Nucleophilic Vinylic Substitutions of (Z)-(β-Haloalkenyl)phenyliodonium Salts with Sodium Benzenesulfinate: First Evidence of a Michael Addition of Nucleophiles to Alkenyliodonium Salts at the Cβ Atom

Article abstract of DOI:10.1021/jo970735v

Evidence for a Michael addition of a nucleophile to alkenyl(phenyl)iodonium salts at the Cβ atom is reported here for the first time. Nucleophilic vinylic substitutions of (Z)-(β-chloroalkenyl)- 2b and (Z)-(β-bromoalkenyl)iodonium tetrafluoroborates 3b with sodium benzenesulfinate in THF afforded stereoselectively (Z)-1,2-bis(benzenesulfonyl)alkene 5b with retention of configuration. Intermediate formation of (Z)-(β-(benzenesulfonyl)alkenyl)iodonium salt 9b in these reactions was established by ¹H NMR experiments in CDCl₃. The formation of (Z)-9b involves a hitherto unobserved Michael addition of benzenesulfinate anion to the alkenyliodonium salts at the C_β atom, followed by halogen extrusion. The formation of a stereoisomeric mixture of (Z)- and (E)-bis-sulfones 5b, and 1-(benzenesulfonyl)cyclopentene 11 that was observed in the reaction of (Z)-(β-fluoroalkenyl)-iodonium salt 4b in CDCl₃, strongly suggests the intermediacy of 9b in this nucleophilic vinylic substitution.

Full text of DOI:10.1021/jo970735v

J . Org. Chem. 1997, 62, 8001-8008
8001
Nu cleop h ilic Vin ylic Su bstitu tion s of
(Z)-(â-Ha loa lk en yl)p h en yliod on iu m Sa lts w ith Sod iu m
Ben zen esu lfin a te: F ir st Evid en ce of a Mich a el Ad d ition of
Nu cleop h iles to Alk en yliod on iu m Sa lts a t th e Câ Atom
Masahito Ochiai,*,1a Yutaka Kitagawa,1a Mika Toyonari,1a Koji Uemura,1b
Kunio Oshima,1b and Motoo Shiro1c
Faculty of Pharmaceutical Sciences, University of Tokushima, 1-78 Shomachi, Tokushima 770,
Gifu Pharmaceutical University, 5-6-1 Mitahora Higashi, Gifu 502, and Rigaku Corporation,
3-9-12 Matsubara, Akishima, Tokyo 196, J apan
Received April 24, 1997X
Evidence for a Michael addition of a nucleophile to alkenyl(phenyl)iodonium salts at the Câ atom
is reported here for the first time. Nucleophilic vinylic substitutions of (Z)-(â-chloroalkenyl)- 2b
and (Z)-(â-bromoalkenyl)iodonium tetrafluoroborates 3b with sodium benzenesulfinate in THF
afforded stereoselectively (Z)-1,2-bis(benzenesulfonyl)alkene 5b with retention of configuration.
Intermediate formation of (Z)-(â-(benzenesulfonyl)alkenyl)iodonium salt 9b in these reactions was
established by 1H NMR experiments in CDCl3. The formation of (Z)-9b involves a hitherto
unobserved Michael addition of benzenesulfinate anion to the alkenyliodonium salts at the Câ atom,
followed by halogen extrusion. The formation of a stereoisomeric mixture of (Z)- and (E)-bis-sulfones
5b, and 1-(benzenesulfonyl)cyclopentene 11 that was observed in the reaction of (Z)-(â-fluoroalkenyl)-
iodonium salt 4b in CDCl3, strongly suggests the intermediacy of 9b in this nucleophilic vinylic
substitution.
Alkynyl(phenyl)iodonium salts are highly electron-
deficient species2 and act as good Michael acceptors for
a variety of soft nucleophiles, including stable enolates
of 1,3-dicarbonyl compounds, and oxygen (carboxylates
and phenoxides), nitrogen (azide and amide), and sulfur
nucleophiles (sulfinates and thiocyanates).3 Michael
addition of nucleophiles to the â-carbon of alkynyliodo-
nium salts constitutes a key step for efficient cyclopen-
tene annulation of alkynyliodonium salts via the tandem
Michael-carbene insertion (MCI) reaction.3 In contrast,
Michael addition to alkenyl(phenyl)iodonium salts at the
Câ atom has never been reported.2
whereas formation of a stereoisomeric mixture of (Z)- and
(E)-bis-sulfones 5 was observed in the reaction of (Z)-(â-
fluoroalkenyl)iodonium salt 4.
Resu lts a n d Discu ssion
Syn th esis of (Z)-(â-Ha loa lk en yl)p h en yliod on iu m
Tetr a flu or obor a tes. Conjugate addition of halide ions
(3) (a) Enolate anions: Ochiai, M.; Kunishima, M.; Nagao, Y.; Fuji,
K.; Shiro, M.; Fujita, E. J . Am. Chem. Soc. 1986, 108, 8281. Ochiai,
M.; Ito, T.; Takaoka, Y.; Masaki, Y.; Kunishima, M.; Tani, S.; Nagao,
Y. J . Chem. Soc., Chem. Commun. 1990, 118. Suzuki, T.; Uozumi, Y.;
Shibasaki, M. J . Chem. Soc., Chem. Commun. 1991, 1593. Tykwinski,
R. R.; Stang, P. J .; Persky, N. E. Tetrahedron Lett. 1994, 35, 23.
Kitamura, T.; Nagata, K.; Taniguchi, H. Tetrahedron Lett. 1995, 36,
1081. (b) Oxygen nucleophiles: Stang, P. J .; Surber, B. W. J . Am.
Chem. Soc. 1985, 107, 1452. Stang, P. J .; Boehshar, M.; Lin, J . J . Am.
Chem. Soc. 1986, 108, 7832. Stang, P. J .; Boehshar, M.; Wingert, H.;
Kitamura, T. J . Am. Chem. Soc. 1988, 110, 3272. Stang, P. J .;
Kitamura, T.; Boehshar, M.; Wingert, H. J . Am. Chem. Soc. 1989, 111,
2225. Ochiai, M.; Kunishima, M.; Fuji, K.; Nagao, Y. J . Org. Chem.
1989, 54, 4038. Kitamura, T.; Zheng, L.; Taniguchi, H.; Sakurai, M.;
Tanaka, R. Tetrahedron Lett. 1993, 34, 4055. Shu, T.; Chen, D.-W.;
Ochiai, M. Tetrahedron Lett. 1996, 37, 5539. (c) Nitrogen nucleo-
philes: Kitamura, T.; Stang, P. J . Tetrahedron Lett. 1988, 29, 1887.
Ochiai, M.; Kunishima, M.; Fuji, K.; Nagao, Y. J . Org. Chem. 1988,
53, 6144. Murch, P.; Williamson, B. L.; Stang, P. J . Synthesis 1994,
1255. 50. Kunz, R.; Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl.
1994, 33, 330. Feldman, K. S.; Bruendl, M. M.; Schildknegt, K. J . Org.
Chem. 1995, 60, 7722. Schildknegt, K.; Bohnstedt, A. C.; Feldman, K.
S.; Sambandam, A. J . Am. Chem. Soc. 1995, 117, 7544. (d) Sulfur
nucleophiles: Ochiai, M.; Kunishima, M.; Tani, S.; Nagao, Y. J . Am.
Chem. Soc. 1991, 113, 3135. Stang, P. J .; Zhdankin, V. V. J . Am. Chem.
Soc. 1990, 112, 6437. Stang, P. J .; Zhdankin, V. V. J . Am. Chem. Soc.
1991, 113, 4571. Kitamura, T.; Furuki, R.; Zheng, L.; Fujimoto, T.;
Taniguchi, H. Chem. Lett. 1992, 2241. Kitamura, T.; Furuki, R.; Zheng,
L.; Nagata, K.; Fukuoka, T.; Fujiwara, Y.; Taniguchi, H. Bull. Chem.
Soc. J pn. 1995, 68, 3637. Fischer, D. R.; Williamson, B. L.; Stang, P.
J . Synlett 1992, 535. Williamson, B. L.; Murch, P.; Fischer, D. R.; Stang,
P. J . Synlett 1993, 858. Tykwinski, R. R.; Williamson, B. L.; Fischer,
D. R.; Stang, P. J .; Arif, A. M. J . Org. Chem. 1993, 58, 5235.
Williamson, B. L.; Tykwinski, R. R.; Stang, P. J . J . Am. Chem. Soc.
1994, 116, 93. Liu, Z.-D.; Chen, Z.-C. Synth. Commun. 1992, 22, 1997.
Liu, Z.-D.; Chen, Z.-C. J . Org. Chem. 1993, 58, 1924. (e) Phosphites:
Lodaya, J . S.; Koser, G. F. J . Org. Chem. 1990, 55, 1513.
Because of the excellent nucleofugality of the phenyli-
odonio group, which shows a leaving group ability about
106 times greater than triflate,4 alkenyl(phenyl)iodonium
salts serve as the highly activated species of alkenyl
halides in nucleophilic vinylic substitution reactions with
a number of nucleophiles, such as organocuprates, sul-
finates, thiolates, nitrites, halides, cyanides, azides, and
phosphines.5-7 These nucleophilic vinylic substitutions
of alkenyliodonium salts occur regioselectively at the ipso
positions under mild conditions.
Here, for the first time, we report evidence of a
nucleophilic vinylic substitution of (Z)-(â-haloalkenyl)-
iodonium tetrafluoroborates 2-4 with sodium benzene-
sulfinate that involves a Michael addition to the â-carbon
atom as the first step of the reaction.8 Nucleophilic
vinylic substitutions of â-chloro- 2 and â-bromoiodonium
tetrafluoroborates 3 with sodium benzenesulfinate af-
forded (Z)-1,2-bis(benzenesulfonyl)alkene 5 stereoselec-
tively in high yields with retention of configuration,
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) (a) The University of Tokushima. (b) Gifu Pharmaceutical
University. (c) Rigaku Corporation.
(2) For reviews, see: (a) Koser, G. F. The Chemistry of Functional
Groups, Supplement D; Wiley: New York, 1983; Chapter 25. (b) Ochiai,
M. Rev. Heteroatom Chem. 1989, 2, 92. (c) Stang, P. J . Angew. Chem.,
Int. Ed. Engl. 1992, 31, 274. (d) Varvoglis, A. The Organic Chemistry
of Polycoordinated Iodine; VCH Publishers: New York, 1992. (e) Koser,
G. F. The Chemistry of Functional Groups, Supplement D2; Wiley: New
York, 1995; Chapter 21. (f) Stang, P. J .; Zhdankin, V. V. Chem. Rev.
1996, 96, 1123.
(4) Okuyama, T.; Takino, T.; Sueda, T.; Ochiai, M. J . Am. Chem.
Soc. 1995, 117, 3360.
(5) (a) Ochiai, M.; Sumi, K.; Takaoka, Y.; Kunishima, M.; Nagao,
Y.; Shiro, M.; Fujita, E. Tetrahedron 1988, 44, 4095. (b) Ochiai, M.;
Sumi, K.; Nagao, Y.; Shiro, M.; Fujita, E. Tetrahedron Lett. 1985, 26,
2351. (c) Beringer, F. M.; Galton, S. A. J . Org. Chem. 1965, 30, 1930.
S0022-3263(97)00735-4 CCC: $14.00 © 1997 American Chemical Society

8002 J . Org. Chem., Vol. 62, No. 23, 1997
Shiro and Ochiai
Sch em e 1
Sch em e 2
Ta ble 2. Rea ction of (Z)-(â-Ha loa lk en yl)iod on iu m Sa lts
w ith Sod iu m Ben zen esu lfin a tea
product (yield,b
iodonium
entry
salt
time, h
(Z)-5
(E)-5
7
Ta ble 1. Syn th esis of (Z)-(â-Ha loa lk en yl)iod on iu m
Sa lts 2 a n d 3a
1
2
2a
2b
2c
2d
2e
2f
2g
2h
3b
3c
4b
4c
8
2
3.5
4
8
2
2.5
70
64
82
49
65
(Z)-5a (95)
(Z)-5b (92)c
(Z)-5c (89)
(Z)-5d (93)
(Z)-5e (86)
(Z)-5f (83)
(Z)-5g (87)
(Z)-5h (6)d
(Z)-5b (52)
(Z)-5c (53)
iodonium
salt 1
product
3
entry
LiXb
time, h
(yield,c %)
4
5
1
2
1a
1b
1c
1d
1e
1f
1g
1h
1b
1c
LiCl
LiCl
LiCl
LiCl
LiCl
LiCl
LiCl
LiCl
LiBr
LiBr
12
9
2a (81)
2b (91)
2c (85)
2d (70)
2e (88)
2f (80)
2g (84)
2h (84)
3b (71)
3c (81)
6
7
3
12
11
10
12
20
4.5
12
11
8
4
9
7b (30)
7c (35)
5
10
11
12
6
(Z)-5b (25) (E)-5b (75)
(Z)-5c (12) (E)-5c (68)
7
8
9
a
Reactions were carried out using 2.5 equiv of sodium benze-
10
nesulfinate in THF at 0 °C. Isolated yields. c A trace amount of
b
a
b
d
Reactions were carried out at room temperature. 10 equiv
of LiX were used. c Isolated yields.
6b was detected. (Z)-2-Chloro-3,3-dimethyl-1-butenyl phenyl sul-
fone (8) was obtained in 78% yield.
(Cl- or Br-) to alkynyl(phenyl)iodonium salts 19 using
LiCl or LiBr (10 equiv) in acetic acid at room tempera-
ture, followed by ligand exchange with NaBF4, gave (Z)-
(â-haloalkenyl)phenyliodonium tetrafluoroborates 2 or 3
in high yields (Scheme 1).10 The results of synthesizing
2 and 3 are summarized in Table 1. The addition
reactions were stereoselective, and no formation of the
corresponding (E)-isomers was detected. The (Z)-stere-
ochemistry of these iodonium salts was established by
observation of an NOE enhancement between the vinylic
and allylic protons.
chloro-1-decenyl)iodonium tetrafluoroborate (2b) to so-
dium benzenesulfinate (2.5 equiv) in THF at 0 °C for 2 h
resulted in double nucleophilic vinylic substitutions of a
phenyliodonio group and a â-chlorine atom, giving (Z)-
1,2-bis(benzenesulfonyl)alkene 5b7b in 92% yield, along
with (Z)-chlorosulfone 6b in trace amounts (Scheme 2).7a
Similarly, the reaction with (â-chlorovinyl)iodonium salts
2a and 2c-g afforded the corresponding (Z)-bis(benze-
nesulfonyl)alkenes 5 in high yields (Table 2). All of these
1
reactions were exclusively stereoselective (by H NMR)
with retention of configuration. The alkenyliodonium
salt 2h with a sterically demanding tert-butyl group at
the â-position took a different reaction course, i.e.,
monosubstitution at the R-position (Table 2, entry 8). The
reaction was very slow and, after 70 h at room temper-
ature, gave (Z)-2-chloro-3,3-dimethyl-1-butenyl phenyl
sulfone (8) in 78% yield. Yield of the normal product,
(Z)-1,2-bis(benzenesulfonyl)alkene 5h is low (6%).
In marked contrast to the reaction of (Z)-(â-chloroalk-
enyl)iodonium salts 2, the rate of substitutions of (Z)-
(â-bromoalkenyl)iodonium tetrafluoroborates 3 with so-
dium benzenesulfinate was slow, and the reaction resulted
in formation of a large amount of the (Z)-bromovinyl
sulfone 7: thus, â-bromoiodonium salt 3b afforded a
mixture of the (Z)-1,2-bis(benzenesulfonyl)alkene 5b and
the (Z)-bromovinyl sulfone 7b7a in 52 and 30% yields,
respectively (Table 2, entry 9). Similarly, 3c gave a
mixture of (Z)-5c (53%) and 7c (35%). Interestingly, with
(Z)-(2-fluoro-1-decenyl)phenyliodonium tetrafluoroborate
(4b), we observed exclusive substitution with sodium
benzenesulfinate yielding 1,2-bis(benzenesulfonyl)alkene
5, but we obtained a mixture of stereoisomers with (E)-
isomer as a major product. This reaction afforded a 25:
75 mixture of (Z)- and (E)-5b in a quantitative yield
(Table 2, entry 11). The reaction with 4c also afforded a
mixture of (Z)- (12%) and (E)-5c (68%).
Our attempt at conjugate addition of fluoride ion under
similar conditions (LiF in acetic acid at room tempera-
ture) resulted in the recovery of the alkynyliodonium salt
1. Use of CsF instead of LiF, and of water as an additive,
however, led to the formation of (Z)-(â-fluoroalkenyl)-
iodonium tetrafluoroborates 4, albeit in a low yield: thus,
treatment of 1b with CsF (2 equiv) in acetone-dichlo-
romethane (1:1) in the presence of water (20 equiv) at
room temperature, followed by ligand exchange with
NaBF4, afforded (Z)-(â-fluoro-1-decenyl)phenyliodonium
tetrafluoroborate (4b) in 20% yield.11 Similarly, 4c was
prepared from 1c in 15% yield by reaction with CsF.
Rea ction of (Z)-(â-Ha loa lk en yl)iod on iu m Sa lts
w ith Sod iu m Ben zen esu lfin a te. Exposure of (Z)-(2-
(6) Ochiai, M.; Oshima, K.; Masaki, Y. J . Am. Chem. Soc. 1991, 113,
7059.
(7) (a) Ochiai, M.; Oshima, K.; Masaki, Y. Tetrahedron Lett. 1991,
32, 7711. (b) Ochiai, M.; Oshima, K.; Masaki, Y.; Kunishima, M.; Tani,
S. Tetrahedron Lett. 1993, 34, 4829. (c) Ochiai, M.; Oshima, K.; Masaki,
Y. Chem. Lett. 1994, 871. (d) Zefirov, N. S.; Kozmin, A. S.; Kasumov,
T.; Potekhin, K. A.; Sorokin, V. D.; Brel, V. K.; Abramkin, E. V.;
Struchkov, Y. T.; Zhdankin, V. V.; Stang, P. J . J . Org. Chem. 1992,
57, 2433.
(8) A part of this work has been reported in a preliminary form:
Ochiai, M.; Kitagawa, K.; Toyonari, M.; Uemura, K. Tetrahedron Lett.
1994, 35, 9407.
(9) For synthesis of alkynyl(phenyl)iodonium tetrafluoroborates 1,
see: (a) Ochiai, M.; Kunishima, M.; Sumi, K.; Nagao, Y.; Fujita, E.
Tetrahedron Lett. 1985, 26, 4501. (b) Ochiai, M.; Kunishima, M.; Nagao,
Y.; Fuji, K.; Fujita, E. J . Chem. Soc., Chem. Commun. 1987, 1708.
(10) Ochiai, M.; Uemura, K.; Oshima, K.; Masaki, Y.; Kunishima,
M.; Tani, S. Tetrahedron Lett. 1991, 32, 4753.
Ster eoch em istr y of 1,2-Bis(ben zen esu lfon yl)a lk -
en es 5. NOE studies of 5 indicate that both of the double
nucleophilic vinylic substitutions of a phenyliodonio
group and a â-halogen atom (Cl or Br) of 2 or 3 with
sodium benzenesulfinate occur with retention of config-
(11) Ochiai, M.; Oshima, K.; Masaki, Y. Chem. Lett. 1994, 871.

Câ Michael Addition to Alkenyliodonium Salts
J . Org. Chem., Vol. 62, No. 23, 1997 8003
F igu r e 1. NOE measurements of 5.
uration. The results of measurements of an NOE en-
hancement between the vinylic and allylic protons of 5
are shown in Figure 1. Irradiation of the allylic protons
in (Z)-5b,c resulted in 8-9% enhancements in the vinylic
proton integration whereas only 2-3% enhancements
were observed with (E)-5b,c,12 which is in good agree-
ment with their assigned stereochemistry. The observed
chemical shifts of vinylic protons in 5 support their
stereochemical assignments: vinylic proton signals of (Z)-
5b,c appeared at δ 6.76 whereas those of (E)-5b,c
appeared at δ 7.38.13 The structure of (E)-5b was
established by a single-crystal X-ray analysis22 (see
Supporting Information).
Tim e Cou r ses of Nu cleop h ilic Vin ylic Su bstitu -
tion . A. Rea ction of â-Ch lor oiod on iu m Sa lt 2b. To
gain insight into the mechanism of this nucleophilic
vinylic substitution of (Z)-(â-haloalkenyl)iodonium salts
with sodium benzenesulfinate, we investigated the time
1
courses of the reactions by H NMR in CDCl3 at room
temperature. Changing the solvent from THF to CDCl3
was found to slow the rate of the reaction of (Z)-(2-chloro-
1-decenyl)iodonium salt 2b (Figure 2a). Most impor-
tantly, formation of considerable amounts (up to 18%) of
the (Z)-(â-(benzenesulfonyl)alkenyl)iodonium salt 9b (X
) BF4, PhSO2, or Cl) was detected by 1H NMR, especially
at the early stages of the reaction. The amounts of (Z)-
9b gradually decrease with an increase in the yields of
the (Z)-1,2-bis(benzenesulfonyl)alkene 5b, indicating that
the â-sulfonyliodonium salt (Z)-9b would be an interme-
diate leading to the formation of (Z)-5b. Furthermore,
formation of a small amount of the (Z)-chlorovinyl sulfone
6b was observed during the late stages of the reaction.
It was possible to isolate the intermediate (Z)-9b (X )
BF4). When the reaction of 2b was carried out using one
equiv of sodium benzenesulfinate in THF at 0 °C for 12
h and quenched with an aqueous NaBF4 solution, a
mixture of 2b (54%), (Z)-9b (X ) BF4, 11%),3d (Z)-5b
(34%), and 6b (1%) was produced (Scheme 3). For
purification, the â-sulfonyliodonium salt (Z)-9b (X ) BF4)
could not be applied to silica gel column chromatography,
because it readily decomposes to generate an alkylidene-
carbene 10b via R-elimination yielding 1-(benzenesulfo-
nyl)cyclopentene 11. Repeated recrystallization (more
F igu r e 2. Time courses for the reaction of (Z)-(2-halo-1-
decenyl)iodonium tetrafluoroborates with sodium benzene-
sulfinate (2.5 equiv) in CDCl3 at room temperature. Yields
1
were determined by H NMR. (a) Reaction of 2b. Symbols are
% recovered 2b (O), (Z)-5b (0), 6b (4), and (Z)-9b (b). (b)
Reaction of 3b. Symbols are % recovered 3b (O), (Z)-5b (0),
7b (2), and (Z)-9b (b). (c) Reaction of 4b. Symbols are %
recovered 4b (O), (E)-5b (0), (Z)-5b (9), and 11 (2).
Sch em e 3
(12) Hinkle, R. J .; Stang, P. J . Synthesis 1994, 313.
(13) (a) Stirling, C. J . M. J . Chem. Soc. 1964, 5856. (b) Reddy, M.
V. R.; Naidu, M. S. R. Acta Chim. Hung. 1984, 117, 153. (c) Andrisano,
R.; Angeloni, A. S.; Fini, A. Tetrahedron 1972, 28, 2681. (d) J ulia, M.;
Lauron, H.; Stacino, J .-P.; Verpeaux, J .-N. Tetrahedron 1986, 42, 2475.
(e) Kobayashi, T.; Tanaka, Y.; Ohtani, T.; Kinoshita, H.; Inomata, K.;
Kotake, H. Chem. Lett. 1987, 1209. (f) Ueno, Y.; Setoi, H.; Okawara,
M. Chem. Lett. 1979, 47.
than 10 times) of a mixture of 2b and (Z)-9b from
hexane-diethyl ether-dichloromethane permitted isola-
tion of the pure (Z)-9b (X ) BF4). The intermediate

8004 J . Org. Chem., Vol. 62, No. 23, 1997
Shiro and Ochiai
Ta ble 3. Com p etitive Rea ction of
formation of the â-sulfonyliodonium salt (Z)-9b from the
â-chloroiodonium salt 2b clearly indicates that these
nucleophilic vinylic substitutions involve a Michael ad-
dition of a nucleophile (PhSO2-) to the alkenyliodonium
salt 2b at the Câ atom, followed by elimination of a
chloride anion yielding (Z)-9b. Such a Michael addition
has not been reported previously.
(Z)-â-Su lfon yliod on iu m Sa lt (Z)-9b (X ) BF 4) w ith Ha lid e
a n d Ben zen esu lfin a te An ion sa
product (yield,b %)
entry
nucleophile
time, h (Z)-5b
6b
7b
1
2
3
4
5
6
n-Bu4NSO2Ph, n-Bu4NCl
n-Bu4NSO2Ph, n-Bu4NBr
n-Bu4NCl, n-Bu4NBr
PhSO2Na, NaCl
PhSO2Na, NaBr
NaCl, NaBr
9
7
14
2
2
12
(93)
(92)
(6)
(82)
(71)
(77)
(9)
It has been shown that nucleophilic vinylic substitu-
tions of (Z)-9b (X ) BF4) with sodium benzenesulfinate
proceed at 0 °C in THF with retention of configuration
and afford (Z)-5b stereoselectively in high yields.7b
Hypothesizing that the substitution of (Z)-9b with so-
dium benzenesulfinate would compete with the attack
of a chloride ion, liberated upon the formation of (Z)-9b
from 2b, we anticipated the formation of a small amount
of the (Z)-chlorovinyl sulfone 6b, produced by nucleophilic
substitution of (Z)-9b with a chloride ion (with retention
of configuration).7a
(19)
(88)
a
Reactions were carried out using 20 equiv each of two
competing nucleophiles at 0 °C. Solvent: THF-dichloromethane
b
(10:1) for entries 1 to 3; THF for entries 4 to 6. Isolated yields.
Sch em e 4
B. Rea ction of â-Br om oiod on iu m Sa lt 3b. The
time course of the nucleophilic substitution of (Z)-(2-
bromo-1-decenyl)iodonium salt 3b in CDCl3 at room
temperature is shown in Figure 2b. As in the case of
the â-chloroiodonium salt 2b, at the early stages of the
reaction of 3b, formation of considerable amounts (up to
19%) of the (Z)-â-sulfonyliodonium salt 9b (X ) BF4,
tivities decrease in the order of PhSO2Na > NaBr >
NaCl, which is compatible with the results shown in
Table 2 and Figure 2. In the reactions of 2b or 3b with
sodium benzenesulfinate, formation of (Z)-9b will be
accompanied by generation of NaCl or NaBr via Michael
addition followed by halide ion extrusion. The high
degree of ion pair dissociation expected for NaBr com-
pared to NaCl in THF probably accounts for this reversal
in reactivity order.15 No interconversion among (Z)-5b,
6b, and 7b in the presence of these nucleophiles (PhSO2-
Na, NaBr, or NaCl) in THF at room temperature was
observed.
1
PhSO2, or Br) was observed by H NMR. The amounts
of (Z)-9b gradually decrease with an increase in the yields
of the (Z)-1,2-bis-sulfone 5b and with formation of the
(Z)-bromovinyl sulfone 7b. These results suggest that
the â-sulfonyliodonium salt (Z)-9b might be a common
intermediate leading to the formation of (Z)-5b as well
as 7b. The intermediate formation of (Z)-9b provides
additional evidence for a Michael addition of a nucleo-
phile (PhSO2-) to the alkenyliodonium salt at the Câ
atom.
C. Rea ction of â-F lu or oiod on iu m Sa lt 4b. The
time course of the nucleophilic vinylic substitution of (Z)-
(â-fluoro-1-decenyl)iodonium salt 4b with sodium ben-
zenesulfinate is shown in Figure 2c. In this reaction, no
intermediate formation of the (Z)-â-sulfonyliodonium salt
It is generally accepted that the order of nucleophilic
reactivities of halide anions in dipolar aprotic solvents
such as DMF, DMSO, and acetone, where solvation due
to hydrogen bonding is negligible, is Cl- > Br- > I-.14
This reactivity sequence would suggest that the forma-
tion of the (Z)-chlorosulfone 6b would be larger than that
of the (Z)-bromosulfone 7b, but this was not the case.
Compared to 6b, a large amount of 7b was produced in
the reaction of 3b both in THF (compare Table 2, entries
2 and 9) and in CDCl3 (compare Figures 2a and 2b). For
1
9b was detected by H NMR. The reaction in CDCl3 is
slow and takes more than 150 h at room temperature.
The major product of this reaction was found to be a
stereoisomeric mixture of (Z)- and (E)-bis-sulfones 5b,
but, unexpectedly, we observed formation of a consider-
able amount of the 1-(benzenesulfonyl)cyclopentene 11,
which was not detected in the reaction in THF (Table 2,
entry 11).
Formation of the â-sulfonyliodonium salt (Z)-9b was
not detected directly, but isolation of the 1-(benzenesulfo-
nyl)cyclopentene 11 strongly suggests the intermediacy
of 9b in the nucleophilic vinylic substitution of 4b, since
it has been shown that (Z)-9b (X ) BF4) reacts with
n-Bu4NF in dichloromethane at room temperature, un-
dergoing R-elimination to generate the alkylidenecarbene
10b that affords the sulfonylcyclopentene 11 via in-
tramolecular 1,5-carbon-hydrogen insertion (Scheme
4).7a
Rea ction Mech a n ism . As illustrated in Scheme 5,
a reaction mechanism for the double nucleophilic vinylic
substitutions of (Z)-(2-chloro-1-decenyl)iodonium salt 2b
with sodium benzenesulfinate might be assumed to
involve the following addition-elimination process two
times: (a) Michael addition of benzenesulfinate anion to
the â-chloroiodonium salt 2b at the Câ atom, followed by
elimination of chloride anion yielding (Z)-9b, (b) Michael
this reason, we measured the relative reactivities of
halide (Cl- and Br-) and benzenesulfinate anions (PhSO2
)
-
toward nucleophilic substitutions of the intermediate
â-sulfonyliodonium salt (Z)-9b (X ) BF4). Competitive
reactions were carried out using 20-fold excess each of
two competing nucleophiles at 0 °C. The relative nu-
cleophilic reactivities of these anions are summarized in
Table 3. The rates of substitution of (Z)-9b with tet-
rabutylammonium salts in THF-dichloromethane (10:
1) decrease in the order of n-Bu4NSO2Ph . n-Bu4NCl >
n-Bu4NBr. This order of nucleophilic reactivities is in a
good agreement with the one previously reported,14 but
not with our results obtained in the reactions of 2b and
3b. Reverse order of the rates in the substitution of (Z)-
9b with halides, however, was observed, when sodium
halides were used instead of tetrabutylammonium ha-
lides in THF (Table 3, entries 4-6). The relative reac-
(14) (a) Puar, M. S. J . Chem. Educ. 1970, 47, 473. (b) Winstein, S.;
Savedoff, L. G.; Smith, S.; Stevens, I. D. R.; Gall, J . S. Tetrahedron
Lett. 1960, 24. (c) Weaver, W. M.; Hutchison, J . D. J . Am. Chem. Soc.
1964, 86, 261.
(15) It has been shown that the extent of ion pairing decreases with
increasing ionic size.14a

Câ Michael Addition to Alkenyliodonium Salts
J . Org. Chem., Vol. 62, No. 23, 1997 8005
Sch em e 5
that of 2b. Although formation of the â-sulfonyliodonium
salt 9b was not detected directly by 1H NMR, we assumed
that a similar Michael addition of benzenesulfinate anion
to the Câ atom generating the iodonium ylide 14, shown
in Scheme 6, was involved in the nucleophilic vinylic
substitutions of the â-fluoroiodonium salt 4b. Because
of the poor nucleofugality of the fluorine atom,20 the
iodonium ylide 14 seems to be relatively long-lived, and,
therefore, the conformer 15 formed by 60° clockwise
rotation and the conformer 16 formed by 120° counter-
clockwise rotation will have enough time to equilibrate
to some extent, thereby leading to formation of (Z)- and
(E)-9b, respectively. Similar dependence on halogen
nucleofuges has been reported in the nucleophilic sub-
stitution of p-nitro-â-bromo- and p-nitro-â-fluorostyrenes
with thiophenoxide ion: (E)- and (Z)-â-bromostyrenes
with a good nucleofuge give the retained 4-nitrostyryl
phenyl sulfides, whereas (E)- and (Z)-â-fluorostyrenes
with a poor nucleofuge result in stereoconvergence.16b,21
As described above, isolation of the 1-(benzenesulfonyl)-
cyclopentene 11 in the reaction of 4b in CDCl3 strongly
suggests the intermediacy of the â-sulfonyliodonium salt
9b. Although there is no firm evidence, it is reasonable
to assume that (E)-9b will produce the (E)-1,2-bis-sulfone
5b by reacting with the benzenesulfinate anion and to
generate the alkylidenecarbene 10b via fluoride anion-
induced R-elimination, as shown in Scheme 6.
addition of benzenesulfinate or chloride anion to the
â-(benzenesulfonyl)iodonium salt (Z)-9b at the CR atom,
followed by reductive elimination of the phenyliodonio
group yielding (Z)-5b or 6b, respectively.
Perpendicular attack of benzenesulfinate anion to the
π* orbital of the â-chloroiodonium salt 2b will produce
the iodonium ylide 12. Effects of negative hyperconju-
gation between the leaving group (Cl) and the carbanionic
electron pair in the iodonium ylide 12 account for the
preference of the internal 60° clockwise rotation over the
120° counterclockwise rotation of 12, thereby yielding (Z)-
9b stereoselectively with retention of configuration via
the expulsion of the good nucleofuge (Cl).16,17 In the
reaction of the alkenyliodonium salt 2h , the perpendicu-
lar attack of benzenesulfinate anion will be hindered by
a sterically demanding tert-butyl group at the â-position,
which slows down the rate of the reaction and makes the
nucleophilic vinylic substitution at the CR atom, yielding
8 a preferred reaction course.
The latter Michael addition of benzenesulfinate or
chloride anion to the â-sulfonyliodonium salt (Z)-9b at
the CR atom has been reported.7a,b This substitution also
proceeds with retention of stereochemistry, because of
hyperconjugative stabilization of the intermediate R-sul-
fonyl-stabilized carbanion 13 by the C-I(III) orbital.
Alternatively, a ligand coupling mechanism of (Z)-9b (X
) PhSO2, or Cl) yielding (Z)-5b or 6b is also compatible
with the stereochemical outcome observed in this nu-
cleophilic vinylic substitution.18
Con clu sion s
Reaction of (Z)-(â-haloalkenyl)phenyliodonium tetraflu-
oroborates with sodium benzenesulfinate in THF pre-
dominantly undergoes double nucleophilic vinylic sub-
stitution of a phenyliodonio group and a â-halogen atom
and affords (Z)-1,2-bis(benzenesulfonyl)alkene, its (E)-
isomer, and/or (Z)-halovinyl sulfone, depending on the
nature of a â-halogen atom (nucleophilicity and nucle-
ofugality). Isolation and characterization of the inter-
mediate (Z)-(â-(benzenesulfonyl)alkenyl)iodonium salt
strongly suggest that the double nucleophilic vinylic
substitution involves a hitherto unobserved Michael
addition of benzenesulfinate anion to (â-haloalkenyl)-
iodonium salts at the Câ atom as a first step of the
reactions.
Exp er im en ta l Section
As an alternative mechanism for the reaction of 2b,
an anti â-elimination pathway19 of HCl involving inter-
mediacy of 1-decynyl(phenyl)iodonium salt 1b, followed
by the Michael addition of sodium benzenesulfinate,
should be considered. This pathway does not seem to be
important, however, given that the reaction of 1-decynyl-
(phenyl)iodonium salt 1b with sodium benzenesulfinate
will directly generate an R-(phenylsulfonyl)alkyliden-
ecarbene 10b, but will not produce (Z)-5b.3d
Gen er a l. For general experimental detail, see ref 4.
Preparative thin-layer chromatography (TLC) was carried out
on precoated plates of silica gel (Merck, silica gel F-254).
Kieselgel 60 (Merck, 230-400 mesh) was used for flash
chromatography. Sodium benzenesulfinate dihydrate and
lithium halides are commercially available and were used as
received. 1-Alkynyl(phenyl)iodonium tetrafluoroborates 1 were
prepared from the corresponding alkynyltrimethylsilanes by
the reaction with iodosylbenzene and BF3-Et2O in dichlo-
romethane according to literature procedure.9
Nucleophilic vinylic substitutions of the â-bromoiodo-
nium salt 3b will involve the same reaction pathway as
Gen er a l P r oced u r e for Syn th esis of (Z)-(â-Ch lor oa lk -
en yl)- 2 a n d (Z)-(â-Br om oa lk en yl)p h en yliod on iu m Tet-
r a flu or obor a tes 3.10 To a stirred solution of lithium chloride
or lithium bromide (5 mmol) in acetic acid (20 mL) was added
(16) For reviews of nucleophilic vinylic substitutions, see: (a)
Rappoport, Z. Adv. Phys. Org. Chem. 1969, 7, 1. (b) Modena, G. Acc.
Chem. Res. 1971, 4, 73. (c) Miller, S. I. Tetrahedron 1977, 33, 1211.
(d) Rappoport, Z. Acc. Chem. Res. 1981, 14, 7. (e) Rappoport, Z. Recl.
Trav. Chim. Pays-Bas 1985, 104, 309. (f) Shainyan, B. A. Usp. Khim.
1986, 55, 942. (g) Rappoport, Z. Acc. Chem. Res. 1992, 25, 474.
(17) Apeloig, Y.; Rappoport, Z. J . Am. Chem. Soc. 1979, 101, 5095.
(18) (a) Oae, S.; Uchida, Y. Acc. Chem. Res. 1991, 24, 202. (b)
Furukawa, N.; Ogawa, S.; Matsumura, K.; Fujihara, H. J . Org. Chem.
1991, 56, 6341.
(20) Stang, P. J .; Hanack, M.; Subramanian, L. R. Synthesis 1982,
85.
(21) (a) Marchese, G.; Modena, G.; Naso, F. Tetrahedron 1968, 24,
663. (b) Marchese, G.; Modena, G.; Naso, F. J . Chem. Soc. (B) 1969,
290.
(22) The author has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
(19) Ochiai, M.; Uemura, K.; Masaki, Y. J . Am. Chem. Soc. 1993,
115, 2528.

8006 J . Org. Chem., Vol. 62, No. 23, 1997
Shiro and Ochiai
Sch em e 6
1-alkynyl(phenyl)iodonium tetrafluoroborate 1 (0.5 mmol) at
room temperature, and the solution was stirred for the periods
shown in Table 1. The solvent was evaporated under reduced
pressure. After addition of water, the mixture was extracted
with dichloromethane two times. The combined organic
extracts were vigorously shaken with a saturated aqueous
sodium tetrafluoroborate solution (10 mL) two times. The
organic layer was filtered and concentrated under aspirator
vacuum to give an oil, which was washed several times with
hexane and/or diethyl ether by decantation at -78 °C. Further
purification of (Z)-(â-haloalkenyl)iodonium tetrafluoroborates
2 and 3 was accomplished by recrystallization from dichlo-
romethane-hexane. The yields of pure products are given in
Table 1.
(Z)-(2-Ch lor o-5-ph en yl-1-pen ten yl)ph en yliodon iu m tet-
r a flu or obor a te (2e): colorless leaflets; mp 103-104 °C; IR
1
(KBr) 3071, 1586, 1442, 1085, 737 cm-1; H NMR (CDCl3) δ
8.02 (br d, J ) 7.7 Hz, 2H), 7.63 (br t, J ) 7.3 Hz, 1H), 7.47
(br dd, J ) 7.7, 7.3 Hz, 2H), 7.31-7.09 (6H), 2.73 (t, J ) 7.6
Hz, 2H), 2.60 (t, J ) 7.3 Hz, 2H), 1.95 (m, 2H); FAB MS m/z
383 [(M - BF4)+]; HRMS (FAB) calcd for C17H17ClI [(M -
BF4)+] 383.0064, found 383.0074. Anal. Calcd for C17H17
BClF4I: C, 43.40; H, 3.64. Found: C, 43.17; H, 3.57.
-
(Z)-(2,5-Dich lor o-1-pen ten yl)ph en yliodon iu m tetr aflu -
or obor a te (2f): oil; IR (Nujol) 1580, 1455, 1035 cm-1; 1H NMR
(CDCl3) δ 8.05 (br d, J ) 8.3 Hz, 2H), 7.66 (br t, J ) 7.5 Hz,
1H), 7.50 (br dd, J ) 8.3, 7.5 Hz, 2H), 7.32 (s, 1H), 3.53 (t, J
) 6.2 Hz, 2H), 2.94 (t, J ) 7.1 Hz, 2H), 2.11 (m, 2H); FAB MS
m/z 341 [(M - BF4)+]; HRMS (FAB) calcd for C11H12Cl2I
[(M - BF4)+] 340.9361, found 340.9379. Anal. Calcd for
C11H12BCl2F4I: C, 30.81; H, 2.82. Found: C, 31.26; H, 2.82.
(Z)-(2-Ch lor o-3-cyclop en t yl-1-p r op en yl)p h en yliod o-
n iu m tetr a flu or obor a te (2 g):19 pale yellow crystals; mp
68-70 °C; IR (Nujol) 2720, 1585, 1560, 1145, 1040, 965, 715
cm-1; 1H NMR (CDCl3) δ 8.04 (br d, J ) 7.8 Hz, 2H), 7.62 (br
t, J ) 7.3 Hz, 1H), 7.47 (br dd, J ) 7.8, 7.3 Hz, 2H), 7.23 (s,
1H), 2.69 (d, J ) 7.3 Hz, 2H), 2.16 (septet, J ) 7.7 Hz, 1H),
1.80-1.41 (m, 6H), 1.19-0.95 (m, 2H); 13C NMR (CDCl3) δ
156.5 (s), 135.3 (d), 132.4 (d), 132.1 (d), 113.1 (s), 97.8 (d), 45.7
(t), 38.2 (d), 31.7 (t), 24.9 (t). Anal. Calcd for C14H17BClF4I:
C, 38.70; H, 3.94. Found: C, 38.98; H, 4.00.
(Z)-(2-Ch lor o-3,3-d im et h yl-1-b u t en yl)p h en yliod on -
iu m tetr a flu or obor a te (2h ): colorless crystals; mp 124-125
°C; IR (KBr) 2981, 1578, 1474, 1445, 1239, 1085, 739 cm-1; 1H
NMR (CDCl3) δ 8.05 (br d, J ) 7.7 Hz, 2H), 7.64 (br t, J ) 7.3
Hz, 1H), 7.49 (br dd, J ) 7.7, 7.3 Hz, 2H), 7.14 (s, 1H), 1.32 (s,
9H); FAB MS m/z 321 [(M - BF4)+]; HRMS (FAB) calcd for
C12H15ClI [(M - BF4)+] 320.9907, found 320.9926. Anal. Calcd
for C12H15BClF4I: C, 35.29; H, 3.70. Found: C, 35.28; H, 3.46.
(Z)-(2-Br om o-1-d ecen yl)p h en yliod on iu m t et r a flu o-
r obor a te (3b):19 colorless crystals; mp 70-71 °C; IR (Nujol)
2720, 1580, 1560, 1160, 1030, 980, 715 cm-1; 1H NMR (CDCl3)
δ 8.07 (br d, J ) 8.0 Hz, 2H), 7.68 (br t, J ) 7.1 Hz, 1H), 7.52
(br dd, J ) 8.0, 7.1 Hz, 2H), 7.43 (s, 1H), 2.79 (t, J ) 7.1 Hz,
2H), 1.7-1.5 (m, 2H), 1.34-1.15 (m, 10H), 0.87 (t, J ) 6.6 Hz,
3H). Anal. Calcd for C16H23BBrF4I: C, 37.76; H, 4.55.
Found: C, 37.68; H, 4.56.
(Z)-(2-Ch lor o-1-p r op en yl)p h en yliod on iu m tetr a flu o-
r obor a te (2a ): colorless needles; mp 118-123 °C; IR (KBr)
3072, 1595, 1564, 1471, 1444, 1084, 742 cm-1; 1H NMR (CDCl3)
δ 8.04 (br d, J ) 8.3 Hz, 2H), 7.64 (br t, J ) 7.3 Hz, 1H), 7.49
(br dd, J ) 8.3, 7.3 Hz, 2H), 7.23 (q, J ) 1.2 Hz, 1H), 2.54 (d,
J ) 1.2 Hz, 3H); FAB MS m/z 279 [(M - BF4)+]; HRMS (FAB)
calcd for C9H9ClI [(M - BF4)+] 278.9438, found 278.9448.
(Z)-(2-Ch lor o-1-d ecen yl)p h en yliod on iu m t et r a flu o-
r obor a te (2b):19 colorless needles; mp 73-76 °C; IR (Nujol)
1
3070, 1595, 1565, 1285, 1165, 1045, 985, 735 cm-1; H NMR
(CDCl3) δ 8.04 (br d, J ) 8.0 Hz, 2H), 7.66 (br t, J ) 7.0 Hz,
1H), 7.50 (br dd, J ) 8.0, 7.0 Hz, 2H), 7.15 (s 1H), 2.72 (t, J )
7.6 Hz, 2H), 1.71-1.52 (m, 2H), 1.34-1.13 (m, 12H), 0.87 (t, J
) 6.8 Hz, 3H); 13C NMR (CDCl3) δ 157.8 (s), 135.4 (d), 132.7
(d), 132.3 (d), 111.6 (s), 96.0 (d), 39.8 (t), 31.7 (t), 29.0 (t), 28.3
(t), 27.5 (t), 22.5 (t), 14.0 (q); MS m/z (relative intensity) 300
[7, (M - BF4)+], 204 (87), 77 (100). Anal. Calcd for C16H23
BClF4I: C, 41.37; H, 4.99. Found: C, 41.39; H, 4.96.
-
(Z)-(2-Ch lor o-5-m eth yl-1-h exen yl)ph en yliodon iu m tet-
r a flu or obor a te (2c): colorless needles; mp 57-58 °C; IR
(KBr) 2957, 1599, 1471, 1441, 1063, 736 cm-1; 1H NMR (CDCl3)
δ 8.04 (br d, J ) 7.7 Hz, 2H), 7.66 (br t, J ) 7.3 Hz, 1H), 7.50
(br dd, J ) 7.7, 7.3 Hz, 2H), 7.20 (s, 1H), 2.73 (t, J )6.6 Hz,
2H), 1.61-1.45 (m, 3H), 0.88 (d, J )5.8 Hz, 6H); FAB MS m/z
335 [(M - BF4)+]; HRMS (FAB) calcd for C13H17ClI [(M -
BF4)+] 335.0064, found 335.0074. Anal. Calcd for C13H17
BClF4I: C, 36.96; H, 4.06. Found: C, 37.00; H, 4.06.
-
(Z)-(2-Ch lor o-4-ph en yl-1-bu ten yl)ph en yliodon iu m tet-
r a flu or obor a te (2d ): colorless leaflets; mp 85-86 °C; IR
(KBr) 3090, 1595, 1471, 1450, 1084, 740 cm-1; 1H NMR (CDCl3)
δ 7.81 (br d, J ) 7.6 Hz, 2H), 7.64 (br t, J ) 7.3 Hz, 1H), 7.45
(br dd, J ) 7.6, 7.3 Hz, 2H), 7.25-7.06 (m, 5H), 6.98 (s, 1H),
3.13-3.00 (m, 2H), 3.00-2.87 (m, 2H); FAB MS m/z 369 [(M
- BF4)+]; HRMS (FAB) calcd for C16H15ClI [(M - BF4)+]
368.9907, found 368.9920. Anal. Calcd for C16H15BClF4I: C,
42.10; H, 3.31. Found: C, 42.06; H, 3.29.
(Z)-(2-Br om o-5-m eth yl-1-h exen yl)ph en yliodon iu m tet-
r a flu or obor a te (3c): oil; IR (Nujol) 3045, 1630, 1580, 1465,
1050 cm-1 1H NMR (CDCl3) δ 8.07 (br d, J ) 8.5 Hz, 2H),
;
7.61 (br t, J ) 7.0 Hz, 1H), 7.54-7.47 (m, 3H), 2.78 (t, J ) 7.3
Hz, 2H), 1.79-1.47 (m, 3H), 0.88 (d, J ) 6.0 Hz, 6H); FAB MS
m/z 381, 379 [(M - BF4)+]; HRMS (FAB) calcd for C13H17BrI
[(M - BF4)+] 378.9558, found 378.9564.

Câ Michael Addition to Alkenyliodonium Salts
J . Org. Chem., Vol. 62, No. 23, 1997 8007
Syn th esis of (Z)-(2-F lu or o-1-d ecen yl)p h en yliod on iu m
Tetr a flu or obor a te (4b).11 To a stirred solution of (1-decy-
nyl)phenyliodonium tetrafluoroborate (1b) (699 mg, 1.63 mmol)
in acetone (2 mL) and dichloromethane (2 mL) was added a
solution of CsF (496 mg, 3.27 mmol) in H2O (0.59 mL, 33 mmol)
at room temperature, and the solution was stirred for 9 h. After
addition of water, the mixture was extracted with dichlo-
romethane, and the combined organic extracts were washed
with water and brine (× 3). The organic layer was filtered
and concentrated under aspirator vacuum to give an oil, which
was washed several times with hexane by decantation at -78
°C to give (Z)-(2-fluoro-1-decenyl)phenyliodonium chloride (157
mg, 24%) as colorless crystals: mp 114-117 °C (recrystallized
from dichloromethane-hexane); IR (Nujol) 1640, 1560, 1150,
organic phase was washed with water and brine. The solution
was dried over anhydrous Na2SO4 and concentrated to give
an oil, which was purified by preparative TLC. The yields of
pure products are given in Table 2.
(Z)-1,2-Bis(ben zen esu lfon yl)-1-p r op en e (5a ): colorless
needles; mp 113-115 °C (recrystallized from dichloromethane-
hexane) (lit.13a mp 113-114.5 °C); IR (KBr) 3007, 1583, 1447,
1323, 1163, 1084, 723, 690 cm-1 1H NMR (CDCl3) δ 8.11-
;
8.03 (m, 4H), 7.74-7.54 (m, 6H), 6.82 (q, J ) 1.3 Hz, 1H), 2.12
(d, J ) 1.3 Hz, 3H); MS m/z (relative intensity) 322 (2, M+),
258 (5), 218 (66), 141 (51), 125 (100), 77 (98).
(Z)-1,2-Bis(ben zen esu lfon yl)-1-d ecen e (5b):7b colorless
needles; mp 91.8-92.2 °C (recrystallized from dichloromethane-
hexane); IR (KBr) 2930, 2850, 1450, 1325, 1150, 720, 630 cm-1
;
1
1105, 985, 730 cm-1; H NMR (CDCl3) δ 8.03 (br d, J ) 7.9
1H NMR (CDCl3) δ 8.09 (br d, J ) 7.5 Hz, 2H), 8.03 (br d, J )
7.5 Hz, 2H), 7.72-7.64 (m, 2H), 7.62-7.55 (m, 4H), 6.76 (t, J
) 1.4 Hz, 1H), 2.40 (dt, J ) 1.4, 7.7 Hz, 2H), 1.45-1.36 (m,
2H), 1.30-1.14 (m, 10H), 0.87 (t, J ) 6.8 Hz, 3H); 13C NMR
(CDCl3) δ 154.2, 141.4, 138.6, 138.4, 134.4, 133.8, 129.3, 129.0,
129.0, 128.2, 33.5, 31.7, 29.0, 28.7, 28.2, 22.5, 14.0; MS m/z
(relative intensity) 420 (1, M+), 279 (80), 218 (18), 143 (82),
137 (60), 125 (100), 77 (74); HRMS calcd for C22H28O4S2 (M+)
420.1429, found 420.1458. Anal. Calcd for C22H28O4S2: C,
62.82; H, 6.71. Found: C, 62.78; H, 6.73.
Hz, 2H), 7.52 (br t, J ) 6.9 Hz, 1H), 7.39 (br dd, J ) 7.9, 6.9
Hz, 2H), 6.16 (d, J HF ) 35.5 Hz, 1H), 2.47 (dt, J ) 6.9 Hz, J HF
) 15.5 Hz, 2H), 1.72-1.45 (m, 2H), 1.40-1.10 (m, 10H), 0.87
(t, J ) 6.4 Hz, 3H); 13C NMR (CDCl3) δ 170.2 (J CF ) 274 Hz),
134.4, 131.0, 130.7, 119.6, 82.8 (J CF ) 24 Hz), 32.2 (J CF ) 24
Hz), 31.6, 28.9, 28.5, 25.5, 22.5, 13.9; MS m/z (relative
intensity) 284 [30, (M - Ph-Cl)+], 204 (66), 112 (83), 77 (100).
Anal. Calcd for C16H23ClFI: C, 48.44; H, 5.84. Found: C,
48.16; H, 5.76.
This (â-fluorovinyl)iodonium chloride (30 mg, 0.076 mmol)
was dissolved in dichloromethane (15 mL), and the solution
was vigorously shaken with a saturated aqueous sodium
tetrafluoroborate solution (5 mL) four times. The organic layer
was filtered and concentrated under aspirator vacuum to give
an oil, which was washed several times with hexane by
decantation at -78 °C to give the (â-fluorovinyl)iodonium
tetrafluoroborate 4b (29 mg, 86%) as white solids: IR (KBr)
(E)-1,2-Bis(ben zen esu lfon yl)-1-d ecen e (5b): colorless
plates; mp 76-78 °C (recrystallized from dichloromethane-
hexane); IR (CHCl3) 2925, 2850, 1720, 1325, 1155, 1085 cm-1
;
1H NMR (CDCl3) δ 7.94 (br d, J ) 7.7 Hz, 2H), 7.85 (br d, J )
7.0 Hz, 2H), 7.81-7.54 (m, 6H), 7.38 (s, 1H), 2.75-2.67 (m,
2H), 1.52-1.16 (m, 12H), 0.88 (t, J ) 6.8 Hz, 3H); 13C NMR
(CDCl3) δ 155.0, 139.7, 137.3, 135.2, 134.5, 129.7, 129.6, 128.8,
127.9, 31.8, 29.9, 29.0, 28.9, 27.1, 22.6, 14.1; MS m/z (relative
intensity) 420 (0.2, M+), 279 (100), 143 (45), 137 (30), 77 (45);
HRMS calcd for C22H28O4S2 (M+) 420.1429, found 420.1437.
Anal. Calcd for C22H28O4S2: C, 62.82; H, 6.71. Found: C,
62.54; H, 6.77.
(Z)-1,2-Bis(ben zen esu lfon yl)-5-m eth yl-1-h exen e (5c): col-
orless plates; mp 103-104 °C (recrystallized from dichlo-
romethane-hexane); IR (CHCl3) 2960, 2880, 1595, 1450, 1330,
1155, 1090 cm-1; 1H NMR (CDCl3) δ 8.12-8.01 (m, 4H), 7.81-
7.53 (m, 6H), 6.76 (t, J ) 1.5 Hz, 1H), 2.41 (br dt, J ) 1.5, 7.7
Hz, 2H), 1.57-1.22 (m, 3H), 0.82 (d, J ) 6.5 Hz, 6H); MS m/z
(relative intensity) 378 (0.6, M+), 237 (59), 218 (32), 143 (61),
125 (98), 95 (70), 77 (100); HRMS calcd for C19H22O4S2 (M+)
378.0960, found 378.0941. Anal. Calcd for C19H22O4S2: C,
60.29; H, 5.86. Found: C, 60.55; H, 6.07.
(E)-1,2-Bis(b en zen esu lfon yl)-5-m et h yl-1-h exen e (5c):
colorless plates; mp 87-88 °C (recrystallized from dichlo-
romethane-hexane); IR (CHCl3) 2950, 2875, 1615, 1590, 1450,
1325, 1155, 1085 cm-1; 1H NMR (CDCl3) δ 7.94 (br d, J ) 7.7
Hz, 2H), 7.85 (br d, J ) 7.7 Hz, 2H), 7.75-7.55 (m, 6H), 7.38
(s, 1H), 2.75-2.66 (m, 2H), 1.61-1.20 (m, 3H), 0.83 (d, J )
6.6 Hz, 6H); MS m/z (relative intensity) 378 (0.1, M+), 237
(100), 143 (43), 95 (26), 77(50); HRMS calcd for C19H22O4S2
(M+) 378.0960, found 378.0941. Anal. Calcd for C19H22O4S2:
C, 60.29; H, 5.86. Found: C, 60.03; H, 5.74.
1
2929, 1651, 1472, 1440, 1084, 738 cm-1; H NMR (CDCl3) δ
8.02 (br d, J ) 7.9 Hz, 2H), 7.60 (br t, J ) 7.6 Hz, 1H), 7.48
(br dd, J ) 7.9, 7.6 Hz, 2H), 6.53 (d, J HF ) 33.2 Hz, 1H), 2.53
(dt, J ) 7.7 Hz, J HF ) 16.9 Hz, 2H), 1.62-1.16 (m, 12H), 0.87
(t, J ) 6.8 Hz, 3H); FAB MS m/z 361 [(M - BF4)+]; HRMS
(FAB) calcd for C16H23FI [(M - BF4)+] 361.0829, found
361.0837. Anal. Calcd for C16H23BF5I: C, 42.89; H, 5.17.
Found: C, 42.92; H, 5.07.
Syn th esis of (Z)-(2-F lu or o-5-m eth yl-1-h exen yl)p h e-
n yliod on iu m Tetr a flu or obor a te (4c). In a similar manner,
(Z)-(2-fluoro-5-methyl-1-hexenyl)phenyliodonium chloride was
prepared in 15% yield from (5-methyl-1-hexynyl)phenyliodo-
nium tetrafluoroborate (1c) (500 mg, 1.30 mmol), CsF (394 mg,
2.60 mmol), and H2O (0.47 mL, 26 mmol) in acetone (1 mL)
and dichloromethane (1 mL): white powder: mp 137-141 °C;
IR (KBr) 2958, 1657, 1567, 1472, 1441, 1368, 739 cm-1 1H
;
NMR (CDCl3) δ 8.02 (br d, J ) 8.2 Hz, 2H), 7.52 (br t, J ) 7.0
Hz, 1H), 7.38 (br dd, J ) 8.2, 7.0 Hz, 2H), 6.17 (d, J HF ) 35.9
Hz, 1H), 2.47 (dt, J ) 7.7 Hz, J HF ) 15.5 Hz, 2H), 1.57-1.39
(m, 3H), 0.86 (d, J ) 6.1 Hz, 6H); FAB MS m/z 319 [(M - Cl)+].
Anal. Calcd for C13H17ClFI•1/4H2O: C, 43.48; H, 4.91.
Found: C, 43.51; H, 4.62.
This (â-fluorovinyl)iodonium chloride (22 mg, 0.062 mmol)
was dissolved in dichloromethane (15 mL), and the solution
was vigorously shaken with a saturated aqueous sodium
tetrafluoroborate solution (5 mL) four times. The organic layer
was filtered and concentrated under aspirator vacuum to give
an oil, which was washed several times with hexane by
decantation at -78 °C to give the (â-fluorovinyl)iodonium
tetrafluoroborate 4c (25 mg, 99%) as an oil: IR (neat) 1646,
1472, 1446, 1050, 742 cm-1; 1H NMR (CDCl3) δ 8.02 (br d, J )
7.6 Hz, 2H), 7.65 (br t, J ) 7.3 Hz, 1H), 7.48 (br dd, J ) 7.6,
7.3 Hz, 2H), 6.48 (d, J HF ) 33.7 Hz, 1H), 2.59 (dt, J ) 7.5 Hz,
J HF ) 16.2 Hz, 2H), 1.70-1.36 (m, 3H), 0.88 (d, J ) 6.1 Hz,
6H); FAB MS m/z 319 [(M - BF4)+]; HRMS (FAB) calcd for
C13H17FI [(M - BF4)+] 319.0359, found 319.0356.
(Z)-1,2-Bis(ben zen esu lfon yl)-4-ph en yl-1-bu ten e (5d): col-
orless oil; IR (CHCl3) 1735, 1595, 1450, 1330, 1155, 1085 cm-1
;
1H NMR (CDCl3) δ 8.11 (br d, J ) 7.7 Hz, 2H), 7.88 (br d, J )
7.7 Hz, 2H), 7.70-7.50 (m, 6H), 7.25-7.15 (m, 3H), 7.01-6.92
(m, 2H), 6.48 (t, J ) 1.4 Hz, 1H), 2.84-2.62 (m, 4H); MS m/z
(relative intensity) 412 (0.1, M+), 271 (44), 129 (100), 91 (78),
77 (41); HRMS calcd for C22H20O4S2 (M+) 412.0803, found
412.0798. Anal. Calcd for C22H20O4S2: C, 64.05; H, 4.89.
Found: C, 64.36; H, 5.19.
(Z)-1,2-Bis(ben zen esu lfon yl)-5-p h en yl-1-p en ten e (5e):
colorless needles; mp 93-94 °C (recrystallized from dichlo-
romethane-hexane); IR (CHCl3) 2930, 1720, 1585, 1450, 1325,
1155, 1090 cm-1; 1H NMR (CDCl3) δ 8.10-8.00 (m, 4H), 7.75-
7.51 (m, 6H), 7.30-7.15 (m, 3H), 7.10-7.00 (m, 2H), 6.73 (t,
J ) 1.2 Hz, 1H), 2.56 (t, J ) 7.6 Hz, 2H), 2.42 (dt, J ) 1.2, 7.6
Hz, 2H), 1.75 (quint, J ) 7.6 Hz, 2H); MS m/z (relative
intensity) 426 (0.7, M+), 285 (80), 181 (30), 142 (99), 128 (58),
91 (100), 77 (78); HRMS calcd for C23H22O4S2 (M+) 426.0960,
found 426.0953. Anal. Calcd for C23H22O4S2: C, 64.76; H,
5.20. Found: C, 64.37; H, 5.22.
Gen er a l P r oced u r e for Rea ction of (Z)-(â-Ha loa lk -
en yl)iod on iu m Tet r a flu or ob or a t es 2-4 w it h Sod iu m
Ben zen esu lfin a te. To a stirred solution of a (Z)-(â-halovinyl)-
iodonium salt 2, 3, or 4 (0.05 mmol) in THF (1 mL) was added
sodium benzenesulfinate dihydrate (25 mg, 0.13 mmol) under
atmosphere at 0 °C, and the mixture was stirred for the periods
shown in Table 2. Water was added, the mixture was
extracted with dichloromethane three times, and the combined

8008 J . Org. Chem., Vol. 62, No. 23, 1997
Shiro and Ochiai
(Z)-1,2-Bis(b en zen esu lfon yl)-5-ch lor o-1-p en t en e (5f):
colorless oil; IR (CHCl3) 1450, 1325, 1150, 1085 cm-1; 1H NMR
(CDCl3) δ 8.16-8.00 (m, 4H), 7.71-7.51 (m, 6H), 6.84 (t, J )
1.2 Hz, 1H), 3.48 (t, J ) 6.1 Hz, 2H), 2.56 (br dt, J ) 1.2, 7.3
Hz, 2H), 2.04-1.89 (m, 2H); MS m/z (relative intensity) 384
(0.4, M+), 243 (11), 183 (24), 149 (53), 125 (93), 77 (100); HRMS
calcd for C17H17O4ClS2 (M+) 384.0257, found 384.0232.
(Z)-1,2-B is (b e n ze n e s u lfo n y l)-3-c y c lo p e n t y l-1-p r o -
p en e (5g):7b colorless oil; IR (CHCl3) 2950, 1450, 1325, 1150,
2.54 (dt, J ) 1.2, 7.5 Hz, 2H), 1.70-1.50 (m, 2H), 1.43-1.18
(m, 10H), 0.88 (t, J ) 6.8 Hz, 3H);, 2.54 (dt, J ) 1.2, 7.3 Hz,
2H), 1.66-1.46 (m, 2H), 1.36-1.14 (m, 10H), 0.88 (t, J ) 6.8
Hz, 3H); MS (CI, isobutane) m/z (relative intensity) 629 (20),
317 (45), 315 (100, M+ + 1); HRMS calcd for C16H24ClO2S (M+
+ 1) 315.1186, found 315.1200.
Rea ction In ter m ed ia te (Z)-[2-(Ben zen esu lfon yl)-1-d e-
cen yl]p h en yliod on iu m Tetr a flu or obor a te (Z)-(9b). To
a stirred solution of (Z)-(â-chlorovinyl)iodonium salt 2b (80 mg,
0.17 mmol) in THF (3 mL) was added sodium benzenesulfinate
dihydrate (35 mg, 0.17 mmol) under atmosphere at 0 °C, and
the mixture was stirred for 12 h. The mixture was vigorously
shaken with a saturated aqueous sodium tetrafluoroborate
solution (10 mL) four times. The organic layer was filtered
and concentrated under aspirator vacuum to give an oil, which
was analyzed by 1H NMR and the results are shown in Scheme
3. Decantation using hexane at -78 °C several times followed
by repeated fractional recrystallization using dichloromethane-
hexane-diethyl ether gave pure (Z)-(2-sulfonyldecenyl)iodo-
nium salt (Z)-9b (X ) BF4) (1.2 mg) as colorless plates (mp
118-121 °C). The structure of this iodonium salt was deter-
mined by comparison of its spectral data (1H NMR, IR, and
FAB MS) with those of the authentic samples.3d
Tim e Cou r se for th e Rea ction of (Z)-(â-Br om od ece-
n yl)iod on iu m Sa lt 3b w ith Sod iu m Ben zen esu lfin a te. To
a solution of (Z)-(â-bromodecenyl)iodonium salt 3b (11 mg,
0.022 mmol) in CDCl3 (0.5 mL) in an NMR tube was added
sodium benzenesulfinate dihydrate (11 mg, 0.054 mmol) at
room temperature. 1H NMR monitoring of the reaction
mixture was performed over 84 h and the results are shown
in Figure 2 (b). Quenching of the reaction mixture with water
followed by standard workup gave (Z)-5b (3.3 mg, 43%) and
(Z)-2-(benzenesulfonyl)-1-bromo-1-decene (7b) (3 mg, 33%).
Gen er a l P r oced u r e for Com p etitive Rea ction of (Z)-
9b (X ) BF 4) w ith Ha lid e a n d Ben zen esu lfin a te An ion s.
To a stirred solution of two competing tetrabutylammonium
salts (each 0.70 mmol) in THF (10 mL) and dichloromethane
(1 mL) was added (Z)-(2-sulfonyldecenyl)iodonium salt (Z)-9b
(X ) BF4) (20 mg, 0.035 mmol) under atmosphere at 0 °C, and
the mixture was stirred for the periods shown in Table 3.
Water was added, the mixture was extracted with diethyl ether
three times, and the combined organic phase was washed with
water and brine. The solution was dried over anhydrous Na2-
SO4 and concentrated to give an oil, which was purified by
preparative TLC (hexane-ethyl acetate). The yields of pure
products are given in Table 3, entries 1-3.
1085 cm-1 1H NMR (CDCl3) δ 8.09 (br d, J ) 7.5 Hz, 2H),
;
8.03 (br d, J ) 7.5 Hz, 2H), 7.71-7.64 (m, 2H), 7.63-7.54 (m,
4H), 6.81 (t, J ) 1.3 Hz, 1H), 2.41 (dd, J ) 7.5, 1.3 Hz, 2H),
2.01 (septet, J ) 7.5 Hz, 1H), 1.73-1.64 (m, 2H), 1.60-1.42
(m, 4H), 1.03-0.93 (m, 2H); MS m/z (relative intensity) 390
(0.1, M+), 249 (37), 218 (32), 143 (33), 125 (88), 107 (61), 77
(100); HRMS calcd for C20H22O4S2 (M+) 390.0960, found
390.0976. Anal. Calcd for C20H22O4S2: C, 61.51; H, 5.68.
Found: C, 61.28; H, 5.71.
(Z)-1,2-Bis(b e n ze n e su lfon yl)-3,3-d im e t h yl-1-b u t e n e
(5h ):7b colorless needles; mp 138-139 °C (recrystallized from
dichloromethane-hexane); IR (CHCl3) 2945, 1580, 1445, 1320,
1
1150, 1080 cm-1; H NMR (CDCl3) δ 8.16 (br d, J ) 8.0 Hz,
2H), 7.97 (br d, J ) 8.0 Hz, 2H), 7.71-7.49 (m, 6H), 7.11 (s,
1H), 1.26 (s, 9H). Anal. Calcd for C18H20O4S2: C, 59.32; H,
5.53. Found: C, 59.13; H, 5.53.
(Z)-2-(Ben zen esu lfon yl)-1-br om o-1-d ecen e (7b):7a color-
less oil; IR (CHCl3) 2920, 2845, 1715, 1580, 1445, 1315, 1150,
1085 cm-1 1H NMR (CDCl3) δ 8.00 (br d, J ) 7.3 Hz, 2H),
;
7.65 (br t, J ) 6.8 Hz, 1H), 7.55 (br dd, J ) 7.3, 6.8 Hz, 2H),
6.79 (t, J ) 1.2 Hz, 1H), 2.54 (dt, J ) 1.2, 7.3 Hz, 2H), 1.66-
1.46 (m, 2H), 1.36-1.14 (m, 10H), 0.88 (t, J ) 6.8 Hz, 3H);
MS (CI, isobutane) m/z (relative intensity) 361 (100), 359 (97,
M+ + 1), 317 (10); HRMS calcd for C16H24BrO2S (M+ + 1)
359.0680, found 359.0663. Anal. Calcd for C16H23BrO2S: C,
53.48; H, 6.45. Found: C, 52.98; H, 6.40.
(Z)-2-(Ben zen esu lfon yl)-5-m et h yl-1-b r om o-1-h exen e
(7c): colorless oil; IR (CHCl3) 2945, 1585, 1440, 1315, 1150,
1085 cm-1 1H NMR (CDCl3) δ 8.00 (br d, J ) 7.7 Hz, 2H),
;
7.68-7.50 (m, 3H), 6.80 (t, J ) 1.3 Hz, 1H), 2.55 (br dt, J )
1.3, 7.6 Hz, 2H), 1.62-1.41 (m, 3H), 0.91 (d, J ) 6.3 Hz, 6H);
MS m/z (relative intensity) 318 (0.3), 316 (0.3, M+), 303 (2),
301 (2), 237 (98), 143 (100), 125 (57), 95 (72), 77 (62); HRMS
calcd for C13H17BrO2S (M+) 316.0133, found 316.0115.
(Z)-1-(Ben zen esu lfon yl)-2-ch lor o-3,3-d im et h yl-1-b u -
ten e (8): colorless plates; mp 67-68 °C (recrystallized from
dichloromethane-hexane); IR (CHCl3) 2970, 1595, 1320, 1200,
1
1150, 1090 cm-1; H NMR (CDCl3) δ 7.98 (br d, J ) 7.3 Hz,
In a similar manner, competitive reactions of (Z)-9b (X )
BF4) with sodium salts were carried out in THF under
atmosphere at 0 °C. The yields of pure products are given in
Table 3, entries 4-6.
2H), 7.64 (br t, J ) 7.3 Hz, 1H), 7.55 (br t, J ) 7.3 Hz, 2H),
6.69 (s, 1H), 1.19 (s, 9H); MS m/z (relative intensity) 258 (9,
M+), 223 (100), 125 (84), 117 (88), 81 (50), 77 (81); HRMS calcd
for C12H15ClO2S (M+) 258.0481, found 258.0466. Anal. Calcd
for C12H15ClO2S: C, 55.70; H, 5.84. Found: C, 55.95; H, 6.01.
The structure and stereochemistry of 8 were deduced by the
observed NOE enhancements between the vinylic proton and
both the ortho protons and the methyl groups. Synthesis of
the regioisomer, (Z)-2-(benzenesulfonyl)-1-chloro-3,3-dimethyl-
1-butene, has been reported.7a
Tim e Cou r se for th e Rea ction of (Z)-(â-F lu or od ece-
n yl)iod on iu m Sa lt 4b w ith Sod iu m Ben zen esu lfin a te. To
a solution of (Z)-(â-fluorodecenyl)iodonium salt 4b (13 mg,
0.029 mmol) in CDCl3 (0.5 mL) in an NMR tube was added
sodium benzenesulfinate dihydrate (14 mg, 0.071 mmol) at
room temperature. 1H NMR monitoring of the reaction
mixture was performed over 154 h, and the results are shown
in Figure 2 c. Quenching of the reaction mixture with water
followed by standard workup gave (Z)-5b (2.2 mg, 18%), (E)-
5b (3.6 mg, 30%), and 1-(benzenesulfonyl)cyclopentene 113d
(1.8 mg, 23%).
Tim e Cou r se for th e Rea ction of (Z)-(â-Ch lor od ece-
n yl)iod on iu m Sa lt 2b w ith Sod iu m Ben zen esu lfin a te. To
a solution of (Z)-(â-chlorodecenyl)iodonium salt 2b (10 mg,
0.022 mmol) in CDCl3 (0.5 mL) in an NMR tube was added
sodium benzenesulfinate dihydrate (11 mg, 0.054 mmol) at
room temperature. 1H NMR monitoring of the reaction
mixture was performed over 9 h, and the results are shown in
Figure 2 (a). Quenching of the reaction mixture with water
followed by standard workup gave (Z)-1,2-bis(benzenesulfonyl)-
1-decene (5b) (8.2 mg, 91%) and (Z)-2-(benzenesulfonyl)-1-
chloro-1-decene (6b) (0.2 mg, 3%). 6b:7a colorless oil; IR
Su p p or tin g In for m a tion Ava ila ble: ORTEP drawing of
1
(E)-5b; H NMR spectra for (Z)-5f, 6b, and 7c; NOE data of
2b, 2g, 3b, and 4b (5 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
(CHCl3) 2915, 1590, 1445, 1315, 1155, 1085 cm-1 1H NMR
;
(CDCl3) δ 7.98 (br d, J ) 7.8 Hz, 2H), 7.65 (br t, J ) 7.5 Hz,
1H), 7.55 (br dd, J ) 7.8, 7.5 Hz, 2H), 6.52 (t, J ) 1.2 Hz, 1H),
J O970735V