A new general route to acceptor-substituted vinyloxiranes via siloxyoxiranes - Novel promising synthetic building-blocks

Article abstract of DOI:10.1055/s-2002-19796

Epoxidation of silyl enol ethers 2a,b with dimethyldioxirane yields siloxyoxiranes 3a,b. Anions 4a-d lead to nucleophilic ring-opening in the acetal position C-1 of 3 to give diols 5a-d. Monotosylation and cyclisation provide acceptor-substituted vinyloxiranes 6a-d.

Full text of DOI:10.1055/s-2002-19796

PAPER
191
A New General Route to Acceptor-Substituted Vinyloxiranes via
Siloxyoxiranes – Novel Promising Synthetic Building-Blocks
A
cceptor-Subst
r
ituted
V
i
n
nyloxirane
s
st Schaumann,* Frank Tries
Institut für Organische Chemie, Technische Universität Clausthal, Leibnizstraße 6, 38678 Clausthal-Zellerfeld, Germany
Fax +49(5323)722858; E-mail: ernst.schaumann@tu-clausthal.de
Received 16 August 2001; revised 2 November 2001
a
b
90%
Abstract: Epoxidation of silyl enol ethers 2a,b with dimethyldiox-
irane yields siloxyoxiranes 3a,b. Anions 4a–d lead to nucleophilic
ring-opening in the acetal position C-1 of 3 to give diols 5a–d.
Monotosylation and cyclisation provide acceptor-substituted viny-
loxiranes 6a–d.
O
77-92%
OSiR12R2
3a, b
OSiR12R2
2a, b
Li
O
1
Acc
Li
Key words: dimethyldioxirane, silyl enol ethers, siloxyoxiranes,
vinyloxiranes, epoxide ring opening
OH
4a-d
O
Acc
Acc
d
c
54-72%
15-57%
OH
Vinyloxiranes are very useful building blocks in organic
synthesis. Their fully functionalised carbon backbone
opens up a broad range of reaction possibilities.1 Thus, the
general synthetic utility of oxiranes is further enhanced
and numerous uses of vinyloxiranes as intermediates in
natural-product synthesis have been reported.2
5a-d
6a-d
R1
R2
Acc
Compound
2a
2b
3a
Me
Ph
Ph
Ph
Ph
Herein, we describe a conceptually new route to a novel
type of vinyloxiranes 6 with a sulfide or silyl substituent
in the internal olefinic position (Scheme). Vinyloxiranes
with this substitution pattern are difficult to access by the
usual oxidation routes starting from the corresponding
butadienes3 as these oxidation methods inevitably affect
sulfide functions to give sulfoxides or even sulfones. Sim-
ilarly, the presence of a silyl substituent on a butadiene di-
rects the oxidation to the silicon-substituted double bond.4
To avoid these problems, another strategy was required
for the synthesis of acceptor-substituted vinyloxiranes 6,
i.e vinyloxiranes with a carbanion-stabilising heterosub-
Me
Ph
Ph
3b
4a, 5a, 6a
4b, 5b, 6b
SPh
SiMe3
4c, 5c, 6c
4d, 5d, 6d
SiMe2Ph
SiPh3
Scheme Reagents and conditions: a) Et3N, DMF, ClSiR1 R2, r.t., 2
d; b) DMDO/acetone, CH2Cl2, –78 °C, 2 h; c) Et2O, –78 °C, r.t., 12 h;
d) i. Et3N, p-TosCl, 4-DMAP, CH2Cl2, 0 °C, 12 h, ii. K2CO3, MeOH,
2
stituent. The idea to employ a ring-closure reaction rather r.t., 1 h
than an oxidation makes enediols 5 our crucial intermedi-
ates as they should readily provide the oxirane unit via
usually yields -hydroxy carbonyl compounds (Rubottom
monotosylation and base-controlled cyclisation. On the
other hand, an obvious synthetic route to enediols 5 in-
volves addition of a vinyl anion to glycolaldehyde, prob-
ably modified by a protective group for the alcohol
function.
reaction).5 Siloxyoxiranes 3 so far can only be isolated if
they are ketone derivatives loaded with substituents in the
-position and under neutral conditions using sulfonyl ox-
aziridines.6 It now turned out that simple aldehyde-de-
rived siloxy epoxides can be isolated in the case of a bulky
silyl residue and neutral reaction conditions employing
dimethyldioxirane7 (DMDO) as reagent. This is shown
here for gylcolaldehyde equivalents 3a,b, but the ap-
proach also works for equivalents of higher -hydroxy al-
dehydes.8
However, the need of laborious protective group chemis-
try is an obvious drawback of the starting material glycol-
aldehyde. Moreover, this aldehyde has an unfortunate ten-
dency to polymerise. An attractive alternative would be
the use of a siloxyoxirane 3 which may be looked upon as
an equivalent of glycolaldehyde. Oxidation of silyl enol
ethers should lead to oxiranes 3. However, attempted ep-
oxidation of trimethylsilyl enol ethers 2 using peracids
Siloxyoxiranes 3a,b were prepared from silyl enol ethers
2a,b by epoxidation with dimethyldioxirane at –78 °C in
a high-yield reaction (Scheme). Especially product 3b can
be stored at –25 °C for weeks without appreciable deteri-
oration. As to the formation of the present reaction part-
ners, anion 4a9 was obtained by deprotonation of the
Synthesis 2002, No. 2, 01 02 2002. Article Identifier:
1437-210X,E;2002,0,02,0191,0194,ftx,en;E15601SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

192
E. Schaumann, F. Tries
PAPER
1H NMR (200 MHz): = 4.22 (dd, 2J = 1.0, 3J = 5.8 Hz, 1 H,
H2C=CH), 4.65 (dd, J = 1.0, J = 13.6 Hz, 1 H, H2C=CH), 6.55
(dd, 3J = 5.8, 3J = 13.6 Hz, 1 H, H2C=CHOSi), 7.36–7.71 [m, 15 H,
Si(C6H5)3].
13C NMR (50 MHz): = 146.0 (+, C=CHOSi), 135.4, 130.4, 128.0
(+, CHarom), 133.0 (0, Carom), 95.8 (–, H2C=CH).
corresponding vinyl sulfide at the -position with BuLi/
TMEDA, while metalation of the corresponding -bro-
movinylsilanes with t-BuLi/TMEDA yielded anions 4b–
d.10,11 Addition of freshly prepared 3 to 4 gave the expect-
ed diols 5a–d in 15–57% yield. In all cases, in situ desily-
lation was observed. Steric hindrance to nucleophilic
attack at the acetalic position and electronic reasons may
account for the relatively low yields. Finally, monotosyla-
tion with p-TosCl, triethylamine and 4-DMAP in anhy-
drous dichloromethane and cyclisation with potassium
carbonate in anhydrous methanol gave the desired accep-
tor-substituted vinyloxiranes 6a–d in good yields.
2
3
Anal. Calcd for C20H18OSi (302.4): C, 79.44, H; 6.00; found, C,
79.35; H, 6.01.
Epoxidation of Silyl Enol Ethers 2a,b; General Procedure
To a solution of silyl enol ether 2 (1.0 equiv) in CH2Cl2 (10 mL) was
slowly (1–3 drops/sec) added dimethyldioxirane solution7 (1.2
equiv) at –78 °C. The mixture was stirred for 1 h and then concen-
trated at 1 mbar first at –78 °C, and subsequently without a cooling
bath. After CH2Cl2 and acetone had been removed, the residue was
dissolved in either pentane or Et2O, dried (Na2SO4), and concentrat-
ed again in vacuo at r.t. The crude product can be used without fur-
ther purification and for 3b storage at –25 °C is possible, but
immediate use is recommended.
Beyond the present synthetic use, siloxyoxiranes 3 de-
serve general interest as equivalents of glycolaldehyde.
Moreover, multifunctional vinyloxiranes 6 are now in our
hands and promise a rich chemistry.
All experiments were performed under dry N2. THF was distilled
from sodium benzophenone ketyl prior to use. CH2Cl2 was distilled
from CaH2. Column chromatography was carried out on Merck sil-
ica gel (70–230 mesh). Petroleum ether (PE) with the boiling range
60–70 °C was always used in the chromatographic separations. An-
alytical TLC was performed on Merck silica gel 60 PF254 plates (vi-
sualisation with UV light or 4-methoxybenzaldehyde spray
reagent). Mps are uncorrected. IR spectra were recorded on a PYE
Unicam SP 3-200 spectrometer and on a Bruker Vektor 22 instru-
ment. NMR spectra were obtained on Bruker ARX 400 or DPX 200
spectrometers in CDCl3 using TMS as an internal standard Assign-
ments of 13C NMR signals were supported by broadband decoupled
DEPT.
Dimethyl(oxiranyloxy)phenylsilane (3a)
Prepared from 2a (1.78 g, 10 mmol); yield: 90% (determined by
GC); colorless oil.
IR (film): 3070 (oxirane), 1591 (C=Carom), 1428, 1397, 1288 (ox-
irane), 1119 (C–O), 1255 (SiMe2), 996, 864, 832, 731, 701 cm–1.
1H NMR (400 MHz): = 0.35, 0.38 [s each, 3 H, Si(CH3)2], 2.05
3
2
3
2
(dd, J = 2.4, J = 4.6 Hz, 1 H, CH2O), 2.48 (dd, J = 1.2, J = 4.6
Hz, 1 H, CH2O), 4.50 (dd,, 3J = 1.2, 3J = 2.4 Hz, 1 H, CHO), 7.17–
7.25 (m, 3 H, ArH), 7.54–7.60 (m, 2 H, ArH).
13C NMR (100 MHz): = 137.7 (0, Carom), 134.3, 130.6, 128.7 (+,
CHarom), 73.7 (+, CHO), 48.2 (–, CH2O), –0.5, –0.7 [+, Si(CH3)2].
-Lithiophenylvinylsulfide (4a),9 -bromovinylsilanes10 and the
corresponding -lithiovinylsilanes 4b–d10,11 were prepared accord-
ing to literature procedures.
Oxiranyloxy(triphenyl)silane (3b)
Prepared from 2b (3.025g, 10 mmol); yield: 3.142 g ( 90%, deter-
mined by GC); solid.
IR (film): 3067 (oxirane), 2855, 1589 (C=Carom), 1428, 1388 (O–
CO), 1282, 1118s (C–O), 1026 (SiPh3), 1261, 872, 801 (oxirane),
740, 714, 699 cm–1.
1H NMR (400 MHz): = 2.07 (dd, 3J = 2.0, 2J = 4.6 Hz, 1 H,
CH2O), 2.63 (dd, 3J = 1.0, 2J = 4.6 Hz, 1 H, CH2O), 4.76 (dd,
3J = 1.0, 3J = 2.0 Hz, 1 H, CHO), 7.15–7.25, (m, 9 H, ArH), 7.75–
7.85 (m, 6 H, ArH).
Silyl Enol Ethers 2a,b; General Procedure
A solution of chlorosilane (1.0 equiv) in DMF (1 mL/mmol) was
treated with Et3N (2.0 equiv) and freshly distilled 1 (1.0 equiv) at r.t.
The reaction mixture was stirred for 48 h. The insoluble residue was
removed by filtration over Celite. The organic phase was washed
with aq sat. NaHCO3 solution and brine, dried (MgSO4) and con-
centrated in vacuo.
13C NMR (100 MHz): = 135.8, 130.6, 128.3 (+, CHarom), 133.8 (0,
Dimethyl(phenyl)vinyloxysilane (2a)
Prepared from 1 (0.22 g, 5 mmol). Kugelrohr distillation (bp 60 °C/
0.01 Torr) gave 2a (0.684 g, 77%) as a colorless oil.
Carom), 73.8 (+, CHO), 48.0 (–, CH2O).
Nucleophilic Oxirane-Opening of Epoxides 3 by Acceptor-
Substituted -Lithioethenes 4; General Procedure
IR (film): 2963, 1632 (C=C), 1592 (C=Carom), 1428, 1319, 1256,
1175, 1120, 1018, 987, 948, 827 (SiMe2Ph), 792, 732, 641 cm –1
.
An acceptor-substituted -lithioethene 4 (1 equiv) in THF (2 mL/
mmol) was treated dropwise at –60 °C (– 30 °C for 4a) with 3a or
3b (1 equiv) dissolved in THF (3 mL/mmol). The reaction mixture
was allowed to warm slowly to r.t. and stirred for 12 h. For workup,
it was hydrolysed with a mixture of Et2O–aq sat. NH4Cl solution
(1:1). The aqueous phase was separated and extracted twice with
Et2O and washed with brine. The combined organic layers were
dried (MgSO4) and concentrated in vacuo.
1H NMR (200 MHz): = 0.32 [s, 6 H, Si(CH3)2], 4.00 (dd, 2J = 1.0,
3J = 6.0 Hz, 1 H, =CH2), 4.33 (dd, 2J = 1.0, 3J = 13.6 Hz, 1
3
3
H, =CH2), 6.25 (dd, J = 6.0, J = 13.6 Hz, 1 H, =CH), 7.20–7.49
(m, 5 H, C6H5).
13C NMR (50 MHz): = 145.8 (+, =CH), 136.5 (0, Carom), 133.4,
133.0, 127.9 (+, CHarom), 95.2 (–, = CH2), –1.8 [+, Si(CH3)2].
Anal. Calcd for C10H14OSi (178.3): C, 67.38; H, 7.92; found, C,
67.41; H, 8.41.
3-(Phenylsulfanyl)but-3-ene-1,2-diol (5a)
Prepared from 4a and freshly prepared 3a; flash chromatography
(PE–EtOAc, 20:1 10:1 5:1 1:1) gave 5a (448 mg, 30%) as
a yellow oil. In an analogous reaction with 3b (0.545 g, 4 mmol),
the same work up gave 5a (448 mg, 57%).
Triphenyl(vinyloxy)silane (2b)
Prepared from 1 (2.203 g, 50 mmol). Flash chromatography (PE)
gave 2b (13.947 g, 92%) as colorless crystals; mp 82–84 °C.
IR (film): 3383 (OH), 1608, 1583 (C=C), 749, 692 cm–1.
IR (KBr): 3067, 3053, 1631 (C=C), 1589 (C=Carom), 1428, 1313,
1171, 1154, 1130, 1106, 996, 951, 841 (SiPh3), 766, 739, 715, 698
cm–1.
Synthesis 2002, No. 2, 191–194 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Acceptor-Substituted Vinyloxiranes
193
1H NMR (200 MHz): = 2.51 (s, 1 H, CH2OH), 3.06 (s, 1 H,
mmol), was added K2CO3 (1.1 equiv). The mixture was stirred for
several min at r.t. and the reaction monitored by TLC. If tosylate
could still be detected, more K2CO3 was added. For workup, Et2O
(45 mL/mmol) was added and the mixture was filtered. The organic
phase was washed with aq sat. NH4Cl solution, H2O, brine, dried
(MgSO4) and concentrated in vacuo.
3
2
CHOH), 3.64 (dd, J = 6.6, J = 11.6 Hz, 1 H, CH2OH), 3.76 (dd,
3J = 3.2, 2J = 11.6 Hz, 1 H, CH2OH), 4.24 (dd, 3J = 3.2, 3J = 6.6 Hz,
1 H, CHOH), 5.09 (s, 1 H, =CH2), 5.55 (d, 4J = 1.0 Hz, 1 H, =CH2),
7.19–7.42 (m, 5 H, ArH).
13C NMR (50 MHz): = 144.4 (0, Colef), 132.2 (0, Carom), 132.7,
129.3, 128.0 (+, CHarom), 115.3 (–, CH2 olef), 74.3 (+, CHOH), 65.7
(–, CH2OH).
(1-Phenylsulfanylvinyl)oxirane (6a)
Prepared from 5a (1.82 g, 5.2 mmol). Flash chromatography (PE–
EtOAc, 40:1 5:1 1:1) gave 6a (581 mg, 63%) as a yellow oil.
IR (film): 1605, 1583 (C=C), 1477, 1439, 1024, 916, 748, 691 cm–1.
3-(Trimethylsilyl)but-3-ene-1,2-diol (5b)
Anion 4b was generated from -bromovinyltrimethylsilane10 (1.79
g, 10 mmol), then BF3·Et2O (10 mmol) and freshly prepared 3a
were added. Flash chromatography (PE/EtOAc, 20:1 10:1 5:1
1:1) gave 5b (528 mg, 33%) as a colorless oil.
1H NMR (400 MHz): = 2.69 (dd, 3J = 2.6, 2J = 5.6 Hz, 1 H,
3
2
CH2O), 2.78 (dd, J = 4.0, J = 5.6 Hz, 1 H, CH2O), 3.42 (ddd,
4J = 0.6, 3J = 2.6, 3J = 4.0 Hz, 1 H, CHO), 5.12 (s, 1 H, =CH2), 5.53
(d, 4J = 0.6 Hz, 1 H, =CH2), 7.15–7.40 (m, 5 H, ArH).
IR (film): 3377 (OH), 1714, 1655 (C=C), 1409, 1250, 1077, 1030,
944, 841, 760, 694 cm–1.
13C NMR (100 MHz): = 141.6 (0, Colef), 132.4 (0, Carom), 132.4,
129.2, 127.8 (+, CHarom), 116.4 (–, =CH2), 53.1 (+, CHO), 49.1 (–,
CH2O).
1H NMR (200 MHz): = 0.12 [s, 9 H, Si(CH3)3], 3.42 (dd, 3J = 8.4,
3
2
2J = 11.4 Hz, 1 H, CH2OH), 3.62 (dd, J = 3.2, J = 11.4 Hz, 1 H,
2
4
CH2OH), 4.42 (m, 1 H, CHOH), 5.51 (dd, J = 1.2, J = 1.6 Hz, 1
H, =CH2), 5.89 (dd, 2J = 1.2, 4J = 1.6 Hz, 1 H, =CH2).
Trimethyl(1-oxiranylvinyl)silane (6b)
Prepared from 5b (817 mg, 5.1 mmol) gave, after partial removal of
the solvent, a solution of 6b (392 mg, 54%) in Et2O (2.62 g) (yield
was determined based on integration of the 1H NMR spectrum).
13C NMR (50 MHz): = 151.2 (0, Colef), 125.5 (–, = CH2), 75.8 (+,
CHOH), 66.7 (–, CH2OH), –0.2, –0.9 [+, Si(CH3)3].
3-[Dimethyl(phenyl)silyl]but-3-ene-1,2-diol (5c)
Prepared from -bromovinyldimethylphenylsilane (2.412 g, 10
mmol) as precursor of 4c and freshly prepared 3a. Flash chromato-
1H NMR (200 MHz, CDCl3): = 0.03 [s, 9 H, Si(CH3)3], 2.35 (dd,
3J = 2.8, 2J = 6.0 Hz, 1 H, CH2O), 2.79 (dd, 3J = 4.4, 2J = 6.0 Hz, 1
H, CH2O), 3.30–3.40 (m, 1 H, CHO; overlaps with OCH2), 5.31 (dd,
4J = 0.8, 2J = 3.0 Hz, 1 H, =CH2), 5.74 (dd, 4J = 1.2, 3J = 3.0 Hz, 1
H, =CH2).
graphy (PE–EtOAc, 20:1
33%) as a colorless oil.
10:1
5:1
1:1) gave 5c (372 mg,
IR (film): 3383 (OH), 1688 (C=C), 1428, 1252 (SiMe2), 1111 (C–
O), 1073, 948, 836, 822, 779, 734, 701 cm–1.
13C NMR (50 MHz): = 148.5 (0, Colef), 124.5 (–, =CH2), 54.2 (+,
CHO), 49.4 (–, CH2O), –1.7 [+, Si(CH3)3].
1H NMR (200 MHz): = 0.42, 0.44 [s each, 3 H, Si(CH3)2], 2.27,
Dimethyl(1-oxiranylvinyl)phenylsilane (6c)
Prepared from 5c (222 mg, 1.0 mmol). Flash chromatography (PE–
EtOAc, 40:1 5:1) gave 6c (147 mg, 72%) as a colorless oil.
2.44 (s each, 1 H, OH), 3.30 (dd, 3J = 8.0, 2J = 11.2 Hz, 1 H, CH2),
4
3.48 (m, 1 H, CH2), 4.37 (m, 1 H, CHOH), 5.60 (dd, J = 1.4,
2J = 2.2 Hz, 1 H, =CH2), 6.0 (dd, 4J = 1.4, 2J = 2.2 Hz, 1 H, =CH2),
7.31–7.55 (m, 5 H, ArH).
IR (film): 1590 (C=C), 1428, 1251 (SiMe2), 1112 (C–O), 938, 924,
835 (SiMe2), 822, 776, 734, 701 cm–1.
13C NMR (50 MHz): = 149.6 (0, Colef), 137.7, 133.8, 129.2, 127.9
(+, CHarom), 133.0 (0, Carom), 127.4 (–, =CH2), 75.7 (+, CHOH), 66.6
(–, CH2OH), –2.3, –2.7 [+, Si(CH3)2].
1H NMR (200 MHz): = 0.44, 0.44 [s each, 3 H, Si(CH3)2], 2.37
3
2
3
2
(dd, J = 2.8, J = 5.6 Hz, 1 H, CH2O), 2.82 (dd, J = 4.4, J = 5.6
2
Hz, 1 H, CH2O), 3.46 (m, 1 H, CHO), 5.51 (d, J = 2.4 Hz, 1
H, =CH2), 5.98 (dd, J = 1.2, J = 2.4 Hz, 1 H, =CH2), 7.33–7.59
4
2
3-(Triphenylsilyl)but-3-ene-1,2-diol (5d)
Prepared from -bromovinyltriphenylsilane (2.375 g, 6.5 mmol) as
precursor of 4d and freshly prepared 3a. Flash chromatography
(PE–EtOAc 20:1 10:1 5:1 1:1) gave 5d (345 mg, 15%) as
colorless crystals; mp 143–144 °C. The analogous reaction with 3b
(3.653 g, 10 mmol) and the same workup gave 5d (151 mg, 10%) as
colorless crystals; mp 143–144 °C.
(m, 5 H, ArH).
13C NMR (50 MHz): = 146.9 (0, Colef), 137.2 (0, Carom), 133.9,
129.2, 127.8 (+, CHarom), 126.6 (–, = CH2), 54.4 (+, CHO), 49.8 (–,
CH2O), –2.9, –3.0 [+, Si(CH3)2].
(1-Oxiranylvinyl)triphenylsilane (6d)
IR (film): 3285 (OH), 1426, 1107, 949, 743, 702 cm–1.
Prepared from 5d (540 mg, 1.56 mmol). Flash chromatography
(PE–EtOAc, 40:1 10:1 5:1 1:1) gave 6d (356 mg, 72%) as
colorless crystals; mp 118–119 °C.
3
1H NMR (200 MHz): = 2.11 (s, 2 H, OH), 3.28 (dd, J = 7.8,
3
2
2J = 11.4 Hz, 1 H, CH2OH), 3.45 (dd, J = 3.2, J = 11.4 Hz, 1 H,
2
4
CH2OH), 4.50 (m, 1 H, CHOH), 5.75 (dd, J = 1.2, J = 1.6 Hz, 1
H, =CH2), 6.37 (dd, J = 1.2, J = 1.6 Hz, 1 H, =CH2), 7.33–7.49
IR (film): 1586 (C=C), 1484, 1427, 1109 (C–O), 943, 847, 704
cm–1.
2
4
(m, 9 H, ArH), 7.55–7.63 (m, 6 H, ArH.).
1H NMR (400 MHz): = 2.41 (dd, 3J = 2.6, 2J = 6.0 Hz, 1 H,
13C NMR (50 MHz): = 146.0 (0, Colef), 133.3 (0, Carom), 136.2,
129.8 128.0 (+, CHarom), 131.8 (–, = CH2), 74.8 (+, CHOH), 66.6
(–, CH2OH).
CH2O), 2.81 (dd, J = 4.2, J = 6.0 Hz, 1 H, CH2O), 3.55 (ddd,
3
2
3
3
2
4J = 1.2, J = 2.8, J = 4.2 Hz, 1 H, CHO), 5.58 (d, J = 2.8 Hz, 1
H, =CH2), 6.23 (dd, 4J = 1.2, 3J = 2.8 Hz, 1 H, =CH2), 7.32–7.48 (m,
9 H, ArH), 7.53–7.61 (m, 6 H, ArH.).
Anal. Calcd for C22H22O2Si (346.5): C, 76.27, H, 6.41; found, C,
76.32, H, 6.44.
13C NMR (100 MHz): = 143.2 (0, Colef), 133.1 (0, Carom), 136.1,
129.8, 127.9 (+, CHarom), 130.2 (–, =CH2), 53.8 (+, CHO), 51.2 (–,
CH2O).
Acceptor-Substituted Vinyloxiranes 6 from the Corresponding
Diols 5 via the Corresponding Monotosylates; General
Procedure
Anal. Calcd for C22H20OSi (328.5): C, 80.46; H, 6.14; found, C,
80.44; H, 6.10.
The monotosylates were prepared according to the literature proce-
dure.12 To the crude tosylate (1.0 equiv), dissolved in MeOH (5 mL/
Synthesis 2002, No. 2, 191–194 ISSN 0039-7881 © Thieme Stuttgart · New York

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E. Schaumann, F. Tries
PAPER
(3) (a) For (2-bromovinyl)oxirane: Beny, J.-P.; Pommelet, J.-
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Acknowledgements
We gratefully acknowledge the financial support of this work by
Fonds der Chemischen Industrie, Frankfurt/Main. Thanks are also
due to Interox Peroxid-Chemie, München, Germany, for a generous
gift of Curox (potassium peroxomonosulfate).
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