Highly diastereoselective intramolecular allylation reactions of mixed silyl-substituted acetals

Article abstract of DOI:10.1021/jo9517048

The reaction of preformed mixed acetals derived from (α-hydroxyalkyl)dimethylallylsilane with a number of aromatic and aliphatic aldehydes in the presence of Lewis acids results in a highly diastereoselective intramolecular allylation reaction. The reaction proceeds through a cyclic synclinal S_E′ addition of the allylsilane to an intermediate oxocarbenium ion. The reaction occurs exclusively by an intramolecular process as determined by means of a cross-over experiment. The relative stereochemistry was determined by the conversion of one of the allylation products to a known (stereodefined) aldol-type product. A greater degree of diastereoselectivity is obtained by in-situ formation of an oxocarbenium ion from (α-hydroxyhexyl)dimethylallylsilane and an aldehyde in the presence of boron trifluoride etherate. The diastereoselectivity of the in-situ allylation reaction typically exceeds 100:1 in favor of the syn adduct. However, reactions with electron rich aryl aldehydes resulted in a diminished degree of diastereoselectivity. The initial product of the in-situ reaction is an unstable silyl fluoride which is readily hydrolyzed to a silanol derivative upon reaction with methanolic potassium hydroxide. The overall yield of the two-step process is greater than 80%. A method for the synthesis of more highly substituted (α-alkoxyalkyl)dimethylallylsilanes by allyl anion displacement of methoxide from silicon is also described. The methyl siloxane derivatives were obtained by ozonolytic cleavage of an unsubstituted allyl group in methanol.

Full text of DOI:10.1021/jo9517048

J . Org. Chem. 1996, 61, 2441-2453
2441
High ly Dia ster eoselective In tr a m olecu la r Allyla tion Rea ction s of
Mixed Silyl-Su bstitu ted Aceta ls
Russell J . Linderman* and Kangyi Chen
Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204
Received September 18, 1995X
The reaction of preformed mixed acetals derived from (R-hydroxyalkyl)dimethylallylsilane with a
number of aromatic and aliphatic aldehydes in the presence of Lewis acids results in a highly
diastereoselective intramolecular allylation reaction. The reaction proceeds through a cyclic
synclinal SE′ addition of the allylsilane to an intermediate oxocarbenium ion. The reaction occurs
exclusively by an intramolecular process as determined by means of a cross-over experiment. The
relative stereochemistry was determined by the conversion of one of the allylation products to a
known (stereodefined) aldol-type product. A greater degree of diastereoselectivity is obtained by
in-situ formation of an oxocarbenium ion from (R-hydroxyhexyl)dimethylallylsilane and an aldehyde
in the presence of boron trifluoride etherate. The diastereoselectivity of the in-situ allylation reaction
typically exceeds 100:1 in favor of the syn adduct. However, reactions with electron rich aryl
aldehydes resulted in a diminished degree of diastereoselectivity. The initial product of the in-
situ reaction is an unstable silyl fluoride which is readily hydrolyzed to a silanol derivative upon
reaction with methanolic potassium hydroxide. The overall yield of the two-step process is greater
than 80%. A method for the synthesis of more highly substituted (R-alkoxyalkyl)dimethylallylsilanes
by allyl anion displacement of methoxide from silicon is also described. The methyl siloxane
derivatives were obtained by ozonolytic cleavage of an unsubstituted allyl group in methanol.
In tr od u ction
“endocyclic” within a closed cyclic transition state for
intramolecular delivery of the allyl group.3
Allylsilanes comprise a very useful class of function-
alized nucleophilic reagents that have enjoyed a consid-
erable degree of application in synthesis. A number of
intermolecular and intramolecular regiospecific and ste-
reoselective reactions have been reported.1 In addition
to the synthetic applications of allylsilanes, a number of
investigations have probed the mechanism of reaction
with acetals and carbonyl compounds.2 In general,
current and previous work has focused on transforma-
tions in which the silyl reagent undergoes an acyclic
antiperiplanar SE′ reaction with an electrophile. The
antiperiplanar reaction manifold is also commonly ob-
served in intramolecular reactions of allylsilanes which
incorporate a trimethylsilyl-substituted allyl group. There
are few examples in the literature in which the silicon
atom serves as a template to bring the allyl moiety and
the electrophile together in an intramolecular reaction.
To our knowledge, there are only two examples of an
allylsilane addition reaction in which the silicon atom is
Earlier work from our laboratory revealed that (R-
alkoxyalkyl)silyl- and -stannyl-substituted mixed acetals
undergo diastereoselective nucleophilic addition reactions
with a number of enol ethers and ketene silyl acetals.4
The relative stereochemistry (across the ether linkage)
of the aldol type products was determined to be anti as
illustrated in Figure 1. As part of a program designed
to fully investigate the synthetic utility of (R-alkoxyalkyl)-
silanes, we sought to develop a stereocomplementary
process which would lead to products bearing a syn
stereochemical relationship of the substituents across the
ether linkage. In this paper, we describe details of the
study of an intramolecular allyl transfer reaction via an
(R-alkoxyalkyl)dimethylallylsilane. We also note that the
silane derivative is a bis-functionalized reagent that
serves to bring together both the electrophilic and nu-
cleophilic reactive centers via an “endocyclic” silicon
template.
Syn th esis of Allylsila n e Su bstitu ted Mixed
Aceta ls
* To whom correspondence should be addressed. Phone: (919) 515-
3616. Fax: (919) 515-5079. E-mail: linderma@chemdept.chem.ncsu.edu.
X Abstract published in Advance ACS Abstracts, March 15, 1996.
(1) (a) Fleming, I. Chem. Soc. Rev. 1981, 10, 83. (b) Yamamoto, Y.;
Asao, N. Chem. Rev. 1993, 93, 2207. (c) Majetich, G. In Organic
Synthesis: Theory and Application; Hudlicky, T., Ed.; J AI Press:
Greenwich, CT, 1989; Vol. 1, p 173. (d) Fleming, I.; Dunogues, J .;
Smithers, R. Org. React. 1989, 37, 57.
(2) For examples of mechanistic studies, see: (a) Hayashi, T.;
Konishi, M.; Ito, H.; Kumada, M. J . Am. Chem. Soc. 1982, 104, 4962.
(b) Hayashi, T.; Konishi, M.; Kumada, M. J . Am. Chem. Soc. 1982,
104, 4963. (c) Yamamoto, T.; Yatagai, H.; Ishihara, Y.; Maeda, N.;
Maruyama, K. Tetrahedron 1984, 40, 2239. (d) Heathcock, C. H.;
Kiyooka, S.; Blumenkopf, T. A. J . Org. Chem. 1984, 49, 4214. (e)
Denmark, S. E.; Weber, E. J .; Wilson, T. M.; Willson, T. M. Tetrahedron
1989, 45, 1053. (f) Panek, J . S.; Cirillo, P. F. J . Org. Chem. 1993, 58,
999. (g) Denmark, S. E.; Almstead, N. G. J . Org. Chem. 1994, 59, 5130.
(h) For an example of a syn SE′ addition from a bis-silyl-substituted
species, see: Wetter, H.; Scherer, P.; Schweizer, W. B. Helv. Chim.
Acta 1979, 1985. (i) Mayr, H.; Gorath, G. J . Am. Chem. Soc. 1995,
117, 7862.
The (R-hydroxyalkyl)allyldimethylsilanes 1a -c were
easily prepared by the reverse Brook methodology de-
veloped earlier in this group, Scheme 1.5 Initial conden-
sation of the aldehyde with (tributylstannyl)lithium
followed by O-silylation of the alcohol with commercially
available chlorodimethylallylsilane provided the inter-
mediate (tributylstannyl)silyl ether. Rearrangement of
silicon from oxygen to carbon was then accomplished by
treatment of the stannane with an excess of butyllithium.
(3) (a) Reetz, M. T.; J ung, A.; Bolm, C. Tetrahedron 1988, 44, 3889.
(b) Uyeo, S.; Itani, H. Tetrahedron Lett. 1991, 32, 2143.
(4) (a) Linderman, R. J .; Anklekar, T. V. J . Org. Chem. 1992, 57,
5078. (b) Linderman, R. J .; Viviani, F. G.; Kwochka, W. R. Tetrahedron
Lett. 1992, 33, 3571.
(5) Linderman, R. J .; Ghannam, A. J . Am. Chem. Soc. 1990, 112,
1392.
0022-3263/96/1961-2441$12.00/0 © 1996 American Chemical Society

2442 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
and co-workers.9 It is interesting to note in this example
that no competing cleavage of the R-acetoxyalkyl group
from silicon was observed. The silyl fluoride 5 could be
obtained in 80-87% yield by Kugelrohr distillation.
Unfortunately, the electrophilic cleavage of the phenyl
group could not be accomplished on an acetal-protected
derivative of 3 without concomitant loss of the acetal
protecting group. Reaction of the silyl fluoride 5 with
methallyllithium or Grignard reagents did not result in
the anticipated free (R-hydroxyhexyl)dimethylmethal-
lylsilane. The reaction led instead to a diastereomeric
mixture of the unstable dimeric product 6 (tentatively
identified by NMR data) along with the expected bisho-
moallylic ether 7 resulting from addition of the anion to
the acetate, Scheme 3. We were unable to find reaction
conditions that would allow for the conversion of the
dimeric product 6 to the desired addition product in
reasonable yield. Interestingly, treatment of the dimer
6 with excess methyllithium resulted in cleavage of the
silyl ether as well as loss of the methallyl group, provid-
ing only the known trimethylsilyl derivative 8.5
Given the fact that alkoxy groups are readily displaced
from silicon by reaction with alkyllithio species,7 we then
explored an alternative route to synthesize a methoxy
substituted (R-alkoxyalkyl)dimethylsilane. We antici-
pated that ozonolysis of allyl silane 2a or 2b in methanol
would result in an unstable R-trialkylsilyl aldehyde.10
Methanolysis of the R-silyl aldehyde or rearrangement
to a silyl enol ether prior to methanolysis could then
result in the silyl ether product. In the event, ozonolysis
of acetal 2a or 2b in methanol provided the silyl methyl
ether derivatives 9a and 9b, respectively, in good yields
(1). It must be pointed out that the ozonolysis reaction
F igu r e 1. Diastereoselective nucleophilic addition reactions
to (R-alkoxyalkyl)trimethylsilanes.
Sch em e 1a
a
Reagents: (a) Bu3SnLi, THF -78 °C; (b) CH2CHCH2Si(CH3)2Cl,
(c) 3 equiv of BuLi, THF, -78 °C; (d) 1-chloroethyl methyl ether,
iPr2NEt, CH2Cl2.
Conversion of the dimethylallylsilyl substituted carbinol
to the mixed acetal was straightforward via reaction with
an R-chloro ether in the presence of Hunig’s base.5 The
mixed silyl-substituted acetals were each obtained as a
1:1 mixture of diastereoisomers.
The synthesis of mixed acetals containing more highly
substituted allyl silanes was then pursued. Unfortu-
nately, chlorodimethyl-substituted allylsilanes which
could be employed in the reverse Brook rearrangement
method are not readily available. A number of ap-
proaches to the synthesis of bifunctional silanes have
been reported from dichlorodialkylsilanes6 or (dialkyl-
amino)alkoxydialkylsilane7 derivatives; however, earlier
studies in our group had indicated that nucleophilic
addition of R-alkoxy anions to silyl halides or silyl ethers
was not a synthetically useful process.5 Our initial
attempts to solve this problem involved chemoselective
functionalization of dimethylphenyl(R-hydroxyhexyl)si-
lane 3. The requisite starting material was prepared by
the reverse Brook rearrangement method rather than
direct addition of the dimethylphenylsilyl anion8 to
hexanal, Scheme 2. In our hands this three-step proce-
dure provided very good overall yields of the product and
obviated the need to prepare the silyl anion. In addition,
we have found that the reverse Brook approach for the
synthesis of (R-hydroxyalkyl)silanes can be easily carried
out on relatively large scales (g4 g). The hydroxy group
of the silane was then protected as the acetate 4 in
excellent yield. Chemoselective removal of the phenyl
group of 4 was then effected by reaction with tetrafluo-
roboric acid under the conditions reported by Fleming
of the silyl acetal can be tempermental. Extended
ozonolysis reaction times can result in loss of the acetal
protecting group with subsequent oxidation of the (R-
hydroxyhexyl)dimethylsilane derivative to hexanoic acid.11
Overoxidation can be minimized by monitoring the
ozonolysis reaction for loss of starting material. Longer
reaction times are required for larger scale reactions (>2
g) which can lead to an increase in the extent of
overoxidation. The methoxy ether 9 is somewhat un-
stable to chromatography on silica gel and is best purified
by rapidly passing the crude ozonolysis reaction mixture
through a short plug of silica gel. The fairly unstable
silanol acetal 10 may be obtained as a byproduct by
hydrolysis on the column. Nevertheless, silyl ether 9a
or 9b can be reproducibly obtained in 70-80% yield.
Substituted allylsilanes were then prepared by dis-
placement of the methoxy group of 9 by allyllithio regents
which were in turn generated by transmetalation of the
corresponding allylstannane; see Table 1. The stannanes
(6) Dihalodialkylsilanes have been employed in the preparation of
a wide variety of bisfunctionalized silane derivatives. The “temporary
silicon connection” methodology of Stork provides an example of this
approach. See, for example: (a) Stork, G.; Suh, H. S.; Kim, G. J . Am.
Chem. Soc. 1991, 113, 7054. (b) Stork, G.; Kim, G. J . Am. Chem. 1992,
114, 1087. (c) Matsumoto, Y.; Ohno, A.; Hayashi, T. Organometallics
1993, 12, 4051.
(7) Aminosilanes are also useful intermediates in the synthesis of
bisfunctionalized silanes. See: (a) Stork, G.; Keitz, P. F. Tetrahedron
Lett. 1989, 30, 6981. (b) Tamao, K.; Kawachi, A.; Ito, Y. Organome-
tallics 1993, 12, 580.
(8) (a) George, M. V.; Peterson, D. J .; Gilman, H. J . Am. Chem. Soc.
1960, 82, 403. (b) Fleming, I.; Newton, T. W. J . Chem. Soc., Perkins
Trans. 1 1984, 1805.
(9) Fleming, I.; Henning, R.; Plaut, H. J . Chem. Soc., Chem.
Commun. 1984, 29.
(10) For a recent report on the isolation of a stable R-trialkylsilyl
substituted aldehyde, see: Duhamel, L.; Gralak, J .; Bouyanzer, A. J .
Chem. Soc., Chem. Commun. 1993, 1763.
(11) Linderman, R. J .; Chen, K. Y. Tetrahedron Lett. 1992, 33, 6767.

Allylation Reactions of Mixed Silyl-Substituted Acetals
Sch em e 2a
J . Org. Chem., Vol. 61, No. 7, 1996 2443
a
Reagents: (a) Bu3SnLi, THF, -78 °C; (b) PhMe2SiCl, iPr2NEt, DMAP, CH2Cl2, rt; (c) 3 equiv of nBuLi, THF, -78 °C (69%); (d) Ac2O,
py, DMAP, CH2Cl2, rt (91%); (e) 2 equiv of HBF4‚Et2O, CH2Cl2, rt (87%).
Sch em e 3
Sch em e 4a
Ta ble 1. Syn th esis of Su bstitu ted Allylsila n es
a
Reagents: (a) Me3SiOTf, CH2Cl2, -78 °C (70%); (b) 8 equiv
of MeLi, THF, 0 °C (91%).
unstable allyl transfer product 16 in good yield after
chromatography, Scheme 4. Verification of the structural
assignment was realized upon reaction of the trimeth-
ylsilyl ether derivative 16 with an excess of methyl-
lithium, providing the trimethylsilyl-substituted deriva-
tive 17 as a 34:1 diastereomeric mixture. The derived
trimethylsilyl substituted allylation product was the
same as that obtained by intermolecular reaction of the
corresponding trimethylsilyl substituted mixed acetal 18
with allyltrimethylsilane,4a (2), except that the diaster-
a
Each acetal was obtained as a 1:1 mixture of diastereomers.
Isolated yields after chromatography. c Silane 12 was obtained
as an approximately 2:1 ratio of E:Z isomers. Silane 14 was
b
d
obtained as an approximately 6:1 ratio of E:Z isomers.
were prepared from the appropriate allyl halide and
tributyltin chloride using Barbier reaction conditions.12
Tributylcrotylstannane prepared in this fashion from
3-chloro-1-butene was isolated as an E/ Z mixture of
alkenes. The best yields of the allylsilane derivatives
11-15 were obtained from reaction of 9a or 9b with 3
equiv of the allyllithium reagent.
eomeric ratio of the product, as determined by capillary
GC, was reversed. Significantly, the intermolecular
allylation reaction only produced 17 as a 1:5 (syn:anti)
mixture of diastereomers. The syn- and anti-isomers of
17 were also readily distinguished by 13C NMR spectral
data. The relative stereochemistry of syn-17 obtained
from the intramolecular reaction (Scheme 4) was then
verified by chemical conversion to the aldol product 20
as shown in Scheme 5. Ozonolysis of the allyl group
followed by Grignard addition to the aldehyde provided
alcohol 19 in 56% overall yield. Swern oxidation13
provided the ketone 20 in very good yield. Comparison
of ketone 20 with that derived from the known anti
selective Mukaiyama aldol reaction4a clearly indicated
that the intramolecular allylation product 16 bears the
In tr a m olecu la r Allyla tion Rea ction s
Our initial investigations of the allylsilane-function-
alized mixed acetals focused on an intramolecular ally-
lation reaction using mixed acetal 2a . On the basis of
our earlier work on aldol reactions of trimethylsilyl-
substituted mixed acetals, we first chose to examine
reactions catalyzed by trimethylsilyl triflate. Reaction
of the mixed acetal 2a with 1.1 equiv of trimethylsilyl
triflate at -78 °C resulted in the somewhat hydrolytically
(12) Keck, G. E.; Enholm, E. J .; Yates, J . B.; Wiley, M. R. Tetrahe-
dron 1985, 41, 4079.
(13) Mancuso, A. J .; Brownfair, D. S.; Swern, D. J . Org. Chem. 1979,
44, 4148.

2444 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
Sch em e 5a
Sch em e 6a
a
a
Reagents: (a) 0.1 equiv of TMSOTf, CH2Cl2, -78 °C; (b) SiO2/
Reagents: (a) O3, then Me2S, (b) PhMgCl (56%), (c) Swern
H2O (observed incomplete hydrolysis under these conditions).
(89%).
Ta ble 2. In tr a m olecu la r Allyla tion Rea ction s of
Su bstitu ted Allyl Sila n es
were treated under the relatively strong basic conditions
of 10% KOH in MeOH/THF to effect complete conversion
to the relatively stable silanol. The silanols could be
readily purified by flash chromatography. Symmetric
siloxanes or (trimethylsilyl)siloxanes (such as 16) were
converted to the silanol in >95% yield in all cases
examined. A number of milder basic hydrolysis condi-
tions were examined but found not to be as effective. Over
time the silanols are found to dehydrate to once again
produce the corresponding symmetric siloxane.
silane siloxane
silanol yieldc
C
entry
R1
R2
R3
Aa
B
selectivityb
(%)
1
2
3
4
5
6
C5H11
iPr
C5H11 CH3
C5H11
C5H11
iPr
H
H
H
H
H
2a
2b
11
3
34:1
38:1
25:1
1.6:1d
6.4:1d
37:1
26
27
28
29
30
31
85
69
70
78
78
71
21
22
23
24
25
H
H
CH3
CH3 12
Ph
H
14
15
a
b
Structures shown in Figure 2. Diastereoselectivity (syn:anti)
of the initially formed trimethylsilyl ether of the silanol determined
by capillary GC analysis of the crude reaction mixture. c Isolated
The initial experiments using mixed acetal 2a were
carried out at room temperature; however, the substi-
tuted allyl species 11-15 were found to be more reactive,
and the allylation reaction was therefore carried out at
-78 °C. Acetal 2a also provides the silanol 26 in good
yield upon treatment with trimethylsilyl triflate at -78
°C (Table 2, entry 1). Both â-substituted silanes 12 and
14 provide the product resulting from γ-allylation, sil-
anols 29 and 30, respectively, as anticipated. The
selectivities of the allylation reaction of silanes 12 and
14 were much more difficult to assess due to the fact that
the starting silanes were diastereomeric mixtures at the
acetal carbon as well as an E/ Z isomeric mixture at the
double bond. In the case of silane 12, all four isomers
were resolved by GC, providing assessment of the acetal
diastereomeric mixture as 1:1.2 and the alkene isomeric
ratio as 1.6:1. GC analysis of the (trimethylsilyl)siloxane
derivative of silanol 29 indicated two diastereomers in a
ratio of 1.6:1, reflecting the ratio of double bond isomers
in the starting material. A comparison of spectral data
from the series of compounds produced by this study
indicated that the ratio was due to the relative stereo-
chemistry of the R3 (see Figure 2) group and the vicinal
methyl substituent, rather than the relative stereochem-
istry across the ether linkage. Similarly, silane 14 was
produced as a roughly 6:1 ratio of alkene isomers and a
1:1 ratio of diastereomers at the acetal carbon (relative
to the silyl-substituted carbon). The allylation product
was isolated as a 6.4:1 mixture of isomers, again due to
the relative stereochemistry of R3 and the vicinal methyl
group. The actual diastereoselectivity across the ether
linkage could not be accurately determined for either 29
d
overall yield of the silanol. The diastereoselectivity reported
reflects the ratio of isomers determined by the stereochemistry of
R3 relative to the vicinal methyl group. Diastereoselectivity across
the ether linkage could not be accurately determined but is
estimated as >20:1 by NMR data.
F igu r e 2. Structures of substituted allylsilanes A, siloxanes
B, and silanols C.
syn stereochemical relationship for the substituents
across the ether linkage.
The yields and selectivities of the intramolecular
allylation reaction of mixed acetals 2a , 2b, 11, 12, 14,
and 15 are given in Table 2. The structures of the mixed
acetal silane A, siloxane B, and silanol C are shown in
Figure 2. Each acetal provided the allylation product
with an excellent degree of diastereoselectivity (as de-
termined by capillary GC analysis of the initial (tri-
methylsilyl)siloxane derivative B). Reactions using less
than stoichiometric amounts of trimethylsilyl triflate led
to substantial amounts of symmetric siloxane derivatives,
such as 32, Scheme 6. The symmetric siloxanes were
difficult to purify due to partial hydrolysis upon silica
gel column chromatography. The spectral data (1H and
13C NMR) for the symmetric siloxane were virtually
identical to that for the corresponding silanol with the
only distinction being observation of an absorption for a
free OH in the IR spectrum of the silanol. Symmetric
siloxanes can also be obtained in reactions using 1.1 equiv
of trimethylsilyl triflate if the reaction mixture is allowed
to stir for >2 h at room temperature. To prevent this
problematic side reaction, the crude allylation products
1
or 30, but is estimated as >20:1 from H NMR spectral
data. Unfortunately, attempts to obtain a single alkene
isomer of silane 12 or 14 for use in the allylation reaction
were not successful.
The reaction of silane 13 with trimethylsilyl triflate
was unique in that the reaction did not provide the
expected allyl transfer product, but rather the cyclic
silane 33 in 76% yield, Scheme 7. Significantly, 33 was
isolated as a single isomer in which all of the substituents
are equatorial. The diaxial orientation of Ha and Hb
(Scheme 7) was readily apparent from the observed

Allylation Reactions of Mixed Silyl-Substituted Acetals
J . Org. Chem., Vol. 61, No. 7, 1996 2445
Sch em e 7a
product is obtained with greater than 100:1 selectivity
for the syn isomer in nearly all of the cases examined.
The diastereoselectivity of the allylation reaction was
determined by GC analysis of the crude silyl fluoride
product 34. The high degree of diastereoselectivity is also
reflected in the 19F NMR of the fluoride. For example,
the 19F NMR spectrum of 34c revealed only a singlet at
-164 ppm. The relatively unstable silyl fluoride partially
hydrolyzes upon attempted column chromatography on
silica gel. Similar to the trimethylsilyl ethers (siloxanes)
discussed above, neutral pH aqueous hydrolysis of the
fluoride leads to a mixture of silanol and siloxane dimers
which is difficult to separate. Clean hydrolysis of the silyl
fluoride was then routinely accomplished with 10%
potassium hydroxide in MeOH/THF in the same manner
as discussed above for the siloxanes. The silanols 35
obtained in this fashion are remarkably stable and easily
chromatographed on silica gel. The yields of isolated
silanols given in Table 3 are for the overall two-step
process (allyl transfer and hydrolysis). The silanols tail
upon attempted GC analysis, preventing an accurate
determination of diastereomeric ratios by this analytical
method at this stage; however, NMR data (1H and 13C)
of the silanols 35a -l indicate a single diastereomeric
product in good agreement with the GC data from the
silyl fluorides.
a
Reagents: (a) 1.1 equiv of TMSOTf, CH2Cl2, -78 °C.
Sch em e 8a
a
Reagents: (a) RCHO, 0.5 equiv of BF3Et2O, CH2Cl2, rt; (b)
10% KOH MeOH/THF.
Trimethylsilyl triflate is not as effective a catalyst in
the reaction of the free alcohol 1a with aldehydes as in
the reactions of preformed acetals with this Lewis acid.
For example, the reaction of benzaldehyde and silane 1a
catalyzed by trimethylsilyl triflate at room temperature
produced silanol 35e in 35-40% yield (after hydrolysis
of the initially formed (trimethylsilyl)siloxane). In con-
trast, boron trifluoride etherate consistently provided
silanol 35e in yields over 85%. Other Lewis acids such
as titanium tetrachloride or tin tetrachloride did not
cleanly provide the allylation products from reactions of
1a with aldehydes. A slight excess of the silane 1a is
required to optimize the yield of the allylation product
35. The examples shown in Table 3 were obtained using
1.4 equiv of silane to aldehyde. The yield of the allyl
transfer product is also dependent on the reaction time
and temperature. Reactions using silane 1a at room
temperature for periods longer than 10 min resulted in
a significant reduction in the yield of the adduct. How-
ever, reaction times using the hydroxysilane at lower
temperatures (<-40 °C) were much longer (>2 h for
completion) and, therefore, did not provide any advantage
over the shorter reaction time at room temperature.
For a direct comparison of the diastereoselectivity of
the intramolecular allyl transfer reaction with an inter-
molecular allylation reaction, the in-situ reaction of
allyltrimethylsilane, hexanal, and (1-hydroxyhexyl)tri-
methylsilane (8) was carried out (3). In this reaction,
Ta ble 3. In tr a m olecu la r Allyla tion Rea ction of RCHO
w ith 1a
yieldb
(%)
entry
aldehyde R
CH3
selectivitya SiF
SiOH
1
2
>120:1
118:1
113:1
114:1
>120:1
>120:1
>120:1
>120:1
>120:1
>120:1
>120:1
>120:1
24:1
34a
35a (26)
49
81
82
85
93
77
75
72
85
80
73
72
78
34
CH(CH3)2
34b 35b
34c 35c
34d 35d
34e
34f
34g 35g
34h 35h
34i
34j
34k 35k
34l 35l
34m 35m
34n 35n
3
4
5
6
7
8
9
10
11
12
13
14
15
nC5H11
cyclo-C6H11
C6H5
4-PhC6H4
2-naphthaldehyde
2-BrC6H4
4-NO2C6H4
4-CF3C6H4
3-CF3C6H4
2-CF3C6H4
4-MeC6H4
2,4,6-(CH3)3C6H2
4-MeOC6H4
35e
35f
35i
35j
4:1
c
a
Diastereoselectivity (syn:anti) of the silyl fluoride 34, deter-
mined by capillary GC analysis of the crude reaction mixture.
Isolated overall yield of the silanol 35 from the aldehyde. c No
b
silyl containing allylation product was obtained. 4-(Diallylmethy-
l)anisole 38 was isolated in 31% yield with 48% recovered
4-methoxybenzaldehyde.
vicinal coupling constant of 3 Hz. Additional NOE and
2D NMR data served to confirm the stereochemical
assignment.
The intramolecular allylation reaction does not require
the prior synthesis of a mixed acetal. The direct combi-
nation of (R-hydroxyhexyl)dimethylallylsilane (1a ), an
aldehyde, and boron trifluoride etherate also results in
the desired allylation product in very good yield, Scheme
8 and Table 3. In this case, the initial product of the
reaction is the silyl fluoride 34. More significantly, the
diastereoselectivity of the reaction is enhanced over that
observed in reactions with preformed mixed acetals, from
roughly a >20:1 mixture to a >100:1 mixture. As in the
reactions using preformed mixed acetals, we believe that
the free alcohol forms an intermediate oxocarbenium ion
which then undergoes intramolecular allylation in very
good yield with excellent selectivity; see the mechanism
discussion below. As shown in Table 3 , the allylation
the intermolecular allylation product 36 was obtained in
good yield, but with only 1:3.4 selectivity. In contrast to
the intermolecular reaction, note the extent of selectivity
realized for the intramolecular process, Table 3, entry 3,
of 113:1. Given the data presented within this study, we

2446 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
Sch em e 9
Sch em e 10a
a
Reagents: (a) 0.5 equiv of BF3‚Et2O, CH2Cl2, -78 to -20 °C;
(b) 10% KOH, MeOH/THF.
Sch em e 11a
have assigned the relative stereochemistry of 36 derived
from the intermolecular allylation process anti as shown
in (3). In a related reaction, Marko and co-workers have
realized diastereoselectivity as high as 10:1 for intermo-
lecular allylation reactions employing mixed acetals
derived in-situ from aryl-substituted alcohols.14 There
are other examples of high degrees of diastereoselection
in reactions of acyclic acetals15 and trimethylallylsilane;
however, there are no other examples of addition reac-
tions to silyl-substituted mixed acetals such as those
reported here. The observed diastereoselectivity for this
intramolecular allylation process provides an example of
one of the highest degrees of “acyclic” 1,3-asymmetric
induction reported to date.16
The reactions of silane 1a and substituted aromatic
aldehydes reveal that electron-rich aryl aldehydes result
in silanols 35 with diminished diastereoselectivity rela-
tive to silanols obtained from reaction with electron poor
aryl aldehydes. The substitution of a methyl group for
hydrogen in the para position dramatically reduces the
diastereoselectivity of the reaction (compare Table 3,
entries 5 and 13) from >120:1 to 24:1. The incorporation
of three alkyl groups on the aromatic ring further reduce
the selectivity to 4:1, see Table 3, entry 14. Anisaldehyde
does not result in the formation of the silyl fluoride
product at all, but rather undergoes a second allylation
reaction to form 38, presumably through a quinone
methide intermediate 37 formed by Lewis acid catalyzed
expulsion of the benzylic oxygen present in the initial
allylation product, Scheme 9.
a
Reagents: (a) c-C6H11CHO, 0.5 equiv of BF3‚OEt2, CH2Cl2,
-78 °C; (b) 10% KOH, MeOH/THF.
product 40 in similar yield (50%), but as a 22:1 diaster-
eomeric mixture. Closer examination of the products
revealed that the observed ratio of isomers reflected a
mixture of cis- and trans-alkene isomers rather than a
diastereomeric mixture across the ether linkage. How-
ever, we cannot be certain of complete resolution of the
mixture and therefore can only presume that the actual
diastereoselectivity of the allylation reaction in this
particular example is as high as that observed for
cinnamaldehyde (>100:1).
The intramolecular allylation reaction was also exam-
ined for a phenyl-substituted silane 1c and cyclohexyl-
carboxaldehyde. In this case the normal reaction con-
ditions did not result in a product that contained the
dimethylsilanol moiety, but rather the benzyl ether 41,
Scheme 11.
Cleavage of C-Si bonds of benzylic silanes under
strongly basic conditions is a well-known process.18
Indeed, if the allylation reaction of 1c is repeated without
the secondary base treatment step, the sensitive silyl
fluoride 42 was obtained as a single diastereomer (>120:1
selectivity). Submission of the fluoride to methanolic
potassium hydroxide then resulted in the benzyl ether
41 in very good yield.
Attempted intramolecular allylation reaction of silane
1a or 1b with ketones, such as acetophenone and cyclo-
hexanone, did not result in any allylation products. The
ketone and silane were recovered from the reaction
mixture. This result is not unexpected given the lower
propensity of a ketone to form a hemiketal with the free
alcohol (and therefore an oxocarbenium ion) under the
reaction conditions employed.
The reaction of silane 1a with two unsaturated alde-
hydes has also been examined. Reaction with cinnama-
ldehyde provided the 1,2-addition product 39 in reason-
able yield (55%), Scheme 10.
The possible 1,4-addition product was not observed in
the reaction mixture, but given the attenuated yield of
the reaction relative to the other examples discussed
above, this possible reaction pathway cannot be com-
pletely ruled out. Intermolecular reactions of unsatur-
ated aldehyde acetals with allyltrimethylsilane result in
products derived from multiple allylations by 1,2- and
1,4-additions.17 The somewhat sensitive diene 40 was
obtained as a 100:1 ratio of diastereomers. In contrast,
crotonaldehyde also provided the 1,2-addition reaction
Mech a n ism of th e Rea ction
(14) Mekhalfia, A.; Marko, I. E. Tetrahedron Lett. 1991, 32, 4779.
(15) (a) Imwinkelreid, R.; Seebach, D. Angew. Chem., Int. Ed. Engl.
1985, 24, 591. (b) Mukaiyama, T.; Ohshima, M.; Muyishi, N. Chem.
Lett. 1987, 1121.
Given the fact that each silyl-substituted mixed acetal
initially exists as a 1:1 mixture of diastereomers, but
produces a product with typically >25:1 stereoselectivity,
(16) Hoffman, R. W. Chem. Rev. 1989, 89, 1841.
(17) Allylsilane additions to unsaturated aldehydes result in mix-
tures of 1,2- and 1,4-addition products as well as diaddition products;
see: Hosomi, A.; Endo, M.; Sakurai, H. Chem. Lett. 1978, 499.
(18) Linderman, R. J .; Ghannam, A.; Badejo, I. J . Org. Chem. 1991,
56, 5213.

Allylation Reactions of Mixed Silyl-Substituted Acetals
J . Org. Chem., Vol. 61, No. 7, 1996 2447
Sch em e 12a
F igu r e 3. Cyclic SE′ synclinal transition state.
implies that the reaction proceeds through an oxocarbe-
nium ion intermediate. This mechanism is consistent
with our previous data on aldol reactions of silyl-
substituted mixed acetals4 and is also supported by recent
mechanistic studies of Lewis acid-catalyzed nucleophilic
addition reactions to acyclic acetals not containing sili-
con.19 Trialkylallylsilanes generally react via an anti SE′
mechanism through either an antiperiplanar or synclinal
acyclic transition state.1,2 Reactions through a syn SE′
mechanism are typically disfavored for stereoelectronic
reasons.2g,h Reactions of allylsilanes through cyclic (or
closed) transition states are fairly uncommon and are
typically only observed for pentacoordinate allylsilicate20
species or allylsilanes bearing inductively withdrawing
substituents such as allyltrifluorosilane.21 Intramolecu-
lar allyl transfer reactions proceeding by an anti SE′
mechanism are well known for the construction of car-
bocyclic and heterocyclic systems.1c The stereoselectivity
of the intramolecular allylation reactions can be very
high, such as the tetrahydrofuran synthesis reported by
Mohr.22 Marko and co-workers have examined an in-
tramolecular Sakurai reaction of functionalized allylsi-
lanes that leads to tetrahydropyran derivatives.23 Lee
and co-workers have also studied reactions of function-
alized allylsilanes that react via in-situ formation of an
oxocarbenium ion.24 However, these reactions are dis-
tinct from the intramolecular allyl transfer reaction
reported herein in that the silicon in the previous studies
is present as a trimethylsilyl moiety and is “exocyclic” to
the forming ring in the transition state.
A reasonable transition state for the intramolecular
process is depicted in Figure 3 in which a synclinal SE′
attack of the allylsilane occurs on the intermediate
oxocarbenium ion through a seven-membered cyclic
transition state. Note in this case that the silicon atom
is “endocyclic” within the cyclic transition state. This
constraint apparently precludes the adoption of an an-
tiperiplanar approach of the electrophile to the allylsi-
lane. Indeed, examination of molecular models indicates
that an antiperiplanar SE′ approach is not favorable.
Reetz and co-workers have reported a novel intramolecu-
lar allyl transfer reaction to provide syn-1,3-diols.3a In
this example, a dimethylallylsilyl moiety is used to
derivatize an aldol product with subsequent intramo-
a
Reagents: (a) 1.1 equiv of TMSOTf, CH2Cl2, -78 °C; (b) 10%
KOH MeOH/THF; (c) 5 equiv of Me3SiCl, 10 equiv of Et3N, CH2Cl2,
rt.
lecular delivery of the allyl group via a cyclic 10-
membered ring induced by chelation to titanium. The
seven-membered ring intermediate, shown in Figure 3,
provides for a possible dual role for silicon in that the
C-Si σ bond R to the oxocarbenium ion can adopt an
antiperiplanar geometry to the developing π* orbital of
the oxocarbenium ion.4a This orientation will facilitate
ionization of the acetal via a stereoelectronic effect
similar to hyperconjugative stabilization of a â-carboca-
tion.25 The allylic C-Si σ bond is also situated anti (or
nearly so) to the CdC π-system for the “normal” mode of
reaction (stereoelectronic control) for the allylsilane. The
cyclic nature of the transition state is strongly supported
not only by the data from a cross-over reaction (described
below), but also by the results of the reactions of
substituted silanes 12 and 14. An intermolecular anti-
periplanar mechanism would be expected to give a high
degree of stereoselection independent of the double bond
geometry, whereas the stereoselectivity of a closed or
cyclic transition state allylsilane reaction is known to be
dependent on the alkene geometry1,20,21 as is observed in
our study.
The question of whether the reaction mechanism for
the allylation process was solely an intramolecular
pathway or potentially also involved a degree of inter-
molecular reaction was then probed in detail by the
design of a cross-over experiment, Scheme 12. An
equimolar amount of acetals 11 and 2b was combined
with trimethylsilyl triflate at -78 °C. GC analysis of the
crude reaction mixture revealed siloxanes 21 and 22 and
dimeric siloxanes as discussed above (Scheme 6). To
remove the dimeric siloxane byproducts, the crude reac-
tion mixture was hydrolyzed with KOH and the silanols
thus obtained were reprotected as the (trimethylsilyl)-
siloxanes using an excess of trimethylsilyl chloride.26
Interestingly, trimethylsilyl chloride does not promote
dimeric siloxane formation as noted previously for tri-
methylsilyl triflate. Upon careful GC analysis of the
crude reaction mixture, only the products of intramo-
lecular allyl transfer (siloxanes 21 and 22: diastereose-
lectivity >25:1 in each case) were observed. The products
(19) For recent mechanistic investigations into the reaction of
nonsilyl-substituted acyclic acetals, see: Sammakia, T.; Smith, R. S.
J . Am. Chem. Soc. 1994, 116, 7915 and references therein.
(20) (a) Hosomi, A.; Kohra, S.; Ogata, K.; Yanagi, T.; Tominaga, Y.
J . Org. Chem. 1990, 55, 2415. (b) Hosomi, A.; Kohra, S.; Tominaga, Y.
J . Chem. Soc., Chem. Commun. 1987, 1517.
(21) (a) Kira, M.; Hino, T.; Sakurai, H. Tetrahedron Lett. 1989, 30,
1099. (b) Sato, K.; Kira, M.; Sakurai, H. J . Am. Chem. Soc. 1989, 111,
6429.
(22) (a) Mohr, P. Tetrahedron Lett. 1993, 34, 6251. (b) For
a
diastereoselective synthesis of tetrahydrofurans via an intermolecular
allylsilane addition, see: Panek, J . S.; Beresis, R. J . Org. Chem. 1993,
58, 809.
(23) (a) Marko, I. E.; Bailey, M.; Murphy, F.; Declercq, J .-P.; Tinant,
B.; Feneau-Dupont, J .; Krief, A.; Dumont, W. Synlett 1995, 123. (b)
Marko, I. E.; Bayston, D. J . Tetrahedron 1994, 50, 7141 and earlier
references therein.
(24) (a) Lee, T. V.; Ellis, K. L.; Richardson, K. A.; Visani, N.
Tetrahedron 1989, 45, 1167. (b) Lee, T. V.; Boucher, R. J .; Porter, J .
R.; Taylor, D. A. Tetrahedron 1988, 44, 4233.
(25) (a) For a review of hyperconjugation effects of silicon, see:
Lambert, J . B. Tetrahedron 1990, 46, 2677. For additional recent
studies, see: (b) Lambert, J . B.; Emblidge, R. W.; Malany, S. J . Am.
Chem. Soc. 1993, 115, 1317. (c) Yoshida, J .; Maekawa, T.; Murata, T.;
Matsunaga, S.; Isoe, S. J . Am. Chem. Soc. 1990, 112, 962. (d) Brook,
M. A.; Neuy, A. J . Org. Chem. 1990, 55, 3609.
(26) A control reaction indicated that the deprotection/reprotection
sequence did not effect the diastereomeric ratio of the product.

2448 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
formation positions the silyl group such that delivery of
an internal nucleophile occurs from the same face of the
oxocarbenium ion as the silyl substituent. The resulting
intramolecular allyl transfer reaction results in one of
the most diastereoselective allylsilane reactions for acy-
clic acetals ever reported. Further work will explore the
potential for extension of this approach for intramolecular
delivery of other nucleophiles from bis-functionalized
silanes.
F igu r e 4. Transition state for formation of 33.
Exp er im en ta l Section
Gen er a l. All reagents were purchased from Aldrich, unless
otherwise noted, and were purified prior to use. Amines and
trialkylsilyl chlorides were distilled from CaH2. Methanol was
refluxed for 2 h over magnesium turnings and then distilled
and stored over 3A molecular sieves. Alkyllithium reagents
were titrated in ether with 2-propanol using 1,10-phenanthro-
line as an indicator. Tetrahydrofuran (THF) was freshly
distilled from sodium-benzophenone. Methylene chloride was
distilled from phosphorous pentoxide. Unless specifically
stated, all reactions were performed in flame-dried glassware
under an argon atmosphere. Infrared spectra were recorded
on a FTIR spectrophotometer. 1H and 13C NMR spectra were
recorded on a 300 MHz spectrometer, and chemical shifts are
reported relative to TMS. 19F NMR spectra were recorded on
a 300 MHz spectrometer and chemical shifts are reported
relative to CFCl3. Capillary gas chromatographic analyses
were carried out on a 30 m SE-30 fused silica capillary column
using a temperature ramp program of 100 °C for 10 min, rate
increase of 10 °C/min to 250 °C and a final temperature of
250 °C for 5 min. Flash chromatography was performed on
silica gel 60, 230-400 mesh ASTM, obtained from American
Scientific Products or Baxter Scientific. Elemental analyses
were carried out by Atlantic Microlab, Inc., Atlanta, GA.
A. Syn th esis of r-Hyd r oxy Sila n es by th e Rever se
Br ook Rea r r a n gem en t. Known compounds 1a and 3 were
prepared as described in ref 5 in 74% and 89% yields,
respectively. Compounds 1b and 1c were also prepared by
the published procedure for 1a .
F igu r e 5. Possible intermediates in the allylation of electron
rich aromatic aldehydes.
21 and 22 were isolated by careful column chromatog-
raphy in good overall yields.27
The reaction of silane 13 to form the cyclic silane 33
(Scheme 7) is interesting in that reaction at the â-position
of an allyl silane is very uncommon.1 Akiba and co-
workers have reported alkylation at the â-carbon in
reactions of (γ,γ-dimethylallyl)trimethylsilane.28 In the
case of silane 13, a six-membered ring transition state
can be adopted in which all of the substituents, with the
exception of a methyl group on silicon, are equatorial;
see Figure 4. The ring closure results in formation of a
tertiary carbocation which may not be significantly
higher in energy than the cyclic â-silyl carbocation formed
in the intramolecular allyl transfer process. The end
result is competitive ring closure via the smaller ring (six
vs seven) with ultimate loss of a proton to provide the
isopropenyl group.
1-[Dim e t h yl(3-p r op e n -1-yl)silyl]-2-m e t h ylp r op a n -1-
1
ol, 1b (63%): H NMR (CDCl3) δ 0.04 (s, 3 H), 0.05 (s, 3 H),
0.92 (d, 3 H, J ) 5 Hz), 0.95 (d, 3 H, J ) 5 Hz), 1.40 (s, 1 H),
1.60 (t, 2 H, J ) 7 Hz), 1.83 (m, 1 H), 3.12 (t, 1 H, J ) 5 Hz),
4.83 (m, 2 H), 5.79 (m, 1 H); 13C NMR (CDCl3) ppm -4.97,
-4.49, 18.97, 20.36, 22.20, 31.96, 71.02, 113.03, 134.94; IR
(neat) (cm-1) 3470, 3100, 1640, 1470, 1250, 835, 820. Anal.
Calcd for C9H20OSi: C, 62.73; H, 11.79. Found: C, 62.62; H,
11.65.
[Dim et h yl(3-p r op en -1-yl)silyl]p h en ylm et h a n ol, 1c
(51%): 1H NMR (CDCl3) δ -0.01 (s, 3 H), 0.01 (s, 3 H), 1.61 (t,
2 H, J ) 7 Hz), 1.81 (s, 1 H), 4.60 (s, 1 H), 4.89 (m, 2 H), 5.79
(m, 1 H), 7.19-7.35 (m, 5 H); 13C NMR (CDCl3) ppm -6.49,
-6.03, 20.72, 69.50, 113.51, 124.95, 125.95, 125.88, 128.18,
134.54, 143.85; IR (neat) (cm-1) 3440, 3180, 1630, 1490, 1250,
840, 700. Anal. Calcd for C12H18OSi: C, 69.84; H, 8.79.
Found: C, 69.56; H, 8.74.
Stabilization of the forming intermediate benzylic
cation by the aromatic ring also provides a reasonable
explanation for the lower degrees of selectivity observed
for electron-rich aryl aldehydes. A quinone methide
intermediate 44 can arise as the reactive species rather
than the oxocarbenium ion 43, Figure 5. The quinone
methide resonance form must not provide the same
degree of stereochemical control in the transition state
for the intramolecular allyl transfer reaction as that
enjoyed by the oxocarbenium ion. One must also note
that the possibility of intermolecular reactions in ally-
lation of the aryl aldehydes cannot be completely ruled
out from the data in hand.
B. Gen er a l P r oced u r e for Mixed Aceta l F or m a tion .
A solution of (R-hydroxyalkyl)silane (10 mmol), diisopropyl-
ethylamine (5.23 mL, 30 mmol), and 4-(dimethylamino)-
pyridine (12 mg, 0.1 mmol) in 25 mL of CH2Cl2 was cooled to
0 °C (ice/water bath). Methyl methoxymethyl chloride (1.57
g, 20 mmol) was then added dropwise via syringe. The
reaction mixture was allowed to warm to room temperature
and stirred for 24 h. The mixture was diluted with 100 mL of
petroleum ether and washed successively with 0.1 N hydro-
chloric acid (2 × 30 mL), water (30 mL), saturated sodium
bicarbonate (30 mL), and saturated aqueous sodium chloride
solution (30 mL). The organic phase was dried over anhydrous
sodium sulfate, and the solvent was removed under reduced
pressure. The crude product was purified by flash chroma-
tography on silica gel by a gradient elution using 100%
hexanes or a 1%, 2%, and 3% diethyl ether/hexanes system.
Met h oxyet h yl 1-[d im et h yl(3-p r op en -1-yl)silyl]h exyl
Con clu sion s
In summary, we have described a novel method for
stereochemical complementarity in nucleophilic addition
reactions to silyl-substituted mixed acetals. In intermo-
lecular nucleophilic addition reactions the silyl group
serves to block one face of the oxocarbenium ion, directing
addition to the face of the oxocarbenium ion opposite the
silyl group. In the intramolecular variant, a stereoelec-
tronic effect of silicon to accentuate oxocarbenium ion
(27) The silica gel must be deactivated by treatment with triethy-
lamine (2%)/hexane prior to chromatography of 28 or 29 (see Experi-
mental Section).
(28) Wada, M.; Shigehisa, T.; Kitani, H.; Akiba, K.-Y. Tetrahedron
Lett. 1983, 24, 1715.
1
eth er , 2a (87%): GC tR 17.00 and 17.12 min (1:1); H NMR

Allylation Reactions of Mixed Silyl-Substituted Acetals
J . Org. Chem., Vol. 61, No. 7, 1996 2449
(CDCl3) δ -0.01 (s, 3 H), 0.01 (s, 3 H), 0.84 (t, 3 H, J ) 6 Hz),
1.19-1.58 (m, 13 H), 3.24 (d, 3 H, J ) 12 Hz), 3.33 (t, 1 H, J
) 6 Hz), 4.54 (q, 1 H, J ) 5 Hz), 4.80 (m, 2 H), 5.74 (m, 1 H);
13C NMR (CDCl3) ppm -5.01, 13.99, 19.71, 21.75, 22.52, 26.75,
31.47, 32.12, 51.76, 70.41, 101.40, 113.13, 134.61; IR (neat)
(cm-1) 3100, 1635, 1460, 1250, 840. Anal. Calcd for C14H30O2-
Si: C, 65.06; H, 11.70. Found: C, 65.17; H, 11.67.
Com p ou n d 6: 1H NMR (CDCl3) δ 0.04-0.13 (m, 12H), 0.8-
1.8 (m, 25H), 2.08 (d, 1H, J ) 6 Hz), 2.17 (d, 1H, J ) 6 Hz),
3.25 (m, 1H), 4.00 (s, 1H), 4.71 (s, 1H), 4.78 (s, 1H); 13C NMR
(CDCl3) ppm -4.52, -3.62, -3.56, -2.84, 14.06, 22.62, 23.81,
26.40, 26.50, 31.80, 32.67, 32.83, 48.15, 65.34, 67.37, 112.87,
143.18; IR (neat) (cm-1) 3460, 3080, 1250, 1080, 835.
1
2,4,6-Tr im eth ylh ep ta -1,6-d ien -4-ol, 7: H NMR (CDCl3)
δ 1.16 (s, 3H), 1.83 (s, 6H), 2.19 (dd, 4H, J ) 13 and 23 Hz),
4.73 (s, 2H), 4.91 (s, 4H); 13C NMR (CDCl3) ppm 24.95, 27.05,
50.15, 71.96, 114.87, 142.89; IR (neat) (cm-1) 3460, 3080, 1250,
1095, 890.
Meth oxyeth yl 1-[d im eth yl(3-p r op en -1-yl)silyl]-2-m e-
th ylp r op yl eth er , 2b (94%): GC tR 12.82 and 13.22 min (1:
1); 1H NMR (CDCl3) δ 0.05 (s, 3 H), 0.07 (s, 3 H), 0.90 (d, 3 H,
J ) 7 Hz), 0.95 (d, 3 H, J ) 7 Hz), 1.26 (d, 3 H, J ) 6 Hz), 1.62
(m, 2H), 1.96 (m, 1 H), 3.25 (t, 1 H, J ) 4 Hz), 3.26 (s, 3 H),
4.57 (q, 1 H, J ) 6 Hz), 4.83 (m, 2 H), 5.78 (m, 1 H); 13C NMR
(CDCl3) ppm -3.59, -3.39, 19.16, 19.58, 20.84, 22.94, 31.34,
52.09, 76.55, 101.95, 113.19, 134.87; IR (neat) (cm-1) 3180,
1625, 1240, 830. Anal. Calcd for C12H26O2Si: C, 62.54; H,
11.37. Found: C, 62.66; H, 11.36.
C. Attem p ted Con ver sion of Dim eth ylp h en ylsila n e to
Su bstitu ted Allylsila n es. Syn th esis of 4. A solution of 3
(2.36 g, 10 mmol), pyridine (4.0 mL, 50 mmol), and 4-(di-
methylamino)pyridine (12 mg, 0.1 mmol) in 25 mL of CH2Cl2
was cooled to 0 °C (ice/water bath). Acetic anhydride (2.0 mL,
21 mmol) was then added dropwise via syringe. The reaction
mixture was allowed to warm to room temperature and stirred
for 12 h. The mixture was diluted with 100 mL of CH2Cl2 and
washed sequentially with 0.1 N HCl (2 × 30 mL), water (30
mL), and saturated aqueous sodium chloride solution (30 mL).
The organic phase was dried over anhydrous sodium sulfate,
and the solvent was removed under reduced pressure. The
crude product was purified by flash chromatography on silica
gel by a gradient elution using a 1%, 2%, 3%, and 5% diethyl
ether/hexanes system.
D. Gen er a l P r oced u r e for Ozon olysis of Sila n es 2a
a n d 2b. A solution of silane 2a or 2b in methanol (1 mmol/
20 mL) was cooled to -78 °C. Ozone was passed through the
solution until a blue coloration persisted. Excess ozone was
purged from the reaction with argon, and dimethyl sulfide (2
mL) was then added. The reaction mixture was allowed to
warm to room temperature, stirred for 6 h, and then concen-
trated under reduced pressure. The residue was taken up in
ether (100 mL), the solution dried over anhydrous magnesium
sulfate, and the solvent removed under reduced pressure. The
crude product was purified by rapid filtration of a hexane
solution through a plug of silica gel.
Meth oxyeth yl 1-(d im eth ylm eth oxysilyl)h exyl eth er ,
1
9a (70%): GC tR 14.85 and 14.97 min (1:1); H NMR (CDCl3)
δ 0.01 (s, 3 H), 0.12 (s, 3 H), 0.85 (t, 3 H, J ) 7 Hz), 1.22-1.60
(m, 11 H), 3.25 (s, 3 H), 3.33 (t, 1 H, J ) 6 Hz), 3.42 (s, 3 H),
4.59 (m, 1 H); 13C NMR (CDCl3) ppm -4.17, -3.98, 13.99,
19.81, 22.49, 26.33, 31.47, 32.18, 50.67, 51.57, 69.47, 101.23;
IR (neat) (cm-1) 1250, 1090, 830. Anal. Calcd for C12H28O3-
Si: C, 58.02; H, 11.36. Found: C, 58.17; H, 11.34.
Meth oxyeth yl 1-(d im eth ylm eth oxysilyl)-2-m eth ylp r o-
p yl eth er , 9b (68%): GC tR 7.81 and 8.38 min (1:1); 1H NMR
(CDCl3) δ 0.16 (s, 3H), 0.17 (s, 3H), 0.98 (m, 6H), 1.25 (d, J )
6 Hz, 3H), 2.02 (m, 1H), 3.25 (d, J ) 5 Hz, 1H), 3.32 (s, 3H),
3.45 (s, 3H), 4.59 (m, 1H); 13C NMR (CDCl3) ppm -2.62, -2.46,
19.52, 19.74, 20.45, 30.79, 50.60, 51.96, 76.42, 101.91; IR (neat)
(cm-1) 1245, 1140, 1080, 995, 830. Anal. Calcd for C10H24O3-
Si: C, 54.50; H, 10.98. Found: C, 54.21; H, 10.78.
1-(Dim eth ylp h en ylsilyl)h exyl a ceta te, 4 (91%): 1H NMR
(CDCl3) δ 0.22 (s, 3 H), 0.24 (s, 3 H), 0.74 (t, 3 H, J ) 7 Hz),
1.05-1.60 (m, 8 H), 1.90 (s, 3 H), 4.88 (dd, 1 H, J ) 4 Hz, J ′
) 13 Hz), 7.26 (m, 3 H), 7.43 (m, 2 H); 13C NMR (CDCl3) ppm
-5.36, -5.07, 13.93, 20.91, 22.43, 26.59, 30.79, 31.41, 68.37,
127.73, 129.31, 133.97, 135.97, 171.06; IR (neat) (cm-1) 3070,
3050, 1730, 1240, 830, 690. Anal. Calcd for C16H26O2Si: C,
69.01; H, 9.41. Found: C, 68.90; H, 9.37.
E. Gen er a l P r oced u r e for th e Syn th esis of Su bsti-
tu ted Allylsila n es. Butyllithium (2.6 M in hexanes, 1.2 mL,
3.0 mmol) was added dropwise via syringe to a solution of a
substituted allyltributylstannane (3 mmol) in 5 mL of THF at
-78 °C. The reaction mixture was stirred for 20 min at -78
°C to provide a bright yellow or red solution. Silane 9a or 9b
(0.32 mmol) in 1 mL of THF was then added dropwise at -78
°C. The reaction mixture was allowed to warm to 0 °C and
stirred for 2 h. The reaction mixture was then quenched by
the addition of 2 mL of water. The layers were separated, and
the aqueous phase was extracted with ether (2 × 30 mL). The
combined organic phases were then washed with water (20
mL) and dried over anhydrous sodium sulfate, and the solvents
were removed under reduced pressure. The crude product was
purified by flash chromatography using 2% petroleum ether/
hexane as eluent.
Syn th esis of 5. A sample of 85% HBF4‚OEt2 (0.3 mL, 1.8
mmol) was added via syringe to a solution of 4 (230 mg, 0.827
mmol) in 5 mL of CH2Cl2 at room temperature. The reaction
mixture was stirred for 2 h and then quenched by the addition
of 5 mL of water. The layers were separated and the aqueous
phase extracted with ether (3 × 20 mL). The combined organic
phases were dried over anhydrous sodium sulfate and the
solvents removed under reduced pressure to provide the crude
fluorosilane in 90-95% yield. (GC and NMR data showed that
the Si-F intermediate was pure enough to carry out the next
reaction.) Crude product was purified by vacuum distillation,
50-55 °C/4 mmHg, to provide a colorless liquid in 85% yield.
1-(Dim eth ylflu or osilyl)-1-h exyl a ceta te, 5: 1H NMR
(CDCl3) δ 0.23 (d, 3 H, J ) 7 Hz), 0.25 (d, 3 H, J ) 8 Hz), 0.86
(t, 3 H, J ) 7 Hz), 1.25-1.65 (m, 8 H), 2.04 (s, 3 H), 4.26 (m, 1
H); 13C NMR (CDCl3) ppm -2.91 (-3.13), -1.94 (-2.13), 13.96,
20.45, 22.43, 26.43, 29.95, 31.47, 69.31 (69.05), 172.26; 19F
NMR (CDCl3) -158.64; IR (neat) (cm-1) 1730, 1710, 1255, 840,
795.
Syn th esis of 6 a n d 7. Compound 5 (160 mg, 0.73 mmol)
was dissolved in 15 mL of THF, and Mg metal (583 mg, 24
mmol) and a crystal of iodine were added. A THF solution
(10 mL) of methallyl chloride (0.8 mL, 8.1 mmol) was then
added dropwise at room temperature over a period of ap-
proximately 30 min. After being stirred for 90 min at room
temperature, the reaction mixture was quenched by the
addition of saturated aqueous ammonium chloride (10 mL).
The reaction mixture was diluted with ether (100 mL) and
washed sequentially with saturated aqueous sodium bisulfate
(20 mL), saturated aqueous sodium bicarbonate (20 mL), water
(20 mL), and saturated aqueous sodium chloride (20 mL). The
organic phase was then dried over anhydrous magnesium
sulfate, and the solvents were removed under reduced pres-
sure. Purification of the crude product mixture provided 6 and
7 in 25% and 99% yield, respectively.
Meth oxyeth yl 1-[d im eth yl(2-m eth yl-3-p r op en -1-yl)si-
lyl]h exyl eth er , 11 (65%): GC tR 18.48 and 18.58 min (1:1);
1H NMR (CDCl3) δ (mixture of diastereomers) 0.06 (m, 6 H),
0.86 (t, 3 H, J ) 7 Hz), 1.20-1.85 (m, 16 H), 3.24 (s, 3 H), 3.34
(t, 1 H, J ) 6 Hz), 4.48 (s, 1 H), 4.58 (s, 1 H), 4.60 (m, 1 H); 13
C
NMR (CDCl3) ppm (major diastereomer) -4.30, -4.17, 14.02,
19.55, 22.55, 25.30, 26.88, 31.57, 32.12, 32.25, 51.67, 69.89,
100.59, 108.54, 143.56; IR (neat) (cm-1) 3080, 1630, 1250, 840,
730. Anal. Calcd for C15H32O2Si: C, 66.11; H, 11.84. Found:
C, 65.93; H, 11.78.
Met h oxyet h yl
1-[d im et h yl(4-b u t en -2-yl)silyl]h exyl
eth er , 12 (71%): GC tR (a) 18.26 and 18.36 min (1:1.2), (b)
1
18.64 and 18.75 min (1.2:1); a:b ) 1:1.6; H NMR (CDCl3) δ
(mixture of diastereomers) 0.15 (m, 6 H), 0.87 (t, 3 H, J ) 7
Hz), 1.20-1.65 (m, 14 H), 3.27 (m, 4 H), 4.56 (m, 1 H), 5.33
(m, 1 H); 13C NMR (CDCl3) ppm (major diastereomer) -4.88,
-4.78, 13.99, 17.97, 19.52, 22.52, 26.69, 26.82, 31.54, 32.22,
51.76, 70.73, 100.46, 121.72, 126.05; IR (neat) (cm-1) 1450,
1090. 837, 734. Anal. Calcd for C15H32O2Si: C, 66.11; H,
11.84. Found: C, 66.28; H, 11.79.

2450 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
Meth oxyeth yl 1-[d im eth yl(2-m eth yl-4-bu ten -2-yl)silyl]-
h exyl eth er , 13 (75%): GC tR 19.45 and 19.55 min (1:1); H
ppm 0.19, 0.87, 1.97, 19.74, 19.90, 20.49, 30.79, 41.49, 75.48,
77.29, 116.42, 135.68; IR (neat) (cm-1) 3070, 1250, 1040, 830,
740.
1
NMR (CDCl3) δ (mixture of diastereomers) 0.02 (s, 3 H), 0.03
(s, 3 H), 0.89 (t, 3 H, J ) 7 Hz), 1.20-1.75 (m, 19 H), 3.29 (s,
3 H), 3.33 (m, 1 H), 4.54 (q, 0.5 H, J ) 5 Hz), 4.64 (q, 0.5 H, J
) 5 Hz), 5.14 (m, 1 H); 13C NMR (CDCl3) ppm (major
diastereomer) -4.65, 14.06, 15.63, 17.64, 19.78, 22.55, 25.69,
26.72, 31.60, 32.28, 51.73, 70.86, 100.52, 119.52, 129.02; IR
(neat) (cm-1) 1456, 1090, 836, 773, 720. Anal. Calcd for
4-[[1-(H yd r oxyd im et h ylsilyl)-2-m et h ylp r op yl]oxy]-1-
1
p en ten e, 27 (69%): H NMR (CDCl3) δ 0.16 (s, 3 H), 0.17 (s,
3 H), 0.94 (t, 6 H, J ) 7 Hz), 1.12 (d, 3 H, J ) 7 Hz), 1.97 (m,
1 H), 2.05 (s, 1 H), 2.10 (m, 1 H), 2.27 (m, 1 H), 2.88 (d, 1 H,
J ) 6 Hz), 3.46 (m, 1 H), 5.08 (m, 2 H), 5.80 (m, 1 H); 13C
NMR (CDCl3) ppm -0.26, 0.36, 19.78, 20.13, 20.42, 30.50,
41.30, 75.97, 76.55, 117.13, 135.68; IR (neat) (cm-1) 3420, 3075,
1646, 861, 735. Anal. Calcd for C11H24O2Si: C, 61.06; H,
11.18. Found: C, 61.17; H, 11.15.
C
16H34O2Si: C, 67.07; H, 11.96. Found: C, 67.16; H, 11.93.
Meth oxyeth yl 1-[d im eth yl(1-p h en yl-3-p r op en -1-yl)si-
lyl]h exyl eth er , 14 (75%): GC tR 25.55 and 25.64 min (1:1);
1H NMR (CDCl3) δ (mixture of diastereomers) 0.03 (s, 3 H),
0.04 (s, 3 H), 0.83 (t, 3 H, J ) 7 Hz), 1.15-1.65 (m, 11 H), 1.70
(m, 2 H), 3.20-3.28 (m, 3 H), 3.36 (m, 1 H), 4.55 (m, 1 H),
6.20 (m, 2 H), 7.07-7.26 (m, 5 H); 13C NMR (CDCl3) ppm
(major diastereomer) -4.78, -4.72, 14.02, 19.74, 21.06, 22.52,
26.66, 31.47, 32.18, 51.54, 69.44, 100.49, 125.40, 126.12,
127.54, 128.34, 138.23, 146.41; IR (neat) (cm-1) 3060, 3025,
1642, 1090, 832, 695. Anal. Calcd for C18H34O2Si: C, 71.80;
H, 10.24. Found: C, 71.76; H, 10.20.
4-[[1-[[(Dim eth yltr im eth ylsilyl)oxy]silyl]h exyl]oxy]-2-
m eth yl-1-p en ten e, 22: GC tR 18.81 and 18.93 min (1:25); 1H
NMR (CDCl3) δ 0.05 (s, 9 H), 0.054 (s, 3 H), 0.08 (s, 3 H), 0.87
(t, 3 H, J ) 7 Hz), 1.06 (d, 3 H, J ) 6 Hz), 1.20-1.65 (m, 8 H),
1.69 (s, 3 H), 1.95 (m, 1 H), 2.33 (dd, 1 H, J ) 4 Hz, J ′ ) 13
Hz), 2.96 (t, 1 H, J ) 6 Hz), 3.50 (m, 1 H), 4.67 (s, 1 H), 4.72
(s, 1 H); 13C NMR (CDCl3) ppm -1.52, -0.61, 1.94, 14.09,
19.84, 22.62, 22.91, 26.69, 31.57, 32.25, 45.66, 71.54, 74.06,
112.38, 143.14; IR (neat) (cm-1) 3080, 1250, 1050, 830.
4-[[1-(Hydr oxydim eth ylsilyl)h exyl]oxy]-2-m eth yl-1-pen -
ten e, 28 (70%): 1H NMR (CDCl3) δ 0.13 (s, 6 H), 0.87 (t, 3 H,
J ) 7 Hz), 1.11 (d, 3 H, J ) 6 Hz), 1.20-1.60 (m, 8 H), 1.73 (s,
3 H), 1.97 (dd, 1 H, J ) 7 Hz, J ′ ) 13 Hz), 2.17 (s, 1 H), 2.29
(dd, 1 H, J ) 7 Hz, J ′ ) 13 Hz), 3.00 (t, 1 H, J ) 7 Hz), 3.53
(m, 1 H), 4.74 (s, 1 H), 4.79 (s, 1 H); 13C NMR (CDCl3) ppm
-2.07, -1.29, 14.06, 20.74, 22.55, 23.01, 26.50, 31.76, 32.18,
45.79, 72.19, 75.00, 112.71, 143.95; IR (neat) (cm-1) 3423, 3053,
1265, 741. Anal. Calcd for C14H30O2Si: C, 65.06; H, 11.70.
Found: C, 64.87; H, 11.63.
Meth oxyeth yl 1-[d im eth yl(2-m eth yl-4-bu ten -2-yl)silyl]-
2-m eth ylp r op yl eth er , 15 (64%): GC tR 14.78 and 15.14 min
1
(1:1); H NMR (CDCl3) δ (mixture of diastereomers) 0.08 (s,
3H), 0.09 (s, 3H), 0.95 (m, 6H), 1.25 (d, 3H, J ) 6 Hz), 1.61 (d,
1H, J ) 1.5 Hz), 1.65 (d, 1H, J ) 5 Hz), 1.70 (s, 3H), 2.00 (m,
1H), 3.10 (d, 1H, J ) 5 Hz), 3.26 (s, 3H), 4.47 (m, 1H), 4.52
(m, 1H), 4.58 (m, 1H); 13C NMR (CDCl3) ppm -2.91, -2.84,
19.19, 19.65, 21.10, 25.40, 26.21, 31.08, 52.09, 77.16, 102.04,
108.73, 143.79; IR (neat) (cm-1) 3060, 1080, 990, 830.
F . Allylsila n e Rea ction s fr om P r efor m ed Mixed Ac-
eta ls. Trimethylsilyl triflate (44 µL, 0.23 mmol) was added
dropwise to a solution of silane A (0.2 mmol) in 5 mL of CH2-
Cl2 at -78 °C. The reaction mixture was stirred for 2 h at
-78 °C and then quenched by the addition of 2 mL of water.
The crude reaction mixture was washed with water (2 × 10
mL), and the combined aqueous layers were extracted with
petroleum ether (3 × 20 mL). The combined organic phases
were dried over anhydrous sodium sulfate, and the solvents
were removed under reduced pressure. The crude siloxane
product could be purified by flash chromatography on deacti-
vated silica gel (2% triethylamine/hexane) using petroleum
ether as eluent. Alternatively, the crude siloxane was directly
hydrolyzed to the silanol by dissolving the siloxane in a
mixture of 2 mL of 10% methanolic KOH, 2 mL of H2O, and 5
mL of THF and stirring overnight at room temperature. The
mixture was diluted with water (10 mL) and extracted with
ether (3 × 20 mL). The combined ether phases were dried
over anhydrous sodium sulfate, and the solvent was removed
under reduced pressure. The crude product was purified by
silica gel flash chromatography using 5% ether/petroleum
ether as eluent.
4-[[1-[[(Dim eth yltr im eth ylsilyl)oxy]silyl]h exyl]oxy]-3-
m eth yl-1-p en ten e, 23: GC tR 18.89 and 18.98 min (1.6:1); 1H
NMR (CDCl3) δ (mixture of diastereomers) 0.05 (s, 9 H), 0.06
(s, 3 H), 0.08 (s, 3 H). 0.87 (t, 3 H, J ) 7 Hz), 0.97 (m, 6 H),
1.20-1.55 (m, 8 H), 2.29 (m, 1 H), 2.97 (m, 1 H), 3.32 (m, 1
H), 4.96 (m, 2 H), 5.77 (m, 1 H); 13C NMR (CDCl3) ppm (major
diastereomer) -1.26, -0.42, 1.94, 13.80, 14.09, 16.29, 22.65,
26.53, 31.38, 32.31, 42.23, 71.70, 78.29, 113.77, 141.79; IR
(neat) (cm-1) 3089, 1253, 1059, 842.
4-[[1-(Hydr oxydim eth ylsilyl)h exyl]oxy]-3-m eth yl-1-pen -
ten e, 29 (78%): 1H NMR (CDCl3) δ (mixture of diastereomers)
0.14 (s, 6 H), 0.87 (t, 3 H, J ) 7 Hz), 0.97 (t, 3 H, J ) 7 Hz),
1.04 (d, 3 H, J ) 6 Hz), 1.20-1.60 (m, 8 H), 2.05 (s, 1 H), 2.13
(m, 1 H), 3.04 (q, 1 H, J ) 7 Hz), 3.33 (m, 1 H), 5.01 (d, 2 H,
J ) 15 Hz), 5.83 (m, 1 H); 13C NMR (CDCl3) ppm (major
diastereomer) -1.81, -1.10, 14.02, 15.35, 17.35, 22.55, 26.37,
31.38, 32.25, 42.43, 71.90, 79.10, 114.42, 141.24; IR (neat)
(cm-1) 3406, 3079, 1251, 1092, 837. Anal. Calcd for C14H30O2-
Si: C, 65.06; H, 11.70. Found: C, 65.00; H, 11.79.
4-[[1-[[(Dim eth yltr im eth ylsilyl)oxy]silyl]h exyl]oxy]-3-
p h en yl-1-p en ten e, 24: GC tR 24.47 and 24.76 min (6.4:1); 1H
NMR (CDCl3) δ -0.01 (s, 3 H), 0.03 (s, 3 H), 0.05 (s, 9 H), 0.86
(t, 3 H, J ) 7 Hz), 0.96 (d, 3 H, J ) 7 Hz), 1.20-1.55 (m, 8 H),
2.96 (t, 1 H, J ) 6 Hz), 3.24 (t, 1 H, J ) 7 Hz), 3.66 (m, 1 H),
4.93, (d, 1 H, J ) 18 Hz), 5.06 (d, 1 H, J ) 10 Hz), 5.26 (m, 1
H), 7.14-7.31 (m, 5 H); 13C NMR (CDCl3) ppm -1.26, -0.26,
1.97, 14.09, 18.71, 22.62, 26.59, 31.67, 32.25, 57.03, 71.86,
78.39, 115.97, 126.15, 128.15, 128.64, 139.52, 142.56; IR (neat)
(cm-1) 3054, 3018, 1452, 1249, 843, 694.
4-[[1-(Hydr oxydim eth ylsilyl)h exyl]oxy]-3-ph en yl-1-pen -
ten e, 30 (78%): 1H NMR (CDCl3) δ 0.05 (s, 6 H), 0.87 (t, 3 H,
J ) 7 Hz), 1.05 (d, 3 H, J ) 6 Hz), 1.20-1.55 (m, 8 H), 1.58 (s,
1 H), 2.97 (t, 1 H, J ) 7 Hz), 3.26 (dd, 1 H, J ) 7 Hz, J ′ ) 9
Hz), 3.67 (m, 1 H), 5.07 (d, 1 H, J ) 18 Hz), 5.16 (dd, 1 H, J )
1.5 Hz, J ′ ) 10 Hz), 6.28 (m, 1 H), 7.18-7.32 (m, 5 H); 13C
NMR (CDCl3) ppm -2.26, -1.26, 14.02, 19.10, 22.52, 26.43,
31.89, 32.15, 57.26, 72.67, 79.59, 116.94, 126.47, 128.31,
128.44, 138.78, 142.82; IR (neat) (cm-1) 3427, 3068, 3027, 1250,
836, 700. Anal. Calcd for C19H32O2Si: C, 71.19; H, 10.06.
Found: C, 71.47; H, 10.07.
4-[[[1-[(Dim eth yltr im eth ylsilyl)oxy]silyl]h exyl]oxy]-1-
p en ten e, 16: GC tR 17.80 and 17.97 min (1:34); 1H NMR
(CDCl3) δ 0.07-0.11 (m, 15 H), 0.89 (t, 3 H, J ) 6 Hz), 1.10 (d,
3 H, J ) 6 Hz), 1.20-1.60 (m, 8 H), 2.11 (m, 1 H), 2.29 (m, 1
H), 2.97 (t, 1 H, J ) 7 Hz), 3.43 (q, 1 H, J ) 6 Hz), 5.01 (m, 2
H), 5.78 (m, 1 H); 13C NMR (CDCl3) ppm -1.42, -0.61, 1.94,
14.09, 20.00, 22.65, 26.69, 31.47, 32.25, 41.55, 71.60, 75.03,
116.36, 135.68; IR (neat) (cm-1) 3080, 1640, 1250, 1060, 840.
4-[[1-(Hyd r oxyd im eth ylsilyl)h exyl]oxy]-1-p en ten e, 26
(85%): 1H NMR (CDCl3) δ 0.13 (s, 6 H), 0.86 (t, 3 H, J ) 7
Hz), 1.11 (d, 3 H, J ) 7 Hz), 1.20-1.55 (m, 8 H), 2.12 (m, 1 H),
2.26 (m, 2 H), 3.02 (t, 1 H, J ) 7 Hz), 3.45 (m, 1 H), 5.05 (m,
2 H), 5.81 (m, 1 H); 13C NMR (CDCl3) ppm -1.91, -1.33, 14.06,
20.49, 22.55, 26.53, 31.47, 32.22, 41.33, 71.90, 75.68, 117.00,
135.74; IR (neat) (cm-1) 3384, 3078, 1250, 862. Anal. Calcd
for C13H28O2Si: C, 63.88; H, 11.55. Found: C, 63.90; H, 11.49.
4-[[1-[[(Dim eth yltr im eth ylsilyl)oxy]silyl]-2-m eth ylp r o-
p yl]oxy]-1-p en ten e, 21: GC tR 14.35 and 14.78 min (1:38).
1H NMR (CDCl3) δ 0.05 (s, 9 H), 0.10 (s, 6 H), 0.92 (d, 3 H, J
) 7 Hz), 0.95 (d, 3 H, J ) 7 Hz), 1.07 (d, 3 H, J ) 6 Hz), 1.92
(m, 1 H), 2.05 (m, 1 H), 2.30 (m, 1 H), 2.81 (d, 1 H, J ) 5 Hz),
3.40 (m, 1 H), 5.00 (m, 2 H), 5.77 (m, 1 H); 13C NMR (CDCl3)
4-[[1-[[(Dim eth yltr im eth ylsilyl)oxy]silyl]-2-m eth ylp r o-
p yl]oxy]-2-m eth yl-1-p en ten e, 25: GC tR 16.27 and 16.40 min
1
(1:37); H NMR (CDCl3) δ 0.05 (s, 9 H), 0.10 (s, 6 H), 0.93 (d,
3 H, J ) 7 Hz), 0.96 (d, 3 H, J ) 7 Hz), 1.05 (d, 3 H, J ) 7 Hz),
1.69 (s, 3 H), 1.93 (m, 2 H), 2.35 (m, 1 H), 2.80 (d, 1 H, J ) 5

Allylation Reactions of Mixed Silyl-Substituted Acetals
J . Org. Chem., Vol. 61, No. 7, 1996 2451
Hz), 3.49 (m, 1 H), 4.66 (s, 1 H), 4.72 (s, 1 H); 13C NMR (CDCl3)
ppm 0.03, 0.87, 1.94, 19.74, 20.52, 22.94, 29.70, 30.83, 45.59,
74.48, 77.23, 112.35, 143.24; IR (neat) (cm-1) 3060, 1240, 1050,
830.
solution of dimethyl sulfoxide (0.023 mL, 0.323 mmol dissolved
in 0.5 mL CH2Cl2) was added dropwise over a period of 2 min.
The reaction mixture was stirred at -60 °C for 10 min followed
by addition of 6 (15.8 mg, 0.049 mmol in 0.5 mL CH2Cl2) over
a period of 2 min. The reaction mixture was then stirred for
15 min at -60 °C. Triethylamine (0.068 mL, 0.49 mmol) was
then added dropwise over a period of 2 min, and the reaction
mixture was stirred at -60 °C for 30 min. The reaction
mixture was allowed to warm to room temperature, and water
(5 mL) was then added. Stirring was continued for 10 min,
and the layers were then separated. The aqueous layer was
extracted with CH2Cl2 (2 × 10 mL), and the combined organic
phases were washed sequentially with 0.5 N HCl (5 mL), water
(10 mL), saturated aqueous sodium bicarbonate (5 mL), and
water (10 mL). The organic phase was dried over anhydrous
magnesium sulfate, and the solvents were then removed under
reduced pressure. The crude product was purified by silica
gel chromatography using 2% ether/petroleum ether as eluent
(89%).
4-[[1-(Hyd r oxyDim et h ylsilyl)-2-m et h ylp r op yl]oxy]-2-
m eth yl-1-p en ten e, 31 (71%): 1H NMR (CDCl3) δ 0.16 (s, 3
H), 0.17 (s, 3 H), 0.93 (d, 3 H, J ) 6 Hz), 0.95 (d, 3 H, J ) 5
Hz), 1.11 (d, 3 H, J ) 7 Hz), 1.73 (s, 3 H), 1.96 (m, 2 H), 2.20
(s, 1 H), 2.30 (m, 1 H), 2.86 (d, 1 H, J ) 6 Hz), 3.55 (m, 1 H),
4.73 (s, 1 H), 4.79 (s, 1 H); 13C NMR (CDCl3) ppm -0.32, 0.42,
19.81, 20.13, 20.62, 23.01, 30.66, 45.82, 75.16, 77.91, 112.77,
143.95; IR (neat) (cm-1) 3420, 3075, 1075, 862, 780.
G. An om a lou s Rea ction P r od u ct F r om Sila n e 13.
3-(Dim eth ylsilyl)-2-h exyl-6-m eth yl-5-(2-m eth yl-2-eth en -
1-yl)-1-oxa cycloh exa n e, 33 (76%): 1H NMR (CDCl3) δ -0.02
(s, 3 H), 0.07 (s, 3 H), 0.65-0.85 (m, 2 H). 0.86 (t, 3 H, J ) 7
Hz), 1.05 (d, 3 H, J ) 7 Hz), 1.20-1.60 (m, 8 H), 1.61, (s, 3 H),
2.12 (m, 1 H), 3.07 (m, 1 H), 3.17 (m, 1 H), 4.59 (s, 1 H), 4.67
(s, 1 H); 13C NMR (CDCl3) ppm -7.37, -3.75, 14.06, 18.29,
18.52, 20.65, 22.62, 26.46, 31.76, 31.83, 51.15, 74.96, 78.81,
110.38, 149.70; IR (neat) (cm-1) 3072, 1248, 1094, 838, 781.
Anal. Calcd for C15H30OSi: C, 70.79; H, 11.88. Found: C,
70.87; H, 11.77.
H. Ver ifica tion of th e Rela tive Ster eoch em istr y. (a )
Syn th esis of 17 fr om 16. MeLi (1.4 M in ether, 4.2 mL, 10
equiv) was added dropwise to a solution of 16 (130 mg, 0.41
mmol) in 5 mL of dry THF at 0 °C. The reaction mixture was
allowed to warm to room temperature and stirred for 3 h.
Water (6 mL) was then added and the mixture stirred for an
additional 20 min. The layers were separated, and the
aqueous layer was extracted with petroleum ether (3 × 10 mL).
The combined organic phases were dried over anhydrous
magnesium sulfate, and the solvent was then removed under
reduced pressure. The crude product was purified by column
chromatography.
1-P h e n y l-3-[[1-(t r im e t h y ls ily l)h e x y l]o x y ]b u t a n -1-
1
on e, 20: GC tR 24.39 and 24.64 min (1:30); H NMR (CDCl3)
δ -0.03 (s, 9 H), 0.88 (t, 3 H, J ) 6 Hz), 1.18-1.64 (m, 11 H),
2.94 (dd, 1 H, J ) 7.5 Hz, J ′ ) 15 Hz), 3.09 (t, 1 H, J ) 6 Hz),
4.25 (dd, 1 H, J ) 5 Hz, J ′ ) 16 Hz), 4.04 (m, 1 H), 7.45 (m, 2
H), 7.56 (m, 1 H), 7.95 (d, 2 H, J ) 8 Hz); 13C NMR (CDCl3)
ppm -2.88, 14.06, 21.16, 22.59, 26.79, 32.15, 32.25, 46.24,
72.19, 72.61, 128.25, 128.51, 132.97, 137.46, 199.14; IR (neat)
(cm-1) 3070, 1740, 1680, 1250, 855, 730. The GC tR for the
minor isomer matches that for syn-20.4a
I. Gen er a l P r oced u r e for In tr a m olecu la r Allyla tion
Usin g 1a . (a ) Alip h a tic a n d Ar yl Ald eh yd es. The alde-
hyde (0.1 mmol) and 1a (281 mg, 0.14 mmol) were dissolved
in 2 mL of CH2Cl2. A neat sample of BF3·OEt2 (6.2 µL, 0.5
mmol) was then added dropwise via syringe at room temper-
ature. The reaction mixture was stirred for 10 min at room
temperature and then quenched by the addition of 5 mL of
water. The reaction mixture was extracted with diethyl ether
(3 × 10 mL). The combined ether phases were washed with
water (10 mL) and dried over anhydrous sodium sulfate and
the solvent removed under reduced pressure. The crude Si-F
4-[[1-(Tr im eth ylsilyl)h exyl]oxy]-1-p en ten e, 17 (91%):
1H NMR (CDCl3) δ 0.00 (s, 9 H), 0.88 (t, 3 H, J ) 7 Hz), 1.08
(d, 3 H, J ) 6 Hz), 1.23-1.59 (m, 8 H), 2.08 (m, 1 H), 2.27 (m,
1 H), 3.00 (t, 1 H, J ) 6 Hz), 3.36 (m, 1 H), 5.00 (m, 2 H), 5.77
(m, 1 H); 13C NMR (CDCl3) ppm -2.78, 14.09, 20.07, 22.62,
26.92, 32.09, 32.25, 41.55, 71.60, 75.19, 116.42, 135.65; IR
compound was dissolved in
a mixture of 2 mL of 10%
(neat) (cm-1): 3080, 1640, 1240, 830. Anal. Calcd for C14H30
OSi: C, 69.34; H, 12.47. Found: C, 69.25; H, 12.41.
-
methanolic KOH, 2 mL of H2O, and 5 mL of THF and stirred
overnight at room temperature. The reaction mixture was
diluted with water (10 mL) and extracted with ether (3 × 20
mL). The combined organic phases were dried over anhydrous
sodium sulfate, and the solvent was removed under reduced
pressure. The crude Si-OH compound was purified by flash
chromatography on silica gel using 5% ether/petroleum ether
as eluent.
4-[[1-(Hyd r oxyd im eth ylsilyl)h exyl]oxy]-1-p en ten e, 35a
(26) (49%): GC tR 13.36 and 13.69 min (1:73); 1H NMR (CDCl3)
δ 0.13 (s, 6 H), 0.87 (t, 3 H, J ) 6 Hz), 1.24 (d, 3 H, J ) 6 Hz),
1.23-1.60 (m, 8 H), 2.13 (m, 1 H), 2.25 (m, 1 H), 3.02 (t, 1 H,
J ) 7 Hz), 3.47 (m, 1 H), 5.06 (m, 2 H), 5.81 (m, 1 H); 13C
NMR (CDCl3) ppm -1.94, -1.29, 14.06, 20.52, 22.55, 26.53,
31.50, 32.22, 41.33, 71.83, 75.68, 117.00, 135.81; IR (neat)
(cm-1) 3400, 3070, 1660, 1250, 1080, 850. Anal. Calcd for
C13H28O2Si: C, 63.88; H, 11.55. Found: C, 63.95; H, 11.47.
4-[1-(Dim et h ylflu or osilyl)h exyl]oxy]-5-m et h yl-1-h ex-
en e, 34a : GC tR 16.73 and 16.79 min. (118:1); 1H NMR
(CDCl3) δ 0.22 (m, 6 H), 0.86 (m, 9 H), 1.23-1.61 (m, 8 H),
1.77 (m, 1 H), 2.18 (m, 2 H), 3.17 (m, 2 H), 5.01 (m, 2 H), 5.79
(m, 1 H); 13C NMR (CDCl3) ppm -3.17 (-3.33), -2.29 (-2.49),
14.02, 17.48, 18.64, 22.52, 26.01, 30.28, 32.28, 34.87, 68.89
(68.66), 82.24, 116.32, 135.68; 19F NMR (CFCl3) -163.44; IR
(neat) (cm-1) 3080, 1640, 1250, 1040, 870.
4-[[1-(Hydr oxydim eth ylsilyl)h exyl]oxy]-5-m eth yl-1-h ex-
en e, 35b (81%): 1H NMR (CDCl3) δ 0.13 (s, 6 H), 0.87 (m, 9
H), 1.23-1.57 (m, 8 H), 1.80 (m, 1 H), 2.02 (s, 1 H), 2.19 (t, 2
H, J ) 6 Hz), 3.05 (t, 1 H, J ) 6 Hz), 3.15 (q, 1 H, J ) 5 Hz),
5.06 (m, 2 H), 5.82 (m, 1 H); 13C NMR (CDCl3) ppm -1.94,
-1.16, 14.02, 18.00, 18.29, 22.52, 26.33, 30.31, 30.73, 32.34,
34.64, 70.47, 82.40, 116.81, 136.26; IR (neat) (cm-1) 3400, 3080,
1640, 1250, 1040, 860. Anal. Calcd for C15H32O2Si: C, 66.11;
H, 11.84. Found: C, 66.38; H, 11.77.
(b) Con ver sion of 17 to th e Ald ol P r od u ct 20. Syn th e-
sis of 19. Ozone was passed through a solution of syn-17
(163.5 mg, 0.67 mmol) in 10 mL of MeOH at -78 °C until a
blue color persisted. Excess ozone was then purged from the
reaction with argon. Dimethyl sulfide (2 mL) was then added
and the mixture allowed to warm to room temperature. The
reaction mixture was concentrated under reduced pressure,
and the residue was taken up in ether (50 mL). The ether
layer was washed with water (2 × 5 mL) and dried over
anhydrous magnesium sulfate. The solvent was then removed
under reduced pressure. PhMgCl (2 M in THF, 1.7 mL, 3.4
mmol) was added dropwise to a solution of the crude aldehyde
in dry THF (10 mL) at 0 °C. The reaction mixture was allowed
to warm to room temperature, stirred for 2 h, and then
quenched by the addition of 5 mL water. The layers were
separated, and the aqueous layer was extracted with ether (3
× 10 mL). The combined organic phases were washed
sequentially with 0.1N HCl (5 mL), water (10 mL), and
saturated aqueous sodium chloride solution (10 mL) and then
dried over anhydrous magnesium sulfate. The solvent was
removed under reduced pressure to provide crude alcohol
which was purified by silica gel column chromatography. The
overall yield for two steps was 56%.
1-P h en yl-3-[[1-(tr im eth ylsilyl)h exyl]oxy]bu ta n -2-ol, 19:
1H NMR (CDCl3) δ 0.13 (s, 9 H), 0.90 (t, 3 H, J ) 6 Hz), 1.18
(d, 3 H, J ) 6 Hz), 1.91-1.21 (m, 10 H), 3.20 (t, 1 H, J ) 6
Hz), 3.89 (m, 1 H), 4.60 (s, 1 H), 4.93 (d, 1 H, J ) 9 Hz), 7.33
(m, 5 H); 13C NMR (CDCl3) ppm -2.62, 14.09, 20.16, 22.59,
26.88, 32.09, 32.60, 47.24, 71.38, 74.25, 125.63, 125.99, 127.08,
128.22, 144.73; IR (neat) (cm-1) 3450, 3040, 1250, 1120, 840,
730.
Syn th esis of 20.4a Oxalyl chloride (0.014 mL, 0.162 mmol)
was dissolved in 1 mL of CH2Cl2 and cooled to -60 °C.
A

2452 J . Org. Chem., Vol. 61, No. 7, 1996
Linderman and Chen
4-[[1-(Dim eth ylflu or osilyl)h exyl]oxy]-1-n on en e, 34c: GC
tR 19.72 and 19.80 min (113:1); H NMR (CDCl3) δ 0.23 (t, 6
3411, 3074, 1251, 1072, 865, 735. Anal. Calcd for C18H29NO4-
Si: C, 61.50; H, 8.32. Found: C, 61.26; H, 8.37.
1
H, J ) 8 Hz), 0.87 (m, 6 H), 1.20-1.60 (m, 16 H), 2.18 (m, 2
H), 3.16 (t, 1 H, J ) 6.6 Hz), 3.31 (m, 1 H), 5.05 (m, 2 H), 5.78
(m, 1 H); 13C NMR (CDCl3) ppm -3.07 (-3.26), -2.36 (-2.55),
14.06, 22.55, 22.65, 25.04, 26.11, 30.70, 32.02, 32.28, 33.93,
38.39, 69.37 (69.60), 78.49, 116.62, 135.32; 19F NMR (CFCl3)
-163.8; IR (neat) (cm-1): 3080, 1640, 1250, 1040, 870.
4-[[1-(Hyd r oxyd im eth ylsilyl)h exyl]oxy]-1-n on en e, 35c
(82%): 1H NMR (CDCl3) δ 0.16 (s, 6 H), 0.89 (t, 6 H, J ) 6
Hz), 1.20-1.60 (m, 16 H), 2.22 (m, 2 H), 3.07 (t, 1 H, J ) 6
Hz), 3.36 (m, 1 H), 5.08 (m, 2 H), 5.83 (m, 1 H); 13C NMR
(CDCl3) ppm -1.91, -1.20, 14.02, 22.55, 22.62, 25.14, 26.37,
30.99, 31.99, 32.31, 34.22, 38.36, 70.93, 78.36, 116.94, 135.74;
IR (neat) (cm-1) 3400, 3080, 1640, 1250, 1035, 860. Anal. Calcd
for C17H36O2Si: C, 67.94; H, 12.07. Found: C, 68.03; H, 12.04.
4-Cycloh exyl-4-[[1-(h yd r oxyd im eth ylsilyl)h exyl]oxy]-
1-bu ten e, 35d (85%): 1H NMR (CDCl3) δ 0.13 (s, 6 H), 0.87
(t, 3 H, J ) 7 Hz), 1.00-1.72 (m, 19 H), 2.05 (s, 1 H), 2.20 (m,
2 H), 3.04 (t, 1 H, J ) 6 Hz), 3.14 (q, 1 H, J ) 5 Hz), 5.06 (m,
2 H), 5.82 (m, 1 H); 13C NMR (CDCl3) ppm -1.91, -1.16, 14.02,
22.52, 26.30, 26.40, 26.66, 28.60, 28.89, 30.66, 32.31, 34.67,
40.46, 70.38, 81.85, 116.78, 136.20; IR (neat) (cm-1) 3350, 3070,
1240, 1030, 860. Anal. Calcd for C18H36O2Si: C, 69.17; H,
11.61. Found: C, 69.01; H, 11.53.
4-P h e n yl-4-[[1-(h yd r oxyd im e t h ylsilyl)h e xyl]oxy]-1-
bu ten e, 35e (93%): 1H NMR (CDCl3) δ 0.20 (s, 3 H), 0.22 (s,
3 H), 0.78 (t, 3 H, J ) 6 Hz), 0.87-1.50 (m, 8 H), 2.02 (s, 1 H),
2.42 (m, 1 H), 2.58 (m, 1 H), 3.08 (t, 1 H, J ) 6 Hz), 4.32 (t, 1
H, J ) 6 Hz), 5.07 (m, 2 H), 5.81 (m, 1 H), 7.32 (m, 5 H); 13C
NMR (CDCl3) ppm -0.93, -0.28, 14.65, 23.11, 26.89, 32.06,
32.48, 43.18, 73.10, 83.56, 117.91, 127.83, 128.18, 128.76,
136.32, 143.63; IR (neat) (cm-1) 3450, 3070, 3030, 1250, 1060,
830, 700. Anal. Calcd for C18H30O2Si: C, 70.53; H, 9.87.
Found: C, 70.60; H, 9.89.
4-(4′-Bip h en ylyl)-4-[[1-(h yd r oxyd im et h ylsilyl)h exyl]-
oxy]-1-bu ten e, 35f (77%): 1H NMR (CDCl3) δ 0.19 (s, 3 H),
0.21 (s, 3 H), 0.74 (t, 3 H, J ) 7 Hz), 0.80-1.50 (m, 8 H), 2.12
(s, 1 H), 2.43 (m, 1 H), 2.60 (m, 1 H), 3.10 (t, 1 H, J ) 6 Hz),
4.35 (dd, 1 H, J ) 5 Hz, J ′ ) 8 Hz), 5.07 (m, 2 H), 5.86 (m, 1
H), 7.32-7.60 (m, 9 H); 13C NMR (CDCl3) ppm -1.68, -1.00,
13.96, 22.39, 26.17, 31.34, 31.76, 42.43, 72.41, 82.56, 117.33,
126.79, 127.02, 127.15, 127.54, 128.70, 135.58, 140.36, 140.91,
141.98; IR (neat) (cm-1) 3503, 3065, 3029, 1787, 1696, 734.
Anal. Calcd for C24H34O2Si: C, 75.34; H, 8.96. Found: C,
75.12; H, 8.93.
4-(2'-Naph th yl)-4-[[1-(h ydr oxydim eth ylsilyl)h exyl]oxy]-
1-bu ten e, 35g (75%): 1H NMR (CDCl3) δ 0.20 (s, 3 H), 0.22
(s, 3 H), 0.64 (t, 3 H, J ) 7 Hz), 0.80-1.45 (m 8 H), 2.05 (s, 1
H), 2.48 (m, 1 H), 2.65 (m, 1 H), 3.11 (dd, 1 H, J ) 6 Hz, J ′ )
7 Hz), 4.47 (dd, 1 H, J ) 5 Hz, J ′ ) 8 Hz), 5.06 (m, 2 H), 5.83
(m, 1 H), 7.47 (m, 3 H), 7.71 (s, 1 H), 7.81 (m, 3 H); 13C NMR
(CDCl3) ppm -1.68, -0.97, 13.80, 22.36, 26.21, 31.38, 31.70,
42.39, 72.14, 83.01, 117.33, 124.95, 125.66, 125.95, 126.18,
127.63, 127.80, 127.92, 133.00, 133.06, 135.55, 140.27; IR
(neat) (cm-1) 3406, 3058, 1250, 1069, 858, 778, 746. Anal.
Calcd for C22H32O2Si: C, 74.10; H, 9.05. Found: C, 74.38; H,
9.28.
4-[[1-(H yd r oxyd im et h ylsilyl)h exyl]oxy]-4-[4′-(r′,r′,r′-
tr iflu or om eth yl)p h en yl]-1-bu ten e, 35j (80%): 1H NMR
(CDCl3) δ 0.17 (s, 3 H), 0.20 (s, 3 H), 0.74 (t, 3 H, J ) 7 Hz),
0.90-1.45 (m, 8 H), 2.04 (s, 1 H), 2.38 (m, 1 H), 2.53 (m, 1 H),
3.05 (t, 1 H, J ) 7 Hz), 4.37 (dd, 1 H, J ) 6 Hz, J ) 7 Hz), 5.06
(m, 2 H), 5.74 (m, 1 H), 7.49 (dd, 4 H, J ) 9 Hz, J ′ ) 14 Hz);
13C NMR (CDCl3) ppm -1.71, -1.10, 13.83, 22.36, 26.21, 31.25,
31.76, 42.36, 73.09, 82.14, 117.78, 125.05, 127.28, 129.86,
134.81, 147.25; 19F NMR (CFCl3) -62.93; IR (neat) (cm-1) 3375,
1068, 865, 839. Anal. Calcd for C19H29F3O2Si: C, 60.93; H,
7.80. Found: C, 61.09; H, 7.85.
4-[[1-(H yd r oxyd im et h ylsilyl)h exyl]oxy]-4-[3′-(r′,r′,r′-
tr iflu or om eth yl)p h en yl]-1-bu ten e, 35k (73%): 1H NMR
(CDCl3) δ 0.17, (s, 3 H), 0.20 (s, 3 H), 0.74 (t, 3 H, J ) 7 Hz),
0.90-1.40 (m, 8 H), 2.05 (s, 1 H), 2.38 (m, 1 H), 2.53 (m, 1 H),
3.03 (t, 1 H, J ) 6 Hz,), 4.37 (dd, 1 H, J ) 5 Hz, J ′ ) 8 Hz),
5.06 (m, 2 H), 5.77 (m, 1 H), 7.39-7.58 (m, 5 H); 13C NMR
(CDCl3) ppm -1.75, -1.10, 13.86, 22.33, 26.33, 31.28, 31.80,
42.49, 73.12, 82.27, 117.81, 123.72, 123.79, 124.31, 125.95,
128.51, 130.41, 134.90, 144.77; 19F NMR (CFCl3) -64.07; IR
(neat) (cm-1) 3388, 3077, 1253, 1129, 567. Anal. Calcd for
C19H29F3O2Si: C, 60.93; H, 7.80. Found: C, 61.07; H, 7.92.
4-[[1-(H yd r oxyd im et h ylsilyl)h exyl]oxy]-4-[2′-(r′,r′,r′-
tr iflu or om eth yl)p h en yl]-1-bu ten e, 35l (72%): 1H NMR
(CDCl3) δ 0.17 (s, 3 H), 0.18 (s, 3 H), 0.72 (t, 3 H, J ) 7 Hz),
0.80-1.40 (m, 8 H), 2.03 (s, 1 H), 2.38 (m, 2 H), 3.05 (t, 1 H,
J ) 7 Hz), 4.75 (m, 1 H), 5.08 (m, 2 H), 5.92 (m, 1 H), 7.33 (t,
1 H, J ) 8 Hz), 7.55 (m, 2 H), 7.75 (d, 1 H, J ) 8 Hz); 13C
NMR (CDCl3) ppm -1.71, -1.04, 13.89, 22.30, 26.11, 31.25,
31.73, 43.59, 74.16, 78.23, 117.58, 124.92, 125.02, 127.18,
128.73, 131.71, 135.68, 143.34; 19F NMR (CFCl3) -59.20; IR
(neat) (cm-1) 3417, 3075, 1313, 1123, 834, 769.
4-[[1-(Hydr oxydim eth ylsilyl)h exyl]oxy]-4-(4′-m eth ylph e-
n yl)-1-bu ten e, 35m (78%): 1H NMR (CDCl3) δ 0.17 (s, 3 H),
0.19 (s, 3 H), 0.76 (t, 3 H, J ) 8 Hz), 0.90-1.45 (m, 8 H), 2.29
(s, 1 H), 2.33 (s, 3 H), 2.36 (m, 1 H), 2.56 (m, 1 H), 3.04 (t, 1 H,
J ) 6 Hz), 4.26 (dd, 1 H, J ) 6 Hz, J ′ ) 7 Hz), 5.05 (m, 2 H),
5.81 (m, 1 H), 7.15 (dd, 4 H, J ) 8 Hz, J ′ ) 24 Hz); 13C NMR
(CDCl3) ppm -1.65, -0.97, 13.96, 21.10, 22.46, 26.17, 31.38,
31.76, 42.43, 71.99, 82.59, 117.13, 127.08, 128.76, 135.81,
137.10, 139.82; IR (neat) (cm-1) 3405, 3076, 1251, 1069, 846,
833, 780, 735. Anal. Calcd for C19H32O2Si: C, 71.19; H, 10.06.
Found: C, 70.95; H, 9.97.
4-[[1-(H yd r oxyd im et h ylsilyl)h exyl]oxy]-4-(2′,4′,6′-t r i-
m eth ylp h en yl)-1-bu ten e, 35n (34%): 1H NMR (CDCl3) δ
0.16 (s, 3 H), 0.17 (s, 3 H), 0.73 (t, 3 H, J ) 7 Hz), 0.87-1.60
(m, 8 H), 2.04 (s, 1 H), 2.20 (s, 3 H), 2.25-2.50 (m, 7 H), 2.71
(m, 1 H), 3.05 (t, 1 H, J ) 6 Hz), 4.68 (dd, 1 H, J ) 6 Hz, J ′ )
8 Hz), 5.07 (m, 2 H), 5.80 (m, 1 H), 6.78 (m, 2 H); 13C NMR
(CDCl3) ppm (major diastereomer) -1.65, -1.10, 13.89, 20.71,
20.84, 22.36, 26.04, 31.12, 31.96, 39.94, 75.00, 80.52, 116.91,
128.89, 130.12, 131.22, 135.71, 136.10, 136.16, 136.46; IR
(neat) (cm-1) 3405, 3076, 1612, 1250, 1057, 851, 782. Anal.
Calcd for C21H36O2Si: C, 72.36; H, 10.41. Found: C, 72.62;
H, 10.31.
4-[4-(Meth yloxy)p h en yl]-1,6-h ep ta d ien e, 38 (31%): 1H
NMR (CDCl3) δ 2.33 (m, 4 H), 2.65 (m, 1 H), 3.77 (s, 3 H), 4.92
(m, 2 H), 5.63 (m, 1 H), 6.81 (d, 2 H, J ) 9 Hz), 7.05 (d, 2 H,
4-(2′-Br om oph en yl)-4-[[1-(h ydr oxydim eth ylsilyl)h exyl]-
oxy]-1-bu ten e, 35h (72%): 1H NMR (CDCl3) δ 0.19 (s, 3 H),
0.20 (s, 3 H), 0.76 (t, 3 H, J ) 8 Hz), 0.80-1.55 (m, 8 H), 2.15
(s, 1 H), 2.41 (t, 2 H, J ) 8 Hz), 3.09 (t, 1 H, J ) 7 Hz), 4.83
(m, 1 H), 5.07 (m, 2 H), 5.87 (m, 1 H), 7.11 (m, 1 H), 7.28 (m,
1 H), 7.49 (m, 2 H); 13C NMR (CDCl3) ppm -1.65, -1.03, 13.89,
22.33, 26.27, 31.31, 31.80, 41.72, 73.87, 80.88, 117.49, 122.50,
127.28, 128.64, 132.16, 135.19, 142.56; IR (neat) (cm-1) 3412,
3074, 1072, 910, 865, 735. Anal. Calcd for C18H29BrO2Si: C,
56.09; H, 7.58. Found: C, 55.84; H, 7.59.
J
) 9 Hz); 13C NMR (CDCl3) ppm 40.46, 44.69, 55.13,
113.55,113.71, 115.97, 128.54, 136.65, 136.91; IR (neat) (cm-1
)
3067, 3032, 1602, 1240, 1030, 821; HRMS calcd for C14H18
202.1358, found 202.1347.
O
(b) r,â-Un sa tu r a ted Ald eh yd es. A slightly modified
reaction procedure compared to that described above was
employed for reactions of 1a with trans-cinnamaldehyde or
trans-crotonaldehyde. The reaction mixture was stirred at
-78 °C for 1 h after the addition of the Lewis acid, gradually
warmed to -40 °C, stirred at -40 °C for 1 h, and then warmed
to -20 to -10 °C, and stirred for an additional 1.5 h. Reaction
progress was monitored by TLC until the starting aldehyde
was consumed.
4-(4′-Nitr op h en yl)-4-[[1-(h yd r oxyd im eth ylsilyl)h exyl]-
oxy]-1-bu ten e, 35i (85%): 1H NMR (CDCl3) δ 0.17 (s, 3 H),
0.20 (s, 3 H), 0.75 (t, 3 H, J ) 7 Hz), 0.99-1.45 (m, 8 H), 1.92
(s, 1 H), 2.39 (m, 1 H), 2.51 (m, 1 H), 3.06 (t, 1 H, J ) 7 Hz),
4.56 (m, 1 H), 5.01 (m, 2 H), 5.73 (m, 1 H), 7.47 (d, 2 H, J ) 8
Hz), 8.17 (d, 2 H, J ) 9 Hz); 13C NMR (CDCl3) ppm -1.75,
-1.31, 13.89, 22.36, 26.27, 31.25, 31.83, 42.30, 73.61, 81.69,
3-[[1-(Hyd r oxyd im eth ylsilyl)h exyl]oxy]-1-p h en yl-1,5-
h exa d ien e, 39 (55%): 1H NMR (CDCl3) δ 0.19 (s, 3 H), 0.20
(s, 3 H), 0.79 (t, 3 H, J ) 7 Hz), 1.15-1.65 (m, 8 H), 2.04 (s, 1
118.17, 123.40, 127.63, 134.23, 147.28, 150.93; IR (neat) (cm-1
)

Allylation Reactions of Mixed Silyl-Substituted Acetals
J . Org. Chem., Vol. 61, No. 7, 1996 2453
H), 2.35 (m, 1 H), 2.43 (m, 1 H), 3.14 (dd, 1 H, J ) 6 Hz, J ′ )
8 Hz), 3.89 (m, 1 H), 5.11 (m, 2 H), 5.89 (m, 1 H), 6.09 (dd, 1
H, J ) 8 Hz, J ′ ) 15 Hz), 6.50 (d, 1 H, J ) 16 Hz), 7.20-7.41
(m, 5 H); 13C NMR (CDCl3) ppm -1.84, -1.26, 13.96, 22.59,
26.56, 31.63, 31.96, 40.58, 71.57, 81.75, 117.36, 126.41, 127.60,
128.54, 131.09, 131.77, 135.26, 136.65; IR (neat) (cm-1) 3407,
3079, 3027, 1641, 1450, 1250, 1058, 858, 748, 692. Anal.
Calcd for C20H32O2Si: C, 72.23; H, 9.70. Found: C, 72.30; H,
9.72.
2 H, J ) 11 Hz, J ′ ) 30 Hz), 5.05 (m, 2 H), 5.86 (m, 1 H), 7.33
(m, 5 H); 13C NMR (CDCl3) ppm 26.27, 26.33, 26.59, 28.66,
28.95, 35.25, 41.04, 71.83, 83.27, 116.49, 127.34, 127.73,
128.25, 135.61, 139.04; IR (neat) (cm-1) 3066, 3030, 1097, 1069,
734, 696. Anal. Calcd for
Found: C, 83.36; H, 9.95.
C17H24O: C, 83.55; H, 9.90.
4-[[1-[(Dim et h ylflu or osilyl)p h en yl]m et h yl]oxy]-4-cy-
cloh exyl-1-bu ten e, 42 (93%): GC tR 22.76 and 22.86 min
1
(>120:1); H NMR (CDCl3) δ 0.14 (d, 3 H, J ) 8 Hz), 0.27 (d,
4-[[1-(H yd r oxyd im et h ylsilyl)h exyl]oxy]-1,5-h ep t a d i-
en e, 40 (50%): GC tR 16.54 and 16.74 min (22:1); 1H NMR
(CDCl3) δ 0.14 (s, 6 H), 0.80-1.60 (m, 11 H), 1.68 (d, 3 H, J )
7 Hz), 1.93 (s, 1 H), 2.19 (m, 1 H), 2.82 (m, 1 H), 3.03 (dd, 1 H,
J ) 6 Hz, J ′ ) 8 Hz), 3.61 (q, 1 H, J ) 7 Hz), 5.05 (m, 2 H),
5.31 (m, 1 H), 5.55 (m, 1 H), 5.81 (m, 1 H); 13C NMR (CDCl3)
ppm -1.84, -1.26, 14.06, 17.64, 22.59, 26.37, 31.57, 31.92,
40.49, 70.86, 81.75, 116.94, 128.09, 132.71, 135.71; IR (neat)
(cm-1) 3419, 3077, 1250, 1058, 863, 782. Anal. Calcd for
C15H30O2Si: C, 66.61; H, 11.18. Found: C, 66.72; H, 11.13.
J . In ter m olecu la r Allyla tion Rea ction . Syn th esis of
36. Silanol 8 (53 mg, 0.30 mmol), hexanal (30 mg, 0.31 mmol),
and allyltrimethylsilane (38 mg, 0.33 mmol) were dissolved
in 3 mL of CH2Cl2, and the mixture was cooled to -78 °C.
Trimethylsilyl triflate (64 µL, 0.33 mmol) was then added, and
the reaction mixture was stirred for 30 min. The reaction
mixture was then quenched by the addition of 1 mL of water
and allowed to warm to room temperature. The mixture was
then diluted with ether (25 mL) and washed with water (5
mL). The organic phase was dried over anhydrous magnesium
sulfate, and the solvents were removed under reduced pres-
sure. The crude product was purified by flash chromatography
on silica gel using hexane as eluent.
4-[[(1-Tr im eth ylsilyl)h exyl]oxy]n on en e, 36 (74%): GC
tR 20.36 and 20.45 min (3.4:1); 1H NMR (CDCl3) δ (mixture of
diastereomers) 0.02 (s, 9H), 0.85-1.60 (m, 22H), 2.22 (m, 2H),
3.05 (m, 1H), 3.28 (m, 1H), 5.05 (m, 2h), 5.85 (m, 1H); 13C NMR
(CDCl3) ppm -2.65, -2.33, 14.06, 22.65, 24.98, 26.72, 26.82,
29.70, 31.50, 31.67, 31.83, 32.09, 32.18, 32.34, 33.77, 33.93,
38.39, 38.58, 70.50, 70.96, 77.65, 78.25, 116.10, 116.29, 135.65,
135.81; IR (neat) (cm-1) 3095, 2925, 1640, 1450, 1250. Anal.
Calcd for C18H38OSi: C, 72.40; H, 12.83. Found: C, 72.51; H,
12.79.
3 H, J ) 8 Hz), 0.90-1.90 (m, 10 H), 1.95 (d, 1 H, J ) 11 Hz),
2.28 (m, 1 H), 2.37 (m, 1 H), 3.16 (q, 1 H, J ) 5 Hz), 4.41 (s, 1
H), 5.07 (m, 2 H), 5.81 (m, 1 H), 7.25 (m, 5 H); 13C NMR (CDCl3)
ppm -3.91 (-4.10), -3.56 (-3.75), 26.30, 26.37, 26.59, 28.44,
29.34, 33.06, 40.58, 72.22 (71.99), 79.94, 116.58, 126.37, 126.86,
128.18, 134.90, 139.46; 19F NMR (CFCl3) -166.66; IR (neat)
(cm-1) 3426, 3078, 3024, 1252, 1047, 886, 700.
L. Th e Cr ossover Rea ction . Trimethylsilyl triflate (60
µL, 0.31 mmol) was added dropwise to a solution of 2b (37.5
mg, 0.163 mmol) and 11 (41.1 mg, 0.150 mmol) in 3 mL of
CH2Cl2 at -78 °C. The reaction mixture was stirred for 2 h
at -78 °C, and then quenched by the addition of 6 mL of water.
The reaction mixture was then allowed to warm to room
temperature. The layers were separated, and the aqueous
layer was extracted with petroleum ether (3 × 20 mL). The
combined organic phases were dried over anhydrous sodium
sulfate, and the solvents were removed under reduced pres-
sure. The crude product was then added to a mixture of 2
mL of 10% methanolic KOH, 2 mL of H2O, and 5 mL of THF
and the resulting mixture stirred overnight at room temper-
ature. The crude silanol mixture was then dissolved in 3 mL
of CH2Cl2, and 10 equiv triethylamine and 5 equiv trimeth-
ylsilyl chloride were added at 0 °C. The reaction mixture was
allowed to warm to room temperature and the resulting
mixture stirred overnight. Water (6 mL) was then added, and
the layers were separated. The aqueous layer was extracted
with petroleum ether (3 × 20 mL). The combined organic
layers were dried over anhydrous sodium sulfate, and the
solvents were removed under reduced pressure. GC analysis
was performed at this stage to determine the overall composi-
tion of the reaction mixture. The crude products were purified
by silica gel chromatography as described above. Siloxane 21
was obtained in 79% yield as a 1:38 mixture of diastereomers.
Siloxane 22 was obtained in 69% yield as a 1:25 mixture of
diastereomers.
K. At t em p t ed In t r a m olecu la r Allyla t ion Usin g 1C.
The same procedure as described above for the reactions of
1a was employed. The benzyl ether 41 was obtained after the
basic hydrolysis step; however, removal of the solvents and
careful column chromatography on deactivated silica gel
provided the silyl fluoride 42 in excellent yield and in >90%
purity. The main contaminant is the silanol. Resubjection of
the silyl fluoride 42 to the basic hydrolysis conditions provided
the benzyl ether in nearly quantitative yield.
Ack n ow led gm en t. Financial support from the Na-
tional Institutes of Health (GM47275) is gratefully
acknowledged. The authors would also like to thank
Mohamed J aber for carrying out the intermolecular
allylation reaction.
Ben zyl 4-cycloh exylbu ten -1-yl eth er , 41: 1H NMR (CDCl3)
δ 0.90-2.00 (m, 11 H), 2.31 (m, 2 H), 3.18 (m, 1 H), 4.52 (dd,
J O9517048