Ring-opening reactions of cyclic acetals and 1,3-oxazolidines with halosilane equivalents

Article abstract of DOI:10.1021/jo020019f

Reactions of acetal and 1,3-oxazolidine rings were examined using two kinds of iodosilane equivalent reagents, a 1:2 mixture of Me₃SiNEt₂ and MeI (reagent 1a) and a 1:1 mixture of Et₃SiH and MeI containing a catalytic amount of PdCl₂ (reagent 1b). In the reactions of alkanone ethylene acetals with reagent 1a, a C-O bond in the acetal ring readily cleaved to give 2-(trimethylsiloxy)ethyl enol ethers. Similarly, the C-O bond of 1,3-oxazolidine rings cleaved to give ring-opened imine or enamine derivatives. The reactions of aromatic ketone ethylene acetals and cyclohexanone trimethylene acetal led to deprotection of the acetal unit to liberate free ketones. With reagent 1b, cycloalkanone ethylene acetal afforded a dimeric product with 2-iodoethyl alkenoate moieties, while aromatic ketone ethylene or trimethylene acetals produced deprotected ketones.

Full text of DOI:10.1021/jo020019f

Rin g-Op en in g Rea ction s of Cyclic Aceta ls a n d 1,3-Oxa zolid in es
w ith Ha losila n e Equ iva len ts
Arihiro Iwata, Heqing Tang, and Atsutaka Kunai*
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527, J apan
J oji Ohshita
Institute for Fundamental Research of Organic Chemistry, Kyushu University, Fukuoka 812-8581, J apan
Yasushi Yamamoto and Chinami Matui
Silicone-Electronic Materials Research Center, Shin-Etsu Chemical Co., Ltd., 1-10 Hitomi, Matsuida,
Gunma 379-0224, J apan
akunai@hiroshima-u.ac.jp
Received J anuary 8, 2002
Reactions of acetal and 1,3-oxazolidine rings were examined using two kinds of iodosilane equivalent
reagents, a 1:2 mixture of Me3SiNEt2 and MeI (reagent 1a ) and a 1:1 mixture of Et3SiH and MeI
containing a catalytic amount of PdCl2 (reagent 1b). In the reactions of alkanone ethylene acetals
with reagent 1a , a C-O bond in the acetal ring readily cleaved to give 2-(trimethylsiloxy)ethyl
enol ethers. Similarly, the C-O bond of 1,3-oxazolidine rings cleaved to give ring-opened imine or
enamine derivatives. The reactions of aromatic ketone ethylene acetals and cyclohexanone
trimethylene acetal led to deprotection of the acetal unit to liberate free ketones. With reagent 1b,
cycloalkanone ethylene acetal afforded a dimeric product with 2-iodoethyl alkenoate moieties, while
aromatic ketone ethylene or trimethylene acetals produced deprotected ketones.
In tr od u ction
without special care and react readily with several
organic substrates containing a C-O bond. Their reac-
tions with cyclic ethers afford ring-opened R-iodo-ω-
siloxyalkanes in good yield.6 It has also been reported
that treatment of alkyl esters of alkanoic acids with
reagent 1a affords trimethylsilyl alkanoates with the
liberation of alkyl iodides,7 while similar reactions of
alkanones give trimethylsilyl enol ethers.8 To further
explore the scope of the synthetic utilities of the iodo-
silane equivalents, we examined the reactions of acetals10
and 1,3-oxazolidines that have a five- or six-membered
ring with reagents 1a and 1b.
Halosilanes are widely used in areas of synthetic
organic chemistry.1 For example, it has been reported
that the reactions of cyclic ethers2 and lactones3 with
iodo- and bromosilanes produce R-halo-ω-siloxy com-
pounds in good yields. It has also been reported that
deprotection of acetal moieties with trimethyliodosilane
takes place to give free ketones under neutral conditions.4
However, in contrast to fluoro- and chlorosilanes, the use
of iodosilanes is rather limited due to their strong
tendency to undergo hydrolytic cleavage of the silicon-
halogen bonds even with atmospheric moisture.5
Recently, we have demonstrated that a 1:2 mixture of
Me3SiNEt2 and MeI (reagent 1a ) and a 1:1 mixture of
Et3SiH and MeI containing a catalytic amount of PdCl2
(reagent 1b) act as synthetic equivalents of Me3SiI and
Et3SiI, respectively.6-9 These reagents can be handled
Resu lts a n d Discu ssion
Rea ction s of Alk a n on e Aceta l Rin gs w ith Re-
a gen t 1a . Reactions of cyclic acetals 2a -g derived from
cyclic or acyclic alkanones were examined, as listed in
Table 1. All these reactions were carried out using 1 equiv
of reagent 1a in toluene at 80-90 °C for 12 h, and the
products were isolated by distillation and verified on the
basis of spectroscopic and elemental analyses.
* Corresponding author.
(1) Larson, G. L. In The Chemistry of Organic Silicon Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Part 1, Chapter
11.
(2) Kru¨erke, U. Chem. Ber. 1962, 95, 174.
(3) Kricheldorf, H. R. Angew. Chem., Int. Ed. Engl. 1979, 18, 689.
(4) J ung, M. E.; Andrus, W. A.; Ornstein, P. L. Tetrahedron Lett.
1977, 4175.
(5) Walsh, R. In The Chemistry of Organic Silicon Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Part 1, Chapter
5.
(7) Yamamoto, Y.; Shimizu, H.; Hamada, Y. J . Organomet. Chem.
1996, 509, 119.
(8) Yamamoto, Y.; Matui, C. Organometallics 1997, 16, 2204.
(9) Yamamoto, Y.; Shimizu, H.; Matui, C.; Chinda, M. Main Group
Chemistry 1996, 1, 409.
(10) Preliminary results on the reactions of acetals with reagent 1a
have been reported. See: Ohshita, J .; Iwata, A.; Tang, H.; Yamamoto,
Y.; Matui, C.; Kunai, A. Chem. Lett. 2001, 740.
(6) Ohshita, J .; Iwata, A.; Kanetani, F.; Kunai, A.; Yamamoto, Y.;
Matui, C. J . Org. Chem. 1999, 64, 8024.
10.1021/jo020019f CCC: $22.00 © 2002 American Chemical Society
Published on Web 06/12/2002
5170
J . Org. Chem. 2002, 67, 5170-5175

Ring-Opening Reactions with Halosilane Equivalents
TABLE 1. Rea ction s of Alk a n on e Aceta l Rin gs w ith 1
Equ iv of Rea gen t 1a a
SCHEME 1
went ring-opening reactions to give the corresponding
siloxyethyl enol ethers 3c (75%), 3d (62%), and 3e (72%),
respectively. Traces of 1,2-bis(trimethylsiloxy)ethane and
1-iodo-2-(trimethylsiloxy)ethane were detected by GC/MS
analysis in these reactions. The reaction of cyclohexanone
propylene acetal (2f), which bears an unsymmetrical
acetal ring, led to preferential cleavage on the less
hindered C-O bond to give an 87/13 mixture of 3f-1 and
3f-2 in 84% yield.
In the reaction of 2d , the products were obtained as a
mixture of (E)-3d and (Z)-3d (80/20), whose ratio was
determined on the basis of integrated ratios of proton
1
signals in H NMR spectra. Their configurations around
CdC double bonds could be confirmed by NOESY experi-
ments. For the major component, clear NOEs were
observed between a signal due to vinylmethyl protons (δ
1.56, d) and signals due to methyl (δ 1.03, t) and
methylene (δ 2.14, q) protons in an ethyl group, respec-
tively. On the other hand, the vinylmethyl protons (δ
1.66, d) of the minor component showed NOE with
protons in an OCH2CH2OSi unit, but not with the ethyl
protons. The reaction of 2e with 1a afforded also a
mixture of 3e-1, (E)-3e-2, and (Z)-3e-2 (60/30/10), and
the assignment of E/ Z for 3e-2 was similarly made by
NOESY measurements: NOEs were observed between
signals of i-Pr and Me(-Vi) groups in (E)-3e-2 and
between those of H(-Vi) and Me(-Vi) groups in (Z)-
3e-2.
Strangely, six-membered ring acetals did not produce
enol ethers. Thus, the reaction of cyclohexanone tri-
methylene acetal (2g) with 1a would give a 40/60 mixture
of 1,3-bis(trimethylsiloxy)propane (3g-1) and 1-iodo-3-
(trimethylsiloxy)propane (3g-2) in 64% yield, although
no products due to the cyclohexyl moiety were found in
the volatile products. Moreover, attempted reaction of the
parent ring compound, 1,3-dioxolane, with 1a was unsuc-
cessful.
These reactions may be initiated by silylation on one
of two oxygen atoms forming a ring-opened cationic
species (A), as shown in Scheme 1, and subsequent proton
elimination from A produces enol ethers 3a -e (similarly
3f). It is also possible to assume an iodosiloxy compound
(B) as the intermediate, in analogy with the reaction of
cyclic ethers,6 although we have not yet obtained evi-
dences for the formation of B in the present reactions.
Thus, the formation of 3g-1 can be understood by
assuming B: further silylation to B produces bissilylated
product 3g-1, while iodosiloxylpropane 3g-2 is produced
a
All reactions were carried out using 1 equiv of 1a in toluene
b
at 80-90 °C for 12 h. Isolated yield.
When ethylene acetals 2a -f were treated with 1a ,
preferential C-O bond cleavage took place at one of the
O-C-O bonds in the acetal ring, and the corresponding
ring-opened 2-(trimethylsiloxy)ethyl enol ethers 3a -f
were obtained in good yields, respectively. Thus, the
reaction of cyclohexanone ethylene acetal (2a ) for 12 h
gave 2-(trimethylsiloxy)ethyl 1-cyclohexenyl ether (3a ) as
the sole volatile product in 76% isolated yield. Similar
reactions of alkanone dimethyl acetals with Me3SiI in the
presence of hexamethyldisilazane, which give the corre-
sponding methyl vinyl ethers, have been reported previ-
ously.11 Recently, we reported that a 1:2 mixture of
Me3SiNEt2 and allyl bromide (reagent 1a ′) acts as a
synthetic equivalent of Me3SiBr,6,7,9 and the reactions
with cyclic ethers, such as tetrahydrofuran and tetrahy-
dropyran, give ring-opened products, R-bromo-ω-tri-
methylsiloxyalkanes. However, the acetal ring of 2a did
not react with 1a ′.
Treatment of 2-methylcyclohexanone ethylene acetal
(2b) that has an unsymmetrically substituted cyclohex-
ane ring with 1a gave a mixture of double-bond isomers,
2-methyl- and 6-methyl-1-cyclohexenyl ethers 3b-1 and
3b-2, respectively, in a ratio of 59/41 in 75% combined
yield. Ethylene acetals of cyclopentanone (2c), 3-pen-
tanone (2d ), and 4-methyl-2-pentanone (2e) also under-
(11) Hosomi, A.; Iijima, S.; Sakurai, H. Tetrahedron Lett. 1982, 23,
547.
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Iwata et al.
TABLE 2. Rea ction s of P h en yl-Su bstitu ted Aceta l Rin gs
w ith Rea gen t 1a a
TABLE 3. Rea ction s of Oxa zolid in e Rin gs w ith 1 Equ iv
of Rea gen t 1a a
a
All reactions were carried out using 1 equiv of 1a in toluene.
b
a
Isolated yield.
Reactions were carried out in toluene under the following
conditions: (A) 1a /4 ) 2/1, 12 h; (B) 1a /4 ) 1/1, 12 h; or (C) 1a /4
) 1/1, 48 h. Isolated yield. c Benzophenone was also obtained as
b
the coproduct in 67,d 75,e and 70%f yields, respectively.
(70%). These compounds 6b and 6c were also given by
the ring-opening iodosilation of propylene oxide with 1a .
In this reaction, 6c was obtained as the major product
(6b/6c ) 8/92), in contrast to the reaction of cyclic acetal
4e.
from A, as discussed later. A failure to isolate a coun-
terpart of 3g, possibly cyclohexylidene iodide or cyclo-
hexanone, is presumably due to further reactions such
as acid-catalyzed self-condensation or reaction with di-
ethylamine liberated in the reaction pathway, forming
nonvolatile products. The iodide B may be in equilibrium
with A and seems to be formed only from trimethylene
acetal 2g and not from ethylene acetals due to steric
hindrance. Deprotonation from A thus proceeds in cases
of ethylene acetals to give enol ethers.
Rea ction s of P h en yl-Su bstitu ted Aceta l Rin gs
w ith Rea gen t 1a . Table 2 summarizes results for the
reactions of cyclic acetals 4a -e bearing phenyl group(s)
on the ring with reagent 1a . The reactions were carried
out at 80-90 °C in a manner similar to that described
above. In all cases, iodosiloxyalkanes and/or bis(siloxy)-
alkanes were obtained in good yields. Thus, when ben-
zaldehyde ethylene acetal (4a ) was treated with 2 equiv
of 1a for 12 h, 1,2-bis(trimethylsiloxy)ethane (5) was
isolated in 79% yield as the sole volatile product. Ben-
zylidene iodide, which is expected to be formed along with
5, was not detected by GLC analysis of the reaction
mixture. This is presumably due to the same reason
discussed in Scheme 1 before.
In the reaction of acetophenone ethylene acetal (4b)
with 2 equiv of 1a for 12 h, an enol ether that can be
generated was not detected in the reaction mixture, but
an 80/20 mixture of 5 and 1-iodo-2-(trimethylsiloxy)-
ethane (6a ) was isolated in 61% total yield. The reaction
of benzophenone ethylene acetal (4c) with 1 equiv of 1a
for 12 h gave 6a as the main product in 62% yield,
together with 67% yield of benzophenone, while similar
reaction of benzophenone trimethylene acetal (4d ) for 48
h gave 1-iodo-3-(trimethylsiloxy)propane (3g-2) and ben-
zophenone in 71 and 75% isolated yields, respectively.
In the reaction of benzophenone acetal 4e with a methyl
substituent on the ring for 48 h, silylation occurred on
the less hindered oxygen atom to give an 83/17 mixture
of iodosiloxypropanes 6b and 6c (73%) and benzophenone
These results can be understood by analogy with the
reactions of acetal 2. As illustrated in the bottom part of
Scheme 1, two pathways (a and b) from a cation A′ may
compete, and their ratio seems to depend on the bulkiness
of the substituents. In the case of benzaldehyde ethylene
acetal (R ) H), addition of an iodide anion to the sp2
carbon in A′ is possible to give an iodosiloxy intermediate
B′ (path b), from which bissiloxyethane 5 is produced.
On the other hand, benzophenone acetal (R ) Ph) do not
form B′ due to steric hindrance, and the iodide anion
attacks preferentially on the less hindered ethylene
carbon to liberate 6a and benzophenone (path a ). Ac-
etophenone acetal (R ) Me) undergoes both reactions
through a and b and results in a mixture of 6a and 5.
Rea ction s of Oxa zolid in e Rin gs w ith Rea gen t 1a .
The reactivity of a series of 2,2-dialkyl-1,3-oxazolidines
7a -d with 1a was also examined. The results are
summarized in Table 3. The reaction of 7a with 1a at
room temperature gave an 81/19 isomeric mixture of
N-[2-(trimethylsiloxy)ethyl]cyclohexanimine (8a ) and a
simple N-trimethylsilylated product 8a ′ in 89% combined
yield, while heating 7a and 1a at 80-90 °C for 5 h led to
the exclusive formation of 8a as the sole product in 83%
yield, suggesting that 8a ′ is a primary product, which
then isomerizes to 8a . The isomerization may proceed
via an intermediate C, as indicated in Scheme 2, details
of which are discussed below.
To confirm isomerization pathways, we carried out
related experiments. When allyl bromide was used
instead of MeI in reagent 1a as the halogen source
(reagent 1a ′), the reaction of 7a at 80-90 °C proceeded
less selectively to give a 63/37 mixture of 8a and 8a ′ in
85% yield, while the reaction of 7a with trimethylchlo-
rosilane in ether under reflux gave a 69/31 ratio of 8a
and 8a ′ in 82% yield. When the isolated mixture (69/31)
was heated at 100 °C overnight, the mixture was
5172 J . Org. Chem., Vol. 67, No. 15, 2002

Ring-Opening Reactions with Halosilane Equivalents
TABLE 4. Rea ction s of Aceta l Rin gs w ith Rea gen t 1ba
SCHEME 2
recovered in 92% yield with no noticeable change in the
ratio (71/29). This clearly indicates that the isomerization
of 8a ′ to 8a does not proceed by a simple thermal process
but needs some interaction with iodosilane or its equiva-
lent, as indicated in Scheme 2.
As can be seen in Table 3, the reactions of other
oxazolidines, 7b and 7c with 1a , also proceeded quite
smoothly. Thus, the reactions of 7b and 7c went to
completion at room temperature within 2 h to give
respective ring-opened imines 8b (82%) and 8c (73%) as
the sole products. The higher reactivity of oxazolidines
7a -c compared to that of ethylene acetals may be
understood by the formation of iminium ions that are
more stable than oxonium ions, as represented with C
in Scheme 2. The silylated iminium salt C further
converts to an imine with a loss of the trimethylsilyl
group, which is presumably released as iodosilane.
On the other hand, the reaction of N-methylated
oxazolidine 7d at 80-90 °C for 5 h produced enamine
8d in 72% yield. In this reaction, a similar iminium
intermediate C′ may also be produced, but C′ prefers
proton elimination, since its N-methyl group is hard to
leave compared with the trimethylsilyl group in C.
Rea ction s of Aceta l Rin gs w ith Rea gen t 1b. Unlike
the reaction with reagent 1a , a completely different type
of product was obtained in the reaction of cyclohexanone
ethylene acetal (2a ) with reagent 1b. This is in marked
contrast to the previous observation that both of 1a and
1b produced similar ring-opened iodosiloxyalkanes upon
reactions with cyclic ethers.6
a
Reactions were carried out in a 1:1 ratio of 1b/acetal in toluene
b
at 80-90 °C. In most cases, Et3SiOSiEt3 was obtained as the
coproduct in nearly quantitative yield. c Isolated yield. Pd(acac)2/
d
dppe was used instead of PdCl2.
SCHEME 3
As shown in Table 4, the reaction of 2a with 1 equiv of
1b produced a dimeric compound, 2-iodoethyl 6-(1-
cyclohexenyl)hexanoate (9a ), in 63% isolated yield, to-
gether with an 85% yield of Et3SiOSiEt3 (run 1). When
Pd(acac)2/dppe was used as the catalyst, in place of PdCl2
of reagent 1b, the yield of 9a increased to 73%. In these
reactions, no enol ethers analogous to 3a were detected
in the reaction mixtures by GLC analysis. When allyl
bromide was used instead of MeI in 1b, an 80/20 mixture
of bromoester 9b-1 and its dehydrogenated product 9b-2
was obtained in 79% combined yield after distillation (run
2), and the products could be separated by recycling GPC.
Similar reaction of acetal 2b with 1b proceeded regio-
selectively to give also the dimeric product, 2-iodoethyl
2-methyl-6-(2-methyl-1-cyclohexenyl)hexanoate (9c, 76%),
and Et3SiOSiEt3 (98%) (run 3).
with 1b gave deprotected benzophenone (10a ) in 87 and
82% yields, respectively, along with high yields of Et3-
SiOSiEt3. Deprotection of the acetal moiety also pro-
ceeded for ethylene acetals of phenyl styryl ketone and
distyryl ketone (4f and 4g) to give the corresponding free
ketones 10b and 10c in 74 and 80% yields, respectively.
Although a pathway leading to dimeric product 9a from
2a is uncertain at present, we tentatively assume 2-(1-
cyclohexenyl)cyclohexanone ethylene acetal (11) as an
intermediate (Scheme 3), which is possibly produced from
2a by acid-catalyzed condensation. If this is the case, Pd-
assisted C-C bond cleavage on the acetal carbon of 11
may follow to produce a π-allyl intermediate D, which
then reacts with HI to give 9a . The Pd-assisted cleavage
of C-C bonds adjacent to a C-O unit has been reported.12
To check this possibility, we prepared acetal 11 by aldol
condensation of cyclohexanone followed by acetalization
and examined the reaction with 1b. As expected, the
reaction of 11 with 1 equiv of 1b gave 9a in 43% yield.
On the other hand, the reaction of 11 with pure Et3SiI
On the other hand, attempted reactions of other
alkanone acetals 2c, 2d , and 2f with 1b gave complex
mixtures, from which no main products were separated.
In contrast, deprotection reaction of acetal rings pro-
ceeded cleanly for diaryl-substituted acetals (runs 4-7).
Thus, the reactions of benzophenone acetals 4c and 4d
J . Org. Chem, Vol. 67, No. 15, 2002 5173

Iwata et al.
2H), 0.12 (s, 9H); 13C NMR (CDCl3) δ 154.48, 93.85, 67.37,
61.46, 27.78, 23.49, 22.87, 22.72, -0.38; GC/MS m/z 214 (M+),
199 (M+ - Me). Anal. Calcd for C11H22O2Si: C, 61.63; H, 10.34.
Found: C, 61.51; H, 10.49.
alone gave a quantitative yield of a deacetalized product,
2-(1-cyclohexenyl)cyclohexanone, without formation of 9a ,
suggesting that the presence of a Pd catalyst is essential
for production of 9a .
Deprotection reactions of diaryl-substituted acetals
with 1b might proceed in manners similar to those with
1a , but no products derived from acetal rings would be
detected in the volatile products. It should be stressed
again that hexaethyldisiloxane is always obtained in high
yields, and no silicon units are incorporated into the
products from acetal rings. These facts suggest that some
followup reactions with remaining iodosilane occur in the
present system to make the reaction more complicated.
Rea ction of 4c w ith Me3SiNEt2/MeI. A solution of di-
ethylaminotrimethylsilane (5.95 g, 41.0 mmol), 4c (5.79 g, 40.8
mmol), and methyl iodide (12.2 g, 86.1 mmol) in 20 mL of
toluene was treated as described above. The products were
distilled to give benzophenone (2.57 g, 14.1 mmol, 67%) and
6a (3.19 g, 13.1 mmol, 62%). For 6a : bp 70-71 °C/ 25 mmHg;
1
IR (neat) 1103 cm-1; H NMR (CDCl3) δ 3.80 (t, J ) 6.8 Hz,
2H), 3.18 (t, J ) 6.8 Hz, 2H), 0.11 (s, 9H); 13C NMR (CDCl3) δ
63.79, 6.55, -0.44; GC/MS m/z 229 (M+ - Me). Anal. Calcd
for C5H13IOSi: C, 24.60; H, 5.37. Found: C, 24.39; H, 5.33.
Rea ction of 7a w ith Me3SiNEt2/MeI. A solution of di-
ethylaminotrimethylsilane (21.2 g, 146 mmol), 7a (19.0 g, 135
mmol), and methyl iodide (20.8 g, 146 mmol) in 100 mL of
toluene was treated for 5 h as described above, and then
triethylamine (16.0 g, 158 mmol) was added. The products
were distilled to give 8a (23.9 g, 112 mmol, 83%), bp 65-68
Con clu sion s
We studied the reactivity of two types of iodosilane
equivalent reagents, 1a and 1b, toward acetal and 1,3-
oxazolidine rings. Specific reactions proceeded depending
on the reagents and structures of substrates. With
reagent 1a , ethylene acetals and 1,3-oxazolidines bearing
dialkyl substituents on the ring underwent ring-opening
deprotosilation reactions, giving rise to the formation of
siloxyethyl enol ethers and siloxyethylimines (or enam-
ines) bearing a silyl-protected hydroxylethyl group, re-
spectively, providing one-step synthetic routes to the
products. On the other hand, the reactions of alkanone
acetals with reagent 1b gave rather complex results.
Among them, the reaction of cyclohexanone ethylene
acetal with 1b gave a dimeric product in good yield, which
could be explained by assuming acid-catalyzed condensa-
tion of the starting acetal and subsequent Pd-catalyzed
ring-opening reaction.
In marked contrast to these alkyl derivatives, those
with diaryl substituents on the acetal ring led to a
significant change in the reaction course, i.e., reactions
with both 1a and 1b gave deprotected ketones in high
yields. In the reaction with 1a , iodosiloxyalkanes were
also obtained as coproducts. This seems to be of impor-
tance as a method not only for deprotection of aromatic
acetals under neutral conditions but also for preparation
of R,ω-iodosiloxyalkanes, which are useful in synthetic
chemistry as bifunctional materials.
°C/1 mmHg. For 8a : IR (neat) 1665, 1108 cm-1 1H NMR
;
(CDCl3) δ 3.77 (t, J ) 6.5 Hz, 2H), 3.43 (t, J ) 6.5 Hz, 2H),
2.27-2.26 (m, 4H), 1.78-1.60 (m, 6H), 0.09 (s, 9H); 13C NMR
(CDCl3) δ 174.53, 62.91, 52.49, 39.94, 29.14, 27.66, 26.94, 26.00,
-0.47; GC/MS m/z 213 (M+), 198 (M+ - Me). Anal. Calcd for
C
11H23NOSi: C, 61.91; H, 10.86; N, 6.56. Found: C, 61.52; H,
10.85; N, 6.51.
Rea ction of 7d w ith Me3SiNEt2/MeI. A solution of di-
ethylaminotrimethylsilane (14.7 g, 101 mmol), 7d (15.5 g, 100
mmol), and methyl iodide (14.6 g, 103 mmol) in 100 mL of
toluene was treated as described above. The products were
distilled to give 8d (16.3 g, 72.0 mmol, 72%), bp 75 °C/1 mmHg.
1
For 8d : IR (neat) 1641, 1097 cm-1; H NMR (CDCl3) δ 4.41
(brs, 1H), 3.58 (t, J ) 6.5 Hz, 2H), 3.08 (t, J ) 6.5 Hz, 2H),
2.63 (s, 3H), 2.15-2.00 (m, 4H), 1.70-1.60 (m, 2H), 1.55-1.45
(m, 2H), 0.09 (s, 9H); 13C NMR (CDCl3) δ 143.99, 96.45, 59.93,
52.99, 38.32, 26.92, 24.63, 23.46, 22.86, -0.53; GC/MS m/z 227
(M+), 212 (M+ - Me). Anal. Calcd for C12H25NOSi: C, 63.38;
H, 11.08; N, 6.16. Found: C, 63.32; H, 10.86; N, 6.14.
Rea ction of 2a w ith Et3SiH/MeI(P d (a ca c)2/d p p e). A
mixture of triethylsilane (3.08 g, 26.6 mmol), 2a (3.75 g, 26.4
mmol), methyl iodide (7.94 g, 55.9 mmol), palladium acetyl-
acetonate (40 mg, 0.13 mmol), and 1,2-bis(diphenylphosphino)-
ethane (60 mg, 0.15 mmol) was stirred at 80-90 °C for 5 h.
The products were fractionally distilled with a Ku¨gel-Rohr
distillation apparatus to give hexaethyldisiloxane (2.68 g, 10.9
mmol, 82%) and 9a (3.37 g, 9.64 mmol, 73%). For 9a : bp 170
°C/1 mmHg (oven temp); IR (neat) 1740 cm-1; 1H NMR (CDCl3)
δ 5.36 (s, 1H), 4.31 (t, J ) 6.8 Hz, 2H), 3.28 (t, J ) 6.8 Hz,
2H), 2.32 (t, J ) 7.5 Hz, 2H), 2.00-1.89 (m, 6H), 1.67-1.50
(m, 6H), 1.43-1.27 (m, 4H); 13C NMR (CDCl3) δ 173.15, 137.67,
120.79, 64.31, 37.78, 34.13, 28.79, 28.23, 27.24, 25.22, 24.82,
23.01, 22.58, 0.50; GC/MS m/z 350 (M+), 223 (M+ - I). Anal.
Calcd for C14H23IO2: C, 48.01; H, 6.62. Found: C, 48.31; H,
6.68.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Methyl iodide and allyl bromide
were dried over P2O5 and distilled just before use. Toluene was
dried over sodium and distilled just before use. All reactions
were carried out under an atmosphere of dry argon. Typical
procedures for the reactions with reagents 1a and 1b are
shown below. The ratio of isomers was determined by integra-
Rea ction of 2b w ith Et3SiH/MeI(P d Cl2). A mixture of
triethylsilane (3.52 g, 30.3 mmol), 2b (4.56 g, 29.2 mmol),
methyl iodide (6.74 g, 47.5 mmol), and palladium dichloride
(20 mg, 0.11 mmol) was treated as described above. The
products were distilled to give hexaethyldisiloxane (3.66 g, 14.9
mmol, 98%) and 9c (4.20 g, 11.1 mmol, 76%). For 9c: bp 170-
1
tion of H NMR signals of the mixture.
Rea ction of 2a w ith Me3SiNEt2/MeI. A solution of di-
ethylaminotrimethylsilane (5.95 g, 41.0 mmol), 2a (5.79 g, 40.8
mmol), and methyl iodide (12.2 g, 86.1 mmol) in 20 mL of
toluene was stirred at 80-90 °C for 12 h. The resulting
ammonium salts were filtered off, and the solvent was
evaporated. The residue was fractionally distilled under
reduced pressure to give 3a (6.63 g, 31.0 mmol, 76%), bp 73-
1
175 °C/1 mmHg (oven temp); IR (neat) 1740 cm-1; H NMR
(CDCl3) δ 4.32 (t, J ) 6.8 Hz, 2H), 3.28 (t, J ) 6.8 Hz, 2H),
2.50-2.40 (m, 1H), 2.00-1.20 (m, 16H), 1.57 (s, 3H), 1.15 (d,
J ) 7.0 Hz, 3H); 13C NMR (CDCl3) δ 176.20, 129.93, 125.92,
64.22, 39.46, 33.70, 33.24, 31.81, 29.51, 28.06, 27.28, 23.50,
23.40, 19.02, 17.03, 0.58; GC/MS m/z 378 (M+), 251 (M+ - I).
Anal. Calcd for C16H27IO2: C, 50.80; H, 7.19. Found: C, 50.60;
H, 7.20.
1
75 °C/1 mmHg. For 3a : IR (neat) 1667, 1107 cm-1; H NMR
(CDCl3) δ 4.58 (s, 1H), 3.81 (t, J ) 5.1 Hz, 2H), 3.69 (t, J ) 5.1
Hz, 2H), 2.15-2.02 (m, 4H), 1.68-1.62 (m, 2H), 1.55-1.49 (m,
Rea ction of 2a w ith Et3SiH/AllylBr (P d Cl2). A mixture
of triethylsilane (4.81 g, 41.5 mmol), 2a (5.94 g, 41.8 mmol),
allyl bromide (8.01 g, 66.2 mmol), and palladium dichloride
(12) (a) Tamaru, Y. J . Organomet. Chem. 1999, 576, 215. (b)
Nishimura, T.; Matsumura, S.; Maeda, Y.; Uemura, S. Tetrahedron
Lett. 2002, 43, 3037.
5174 J . Org. Chem., Vol. 67, No. 15, 2002

Ring-Opening Reactions with Halosilane Equivalents
(20 mg, 0.11 mmol) was treated for 10 h. The products were
distilled to give hexaethyldisiloxane (4.13 g, 16.7 mmol, 81%)
and an 80/20 mixture of 9b-1 and 9b-2 (4.95 g, 16.4 mmol,
79%), bp 150 °C/1 mmHg (oven temp). Recycling GPC separa-
tion of the mixture eluting with benzene afforded 9b-1 and
(CDCl3) δ 173.15, 142.37, 128.32, 128.21, 125.62, 63.53, 35.64,
33.93, 30.98, 28.73, 28.60, 24.69; GC/MS m/z 298 (M+ for 79Br).
Anal. Calcd for C14H19BrO2: C, 56.20; H, 6.40. Found: C, 56.04;
H, 6.55.
1
9b-2 in pure forms. For 9b-1: IR (neat) 1738 cm-1; H NMR
Ack n ow led gm en t. We thank Sankyo Kasei Co.,
Ltd., Tokuyama Corp., and Sumitomo Electric Industry
for financial support.
(CDCl3) δ 5.36 (s, 1H), 4.36 (t, J ) 6.8 Hz, 2H), 3.50 (t, J ) 6.8
Hz, 2H), 2.33 (t, J ) 7.5 Hz, 2H), 2.00-1.80 (m, 6H), 1.67-
1.40 (m, 6H), 1.40-1.25 (m, 4H); 13C NMR (CDCl3) δ 173.27,
137.62, 120.76, 63.53, 37.76, 34.03, 28.75, 28.75, 28.21, 27.21,
25.19, 24.77, 22.99, 22.56; GC/MS m/z 302 (M+ for 79Br). Anal.
Calcd for C14H23BrO2: C, 55.45; H, 7.65. Found: C, 55.63; H,
7.81. For 9b-2: IR (neat) 1738 cm-1; 1H NMR (CDCl3) δ 7.19-
7.14 (m, 2H), 7.08-7.05 (m, 3H), 4.26 (t, J ) 6.3 Hz, 2H), 3.38
(t, J ) 6.3 Hz, 2H), 2.51 (t, J ) 7.7 Hz, 2H), 2.24 (t, J ) 7.5
Hz, 2H), 1.61-1.50 (m, 4H), 1.32-1.16 (m, 2H); 13C NMR
Su p p or tin g In for m a tion Ava ila ble: Detailed experi-
mental procedures and spectral and analytical data for prod-
ucts. This material is available free of charge via the Internet
at http://pubs.acs.org.
J O020019F
J . Org. Chem, Vol. 67, No. 15, 2002 5175