Lewis acid-catalyzed three-component condensation reactions of aldehydes, alkoxysilanes, and allenylsilanes: Synthesis of α-propargyl ethers

Article abstract of DOI:10.1016/S0040-4020(01)01145-0

Lewis acid-catalyzed reaction of acetals with allenylsilanes and the three-component reactions of aldehydes, alkoxysilanes, and allenylsilanes are described. Both reactions are strongly dependent on the substituent at the α-position of allenylsilanes. Allenylsilanes having bulky substituents such as the tert-butyl and isopropyl groups result in the corresponding α-propargyl ethers in high yields, whereas allenylsilanes having the methyl and ethyl groups afford not only the corresponding α-propargyl ethers in low yield but also cyclopropyl ketones and α,β-unsaturated ketones as by-products.

Full text of DOI:10.1016/S0040-4020(01)01145-0

TETRAHEDRON
Pergamon
Tetrahedron 58 52002) 245±252
Lewis acid-catalyzed three-component condensation reactions
of aldehydes, alkoxysilanes, and allenylsilanes:
synthesis of a-propargyl ethers
Lui Niimi, Shuichi Hiraoka and Tsutomu Yokozawap
Department of Applied Chemistry, Kanagawa University, Kanagawa-ku, 3-27-1 Rokkakubashi, Yokohama 221-8686, Japan
Received 17 September 2001;accepted 16 November 2001
AbstractÐLewis acid-catalyzed reaction of acetals with allenylsilanes and the three-component reactions of aldehydes, alkoxysilanes, and
allenylsilanes are described. Both reactions are strongly dependent on the substituent at the a-position of allenylsilanes. Allenylsilanes
having bulky substituents such as the tert-butyl and isopropyl groups result in the corresponding a-propargyl ethers in high yields, whereas
allenylsilanes having the methyl and ethyl groups afford not only the corresponding a-propargyl ethers in low yield but also cyclopropyl
ketones and a,b-unsaturated ketones as by-products. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
would be more versatile, because the carbon±carbon triple
bond is easily transformed to other functional groups11 and
cross-linking would occur by not only photochemical reac-
tion12 but also bidentate metals that form acetylides.13 It has
been reported that the reactions of allenylsilanes with
aldehydes and acetals in the presence of TiCl4 yield
a-propargyl alcohols and ethers, respectively.14 However,
there is no report about the three-component condensation
of aldehydes, alkoxysilanes, and allenylsilanes, which will
afford the a-propargyl ethers in one-pot and can be applied
to the synthesis of polyethers having the propargyl side
chains.
Three-component condensation reactions make two bonds
in one-pot and yield a broad variety of compounds by
changing three kinds of reactants. These reactions are
recently applied to combinatorial synthesis.1 There are
documented examples of the three-component condensation
reactions of aldehydes, alkoxysilanes, and a variety of silyl
nucleophiles, which yield ethers,2 homoallyl ethers,3
a-alkoxynitriles,4 and b-alkoxyketones.5 Furthermore,
these reactions with amine derivatives instead of alkoxy-
silanes produce N-homoallylcarbamates,6 pyridine and
quinoline derivatives,7 b-amino esters,8a b-amino ketones,8b
and d-lactams.9 We have applied the three-component ether
synthesis to polycondensation, in which the polyether back-
bone is constructed from dialdehydes and diol disilyl ethers,
and functional side chains are simultaneously introduced to
polyethers by silyl nucleophiles. The polyethers with the
allyl,10 cyano,4 and keto5a,b side chains have been synthe-
sized by the three-component polycondensations using
allylsilane, cyanosilane, and silyl enol ethers, respectively
5Scheme 1). Polyethers having the propargyl side chains
On the basis of the reported reaction mechanism of the
Lewis acid-catalyzed three-component condensations,5a
the condensation of aldehydes, alkoxysilanes, and allenyl-
silanes would also take place via similar reaction mechan-
ism 5Scheme 2). Aldehyde ®rst reacts with 1 equiv. of
alkoxysilane to give acetal;1:1 mixture of aldehyde and
acetal in the initial reaction mixture. Acetal next reacts
with allenylsilane to yield the desired a-propargyl ether,
as well as the regeneration of 1 equiv. of alkoxysilane. If
the aldehyde reacts fast with allenylsilane, the adduct
obtained would not further react with alkoxysilane.
Scheme 1.
Keywords: Lewis acid-catalyst;allenylsilane; a-propargyl ether.
Corresponding author. Tel.: 181-45-481-5661x3151;fax: 181-45-491-
7915;e-mail: yokozawa@cc.kanagawa-u.ac.jp
p
Scheme 2.
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020501)01145-0

246
L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
Scheme 3.
Therefore, this reaction should satisfy the following three
requirements: 51) acetalization and the reaction of acetal
with allenylsilane proceed by the same Lewis acid;52)
aldehyde reacts with alkoxysilane faster than with allenyl-
silane;53) allenylsilane reacts with acetal faster than with
aldehyde. The reported reactions of allenylsilanes by
14
TiCl4 would not be applied to this three-component
condensation, because allenylsilane reacts both with alde-
hyde and acetal, and it would be dif®cult to form acetal by
TiCl4. Accordingly, another Lewis acid reaction system
should be developed for the three-component condensation
of aldehydes, alkoxysilanes, and allenylsilanes.
Scheme 4.
In this paper, we report the triphenylmethyl 5trityl) per-
chlorate-catalyzed condensations of aldehydes, alkoxy-
silanes, and allenylsilanes, where a-propargyl ethers were
obtained in one-pot in good yields when the allenylsilanes
possessed the bulky alkyl groups at the a-position. First, we
studied the reactions of a variety of allenylsilanes with an
acetal which is an intermediate in the three-component
condensation. Next, we checked whether the reaction of
allenylsilanes with aldehydes proceeded under the same
conditions of the reactions with acetals, and then studied
the three-component condensations of aldehydes, alkoxy-
silanes, and allenylsilanes 5Scheme 3).
with various allenylsilanes 3a±f were carried out in the
presence of trityl perchlorate 5TrClO4) trimethylsilyl
tri¯uoromethanesulfonate 5tri¯ate) 5TMSOTf), tin 5II)
tri¯ate 5Sn5OTf)2), and scandium tri¯ate 5Sc5OTf)3) in
CH2Cl2, respectively 5Table 1). The yields of a-propargyl
ethers 4 were strongly dependent on the substituents at the
a-position of 3. Allenylsilanes 3e and 3f having bulky
substituents resulted in 4 in high yields with 5 mol% of
TrClO4;TMSOTf, Sn5OTf) 2, and Sc5OTf)3 gave 4 in
moderate yields, respectively. On the other hand, the reac-
tion of unsubstituted 3a with 5 hardly proceeded with
5 mol% of TrClO4. Even increase in the amount of the
catalyst up to 50 mol% afforded not only 4 in low yields
but also trimethylsilyl-substituted a-propargyl ether 6,
which may be formed by the elimination of proton from
b-silyl vinyl cationic intermediate 9 in Scheme 4. Further
in this reaction, methyl triphenylmethyl ether 5Tr±OMe)15
2. Result and discussion
2.1. Reaction of acetal with allenylsilanes
At ®rst, the reactions of benzaldehyde dimethyl acetal 5
Table 1. Reaction of acetal 5 with allenyltrimethyl silanes 3
R in 3
Lewis acid 5mol%)
Conditions
Yield 5%)a
4
6
7
8
H:3a
Me:3b
Et:3c
TrClO4 550)
TMSOTf 5100)
TMSOTf 5100)
TrClO4 55)
TMSOTf 55)
Sn5OTf)2 55)
Sc5OTf)3 55)
TrClO4 55)
2208C, 2 h
3
14
4
99
81
59
60
85b
20
0
0
0
0
0
0
0
0
31
6
0
0
0
0
0
0
23
38
0
0
0
2788C, 1.5 h
2788C, 1.5 h
2508C, 9.5 h
2508C, 8 h and 2208C, 13 h
2508C, 9 h; 2208C, 13 h and 08C, 9 h
2508C, 4 h
But:3e
0
0
SiMe2Ph:3f
2208C, 3.5 h
The reaction was carried out in CH2Cl2 5[5]0ˆ[3]0ˆ0.5 M).
a
Isolated yield.
Isolated yield after desilylation of the mixture 6 and 4f.
b

L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
247
analogy with the rearrangement of enol benzylic ethers by
triisobutylaluminium.19 Enone 8 would be formed by the
tandem reaction of the desired product 4 with further
1 equiv. of 5. Thus, 4 undergoes [212] cycloaddition with
5 activated by TMSOTf to give 12,20 followed by ring-
opening isomerization and hydrolysis to give 8.
Scheme 5.
In this case, steric hindrance by the tert-butyl and phenyl-
dimethylsilyl groups from C-1 of the allenes would retard
the rate of intramolecular cyclization of 90 and undergo very
rapid elimination of the trimethylsilyl group in order to
relieve steric congestion to yield 4. Furthermore, the steric
hindrance would also retard the [212] cycloaddition of 4
with 5 leading to 8.
was also obtained in 23% yield based on 5, implying that
TrClO4 did not work well as a catalyst. Accordingly,
TMSOTf was used for the reaction of 3b, 3c with 5,
because TMSOTf is easily regenerated after the reaction
of 3 with the silyl oxonium tri¯ate generated from 5 and
TMSOTf. However, the reaction of 3b, 3c with 5 hardly
proceeded with 5 mol% of TMSOTf. Even addition of
1 equiv. of TMSOTf resulted in the corresponding 4 in
poor yield, and surprisingly cyclopropyl ketones 716 and
a,b-unsaturated ketones 8 were obtained as major
products.
2.2. Reaction of aldehyde with allenylsilanes
As mentioned in Section 1, it is necessary for the three-
component condensation that allenylsilanes react with
acetals faster than with aldehydes or does not react with
aldehydes under the conditions where allenylsilanes react
with acetals. Therefore, we tested the reaction of benz-
aldehyde 1a with 3e or 3f which reacted with 5 to give 4
in high yields 5Scheme 5). Fortunately, the reaction of 1a
with 3e did not proceed in the presence of TrClO4 at 250
and even at 2208C. On the other hand, 3f smoothly reacted
with 1a under the same conditions to give a-propargyl alco-
hol 14 in 77% yield after the removal of the silyl groups by
the treatment with tetrabuthylammonium ¯uoride 5TBAF).
These results show that bissilylallene 3f possesses higher
reactivity toward electrophiles than monosilylallene 3e.
Scheme 4 accounts for the formation of 7 and 8 from the
reaction of 5 and 3. As Danheiser explained the formation of
a dihydrofurane product from the reaction of an aldehyde
with an allenylsilane in the presence of TiCl4,14a dihydro-
pyranium 10 is formed by the intramolecular cyclization of
intermediate cation 90, which is subjected to a rapid 1,2-
trimethylsilyl shift,17,18 thus establishing an equilibrium
with an isomeric vinyl cation 9. Since 10 is an activated
enol benzyl ether, 10 undergoes rearrangement via the
proposed intermediate benzyl cation 11 to afford 7, in
Table 2. Three-component condensation reaction of benzaldehyde 1a, methoxytrimethylsilane 2a, and allenyltrimethylsilane 3
R in 3
Me:3b
Lewis acid
Temperature 58C)
Time 5h)
Yield 5%)a
4
7
8
TrClO4
220
220
278
220
220
250
220
220
1.0
1.0
1.5
1.0
21.0
8.5
1.5
8.0
8b
12b
17b
5b
67
93
0
0
9b
16b
4b
8b
0
0
0
0
TMSOTf
TMSOTtc
TrClO4
15b
0
Et:3c
Pri:3d
But:3e
3e
0
0
0
0
81
60d,e
SiMe2Ph:3f
5RˆSiMe3/SiMe2Phˆ52/48)f
3f
TMSOTf
TrClO4
220
278
278
5.0
7.0
1.0
49d
0
0
0
0
0
0
5RˆSiMe3/SiMe2Phˆ50/50)f
3f
70d
5RˆSiMe3/SiMe2Phˆ54/46)f
46d,h
3fg
The reaction was carried out in CH2Cl2 5[1a]0ˆ[2a]0ˆ[3]0ˆ0.5 M).
a
Isolated yield.
b
1H NMR yield.
100 mol% of TMSOTf was used.
Isolated yield after desilylation.
c
d
e
Dimethylphenyl-1-propynyl silane was also obtained in 15% yield.
The ratio was determined by 1H NMR.
1.5 equiv. of 3f was used.
f
g
h
1-Phenyl-3-butyn-1-ol 514) was also obtained in 16% yield.

248
L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
Table 3. Three-component condensation reaction of carbonyl compounds 1, alkoxytrimethylsilanes 2, and 1-But-allenyltrimethylsilane 3e
Entry
1
1
2
Conditions
2508C, 8.5 h
Yield 5%)a
MeOSiMe3:2a
93
2
3
1a
1a
2508C, 15 h
2208C, 42 h
84
91
4
2a
2508C, 25 h and 2208C, 8.5 h
64
5
6
7
2a
2b
2a
2508C, 8.5 h
89
38
12
2208C, 20 h
2208C, 14 h;0 8C, 7 h and rt 22 h
The reaction was carried out with 5 mol% of TrClO4 in CH2Cl2 5[1]0ˆ[2]0ˆ[3e]0ˆ0.5 M).
a
Isolated yield.
Consequently, 3e 5RˆBut) was suited for the three-compo-
nent reaction because 3e reacted only with acetal even in the
presence of aldehyde.
tion of aliphatic aldehyde or ketone proceeded slowly, and
the corresponding 4 was obtained in low yields even at
higher temperature and longer time 5entries 6, 7).
2.3. Reaction of aldehyde, alkoxysilane, and
allenylsilanes
3. Conclusions
Three-component reaction of aldehydes 1, alkoxysilanes 2,
and allenylsilanes 3 was studied. The substituents at the
a-position of 3 were found to affect the reaction strongly;
bulky substituents such as the tert-butyl and isopropyl
groups made the three-component reaction proceed
smoothly to give a-propargyl ethers 4 in good yields,
whereas the methyl- and ethyl-substituted 3 gave cyclo-
propyl ketones and a,b-unsaturated ketones as by-products.
The reaction developed here would apply to the three-
component polycondensation of dialdehydes, diol disilyl
ethers, and 3 having bulky substituents, which would yield
functional polyethers having the propargyl side chains in
one-pot. The study along this line is in progress.
To establish the optimal condition for the three-component
condensation of 1, 2, and 3, the reactions of benzaldehyde
1a, methoxytrimethylsilane 2a, and a variety of 3 were
carried out 5Table 2). In analogy with the reaction of acetal
5 with a variety of 3, allenylsilanes 3b, 3c 5RˆMe, Et)
resulted in 4 and 8 in low yields, as well as polymeric
compounds, whereas 3d, 3e, and 3f 5RˆPri, But, PhMe2Si)
having bulky substituents did 4 in good yields, respectively.
In the reactions of 1a, 2a and 3f at 2208C, the yield of 4 was
moderate irrespective of the catalysts TrClO4 or TMSOTf,
and dimethylphenyl-1-propynylsilane was obtained as a
by-product.15a The reaction at 2788C depressed this side
reaction to increase the yield of 4. There was no selectivity
of the silyl groups which were eliminated during reaction;
this might be because there was no p-face selectivity at the
g-carbon of 3f, if 3f undergoes anti S0E reaction like allyl-
silanes.21 Me3Si-substituted-4 and PhMe2Si-substituted-4
were obtained in the ratio about 1:1. It should be noted
that 3f, which can react not only with acetal but also with
the aldehyde, gave the three-component condensed product
4 without the formation of the adduct 14 of 3f and aldehyde
1a. This implies that the reaction of 3f with acetal is faster
than that with aldehyde. In the reaction using 1.5 equiv. of
3f, however, 14 was obtained in 16% yield to decrease the
yield of 4.
4. Experimental
4.1. General
All reactions were carried out under argon atmosphere.
Column chromatography was carried out on Merck silica
gel 60 using hexane and a hexane/diethyl ether gradient as
eluent. The purity of new compounds was con®rmed by
1
elemental analysis. H NMR spectra were obtained on a
JEOL A-500 and FX-200 operating in the pulsed Fourier
transform 5FT) modes with tetramethylsilane 5TMS) as an
internal standard. 13C NMR spectra were also obtained on a
JEOL A-500 and FX-200 operating in the FT modes with
TMS as an internal standard. IR spectra were recorded on a
Hitachi 270-30 and JASCO FT/IR-410. Isolation of some
products was carried out with a recycling preparative high-
performance liquid chromatography 5HPLC) Japan Ana-
lytical Industry LC-908 5eluent, chloroform) using two
Tosoh TSK gel G2000H columns. Elemental analyses
were performed by Perkin-Elmer 2400 II CHN. Commer-
cially available dry dichloromethane and tetrahydrofuran
were used as received. Benzaldehyde 1a, p-anisaldehyde,
With the optimized conditions in hand, we next carried out
the reaction of a variety of 1, 2, and 3e. The results are
summarized in Table 3. In the reaction of 1a, 2, and 3e,
silyl ethers 2a, 2b of primary alcohols resulted in the corre-
sponding 4 in good yields at 2508C, but the reaction of
secondary 2c required raising reaction temperature for
obtaining 4 in high yield 5entries 1±3). Regarding the
substituent effects of aromatic aldehydes, the electron-
withdrawing group was more effective for obtaining 4
than the electron-donating group 5entry 4 vs. 5). The reac-

L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
249
4-chlorobenzaldehyde, propionaldehyde, isobutyraldehyde,
cyclohexanone, methoxytrimethylsilane 2a, benzaldehyde
dimetyl acetal 5, and TMSOTf were used as received.
TrClO4 was prepared from triphenylmethanol and 70%
perchloric acid according to the reported procedure.22
Octyloxytrimethylsilane 2b was prepared from octanol,
1,1,1,3,3,3-hexamethyldisilazane 5HMDS), and a catalytic
amount of chlorotrimethylsilane. Cyclohexyloxytrimethyl-
silane was prepared from cyclohexanol, HMDS, and a
catalytic amount of saccharin.23 Trimethylsilylallene 3a
was prepared from 3-trimethylsilyl-2-propyn-1-ol and
o-nitrobenzenesulfonylhydrazide in the presence of tri-
phenylphosphine and diethylazodicarboxylate in CH2Cl2.24
a-Substituted trimethylsilylallene 3b±3e were prepared
from the corresponding organoheterocuprates and 3-tri-
methylsilyl-2-propyn-1-mesylates.25
NMR 5500 MHz, CDCl3) d 7.38±7.31 5br s, 5H), 4.31 5dd,
Jˆ6.3, 6.8 Hz, 1H), 3.28 5s, 3H), 2.68 5ddd, Jˆ2.8, 6.8,
16.8 Hz, 1H), 2.56 5ddd, Jˆ2.8, 6.3, 16.8 Hz, 1H), 1.98 5t,
Jˆ2.8 Hz, 1H); 13C NMR 5125 MHz, CDCl3) d 140.5,
128.4, 128.1, 126.7, 82.0, 80.9, 69.9, 57.0, 28.0;IR 5neat)
3293, 2935, 2824, 2121, 1602, 1103, 756, 701 cm21. Anal.
Calcd for C11H12O: C, 82.46;H, 7.55. Found: C, 82.86;H,
7.50. 6: 1H NMR 5500 MHz, CDCl3) d 7.36±7.24 5m, 5H),
4.29 5dd, Jˆ6.3, 6.8 Hz, 1H), 3.28 5s, 3H), 2.72 5dd, Jˆ6.3,
16.6 Hz, 1H), 2.55 5dd, Jˆ6.8, 16.6 Hz, 1H), 0.11 5s, 9H);
13C NMR 5125 MHz, CDCl3) d 140.7, 128.3, 128.0, 126.8,
103.5, 86.7, 82.3, 57.1, 29.5, 0.04;IR 5neat) 2959, 2179,
1249, 1104, 758, 700 cm21. Anal. Calcd for C14H20OSi: C,
72.36;H, 8.67. Found: C, 72.29;H, 8.86.
4.1.3. Reaction of 5 with 3b. A solution of TMSOTf
51.8 mL, 10.0 mmol) in CH2Cl2 55.0 mL) was added to a
¯ask, followed by cooling to 2788C. A solution of 5
51.52 g, 10.0 mmol) and 3b 51.26 g, 10.0 mmol) in CH2Cl2
55.0 mL) was added at 2788C. The solution was stirred at
2788C for 1.5 h. The reaction mixture was quenched with
saturated NaHCO3 solution, followed by dilution with
diethyl ether. The organic layer was washed with water
and dried over MgSO4. The solution was ®ltered and
concentrated in vacuo. The residue was puri®ed by column
chromatography on silica gel, followed by HPLC to afford
5-methoxy-5-phenyl-2-pentyne 4b 50.240 g, 14%), methyl
2-phenyl-1-trimethylsilylcyclopropyl ketone 7b 50.711 g,
31%), and 3-52-methoxy-2-phenylethyl)-4-phenyl-3-buten-
2-one 8b 50.324 g, 23%). 4b: 1H NMR 5200 MHz, CDCl3) d
7.32 5br s, 5H), 4.25 5dd, Jˆ6.1, 6.8 Hz, 1H), 3.25 5s, 3H),
2.69±2.41 5m, 2H), 1.74 5t, Jˆ2.6 Hz, 3H); 13C NMR
550 MHz, CDCl3) d 141.0, 128.3, 127.8, 126.7, 82.5, 77.3,
75.5, 56.9, 28.3, 3.5;IR 5neat) 3022, 2974, 2914, 1599,
1095, 696 cm21. Anal. Calcd for C121H14O: C, 82.72;H,
8.10. Found: C, 82.43;H, 8.26. 7b: H NMR 5500 MHz,
CDCl3) d 7.28±7.19 5m, 5H), 2.58 5dd, Jˆ6.4, 8.8 Hz,
1H), 2.16 5s, 3H), 1.71 5dd, Jˆ4.7, 8.8 Hz, 1H), 1.42 5dd,
Jˆ4.7, 6.4 Hz, 1H), 20.19 5s, 9H); 13C NMR 5125 MHz,
CDCl3) d 209.3, 137.9, 129.8, 128.1, 127.0, 31.6, 30.9, 27.5,
14.8, 20.8;IR 5neat) 2954, 2898, 1672, 1603, 1252, 771,
700 cm21. Anal. Calcd for C14H20OSi: C, 72.36;H, 8.67.
Found: C, 72.05;H, 8.74. 8b: 1H NMR 5200 MHz, CDCl3) d
7.55 5s, 1H), 7.48±7.22 5m, 10H), 4.42 5dd, Jˆ5.4, 8.6 Hz,
1H), 3.16 5s, 3H), 3.00 5dd, Jˆ8.6, 13.6 Hz, 1H), 2.82 5dd,
Jˆ5.4, 13.6 Hz, 1H), 2.43 5s, 3H); 13C NMR 5125 MHz,
CDCl3) d 200.5, 142.0, 141.6, 139.3, 135.5, 129.3, 128.5,
128.4, 128.3, 127.5, 126.6, 82.3, 56.9, 35.5, 26.3;IR 5neat)
3022, 2974, 2920, 1659, 1101, 732, 690 cm21. Anal. Calcd
for C19H20O2: C, 81.40;H, 7.19. Found: C, 81.26;H, 7.28.
4.1.1. Preparation of 3f. THF 533 mL) was added to the
¯ask which was charged with lithium 50.84 g, 121.6 mmol),
followed by cooling the solution to 08C.26 Dimethylphenyl-
silyl chloride 59.3 mL, 55.4 mmol) was added to the ¯ask at
08C. The resulting red solution was transferred by cannula
into a slurry of CuCN 54.95 g, 55.2 mmol) in THF 510 mL)
at 2788C. The reaction mixture was stirred for 10 min and
warmed up to 2208C over 30 min, and then cooled again to
2788C. BF3±OEt227,28 57.0 mL, 55.2 mmol) was added and
stirred for 10 min at 2788C, and a solution of 3-trimethyl-
silyl-2-propyn-1-mesylate 510.36 g, 50.2 mmol) in THF
550 mL) was added. After stirring for 3 h at 2788C, the
reaction mixture was poured into a saturated NH4Cl solu-
tion, and diluted with hexane. The black emulsion was
®ltered through Celite. The organic layer was washed with
saturated NH4Cl solution, and the aqueous layer was
extracted with hexane. The organic layer was combined
and dried over MgSO4. The solution was ®ltered and
concentrated in vacuo. The residue was puri®ed by column
chromatography on silica gel, followed by HPLC to afford
3f 51.70 g, 14%): 1H NMR 5500 MHz, CDCl3) d 7.55±7.49
5m, 2H), 7.36±7.30 5m, 3H), 3.94 5s, 2H), 0.41 5s, 6H), 0.00
5s, 9H); 13C NMR 5125 MHz, CDCl3) d 212.6, 139.0, 134.0,
129.1, 127.7, 59.4, 46.3, 20.1, 21.5;IR 5neat) 3069, 2958,
2898, 1912, 1543, 1249, 776, 699 cm21. Anal. Calcd for
C14H22Si2: C, 68.22;H, 9.00. Found: C, 68.01;H, 8.70.
4.1.2. Reaction of 5 with 3a. A round-bottomed ¯ask,
equipped with a three-way stopcock, was charged with
TrClO4 50.017 g, 0.05 mmol) and purged with argon.
CH2Cl2 51.0 mL) was added to the ¯ask, followed by
cooling the solution to 2208C. A solution of 5 50.152 g,
1.0 mmol) in CH2Cl2 50.5 mL) was added at 2208C. After
5 min, a solution of 3a 50.112 g, 1.0 mmol) in CH2Cl2
50.4 mL) was added. After 3 h, a solution of TrClO4
50.153 g, 0.45 mmol) in CH2Cl2 51.5 mL) was added at
2208C. The solution was stirred at 2208C for 2 h. The
reaction mixture was quenched with a few drops of ammo-
niacal methanol. The reaction mixture was diluted with
diethyl ether and washed with water. The organic layer
was dried over MgSO4. The solution was ®ltered and
concentrated in vacuo. The residue was puri®ed by column
chromatography on silica gel, followed by HPLC to afford
methyl triphenylmethyl ether15 50.062 g, 23%), 4-methoxy-
4-phenyl-1-butyne 4a 50.005 g, 3%), and 4-methoxy-4-
4.1.4. Reaction of 5 with 3c. In the presence of TMSOTf
51.62 mL, 9.0 mmol), the reaction of 5 51.37 g, 9.0 mmol)
with 3c 51.26 g, 9.0 mmol) was performed in a similar
manner as above to yield 1-methoxy-1-phenyl-3-hexyne
4c 50.058 g, 4%), ethyl 2-phenyl-1-trimethylsilylcyclopro-
pyl ketone 7c 50.117 g, 6%), 2-52-methoxy-2-phenylethyl)-
1
1-phenyl-1-pentene-3-one 8c 50.471 g, 38%). 4c: H NMR
5500 MHz, CDCl3) d 7.38±7.23 5m, 5H), 4.26 5dd, Jˆ6.0,
6.3 Hz, 1H), 3.27 5s, 3H), 2.64 5dd, Jˆ6.0, 16.5 Hz, 1H),
2.50 5dd, Jˆ6.3, 16.5 Hz, 1H), 2.13 5q, Jˆ7.5 Hz, 2H), 1.07
5t, Jˆ7.5 Hz, 3H); 13C NMR 5125 MHz, CDCl3) d 141.1,
128.3, 127.9, 126.8, 83.6, 82.7, 75.8, 57.1, 28.4, 14.2, 12.5;
1
phenyl-1-trimethylsilyl-1-butyne 6 50.047 g, 20%). 4a: H

250
L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
IR 5neat) 2975, 2932, 1600, 1102, 757, 700 cm21. Anal.
Calcd for C13H16O: C, 82.94;H, 8.57. Found: C, 82.53;H,
8.75. 7c: 1H NMR 5500 MHz, CDCl3) d 7.28±7.20 5m, 5H),
2.51 5q, Jˆ7.4 Hz, 2H), 2.49 5dd, Jˆ5.8, 10.6 Hz, 1H), 1.73
5dd, Jˆ4.6, 10.6 Hz, 1H), 1.39 5dd, Jˆ4.6, 5.8 Hz, 1H), 1.10
5t, Jˆ7.4 Hz, 3H), 20.19 5s, 9H); 13C NMR 5125 MHz,
CDCl3) d 211.9, 138.1, 129.8, 128.1, 127.0, 33.2, 31.0,
30.7, 14.2, 8.5, 20.7;IR 5neat) 3061, 3028, 2974, 2899,
1673, 1603, 1249, 765, 700 cm21. Anal. Calcd for
C15H22OSi: C, 73.11;H, 9.00. Found: C, 73.14;H, 9.00.
1.0 mmol) with 3f 50.247 g, 1.0 mmol) was performed in a
similar manner to the reaction of 5 with 3a. The solution
was stirred at 2208C for 6.5 h. The reaction mixture was
quenched with a few drops of ammoniacal methanol. After
puri®cation by column chromatography, the residue was
treated with 1.0 M TBAF in THF 51.5 mL, 1.5 mmol) to
1
afford 1-phenyl-3-butyn-1-ol 14 50.112 g, 77%): H NMR
5500 MHz, CDCl3) d 7.43±7.27 5m, 5H), 4.88 5t, Jˆ6.3 Hz,
1H), 2.65 5dd, Jˆ2.3, 6.3 Hz, 2H), 2.49±2.28 5br, 1H), 2.07
5t, Jˆ2.3 Hz, 1H); 13C NMR 5125 MHz, CDCl3) d 142.4,
128.5, 128.0, 125.7, 80.7, 72.3, 71.0, 29.5;IR 5neat) 3385,
3294, 3031, 2911, 2121, 1600, 1051, 755, 701 cm21. Anal.
Calcd for C10H10O: C, 82.16;H, 6.90. Found: C, 82.18;H,
7.00.
1
8c: H NMR 5500 MHz, CDCl3) d 7.52 5s, 1H), 7.44 5d,
Jˆ7.5 Hz, 2H), 7.38±7.22 5m, 8H), 4.40 5dd, Jˆ5.6,
8.6 Hz, 1H), 3.16 5s, 3H), 3.01 5dd, Jˆ8.6, 13.3 Hz, 1H),
2.84 5dd, Jˆ5.6, 13.3 Hz, 1H), 2.80 5q, Jˆ7.3 Hz, 2H), 1.15
5t, Jˆ7.3 Hz, 3H); 13C NMR 5125 MHz, CDCl3) d 203.4,
142.1, 140.1, 139.1, 135.7, 129.3, 128.40, 128.36, 127.6,
126.7, 82.4, 57.0, 35.8, 31.2, 8.8;IR 5neat) 3028, 2977,
2936, 1667, 1625, 1102, 754, 700 cm21. Anal. Calcd for
C20H22O2: C, 81.60;H, 7.53. Found: C, 81.24;H, 7.42.
4.2. General procedure for the reaction of 1, 2, and 3
A round-bottomed ¯ask, equipped with a three-way stop-
cock, was charged with TrClO4 50.017 g, 0.05 mmol) and
purged with argon. CH2Cl2 51.0 mL) was added to the ¯ask,
followed by cooling the solution to 220 or 2508C. A
solution of 1 51.0 mmol) and 2 51.0 mmol) in CH2Cl2
50.5 mL) was added at 220 or 2508C. After 5 min, a solu-
tion of 3 51.0 mmol) in CH2Cl2 50.5 mL) was added. The
solution was stirred at 220 or 2508C. The reaction mixture
was quenched with a few drops of ammoniacal methanol.
The solvent was evaporated and the residue was puri®ed by
column chromatography on silica gel to afford 4.
4.1.5. Reaction of 5 with 3e. In the presence of TrClO4
50.051 g, 0.15 mmol), the reaction of 5 50.459 g, 3.0
mmol) with 3e 50.505 g, 3.0 mmol) was performed in a
similar manner to the reaction of 5 with 3a. The solution
was stirred at 2508C for 9.5 h. The reaction mixture was
quenched with a few drops of ammoniacal methanol. The
solvent was evaporated and the residue was puri®ed by
column chromatography on silica gel to afford 1-methoxy-
5,5-dimethyl-1-phenyl-3-hexyne 4e 50.630 g, 99%): 1H
NMR 5200 MHz, CDCl3) d 7.32 5br s, 5H), 4.23 5dd,
Jˆ6.3, 7.2 Hz, 1H), 3.27 5s, 3H), 2.66 5dd, Jˆ6.3,
16.3 Hz, 1H), 2.46 5dd, Jˆ7.2, 16.3 Hz, 1H), 1.13 5s, 9H);
13C NMR 550 MHz, CDCl3) d 141.1, 128.1, 127.8, 126.9,
90.9, 82.8, 74.8, 57.0, 31.2, 28.2, 27.3;IR 5neat) 2966, 2931,
2866, 1601, 1104, 753, 697 cm21. Anal. Calcd for C15H20O:
C, 83.29;H, 9.32. Found: C, 83.06;H, 9.48.
4.2.1. 1-Methoxy-5-methyl-1-phenyl-3-hexyne 4d. 0.113 g,
67%. H NMR 5200 MHz, CDCl3) d 7.33 5br s, 5H), 4.25
1
5dd, Jˆ6.3, 6.6 Hz, 1H), 3.27 5s, 3H), 2.75±2.39 5m, 3H),
1.09 5d, Jˆ6.6 Hz, 6H); 13C NMR 550 MHz, CDCl3) d
141.0, 128.2, 127.8, 126.8, 88.0, 82.7, 75.6, 57.0, 28.3,
23.2, 20.5;IR 5neat) 3032, 2968, 2931, 1601, 1103, 756,
700 cm21. Anal. Calcd for C14H18O: C, 83.12;H, 8.97.
Found: C, 82.74;H, 9.04.
4.1.6. Reaction of 5 with 3f. In the presence of TrClO4
50.008 g, 0.025 mmol), the reaction of
5 50.076 g,
4.2.2. Dimethylphenyl-1-propynylsilane. 0.013 g, 15%.
1H NMR 5500 MHz, CDCl3) d 7.64±7.62 5m, 2H), 7.37±
7.36 5m, 3H), 1.93 5s, 3H), 0.39 5s, 6H); 13C NMR
5125 MHz, CDCl3) d 137.7, 133.8, 129.4, 128.0, 105.0,
82.0, 5.1, 20.6;IR 5neat) 3069, 2960, 2917, 2183, 1250,
730, 700 cm21. Anal. Calcd for C11H14Si: C, 75.79;H, 8.10.
Found: C, 75.96;H, 7.80.
0.5 mmol) with 3f 50.123 g, 0.5 mmol) was performed in a
similar manner to the reaction of 5 with 3a. The solution
was stirred at 2208C for 3.5 h. The reaction mixture was
quenched with a few drops of ammoniacal methanol. The
solvent was evaporated and the residue was puri®ed by
column chromatography on silica gel, followed by HPLC
to afford a mixture of 6 and 1-5dimethylphenylsilyl)-4-
methoxy-4-phenyl-1-butyne 4f. 4f: 1H NMR 5500 MHz,
CDCl3) d 7.55±7.52 5m, 2H), 7.36±7.30 5m, 8H), 4.32
5dd, Jˆ6.3, 7.2 Hz, 1H), 3.28 5s, 3H), 2.79 5dd, Jˆ6.3,
16.8 Hz, 1H), 2.62 5dd, Jˆ7.2, 16.8 Hz, 1H), 0.34 5s, 6H);
13C NMR 5125 MHz, CDCl3) d 141.3, 138.2, 134.5, 130.0,
129.1, 128.7, 128.6, 127.6, 106.1, 85.4, 83.0, 57.8, 30.2,
0.00;IR 5neat) 3067, 2959, 2932, 2906, 2179, 1589, 1249,
1104, 754, 700 cm21. Anal. Calcd for C19H22OSi: C, 77.50;
H, 7.53. Found: C, 77.54;H, 7.61. The mixture was
dissolved in THF 52.0 mL), and 1.0 M TBAF in THF
50.5 mL, 0.5 mmol) was added. After 1 min, the solution
was ®ltered through silica gel. The solvent was evaporated
and the residue was puri®ed by column chromatography on
silica gel to afford 4a 50.068 g, 85%).
4.2.3. 5,5-Dimethyl-1-octyloxy-1-phenyl-3-hexyne. 0.265 g,
84%. H NMR 5500 MHz, CDCl3) d 7.35±7.21 5m, 5H),
1
4.32 5t, Jˆ6.8 Hz, 1H), 3.40±3.29 5m, 2H), 2.63 5dd, Jˆ
6.8, 16.3 Hz, 1H), 2.44 5dd, Jˆ6.8, 16.3 Hz, 1H), 1.59±1.54
5m, 2H), 1.38±1.21 5m, 10H), 1.14 5s, 9H), 0.87 5t, Jˆ
7.0 Hz, 3H); 13C NMR 5125 MHz, CDCl3) d 141.9, 128.0,
127.7, 126.7, 90.6, 81.1, 75.1, 69.4, 31.8, 31.2, 29.9, 29.4,
29.3, 28.5, 27.3, 26.2, 22.6, 14.1;IR 5neat) 2928, 2857,
1602, 1102, 755, 700 cm21. Anal. Calcd for C22H34O: C,
84.02;H, 10.90. Found: C, 83.78;H, 11.17.
4.2.4. 1-Cyclohexyloxy-5,5-dimethyl-1-phenyl-3-hexyne.
0.258 g, 91%. H NMR 5500 MHz, CDCl3) d 7.38±7.22
1
5m, 5H), 4.51 5dd, Jˆ6.3, 7.3 Hz, 1H), 3.27±3.21 5m, 1H),
2.57 5dd, Jˆ7.3, 16.5 Hz, 1H), 2.40 5dd, Jˆ6.3, 16.5 Hz,
1H), 2.00±1.92 5m, 1H), 1.81±1.63 5m, 3H), 1.52±1.27
5m, 3H), 1.23±1.11 5m, 12H); 13C NMR 5125 MHz,
4.1.7. Reaction of 1a with 3f. In the presence of TrClO4
50.017 g, 0.05 mmol), the reaction of 1a 50.106 g,

L. Niimi et al. / Tetrahedron 58 ,2002) 245±252
251
5c) Niimi, L.;Serita, K.;Hiraoka, S.;Yokozawa, T.
Tetrahedron Lett. 2000, 41, 7075.
CDCl3) d 142.8, 128.0, 127.4, 126.6, 90.3, 78.0, 75.59,
75.55, 33.3, 31.6, 31.2, 29.1, 27.3, 25.8, 24.2, 24.0;IR
5neat) 2931, 2857, 1601, 1452, 1089, 755, 700 cm21
Anal. Calcd for C20H28O: C, 84.45;H, 9.92. Found: C,
84.81;H, 10.13.
.
7. Kobayashi, S.;Ishitani, H.;Nagayama, S. Chem. Lett. 1995,
423.
8. 5a) Kobayashi, S.;Araki, M.;Yasuda, M. Tetrahedron Lett.
1995, 36, 5773. 5b) Manabe, K.;Kobayashi, S. Org. Lett.
1999, 1, 1965.
4.2.5. 1-Methoxy-1-24-methoxyphenyl)-5,5-dimethyl-3-
hexyne. 0.156 g, 64%. 1H NMR 5500 MHz, CDCl3) d
7.25 5d, Jˆ8.8 Hz, 2H), 6.88 5d, Jˆ8.8 Hz, 2H), 4.19 5dd,
Jˆ5.8, 7.2 Hz, 1H), 3.81 5s, 3H), 3.25 5s, 3H), 2.64 5dd,
Jˆ5.8, 16.1 Hz, 1H), 2.44 5dd, Jˆ7.2, 16.1 Hz, 1H), 1.13
5s, 9H); 13C NMR 5125 MHz, CDCl3) d 159.2, 133.1, 128.0,
113.5, 90.8, 82.3, 74.9, 56.8, 55.3, 31.2, 28.2, 27.3;IR 5neat)
2967, 2857, 1601, 1452, 1089, 755, 700 cm21. Anal. Calcd
for C16H22O2: C, 78.01;H, 9.00. Found: C, 78.12;H, 8.96.
9. Kobayashi, S.;Akiyama, R.;Moriwaki, M. Tetrahedron Lett.
1997, 38, 4819.
10. Yokozawa, T.;Takenoya, K. React. Funct. Polym. 1996, 30,
251.
11. A review: The Chemistry of the Carbon±Carbon Triple Bond;
Patai, S., Ed.;Wiley: New York, 1978.
12. Shimokawa, T.;Suzuki, T.;Nishikubo, T. Polym. J. 1994, 26,
967.
13. 5a) HuÈttel, R.;Forkl, H. Chem. Ber. 1972, 105, 2913.
5b) Yamazaki, H.;Wakatsuki, Y. J. Organomet. Chem.
1977, 139, 157. 5c) Suzuki, H.;Itoh, K.;Ishii, Y.;Simon,
K.;Ibers, J. A. J. Am. Chem. Soc. 1976, 98, 8494.
5d) Fahey, D. R. J. Org. Chem. 1972, 37, 4471.
14. 5a) Danheiser, R. L.;Carini, D. J.;Kwasigroch, C. A. J. Org.
Chem. 1986, 51, 3870. 5b) Danheiser, R. L.;Carini, D. J.
J. Org. Chem. 1980, 45, 3925. 5c) Danheiser, R. L.;
Kwasigroch, C. A.;Tsai, Y.-M. J. Am. Chem. Soc. 1985,
107, 7233. 5d) Archibald, S. C.;Fleming, I. Tetrahedron
Lett. 1993, 34, 2387. 5e) Ohno, M.;Yamamoto, Y.;Shirasaki,
Y.;Eguchi, S. J. Chem. Soc., Perkin Trans. 1 1993, 263.
5f) Marshall, J. A.;Maxson, K. J. Org. Chem. 2000, 65, 630.
15. 5a) Hollis, T. K.;Boshich, B. J. Am. Chem. Soc. 1995, 117,
4570. 5b) Smith, H. A.;Smith, R. J. J. Am. Chem. Soc. 1948,
70, 2400.
4.2.6.
1-24-Chlorophenyl)-1-methoxy-5,5-dimethyl-3-
hexyne. 0.224 g, 89%. 1H NMR 5500 MHz, CDCl3) d
7.32 5d, Jˆ8.5 Hz, 2H), 7.27 5d, Jˆ8.5 Hz, 2H), 4.21 5dd,
Jˆ5.6, 7.6 Hz, 1H), 3.26 5s, 3H), 2.64 5dd, Jˆ5.6, 16.5 Hz,
1H), 2.44 5dd, Jˆ7.6, 16.5 Hz, 1H), 1.13 5s, 9H); 13C NMR
5125 MHz, CDCl3) d 139.5, 133.4, 128.7, 128.3, 91.3, 82.0,
74.2, 57.0, 31.1, 28.0, 27.3;IR 5neat) 2967, 2929, 1598,
1107, 825 cm21. Anal. Calcd for C15H19ClO: C, 71.84;H,
7.64. Found: C, 72.14;H, 7.94.
4.2.7. 2,2-Dimethyl-6-octyloxy-3-octyne. 0.015 g, 38%. 1H
NMR 5500 MHz, CDCl3) d 3.55 5dt, Jˆ6.5, 9.3 Hz, 1H),
3.40 5dt, Jˆ6.7, 9.3 Hz, 1H), 3.28±3.23 5m, 1H), 2.38 5dd,
Jˆ5.5, 16.5 Hz, 1H), 2.22 5dd, Jˆ6.8, 16.5 Hz, 1H), 1.22±
1.71 5m, 14H), 1.19 5s, 9H), 0.93 5t, Jˆ7.3 Hz, 3H), 0.88 5t,
Jˆ7.0 Hz, 3H); 13C NMR 5125 MHz, CDCl3) d 90.1, 79.8,
1
16. After desilylation of 7, its H NMR spectrum was identical
75.6, 70.0, 31.8, 31.3, 30.2, 29.9, 29.5, 29.3, 26.9, 26.2,
with that of the reported 1-phenyl-2-acetylcyclopropane:
5a) Cavallo, A. S.;Isarno, T. Tetrahedron Lett. 1999, 40,
1579. 5b) Sasaki, T.;Eguchi, S.;Ohno, M. Bull. Chem. Soc.
Jpn 1980, 53, 1469. 5c) Kessar, S. V.;Singh, P.;Kaur, N. P.;
Chawla, U.;Shukla, K.;Aggarwal, P.;Venugopal, D. J. Org.
Chem. 1991, 56, 3908.
21
23.9, 22.6, 14.1, 9.6;IR 5neat) 2927, 2857, 1111 cm
Anal. Calcd for C19H34O: C, 81.13;H, 12.86. Found: C,
81.06;H, 13.14.
.
4.2.8. 1-24,4-Dimethyl-2-pentynyl)-1-methoxycyclohex-
ane. 0.025 g, 12%. H NMR 5500 MHz, CDCl3) d 3.21 5s,
1
17. For examples of internal cyclization via the reaction of
allenylsilanes with electrophiles, see: 5a) Danheiser, R. L.;
Carini, D. J.;Basak, A. J. Am. Chem. Soc. 1981, 103, 1604.
5b) Danheiser, R. L.;Carini, D. J.;Fink, D. M.;Basak, A.
Tetrahedron 1983, 39, 935. 5c) Danheiser, R. L.;Fing, D. M.
Tetrahedron Lett. 1985, 26, 2513. 5d) Danheiser, R. L.;Stoner,
3H), 1.87 5s, 2H), 1.75±1.69 5m, 2H), 1.61±1.42 5m, 8H),
1.20 5s, 9H); 13C NMR 5125 MHz, CDCl3) d 91.1, 74.9,
74.8, 48.6, 33.2, 31.2, 27.9, 27.4, 25.7, 21.8;IR 5neat)
2967, 2932, 2861, 1455, 1081 cm21. Anal. Calcd for
C14H24O: C, 80.71;H, 11.61. Found: C, 80.52;H, 11.37.
E. J.;Koyama, H.;Yamashita, D. S.;Klade, C. A.
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18. Stang, P. J.;Rappaport, Z.;Hanack, M.;Subramanian, L. R.
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28. It has been reported that organo cyanocopper-tri¯uoroborane