m, Ar),
O
iii
PhS
᎐
O
8a
7.52–7.71 (3H, m, Ar), 7.81–7.98 (4H, m, Ar).
19
(R*)-S-[(4S*)(E)-2-(2,2-Dimethyl-1,3-dioxolan-4-yl)ethenyl]-
N-[(4-methylphenyl)sulfonyl]-S-phenylsulfoximine 5
Br
(R)-S-Methyl-S-phenyl-N-(p-tolylsulfonyl)sulfoximine 7 (3.09
g, 10 mmol) was condensed with (ϩ)-2,3-O-isopropylidene--
glyceraldehyde using the method described in our previous pub-
lication,5 to give the pure vinylsulfoximine 5 as a colourless oil
(2.74 g, 6.5 mmol, 65%),5 [α]D20 ϩ1.5 (c, 1.0 CH2Cl2); δH (200
MHz, CDCl3) 1.34 (3H, s, MeAMeBC), 1.40 (3H, s, MeAMeBC),
2.36 (3H, s, MeC6H4SO2), 3.68 (1H, dd, 2J 8.5 and 3J 7.0,
CHAHBCH), 4.18 (1H, dd, 2J 8.5 and 3J 7.0, CHAHBCH), 4.69
(1H, m, CHAHBCH), 6.70 (1H, dd, 3J 14.5 and 1.5, CH=CHS),
PhS
O
O
O
20
Scheme 4 Reagents and conditions: i, BuLi, THF, Ϫ102 ЊC; ii, PhSSO2-
Ph; iii, MgBr2, Et2O, room temp.
isomers of the related α-bromo p-tolylthioester,1 whose struc-
tures had already been unambiguously established by X-ray
crystallography.20
6.99 (1H, dd, 3J 14.5 and 3.5, CH᎐CHS), 7.19–7.26 (2H, m, Ar),
᎐
7.48–7.67 (3H, m, Ar), 7.78–7.96 (4H, m, Ar).
Epoxidation of vinyl sulfone 3 with lithium/potassium tert-butyl/
triphenylmethyl peroxide. General procedures
Experimental
Lithium tert-butyl/triphenylmethyl peroxide. To the alkyl
hydroperoxide (3.3 equiv.) in dry THF (1 ml per 0.1 mmol) at
Ϫ78 ЊC, n-butyllithium (solution in hexanes; 2.5 equiv.) was
added, dropwise, and allowed to stir for 5 min at that temper-
ature. After 5 min, the vinyl sulfone in dry THF (1 ml per 0.1
mmol) was added, dropwise, and allowed to warm to Ϫ20 ЊC
over 10 min. The reaction mixture was stirred for a further 2 h.
After 2 h, the reaction was quenched with aqueous NH4Cl
(10%; 1 ml per 0.2 mmol) and Na2SO3 (10%; 1 ml per 0.4
mmol), and allowed to warm to room temp. The layers were
separated and the product was extracted with CH2Cl2 (3 ×
1 ml per 0.2 mmol). The combined extracts were dried, con-
centrated under reduced pressure and purified by column
General experimental procedures and instrumentation are as
previously described.18 J values are given in Hz. [α]D values are
given in units of 10Ϫ1 deg cm2 gϪ1. Light petroleum refers to that
fraction with boiling point range 40–60 ЊC. All organic extracts
were dried over anhydrous MgSO4, and solvent was removed
using a rotary evaporator.
(S)-(E)-2,2-Dimethyl-4-[2-(phenylsulfonyl)ethenyl]-1,3-
dioxolane 3
n-Butyllithium (5.6 ml, 2.5 M in hexanes, 14.1 mmol) was
added dropwise to a solution of methyl phenyl sulfone (1.00 g,
6.4 mmol) in dry THF (40 ml) at 0 ЊC, and the resulting yellow
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102
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chromatography (5:1 petrol–ethyl acetate) to give the phenyl-
sulfonyloxirane as a colourless solid (or oil).
bined extracts were dried, concentrated under reduced pressure
and purified by column chromatography (3:1 petrol–ethyl
acetate) to give the corresponding sulfoximinooxirane.
Potassium tert-butyl/triphenylmethyl peroxide. To potassium
hydride in dry THF (1 ml per 0.2 mmol) at Ϫ78 ЊC, the alkyl
hydroperoxide (3.3 equiv.) (1 ml per 0.2 mmol) in dry THF was
added, dropwise, and allowed to stir for 5 min at that temper-
ature. After 5 min, the vinyl sulfone in dry THF (1 ml per 0.1
mmol) was added, dropwise, and allowed to warm to Ϫ20 ЊC
over 10 min. The reaction mixture was stirred for a further 2 h.
After 2 h, the reaction was quenched with aqueous NH4Cl
(10%; 1 ml per 0.2 mmol) and Na2SO3 (10%; 1 ml per 0.4
mmol), and allowed to warm to room temp. The layers were
separated and the product was extracted with CH2Cl2 (3 × 1
ml per 0.2 mmol). The combined extracts were dried, concen-
trated under reduced pressure and purified by column chrom-
atography to give the corresponding phenylsulfonyloxirane as a
colourless solid (or oil).
(R)-S-[(4R),2á(R*),3â(S*)-3-(2,2-Dimethyl-1,3-dioxolan-4-
yl)oxiran-2-yl]-N-[(4-methylphenyl)sulfonyl]-S-phenylsulfox-
imine 9a
Treatment of the vinylsulfoximine 4 (0.84 g, 2 mmol) with
lithium tert-butyl peroxide gave the anti-oxirane 9a (0.594 g,
1.36 mmol, 68%) as a colourless crystalline solid, mp 99–101 ЊC,
[α]D20 ϩ86.8 (c, 0.6 CH2Cl2); νmax(film)/cmϪ1 1599, 1497,
1325, 1065; δH (200 MHz, CDCl3) 1.31 (3H, s, MeAMeBC), 1.35
(3H, s, MeAMeBC), 2.40 (3H, s, MeC6H4SO2), 3.59 (1H, dd,
3J 4.0 and 1.5, CH[O]CHS), 3.85–3.92 (1H, m, CHCH2CMe2),
3
4.07–4.17 (2H, m, CHCH2CMe2), 4.57 (1H, d, J 1.5, CH[O]-
CHS), 7.24–7.28 (2H, m, Ar), 7.58–7.79 (3H, m, Ar), 7.82–8.01
(4H, m, Ar); m/z (EI) 422 (Mϩ Ϫ Me, 4.8), 278 (PhSNTs, 20%)
(Found: Mϩ Ϫ Me, 422.0715. C19H20NO6S2 requires 422.0732).
The syn-oxirane 9b, which was obtained by column chrom-
atography from the reaction using potassium tert-butyl per-
oxide as the oxidant, was a colourless oil: [α]D20 Ϫ46.4 (c, 0.7
CH2Cl2); δH (200 MHz, CDCl3) 1.35 (3H, s, MeAMeBC), 1.37
(3H, s, MeAMeBC), 2.40 (3H, s, MeC6H4SO2), 3.89 (1H, dd,
3J 4.0 and 1.5, CH[O]CHS), 4.09 (1H, dd, 3J 9.0 and 6.0,
(4R)-2,2-Dimethyl-4-[2á(R*),3â(S*)-3-(phenylsulfonyl)oxiran-
2-yl]-1,3-dioxolane 8a
Treatment
of
(S)-(E)-2,2-dimethyl-4-[2-(phenylsulfonyl)-
ethenyl]-1,3-dioxolane 3 (0.268 g, 1 mmol) with potassium
triphenylmethyl peroxide according to the procedure described
above, including purification using flash chromatography and
eluting with 8:1 toluene–ethyl acetate, gave the anti-oxirane 8a
(0.241 g, 0.85 mmol, 85%), as a colourless crystalline solid, mp
43–44 ЊC, [α]D20 ϩ54 (c, 1.0 CH2Cl2) (Found: C, 54.8; H, 5.3.
C13H16O5S requires C, 54.9; H, 5.7%); νmax(KBr)/cmϪ1 3070,
2988, 1380, 1315, 1090, 754; δH (200 MHz, CDCl3; standard
Me4Si) 1.34 and 1.44 (6H, 2 × s), 3.75–3.77 (1H, m), 3.84–3.94
(1H, m), 4.11 (3H, m), 7.57–7.76 (3H, m), 7.90–7.97 (2H, m);
δC (50 MHz, CDCl3) 134.6, 129.4, 128.8, 128.4, 110.6, 72.9,
66.4, 66.0, 57.4, 26.4, 25.1; m/z (FAB) 285 (MHϩ, 60%), 259
(80), 227 (40), 199 (40), 125 (60), 77 (60). The syn-oxirane 8b,
which was present as the minor component in the reaction
using lithium tert-butyl peroxide as the oxidant, exhibited the
following 13C NMR data: δC 134.6, 129.4, 128.8, 128.4, 110.6,
72.1, 65.8, 63.1, 56.5, 25.9, 25.5. It was not possible to isolate a
pure sample of 8b.
3
CHCHAHBCMe2), 4.23 (1H, dd, J 9.0 and 7.0, CHCHAHB-
3
CMe2), 4.32 (1H, ddd, J 7.0, 6.0 and 4.0, CHCHAHBCMe2),
3
4.55 (1H, d, J 1.5, CH[O]CHS), 7.23–7.28 (2H, m, Ar), 7.53–
7.77 (3H, m, Ar), 7.83–7.97 (4H, m, Ar). IR and MS data were
indistinguishable from 9a.
(S)-S-[(4R),2á(R*),3â(S*)-3-(2,2-Dimethyl-1,3-dioxolan-4-
yl)oxiran-2-yl]-N-[(4-methylphenyl)sulfonyl]-S-phenylsulfox-
imine 10a
Treatment of vinylsulfoximine 5 (0.84 g, 2 mmol) with lithium
triphenylmethyl peroxide gave the anti-oxirane 10a (0.655 g,
1.50 mmol, 76%) as a colourless oil, [α]D20 Ϫ6.8 (c, 0.75 CH2Cl2);
δH (200 MHz, CDCl3) 1.36 (3H, s, MeAMeBC), 1.45 (3H, s,
MeAMeBC), 2.39 (3H, s, MeC6H4SO2), 3.95 (1H, dd, 3J 2.5 and
3
1.5, CH[O]CHS), 4.06 (1H, dd, J 8.5 and 7.0, CHCHAHB-
3
CMe2), 4.15 (1H, dd, J 8.5 and 6.5, CHCHAHBCMe2), 4.47
3
(1H, ddd, J 7.0, 6.5 and 2.5, CHCHAHBCMe2), 4.55 (1H, d,
Epoxidation of vinylsulfoximines 4 and 5 with lithium/potassium
tert-butyl/triphenylmethyl peroxide. General procedures
3J 1.5, CH[O]CHS), 7.24–7.28 (2H, m, Ar), 7.56–7.75 (3H, m,
Ar), 7.85–8.01 (4H, m, Ar). IR and MS data were indis-
tinguishable from 9a. The syn-oxirane 10b, which was obtained
by column chromatography from the reaction using lithium
tert-butyl peroxide as the oxidant, was a colourless oil: [α]D20
Ϫ58.7 (c, 0.8 CH2Cl2); δH (200 MHz, CDCl3) 1.27 (3H, s,
MeAMeBC), 1.30 (3H, s, MeAMeBC), 2.39 (3H, s, MeC6H4SO2),
3.56 (1H, dd, 3J 3.0 and 1.5, CH[O]CHS), 3.81 (1H, dd, 3J 8.5
and 6.0, CHCHAHBCMe2), 4.12 (1H, dd, 3J 8.5 and 7.0,
CHCHAHBCMe2), 4.27 (1H, ddd, 3J 7.0, 6.0 and 3.0,
Lithium tert-butyl/triphenylmethyl peroxide. To the alkyl
hydroperoxide (1.2 equiv.) in dry THF (1 ml per 0.1 mmol) at
Ϫ78 ЊC, n-butyllithium (solution in hexanes; 1.5 equiv.) was
added, dropwise, and allowed to stir for 5 min at that temper-
ature. After 5 min, the vinylsulfoximine in dry THF (1 ml per
0.1 mmol) was added quickly, such that the temperature of the
reaction mixture rose to Ϫ55 ЊC. The reaction mixture was
warmed to Ϫ35 ЊC over 3 min and cooled to Ϫ78 ЊC, before
being quenched with solid sodium sulfite and stirred for a
further 15 min. After 15 min, the reaction mixture was diluted
with CH2Cl2 and allowed to warm to room temp. and filtered
through Celite and concentrated under reduced pressure to give
the crude product. Purification by column chromatography
(3:1 petrol–ethyl acetate) gave the pure sulfoximinooxirane.
3
CHCHAHBCMe2), 4.58 (1H, d, J 1.5, CH[O]CHS), 7.25–7.28
(2H, m, Ar), 7.56–7.76 (3H, m, Ar), 7.81–7.99 (4H, m, Ar). IR
and MS data were indistinguishable from 9a.
(2R,3R)-2-Bromo-3,4-O-isopropylidenebutane-1,3,4-triol 11
The anti-oxirane 9a (200 mg, 0.475 mmol) was treated with
magnesium bromide–diethyl ether and tetra-n-butylammonium
borohydride as described above at room temp. for 48 h. Normal
work up and purification12 gave the bromohydrin 11 (62 mg,
0.32 mmol, 68%) as a colourless oil, [α]D20 Ϫ9.4 (c, 0.9 CH2Cl2),
νmax(film)/cmϪ1 3434, 797, 619; δH (200 MHz, CDCl3) 1.37
(3H, s, MeAMeBC), 1.49 (3H, s, MeAMeBC), 2.26 (1H, br s,
OH), 3.92–4.02 (3H, m, CH2CHCH[Br]), 4.07–4.18 (2H, m,
CH[Br]CH2OH), 4.42 (1H, dt, 3J 7.5 and 4.5, CH[Br]CH2OH);
m/z (EI) 209 (Mϩ Ϫ Me, 27), 171 (Mϩ Ϫ CH2CH2OH, 20), 155
(Mϩ Ϫ Me2CO2, 25) (Found: Mϩ Ϫ Me, 208.9818. C6H10O3Br
requires 208.9814). (S)-2,2-Dimethyl-4-(2-hydroxyethyl)-1,3-
Potassium tert-butyl/triphenylmethyl peroxide. To potassium
hydride (1.5 equiv.) in dry THF (1 ml per 0.2 mmol) at Ϫ78 ЊC,
the alkyl hydroperoxide (1.2 equiv.) (1 ml per 0.2 mmol) in dry
THF was added, dropwise, and allowed to stir for 5 min at that
temperature. After 5 min, the vinylsulfoximine in dry THF (1
ml per 0.1 mmol) was added, dropwise, and allowed to warm to
Ϫ35 ЊC over 5 min. The reaction mixture was re-cooled to
Ϫ78 ЊC and quenched with aqueous NH4Cl (10%; 1 ml per 0.2
mmol) and Na2SO3 (10%; 1 ml per 0.4 mmol), and allowed to
warm to room temp. The layers were separated and the product
was extracted with CH2Cl2 (3 × 1 ml per 0.2 mmol). The com-
4100
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102

View Article Online
dioxolane 12 (21 mg, 0.15 mmol, 31%) was also isolated as a
colourless oil, νmax(film)/cmϪ1 3444; δH (200 MHz, CDCl3) 1.37
(3H, s, MeAMeBC), 1.43 (3H, s, MeAMeBC), 2.30 (1H, br s,
OH), 3.60 (2H, m, CHCH2CMe2), 3.81 (2H, t, 3J 6.0, CH2OH),
4.10 (2H, dd, 3J 8.0 and 6.0, CH2CH2OH), 4.30 (1H, m,
CH2CHCH2); m/z (EI) 131 (Mϩ Ϫ Me, 85), 101 (Mϩ Ϫ CH2-
CH2OH, 20), 71 (Mϩ Ϫ Me2CO2, 80) (Found: Mϩ Ϫ Me,
131.0675. C6H11O3 requires 131.0642).
solution of sodium metaperiodate (0.531 g, 2.48 mmol) in H2O
(2 ml), and the suspension was stirred for 5 min. The reaction
was diluted with H2O (5 ml), resulting in a colourless solution.
The product was extracted with CH2Cl2 (3 × 10 ml), dried and
concentrated under reduced pressure to the crude product.
Purification by column chromatography (1:1 petrol–ethyl acet-
ate) gave the desired aldehyde 16 (260 mg, 1.23 mmol, 99%) as a
colourless solid, mp 75–76 ЊC, [α]D20 ϩ74.7 (c, 0.9 CH2Cl2);
νmax(film)/cmϪ1 1734, 1586, 1086; δH (200 MHz, CDCl3) 4.06
3
3
(2R,3S)-3,4-Epoxy-1,2-O-isopropylidenebutane-1,2-diol 13
(1H, dd, J 5.5 and 1.5, CH[O]CHSO2Ph), 4.42 (1H, d, J 1.5,
CH[O]CHSO2Ph), 7.57–7.81 (3H, m, Ph), 7.91–7.99 (2H, m,
To sodium hydride (65% in mineral oil; 8.5 mg, 0.226 mmol)
in dry Et2O (1 ml), (2R,3R)-2-bromo-3,4-O-isopropylidene-
butane-1,3,4-triol 11 (50 mg, 0.226 mmol) in Et2O (1 ml) was
added and the mixture was stirred for 30 min. Phosphate buffer
(pH 7; 3 ml) was added and the mixture was extracted with
Et2O (3 × 5 ml). The combined extracts were dried and concen-
trated under reduced pressure. Purification by column chrom-
atography (5:1 petrol–ethyl acetate) gave the desired product
(23 mg, 0.156 mmol, 69%) 13 as a colourless oil, [α]D20 ϩ11.6 (c,
2.3 EtOH) {lit.13 value [α]D20 ϩ9.2 (c, 3.04 MeOH)}; δH (500 MHz,
CDCl3) 1.32 (3H, s, MeAMeBC), 1.41 (3H, s, MeAMeBC), 2.61
(1H, dd, 3J 5.0 and 2.5, CH[O]CHAHB), 2.81 (1H, dd, 3J 5.0 and
4.0, CH[O]CHAHB), 2.98 (1H, ddd, 3J 6.5, 4.0 and 2.5,
CH[O]CHAHB), 3.76 (1H, m, CHCHAЈHBЈCMe2), 3.85 (1H, dd,
3J 8.5 and 6.0, CHCHAЈHBЈCMe2), 4.06 (1H, dd, 3J 8.5 and 6.5,
CHCHAЈHBЈCMe2). Other spectroscopic data were identical to
those reported.13,15
Ph), 9.14 (1H, d, J 5.5, CHO); m/z (EI) 213 (MHϩ, 7), 212
3
(Mϩ, 8) (Found: Mϩ, 212.0138. C9H8O4S requires 212.0132).
(2R)-trans-3-(Phenylsulfonyl)oxirane-2-methanol 17
Sodium borohydride (42 mg, 1.13 mmol) was added to a solu-
tion of the aldehyde 16 (200 mg, 0.943 mmol) in MeOH (4 ml)
at Ϫ25 ЊC, and stirred for 90 min. Phosphate buffer (pH 7, 3 ml)
was added and the product was extracted with CH2Cl2 (3 × 10
ml). The combined extracts were dried and concentrated under
reduced pressure. Purification by column chromatography (1:1
petrol–ethyl acetate) gave the alcohol 17 (114 mg, 0.66 mmol,
70%) as a colourless solid, mp 73–74 ЊC, [α]D20 ϩ94.0 (c, 1.0
CH2Cl2) (Found: C, 50.7; H, 4.9. C9H10O4S requires C, 50.5;
H, 4.7%); νmax(KBr disc)/cmϪ1 3511, 1583, 1086; δH (200 MHz,
CDCl3) 3.85 (2H, m, CH2OH), 4.05 (1H, m, CH[O]CHSO2Ph),
3
4.26 (1H, d, J 1.6, CH[O]CHSO2Ph), 7.57–7.78 (3H, m, Ph),
The two diastereoisomers (2S,3R) and (2R,3R) were pre-
pared for comparison by the literature procedure of White
et al.,15 and the high field NMR data in which each proton can
be clearly distinguished is listed below.
7.93–7.98 (2H, m, Ph).
(2R)-trans-tert-Butyl(dimethyl){[3-(phenylsulfonyl)oxiran-2-yl]-
methoxy}silane 15
(2R,3S)-3,4-Epoxy-1,2-O-isopropylidenebutane-1,2-diol was
prepared as a colourless oil, [α]D20 ϩ11.45 (c, 2.2 EtOH); δH (500
MHz, CDCl3) 1.32 (3H, s, MeAMeBC), 1.41 (3H, s, MeAMeBC),
tert-Butyldimethylsilyl chloride (79 mg, 0.526 mmol) and imid-
azole (36 mg, 0.526 mmol) were added to a solution of the
alcohol 17 (100 mg, 0.439 mmol) in DMF (1 ml), and the mix-
ture was stirred at room temp. for 40 h. The reaction mixture
was diluted with petrol (10 ml) and washed with saturated
aqueous sodium hydrogen carbonate (3 ml), brine (3 ml) and
water (5 × 25 ml). The petrol extract was dried and concen-
trated under reduced pressure to give the silyl ether 15 (111 mg,
0.355 mmol, 81%) as a colourless oil, [α]D20 ϩ49.0 (c, 1.8 CH2Cl2).
Spectroscopic data were identical to those reported.18
3
2.60 (1H, dd, J 5.0 and 2.5, CH[O]CHAHB), 2.80 (1H, dd,
3
3J 5.0 and 4.0, CH[O]CHAHB), 2.91 (1H, ddd, J 7.0, 4.0 and
2.5, CH[O]CHAHB), 3.81 (1H, dd, 3J 8.5 and 6.5, CHCHAЈHBЈ-
CMe2), 3.87 (1H, m, CHCHAЈHBЈCMe2), 4.02–4.11 (1H, dd,
3J 8.5 and 6.5, CHCHAЈHBЈCMe2).
(2R,3R)-3,4-Epoxy-1,2-O-isopropylidenebutane-1,2-diol was
prepared as a colourless oil, [α]D20 ϩ1.2 (c, 2.4 EtOH); δH (500
MHz, CDCl3) 1.35 (3H, s, MeAMeBC), 1.41 (3H, s, MeAMeBC),
3
2.65 (1H, dd, J 5.0 and 2.5, CH[O]CHAHB), 2.79 (1H, dd,
3
3J 5.0 and 4.0, CH[O]CHAHB), 3.02 (1H, ddd, J 6.5, 4.0 and
Determination of optical purity of (2R)-trans-3-(phenyl-
sulfonyl)oxirane-2-methanol 17; preparation of 3-(R)- and
(S)-camphanoates of trans-3-hydroxymethyl-2-
phenylsulfonyloxirane. General procedure
2.5, CH[O]CHAHB), 3.84 (1H, dd, 3J 8.5 and 5.5, CHCHAЈHBЈ-
3
CMe2), 3.96 (1H, m, CHCHAЈHBЈCMe2), 4.08 (1H, dd, J 8.5
and 6.5, CHCHAЈHBЈCMe2).
(1R)-1-[2á(R*),3â(S*)-3-(Phenylsulfonyl)oxiran-2-yl]ethane-
1,2-diol 14
(R)- or (S)-Camphanic acid chloride (1.3 equiv.) and N,N-
dimethylaminopyridine (1.3 equiv.) were added to a solution of
the alcohol 17 in dry CH2Cl2 (1 ml per 0.1 mmol). The reaction
mixture was stirred at room temp. for 16 h. After 16 h, the
reaction mixture was concentrated under reduced pressure and
the residue was treated with diethyl ether (1 ml per 0.1 mmol)
and aqueous HCl (1.0 M; 2 ml per 0.1 mmol). The mixture was
vigorously stirred for 10 min. The layers were separated and the
ethereal layer was washed with saturated aqueous sodium
carbonate (3 × 3 ml per 0.1 mmol). The etheral layer was dried,
filtered through a small pad of silica and concentrated under
reduced pressure to give the camphanoate ester as a colourless
oil.
Toluene-p-sulfonic acid (30 mg, 0.176 mmol) was added to a
solution of the anti-oxirane 8a (0.5 g, 1.76 mmol) in dry THF
(10 ml) and dry MeOH (10 ml). The reaction mixture was
stirred for 16 h at room temp. Solid NaHCO3 (ca. 0.2 g) was
added, the suspension was washed with MeOH (10 ml) and
concentrated under reduced pressure. Purification by column
chromatography (1:1 petrol–ethyl acetate to pure ethyl acetate
gradient) gave the corresponding diol 14 (0.341 g, 1.41 mmol,
80%) as a colourless solid, mp 143–144 ЊC, [α]D20 ϩ62.4 (c, 1.0
MeOH) (Found: C, 48.9; H, 4.8. C10H12O5S requires C, 49.2; H,
5.0%); νmax(KBr disc)/cmϪ1 3494, 3380, 1584, 1086; δH (200
MHz, CD3OD) 3.59 (2H, m, CH2OH), 3.67 (1H, dd, 3J 3.5 and
1.5, CH[O]CHSO2Ph), 3.74 (1H, m, CH[OH]CH2OH), 4.39
(1H, d, 3J 1.5, CH[O]CHSO2Ph), 7.62–7.78 (3H, m, Ph), 7.91–
7.95 (2H, m, Ph); m/z (EI) 243 (MHϩ, 10), 196 (28), 142 (70)
and 78 (100).
Camphanoate 18a
This compound was prepared from (R)-camphanic acid chlor-
ide and alcohol 15 according to the above procedure; δH (200
MHz, CDCl3) 0.96 (3H, s, MeCC[MeAMeB]), 1.04 (3H, s,
MeAMeBC), 1.12 (3H, s, MeAMeBC), 1.59–1.75 (1H, m), 1.85–
2.09 (2H, m), 2.33–2.47 (1H, m), 3.93–3.97 (1H, m, CH[O]-
CHSO2Ph), 4.17 (1H, d, 3J 1.5, CH[O]CHSO2Ph), 4.26 (1H, dd,
(2R)-trans-3-(Phenylsulfonyl)oxiranecarbaldehyde 16
Diol 14 (300 mg, 1.24 mmol) in MeOH (4 ml) was added to a
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102
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3J 13.0 and 4.5), 4.70 (1H, dd, 3J 13.0 and 3.0), 7.58–7.78 (3H,
m, Ph), 7.92–7.97 (2H, m, Ph).
Acknowledgements
We thank the EPSRC for a CASE studentship (A. D. B.), Dr
P. L. Bailey and Dr S. P. Standen for preliminary experiments,
and Roche Products for support. We also thank Dr M. N. S.
Hill, Mrs L. Cook, Mr D. Dunbar and Mr S. Addison for
obtaining spectroscopic and other data, and Mr E. Hart for
invaluable technical assistance.
Camphanoate 18b
This compound was prepared from (S)-camphanic acid chlor-
ide and alcohol 15 according to the above procedure; δH (200
MHz, CDCl3) 0.90 (3H, s, MeCC[MeAMeB]), 1.05 (3H, s,
MeAMeBC), 1.11 (3H, s, MeAMeBC), 1.61–1.76 (1H, m), 1.86–
2.10 (2H, m), 2.35–2.49 (1H, m), 3.93–3.97 (1H, m, CH[O]-
CHSO2Ph), 4.17 (1H, d, 3J 1.5, CH[O]CHSO2Ph), 4.27 (1H, dd,
3J 13.0 and 4.5), 4.71 (1H, dd, 3J 13.0 and 3.0), 7.58–7.78 (3H,
m, Ph), 7.92–7.96 (2H, m, Ph).
References
1 R. F. W. Jackson, N. J. Palmer, M. J. Wythes, W. Clegg and M. R. J.
Elsegood, J. Org. Chem., 1995, 60, 6431.
2 L. Ambroise and R. F. W. Jackson, Tetrahedron Lett., 1996, 37,
2311.
The key signals for comparison are at δ 0.90 and 0.96.
3 R. F. W. Jackson, S. P. Standen, W. Clegg and A. McCamley,
J. Chem. Soc., Perkin Trans. 1, 1995, 141.
4 R. F. W. Jackson, S. P. Standen and W. Clegg, J. Chem. Soc., Perkin
Trans. 1, 1995, 149.
(4R)-2,2-Dimethyl-4-[2á(R*),3â(R*)-3-(phenylsulfonyl)-3-
(phenylthio)oxiran-2-yl]-1,3-dioxolane
n-Butyllithium (2.0 M; solution in hexanes; 0.42 ml, 0.84 mmol)
was added, dropwise, to a solution of the oxirane 8a (200 mg,
0.704 mmol) in dry THF (6 ml) at Ϫ102 ЊC, and the mixture
warmed to Ϫ95 ЊC and stirred at that temperature for 8 min.
Phenyl benzenethiosulfonate24 (264 mg, 1.06 mmol) in dry
THF (4 ml) was added, dropwise. The reaction mixture was
allowed to warm to Ϫ80 ЊC and stirred for 5 min, before being
quenched with aqueous NH4Cl (10%; 6 ml) and the mixture
was allowed to warm to room temp. The mixture was extracted
with CH2Cl2 (3 × 20 ml) and the combined extracts were dried,
and concentrated under reduced pressure. Purification by
column chromatography (3:1 petrol–ethyl acetate) gave oxirane
19 (191 mg, 0.486 mmol, 69%) as a colourless solid, mp 56–
57 ЊC; [α]D20 ϩ26.9 (c, 0.9 CH2Cl2); νmax(film)/cmϪ1 1584, 1088; δH
(200 MHz, CDCl3) 1.35 (3H, s, MeAMeBC), 1.49 (3H, s,
5 P. L. Bailey, W. Clegg, R. F. W. Jackson and O. Meth-Cohn,
J. Chem. Soc., Perkin Trans. 1, 1993, 343.
6 R. F. de la Pradilla, S. Castro, P. Manzano, J. Priego and A. Viso,
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7 R. F. de la Pradilla, S. Castro, P. Manzano, M. Martin-Ortega,
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63, 4954.
8 A. D. Briggs, R. F. W. Jackson, W. Clegg, M. R. J. Elsegood, J. Kelly
and P. A. Brown, Tetrahedron Lett., 1994, 35, 6945.
9 W. C. Still, J. Am. Chem. Soc., 1979, 101, 2493.
10 E. J. Corey, M.-C. Kang, M. C. Desai, A. K. Ghosh and I. N.
Houpis, J. Am. Chem. Soc., 1988, 110, 649.
11 J. W. Lee and D. Y. Oh, Synth. Commun., 1989, 19, 2209.
12 P. L. Bailey, A. D. Briggs, R. F. W. Jackson and J. Pietruszka,
J. Chem. Soc., Perkin Trans. 1, 1998, 3359.
13 C. Gravier-Pelletier, J. Dumas, Y. Le Merrer and J.-C. Depezay,
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14 E. Abushanab, P. Vemishetti, R. W. Leiby, H. K. Singh, A. B.
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15 J. D. White, R. A. Badger, H. S. Kezar III, A. J. Pallenberg and
G. A. Scheihser, Tetrahedron, 1989, 45, 6631.
3
MeAMeBC), 4.04 (1H, d, J 7.0, CHCH[O]CH2), 4.13 (1H, m,
CHCH[O]CH2), 4.35 (2H, m, CHCH[O]CH2), 7.11–7.63 (8H,
m, Ar), 7.77–7.82 (2H, m, Ar); m/z (EI) 377 (Mϩ Ϫ Me, 20), 317
(5), 282 (10).
16 M. Pottie, J. Van der Eycken and M. Vandewalle, Tetrahedron:
Asymmetry, 1991, 2, 329.
17 Y. Mori, K. Yaegashi and H. Furukawa, J. Am. Chem. Soc., 1996,
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(2S)-S-Phenyl 2-bromo-2-[(4R*)-2,2-dimethyl-1,3-dioxolan-4-
yl]ethanethioate 20
The oxirane 19 (60 mg, 0.153 mmol) in dry CH2Cl2 (1 ml) was
added to a solution of magnesium bromide–diethyl ether (47
mg, 184 mmol) in dry diethyl ether (2 ml) at room temp., and
stirred for 16 h. Phosphate buffer (pH 7; 3 ml) was added and
the mixture was extracted with Et2O (3 × 5 ml). The combined
extracts were dried and concentrated under reduced pressure.
Purification by column chromatography (5:1 petrol–ethyl acet-
ate) gave the α-bromo thioester 20 (44 mg, 0.135 mmol, 88%)
as a colourless solid, mp 60–61 ЊC; νmax(film)/cmϪ1 1692, 1478,
747; δH (200 MHz, CDCl3) 1.38 (3H, s, MeAMeBC), 1.49 (3H, s,
18 M. Ashwell, W. Clegg and R. F. W. Jackson, J. Chem. Soc., Perkin
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19 S. F. C. Dunn and R. F. W. Jackson, J. Chem. Soc., Perkin Trans. 1,
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3
MeAMeBC), 3.98 (1H, dd, J 9.0 and 5.0, CHAHBCHCH[Br]),
24 B. M. Trost, T. N. Salzmann and K. Hiroi, J. Am. Chem. Soc., 1976,
98, 4887.
4.15 (1H, dd, 3J 9.0 and 6.0, CHAHBCHCH[Br]), 4.49–4.63
(2H, m, CHAHBCHCH[Br]), 7.44 (5H, s, Ph); m/z (EI)
331 (MHϩ, 5), 315 (Mϩ Ϫ CH3, 6), 257 (Mϩ Ϫ Me2C, CH2OH,
20) (Found: Mϩ Ϫ CH3, 314.9687. C12H12O3SBr requires
314.9683).
Paper 8/07458E
4102
J. Chem. Soc., Perkin Trans. 1, 1998, 4097–4102