Highly Regio- and Enantioselective Monoepoxidation of Conjugated Dienes

Article abstract of DOI:10.1021/jo9721195

This paper describes a highly effective and mild asymmetric monoepoxidation method for conjugated dienes using a fructose-derived chiral ketone 1 as catalyst and Oxone as oxidant. The regioselectivies and enantioslectivies are very high in most cases. For unsymmetrical dienes, the regioselectivity can be regulated by using steric and electronic control. The olefin substrates include trans-disubstituted and trisubstituted olefins that can bear a wide range of functional groups such as hydroxyl groups, TBS ethers, or esters. The enantiomeric excesses for the major monoepoxides range from 89% to 97%. The epoxidation is believed to proceed via a spiro mode.

Full text of DOI:10.1021/jo9721195

2948
J . Org. Chem. 1998, 63, 2948-2953
High ly Regio- a n d En a n tioselective Mon oep oxid a tion of
Con ju ga ted Dien es
Michael Frohn, Molly Dalkiewicz, Yong Tu, Zhi-Xian Wang, and Yian Shi*
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
Received November 19, 1997
This paper describes a highly effective and mild asymmetric monoepoxidation method for conjugated
dienes using a fructose-derived chiral ketone 1 as catalyst and Oxone as oxidant. The regioselec-
tivies and enantioslectivies are very high in most cases. For unsymmetrical dienes, the regiose-
lectivity can be regulated by using steric and electronic control. The olefin substrates include trans-
disubstituted and trisubstituted olefins that can bear a wide range of functional groups such as
hydroxyl groups, TBS ethers, or esters. The enantiomeric excesses for the major monoepoxides
range from 89% to 97%. The epoxidation is believed to proceed via a spiro mode.
Enantiomerically enriched vinyl epoxides are very
oxide could be minimized by controlling the amount of
catalyst to reduce the further epoxidation of the formed
monoepoxide. When 25 mol % of catalyst 1 was used,
94% conversion of the substrate could be achieved at 0
°C with 1.5 h reaction time. The selectivity of monoep-
oxidation over bisepoxidation remained high (22:1). The
high selectivity could be due to the fact that the first
epoxide introduced deactivated the remaining olefin by
the inductive effect. While the selective monoepoxidation
was found to be feasible, the enantiomeric excess for the
monoepoxide was also found to be pleasingly high (97%).
High conversion and selectivity were also obtained for
the symmetric cyclic trisubstituted diene (Table 1, entry
3). It is worth noting that the epoxidations of dienes
under the current reaction conditions were generally
clean as judged by the 1H NMR of the crude reaction
mixtures. The somewhat low isolated yields compared
to the substrate conversions in most cases were due to
the high sensitivity of these vinyl epoxides toward flash
column isolation using silica gel.
useful synthetic intermediates.1 Enantioselective mo-
noepoxidation of conjugated dienes presents an efficient
approach to these epoxides.2,3 Recently, we reported a
highly enantioselective epoxidation method for trans-
disubstituted and trisubstituted olefins using a fructose-
derived ketone 1 as catalyst and Oxone as oxidant.4 As
part of our continuing effort to expand the scope of this
epoxidation, we have been investigating the feasibility
of regio- and enantioselective monoepoxidation of conju-
gated dienes with this catalyst (eq 1). The major issues
that need to be addressed for the diene epoxidation
include regioselectivity (A vs B), selectivity between
monoepoxidation and bisepoxidation (A and B vs C), and
enantioselectivity.5 Herein we wish to report our efforts
in this area.
The good selectivities obtained with the symmetric
dienes encouraged us to further explore the epoxidation
of unsymmetrical dienes. As shown in Table 1, the
results are very encouraging. In many cases, monoep-
oxides were predominately obtained if the amount of
(3) For leading references on enantioselective epoxidations of cis-
olefins of conjugated dienes using chiral (salen)Mn catalysts see: (a)
Lee, N. H.; J acobsen, E. N. Tetrahedron Lett. 1991, 32, 6533-6536.
(b) Chang, S.; Lee, N. H.; J acobsen, E. N. J . Org. Chem. 1993, 58,
6939-6941. (c) Chang, S.; Heid, R. M.; J acobsen, E. N. Tetrahedron
Lett. 1994, 35, 669-672. (d) Zhang, W.; Lee, N. H.; J acobsen, E. N. J .
Am. Chem. Soc. 1994, 116, 425-426. (e) Hamada, T.; Irie, R.; Katsuki,
T. Synlett 1994, 479-481. (f) Mikame, D.; Hamada, T.; Irie, R.; Katsuki,
T. Synlett 1995, 827-828. (g) Hentemann, M. F.; Fuchs, P. L.
Tetrahedron Lett. 1997, 38, 5615-5618.
(4) (a) Tu, Y.; Wang, Z.-X.; Shi, Y. J . Am. Chem. Soc. 1996, 118,
9806-9807. (b) Wang, Z.-X.; Tu, Y.; Frohn, M.; Shi, Y. J . Org. Chem.
1997, 62, 2328-2329. (c) Wang, Z.-X.; Tu, Y.; Frohn, M.; Zhang, J .-R.;
Shi, Y. J . Am. Chem. Soc. 1997, 118, 11224-11235.
(5) For some examples of racemic epoxidations of conjugated dienes
and polyenes with dimethyldioxirane see: (a) Curci, R.; Fiorentino,
M.; Troisi, L.; Edwards, J . O.; Pater, R. H. J . Org. Chem. 1980, 45,
4758-4760. (b) Ebenezer, W.; Pattenden, G. Tetrahedron Lett. 1992,
33, 4053-4056. (c) Curci, R.; Detomaso, A.; Prencipe, T.; Carpenter,
G. B. J . Am. Chem. Soc. 1994, 116, 8112-8115. (d) Curci, R.; Detomaso,
A.; Lattanzio, M. E.; Carpenter, G. B. J . Am. Chem. Soc. 1996, 118,
11089-11092. (e) Murray, R. W.; Singh, M.; Rath, N. Tetrahedron Lett.
1996, 37, 8671-8674. (f) Murray, R. W.; Singh, M.; Rath, N. J . Org.
Chem. 1997, 62, 8794-8799. (g) Yang, D.; Wong, M.-K.; Cheung, K.-
K.; Chan, E. W. C.; Xie, Y. Tetrahedron Lett. 1997, 38, 6865-6868.
Resu lts a n d Discu ssion
Our initial investigation started with a symmetric
conjugated diene, trans,trans-1,4-diphenyl-1,3-butadiene,
as the test substrate (Table 1, entry 1). Subjecting this
diene to the epoxidation conditions gave the monoepoxide
along with the bisepoxide. The formation of the bisep-
* To whom correspondence should be addressed. Tel.: (970) 491-
7424. Fax: (970) 491-1801. E-mail: yian@lamar.colostate.edu.
(1) For leading references on synthetic applications of vinyl epoxides
see: (a) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1173-
1192. (b) Marshall, J . A. Chem. Rev. 1989, 89, 1503-1511. (c) Kolb,
H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94,
2483-2547.
(2) For leading references on enantioselective monoepoxidations of
conjugated dienes directed by hydroxyl groups see: (a) J ohnson, R.
A.; Sharpless, K. B. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
VCH: New York, 1993; Chapter 4.1. (b) Katsuki, T.; Martin, V. S. Org.
React. 1996, 48, 1-299.
S0022-3263(97)02119-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 04/17/1998

Monoepoxidation of Conjugated Dienes
J . Org. Chem., Vol. 63, No. 9, 1998 2949
Ta ble 1. Asym m etr ic Ep oxid a tion of Rep r esen ta tive Dien es by Keton e 1 a n d en t-1a
a
All reactions were carried out at 0 °C with diene (1 equiv), ketone (0.2-0.3 equiv), Oxone (1.12-1.38 equiv), and K2CO3 (5.0-6.2
equiv) in CH3CN-DMM-0.05 M Na2B4O7‚10H2O of aqueous EDTA (4 × 10-4 M) solution (1:2:2, v/v). Oxone was added over 1.5 h unless
otherwise stated, and the reactions were stopped immediately. The conversions were determined by the 1H NMR of the crude reaction
b
mixtures. c The ratios were determined by the 1H NMR of the crude reaction mixtures. For symmetric dienes the ratio refers to the
monoepoxide/bisepoxide ratio (the precise stereochemistry of the bisepoxides has not been determined yet). For unsymmetric dienes it
refers to the ratio of the two monoepoxides. For entries 6-12 and 15-17, the other monoepoxide regioisomers were barely detectable by
1H NMR if there was any. The epoxides were purified by flash chromatography and gave satisfactory spectroscopic characterization.
d
The number in parentheses refers to the yield of the minor epoxide. It should be noted that the vinyl epoxides are not very stable, and
g
portions are lost during the column isolation. e 0.20 equiv of catalyst used. f 0.25 equiv of catalyst used. 0.30 equiv of catalyst used.
h
i
Oxone was added over 4 h, and the reaction was stopped immediately. Trace amounts of bisepoxide were detected in the crude reaction
mixtures by 1H NMR. The epoxide distal to the SiMe3 group was isolated, and the epoxide proximal to the SiMe3 group was detected in
j
the crude reaction mixtures by 1H NMR but decomposed during column isolation. Enantioselectivities were determined by chiral HPLC
k
l
(Chiralcel OD). The TBS ether was converted to the corresponding alcohol with TBAF, and enantioselectivities were determined by
m
chiral GC (Chiraldex γ-TA column). The number in parentheses refers to the ee of the minor epoxide. Enantioselectivities were determined
n
by chiral HPLC (Chiralcel OB). The TBS ether was converted to the corresponding alcohol with TBAF, and enantioselectivities were
determined by chiral HPLC (Chiralcel OB). o Enantioselectivities were determined by chiral shift NMR with Eu(hfc)3. The absolute
p
configurations of the epoxides for entries 1 and 10 were determined by comparing to the authentic samples prepared by different routes,
q
and the configurations for the remaining epoxides were tentatively assumed by analogy based on the spiro reaction mode. The number
refers to the ee of the epoxide distal to the SiMe3 group.

2950 J . Org. Chem., Vol. 63, No. 9, 1998
Frohn et al.
catalyst was properly controlled. The enantiomeric
excesses for the formed monoepoxides were also high.
Some of the reaction features are highlighted as follows.
If both olefins were disubstituted, regioselectivity (A vs
B) could be regulated by using steric and electronic
control. Introducing an electron-withdrawing group
deactivated the adjacent olefin, resulting in the formation
of the distal epoxide as the major product. For example,
a 7:1 ratio was obtained for the epoxidation of ethyl
sorbate (Table 1, entry 4). The allylic electron-withdraw-
ing groups such as TBS ether, which was not conjugated
to the olefin, could also substantially deactivate the
proximal olefin by the inductive effect (Table 1, entry 5).
The regioselectivity could be further enhanced by intro-
ducing steric hindrance next to one olefin. Such an
example is illustrated in entry 6, in which only one
monoepoxide was detected. Introducing an additional
alkyl group to the olefin could also further regulate the
regioselectivity. For example, entries 7 and 8 show that
the epoxidation was highly selective for the trisubstituted
olefin distal to the hydroxyl group and the TBS ether
group. The regioselectivity shown in entry 7 is comple-
mentary to the Sharpless asymmetric epoxidation, which
selectively epoxidizes the olefin proximal to the hydroxyl
group. In the case of diene esters (Table 1, entries 9-12),
it is rather interesting to note that the epoxidation
regioselectively occurred on the distal olefin regardless
of whether the alkyl group was introduced to the distal
or to the proximal or both olefins. A possible reason for
the observed selectivity could be that the introduced alkyl
group(s) prevented full conjugation of the diene due to
the A1,3 strain, and therefore the distal olefin to the ester
group was less electron deficient compared to the proxi-
mal olefin.
F igu r e 1. Possible main competing spiro and planar transi-
tion states for the epoxidation catalyzed by ketone 1.
ample, the silyl group could be further utilized as a
controlling element for regioselective opening of the
epoxide.
The epoxidation of isolated trans-disubstituted and
trisubstituted olefins with catalyst 1 has been shown to
proceed mainly via spiro transition state A (Figure
1).4a,c,10 The main competing transition state is believed
to be planar transition state B (Figure 1).4c The nature
of the substitutents on the olefins have noticeable effects
on the competition between the two transition states,
consequently affecting the enantioselectivities of the
epoxidation.4c It is believed that the spiro transition state
is generally favored due to the stabilizing interaction of
an oxygen lone pair of the dioxirane with the π* orbital
of the alkene.10c,e The transition states C and D are
anticipated for the two main competing transition states
for the epoxidation of the dienes. As shown in Table 1,
the enantioselectivities of the epoxidation of the dienes
are high regardless of whether the epoxidized olefin is
disubstituted or trisubstituted. This observation shows
that the spiro transition state is further favored when a
conjugated diene is used as substrate. The increased
favorability of the spiro transition state is presumably
due to the fact that a conjugated diene has a lower LUMO
than an isolated olefin leading to a greater stabilizing
interaction between an oxygen lone pair of the dioxirane
with the LUMO of the alkene.
The epoxidation with dioxiranes is more sensitive to
the steric environment around olefins than other epoxi-
dizing reagents such as m-CPBA. The reduced reactivity
of vinylsilanes for the epoxidation with dioxiranes has
been observed due to the steric hindrance of the silyl
groups.6 To further probe the possibility of using the
silicon group as a potential controlling element for
regioselectivity, a variety of silyl-substituted dienes were
prepared and studied (Table 1, entries 13-17).7 Like the
previously discussed dienes, a mixture of two epoxide
regioisomers were obtained when both olefins were
disubstituted (Table 1, entry 13). However, when the
olefin distal to the trimethylsilyl group was trisubsti-
tuted, the epoxidation again predominately occurred on
the distal olefin with high enantioselectivity.8 The enan-
tiomerically enriched silyl-substituted vinyl epoxides
should be versatile synthetic intermediates.9 For ex-
As discussed above, the spiro transition state is ex-
pected for the epoxidation of dienes. The stereochemistry
of the epoxides in Table 1 is assigned on the basis of this
model. To further validate the assignment, the absolute
configurations of two representative examples (Table 1,
entries 1 and 10) were further defined either by convert-
ing the vinyl epoxide to an epoxide with known config-
(6) For examples of the epoxidation of vinylsilanes with dimethyl-
dioxirane see: (a) Branan, B. M.; Wang, X.; J ankowski, P.; Wicha, J .;
Paquette, L. A. J . Org. Chem. 1994, 59, 6874-6876. (b) Adam, W.;
Prechtl, F.; Richter, M. J .; Smerz, A. K. Tetrahedron Lett. 1995, 36,
4991-4994.
(7) The silyl-substituted dienes were readily prepared on the basis
of the reported method: Ni, Z. J .; Yang, P. F.; Ng, D. K. P.; Tzeng, Y.
L.; Luh, T. Y. J . Am. Chem. Soc. 1990, 112, 9356-9364.
(8) In comparison, the diene of entry 17 was epoxidized with
m-CPBA. The distal epoxide was favored by a 2.5:1 ratio.
(9) For leading references on the synthesis of silyl-substituted vinyl
epoxides by other methods, see: (a) Chou, W.-N.; White, J . B.
Tetrahedron Lett. 1991, 32, 157-160. (b) Chou, W.-N.; White, J . B.;
Smith, W. B. J . Am. Chem. Soc. 1992, 114, 4658-4667. (c) Zhou, Z.-
L.; Huang, Y.-Z.; Shi, L.-L. Tetrahedron Lett. 1992, 33, 5827-5830.
(d) Zhou, Y.-G.; Li, A.-H.; Hou, X- L.; Dai, L.-X. Chem. Commun. 1996,
1353-1354.
(10) For leading references on the transition states of the dioxirane-
mediated epoxidation see: (a) Baumstark, A. L.; McCloskey, C. J .
Tetrahedron Lett. 1987, 28, 3311-3314. (b) Baumstark, A. L.; Vasquez,
P. C. J . Org. Chem. 1988, 53, 3437-3439. (c) Bach, R. D.; Andres, J .
L.; Owensby, A. L.; Schlegel, H. B.; McDouall, J . J . W. J . Am. Chem.
Soc. 1992, 114, 7207-7217. (d) Yang, D.; Wang, X.-C.; Wong, M.-K.;
Yip, Y.-C.; Tang, M.-W. J . Am. Chem. Soc. 1996, 118, 11311-11312.
(e) Houk, K. N.; Liu, J .; DeMello, N. C.; Condroski, K. R. J . Am. Chem.
Soc. 1997, 119, 10147-10152. (f) J enson, C.; Liu, J .; Houk, K. N.;
J orgensen, W. L. J . Am. Chem. Soc. 1997, 119, 12982-12983.

Monoepoxidation of Conjugated Dienes
J . Org. Chem., Vol. 63, No. 9, 1998 2951
uration (eq 2)11 or by preparing an authentic sample from
an epoxy alcohol with known configuration following a
reported sequence for the exact compound (eq 3).12,13 In
our case, it was found that the route presented in eq 2
was not a very efficient sequence, particularly for the
NaBH4 reduction. As a result, the overall yield for the
transformation was extremely low. Nevertheless, a small
amount of the hydroxy epoxide was obtained, which was
sufficient for us to compare with authentic sample by
chiral HPLC. The results in both cases support the
initial assignment based on the spiro mode.
mL) were added separately via syringe pump over 1.5 h. The
reaction was immediately quenched by the addition of hexanes
(15 mL). The aqueous layer was extracted with hexanes (3 ×
25 mL), washed with brine (50 mL), dried (Na2SO4), filtered,
concentrated, and purified by flash chromatography (the silica
gel was buffered with 1% Et3N in hexane; 1% Et3N in 3:1 CH2-
Cl2/hexane was used as the eluent) to afford (R,R)-2-phenyl-
3-(trans-2-phenylvinyl)oxirane as a white solid (0.171 g, 77%
yield, 97% ee) (Table 1, entry 1).
(R,R)-2-P h en yl-3-(tr a n s-2-p h en ylvin yl)oxir a n e (Ta ble
1, en tr y 1): white solid; [R]20 ) +252.2° (c 0.24, CHCl3); IR
D
(NaCl): 3027, 1953, 1755, 1598, 1489, 1448, 1263 cm-1
;
1H
NMR (300 MHz, CDCl3) δ 7.4-7.2 (m, 10H), 6.81 (d, J ) 15.9
Hz, 1H), 6.09 (dd, J ) 15.9, 7.5 Hz, 1H), 3.89 (d, J ) 2.1 Hz,
1H), 3.53 (dd, J ) 7.5, 2.1 Hz, 1H); 13C NMR (75 MHz, CDCl3)
δ 137.0, 136.0, 134.4, 128.7, 128.5, 128.2, 128.1, 126.5, 126.2,
125.5, 63.12, 60.70. Anal. Calcd for C16H14O: C, 86.45; H,
6.34. Found: C, 86.43; H, 6.55.
(R,R)-1-Cycloh exen ylcycloh exen e Oxid e (Ta ble 1, en -
tr y 3). The diene substrate was prepared by pinacolic coupling
of cyclohexanone14 and dehydration of the resulting diol15 to
give a white solid (36% overall yield): IR (NaCl) 3037, 2924,
1
2855, 1439 cm-1; H NMR (300 MHz, CDCl3) δ 5.78 (s, 2H),
2.20-2.05 (m, 8H), 1.70-1.50 (m, 8H); 13C NMR (75 MHz,
CDCl3) δ 136.8, 121.4, 25.85, 25.50, 23.13, 22.51.
Ep oxid e: colorless oil; [R]20 ) +6.67° (c 0.29, CHCl3); IR
D
(NaCl) 2932, 2857, 1439, 1344, 1220, 1136, 980, 920, 834 cm-1
;
1H NMR (300 MHz, CDCl3) δ 5.73 (m, 1H), 3.04 (dd, J ) 3.6,
1.5 Hz, 1H), 2.1-1.1 (m, 16H); 13C NMR (75 MHz, CDCl3) δ
138.3, 122.6, 61.81, 58.81, 27.39, 24.93, 24.80, 24.55, 22.62,
In summary, we report a highly effective and mild
epoxidation of conjugated dienes using a fructose-derived
chiral ketone 1 as catalyst and Oxone as oxidant. The
regioselectivities and enantioslectivities are very high in
most cases. As a result, a variety of synthetically useful
vinyl epoxides can be readily produced in optically
enriched form. The current method is complementary
to the selective epoxidation of conjugated dienes catalyzed
by chiral (salen)Mn complexes, in which the cis-olefins
are preferentially epoxidized.3
22.33, 20.09, 19.91; HRMS calcd for
179.1437, found 179.1437.
C
12H19O (M+ + 1)
(R,R)-2-[tr a n s-2-(E t h oxyca r b on yl)vin yl]-3-m et h ylox-
ir a n e (Ta ble 1, en tr y 4): colorless oil; [R]20 ) +12.64° (c
D
0.48, CHCl3); IR (NaCl) 2984, 2933, 1721, 1655, 1446, 1370,
1340, 1188, 1144 cm-1; 1H NMR (300 MHz, CDCl3) δ 6.67 (dd,
J ) 15.6, 7.2 Hz, 1H), 6.13 (d, J ) 15.6 Hz, 1H), 4.20 (q, J )
7.2 Hz, 2H), 3.18 (dd, J ) 7.2, 1.8 Hz, 1H), 2.98 (qd, J ) 5.1,
1.8 Hz, 1H), 1.39 (d, J ) 5.1 Hz, 3H), 1.29 (t, J ) 7.2 Hz, 3H);
13C NMR (75 MHz, CDCl3) δ 165.7, 144.6, 123.7, 60.50, 57.37,
57.21, 17.50, 14.19; HRMS calcd for C8H13O3 (M+ + 1)
157.0864, found 157.0865.
Exp er im en ta l Section
Gen er a l Meth od s. Oxone was purchased from Aldrich (it
has been found that the oxidation activity of the purchased
Oxone occasionally varies with different batches). All glass-
ware used for the epoxidation was carefully washed to be free
of any trace metals, which catalyze the decomposition of
Oxone. The 300 MHz 1H NMR and 75.5 MHz 13C NMR spectra
were measured on a Bruker ACE-300 spectrometer in CDCl3.
Proton chemical shifts (δ) are given relative to internal TMS
(0.00 ppm), and carbon chemical shifts are given relative to
CDCl3 (77.00 ppm). Infrared spectra were recorded on a
Perkin-Elmer 1600 Series FTIR spectrometer. High-resolution
mass spectra were performed by the mass spectrometry facility
of Colorado State University. Elemental analyses were per-
formed by M-H-W Laboratories, Phoenix, AZ. Optical rota-
tions were measured on an Autopol III automatic polarimeter
in a 10 cm cell. Silica gel 60 of E-Merck Co. was employed for
all flash chromatography.
Gen er a l Ep oxid a tion P r oced u r e. To a 150 mL three-
necked flask were added buffer (0.05 M Na2B2O4‚10 H2O in 4
× 10-4 M EDTA, 10 mL), dimethoxymethane/acetonitrile (2:
1, 15 mL), trans,trans-1,4-diphenyl-1,3-butadiene (0.206 g, 1
mmol), tetrabutylammonium hydrogen sulfate (0.015 g, 0.04
mmol), and ketone 1 (0.065 g, 0.25 mmol). The reaction
mixture was cooled to 0 °C with an ice bath. A solution of
Oxone (0.69 g, 1.13 mmol) in aqueous EDTA (4 × 10-4 M, 6.0
mL) and a solution of K2CO3 (0.69 g, 4.99 mmol) in water (6.0
(R,R)-2-[tr a n s-2-[(ter t-Bu tyld im eth ylsiloxy)m eth yl]vi-
n yl]-3-m eth yloxir a n e (Ta ble 1, en tr y 5). The diene sub-
strate was prepared from (E,E)-2,4-hexadien-1-ol and tert-
butyldimethylsilyl chloride16 to give a colorless oil (99%
yield): IR (NaCl) 3020, 2954, 2931, 2856, 1467, 1379, 1255,
1
1111 cm-1; H NMR (300 MHz, CDCl3) δ 6.25-6.00 (m, 2H),
5.75-5.55 (m, 2H), 4.19 (d, J ) 4.5 Hz, 2H), 1.75 (d, J ) 6.6
Hz, 3H), 0.91 (s, 9H), 0.07 (s, 6H); 13C NMR (75 MHz, CDCl3)
δ 131.0, 130.3, 129.9, 129.0, 63.70, 26.00, 18.46, 18.11, -5.13.
Ep oxid e: colorless oil; [R]20 ) +28.6° (c 0.71, EtOH); IR
D
(NaCl) 2956, 2931, 2857, 1620, 1468, 1381, 1255, 1125 cm-1
;
1H NMR (300 MHz, CDCl3) δ 5.98 (dt, J ) 15.3, 4.5 Hz, 1H),
5.45 (ddtd, J ) 15.3, 8.1, 1.8, 0.9 Hz, 1H), 4.19 (dd, J ) 4.5,
1.8 Hz, 2H), 3.09 (dd, J ) 8.1, 2.1 Hz, 1H), 2.91 (qdd, J ) 5.1,
2.1, 0.9 Hz, 1H), 1.34 (d, J ) 5.1 Hz, 3H), 0.91, (s, 9H), 0.07 (s,
6H); 13C NMR (75 MHz, CDCl3) δ 134.5, 127.2, 62.87, 59.08.
56.40, 25.89, 18.36, 17.54, -5.41. Anal. Calcd for C12H24O2-
Si: C, 63.10; H, 10.59. Found: C, 62.96; H, 10.30..
(R,R)-2-[(ter t-Bu tyld im eth ylsiloxy)m eth yl]-3-(tr a n s-2-
m eth ylvin yl)oxir a n e (Ta ble 1, en tr y 5): colorless oil; [R]20
D
) +17.7° (c 0.45, EtOH); IR (NaCl) 3051, 2955, 2928, 2857,
1464, 1382, 1260, 1109 cm-1 1H NMR (300 MHz, CDCl3) δ
;
5.94 (dq, J ) 15.3, 6.6 Hz, 1H), 5.22 (ddq, J ) 15.3, 8.1, 1.8
Hz, 1H), 3.84 (dd, J ) 12.3, 3.6 Hz, 1H), 3.70 (dd, J ) 12.3,
4.5 Hz, 1H), 3.24 (dd, J ) 8.1, 2.4 Hz, 1H), 3.02-2.97 (m, 1H),
1.74 (dd, J ) 6.6, 1.8 Hz, 3H), 0.90 (s, 9H), 0.08 (s, 3H), 0.072
(11) Gao, Y.; Hanson, R. M.; Klunder, J . M.; Ko, S. Y.; Masamune,
H.; Sharpless, K. B. J . Am. Chem. Soc. 1987, 109, 5765-5780.
(12) Rossiter, B. E.; Katsuki, T.; Sharpless, K. B. J . Am. Chem. Soc.
1981, 103, 464-465.
(13) (a) Oshima, M.; Yamazaki, H.; Shimizu, I.; Nisar, M.; Tsuji, J .
J . Am. Chem. Soc. 1989, 111, 6280-6287. (b) Shimizu, I.; Hayashi,
K.; Ide, N.; Oshima, M. Tetrahedron 1991, 47, 2991-2998.
(14) Corey, E. J .; Danheiser, R. L.; Chandrasekaran, S. J . Org.
Chem. 1976, 41, 260-265.
(15) Saltiel, J .; Marchand, G. R. J . Am. Chem. Soc. 1991, 113, 2702-
2708.
(16) Corey, E. J .; Venkateswarlu, A. J . Am. Chem. Soc. 1972, 94,
6190-6191.

2952 J . Org. Chem., Vol. 63, No. 9, 1998
Frohn et al.
(s, 3H); 13C NMR (75 MHz, CDCl3) δ 131.8, 128.2, 63.23, 60.17,
56.16, 25.88, 18.30, 17.86, -5.31. Anal. Calcd for C12H24O2-
Si: C, 63.10; H, 10.59. Found: C, 63.02; H, 10.46.
Ep oxid e: colorless oil; [R]20 ) -58.8° (c 0.39, CHCl3); IR
D
(NaCl) 2961, 2932, 2872, 1722, 1655, 1464, 1367, 1305, 1265,
1165, 1041, 980 cm-1; 1H NMR (300 MHz, CDCl3) δ 6.96 (d, J
) 15.6 Hz, 1H), 6.00 (d, J ) 15.6 Hz, 1H), 4.19 (q, J ) 7.2 Hz,
2H), 2.74 (t, J ) 6.3 Hz, 1H), 1.8-1.32 (m, 13H), 1.0-0.9 (m,
6H); 13C NMR (75 MHz, CDCl3) δ 166.4, 148.5, 120.9, 67.11,
61.90, 60.44, 32.02, 28.55, 28.17, 22.50, 18.75, 14.28, 14.21,
13.93. Anal. Calcd for C14H24O3: C, 69.96; H, 10.07. Found:
C, 70.17; H, 9.97.
(R,R)-2-[tr a n s-2-(1-Meth oxy-1-m eth yleth yl)vin yl]-3-m e-
th yloxir a n e (Ta ble 1, en tr y 6). The diene substrate was
prepared from ethyl sorbate by treatment with MeLi (2 equiv)
and then NaH/MeI17 to give a colorless oil (39% yield): IR
(NaCl) 3017, 2922, 2856, 1454, 1373, 1241, 1161, 1073, 992
cm-1; 1H NMR (300 MHz, CDCl3) δ 6.15-6.00 (m, 2H), 5.76-
5.64 (m, 1H), 5.57-5.45 (m, 1H), 3.14 (s, 3H), 1.76 (d, J ) 6.6,
0.6 Hz, 3H), 1.27 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 136.0,
131.1, 129.7, 129.2, 74.80, 50.27, 25.82, 18.00.
(R,R)-2-[tr a n s-2-(Eth oxyca r bon yl)vin yl]-3-eth yl-2-m e-
th yloxir a n e (Ta ble 1, en tr y 10). The diene substrate was
prepared by Wittig reaction of (E)-2-methyl-2-pentenal and
(carbethoxymethylene)triphenylphosphorane to give a colorless
oil (99% yield): IR (NaCl) 3066, 2971, 2935, 2874, 1713, 1625,
Ep oxid e: colorless oil; [R]20 ) +22.0° (c 0.20, CHCl3); IR
D
(NaCl) δ 2977, 2934, 2825, 1455, 1378, 1246, 1169, 1075 cm-1
;
1H NMR (300 MHz, CDCl3) δ 5.89 (d, J ) 15.9 Hz, 1H), 5.30
(dd, J ) 15.9, 8.1 Hz, 1H), 3.16 (s, 3H), 3.08 (dd, J ) 8.1, 1.8
Hz, 1H), 2.93 (dq, J ) 5.1, 1.8 Hz, 1H), 1.35 (d, J ) 5.1 Hz,
3H), 1.27 (s, 6H); 13C NMR (75 MHz, CDCl3) δ 140.7, 127.4,
74.51, 59.24, 56.39, 50.43, 25.61, 17.51; HRMS calcd for
C9H17O2 (M+ + 1) 157.1228, found 157.1225.
1294, 1263, 1170 cm-1; H NMR (300 MHz, CDCl3) δ 7.33 (d,
1
J ) 15.6 Hz, 1H), 5.89 (t, J ) 7.2 Hz, 1H), 5.79 (d, J ) 15.6
Hz, 1H), 4.21 (q, J ) 7.2 Hz, 2H), 2.21 (quintet, J ) 7.2 Hz,
2H), 1.77 (s, 3H), 1.30 (t, J ) 7.2 Hz, 3H), 1.03 (t, J ) 7.2 Hz,
3H); 13C NMR (75 MHz, CDCl3) δ 167.5, 149.6, 143.6, 132.2,
115.5, 60.08, 22.05, 14.31, 13.45, 11.93.
(R,R)-3-Eth yl-2-[tr a n s-2-(h yd r oxym eth yl)vin yl]-2-m e-
th yloxir a n e (Ta ble 1, en tr y 7). The diene substrate was
prepared by DIBAL reduction of (E,E)-ethyl-4-methyl-2,4-
heptadienoate to give a colorless oil (81% yield): IR (NaCl)
3332, 3027, 2961, 2925, 2867, 1646, 1450, 1392, 1305, 1087,
Ep oxid e:13a colorless oil; [R]20 ) -36.8° (c 0.65, CHCl3).
D
(R,R)-2-[(E)-2-(Eth oxyca r bon yl)-2-m eth ylvin yl]-3-p r o-
p yloxir a n e (Ta ble 1, en tr y 11). The diene substrate was
prepared by Wittig reaction of 2-(carbethoxyethyl)triphe-
nylphosphonium bromide with trans-2-hexenal to produce a
colorless oil (59% yield): IR (NaCl) 2960, 2931, 2872, 1705,
1641, 1610, 1464, 1389, 1367, 1291, 1238, 1167, 1103, 1038,
971, 749 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.16 (d, J ) 11.1
Hz, 1H), 6.34 (dd, J ) 15.0, 11.1 Hz, 1H), 6.06 (dt, J ) 15.0,
7.2 Hz, 1H), 4.20 (q, J ) 7.2 Hz, 2H), 2.18 (dt, J ) 7.2, 6.6 Hz,
2H), 1.93 (s, 3H), 1.55-1.40 (m, 2H), 1.30 (t, J ) 7.2 Hz, 3H),
0.93 (t, J ) 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 168.5,
142.7, 138.4, 126.0, 124.9, 60.35, 35.30, 22.17, 14.33, 13.67,
12.53.
1
963 cm-1; H NMR (300 MHz, CDCl3) δ 6.24 (d, J ) 15.6 Hz,
1H), 5.71 (dt, J ) 15.6, 6.3 Hz, 1H), 5.49 (t, J ) 7.4 Hz, 1H),
4.18 (d, J ) 6.3 Hz, 2H), 2.14 (quintet, J ) 7.4 Hz, 2H), 1.78
(br s, 1H), 1.75 (s, 3H), 0.99 (t, J ) 7.4 Hz, 3H); 13C NMR (75
MHz, CDCl3) δ 136.7, 135.1, 132.3, 125.1, 63.87, 21.45, 13.90,
12.17.
Ep oxid e: colorless oil; [R]20 ) -8.14° (c 0.52, CHCl3); IR
D
(NaCl) 3416, 2970, 2934, 2875, 1670, 1460, 1385, 1276, 1222,
1
1096, 1071, 1013, 971, 880 cm-1; H NMR (300 MHz, CDCl3)
δ 5.88 (dt, J ) 15.9, 5.1 Hz, 1H), 5.53 (d, J ) 15.9 Hz, 1H),
4.12 (t, J ) 5.1 Hz, 2H), 2.76 (t, J ) 6.3 Hz, 1H), 2.29 (br s,
1H), 1.65-1.5 (m, 2H), 1.37 (s, 3H), 1.01 (t, J ) 7.5 Hz); 13C
NMR (75 MHz, CDCl3) δ 133.9, 130.7, 66.61, 62.65, 59.07,
21.89, 15.24, 10.32; HRMS calcd for C8H15O2 (M+ + 1)
143.1073, found 143.1073.
Ep oxid e: colorless oil; [R]20 ) +40.6° (c 1.61, CHCl3); IR
D
(NaCl) 2962, 2934, 2874, 1714, 1654, 1465, 1368, 1311, 1253,
1236, 1160, 1103, 1033, 976, 914, 858, 747 cm-1; 1H NMR (300
MHz, CDCl3) δ 6.30 (d, J ) 8.4 Hz, 1H), 4.20 (q, J ) 7.2 Hz,
2H), 3.38 (dd, J ) 8.4, 1.8 Hz, 1H), 2.96 (td, J ) 5.7, 1.8 Hz,
1H), 2.00 (s, 3H), 1.65-1.40 (m, 4H), 1.29 (t, J ) 7.2 Hz, 3H),
0.98 (t, J ) 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 166.9,
137.9, 132.0, 60.72, 59.99, 54.43, 33.91, 19.19, 14.17, 13.84,
(R,R)-3-Eth yl-2-[tr a n s-2-[(ter t-bu tyld im eth ylsiloxy)m -
eth yl]vin yl]-2-m eth yloxir a n e (Ta ble 1, en tr y 8). The
diene substrate was prepared from (E,E)-4-methyl-2,4-hepta-
dien-1-ol and tert-butyldimethylsilyl chloride16 to give a color-
less oil (82% yield): IR (NaCl) 3034, 2954, 2925, 2852, 1646,
12.75. Anal. Calcd for C
C, 66.77; H, 8.96.
11H18O3: C, 66.64; H, 9.15. Found:
(R,R)-2-[(E)-2-(Eth oxycar bon yl)-2-m eth ylvin yl]-3-eth yl-
2-m eth yloxir a n e (Ta ble 1, en tr y 12). The diene was
prepared by Wittig reaction of 2-(carbethoxyethyl)triphe-
nylphosphonium bromide with trans-2-methyl-2-pentenal to
give a colorless oil (91% yield): IR (NaCl) 2966, 2933, 2872,
1703, 1626, 1456, 1364, 1246, 1108, 1031, 1010, 923, 872, 749,
667 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.12 (s, 1H), 5.62 (t, J
) 7.2 Hz, 1H), 4.19 (q, J ) 6.9 Hz, 2H), 2.15 (quintet, J ) 6.9
Hz, 2H), 2.01 (s, 3H), 1.84 (s, 3H), 1.30 (t, J ) 6.9 Hz, 3H),
1.02 (t, J ) 6.9 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 169.0,
142.8, 138.2, 131.4, 124.9, 60.40, 21.63, 16.03, 14.26, 13.89,
13.66.
1465, 1377, 1297, 1254, 1123, 1072, 963, 840, 724 cm-1 1H
;
NMR (300 MHz, CDCl3) δ 6.23 (d, J ) 15.6 Hz, 1H), 5.63 (dt,
J ) 15.6, 5.7 Hz, 1H), 5.46 (t, J ) 6.9 Hz, 1H), 4.25 (d, J ) 5.7
Hz, 2H), 2.14 (qd, J ) 7.5, 6.9 Hz, 2H), 1.75 (s, 3H), 0.99 (t, J
) 7.5 Hz, 3H), 0.92 (s, 9H), 0.09 (s, 6H); 13C NMR (75 MHz,
CDCl3) δ 135.0, 134.2, 132.5, 125.7, 64.17, 25.98, 21.45, 18.42,
14.01, 12.24, -5.133.
Ep oxid e: colorless oil; [R]20 ) -9.2° (c 1.57, CHCl3); IR
D
(NaCl) 2959, 2935, 2857, 1456, 1386, 1252, 1118, 1071, 961,
835, 772 cm-1; 1H NMR (300 MHz, CDCl3) δ 5.83 (dt, J ) 15.6,
4.5 Hz, 1H), 5.54 (dt, J ) 15.6, 1.8 Hz, 1H), 4.19 (dd, J ) 4.5,
1.8 Hz, 2H), 2.77 (t, J ) 6.0 Hz, 1H), 1.61 (m, 2H), 1.39 (s,
3H), 1.04 (t, J ) 8.4 Hz, 3H), 0.91 (s, 9H), 0.07 (s, 6H); 13C
NMR (75 MHz, CDCl3) δ 132.7, 130.8, 66.64, 63.21, 59.10,
25.97, 22.06, 18.43, 15.48, 10.45, -5.21. Anal. Calcd for
Ep oxid e: colorless oil; [R]20D ) -90.7° (c 1.63, CHCl3) [lit.13b
[R]23 ) +78.3° (c 1.15, CHCl3) for (S,S)].
D
(R ,R )-2-[t r a n s-2-(Tr im e t h ylsilyl)vin yl]-3-p h e n ylox-
ir a n e (Ta ble 1, en tr y 13). The diene substrate was prepared
by Ni-catalyzed coupling of an allylic dithioacetal with [(tri-
methylsilyl)methyl]magnesium chloride7 to give a white solid
(88% yield): mp 38-40 °C; IR (NaCl) 3077, 3017, 2957, 2897,
1572, 1445, 1243, 1010, 868, 839, 734, 689 cm-1; 1H NMR (300
MHz, CDCl3) δ 7.43 (d, J ) 8.7 Hz, 2H), 7.35 (t, J ) 7.2 Hz,
2H), 7.26 (m, 1H), 6.71 (dd, J ) 17.4, 10.2 Hz, 1H), 6.82 (dd,
J ) 15.3, 10.2 Hz, 1H), 6.61 (d, J ) 15.3 Hz, 1H), 6.01 (d, J )
17.4 Hz, 1H), 0.15 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 144.1,
137.2, 135.0, 132.9, 131.6, 128.6, 127.6, 126.5, -1.28.
C
14H28O2Si: C, 65.57; H, 11.01. Found: C, 65.70; H, 10.84.
(2S,3R)-3-Bu t yl-2-[tr a n s-2-(et h oxyca r b on yl)vin yl]-2-
p r op yloxir a n e (Ta ble 1, en tr y 9). The diene substrate was
prepared by treatment of (Z)-2-propyl-2-heptenal with NaH
and triethyl phophonoacetate to produce a colorless oil (85%
yield): IR (NaCl) 2959, 2931, 2871, 1714, 1624, 1463, 1367,
1
1301, 1258, 1168 cm-1; H NMR (300 MHz, CDCl3) δ 7.24 (d,
J ) 15.9 Hz, 1H), 5.88 (t, J ) 7.5 Hz, 1H), 5.79 (d, J ) 15.9
Hz, 1H), 4.20 (q, J ) 7.2 Hz, 2H), 2.25-2.15 (m, 4H), 1.48-
1.27 (m, 9H), 0.96-0.88 (m, 6H); 13C NMR (75 MHz, CDCl3) δ
167.7, 149.0, 142.6, 137.2, 115.1, 60.08, 31.37, 28.60, 28.46,
22.42, 21.92, 14.31, 14.16, 13.88.
Ep oxid e: colorless oil; [R]20 ) +137.4° (c 0.915, CHCl3);
D
IR (NaCl) 3063, 3034, 2953, 2912, 1615, 1494, 1453, 1251, 989,
850, 757, 699 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.33 (m, 5H),
6.23 (d, J ) 18.6 Hz 1H), 5.87 (dd, J ) 18.6, 7.2 Hz, 1H), 3.81
(d, J ) 2.1 Hz, 1H), 3.35 (dd, J ) 7.2, 2.1 Hz, 1H), 0.11 (s,
9H); 13C NMR (75 MHz, CDCl3) δ 142.0, 137.1, 136.4, 128.4,
(17) Stoochnoff, B. A.; Benoiton, N. L. Tetrahedron Lett. 1973, 21-
24.

Monoepoxidation of Conjugated Dienes
J . Org. Chem., Vol. 63, No. 9, 1998 2953
128.1, 125.4, 64.49, 60.28, -1.55. Anal. Calcd for C13H18OSi:
C, 71.50; H, 8.31. Found: C, 71.41; H, 8.27.
(quintet, J ) 7.5 Hz, 2H), 1.75 (s, 3H), 1.01 (t, J ) 7.5, 3H),
0.01 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 148.7, 136.0, 134.71,
125.4, 21.68, 13.96, 11.67, 0.71.
(R,R)-2-Meth yl-2-[tr a n s-2-(tr im eth ylsilyl)vin yl]-3-p h e-
n yloxir a n e (Ta ble 1, en tr y 14). The diene substrate was
prepared by Ni-catalyzed coupling of an allylic dithioacetal
with [(trimethylsilyl)methyl]magnesium chloride7 to give a
colorless oil (53% yield): IR (NaCl) 3077, 3056, 3019, 2954,
2889, 1600, 1579, 1491, 1444, 1257, 983, 871, 836, 730, 697
cm-1; 1H NMR (300 MHz, CDCl3) δ 7.33 (m, 5H), 6.75 (d, J )
18.9 Hz, 1H), 6.60 (s, 1H), 5.99 (d, J ) 18.9 Hz, 1H), 2.03 (s,
3H), 0.15 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 148.8, 137.9,
137.1, 132.3, 129.2, 128.5, 128.1, 126.6, 13.37, -1.12.
Ep oxid e: colorless oil; [R]20D ) +63.6° (c 0.905, CHCl3); IR
Ep oxid e: colorless oil; [R]20 ) -16.1° (c 0.99, CHCl3); IR
D
(NaCl) 2960, 2898, 1614, 1383, 1249, 1198, 988, 869, 840, 730,
1
694 cm-1; H NMR (300 MHz, CDCl3) δ 5.98 (d, J ) 18.9 Hz,
1H), 5.79 (d, J ) 18.9 Hz, 1H), 2.77 (t, J ) 6.3 Hz, 1H), 1.74-
1.55 (m, 2H), 1.4 (s, 3H), 1.05 (t, J ) 7.8 Hz, 3H), 0.08 (s, 9H);
13C NMR (75 MHz, CDCl3) δ 148.2, 131.0, 66.60, 60.36, 22.1,
14.74, 10.51, -1.38. Anal. Calcd for C10H20OSi: C, 65.15; H,
10.93. Found: C, 65.30; H, 10.75.
(2S,3R)-3-Bu tyl-2-[tr a n s-2-(tr im eth ylsilyl)vin yl]-2-p r o-
p yloxir a n e (Ta ble 1, en tr y 17). The diene substrate was
prepared by Ni-catalyzed coupling of an allylic dithioacetal
with [(trimethylsilyl)methyl]magnesium chloride7 to give a
colorless oil (79% yield): IR (NaCl) 2957, 2932, 2874, 1677,
1626, 1581, 1466, 1370, 1248, 1203, 986, 864, 838, 742, 691,
(NaCl) 3002, 3021, 2956, 1610, 1245, 982, 866, 839, 723 cm-1
;
1H NMR (300 MHz, CDCl3) δ 7.6-7.4 (m, 5H), 6.09 (d, J )
18.9 Hz, 1H), 5.95 (d, J ) 18.9 Hz, 1H), 3.95 (s, 1H), 1.19 (s,
3H), 0.11 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 147.1, 135.9,
131.9, 128.0, 127.5, 126.5, 65.62, 62.99, 14.18, -1.38. Anal.
Calcd for C14H20OSi: C, 72.35; H, 8.67. Found: C, 72.35; H,
8.75.
1
621 cm-1; H NMR (300 MHz, CDCl3) δ 6.44 (d, J ) 18.9 Hz,
1H), 5.72 (d, J ) 18.9 Hz, 1H), 5.53 (t, J ) 7.5 Hz, 1H), 2.15
(m, 4H), 1.37 (m, 6H), 0.92 (m, 6H), 0.09 (s, 9H); 13C NMR (75
MHz, CDCl3) δ 147.7, 139.8, 134.5, 124.8, 31.86, 28.3, 28.09,
22.48, 22.24, 14.37, 13.96, -1.10.
(2S,3R)-3-Isop r op yl-2-[tr a n s-2-(tr im eth ylsilyl)vin yl]-2-
p h en yloxir a n e (Ta ble 1, en tr y 15). The diene substrate
was prepared by Ni-catalyzed coupling of an allylic dithioacetal
with [(trimethylsilyl)methyl]magnesium chloride7 to give a
semicrystalline solid (86% yield): IR (NaCl) 3077, 3054, 3024,
Ep oxid e: colorless oil; [R]20 ) -26.2° (c 1.04, EtOH); IR
D
(NaCl) 2958, 2870, 1615, 1248, 989, 865, 834 cm-1; H NMR
1
2957, 2927, 2897, 2867, 1580, 1235, 988, 867, 839, 704 cm-1
;
(300 MHz, CDCl3) δ 5.93 (s, 2H), 2.72 (dd, J ) 6.6, 5.4 Hz,
1H), 1.75-1.35 (m, 10H), 0.965 (t, J ) 7.2 Hz, 3H), 0.92 (t, J
) 7.2 Hz, 3H), 0.07 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 146.2,
130.4, 66.68, 63.74, 32.22, 29.01, 28.59, 22.85, 19.02, 14.71,
1H NMR (300 MHz, CDCl3) δ 7.35 (m, 3H), 7.10 (dt, J ) 6.6,
1.5 Hz, 2H), 6.7 (dd, J ) 18.9, 0.6 Hz, 1H), 5.58 (d, J ) 10.2
Hz, 1H), 5.32 (d, J ) 18.9 Hz, 1H), 2.25 (m, 1H), 0.935 (d, J )
6.6 Hz, 6H), 0.04 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 148.0,
142.3, 140.8, 138.5, 130.1, 129.8, 128.2, 126.9, 28.53, 23.21,
-0.952.
-1.09. Anal. Calcd for
Found: C, 69.87; H, 11.51.
C14H28OSi: C, 69.93; H, 11.74.
Ep oxid e: colorless oil; [R]20 ) -29.7° (c 0.93, CHCl3); IR
D
Ack n ow led gm en t. We are grateful for the generous
financial support from the General Medical Sciences of
the National Institutes of Health (GM55704-01), the
Beckman Young Investigator Award Program, the
Camille and Henry Dreyfus New Faculty Award Pro-
gram, Colorado State University, and Hoechst Celanese.
(NaCl) 3061, 3030, 2958, 1610, 1466, 1449, 1248, 987, 864, 840,
702 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.35 (m, 5H), 6.12 (d,
J ) 18.9 Hz, 1H), 5.88 (d, J ) 18.9 Hz, 1H), 2.80 (d, J ) 8.7
Hz, 1H), 1.02 (d, J ) 5.1 Hz, 3H), 1.0-0.9 (m, 1H), 0.812 (d, J
) 6.2 Hz, 3H), 0.08 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 145.8,
136.5, 132.9, 127.9, 127.5, 127.3, 73.09, 66.45, 27.8, 19.76,
17.87, -1.42. Anal. Calcd for C16H24OSi: C, 73.78; H, 9.29.
Found: C, 73.41; H, 8.96.
Su p p or tin g In for m a tion Ava ila ble: The NMR spectral,
GC, and HPLC data for the determination of the enantiomeric
excess of the formed epoxides (10 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
(R,R)-3-Eth yl-2-m eth yl-2-[tr a n s-2-(tr im eth ylsilyl)vin y-
l]oxir a n e (Ta ble 1, en tr y 16). The diene substrate was
prepared by Ni-catalyzed coupling of an allylic dithioacetal
with [(trimethylsilyl)methyl]magnesium chloride7 to give a
colorless oil (64% yield): IR (NaCl) 2957, 2893, 2874, 1677,
1632, 1581, 1453, 1289, 1248, 1203, 986, 864, 832, 755, 730,
1
685 cm-1; H NMR (300 MHz, CDCl3) δ 6.55 (d, J ) 18.9 Hz,
1H), 5.73 (d, J ) 18.9 Hz, 1H), 5.56 (t, J ) 7.5 Hz, 1H), 2.17
J O9721195