1-methyl-1-vinyl- and 1-methyl-1-(prop-2-enyl)silacyclobutane: Reagents for palladium-catalyzed cross-coupling reactions of aryl halides

Article abstract of DOI:10.1055/s-2000-6292

1-Methyl-1-vinylsilacyclobutane (1) and 1-methyl-1(prop-2- enyl)silacyclobutane (2) undergo rapid and high yielding cross-coupling with aromatic halides. Many different substituents and patterns on the aromatic moiety are tolerated. All reactions can be r

Full text of DOI:10.1055/s-2000-6292

PAPER
999
1-Methyl-1-vinyl- and 1-Methyl-1-(prop-2-enyl)silacyclobutane: Reagents for
Palladium-Catalyzed Cross-Coupling Reactions of Aryl Halides
Scott E. Denmark,* Zhigang Wang
Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA
Fax +1(217)3333984; E-mail: denmark@scs.uiuc.edu
Received 24 January 2000; revised 23 February 2000
ing investigations were limited to the use of E and Z-2-
Abstract: 1-Methyl-1-vinylsilacyclobutane (1) and 1-methyl-1-
substituted alkenylsilanes and showed good generality. In
(prop-2-enyl)silacyclobutane (2) undergo rapid and high yielding
this disclosure we report the preparation and use of two
new reagents, 1-methyl-1-vinylsilacyclobutane (1) and 1-
cross-coupling with aromatic halides. Many different substituents
and patterns on the aromatic moiety are tolerated. All reactions can
be run at room temperature and require the presence of tetrabutyl- methyl-1-(prop-2-enyl)silacyclobutane (2) which repre-
ammonium fluoride and Pd(dba)2. Both silacyclobutanes can be
sent two new classes of alkene donors (Figure).
made in one step from commercially available precursors.
Key words: cross-coupling, organosilicon, palladium catalysis,
styrenes, alkenes
Me
Si
Si
Me
Me
1
2
Recent disclosures from these laboratories have described
the use of alkenyl-1a and arylsilacyclobutanes1b as viable
partners in palladium-catalyzed cross-coupling reactions
with aryl and alkenyl halides (Scheme 1). For alkenylsila-
cyclobutanes, the reactions are effectively promoted by
2-3 equivalents of tetrabutylammonium fluoride in the
presence of Pd(dba)2 (5 mol%) at room temperature.
Within 10 minutes to 3 hours the reactions are complete
and afford excellent yields of coupling products. Good
functional group compatibility is observed and the alk-
enyl-alkenyl cross-couplings are highly stereospecific.
For arylsilacyclobutanes, the reactions required a heteroa-
tom activating group on the silicon moiety. The aryl-aryl
cross couplings were slightly slower requiring 1-5 hours
in refluxing THF. For these reactions, the superior catalyst
is (allylPdCl)2 in combination with t-Bu3P to suppress ho-
mocoupling.
Figure Structures of 1-methyl-1-vinylsilacyclobutane (1) and 1-
methyl-1-(prop-2-enyl)silacylobutane (2)
Although the vinyl derivative 1 is a known compound2 we
found the literature procedure to be unnecessarily cum-
bersome. By adaptation of the method of Utimoto3 we
prepared 1 from simple combination of vinylmagnesium
bromide and 1-chloro-1-methylsilacyclobutane4 in 58%
yield on a 15g scale. The previously unknown propenyl
analog 2 was prepared by a similar procedure in 65%
yield. Both compounds are stable, colorless but volatile
fluids (1, bp 108-110 °C; 2, bp 124-126 °C).
The palladium catalyzed vinylation of iodoarenes was in-
vestigated first. To establish the optimal conditions for
coupling, two electronically complementary arenes were
chosen, ethyl 4-iodobenzoate (3) and 4-iodoanisole (4).
As starting point, the reaction conditions developed previ-
ously in these laboratories for substituted alkenylsilanes
were tested. The results from coupling of 1 with ester 3 are
R2
RZ
TBAF (2.0 equiv)
RZ
I
I
R4
+
Si
Pd(dba)2 (5 mol %)
THF / rt
RE
or
RE
CH3
R3
R4 = aryl or alkenyl
68 % - 95 %
Table 1 Optimization of the Coupling of 1 with 3
TBAF (3.0 equiv)
R
R
[allylPdCl]2 (2.5 mol%)
+
Si
X
Aryl
I
Aryl
(t-Bu)3P (20 mol%)
THF, reflux
X = Cl, F
71 % - 91 %
Entry 1 (Equiv) TBAF
Pd(dba)2 Time
Conver-
sion (%)
(Equiv)
(mol %)
(min)
Scheme 1
1
2
3
4
5
6
1.1
1.1
1.1
1.2
1.2
1.2
3.0
2.0
1.0
2.0
2.0
2.0
5.0
5.0
5.0
5.0
3.0
1.0
10
10
10
10
10
60
100
100
68
100
100
100
In continuation of these studies we are interested in estab-
lishing the scope of the cross coupling with respect to the
substitution on the alkenylsilane component. The forego-
Synthesis 2000, No. 7, 999–1003 ISSN 0039-7881 © Thieme Stuttgart · New York

1000
S. E. Denmark, Z. Wang
PAPER
Table 3 Survey of Cross-Coupling of 1 with Aryl Halidesa
compiled in Table 1. Under these conditions (Entry 1)
100% conversion of 3 was achieved in only 10 minutes.
Clearly 1 was extremely reactive and we were able to re-
duce the amount of promoter and catalyst significantly.
Thus with just two equivalents of TBAF and 1 mol% of
Pd(dba)2 complete consumption of 3 was accomplished in
60 minutes. The amount of silane 1 was slightly adjusted
to 1.2 equivalents based on 3 to suppress the formation of
a minor byproduct (symmetrical stilbene) which arose
from a Heck arylation subsequent to the coupling.
Aryl, R
1
TBAF Pd(dba)2 Time Prod- Yield
(Comp. No.)
(Equiv) (Equiv) (mol %) (h)
uct
(%)
4-CO2Et (3)
4-COMe (7)
4-COMe (9)b
4-NO2 (10)
4-CN (12)
4-OMe (4)
4-t-Bu (14)
3-NO2 (16)
1.2
1.2
1.2
1.2
1.2
1.5
1.2
1.2
1.2
2.0
2.0
3.0
2.0
2.0
4.5
3.0
2.0
2.0
3.0
2.0
3.0
3.0
4.5
3.0
1
1
1
1
5
8
8
11
13
6
15
17
19
93
85
75
90
87
74
80
92
90
79
86
85
70
75
86
2.5c
1
0.5d
1
The optimization of the coupling with anisole 4 was not as
straightforward. Unlike the reaction with the electron-de-
ficient arene 3, these couplings were much more sluggish
and precipitation of the palladium catalyst became a prob-
lem. The results presented in Table 2 show that no combi-
1
1
4
6
1
5e
5e
1
nation of silane, TBAF and catalyst could drive the 3-CO2Et (18)
3
1
3-CH2OH (20) 1.2
2-NO2 (22) 1.2
2-CO2Me (24) 1.2
2-Me (26)
2-OMe (28)
5e
1
7.5 21
1.5 23
14
16
10
4
reaction to completion at room temperature in a reason-
able period of time. Consequently, we examined the effect
of additives to facilitate the cross-coupling. A number of
structurally diverse phosphine ligands were tested without
success (Entries 6-8). However, the addition of 10 mol%
of triphenylarsine5 dramatically accelerated the reaction
(Entries 9, 10). In this case as well, a small amount of the
Heck reaction byproduct was observed which could be re-
moved by increasing the amount of silane to 1.5 equiva-
lent.
5e
5e
5e
5
25
27
29
31
1.2
1.5
1-napthyl-I (30) 1.2
a All reactions run on 2.0 mmol scale or larger.
b 4-Bromoacetophenone.
c 2.5 5 mol % of (allylPdCl)2 used as catalyst.
d 40 °C.
e 10 mol % of Ph3As added.
With two optimized procedures in hand, we were now in
a position to survey the generality of the vinylation with
respect to aryl electrophiles. The results of cross coupling
with 2-, 3-, and 4-substituted aryl halides are compiled in
Table 3. As expected the coupling with electron-deficient
4-substituted iodobenzenes (ester, ketone, cyano, nitro) is
rapid and high yielding with as little as 1 mol% catalyst.
Even 4-bromoacetophenone could be employed, but re-
quired the use of (allylPdCl)2 as the catalyst and 40 °C re-
action temperature. The electron rich 4-substituted cases
were slightly slower and required the addition of Ph3As as
discussed above.
Similar trends were noted in the 2- and 3-substituted cases
wherein electron-withdrawing substituents gave rise to
rapid reaction with a minimal amount of catalyst, while
the donor substituents led to significantly slower cou-
plings. The 2-substituted cases also provided insights into
the steric effect on the rate and yield of reactions. Whereas
2-nitroiodobenzene showed little steric influence com-
pared to the 3- and 4-nitro isomers (compare 10, 16, and
22) the 2-carboxy substituent had a dramatic decelerating
effect (compare 3, 18, and 24). In this case the steric effect
overrides the electronic activation as seen in the similar
rates of 24 and 2-iodotoluene (26) and 2-iodoanisole (28).
The decelerating effect of an ortho substituent was also
manifest in the coupling of 1-iodonaphthalene (30). The
functional group compatibility of this process as illustrat-
ed in these examples is noteworthy.
Table 2 Optimization of the Coupling of 1 with 4
Entry
1
TBAF Pd(dba)2 Additive
Conv. Conv.
(4 h), % (24 h),
%
(Equiv) (Equiv) (mol %) (mol %)
We briefly examined the coupling of silane 1 with alkenyl
electrophiles, (E)- and (Z)-6-iodohex-5-enol (Scheme 2).
For this purpose we found that (allylPdCl)2 was the cata-
lyst of choice. The reactions proceeded rapidly albeit in
modest yield compared to the previously reported cou-
plings of these substrates. In both cases, however the ste-
reospecificity was excellent as determined by GC
analysis.
1
2
3
1.2
2.4
4.8
1.2
1.2
1.2
1.2
1.2
1.2
1.5
3.0
6.0
12.0
3.0
2.0
3.0
3.0
3.0
3.0
4.5
5
5
5
8
5
5
5
5
5
5
–
–
–
–
43
57
56
52
79
11
18
68
72
82
62
79
29
47
71
–
4
5a
6
–
Ph3P, 10
dppp, 10
furyl3P, 10 25
Ph3As, 10 100b
Ph3As, 10 100
7
8
9
10
–
To evaluate the utility of the propenylsilacyclobutane an-
alog 2 we selected a subset of the coupling partners used
with reagent 1. From the extensive optimization of reac-
a Reaction run at 40°C.
b 3% of the Heck coupling byproduct was formed.
Synthesis 2000, No. 7, 999–1003 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
1-Methyl-1-vinyl- and 1-Methyl-1-(prop-2-enyl)silacyclobutane
1001
OH
OH
OH
O
1 (1.2 equiv)
TBAF (3.0 equiv)
Me
Me
Si
I
O
[allylPdCl]2 (2.5 mol%)
THF / rt / 1 h
Me
32 (E/Z, 100/0)
TBAF (4.0 equiv)
33 46% (E/Z, 100/0)
33 48% (E/Z, 2/98)
Me
8
+
1 (1.0 equiv)
O
+
Pd(dba)2 (1 mol %)
THF / rt
OH
I
1 (1.2 equiv)
Me
Si
I
7
TBAF (3.0 equiv)
100% conversion
8/34, 64/36
Me
[allylPdCl]2 (2.5 mol%)
THF / rt / 6 h
Me
34
32 (E/Z, 3/97)
2 (1.0 equiv)
Scheme 2
Scheme 3
tion parameters developed for the vinylations above, we In a preliminary examination, we have shown that 2 also
had an excellent starting point for the survey of various ar- undergoes rapid and highly stereospecific cross-coupling
omatic substrates. Indeed, as shown in the results in Table with alkenyl iodide (E)-42, Scheme 4. Interestingly, this
4, the only optimization that was necessary was the eval- transformation is higher yielding than the related coupling
uation of the slower acting partners 22 and 24 with regard with 1 and could be performed with Pd(dba)2 as the cata-
to the need for Ph3As as an additive. Surprisingly, these lyst.
reactions proceeded more readily than with the vinyl si-
lane 1. In fact, two of the more difficult substrates encoun-
tered in the vinylation reaction, 4 and 28, reacted much
more rapidly and without the need for Ph3As additive.
Only 24 bearing a 2-methoxycarbonyl group required the
OTHP
OTHP
2 (1.2 equiv)
TBAF (3.0 equiv)
I
Pd(dba)2 (5 mol%)
THF / rt / 12 h
Me
additive for complete reaction.
42 (E/Z, 100/0)
43 71% (E/Z, 100/0)
The unexpected increase in reaction rate for 2 compared
to 1 was quantified in a competition experiment with an
electron-deficient aryl coupling partner (Scheme 3). Com-
bination of equimolar amounts of 1, 2 and 7 in the pres-
ence of 4 equiv of TBAF and 1 mol% Pd(dba)2 afforded
the coupling products 8 and 34 in a 64/36 ratio (100% con-
version). Thus, the difference in rate between vinyl- and
prop-2-enylsilanes is somewhat substrate dependent; 1 re-
acts faster with electron-poor compared to electron-rich
aryl halides while 2 shows the opposite trend.
Scheme 4
In conclusion, we have demonstrated the synthetic utility
of vinyl and 2-propenylsilacyclobutane reagents 1 and 2.
These compounds are easily synthesized on a large scale,
and represent low molecular weight, non-toxic alterna-
tives to tin-based reagents for vinylation of aromatic and
olefinic halides. The generality of the reaction was shown
to be high with regard to aryl halide functionality and sub-
stitution pattern. Further studies on the scope of silicon-
based cross coupling reactions and origin of the rate and
stereoselectivity are in progress.
Table 4 Survey of Cross-Coupling of 2 with Aryl Halidesa
1-Methyl-1-ethenylsilacyclobutane (1)
To a solution of 1-methyl-1-chlorosilacyclobutane (28.9 g, 0.24
mol) in THF (50 mL) was added dropwise vinylmagnesium bro-
mide (290 mL, 1 M, 0.29 mol) at 0-5 °C in 60 min. The mixture was
stirred at 0-5 °C for 2 h. Then 1 M aq HCl (100 mL) was added cau-
tiously (the temperature of reaction mixture should never exceed 10
°C). The layers were separated, and the aqueous layer was extracted
by Et2O (3 î 100 mL). The combined organic layer was washed
with H2O (50 mL) aq sat. of NaHCO3 (2 î 50 mL) and brine, and
dried (Na2SO4). The solvents were removed by distillation, and
fraction distillation of the residue afforded the product; yield: 15.4
g (58%); bp 108-110 °C/760 Torr.
1H NMR (400 MHz, CDCl3): d = 6.34 (dd, J = 20.3, 14.4, 1 H), 6.06
(dd, J = 14.4, 3.7, 1 H), 5.84 (dd, J = 20.3, 3.9, 1 H), 2.10 (m, 2 H),
1.06 (m, 4 H), 0.36 (s, 3 H).
13C NMR (100.6 MHz, CDCl3): d = 138.4, 132.8, 18.3, 14.2, -1.9.
Aryl, R
1
TBAF Pd(dba)2, Time Prod- Yield
(Comp. No.) (Equiv) (Equiv) (mol %) (min) uct
(%)
4-COMe (7)
4-OMe (4)
3-NO2 (16)
3-CH2OH
(20)
2-NO2 (22)
2-CO2Me
(24)
1.2
1.2
1.2
1.2
2.0
3.0
2.0
3.0
1
5
1
5
60
10
60
10
34
35
36
37
89
85
84
87
1.2
1.2
3.0
3.0
5b
5b
240
20 h 39
38
79
78
2-OMe (28)
1-napthyl-I
(30)
1.2
1.2
3.0
3.0
5
5
60
10
40
41
73
84
a All reactions run on 2.0 mmol scale or larger.
b 10 mol % of Ph3As added.
IR (CHCl3): n = 3051 (m), 2966 (s), 2942 (s), 2930 (s), 2873 (m),
1590 (w), 1403 (s), 1251 (s), 1201 (s), 868 (s).
Synthesis 2000, No. 7, 999–1003 ISSN 0039-7881 © Thieme Stuttgart · New York

1002
S. E. Denmark, Z. Wang
PAPER
1-Methyl-1-(1’-methylethenyl)silacyclobutane (2)
3-Ethenylbenzoic Acid Ethyl Ester (19)
To a solution of 1-methyl-1-chlorosilacyclobutane (12.0 g, 0.1 mol)
in THF (15 mL) was added dropwise i-propenylmagnesium bro-
mide (120 mL, 1 M, 0.12 mol) at 0-5 °C in 60 min. The reaction
mixture was stirred at 0-5 °C for 2.5 h. Then the 1 M aq HCl solu-
tion (40 mL) was added cautiously (the temperature of the mixture
should not exceed 10 °C). The layers were separated, and the aque-
ous layer was extracted with Et2O (2 î 60 mL). The combined or-
ganic layers were washed with H2O (50 mL), aq sat. of NaHCO3 (2
î 50 mL) and brine (2 î 50 mL) and dried (Na2SO4). The solvents
were removed by distillation, and fraction distillation afforded the
product 8.2 g (65%); bp 124-126 °C/760 Torr; Rf 0.77 (hexane);
GC: tR 5.10 min (HP-5, 100 °C, 15 psi).
1H NMR (400 MHz, CDCl3): d = 5.67 (m, = CHaHb, 1 H), 5.40
(m, =CHaHb, 1 H), 2.09 (m, CCH2C, 2 H), 1.93 (m, CCH3, 3 H),
1.13 (m, SiCH2, 2 H), 1.01 (m, SiCH2, 2 H), 0.36 (s, SiCH3, 3 H).
13C NMR (100.6 MHz, CDCl3): d = 146.8 (C=CH2), 126.1 (SiC=),
22.3 (CCH2C), 18.4 (CCH3), 13.6 (SiCH2), -2.2 (SiCH3).
Following the General Procedure, 1 (2.4 mmol, 1.2 equiv), a solu-
tion of TBAF in THF (4 mL, 1 M, 2 equiv), 3-iodobenzoic acid eth-
yl ester (552.1 mg, 2.0 mmol, 1 equiv) and Pd(dba)2 (34.5 mg, 0.03
equiv) were stirred at r.t. for 60 min. Et2O (10 mL) was added and
the mixture was stirred for another 5 min and filtered through silica
gel. Purification by silica gel column chromatography (hexane/
EtOAc, 50:1) and Kugelrohr distillation afforded 316.6 mg (90%)
of 19 as colorless oil; bp 160 °C/1.1 Torr; Rf 0.12 (hexane/EtOAc,
50:1); GC: tR 7.43 min (HP-5, 180 °C, 15 psi).
1H NMR (400 MHz, CDCl3): d = 8.08 (t, J = 1.9, 1 H), 7.93 (dt,
J = 7.8, 1.5, 1 H), 7.58 (dt, J = 7.8, 1.2, 1 H), 7.39 (t, J = 7.8, 1 H),
6.75 (dd, J = 17.6, 11.0, 1 H), 5.83 (dd, J = 17.6, 0.7, 1 H), 5.32 (dd
J = 11.0, 0.5, 1 H), 4.39 (q, J = 7.1, 2 H), 1.40 (t, J = 7.1, 3 H).
13C NMR (125.7 MHz, CDCl3): d = 166.8, 138.0, 136.2, 131.0,
130.6, 129.0, 128.7, 127.5, 115.3, 61.2, 14.5.
IR (film). n = 3010 (w), 2982 (w), 1720 (s), 1602 (w), 1442 (w),
1283 (m), 1265 (m), 1195 (m), 911 (w), 762 (m).
IR (film): n = 3047 (w), 2963 (s), 2934 (m), 1442 (w), 1249 (m),
MS (EI, 70 eV): m/z (%) = 177 (M+ + 1, 6), 176 (M+, 43), 148 (30),
131 (100), 103 (50), 77 (37).
1119 (m), 923 (s), 867 (m), 771 (s).
MS: (EI, 70 eV): m/z (%) = 127 (M+ + 1, 2), 126 (M+, 5), 111 (21),
98 (100), 85 (21), 72 (23), 58 (31).
Anal. calcd for C11H12O2 (176.2): C, 74.98; H, 6.86. Found: C,
74.99; H, 6.91.
Anal. calcd for C7H14Si (126.3): C, 66.58; H, 11.18. Found: C,
66.34; H, 11.11.
3-Ethenylbenzenemethanol (21)
Following the General Procedure, 1 (2.4 mmol, 1.2 equiv), a solu-
tion of TBAF in THF (6 mL, 1 M, 3 equiv), 3-iodobenzyl alcohol
(492.1 mg, 2.0 mmol, 1 equiv), Pd(dba)2 (57.5 mg, 0.05 equiv) and
Ph3As (61.2 mg, 0.10 equiv) were stirred at r.t. for 7.5 h. Et2O (10
mL) was added and the mixture was stirred for another 5 min, then
was filtered through silica gel. Purification by silica gel column
chromatography (pentane/EtOAc, 8:1) and Kugelrohr distillation
afforded 211.4 mg (79%) of 21 as colorless oil; bp 130-135 °C/0.18
Torr; Rf 0.23 (hexane/EtOAc, 8:1); GC: tR 7.55 min (HP-5, 180 °C,
15 psi).
1H NMR (400 MHz, CDCl3): d = 7.32 (m, 4 H), 6.72 (dd, J = 17.6,
10.7, 1 H), 5.77 (dd, J = 17.6, 0.7, 1 H), 5.26 (dd, J = 10.7, 0.7 1 H),
4.67 (d, J = 5.6, 2 H), 1.88 (t, J = 5.9, 1 H).
13C NMR (100.6 MHz, CDCl3): d = 141.3, 138.0, 136.8, 128.9,
126.6, 125.7, 124.9, 114.4, 65.4.
Palladium-Catalyzed Cross Coupling Reaction of 1-Methyl-1-
vinylsilacyclobutane (1) or 1-Methyl-1-(prop-2-enyl)silacyclo-
butane (2) with Aryl or Alkenyl Halides; General Procedure
A solution of TBAF in THF (2.4-9.0 mmol, 1 M) was added to a
solution of 1 or 2 (1.2-3.6 mmol) in THF (1:1 vol%) cooled by ice-
water (the temperature of the reaction mixture should not exceed
10 °C). The ice-bath was removed after completing the addition of
TBAF. The reaction mixture was allowed to warm to r.t. and stirred
for 10 min. Then aryl halide or alkenyl iodides, palladium catalyst
(1-5 mol%) and ligand (0-10%) were sequentially added to the
mixture. The mixture was stirred at r.t. for indicated time, Et2O (10
mL) was added and stirred for another 5 min. The mixture was fil-
tered through a short column of silica gel and washed with Et2O
(60-100 mL). The solvents were removed by rotary evaporator and/
or in vacuo, the crude product was purified by column chromatog-
raphy (silica gel) followed by Kugelrohr distillation to afford the
corresponding product.
IR (NaCl): n = 3350 (m, br), 3168 (m), 2958 (m), 1631 (w), 1456
(w), 990 (m), 906 (m), 886 (w), 796 (m), 713 (s).
MS (EI, 70 eV): m/z (%) = 135 (M+ + 1, 14), 134 (M+, 98), 133
4-Ethenylbenzoic Acid Ethyl Ester (5)
(M+ - 1, 46), 115 (28), 105 (100), 91 (37) 77 (50), 63 (14).
Following the General Procedure, 1 (2.4 mmol, 1.2 equiv), a solu-
tion of TBAF in THF (4 mL, 1 M, 2 equiv), 4-iodobenzoic acid eth-
yl ester (552.1 mg, 2.0 mmol, 1 equiv) and Pd(dba)2 (11.5 mg, 0.01
equiv) were stirred at r.t. for 60 min. Et2O (10 mL) was added and
the mixture was stirred for another 5 min, then filtered through silica
gel. Purification by silica gel column chromatography (hexane/
EtOAc, 50:1) and Kugelrohr distillation afforded 328.4 mg (93%)
of 5 as colorless oil; bp 145-150 °C/0.1 Torr; Rf 0.14 (hexane/
EtOAc, 50:1). GC: tR 7.74 min (HP-5, 180 °C, 15 psi).
1H NMR (400 MHz, CDCl3): d = 8.00 (m, 2 H), 7.45 (m, 2 H), 6.74
(dd, J = 17.6, 10.7, 1 H), 5.86 (dd, J = 17.6, 0.7, 1 H), 5.37 (dd,
J = 10.7, 0.5, 1 H), 4.37 (q, J = 7.1, 2 H), 1.39 (t, J = 7.1, 3 H).
13C NMR (100.6 MHz, CDCl3): d = 166.6, 142.0, 136.2, 129.8,
126.2, 116.6, 61.1, 14.5.
Anal. calcd for C9H10O(134.2): C, 80.56; H, 7.51. Found: C, 80.40;
H, 7.47.
(Z)-5,7-Octadien-1-ol [(Z)-33)]
Following the General Procedure, 1 (1.8 mmol, 1.2 equiv), a solu-
tion of TBAF in THF (4.5 mL, 1 M, 3 equiv), (Z)-6-iodohexen-1-ol
(339.0 mg, 1.5 mmol, 1 equiv) and (allylPdCl)2 (13.7 mg, 0.025
equiv) was stirred at r.t. for 6 h. Et2O (10 mL) was added and the
mixture was stirred for another 5 min, then filtered through silica
gel. Purification by silica gel column chromatography (pentane/
Et2O, 4:1) and Kugelrohr distillation afforded 91.1 mg (48%) of (Z)-
33 as colorless oil; bp 90-95 °C/5 Torr; Rf 0.22 (pentane/Et2O, 4:1);
GC (Z)-33, tR 26.76 min (98%); (E)-33, 26.14 min (2%) (HP-225,
70 °C 15 psi).
1H NMR (400 MHz, CDCl3): d = 6.62 (ddt, J = 16.8, 10.3, 1.0, 1 H),
6.00 (t, J = 11.0, 1 H), 5.44 (m, 1 H), 5.18 (dd, J = 16.8, 2.0, 1 H),
5.08 (d, J = 10.3, 1 H), 3.64 (t, J = 5.9, 2 H), 2.22 (m, 2 H), 1.55 (m,
2 H), 1.45 (m, 3 H).
13C NMR (100.6 MHz, CDCl3): d = 132.6, 132.4, 129.7, 117.2,
62.9, 32.4, 27.6, 25.9.
IR (CHCl3): n = 3092 (w), 2984 (s), 2940 (m), 2258 (m), 1709 (s),
1608 (s), 1368 (s), 1279 (s), 1179 (s), 1108 (s), 860 (s).
MS (EI, 70 eV): m/z (%) = 177 (M+ + 1, 5), 176 (M+, 35), 148 (31),
131 (100), 103 (37), 77 (35).
Anal. calcd for C11H12O2 (176.2): C, 74.98; H, 6.86%. Found: C,
74.97; H, 6.91%.
Synthesis 2000, No. 7, 999–1003 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
1-Methyl-1-vinyl- and 1-Methyl-1-(prop-2-enyl)silacyclobutane
1003
IR (film): n = 3343 (m, br), 3085 (m), 3025 (m), 3009 (m), 2935
Acknowledgement
(m), 1643 (w), 1063 (m), 997 (m), 902 cm-1 (m).
We thank the National Science Foundation for generous financial
support (CHE 9803124).
MS (EI, 70 eV): m/z (%) = 127 (M+ + 1, 0.8), 126 (M+, 4.9), 108
(23), 98 (22), 79 (100), 67 (80).
Anal. calcd for C8H14O (126.2): C, 76.14; H, 11.18. Found: C,
76.19; H, 11.14.
References
3-(1-Methylethenyl)benzenemethanol (37)
(1) (a) Denmark, S. E.; Choi, J. Y. J. Am. Chem. Soc. 1999, 121,
5821.
(b) Denmark, S. E.; Wu. Z. Org. Lett. 1999, 1, 1495.
(2) (a) Bertrand, G.; Manuel, G.; Mazerolles, P.; Trinquier, G.
Tetrahedron 1981, 37, 2875.
Following the General Procedure, 2 (2.4 mmol, 1.2 equiv), a solu-
tion of TBAF in THF (6.0 mL, 1 M, 3 equiv), 3-iodobenzyl alcohol
(468.0 mg, 2.0 mmol, 1 equiv) and Pd(dba)2 (57.5 mg, 0.05 equiv)
were stirred at r.t. for 10 min. Et2O (10 mL) was added and the mix-
ture was stirred for another 5 min, then was filtered through silica
gel. Purification by silica gel column chromatography (pentane/
Et2O, 4:1) and Kugelrohr distillation afforded 258.6 mg (87%) of 37
as a colorless oil; bp 135-140 °C/0.5 Torr; Rf 0.11 (pentane/Et2O,
5:1); GC: tR 6.77 min (HP-5, 180 °C, 15 psi).
1H NMR (400 MHz, CDCl3): d = 7.46 (s, 1 H), 7.39 (m, 1 H), 7.32
(t, J = 7.6, 1 H), 7.26 (d, J = 7.8, 1 H), 5.38 (s, 1 H), 5.09 (qn,
J = 1.5, 1 H), 4.68 (s, 2 H), 2.16 (s, 3 H), 1.83 (br s, 1 H).
13C NMR (100.6 MHz, CDCl3): d = 143.1, 141.6, 140.8, 128.5,
126.0, 124.9, 124.2, 112.7, 65.4, 21.8.
(b) Grobe, J.; Ziemer, H. Z. Naturforsch. 1993, 48B, 1193.
(c) Jouikov, V.; Krasnov, V. J. Organomet. Chem. 1995, 498,
213.
(3) Matsumoto, K.; Takeyama, Y.; Miura, K.; Oshima, K.;
Utimoto, K. Bull. Chem. Soc. Jpn. 1995, 68, 250.
(4) Commerically available from Gelest or Aldrich.
(a) Laane, J. J. Am. Chem. Soc. 1967, 89, 1144.
(b) Denmark, S. E.; Griedel, B. D.; Coe, D. M.; Schnute, M.
E. J. Am. Chem. Soc. 1994, 116, 7026.
(5) The salutary effect of Ph3As in Stille-type cross-coupling
reactions has been well-documented by Farina. Farina, V.;
Krishinan, B. J. Am. Chem. Soc. 1991, 113, 9585.
IR (film): n = 3334 (m, br), 2972 (w), 2875 (w), 1629 (w), 1451 (m),
1019 (m), 891 (m), 796 (m), 718 cm-1 (m).
MS (EI, 70 eV): m/z (%) = 149 (M+ + 1, 14), 148 (M+, 100), 133
(33), 119 (30), 107 (44), 91 (59), 77 (33), 65 (13).
Article Identifier:
1437-210X,E;2000,0,07,0999,1003,ftx,en;C00600SS.pdf
Anal. calcd for C10H12O(148.2): C, 81.04; H, 8.16. Found: C, 80.92;
H, 8.31.
Synthesis 2000, No. 7, 999–1003 ISSN 0039-7881 © Thieme Stuttgart · New York