Novel Homologation Reaction of Arylzincates Bearing a Leaving Group at the Ortho and Meta Positions

Article abstract of DOI:10.1021/jo990937m

Arylzincates bearing a leaving group at the ortho, meta, and para positions were generated by iodine/zinc exchange reaction of the corresponding iodoaryl sulfonates with Bu₃ZnLi, and their reactivity was investigated via product analysis after hydrolysis and treatment with iodine. Zincates derived from o-iodophenyl triflates and tosylate underwent homologation reaction to give o-butylphenylzinc species. o-Benzyne as an intermediate of the reaction was demonstrated by the lack of regioselectivity for trisubstituted zincates. Zincates derived from m-iodophenyl triflates also underwent homologation leading to m-butylphenylzinc species. Similar product ratios observed in the reactions of regioisomeric trisubstituted iodophenyl triflates as well as the formation of radical reaction byproducts suggested the involvement of m-benzyne intermediate. p-(Trifluoromethane-sulfonyloxy)phenylzincate was thermally stable at room temperature; generation of p-benzyne was not observed.

Full text of DOI:10.1021/jo990937m

8210
J . Org. Chem. 1999, 64, 8210-8213
Novel Hom ologa tion Rea ction of Ar ylzin ca tes Bea r in g a Lea vin g
Gr ou p a t th e Or th o a n d Meta P osition s
Toshiro Harada,* Minako Chiba, and Akira Oku
Department of Chemistry, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, J apan
Received J une 9, 1999
Arylzincates bearing a leaving group at the ortho, meta, and para positions were generated by
iodine/zinc exchange reaction of the corresponding iodoaryl sulfonates with Bu3ZnLi, and their
reactivity was investigated via product analysis after hydrolysis and treatment with iodine. Zincates
derived from o-iodophenyl triflates and tosylate underwent homologation reaction to give o-
butylphenylzinc species. o-Benzyne as an intermediate of the reaction was demonstrated by the
lack of regioselectivity for trisubstituted zincates. Zincates derived from m-iodophenyl triflates also
underwent homologation leading to m-butylphenylzinc species. Similar product ratios observed in
the reactions of regioisomeric trisubstituted iodophenyl triflates as well as the formation of radical
reaction byproducts suggested the involvement of m-benzyne intermediate. p-(Trifluoromethane-
sulfonyloxy)phenylzincate was thermally stable at room temperature; generation of p-benzyne was
not observed.
Homologation of organometallics is becoming of in-
a leaving group directly at the benzene ring (eq 4).
Phenylzincates 5 (R ) Bu) were generated from the
corresponding iodoarenes by iodine/zinc exchange4,2 with
Bu3ZnLi, and their reactions were studied on the basis
of product analysis after hydrolysis and treatment with
iodine. We wish to report herein the results of the study
that revealed that arylzincates bearing a leaving group
at the ortho and meta position undergo a novel homolo-
gation reaction not through a pathway involving 1,2-
migration.
creasing importance in organic synthesis because sub-
sequent bond formation of the resulting organometallics
leads to the convergent construction of complex carbon
frameworks by a one-pot procedure.1 Recent reports from
this laboratory revealed that organozincates 1 and 2
bearing leaving groups at the R- and γ-position, respec-
tively, undergo 1,2-migration at low temperatures to give
the corresponding homologated organozinc reagents (eqs
1 and 2).2 More recently, we have shown that facile 1,2-
Resu lts a n d Discu ssion
2-Iodophenyl triflate (6) was treated with Bu3ZnLi (2.0
equiv) in THF at -85 °C for 0.5 h. Hydrolysis of the
resulting mixture with aqueous HCl-THF gave butyl-
benzene (8) in 62% yield5 (eq 5). On the other hand,
iodination product 9 was obtained in 68% yield by
treatment of the same reaction mixture with I2, demon-
strating the generation of 2-butylphenylzinc species 7.
migration is also observed for arylzincates 3, bearing a
leaving group at the benzylic position, despite the initial
formation of dearomatized organozinc species 4 (eq 3).3
To clarify the scope of 1,2-migration of organozincates,
we investigated the reactivity of phenylzincates 5 bearing
(1) (a) Knochel, P. InComprehensive Organic Synthesis; Trost, B.
M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 4, p 865.
(b) Suzuki, M.; Yanagisawa, A.; Noyori, R. J . Am. Chem. Soc. 1988,
110, 4718. (c) Lipshutz, B. H.; Wood, M. R. J . Am. Chem. Soc. 1994,
116, 11689. (d) Marek, I.; Normant, J .-F. Chem. Rev. 1996, 96, 3241.
(2) (a) Harada, T.; Hara, D.; Hattori, K.; Oku, A. Tetrahedron Lett.
1988, 29, 3821-3824. (b) Harada, T.; Katsuhira, T.; Osada, A.; Iwazaki,
K.; Maejima, R.; Oku, A. J . Am. Chem. Soc. 1996, 118, 11377 and
references therein. (c) Harada, T.; Oku, A. In Organozinc Reagents. A
Practical Approach; Knochel, P., J ones, P., Eds.; Oxford University
Press: Oxford, 1999; p 101.
(3) (a) Harada, T.; Kaneko, T.; Fujiwara, T.; Oku, A. J . Org. Chem.
1997, 62, 8966. (b) Harada, T.; Kaneko, T.; Fujiwara, T.; Oku, A.
Tetrahedron 1998, 54, 9317.
Under similar conditions at -85 °C, 4-methyl-2-iodo-
phenyl triflate (10a ) gave a mixture of the butylation
10.1021/jo990937m CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/14/1999

Homologation Reaction of Arylzincates
J . Org. Chem., Vol. 64, No. 22, 1999 8211
Ta ble 1. Rea ction of Iod op h en yl Su lfon a tes 10a ,b w ith
Bu 3Zn Lia
Ta ble 2. Rea ction of 3-Iod op h en yl Tr ifla te (17) w ith
Bu 3Zn Lia
sub- electro-
entry strate phile
yield
products ratiob (%)
entry Bu3ZnLi (equiv) concn (M)b time (h) GC yield (%) of 8
conditions
1
2
1.2
2.0
2.0
2.0
3.0
2.0
3.0
0.3
0.3
0.3
0.3
0.3
0.6
0.6
5
1
7
2
2
1
1
24
47
39
35
53
53
60
1
2
3
4
5
10a
10b
10b
10a
10b
aq HCl -85 °C, 0.5 h 11a , 11b 1.1:1
aq HCl -85 °C, 0.5 h 13
65
87
63
55
66
3c
4d
5
aq HCl 0 °C, 1 h
11a , 11b 1.1:1
-85 °C, 0.5 h 12a , 12b 1.3:1
0 °C, 1 h 12a , 12b 1.3:1
I2
I2
6
7
a
All reactions were carried out by adding substrate to a THF
b
a
solution of Bu3ZnLi (2.0 equiv) at -85 °C. Determined by GC
analysis.
Unless otherwise noted, reactions were carried out at room
temperature in THF. Concentration of Bu3ZnLi. c The reaction
was performed at 0 °C. Et2O was used as a solvent.
b
d
Sch em e 1
ature above 0 °C, a zincate derived from 17 was unstable
undergoing novel butylation reaction (eq 7, Table 2).
products 11a and 11b nonselectively (eq 6, entry 1 in
Table 1). Arylzincate derived from tosylate 10b was less
reactive at -85 °C and afforded 4-methylphenyl tosylate
(13) (entry 2). At 0 °C, nonselective formation of 11a and
Thus, hydrolysis of the reaction mixture of 17 and
Bu3ZnLi (2.0 equiv) after being stirred for 1 h at room
temperature afforded butylbenzene (8) in 47% yield
(entry 2). Lower reaction temperature or Et2O as a
solvent did not give better results (entries 3 and 4). The
yield of 8 was improved by the use of the excess zincate
(entry 5 vs entries 1 and 2) and by carrying out the
reaction at higher concentration (entries 6 and 7). The
reaction of 17 with 3.0 equiv of the zincate at 0.6 M in
THF gave 8 in 60% yield (entry 7). It should be noted
that the reaction of 17 with butyllithium gave a complex
mixture even at -85 °C. The formation of 3-butylphe-
nylzinc species 19 was verified by the formation of
iodoarene 20 (56%) in the I2 trapping experiment (eq 7).
In this reaction, m-diiodobenzene (21) (15%) and tetrahy-
drofuran derivative 22 (6%) were also obtained as
byproducts.
11b (1.1:1, 63%) was observed also from 10b (entry 3).
Generation of the corresponding arylzinc species 16a ,b
(Scheme 1) was verified by the formation of iodoarenes
12a and 12b in I2 trapping experiments (entries 4 and
5). Arylzincate 14, produced by iodine/zinc exchange
reaction, would undergo 1,2-migration to give 16a . The
lack of regioselectivity observed indicates that such
concerted pathway is energetically less favorable than a
stepwise pathways involving o-benzyne6-7 as an inter-
mediate. Thus, arylzincate 14 undergoes â elimination
to generate o-benzyne 15. Subsequent nonselective car-
bometalation by Bu2Zn and/or Bu3ZnLi gives a mixture
of 16a and 16b.
In comparison with arylzincates derived from o-iodo-
phenyl triflates, those derived from m- and p-iodophenyl
triflates were found to be considerably more stable. Thus,
treatment of 3- and 4-iodophenyl triflate 17 and 18 with
Bu3ZnLi (2.0 equiv) in THF at -85 °C for 0.5 h and
hydrolysis of the resulting mixture gave phenyl triflate
in 95% and 93% yield, respectively. An arylzincate
To clarify the regiochemistry of butylation, the reaction
of isomeric iodo(methoxy)phenyl triflates 24a and 24b
were examined (eqs 8 and 9). The reaction of 24a with
Bu3ZnLi (3 equiv, 0.6 M) at room temperature for 8 h
gave p-isomer 25a as a major butylation product together
with a minor formation of o-isomer 25b (25a :25b ) 6.6:
1, 17% combined yield). The butylation reaction was
relatively slow and triflate 26a was also obtained in 24%.
Under similar conditions, 24b also afforded a mixture of
25a and 25b (8.1:1) in 13% combined yield as well as
triflate 26b (40% yield).
derived from 18 was stable even at room temperature,
affording phenyl triflate (85%) in the reaction at room
temperature for 20 h. On the other hand, at the temper-
It is difficult to rationalize similar product ratios
(25a :25b) observed for the reactions of isomeric triflates
24a and 24b by a direct alkylation pathway from the
corresponding arylzincate intermediates 27a ,b . The
(4) (a) Harada, T.; Katsuhira, T.; Hattori, K.; Oku, A. Tetrahedron
1994, 50, 7987. (b) Kondo, Y.; Takezawa, N.; Yamazaki, C.; Sakamoto,
T. J . Org. Chem. 1995, 59, 4717.
(5) The yield was determined by GC.

8212 J . Org. Chem., Vol. 64, No. 22, 1999
Harada et al.
Sch em e 2
prepared by iodine/zinc exchange reaction of the corre-
sponding iodoaryl sulfonates with Bu3ZnLi. Zincates
derived from o- and m-iodoaryl sulfonates were found to
undergo homologation to give the corresponding bu-
tylphenylzinc species while a zincate derived from a para
derivative was stable. The lack in regioselectivity ob-
served for trisubstituted zincates demonstrated that
o-benzyne is an intermediate for the reaction of o-iodo
derivatives. Based on a similar product rations in the
reactions of regioisomeric trisubstituted zincates as well
as the formation of radical reaction byproducts, we
proposed a pathway involving m-benzyne as an interme-
diate for the reaction of m-iodo derivatives.
result rather implies a stepwise pathway, which may
involve a common intermediate derived from 27a and
27b. m-Benzyne9 is a σ,σ-biradical intermediate possess-
ing a singlet ground state with a singlet-triplet gap of
21 kcal/mol,10 whose chemistry has been less studied than
that of o- and p-benzynes.11 Recent gas-phase study using
Fourier transform ion cyclotron resonance mass spec-
trometry showed that m-benzyne undergoes both addi-
tion reactions, characteristic of o-benzyne, and radical
reactions, characteristic of p-benzyne.12 One possible
explanation for the result of the reaction of 24a ,b could
be the involvement of m-benzyne as an intermediate
(Scheme 2). Thus, both zincates 27a and 27b would
undergo elimination to give m-benzyne 28, which may
undergo regioselective carbometalation by Bu2Zn and/or
Bu3ZnLi to form p-butylphenylzinc 29a preferentially
over o-butyl isomer 29b probably due to the steric reason.
Diiodobenzene 21 and tetrahydrofuran derivative 22
were produced as byproducts in the reaction of parent
3-iodophenyl triflate (17) followed by I2 trap. The forma-
tion of 21 implies the generation of dimetal species 23.
The radical-type reactivity of m-benzyne12 may allow
iodine abstraction from iodobutane, which was produced
in the initial iodine/zinc exchange of Bu3ZnLi. Dimeta-
lation of the resulting diiodobenzene by Bu3ZnLi may
lead to generation of 23. Formation of 22 can be rational-
ized by the reaction of 23 with 2-iodotetrahydrofuran,
which might be formed through a pathway involving
hydrogen abstraction of tetrahydrofuran by m-benzyne
and iodine abstraction of the resulting radical from
iodobutane.
Exp er im en ta l Section
NMR spectra were recorded in CDCl3. All commercially
available reagents were used without further purification
unless otherwise noted. THF was distilled from sodium ben-
zophenone ketyl. Commercial anhydrous ZnCl2 was dried in
vacuo at 100 °C for 10 h over P2O5. All reactions were
performed under argon. Reactions at -85 °C were performed
with a Neslab Cryo Cool immersion cooler. Organic extracts
were dried over Na2SO4. Flash chromatography was conducted
on silica gel (Wakogel C-300).
2-Iodo-4-methylphenol14 and 5-iodo-2-methoxyphenol15 were
prepared according to the literature procedures. The following
aryl triflates were prepared from the corresponding phenols
by the standard procedure.16
2-Iod op h en yl tr iflu or om eta n esu lfon a te (6): 85% yield;
1H NMR (300 MHz) δ 7.10 (1H, dt, J ) 1.5, 7.8 Hz), 7.32 (1H,
dd, J ) 1.2, 8.1 Hz), 7.42 (1H, dt, J ) 1.5, 8.1 Hz), 7.91 (1H,
dd, J ) 1.5, 8.1 Hz); 13C NMR (125.8 MHz) δ 89.05, 118.69 (q,
J ) 321 Hz), 122.04, 129.60, 130.05, 140.77, 150.22; IR (liquid
film) 1425, 1215, 890, 765 cm-1. Anal. Calcd for C7H4O3F3SI:
C, 23.88; H, 1.15. Found: C, 23.57; H, 1.15.
Con clu sion
We have described the results of the study on the
reactivity of arylzincates bearing a leaving group at the
ortho, meta, and para position. The arylzincates were
2-Iodo-4-m eth ylph en yl tr iflu or om etan esu lfon ate (10b):
1
75% yield; H NMR (500 MHz) δ 2.37 (s, 3H), 7.21 (2H, m),
7.74 (1H, br s); 13C NMR (125.8 MHz) δ 20.39, 88.78, 118.70
(q, J ) 321 Hz), 121.50, 130.61, 140.07, 140.96, 141.89, 148.18;
IR (liquid film) 1440, 1225, 900 cm-1. Anal. Calcd for C8H6O3F3-
SI: C, 26.25; H, 1.65. Found: C, 25.94; H, 1.59.
(6) Hoffmann, R. W. Dehydrobenzene and Cycloalkynes; Academic
Press: New York, 1967.
3-Iod op h en yl tr iflu or om eta n esu lfon a te (17): 90% yield;
1H NMR (300 MHz) δ 7.19 (1H, t, J ) 8.4 Hz), 7.27 (1H, br d,
J ) ca. 8.5 Hz), 7.63 (1H, t, J ) 2.1 Hz), 7.74 (1H, br d, J )
ca. 8 Hz); 13C NMR (125.8 MHz) δ 93.83, 115.00, 118.65 (q, J
) 321 Hz), 120.82, 122.00, 130.42, 131.45, 137.66, 149.20; IR
(liquid film) 1430, 1215, 995, 795 cm-1. Anal. Calcd for
C7H4O3F3SI: C, 23.88; H, 1.15. Found: C, 23.61; H, 1.17.
(7) For a review of nucleophilic addition to arynes, see: Compre-
hensive Organic Chemistry; Kessar, S. V., Ed.; Pergamon: Oxford,
U.K., 1991; Vol. 4, p 483.
(8) Generation of o-benzynes by the reaction of o-iodoaryl triflate
has been reported. (a) Matsumoto, T.; Hosoya, T.; Katsuki, M.; Suzuki,
K. Tetrahedron Lett. 1991, 32, 6735. (b) Matsumoto, T.; Sohma, T.;
Yamaguchi, H.; Suzuki, K. Chem. Lett. 1995, 677.
(9) (a) Squires, R. R. J . Am. Chem. Soc. 1996, 118, 5816. (b)
Wenthold, P. G.; Squires, R. R.; Lineberger, W. C. J . Am. Chem. Soc.
1998, 120, 5279 and references therein.
(10) Marquardt, R.; Sander, W.; Kraka, E. Angew. Chem., Int. Ed.
Engl. 1996, 35, 746.
(11) (a) J ones, R. R.; Bergman, R. G. J . Am. Chem. Soc. 1972, 94,
660. (b) Bergman, R. G. Acc. Chem. Res. 1973, 6, 25. (c) Nicolau, K.
C.; Dai, W.-M. Angew. Chem., Int. Ed. Engl. 1991, 30, 1387.
(12) Thoen, K. K.; Kentta¨maa, H. I. J . Am. Chem. Soc. 1999, 121,
800.
(13) (a) Washburn, W. N.; Zahler, R.; Chen, I. J . Am. Chem. Soc.
1978, 100, 5863. (b) Billups, W. E.; Buynak, J . D.; Bulter, D. J . Org.
Chem. 1979, 44, 4218.
(14) Kometani, T.; Watt, D. S.; J i, T. Tetrahedron Lett. 1985, 26,
2043.
(15) Feldman, K. S. J . Org. Chem. 1997, 62, 4983.
(16) Echavarren, A.; Stille, J . K. J . Am. Chem. Soc. 1987, 109, 5478.

Homologation Reaction of Arylzincates
J . Org. Chem., Vol. 64, No. 22, 1999 8213
4-Iod op h en yl tr iflu or om eta n esu lfon a te (18): 67% yield;
1H NMR (500 MHz) δ 7.06 and 7.81 (4H, AA′BB′, J ) ca. 9
Hz); 13C NMR (125.8 MHz) δ 93.15, 118.66 (q, J ) 321 Hz),
123.30, 139.39, 149.37; IR (liquid film) 1435, 1220, 890, 830,
750 cm-1. Anal. Calcd for C7H4O3F3SI: C, 23.88; H, 1.15.
Found: C, 23.61; H, 1.14.
stirred for 15 min, the mixture was poured into 1 N aqueous
HCl and extracted twice with hexane. The organic layers were
washed successively with aqueous Na2S2O3 and aqeous NaH-
CO3, dried, and concentrated in vacuo. Kugelrohr distillation
(60-150 °C/0.5 mmHg) of the residue gave 0.185 g (68%) of
2-butyliodobenzene (9).22
2-Bu t yl-4-m et h yliod ob en zen e (12a ) a n d 2-b u t yl-5-
m eth yliod oben zen e (12b): obtained as a mixture (12a :12b
) 1.3:1) by Kugelrohr distillation (70-100 °C/0.3 mmHg); 1H
NMR (300 MHz) δ 0.95 (3H for 12b, d, J ) 7.2 Hz), 0.96 (3H
for 12a , d, J ) 7.2 Hz), 1.4 (2H, m), 1.55 (2H, m), 2.26 (3H for
12b, s), 2.27 (3H for 12a , s), 2.66 (2H, t), 6.77 (1H for 12a , dd,
J ) 2.4, 7.2 Hz), 7.02 (1H for 12a , d, J ) 2.4 Hz), 7.07 (2H for
12b, br s), 7.64 (1H for 12b, br s), 7.66 (1H for 12a , d, J ) 7.2
Hz); 13C NMR (125.8 MHz) δ 13.97 (for 12a ,b), 20.25 (for 12a ),
20.89 (for 12b), 22.40 (for 12b), 22.49 (for 12a ), 32.52 (for
12a ,b), 39.98 (for 12a ), 40.41 (for 12b), 96.47 (for 12b), 100.49
(for 12a ), 128.49 (for 12b), 128.89 (for 12a ), 129.02 (for 12b),
130.25 (for 12a ), 137.28 (for 12a ), 138.09 (for 12b), 139.07 (for
12a ), 139.76 (for 12b), 142.23 (for 12b), 145.06 (for 12a ). Anal.
Calcd for C11H15I: C, 48.19; H, 5.51. Found: C, 47.88; H, 5.23.
Rea ction of Tr ifla te 17 w ith Bu 3Zn Li: I2 Tr a p (Eq 7).
Triflate 17 (1.06 g, 3.01 mmol) was treated with Bu3ZnLi (6.0
mmol) in THF (21 mL) at -85 °C for 30 min by a procedure
similar to that described above. The mixture was allowed to
warm to room temperature during 0.5 h and stirred further
for 1 h at room temperature. To the resulting mixture at -85
°C was added a THF (9 mL) solution of iodine (4.6 g, 18 mmol).
After being stirred for 15 min, the mixture was poured into 1
N aqueous HCl and extracted twice with hexane. The organic
layers were washed successively with aqueous Na2S2O3 and
aqueous NaHCO3, dried, and concentrated in vacuo. Purifica-
tion of the residue by flash chromatography (0.5-15% ethyl
acetate/hexane) gave, in order of elution, a 3.8:1 mixture of
20 (56%) and 2123 (15%) (0.587 g) and 22 (48.4 mg, 6%).
Separation of the mixture by a recycling preparative HPLC,
equipped with a GPC column (J AIGEL-1H column, J apan
Analytical Industry) using CHCl3 as an eluent, afforded pure
20. 3-Butyl-1-iodobenzene (20): 1H NMR (300 MHz) δ 0.93
(3H, t, J ) 7.2 Hz), 1.34 (2H, m), 1.58 (2H, m), 2.55 (2H, t, J
) 7.8 Hz), 7.00 (1H, t, J ) 7.8 Hz), 7.14 (1H, br d, J ) ca. 8
Hz), 7.51 (1H, br d, J ) ca. 8 Hz), 7.55 (1H, br s); 13C NMR
(125.8 MHz) δ 13.89, 22.25, 33.38, 35.19, 94.40, 127.66, 129.93,
134.61, 137.39, 145.30; IR (liquid film) 790, 695 cm-1. Anal.
Calcd for C10H13I: C, 46.18; H, 5.04. Found: C, 45.99; H, 4.91.
(3-Iodophenyl)tetrahydrofuran (22): 1H NMR (300 MHz) δ 1.77
(1H, m), 1.99 (2H, m), 2.32 (1H, m), 3.93 (1H, m), 4.08 (1H,
m), 4.83 (1H, t, J ) 7.2 Hz), 7.05 (1H, t, J ) 7.8 Hz), 7.25 (1H,
br d, J ) ca. 8 Hz), 7.58 (1H, br d, J ) ca. 8 Hz), 7.68 (1H, br
s); 13C NMR (125.8 MHz) δ 25.91, 34.63, 68.78, 79.75, 94.39,
124.85, 130.03, 134.55, 136.10, 145.99; IR (liquid film) 1070,
785, 735, 695 cm-1. Anal. Calcd for C10H11OI: C, 43.82; H, 4.04.
Found: C, 43.78; H, 4.01.
5-Iod o-2-m et h oxyp h en yl t r iflu or om et a n esu lfon a t e
(24b): 90% yield; 1H NMR (300 MHz) δ 3.90 (3H, s), 6.80 (1H,
d, J ) 8.7 Hz), 7.49 (1H, d, J ) 2.1 Hz), 7.62 (1H, dd, J ) 2.1,
8.7 Hz); 13C NMR (125.8 MHz) δ 55.27, 80.72, 118.63 (q, J )
320 Hz), 131.06, 138.09, 138.75, 151.51; IR (liquid film) 1425,
1220, 905, 810 cm-1. Anal. Calcd for C8H6O4F3SI: C, 25.15;
H, 1.58. Found: C, 25.00; H, 1.64.
2-Iod o-4-m eth ylp h en yl p-Tolu en esu lfon a te (10a ). The
tosylate was prepared in 85% yield by the reaction of the
corresponding phenol with p-toluenesulfonyl chloride under
the Schotten-Baumann conditions in benzene-aqueous NaOH.
10a : mp 104-105 °C (recrystallized from benzene and hexane);
1H NMR (500 MHz) δ 2.31 (3H, s), 2.48 (3H, 1), 7.14 (1H, br
d, J ) ca. 8.5 Hz), 7.20 (1H, d, J ) 8.4 Hz), 7.35 and 7.83 (4H,
AA′BB′, J ) ca. 8.5 Hz), 7.60 (1H, br s); 13C NMR (125.8 MHz)
δ 20.31, 21.72, 89.91, 122.43, 128.80, 129.72, 130.09, 132.76,
138.53, 140.24, 145.59, 147.78; IR (KBr disk) 1385, 1185, 840,
690 cm-1. Anal. Calcd for C14H13O4SI: C, 43.31; H, 3.38.
Found: C, 43.30; H, 3.34.
3-Iod o-4-m et h oxyp h en yl Tr iflu or om et a n esu lfon a t e
(24a ). A mixture of p-methoxyphenyl triflate16 (2.31 g, 9.00
mmol), iodine (1.83 g, 7.20 mmol), iodic acid (0.633 g, 3.6 mmol)
in H2SO4 (10.4 mL, CCl4 (1.8 mL), acetic acid (4.3 mL), and
H2O (2.2 mL) was heated under reflux for 2 days. The mixture
was poured into water and extracted twice with ether. The
organic layers were washed successively with water, aqueous
Na2S2O3, 10% aqueous NaOH, and brine, dried, and concen-
trated in vacuo. Purification of the residue by flash chroma-
tography gave 3.15 g (92%) of 24a : 1H NMR (300 MHz) δ 3.90
(3H, s), 6.82 (1H, d, J ) 9.0 Hz), 7.26 (1H, dd, J ) 3.0, 9.0
Hz), 7.68 (1H, d, J ) 3.0 Hz); 13C NMR (125.8 MHz) δ 55.79,
85.60, 110.62, 118.63 (q, J ) 321 Hz), 122.14, 132.01, 142.58,
157.99; IR (liquid film) 1420, 1220, 900, 820 cm-1. Anal. Calcd
for C8H6O4F3SI: C, 25.15; H, 1.58. Found: C, 25.05; H, 1.64.
Rep r esen ta tive P r oced u r e for th e Rea ction of Ar en e-
su lfon a tes w ith Bu 3Zn Li: Hyd r olysis of th e Rea ction
Mixtu r e (Ta ble 1, En tr y 1). To a solution of ZnCl2 (0.27 g,
2.0 mmol) in THF (6 mL) at 0 °C was added a solution of BuLi
(6.0 mmol) (BuLi; 1.6 M in hexane, 3.75 mL). The mixture was
stirred for 15 min at 0 °C. To the resulting solution of Bu3-
ZnLi (2.0 mmol) at -85 °C was added a THF (1 mL) solution
of triflate 10a (0.39 g, 1.0 mmol), and the mixture was stirred
for 30 min at this temperature. The reaction was quenched
by the addition of aqueous HCl-THF. The mixture was poured
into 1 N aqueous HCl and extracted twice with hexane. The
organic layers were washed with aqueous NaHCO3, dried, and
concentrated in vacuo. Kugelrohr distillation (80-130 °C/20
mmHg) of the residue gave 0.185 g (65% combined yield) of a
1.1:1 mixture of 3-butyltoluene (11a )17 and 4-butyltoluene
(11b).17
For the reactions of 6, 10b (Table 1, entry 3), and 17 (Table
2), the yields of the product 8 were determined by capillary
GC (OV-1, 30 m) analysis by using dodecane as an internal
standard. For the reaction of 10b (Table 1, entry 2), 18, and
24a ,b, the crude products were purified by flash chromatog-
raphy. The spectral data of products, 13,18 25a ,19 25b,20 26a ,16
and 26b21 were in good accordance with reported values.
Rep r esen ta tive P r oced u r e for th e Rea ction of Ar en e-
su lfon a tes w ith Bu 3Zn Li: I2 Tr a p (Eq 5). Triflate 6 (0.35
g, 1.0 mmol) was treated with Bu3ZnLi (2.0 mmol) in THF (7
mL) at -85 °C for 30 min by a procedure similar to that
described above. To the resulting mixture at -85 °C was added
a THF (3 mL) solution of iodine (1.52 g, 6.0 mmol). After being
Ack n ow led gm en t. We would like to thank Profes-
sor Koichiro Oshima of Kyoto University for valuable
discussion on the mechanism of the formation of tet-
rahydrofuran derivative 22.
J O990937M
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