Intramolecular ene reaction of epoxyallylsilanes: Synthesis of allyl- and vinylsilane-functionalized cyclohexanols

Article abstract of DOI:10.1021/jo051868g

Epoxyallylsilanes bearing the bulky tert-butyldiphenylsilyl group undergo an uncommon tandem rearrangement-cyclization process upon treatment with Lewis acids. Two pathways for the carbonyl ene reaction are observed: one leading to allylsilane-cyclohexano

Full text of DOI:10.1021/jo051868g

Intramolecular Ene Reaction of Epoxyallylsilanes: Synthesis of
Allyl- and Vinylsilane-Functionalized Cyclohexanols
Asuncio´n Barbero, Pilar Castren˜o, Gloria Ferna´ndez, and Francisco J. Pulido*
Departamento de Quı´mica Orga´nica, Facultad de Ciencias, C/Dr Mergelina s/n, 47011 Valladolid, Spain
pulido@qo.uva.es
Received September 6, 2005
Epoxyallylsilanes bearing the bulky tert-butyldiphenylsilyl group undergo an uncommon tandem
rearrangement-cyclization process upon treatment with Lewis acids. Two pathways for the carbonyl
ene reaction are observed: one leading to allylsilane-cyclohexanols when the epoxyallylsilane
(28-31) is nonsubstituted, 2-, or 4-monosubstituted and other leading to vinylsilane-cyclohexanols
when the epoxyallylsilane (24-27) is 2,4-disubstituted or trisubstituted. An explanation for the
observed regio- and stereoselectivity is advanced and a reliable mechanism proposed.
Introduction
charge in the Lewis acid mediated intramolecular process
overrides entropic and stereoelectronic factors. Thus,
under Lewis acid conditions, nucleophilic substitution
usually takes place at the most substituted carbon center
of the epoxide5 unless the presence of electron-withdraw-
ing groups next to the epoxide destabilizes the developing
carbocation.6 Contrary to the normal 5-exo7 or 6-endo8
attack,9 we have recently reported that the acid-cata-
lyzed reaction of epoxyallylsilanes containing the phen-
yldimethylsilyl group follows an unusual rearrange-
Organosilicon compounds display a multitude of func-
tions in organic synthesis.1 The usefulness of these
versatile building blocks in stereoselective reactions can
be attributed both to their ability to react with electro-
philes via selective formation of a carbocation â to the
silyl group (the so-called â-effect) and to their stability
toward a large number of functional groups and reaction
conditions. Among them, allylsilanes have been widely
recognized as valuable intermediates for the construction
of ring systems, especially in the area of natural products
synthesis.2 Several groups have reported the synthesis
of carbo- and heterocyclic compounds3 by the Lewis acid
promoted reaction of allylsilanes with carbonyl deriva-
tives or related compounds (Sakurai-Hosomi reaction).4
Despite its synthetic potential, the cyclization of
epoxyallylsilanes has not been widely explored. It has
been reported that the stabilization of the incipient
(4) (a) Hosomi, A.; Sakurai, H. J. Am. Chem. Soc. 1977, 99, 1673.
(b) Heathcock, C. H. J. Am. Chem. Soc. 1983, 105, 2354. (c) Schlosser,
M.; Franzini, L.; Bauer, C.; Leroux, F. Chem. Eur. J. 2001, 7, 1909.
(d) Yadav, J. S.; Chand, P. K.; Anjaneyulu, S. Tetrahedron Lett. 2002,
43, 3783.
(5) (a) Beszant, S.; Giannini, E.; Zanoni, G.; Vidari, G. Tethaedron:
Asymmetry 2002, 13, 1245. (b) Wang, D.; Chan, T.-H. J. Chem. Soc.,
Chem. Commun. 1984, 1273. (c) Armstrong, R. J.; Weiler, L. Can. J.
Chem. 1986, 64, 584. (d) Tan, T. S.; Mather, A. N.; Procter, G.;
Davidson, A. H. J. Chem. Soc., Chem. Commun. 1984, 585. (e)
Overman, L. E.; Renhowe, P. A. J. Org. Chem. 1994, 59, 4138.
(6) (a) Proctor, G.; Russell, A. T.; Murphy, P. J.; Tan, T. S.; Mather,
A. N. Tetrahedron 1988, 44, 3953. (b) Molander, G. A.; Andrews, S.
W. J. Org. Chem. 1989, 54, 3114. (c) Sugita, Y.; Kimura, Y.; Yokoe, I.
Tetrahedron Lett. 1999, 40, 5877.
(1) Roush, W. R. Comprehensive Organic Synthesis; Heathcock, C.
H., Ed.; Pergamon: Oxford, 1990; Vol. 2, p 1.
(2) (a) Barbero, A.; Pulido, F. J. Acc Chem Res. 2004, 37, 817. (b)
Langkopf, E.; Schinzer, D. Chem. Rev. 1995, 95, 1375.
(3) Within others, see: (a) Barbero, A.; Garc´ıa, C.; Pulido, F. J.
Tetrahedron 2000, 56, 2739. (b) Akiyama, T.; Yamanaka, M. Synlett
1996, 1095. (c) Osumi, K.; Sugimura, H. Tetrahedron Lett. 1995, 36,
5789. (d) Panek, J. S.; Jain, N. F. J. Org. Chem. 1994, 59, 2674.
(7) Nishitani, K.; Harada, Y.; Nakamura, Y.; Yokoo, K.; Yamakawa,
K. Tetrahedron Lett. 1994, 35, 7809.
(8) Jung, M. E.; Cho, Y. M.; Jung, Y. H. Tetrahedron Lett. 1996,
37, 3.
10.1021/jo051868g CCC: $30.25 © 2005 American Chemical Society
Published on Web 11/18/2005
J. Org. Chem. 2005, 70, 10747-10752
10747

Barbero et al.
SCHEME 1
SCHEME 2
ment-cyclization process which leads to methylenecy-
clohexanols.10 From previous work, it is clear that the
behavior of the tert-butyldiphenylsilyl group is percep-
tively different from that observed for the phenyldi-
methylsilyl group.11 In this paper, we report the acid-
catalyzed cyclization reaction of allyl-tert-butyldiphen-
ylepoxysilanes and we show their interesting reactivity
pattern.
SCHEME 3
Epoxyallylsilanes have been previously prepared by
Wittig reaction of an aldehyde with Ph3PdCHCH2SiMe3
followed by epoxidation12 and by cross-metathesis of
alkenyl epoxides and allylsilanes.13 Following our meth-
odology,10 we describe herein a new route for the syn-
thesis of epoxyallylsilanes carrying the tert-butyldiphen-
ylsilyl group by silylcupration of allene, followed by
capture of the intermediate cuprate with enones and final
formation of the epoxide via sulfur ylides.
Silylcupration of allene leads to the formation of
intermediate cuprates, which react with electrophiles to
afford either vinyl or allylsilanes.2,14 The regiochemistry
of the addition depends on various factors such as the
nature of the cuprate, the substitution of the allene, the
temperature of the reaction, and the nature of the silyl
group. Thus, the reaction of 1,2-propadiene with higher
order silylcyanocuprates 1 containing the phenyldimeth-
ylsilyl group gives, at any temperature between -78 and
0 °C, a vinylsilane-allylcuprate intermediate 2, which
readily reacts with a wide variety of electrophiles leading
to the corresponding vinylsilanes (Scheme 1).
TABLE 1. Synthesis of Oxoallylsilanes
oxo
yield
entry compd activant R1 R2 R3 oxoallylsilane (%)
1
2
3
4
5
6
7
8
8
BF3‚OEt2 Me Ph
H
16
17
18
19
20
21
22
23
85
90
89
88
88
90
90
80
9
BF3‚OEt2 Me Me Me
10
11
12
13
14
15
BF3‚OEt2 Et Me
BF3‚OEt2 Me i-Pr
H
H
H
H
H
H
TMSCl
TMSCl
TMSCl
TMSCl
Et
Me
H
H
H
H
Me
H
TABLE 2. Synthesis of Epoxyallylsilanes
yield
entry oxoallylsilane R1
R2
R3 epoxyallylsilane (%)
However, the silylcupration of allene, at -78 °C, using
a bulkier silyl reagent as the higher order cuprate
(tBuPh2Si)2CuCNLi2 3, gives rise to an allylsilane-
vinylcuprate intermediate 4 where the steric hindrance
of the silyl group forces it to the end of the allenic system
(Scheme 2). This result is of interest since it opens a route
for the synthesis of functionalized allylsilanes 5 (Scheme
1
2
3
4
5
6
7
8
16
17
18
19
20
21
22
23
Me Ph
H
24
25
26
27
28
29
30
31
74a
78
Me Me Me
Et Me
Me i-Pr
H
H
H
H
H
H
68a
65a
75
Et
Me
H
H
H
72
H
Me
72
H
70a
t
2). The use of a lower order cuprate BuPh2SiCuCNLi 6
a Diastereomeric ratio (R*,R*)/(R*,S*) approximately 1:1.
shows a similar regioselectivity pattern and offers the
possibility of a cheaper methodology since just 1 equiv
of silyllithium is required (Scheme 3).
which reacts smoothly with R,â-unsaturated carbonyl
compounds 8-15 to afford after quenching with satd
NH4Cl compounds 16-23 in good yield. All the reactions
(THF) were carried out in the presence of BF3‚OEt2 or
TMSCl, which considerably increased the yields (Scheme
3, Table 1).
The oxoallylsilanes thus obtained were treated with
dimethylsulfonium methylide to give in good yield the
corresponding epoxides 24-31 (Table 2). Compounds 24,
26, 27, and 31 were isolated as mixtures of diastereomers
in almost equimolar ratio (Table 2). For compound 24,
both diastereomers (24a and 24b) could be separated by
chromatography and their relative R/S configuration
assigned. In the other cases, they were used as a mixture
Results and Discussion
Thus, tert-butyldiphenylsilylcuprate 6 readily adds to
allene at -40 °C to give a vinylcopper intermediate 7,
(9) (a) Corey, E. J.; Staas, D. D. J. Am. Chem. Soc. 1998, 120, 3526.
(b) Molander, G. A.; Shubert, D. C. J. Am. Chem. Soc. 1987, 109, 576.
(10) Barbero, A.; Castren˜o, P.; Pulido, F. J. Org. Lett. 2003, 5, 4045.
(11) (a) Barbero, A.; Castren˜o, P.; Garc´ıa, C.; Pulido, F. J. J. Org.
Chem. 2001, 66, 7723. (b) Barbero, A.; Cuadrado, P.; Gonza´lez, A. M.;
Pulido, F. J.; Fleming, I.; Sa´nchez, A. J. Chem. Soc., Perkin Trans. 1
1995, 1525.
(12) Seyferth, D.; Wursthorn, K. R.; Mammarella, R. E. J. Org.
Chem. 1977, 42, 3104.
(13) Langer, P.; Holtz, E. Synlett 2002, 110.
(14) Fleming, I.; Pulido, F. J. Chem. Commun. 1986, 1010.
10748 J. Org. Chem., Vol. 70, No. 26, 2005

Intramolecular Ene Reaction of Epoxyallylsilanes
TABLE 3. Acid-Catalyzed Cyclization of
Epoxyallylsilanes
SCHEME 4
of diastereomeric epoxides in the subsequent cyclization,
which apparently does not represent a limitation since
it was verified that both diastereomers 24a and 24b lead
separately to the same result.
As we noted previously for epoxyallylsilanes bearing
the phenyldimethylsilyl group,10 the reaction of com-
pounds 24-31, in the presence of a Lewis acid, occurs
through a rearrangement-cyclization process, where the
first stage involves Lewis acid promoted isomerization
of the epoxy group to an aldehyde I and the second stage
occurs by intramolecular ene reaction between the oxo
group and the allylsilane unit (Scheme 4). To our
knowledge, this is the first time that this sequential type
of process has been observed15 in the acid-catalyzed
cyclization of epoxyallysilanes. The former observation
allows us to assert that rearrangement of these epoxides
occur much faster than nucleophilic substitution on the
epoxy group. Moreover, the fact that the Lewis acid
cyclization of 24a or 24b gives the same result seems to
indicate that the reaction proceeds through common
intermediates and, in consequence, that rearrangement
to the aldehyde takes place prior to cyclization. The
degree of concertedness between the two steps is still
uncertain.16 Surprisingly, the presence of the tert-butyl-
diphenylsilyl group introduces another special feature in
these epoxyallylsilane cyclizations, when compared with
the phenyldimethylsilyl series,10 since the hindered silyl
group is maintained along the whole process. Recently,
Alcaide et al.17 described the preparation of six-membered
rings by Lewis acid promoted carbonyl-ene cyclization,
and we previously reported the intramolecular ene reac-
tion of oxoallylsilanes containing the tert-butyldiphenyl-
silyl group.11a
a Cyclization conditions: BF3‚OEt2, DCM, 0 °C.
for the 2,4,4-trisubstituted epoxyallylsilane 25. Obvi-
ously, 33c is formed by cyclization of the cation primarily
formed by ring opening of the epoxide before the rear-
rangement to the aldehyde. The stereoisomers collected
in Table 3 could be adequately separated by flash
chromatography. The structural assignments of the dif-
ferent products were established by means of careful 1H,
COSY, and NOESY studies and X-ray analysis.
The regioselectivity of the cyclization depends dramati-
cally upon the substitution of the epoxyallylsilane. Thus,
nonsubstituted and 2- or 4-monosubstituted epoxyallyl-
silanes 28-31 give exclusively allylsilanes 36-39, upon
treatment with Lewis acids (Table 3, entries 5-8).
However, 2,4-disubstituted epoxyallylsilanes 24-27 give
either mixtures of vinylsilanes and allylsilanes or exclu-
sively vinylsilanes (Table 3, entries 1-4). The only
example in which we found some of the normal product
(33c) of 5-exo attack, predicted by the Baldwin rules, is
From the classical mechanistic standpoint, it is gener-
ally agreed that the concerted ene reaction of allylsi-
lanes18
involves a highly asynchronous transition state
featuring a well-developed C-C bond prior to a relatively
late proton transfer toward the oxygen.19 Consequently,
the ene transition state has dipolar character, and the
silyl group, which enhances the nucleophilicity of the
double bond, is also a powerful force for the stabilization
of the partial positive charge at the â-carbon atom.
(15) Products of epoxide rearrangement have been obtained in a
similar cyclization reaction: Xiao, X.-Y.; Park, S.-K.; Prestwich, G. D.
J. Org. Chem. 1988, 53, 4869.
(18) (a) Monti, H.; Laval, G.; Feraud, M. Eur. J. Org. Chem. 1999,
8, 1825. (b) Dumeunier, R.; Leclercq, C.; Marko, E. Tetrahedron Lett.
2002, 43, 2307.
(19) (a) Monti, H.; Audran, G.; Feraud, M.; Monti, J. P.; Leandri,
G. Tetrahedron 1996, 52, 6685. (b) Robertson, J.; O’Connor, G.
Tetrahedron Lett. 1996, 37, 3411. (c) O’Brien, M.; Taylor, N. H.;
Thomas, E. J. Tetrahedron Lett. 2002, 43, 5491.
(16) We were not able to isolate or detect aldehydes resulting from
isomerization of the starting epoxyallylsilane.
(17) Alcaide, B.; Pardo, C.; Rodriguez-Ranera, C.; Rodriguez-Vicente,
A. Org. Lett. 2001, 3, 4205.
J. Org. Chem, Vol. 70, No. 26, 2005 10749

Barbero et al.
SCHEME 5
proximity with the negative part of the enophile. Stereo-
chemistry has been corroborated by X-ray analysis of 33a
(Figure 1).
Conclusions
In summary, epoxyallylsilanes containing the bulky
tert-butyldiphenylsilyl group undergo, upon treatment
with Lewis acid, a sequential rearrangement-cyclization
process, which leads stereoselectively to allyl- and vinyl-
silane functionalized cyclohexanol derivatives. The low
electrofugacity of the tert-butyldiphenylsilyl group com-
pared with other silyl groups is responsible for the
formation of silicon containing cyclic products. Formally,
the cyclization follows an ene mechanism, through a
chairlike transition state of type A or B, leading to the
formation of either allyl- or vinylsilanes depending upon
the structure of the starting epoxyallylsilane.
Experimental Section
Silylcupration of Allene. Preparation of Intermediate
7. A solution of tert-butyldiphenylsilyllithium11b (6 mmol) in
THF was added by syringe to a stirred suspension of copper-
(I) cyanide (6 mmol) in THF at 0 °C. After 30 min at this
temperature, the solution of tert-butyldiphenylsilylcopper 6 (6
mmol) was cooled at -40 °C and a slight excess of allene was
added from a balloon. The mixture was stirred for 1 h and
then used immediately.
Reaction of Intermediates 7 with R,â-Unsaturated
Carbonyl Compounds. BF3‚OEt2 or TMSCl (6 mmol) was
added at -78 °C to the solution previously prepared and the
mixture stirred for an additional period of 10 min. The
aldehydes or ketones 8-15 (6 mmol) in THF were slowly
dropped in at -78 °C and stirred at this temperature for 1 h.
After gentle warming to 0 °C, the mixture was quenched with
saturated ammonium chloride solution and extracted twice
with ether. The organic layer was dried (MgSO4), evaporated,
and chromatographed to give the corresponding products
16-23 (Table 1). Compounds 16,3a 17,11a and 1811a were
previously described.
5-tert-Butyldiphenylsilylmethyl-4-isopropylhex-5-en-
2-one (19): colorless oil; IR (neat, cm-1) 1715, 1630; 1H NMR
(CDCl3) δ 7.75-7.45 (m, 10H), 4.66 (s, 1H), 4.56 (s, 1H), 2.39-
2.20 (m, 4H), 2.12 (d, J ) 16 Hz, 1H), 1.91 (s, 3H), 1.78-1.67
(m, 1H), 1.04 (s, 9H, tBu-Si), 0.77 (d, J ) 6.8 Hz, 3H), 0.73 (d,
J ) 6.8 Hz, 3H); 13C NMR (CDCl3) δ 208.2, 147.1, 136.2, 134.6,
134.3, 129.0, 127.4, 112.8, 48.8, 44.4, 29.8, 29.7, 27.8, 20.8, 18.8,
18.5. Anal. Calcd for C26H36SiO: C, 79.53; H, 9.24. Found: C,
79.88; H, 9.51.
FIGURE 1. X-ray crystal structure of (E)-(1R*,2S*)-5-tert-
butyldiphenylsilylmethylene-2,4,4-trimethylcyclohexanol.
Three transition states A1, A2, and B may account for
all of the observed compounds (Scheme 5). In the case of
the 2- or 4-monosubstituted epoxyallylsilanes, a simple
examination of the molecular structure shows that the
completion of the H-ene reaction is favored by a well-
positioned endocyclic axial hydrogen, with the 2- or
4-substituent occupying an equatorial position in a
chairlike transition state A1 (R1 or R2 ) H). This is an
energetically favored transition state since the endocyclic
axial C-H bond and the σ C-Si bond are both coplanar
to the empty carbon p-orbital, and therefore, the â-C-Si
bond hyperconjugation is not perturbed. Formation pref-
erential of trans products (36b and 37b) should be a
consequence of the difference of energy between transi-
tion states A1 and A2, the latter being more crowded.
However, for 2,4-disubstituted epoxyallylsilanes (R1
and R2 * H) there are two possible pathways for the ene
reaction, depending on the stereochemistry of the inter-
mediate aldehyde I. Thus, for the pseudo-cis stereoiso-
mer, both substituents in the 2- and 4-position will be
equatorial, and then the transition state A1 will be still
favored since there is an appropriate pseudoaxial hydro-
gen in the allylic position. However, for the pseudo-trans
stereoisomer, where one of the substituents (the bulkier)
will be equatorial and the other will be axial, there is
competitiveness between two energetically close transi-
tion states A2 and B. Thus, in the transition state A2 the
hyperconjugation effect is not perturbed but there is an
unfavorable sterical interaction with the 2-substituent
in axial. On the contrary, in the transition state B the
hydrogens of the exocyclic R-silylated position are both
accessible to the carbonyl group without steric repulsion,
but the â-C-Si bond hyperconjugation is seriously per-
turbed since the required coplanarity is lost.
6-tert-Butyldiphenylsilylmethylhept-6-en-3-one (20):
1
colorless oil; IR (neat, cm-1) 1716, 1636, 1106, 736; H NMR
(CDCl3) δ 7.61-7.42 (m, 10H), 4.65 (s, 1H), 4.54 (s, 1H), 2.29-
2.18 (m, 4H), 2.22 (s, 2H), 1.91 (t, J ) 7.7 Hz, 2H), 1.09 (s, 9H,
tBu-Si), 0.96 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3) δ 211.0,
145.6, 136.1, 134.6, 129.1, 127.4, 109.8, 40.5, 35.4, 32.3, 27.7,
20.6, 18.5, 7.7. Anal. Calcd for C24H32SiO: C, 79.06; H, 8.85.
Found: C, 79.39; H, 9.11.
5-tert-Butyldiphenylsilylmethylhex-5-en-2-one (21): col-
orless oil; IR (neat, cm-1) 1717, 1627, 1105, 910; 1H NMR
(CDCl3) δ 7.74-7.39 (m, 10H), 4.73 (s, 1H), 4.60 (s, 1H), 2.31-
2.28 (m, 4H), 1.97-1.95 (m, 2H), 1.95 (s, 3H), 1.15 (s, 9H,
tBu-Si); 13C NMR (CDCl3) δ 208.2, 145.4, 136.2, 134.6, 129.2,
127.5, 109.9, 41.8, 32.2, 29.5, 27.8, 20.6, 18.6. Anal. Calcd for
C23H30SiO: C, 78.80; H, 8.63. Found: C, 79.15; H, 8.94.
4-tert-Butyldiphenylsilylmethylpent-4-enal (22): color-
Moreover, the selective formation of E-vinylsilanes (32,
33a 34a, and 35a) indicates that, in the transition state
B, the bulky silyl group attains an orientation anti to
the 4-substituent for minimal steric repulsions (Scheme
5); in this way, only one of the methylene hydrogens R
to silicon is selectively transferred, just the one in close
1
less oil; IR (neat, cm-1) 1726, 1636, 1105; H NMR (CDCl3) δ
9.40 (t, J ) 2.0, 1H), 7.64-7.45 (m, 10H), 4.72 (s, 1H), 4.56 (s,
1H), 2.27 (td, J ) 7.3 and 2.0 Hz, 2H), 2.24 (s, 2H), 1.96 (t, J
) 7.3 Hz, 2H), 1.11 (s, 9H, tBu-Si); 13C NMR (CDCl3) δ 202.3,
10750 J. Org. Chem., Vol. 70, No. 26, 2005

Intramolecular Ene Reaction of Epoxyallylsilanes
144.9, 136.1, 134.4, 129.2, 127.5, 110.3, 41.5, 30.3, 27.7, 20.6,
18.5. Anal. Calcd for C22H28SiO: C, 78.51; H, 8.39. Found: C,
79.85; H, 8.91.
7.77-7.27 (m, 10H), 4.73 (s, 1H), 4.62 (s, 1H), 2.44 (d, J ) 4.6
Hz, 1H), 2.30 (d, J ) 4.6 Hz, 1H), 2.15 (d, J ) 16.4 Hz, 1H),
2.06 (d, J ) 16.4 Hz, 1H), 1.90-1.58 (m, 3H), 1.31-1.23 (m,
1H), 1.04 (s, 3H), 1.02 (s, 9H, tBu-Si), 0.81 (d, J ) 6.9 Hz, 3H),
0.74 (d, J ) 6.9 Hz, 3H), 27b 4.72 (s, 1H), 4.60 (s, 1H), 2.42 (d,
J ) 4.8 Hz, 1H), 2.38 (d, J ) 4.8 Hz, 1H), 2.03 (d, J ) 16.0 Hz,
1H), 1.06 (s, 3H), 0.72 (d, J ) 6.8 Hz, 3H); 13C NMR (CDCl3)
δ 27a 146.4, 136.2, 136.1, 134.3, 129.1, 127.4, 113. 6, 56.5, 53.8,
50.6, 36.1, 29.8, 27.8, 20.9, 20.7, 18.9, 18.4, 17.8, 27b 113.4,
55.1, 53.1, 49.6, 35.4, 29.3, 21.6, 20.5, 19.2, 17.6. Anal. Calcd
for C27H38SiO: C, 79.74; H, 9.42. Found: C, 80.09; H, 9.74.
5-tert-Butyldiphenylsilylmethyl-2-ethyl-1,2-epoxyhex-
5-ene (28): colorless oil; IR (neat, cm-1) 1636, 1463, 1105, 820;
1H NMR (CDCl3) δ 7.69-7.34 (m, 10H), 4.67 (s, 1H), 4.58 (s,
1H), 2.43 (d, J ) 4.6 Hz, 1H), 2.28 (d, J ) 4.6 Hz, 1H), 2.22 (s,
2H), 1.67-1.58 (m, 4H), 1.35 (q, J ) 7.6 Hz, 2H), 1.10 (s, 9H,
tBu-Si), 0.79 (t, J ) 7.6 Hz, 3H); 13C NMR (CDCl3) δ 146.3,
136.1, 134.7, 129.1, 127.4, 109. 4, 59.8, 51.9, 33.1, 31.9, 27.7,
26.7, 20.7, 18.5, 8.7. Anal. Calcd for C25H34SiO: C, 79.31; H,
9.05. Found: C, 79.69; H, 9.34.
4-tert-Butyldiphenylsilylmethyl-3-methylpent-4-enal
1
(23): colorless oil; H NMR (CDCl3) δ 9.20 (s, 1H), 7.69-7.37
(m, 10H), 4.71 (s, 1H), 4.59 (s, 1H), 2.24-2.15 (m, 3H), 2.23
(s, 2H), 1.09 (s, 9H, tBu-Si), 0.89 (d, J ) 6.5 Hz, 3H); 13C NMR
(CDCl3) δ 202.8, 149.7, 136.2, 134.5, 129.2, 127.7, 109.5, 49.5,
35.1, 27.8, 19.5, 18.9, 18.5. Anal. Calcd for C23H30SiO: C, 78.80;
H, 8.63. Found: C, 79.18; H, 8.98.
Synthesis of Epoxyallylsilanes. To a solution of tri-
methylsulfonium iodide (1 mmol) in dry THF (5 mL) was added
dropwise BuLi (1 mmol, 1.6 M BuLi in hexanes) and the
mixture stirred for 5 min at 0 °C. Then a solution of the
oxoallylsilane (0.8 mmol) in THF (1 mL) was added. After the
solution was stirred for an additional 30 min at 0 °C and 1 h
at rt, brine (10 mL) was added and the mixture extracted with
ether, dried, and evaporated to dryness. The residue was
purified by chromatography to give epoxyallylsilanes 24-31.
Compounds 24, 26, 27, and 31 were isolated as mixtures
(∼1:1) of diastereomers. In the case of compound 24, both
diastereomers (24a and 24b) could be cleanly separated by
chromatography and their relative R/S configuration assigned
by comparison with the analogous compound bearing the
PhMe2Si group,10 the latter unequivocally identified by X-ray
characterization.10
5-tert-Butyldiphenylsilylmethyl-2-methyl-1,2-epoxyhex-
5-ene (29): colorless oil; IR (neat, cm-1) 1633, 1425, 1106, 906;
1H NMR (CDCl3) δ 7.71-7.36 (m, 10H), 4.71 (s, 1H), 4.61 (s,
1H), 2.41 (d, J ) 4.8 Hz, 1H), 2.35 (d, J ) 4.8 Hz, 1H), 2.25 (s,
t
2H), 1.71-1.36 (m, 4H), 1.12 (s, 9H, Bu-Si), 1.07 (s, 3H);
13C NMR (CDCl3) δ 146.2, 136.2, 134.7, 129.1, 127.5, 109.5,
56.7, 53.6, 34.8, 33.5, 27.8, 20.7, 20.6, 18.6. Anal. Calcd for
C24H32SiO: C, 79.06; H, 8.85. Found: C, 79.39; H, 9.14.
5-tert-Butyldiphenylsilylmethyl-1,2-epoxyhex-5-ene
(2R*,4R*)-5-tert-Butyldiphenylsilylmethyl-2-methyl-4-
phenyl-1,2-epoxyhex-5-ene (24a): colorless oil; 1H NMR
(CDCl3) δ 7.72-6.98 (m, 15H), 4.93 (s, 1H), 4.89 (s, 1H), 2.82-
2.78 (m, 1H), 2.34 (d, J ) 14.2 Hz, 1H), 2.12-2.05 (m, 1H),
2.04 (d, J ) 4.3 Hz, 1H), 1.86 (d, J ) 14.2 Hz, 1H), 1.70 (d, J
) 4.3 Hz, 1H), 1.51-1.40 (m, 1H), 1.11 (s, 9H, tBu-Si), 0.91(s,
3H); 13C NMR (CDCl3) δ 148.8, 142.7, 136.5, 136.3, 134.9,
134.5, 129.3, 129.2, 128.2, 128.1, 127.6, 127.5, 126.6, 109.2,
1
(30): colorless oil; IR (neat, cm-1) 1630, 1440, 1110, 705; H
NMR (CDCl3) δ 7.70-7.27 (m, 10H), 4.71 (s, 1H), 4.64 (s, 1H),
2.68-2.60 (m, 2H), 2.28-2.25 (m, 1H), 2.25 (s, 2H), 1.82-1.71
t
(m, 2H), 1.57-1.38 (m, 2H), 1.11 (s, 9H, Bu-Si); 13C NMR
(CDCl3) δ 145.8, 136.2, 134.7, 129.1, 127.5, 110.1, 51.9, 47.0,
34.2, 30.5, 27.8, 20.4, 18.6. Anal. Calcd for C23H30SiO: C, 78.80;
H, 8.63. Found: C, 79.13; H, 8.94.
55.7, 54.5, 48.7, 42.2, 27.7, 20.6, 19.9, 18.6; MS m/z 383 (M+
-
tBu), 199.
(2R*,4S*)-5-tert-Butyldiphenylsilylmethyl-2-methyl-4-
phenyl-1,2-epoxyhex-5-ene (24b): colorless oil; 1H NMR
(CDCl3) δ 7.67-7.01 (m, 15H), 4.82 (s, 1H), 4.80 (s, 1H), 2.88
(dd, J ) 10.2 and 4.7 Hz, 1H), 2.27 (d, J ) 4.8 Hz, 1H), 2.23
(d, J ) 14.6 Hz, 1H), 2.20 (d, J ) 4.8 Hz, 1H), 1.95 (dd, J )
13.9 and 10.2 Hz, 1H), 1.86 (d, J ) 14.6 Hz, 1H), 1.72 (dd, J
(2R*,4R*)- and (2R*,4S*)-5-tert-Butyldiphenylsilyl-
methyl-4-methyl-1,2-epoxyhex-5-ene (31): colorless oil; IR
(neat, cm-1) 1633, 1426, 1105, 788; 1H NMR (CDCl3) δ 31a
7.78-7.26 (m, 10H), 4.66 (s, 2H), 2.69-2.61 (m, 2H), 2.36 (dd,
J ) 5.0 and 3.1 Hz, 1H), 2.32-2.23 (m, 2H), 1.96-1.20 (m,
3H), 1.11 (s, 9H, tBu-Si), 0.93 (d, J ) 7.0 Hz, 3H), 31b 4.71 (s,
1H), 4.69 (s, 1H); 13C NMR (CDCl3) δ 31a 150.4, 136.2, 134.5,
129.0, 127.4, 109.1, 51.2, 46.7, 39.0, 38.4, 27.8, 19.5, 18.5,
18.4, 31b 109.0, 50.9, 47.5, 38.2, 38.1, 19.1. Anal. Calcd for
C24H32SiO: C, 79.06; H, 8.85. Found: C, 79.41; H, 9.17.
Cyclization of Epoxyallylsilanes. BF3‚OEt2 (1.4 mmol)
was slowly added to a solution of 24-31 (1 mmol) in DCM (10
mL) under nitrogen at 0 °C. After the mixture was slowly
stirred for 30 min at this temperature, brine was added and
the mixture extracted with ether. The organic layer was dried
over MgSO4, the solvent was evaporated, and the residue was
purified by chromatography. Compound 33b was already
described.10
t
) 13.9 and 4.7 Hz, 1H), 1.03 (s, 9H, Bu-Si), 0.77 (s, 3H). 13C
NMR (CDCl3) δ 148.8, 143.0, 136.4, 136.3, 134.8, 134.5, 129.2,
128.4, 128.3, 127.5, 126.5, 109. 8, 56.2, 53.1, 49.4, 41.2, 27.8,
t
21.5, 18.9, 18.6; MS m/z 383 (M+ - Bu), 199. Anal. Calcd for
C30H36SiO: C, 81.76; H, 8.23. Found: C, 82.15; H, 8.51.
5-tert-Butyldiphenylsilylmethyl-2,4,4-trimethyl-1,2-
epoxyhex-5-ene (25): colorless oil; 1H NMR (CDCl3) δ 7.73-
7.27 (m, 10H), 4.79 (s, 1H), 4.67 (s, 1H), 2.63 (d, J ) 4.9 Hz,
1H), 2.54 (dd, J ) 4.9 and 1.1 Hz, 1H), 2.16 (s, 2H), 2.07 (dd,
J ) 14.3 and 1.1 Hz, 1H), 1.45 (d, J ) 14.3 Hz, 1H), 1.33 (s,
t
9H, Bu-Si), 1.06 (s, 3H), 1.03 (s, 3H), 1.01 (s, 3H); 13C NMR
(CDCl3) δ 151.0, 136.2, 134.6, 134.5, 129.0, 127.4, 112.4, 55.9,
54.9, 47.3, 39.8, 28.5, 27.9, 27.5, 22.2, 18.5, 12.8. Anal. Calcd
for C26H36SiO: C, 79.53; H, 9.24. Found: C, 79.85; H, 9.58.
(2R*,4R*)- and (2R*,4S*)-5-tert-butyldiphenylsilyl-
methyl-2-ethyl-4-methyl-1,2-epoxyhex-5-ene (26): colorless
(E)-(1R*,2R*,4S*)-5-tert-Butyldiphenylsilylmethylene-
2-methyl-4-phenylcyclohexanol (32): colorless oil; IR (neat,
cm-1) 3560, 3450, 1610, 1430, 1100; 1H NMR (CDCl3) δ 7.81-
7.72 (m, 4H), 7.47-7.35 (m, 11H), 5.84 (s, 1H), 3.82-3.80 (m,
1H), 2.94 (ddd, J ) 12.5, 9.1 and 4.1 Hz, 1H), 2.44 (dd, J )
10.1 and 4.5 Hz, 1H), 2.22 (dd, J ) 13.2 and 4.1 Hz, 1H), 1.80
(dd, J ) 13.2 and 9.1 Hz, 1H), 1.68-1.57 (m, 2H), 1.04 (s, 9H),
0.99 (d, J ) 6.5 Hz, 3H); 13C NMR (CDCl3) δ 161.5,
142.1, 136.0, 135.3, 129.1, 128.4, 127.7, 127.6, 127.5, 126.0,
120.2, 75.6, 50.6, 40.5, 35.8, 34.1, 27.3, 18.2, 17.9; MS m/z 441
1
oil; IR (neat, cm-1) 1635, 1428, 1105; H NMR (CDCl3) δ 26a
7.67-7.27 (m, 10H), 4.62 (s, 1H), 4.60 (s, 1H), 2.46 (d, J ) 4.8
Hz, 1H), 2.35 (d, J ) 4.8 Hz, 1H), 2.27 (d, J ) 14.7 Hz, 1H),
2.10 (d, J ) 14.7 Hz, 1H), 1.90-1.80 (m, 1H), 1.50-1.31 (m,
4H), 1.07 (s, 9H, tBu-Si), 0.84 (d, J ) 6.6 Hz, 3H), 0.77 (t, J )
7.5 Hz, 3H), 26b 4.63 (s, 1H), 4.58 (s, 1H), 2.52 (d, J ) 4.8 Hz,
1H), 2.44 (d, J ) 4.8 Hz, 1H); 13C NMR (CDCl3) δ 26a 151.1,
136.3, 136.2, 134.7, 134.5, 129.1, 127.4, 108.9, 59.2, 51.3, 40.2,
37.0, 27.9, 26.3, 19.5, 18.7, 18.5, 9.1, 26b 108.5, 59.0, 53.1, 40.1,
26.1, 19.1, 18.9, 8.5. Anal. Calcd for C26H36SiO: C, 79.53; H,
9.24. Found: C, 79.87; H, 9.51.
t
(M+), 423 (M+ - H2O), 239 (Ph2 BuSi), 199. Anal. Calcd for
C30H36OSi: C, 81.76; H, 8.23. Found: C, 82.07; H, 8.57.
(E)-(1R*,2S*)-5-tert-Butyldiphenylsilylmethylene-2,4,4-
trimethylcyclohexanol (33a): white crystals; mp 88-89 °C;
IR (neat, cm-1) 3560, 1590, 1420, 1100; 1H NMR (CDCl3) δ
7.81-7.37 (m, 10H), 5.92 (s, 1H), 3.45-3.39 (m, 1H), 2.20 (d,
J ) 3.1 Hz, 2H), 1.85-1.72 (m, 1H), 1.51 (t, J ) 13.0 Hz, 1H),
1.28 (s, 3H), 1.20 (s, 3H), 1.23-1.14 (m, 1H), 1.01 (s, 9H), 0.84
(2R*,4R*)- and (2R*,4S*)-5-tert-butyldiphenylsilyl-
methyl-2-methyl-4-isopropyl-1,2-epoxyhex-5-ene (27): col-
orless oil; IR (neat, cm-1) 1636, 1105; 1H NMR (CDCl3) δ 27a
J. Org. Chem, Vol. 70, No. 26, 2005 10751

Barbero et al.
(d, J ) 6.7 Hz, 3H), 0.09 (d, J ) 3.1 Hz, 1H); 13C NMR (CDCl3)
δ 165.9, 136.6, 136.1, 135.7, 134.5, 129.0, 127.9, 127.6, 115.0,
71.9, 42.9, 39.8, 39.0, 32.0, 29.5, 27.6, 27.3, 18.1, 17.8; MS m/z
7.30 (m, 6H), 3.15-3.05 (m, 1H), 2.54 (sept, J ) 6.8 Hz, 1H),
2.13 (d, J ) 14.4 Hz, 1H), 2.11-2.02 (m, 1H), 2.05 (d, J ) 14.4
Hz, 1H), 1.97-1.75 (m, 3H), 1.50-1.40 (m, 2H), 1.10 (s, 9H),
0.89 (d, J ) 6.3 Hz, 3H), 0.71 (d, J ) 6.8 Hz, 3H), 0.56 (d, J )
6.8 Hz, 3H); 13C NMR (CDCl3) δ 136.2, 134.9, 134.7, 132.2,
129.0, 127.2, 122.8, 72.6, 41.1, 35.3, 30.3, 29.2, 27.6, 19.9, 19.6,
18.3, 17.5, 15.6.
t
t
t
335 (M+ - Bu), 317 (M+ - Bu - H2O), 239 (Ph2 BuSi).
3-tert-Butyldiphenylsilylmethyl-1,4,4-trimethylcyclo-
pent-2-enylmethanol (33c): colorless oil; IR (neat, cm-1
)
3560, 1590,1420, 1100; 1H NMR (CDCl3) δ 7.76-7.65 (m, 4H),
7.45-7.32 (m, 6H), 4.47 (s, 1H), 3.03-2.89 (m, 2H), 1.97 (dd,
J ) 17.0 and 1.8 Hz, 1H), 1.90 (dd, J ) 17.0 and 1.1 Hz, 1H),
1.70 (d, J ) 13.1 Hz, 1H), 1.34 (d, J ) 13.1 Hz, 1H), 1.05 (s,
3H), 1.03 (s, 3H), 1.01 (s, 9H), 0.77 (s, 3H), 0.50-0.42 (m, 1H);
13C NMR (CDCl3) δ 148.7, 135.9, 134.6, 134.2, 130.3, 129.2,
127.6, 127.5, 70.5, 48.7, 48.3, 48.0, 29.5, 28.1, 27.7, 24.8, 18.5,
6.5. Anal. Calcd for C26H36OSi: C, 79.53; H, 9.24. Found: C,
79.87; H, 9.56.
(1S*,6R*)-3-tert-Butyldiphenylsilylmethyl-6-ethylcy-
clohex-3-enol (36a): colorless oil; IR (neat, cm-1) 3580, 3470,
1550, 1470, 1105; 1H NMR (CDCl3) δ 7.69-7.58 (m, 4H), 7.48-
7.31 (m, 6H), 5.33-5.29 (m, 1H), 3.68-3.59 (m,1H), 2.11 (s,
2H), 1.98-1.85 (m, 2H), 1.76-1.62 (m, 2H), 1.36-1.11 (m, 4H)
1.06 (s, 9H), 0.82 (t, J ) 7.2 Hz, 3H); 13C NMR (CDCl3) δ 136.2,
134.7, 134.5, 130.9, 129.1, 127.4, 120.6, 67.6, 39.6, 38.9, 27.7,
26.7, 24.2, 20.5, 18.4, 11.6. Anal. Calcd for C25H34OSi: C, 79.31;
H, 9.05. Found: C, 79.67; H, 9.36.
(E)-(1R*,2R*,4R*)-5-tert-Butyldiphenylsilylmethylene-
2-ethyl-4-methylcyclohexanol (34a): colorless oil; IR (neat,
cm-1) 3500, 3450, 1610, 1430, 1105; 1H NMR (CDCl3) δ 7.80-
7.70 (m, 4H), 7.45-7.36 (m, 6H), 5.73 (s, 1H), 3.03-2.95 (m,
1H), 2.66-2.56 (m, 1H), 2.08 (dd, J ) 13.6 and 4.2 Hz, 1H),
1.94 (dd, J ) 13.6 and 8.8 Hz, 1H), 1.75-1.57 (m, 3H), 1.51-
1.29 (m, 3H), 1.21 (d, J ) 7.0 Hz, 3H), 1.01 (s, 9H), 0.87 (t, J
) 7.4 Hz, 3H); 13C NMR (CDCl3) δ 164.4, 135.9, 135.4, 129.0,
127.6, 127.5, 114.8, 73.7, 40.2, 39.8, 39.6, 35.3, 27.2, 24.1, 19.6,
18.0, 11.2. Anal. Calcd for C26H36OSi: C, 79.53; H, 9.24.
Found: C, 79.91; H, 9.51.
(1S*,6S*)-3-tert-Butyldiphenylsilylmethyl-6-ethylcy-
1
clohex-3-enol (36b): colorless oil; H NMR (CDCl3) δ 7.70-
7.61 (m, 4H), 7.45-7.30 (m, 6H), 5.20 (s, 1H), 3.30-3.20
(m, 1H), 2.09 (s, 2H), 1.93-1.82 (m, 2H), 1.71-1.49 (m, 4H),
1.30-1.19 (m, 2H), 1.06 (s, 9H), 0.80 (t, J ) 7.3 Hz, 3H); 13C
NMR (CDCl3) δ 136.2, 134.7, 131.6, 129.0, 127.4, 120.1, 70.7,
40.6, 39.3, 28.6, 27.7, 24.0, 20.5, 18.4, 11.1. Anal. Calcd for
C25H34OSi: C, 79.31; H, 9.05. Found: C, 79.62; H, 9.31.
(1S*,6R*)-3-tert-Butyldiphenylsilylmethyl-6-methylcy-
1
clohex-3-enol (37a): colorless oil; H NMR (CDCl3) δ 7.70-
(1S*,6R*)-3-tert-Butyldiphenylsilylmethyl-6-ethyl-4-
7.55 (m, 4H), 7.45-7.30 (m, 6H), 5.26 (s, 1H), 3.51-3.47 (m,
1H), 2.14 (d, J ) 15.2 Hz, 1H), 2.07 (d, J ) 15.2 Hz, 1H), 1.98-
1.83 (m, 2H), 1.71-1.52 (m, 4H), 1.05 (s, 9H), 0.80 (d, J ) 6.7
Hz, 3H); 13C NMR (CDCl3) δ 136.2, 134.7, 134.6, 130.8, 129.1,
127.4, 120.4, 69.6, 39.1, 31.8, 29.1, 27.6, 20.6, 18.4, 16.4. Anal.
Calcd for C24H32OSi: C, 79.06; H, 8.85. Found: C, 79.41; H,
9.14.
methylcyclohex-3-enol (34b): colorless oil; IR (neat, cm-1
)
3430, 1430, 1105; 1H NMR (CDCl3) δ 7.69-7.60 (m, 4H), 7.45-
7.27 (m, 6H), 3.67-3.58 (m, 1H), 2.20 (d, J ) 15.5 Hz, 1H),
2.12 (d, J ) 15.5 Hz, 1H), 2.10-2.03 (m, 1H), 1.84-1.62 (m,
4H), 1.41 (s, 3H), 1.35-1.18 (m, 3H), 1.11 (s, 9H), 0.83 (t, J )
7.3, 3H); 13C NMR (CDCl3) δ 136.1, 135.0, 134.4, 129.0, 127.2,
123.7, 123.1, 67.5, 40.6, 39.8, 33.0, 27.5, 24.3, 19.6, 18.3, 16.4,
11.5. Anal. Calcd for C26H36OSi: C, 79.53; H, 9.24. Found: C,
79.87; H, 9.56.
(1S*,6S*)-3-tert-Butyldiphenylsilylmethyl-6-methylcy-
1
clohex-3-enol (37b): colorless oil; H NMR (CDCl3) δ 7.69-
7.59 (m, 4H), 7.45-7.32 (m, 6H), 5.16 (s, 1H), 3.17-3.09
(m, 1H), 2.08 (s, 2H), 2.09-1.99 (m, 2H), 1.94-1.82 (m, 2H),
1.65-1.52 (m, 2H), 1.06 (s, 9H), 0.83 (d, J ) 6.5 Hz, 3H); 13C
NMR (CDCl3) δ 136.2, 134.8, 134.7, 132.0, 129.0, 127.4, 120.1,
72.5, 39.5, 34.5, 32.3, 27.7, 20.5, 18.4, 17.3. Anal. Calcd for
C24H32OSi: C, 79.06; H, 8.85. Found: C, 79.37; H, 9.09.
3-tert-Butyldiphenylsilylmethylcyclohex-3-enol (38):
colorless oil; IR (neat, cm-1) 3350, 1430, 1100; 1H NMR (CDCl3)
δ 7.75-7.65 (m, 4H), 7.45-7.31 (m, 6H), 5.18 (s, 1H), 3.71-
3.63 (m, 1H), 2.24-2.14 (m, 1H), 2.15 (s, 2H), 1.91-1.68
(m, 4H), 1.56-1.47 (m, 1H), 1.39-1.27 (m, 1H), 1.11 (s, 9H);
13C NMR (CDCl3) δ 136.2, 134.9, 134,8, 134.7, 129.1, 127.4,
118.0, 66.4, 34.4, 30.9, 29.1, 27.7, 20.8, 18.4. Anal. Calcd for
C23H30OSi: C, 78.80; H, 8.63. Found: C, 79.15; H, 8.96.
3-tert-Butyldiphenylsilylmethyl-4-methylcyclohex-3-
enol (39): colorless oil; 1H NMR (CDCl3) δ 7.65-7.55 (m, 4H),
7.45-7.30 (m, 6H), 3.69-3.61 (m, 1H), 2.16 (d, J ) 15.0 Hz,
1H), 2.08 (d, J ) 15.0 Hz, 1H), 2.06-1.99 (m, 1H), 1.85-1.63
(m, 5H), 1.53-1.44 (m, 1H), 1.33 (s, 3H), 1.09 (s, 9H); 13C
NMR (CDCl3) δ 136.2, 134.9, 134.8, 129.0, 127.2, 126.6, 121.2,
66.9, 40.5, 31.0, 29.9, 27.6, 19.8, 18.3, 16.6. Anal. Calcd for
C24H32OSi: C, 79.06; H, 8.85. Found: C, 79.41; H, 9.11.
(1S*,6S*)-3-tert-Butyldiphenylsilylmethyl-6-ethyl-4-
methylcyclohex-3-enol (34c): colorless oil; IR (neat, cm-1
)
3370, 1430, 1105; 1H NMR (CDCl3) δ 7.70-7.61 (m, 4H), 7.45-
7.27 (m, 6H), 3.22-3.11 (m, 1H), 2.12 (s, 2H), 2.06-1.90 (m,
2H), 1.76-1.66 (m, 1H), 1.54-1.44 (m, 2H), 1.33 (s, 3H), 1.31-
1.20 (m, 3H), 1.11 (s, 9H), 0.83 (t, J ) 7.3 Hz, 3H); 13C NMR
(CDCl3) δ 136.2, 135.0, 129.0, 127.4, 127.1, 123.9, 123.3, 70.9,
41.7, 40.5, 35.3, 27.6, 24.1, 19.2, 18.3, 16.6, 11.0.
(E)-(1R*,2R*,4S*)-5-tert-Butyldiphenylsilylmethylene-
1
2-methyl-4-isopropylcyclohexanol (35a): colorless oil; H
NMR (CDCl3) δ 7.80-7.65 (m, 4H), 7.45-7.30 (m, 6H), 5.81
(s, 1H), 3.48-3.39 (m, 1H), 2.10 (dd, J ) 15.2 and 3.2 Hz, 1H),
2.07-1.97 (m, 2H), 1.89-1.77 (m, 1H), 1.71-1.49 (m, 2H),
1.11-1.07 (m, 2H), 1.02 (s, 9H), 0.99 (d, J ) 6.5 Hz, 6H), 0.85
(d, J ) 6.5 Hz, H); 13C NMR (CDCl3) δ 161.2, 136.2, 135.1,
129.0, 127.6, 120.1, 71.8, 56.3, 39.0, 31.0, 30.5, 27.3, 26.8, 22.2,
21.0, 18.1, 17.6. Anal. Calcd for C27H38OSi: C, 79.74; H, 9.42.
Found: C, 80.11; H, 9.71.
(1S*,6R*)-3-tert-Butyldiphenylsilylmethyl-4-isopropyl-
6-methylcyclohex-3-enol (35b): colorless oil; IR (neat, cm-1
)
3430, 1610, 1427, 1105; 1H NMR (CDCl3) δ 7.82-7.65 (m, 4H),
7.45-7.29 (m, 6H), 3.51-3.45 (m, 1H), 2.62 (sept, J ) 6.8 Hz,
1H), 2.15 (d, J ) 14.3 Hz, 1H), 2.05 (d, J ) 14.3 Hz, 1H), 1.95-
1.69 (m, 4H), 1.54-1.43 (m, 2H), 1.09 (s, 9H), 0.98 (d, J ) 6.3
Acknowledgment. We thank the Ministry of Sci-
ence and Technology of Spain (BQU2003-03035) and the
“Junta de Castilla y Leo´n” (VA050/2004) for financial
support.
Hz, 3H), 0.83 (d, J ) 6.8 Hz, 3H), 0.71 (d, J ) 6.8 Hz, 3H); 13
C
NMR (CDCl3) δ 136.3,134.9, 134.5, 132.2, 129.1, 127.2, 121.5,
69.4, 40.3, 32.6, 29.4, 27.6, 26.7, 20.0, 19.7, 18.3, 16.3, 15.4.
Anal. Calcd for C27H38OSi: C, 79.74; H, 9.42. Found: C, 80.07;
H, 9.76.
Supporting Information Available: Crystallographic
data collection parameters for compound 33a. This material
is available free of charge via the Internet at http://pubs.acs.org.
(1S*,6S*)-3-tert-Butyldiphenylsilylmethyl-4-isopropyl-
6-methylcyclohex-3-enol (35c): colorless oil; IR (neat, cm-1
)
3420, 1425, 1105; 1H NMR (CDCl3) δ 7.65-7.55 (m, 4H), 7.45-
JO051868G
10752 J. Org. Chem., Vol. 70, No. 26, 2005