THE VINYLATION OF ARENES WITH 1-(PHENYLTHIO)VINYLSTANNANES

Article abstract of DOI:10.1016/0040-4039(91)80085-K

The vinylation of arenes using 1-(phenylthio)vinylstannanes proceeded in the presence of tin(IV) chloride and molecular sieves 4A to afford 1-arylalkenyl sulfides in good yields.The stereochemistry of the olefinic moiety was determined after oxidation to the corresponding sulfones and it was found that the present reaction gave the thermodynamically stable stereoisomers.

Full text of DOI:10.1016/0040-4039(91)80085-K

Tetlahedron Letters. VoL32, No 40, pp 5567-5570, 1991
Printed m GreatBritain
0040-4039/91 $3.00
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THE VINYLATION OF ARENES WITH 1-(PHENYLTHIO)VINYLSTANNANES
Takeshi TAKEDA,* Fumio KANAMORI, Mitsutoshi MASUDA, and Tooru FUJIWARA
Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan
Abstract: The vinylation ofarenes using l-(phenyhhio)vinylstaananes proceeded in the presence of tin(IV)
chloride and molecular sieves 4A to afford l-arylalkenyl sulfides in good yields. The stereochemistry of the
olef'mie moiety was determined after oxidation to the the corresponding sulfones and it was found that the present
reaction gave the thermodynamically stable stereoisomers.
Although much efforts have been directed towards the development of the synthetic reactions which proceed
via vinylic cations or their equivalents, the vinylation using such species is still difficult and only a few examples
using vinylic halides or triflates are reported.1) Recently, we found that the various nucleophiles reacted with
allyl and allenylstannanes in the presence of tin(IV) or copper(II) salts.2) It is of interest whether these "oxidative
coupling reactions" proceed using the vinylic organotin compounds. Then we investigated the coupling reactions
of 1-(phenylthio)vinylstannanes (1) with nucleophilic reagents and found that l-arylalkenyl sulfides (2) were
produced when I were treated with tin(IV) chloride in aromatic solvents (Eq. 1).
~
~
11)
SnBu3
SnCla
molecular sieves 4A ~ [ ~ - - X 2
1
6
The Z-isomers of l -(phenylthio)vinylstannanes (1) were stereoselectively synthesized by the treatment of (E)-
1-(phenylthio)vinyllithiurn reagents3) with tributyitin chloride (1a, 89%; I b, 73%; 1e, 86%; I d, 85%). The
corresponding E-isomer of la was prepared by the photoisomerization of the Z-isomer.4) The aryl group
substituted compounds (le, 73%) were prepared as a mixture of stereoisomers by the Peterson olefination using
(phenylthio)(tributylstannyi)(trimethylsilyi)methyllithium.5)
When (Z)-1-(phenylthio)- l-(tributylstannyl)- l-pentene (Z- la) was treated with tin(IV) chloride in anisole at
r.t., the disappearence of Z- la was immediately observed on TLC. Then the reaction mixture was refluxed for 4
h to give the corresponding alkenyl sulfide (2a) in 43% yield along with a small amount of anisyl butyl ketone (3)
(run 1). However, no product was obtained by the reaction with rather unreactive aromatic compounds such as
xylene (run 6), toluene, or benzene. Since the formation of 3 was due to the resulting hydrogen chloride, we
examined the use of molecular sieves 4A to capture hydrogen chloride. It was found that molecular sieves not
only prevent the hydrolysis of alkenyl sulfide but also accelerated the reaction remarkably. Using molecular
sieves, 2 were obtained in good yields even when the unreactive arenes were employed. In the case of the
reaction of ld bearing a phenyl group at~5 to tributylstannyl group, the intramolecular reaction preferentially
proceeded (run 17). These results were summarized in Table 1.
The typical experimental procedure is as follows: To a flask charged with £mely ground molecular sieves 4A
(1.1 g) were added an anisole (3 ml) solution of(Z)- l-(phenylthio)- l-(tributylstannyl)- 1-pentene ( Z- I a ) (234
mg, 0.5 mmol) and a CH2CI2 solution ofSnCi4 (0.55 mmol) successively. After being stirred for 30 min, the
reaction mixture was refluxed for 4 h. The reaction was quenched by addition of water and molecular sieves were
5567

5568
Table 1. The reaction of 1-(phenylthio)vinylstannanes with arenesa)
Run
!
Solvent
Time
h
Product
Yieldb,c)
%
E
Z d)
1
2
anisole
anisole
4
4
2a
2a
43 (5)e)
80
3
4
5
6
1,2,3-trimethylbenzene
1,2,3-trimethylbenzene
mesitylene
4
4
5
4
2b
2b
2c
2d
35e)
" f v ~ Sph
84
SnBu 3 Z- I a
82
0e)
70
30
m-xylene
7
8
9
10
11
m-xylene
m-xylene
toluene
benzene
benzene
4
4
2d
2d
2e
2f
2 f
700
77
55
26
:
:
45
74
17
68
11
16
9f, g)
74g)
17
83
mesitylene
benzene
5
16
2c
2f
95
66g)
76
20
:
:
24
80
12
13
"
E - l a
"Sl SPhn B u a
14
15
~
I
S
P
h
mesitylene
benzene
5
16
2g
2h
59
50g)
10
22
:
:
90
78
-SnBuz Z - i b
16
L / ~ , / S Ph
,- -I
anisole
4
2i
53 (22)e,h)
v
Z-lc
...................... .s.n. ~ .u_a. .......................................................................................................
17
~
SPh
anisole
4
ct-tetralone
62i)
~ . ~
Sn~u3 Z- I d
.
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18 . , ~ x . . . / ~ . . ~ S P h
19 ~
anisole
m-xylene
5.5
4
2k
21
92
87
s
n
B
u
3
I e
a) All the reactions were performed with a similar procedure as described in the text, unless otherwise noted, b)
The structures of these compounds were supported by IR and NMR spectra, c) The yields in parentheses are
those of the ketones (3). d) Based on the isolated yields of the stereoisomers of corresponding alkenyl sulfones
(4). e) In the absence of molecular sieves, f') The reaction was carried out at 120 °C. g) The reaction was carried
out in a sealed tube at 170 °C. h) 2.2 equiv, ofSnCl4 were used. i) Since the alkenyl sulfide (2) was unstable,
the product was isolated after hydrolysis with HCI (1 ml/1 mmol of 2) in AcOH (6 ml/1 mmol of 2) at r.t.
overnight.
filtered off. The organic material was extracted with CH2CI2. The extract was washed with 10% KF aqueous
solution, dried (Na2SO4), and condensed under reduced pressure. The residue was chromatographed on silica
gel (Hexane : AcOEt = 95 : 5) and then 1-anisyl- 1-(phenylthio)- 1-pentene (2a) (113 rag, 80%) was obtained
On the basis of the NMR analysis, it was assumed that all the alkenyl sulfides thus obtained were mixtures of
stereoisomers and positional isomers which resulted from the difference of relative positions of the substituents
on an aromatic ring. Since it was difficult to determine the ratio ofstereoisomers ofalkenyl sulfides (2), 2 were
transformed to the corresponding sulfones (4) by the treatment with MCPBA (3 equiv ) in CH2CI2 (0 °C,
overnight). The two isomers of 4 were separated each other by TLC and they were found to correspond to the E
and Z-isomers by comparison with authentic alkenyl sulfides prepared from aromatic ketones.6) The vinyl
proton of one isomer resonates at 0.5 - 1.7 ppm downfield from the vinyl proton of the corresponding sulfide
(2). On the other hand, the chemical shift of vinyl proton of the another isomer varies to a smaller extent after

5569
Table 2. The oxidation ofalkenyl sulfides (2) and the chemical shifts of vinyl protons
Run
2
4
Yield
%
(Chemical shift of vinyl proton (8))a)
(Chemical shift of vinyl proton (15))a)
2c
2d
( E;
5.33 Z; 5.36 )
4c
4d
( E; 7.00, Z; 5.83 )
95
90
Z; 5.60 )b,c)
Z; 5.35 )b,d)
Z, 5.94 )b,e)
Z; 5.77 )b,f)
Z; 6.23 )
( E; 5.60
( E; 5.35
( E; 6.00
( E; 5.77
( E; 5.93
(E; 5.13
( E, > 6.3, Z, 5.90 )b,c)
( E; > 6.3, Z; 5.83 )b,d)
( E, > 6.6, Z; 5.94 )b,e)
( E; > 6.3, Z; 5.90 )b,f)
( E; > 6.7, Z; 5.98 )
( E; 6.80, Z; 5.54 )
2e
4e
75
2f
2g
2h
4f
4g
4h
93
87
91
Z; 5.13 )
(E; 5.71,Z; 6.01 )
( E; > 6.5, Z; 5.74 )
a) Measured in CC14. b) The signals were assigned by the comparison with the NMR spectrum of the authentic
compound prepared from the corresponding aromatic ketone.6) c) 2,4-Xylyl. d) 2,6-Xylyl. e) p-Tolyi, f) o-
Tolyl.
oxidation (Table 2). It is rational to assume that the former is the E-isomer and the latter is Z-isomer. This
assumption is also supported by the prediction of the chemical shifts using Z-factors.7)
The stereocbemical results listed in Table I indicate that the number of substituents on benzene ring is a
dominant factor to determine the main stereoisomer. Furthermore, the mixtures with the same proportions of
stereoisomers were formed from both Z and E- 1a. This fact suggests that the initial products of the present
reaction were isomerized to the more thermally stable ones under the reaction conditions. In fact, it was
confirmed that the alkenyl sulfide (2f (E : Z ffi 60 : 40 )) was thermally isomerized to its equilibrium composition
(22 : 78) by heating in benzene for 16 h. Furthermore, the distributionofstereoisomers of authentic alkenyl
sulfides (2) prepared by the reaction of aromatic ketones with thiopbenol in the presence of phosphorus
pentoxide, which was expected to be a thermodynamically controlled process, was found to be similar to that
observed in the reaction of 1 with arenes ( 2d (2,4-xylyl), E : Z ffi 66 : 34; 2d (2,6-xylyl), E : Z ffi 79 : 21; 2e
(o-tolyl), E : Z ffi 59 : 41; 2e (p-tolyl), E : Z = 20 : 80; 2t", E : Z = 19 : 81 ).
As noted above, 1-(phenylthio)vinylstannane (Z-la) react with SnCI4 to form some intermediate. In order to
determine the structure of intermediate, Z-I a was treated with SnCI4 in anisole at r.t. After evaporation of the
volatile materials under reduced pressure, the NMR spectrum of the residue was measured in CDCI3 and the sole
triplet of vinyl proton was observed at ~ = 7.03 which corresponded to neither the starting material (Z- I a) (15 =
6.43) nor (Z)- 1-chloro-1-(phenylthio)-l-pentene (5) (5 = 6.27). Further, (Z)- 1-(phenylthio)- l-(triphenyl-
stannyl)-1-pentene was isolated in 82% yield by the treatment of the intermediate with excess phenylmagnesium
bromide in anisole. These results suggest that the intermediate of the present reaction is the trichlorovinyl-
stannane (6). It was confirmed that 6 was thermally stable and only a trace amount of the vinyl chloride (5) was
detected when it was heated in refluxing m-xylene (see Table 1, run 6).
Some of the alkenyl sulfides were hydrolyzed to the corresponding aromatic ketones to determine the ratio of
position isomers. Since the distribution of position isomers was similar to that of common Friedel-Crafis type
reactions (Table 3), it is reasonable to assume that the present reaction proceeds through the initial formation of
the arenium ion (7) by the attack of arene on the trichlomvinylstannane (6) or the vinyl cation species (8) formed
from 6 as illustrated in Eq. 2.

5570
Table 3. The hydrolysis ofalkenyl sulfides (2)a)
Aromatic ketone (3)
Run Alkenyl sulfide (2)
Yield
%
~ . . ~ OMe
1
2a
90
:
39b,c)
23b, c)
0 0 M e
O
61
2
2b
65
Me
Me
. ~ , ~ Me 77
:
Me
o
o
3
4
2d
2e
74
65
~ . ~ l u l e
> 95e)
O
~
,
,
~
I~e >95c)
O
a) The hydrolysis was carried out by the treatment of 2 with hydrochloric acid in acetic acid at
r.t. overnight, b) Determined by NMR analysis, c) Determined by GLC analysis.
-
CI3Sn"
_
~
.SPh
(2)
7
~
X
"~
R8- ~.,.-,,.r-.+.~,.._._~q~jii--X
-H+
t .CI3S n-
6
2
It should be noted that the present reaction is the first example of coupling reaction of vinylic organotin
compound with nucleophilic reagent and provides a convenient method for the preparation of aryl substituted
alkenyl sulfides.
References
1) Z. Rappoport, Acc. Chem. Res., 14, 7 (1981). For the examples of Friedel-Cmfts type reactions, see; P. J.
Stung and A. G.Anderson, J. Am. Chem. Soc., 100, 1520 (1978); T. Kitamura, S. Kobayashi, and H
Taniguchi, ibid., 108, 2641 (1986); M. Ochiai, Y. Takaoka, K. Sumi, and Y Nagao, J. Chem. So¢., Chem.
Commun., 1986, 1383.
2) J. Yamaguchi, Y. Takagi, A. Nakayama, T. Fujiwara, and T. Takeda, Chem. Lett., 199 l, 133, T. Takeda,
A. Nakayama, T. Furukawa, and T. Fujiwara, Tetrahedron Lett., 31,6685 (1990)
3) T. Takeda, H. Furukawa, M. Fujimori, K. Suzuki, and T. Fujiwam, Bull. Chem. Soc. Jpn., 57, 1863
(1984).
4) The experimental procedure is as follows: A hexane (6 ml) solution of Z-I a (234 mg, 0.5 retool) and
benzophenone (5 mg, 0.03mmol) in a pyrex test tube was irradiated with high pressure mercury lamp (400 W)
under argon for 1 h. After usual work-up, the products were separated by TLC (hexane) to give E-1a ( 117 rag,
50%) and Z-la (75 rag, 32%).
5) B. T. Gr6bel and D. Seebach, Chem, Bet., 110,852 (1977).
6) B. M. Trost and A. C. Lavoie, J Am. Chem Soc., 105, 5075 (1983).
7) L M. Jackman and S. Stemhell, "Application of Nuclear Magnetic Resonance Spectroscopy m Organic
Synthesis," 2nd ed, Pergamon Press, Oxford (1969), p. 184.
(Recewed m Japan 18 June 1991)