An efficient palladium-catalyzed synthesis of unsymmetrical diaryl sulfones from aryl bromides/triflates and arenesulfinates

Article abstract of DOI:10.1055/s-2003-37117

The palladium-catalyzed coupling of arenesulfinate salts and aryl bromides or triflates provides a simple and extremely efficient route to unsymmetrical diaryl sulfones. The reaction was found to be strongly influenced by the presence of n-Bu₄NCl. The ammonium salt tends to favor the formation of sulfones with neutral, electron-rich and slightly electron-poor aryl bromides or triflates and to hamper the reaction with electron-poor aryl bromides or triflates.

Full text of DOI:10.1055/s-2003-37117

LETTER
361
An Efficient Palladium-Catalyzed Synthesis of Unsymmetrical Diaryl Sulfones
from Aryl Bromides/Triflates and Arenesulfinates
P
S
alladium-Cat
a
alyze
d
Syn
n
thesis of
U
ns
d
ymmetrica
l
r
D
iaryl Su
o
lfones Cacchi,* Giancarlo Fabrizi, Antonella Goggiamani, Luca M. Parisi
Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università degli Studi ‘La Sapienza’,
P.le A. Moro 5, 00185 Roma, Italy
Fax +39(6)49912780; E-mail: sandro.cacchi@uniroma1.it
Received 21 November 2002
would greatly widen its scope and generality and is highly
Abstract: The palladium-catalyzed coupling of arenesulfinate salts
desirable.
and aryl bromides or triflates provides a simple and extremely effi-
cient route to unsymmetrical diaryl sulfones. The reaction was Herein we report that aryl bromides and triflates can be
found to be strongly influenced by the presence of n-Bu NCl. The
ammonium salt tends to favor the formation of sulfones with neu-
tral, electron-rich and slightly electron-poor aryl bromides or trif-
lates and to hamper the reaction with electron-poor aryl bromides or
triflates.
4
successfully employed in the palladium-catalyzed synthe-
sis of unsymmetrical diaryl sulfones via coupling with
arenesulfinate salts (Scheme 1)
O
Key words: coupling, sulfones, palladium, catalysis, arenesul-
finates
Pd cat
1
Ar1
ArSO Na
Ar X
Ar
S
2
O
1
2
3
X = Br, OTf
Scheme 1
Unsymmetrical diaryl sulfones have attracted consider-
1
able interest of late because of their biological activities
2
and chemical properties, and numerous approaches to
their synthesis have been reported, including the oxidation
Using the reaction of sodium p-toluenesulfinate and 4-
bromo biphenyl as a model system, we started out our in-
vestigation by using conditions similar to those employed
by us with aryl iodides and we were pleased to find that
the desired sulfone derivative can be obtained in 87% iso-
lated yield after 24 hours in the presence of Pd (dba) ,
3
of the corresponding sulfides, the sulfonylation of
4
5
arenes, the reaction of organomagnesium halides or or-
6
ganolithium compounds with sulfonate esters, the cop-
per-mediated displacement of nonactivated aryl iodides
7
with arenesulfinates. However, the oxidation process is
2
3
limited by the availability of sulfides, the sulfonylation
approach suffers from the formation of mixtures of
isomeric products and inefficiency with electron-poor
arenes, the employment of organometallic reagents does
not tolerate many functionalities, the copper-mediated
displacement uses an excess of copper iodide compli-
cating the work-up in large scale preparations.
Xantphos [9,9-dimethyl-4,6-bis(diphenylphosphino)xan-
14
thene], Cs CO , n-Bu NCl, in toluene at 120 °C
2
3
4
(
Table 1, entry 2). Addition of n-Bu NCl proved crucial
4
15,16
for the success of the reaction
(Table 1, compare entry
2
with entry 3; see also Table 2, entries 5–8).
When the procedure was extended to electron-poor aryl
bromides, however, a dramatic decrease in efficiency was
observed. In fact, subjection of m-nitrophenyl bromide to
the same reaction conditions afforded the corresponding
sulfone in only 20% yield. In addition, toluenesulfinic
acid 3-nitrophenyl ester 4 (Figure 1), derived from the
competing O-arylation process, was isolated in 17% yield
A copper-catalyzed procedure for the coupling of sul-
finate salts and aryl iodides has been developed. However,
it does not achieve full conversion of aryl bromides and
sulfone products are obtained in low yields when aryl
8
bromides are used.
Recently, we have developed an extremely simple and (Table 1, entry 6).
efficient route to this class of compounds via palladium-
catalyzed reaction of arenesulfinate salts and aryl iod-
ides. This reaction expands the target scope of the pal-
O2N
O
9
S
Me
ladium-catalyzed aryl C-heteroatom bond-forming
O
1
0–13
technology.
While a variety of unsymmetrical diaryl
4
sulfones could be prepared in good to excellent yield,
employment of aryl iodides as the aryl donors was rather
limited to be of broad applicability. Obviously, extension
Figure 1
of the procedure to include aryl bromides and triflates We then explored the influence on the reaction outcome
of some variables, such as ligands, the amounts of sul-
Synlett 2003, No. 3, Print: 19 02 2003.
Art Id.1437-2096,E;2003,0,02,0361,0364,ftx,en;G32002ST.pdf.
finate salts, and the added salts. Using other bidentate
phosphine ligands such as dppf, only trace amounts of sul-
fone were obtained and the yield of compound 4 increased
©
Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

3
62
S. Cacchi et al.
LETTER
Table 1 Ligands, Salts, and Temperature in the Palladium-Catalyzed Reaction of Sodium p-Toluenesulfinate 1 with 4-Bromo Biphenyl or 1-
Bromo-3-nitrobenzenea
Entry
Aryl bromide
Ligand
Salt
Base
Temp (h)
Time (h)
Yield (%)b
3
a
4
1
2
3
4
5
6
7
8
9
p-Ph-C H -Br
Xantphos
Xantphos
Xantphos
Xantphos
Xantphos
Xantphos
dppf
n-Bu NCl
Cs CO
100
120
120
120
120
120
120
120
120
120
120
24
2
11
–
6
4
4
2
3
3
3
n-Bu NCl
Cs CO
87
–
4
2
–
Cs CO
24
24
24
24
24
24
22
27
8
18c
–
–
2
n-Bu NCl
–
–
–
4
–
–
–
m-NO -C H -Br
n-Bu NCl
Cs CO
20
17
43d
–
2
6
4
4
2
3
3
3
3
3
3
n-Bu NCl
Cs CO
traces
27e
19e
28e
89f
4
2
Xantphos
Xantphos
Xantphos
Xantphos
n-Bu NCl
Cs CO
4
2
n-Bu NBr
Cs CO
20
22
–
4
2
1
0
n-Bu NI
Cs CO
4
2
1
1
–
Cs CO
2
a
Unless otherwise stated, reactions were carried out under an argon atmosphere using 1 equiv of bromide, 1.2 equiv of sodium p-toluene-
sulfinate, 0.025 equiv of Pd (dba) , 0.05 equiv of ligand, 1.5 equiv of Cs CO , 1.2 equiv of ammonium salt in toluene at 120 °C.
2
3
2
3
b
c
d
e
f
Yields are given for isolated products.
-Bromo biphenyl was recovered in 74% yield.
Sulfinic acid ester was isolated in 30% yield by using Pd(OAc)2.
Compound 1: Aryl bromide = 2:1.
Compound 3 was isolated in 73% yield (24 h) by using p-Me-C H -SO Li.
4
6
4
2
to 43% (Table 1, entry 7). Increasing the sulfinate salt to electron-rich and electron-poor aryl and heteroaryl brom-
aryl bromide molar ratio produced only a moderate in- ides or triflates and tolerates a variety of functional
crease of the yield (Table 1, entry 8) and the employment groups, including ether, cyano, aldehyde, and nitro
of other ammonium salts did not provide any beneficial groups.
effect. Use of both n-Bu NBr and n-Bu NI produced
low yields of the sulfone derivative and almost equi-
molar amounts of the sulfinic acid ester (Table 1, entries
4
4
As to the mechanism, most probably the reaction proceeds
through the following basic steps: (a) oxidative addition
of aryl bromide or triflate to Pd(0), (b) nucleophilic dis-
placement of bromide or triflate to give an arylsul-
9
and 10).
Almost surprisingly, the best result in terms of yield and fonylpalladium intermediate, (c) reductive elimination of
reaction time was obtained by omitting the ammonium a Pd(0) species to generate the sulfone product. The rea-
salt (Table 1, entry 11). None of the sulfinic acid ester was son of the unexpected divergent effect of n-Bu NCl on
4
observed under these conditions. The negative effect of n- the reaction course is still unclear.
Bu NCl on the reaction yield observed with m-nitrophe-
nyl bromide was not limited to this compound but resulted
to be quite general with electron-poor aryl bromides and
triflates. A variety of aryl donors of this type afforded sul-
4
Table 2 Synthesis of Unsymmetrical Diaryl Sulfones through the
Palladium-Catalyzed Reaction of Sodium p-Toluenesulfinate 1 with
Aryl and Heteroaryl Bromides or Triflates 2a
fone products in low yields in the presence of n-Bu NCl
Yield (%)b,c
of 3
4
Entry
Aryl/heteroaryl bromide Proce-
Time
(h)
(
Table 2, entries 21, 24, 26, 29, 31, 33) or, in any case,
or triflate 2
dure
lower than without n-Bu NCl.
4
1
2
3
4
5
6
p-Me-C H -Br
A
2.5
2
93
92
67
82
93
46
6
4
Therefore, two general procedures were employed when
the reaction was extended to include other aryl bromides
and triflates: sodium p-toluenesulfinate, Pd (dba) , Xant-
m-Me-C H -Br
A
6
4
2
3
p-Bu-t-C H -Br
A
24
2
6
4
phos, Cs CO , 120 °C, toluene with n-Bu NCl (procedure
2
3
4
3,5-Me -C H -Br
A
A: neutral, electron-rich, and slightly electron-poor aryl
bromides or triflates) and without n-Bu NCl (procedure
B: electron-poor aryl bromides or triflates).
2
6
4
4
p-MeO-C H -Br
A
24
24
6
4
1
7,18
p-MeO-C H -Br
B
6
4
Under these conditions, the reaction gives unsymmetrical
diaryl sulfones in good to high yields with many neutral,
Synlett 2003, No. 3, 361–364 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Palladium-Catalyzed Synthesis of Unsymmetrical Diaryl Sulfones
363
Table 2 Synthesis of Unsymmetrical Diaryl Sulfones through the
Palladium-Catalyzed Reaction of Sodium p-Toluenesulfinate 1 with
Aryl and Heteroaryl Bromides or Triflates 2 (continued)
To sum up, we have developed an efficient and general
synthetic approach for the preparation of unsymmetrical
diaryl sulfones from readily available starting materials.
Further work is in progress along this line.
a
Entry
Aryl/heteroaryl bromide Proce-
Time
(h)
Yield (%)b,c
of 3
or triflate 2
dure
A
B
7
8
9
p-MeO-C H -OTf
22
22
7
89
Acknowledgment
6
4
Work carried out in the framework of the National Project ‘Stereo-
selezione in Sintesi Organica. Metodologie ed Applicazioni’ sup-
ported by the Ministero dell’Università e della Ricerca Scientifica e
Tecnologica. Financial support of this research by the University
p-MeO-C H -OTf
72
6
4
PhBr
A
A
A
A
A
A
B
91
1
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
9
PhOTf
7
82
‘La Sapienza’ is also gratefully acknowledged.
p-Ph-C H -Br
2
87
6
4
References
p-Ph-C H -ONf
6
71
6
4
(
1) (a) Jones, T. R.; Webber, S. E.; Varney, M. D.; Reddy, M.
R.; Lewis, K. K.; Kathardekar, V.; Mazdiyasni, H.; Deal, J.;
Nguyen, D.; Welsh, K. M.; Webber, S.; Johnson, A.;
Matthews, D. A.; Smith, W. W.; Janson, C. A.; Bacquet, R.
J.; Howland, E. F.; Booth, C. L. J.; Ward, R. W.; Herrmann,
S. M.; White, J.; Bartlett, C. A.; Morse, C. A. J. Med. Chem.
1997, 40, 677. (b) Neamati, N.; Mazumder, A.; Zhao, H.;
Sunder, S.; Burke Terrence, R. Jr.; Schultz, R. J.; Pommier,
Y. Antimicrob. Agents Chemother. 1997, 41, 385.
m-MeO-C H -Br
2
90
6
4
p-F-C H -Br
19
24
24
24
10
8
74 (21)
73
6
4
p-F-C H -Br
6
4
m-F-C H -Br
A
B
73
6
4
m-F-C H -Br
80
6
4
(
c) Caron, G.; Gaillard, P.; Carrupt, P. A.; Testa, B. Helv.
m-CF -C H -Br
A
A
73
3
6
4
Chim. Acta 1997, 80, 449. (d) Prasit, P.; Wang, Z.; Brideau,
C.; Chan, C.-C.; Charleson, S.; Cromlish, W.; Ethier, D.;
Evans, J. F.; Ford-Hutchinson, A. W.; Gauthier, J. Y.;
Gordon, R.; Guay, J.; Gresser, M.; Kargman, S.; Kennedy,
B.; Leblanc, Y.; Léger, S.; Mancini, J.; O’Neill, G. P.;
Ouellet, M.; Percival, M. D.; Perrier, H.; Riendeau, D.;
Rodger, I.; Tagari, P.; Thérien, M.; Vickers, P.; Wong, E.;
Xu, L.-J.; Young, R.-N.; Zamboni, R. Bioorg. Med. Chem.
Lett. 1999, 9, 1773. (e) Dinsmore, C. J.; Williams, T. M.;
O’Neill, T. J.; Liu, D.; Rands, E.; Culberson, J. C.; Lobell,
R. B.; Koblan, K. S.; Kohl, N. E.; Gibbs, J. B.; Oliff, A. I.;
Graham, S. L.; Hartman, G. D. Bioorg. Med. Chem. Lett.
1999, 9, 3301. (f) Seydel, J. K.; Burger, H.; Saxena, A. K.;
Coleman, M. D.; Smith, S. N.; Perris, A. D. Quant. Struct.-
Act. Rel. 1999, 18, 43. (g) Sun, Z.-Y.; Botros, E.; Su, A.-D.;
Kim, Y.; Wang, E.; Baturay, N. Z.; Kwon, C.-H. J. Med.
Chem. 2000, 43, 4160.
80
Br
2
2
2
2
2
2
2
2
2
2
3
3
3
0
1
2
3
4
5
6
7
8
9
0
1
2
p-CN-C H -Br
B
A
B
B
A
B
A
B
B
A
B
A
B
7
85
6
4
p-CN-C H -Br
24
22
7
35 (14)
67
6
4
p-CN-C H -OTf
6
4
m-CN-C H -Br
85
6
4
m-CN-C H -Br
24
8
40 (23)
89
6
4
m-NO -C H -Br
2
6
4
m-NO -C H -Br
24
37
5
20 (17)
65
2
6
4
(
2) (a) Fumio, H.; Mitsuru, K. JP Patent 61271271, 1986; Chem.
Abstr. 1986, 106, 61271271. (b) Keiichi, S.; Toru, O.; Aki,
S. JP Patent 04120050, 1992; Chem. Abstr. 1992, 117,
p-CHO-C H -Br
6
4
p-NO -C H -Br
78 (7)
57
2
6
4
150703. (c) Toshiaki, T.; Takeshi, Y. JP Patent 2001260544,
p-NO -C H -Br
5
2001; Chem. Abstr., 2001, 135, 264604.
2
6
4
(
3) Schank, K. In The Chemistry of Sulfones and Sulfoxides;
Patai, S.; Rappoport, Z.; Stirling, C. J. M., Eds.; Wiley: New
York, 1988, Chap. 7.
p-NO -C H -OTf
20
20
24
57 (19)
traces
52
2
6
4
p-NO -C H -OTf
2
6
4
(
4) (a) Graybill, B. M. J. Org. Chem. 1967, 32, 2931. (b) Ueda,
M.; Uchiyama, K.; Kano, T. Synthesis 1984, 323. (c)Truce,
W. E.; Klinger, T. C.; Brand, W. W. In Organic Chemistry
of Sulfur; Oae, S., Ed.; Plenum Press: New York, 1977.
Br
N
N
(
2
d) Nara, S. J.; Harjani, J. R.; Salunkhe, M. M. J. Org. Chem.
001, 66, 8616. (e) Frost, C. G.; Hartley, J. P.; Whittle, A. J.
3
3
A
24
28
Br
Synlett 2001, 830. (f) Bandgar, B. P.; Kasture, S. P. Synth.
Commun. 2001, 31, 1065.
a
(5) Gilman, H.; Beaver, N. J.; Meyers, C. H. J. Am. Chem. Soc.
925, 47, 2047.
Reaction conditions: (procedure A) 1.0 equiv of bromide or triflate,
1
1
0
.2 equiv of sodium p-toluenesulfinate, 0.025 equiv of Pd (dba) ,
2
3
(6) Baarschers, W. H. Can. J. Chem. 1976, 54, 3056.
(7) Suzuki, H.; Abe, H. Tetrahedron Lett. 1995, 36, 6239.
(8) Baskin, J. M.; Wang, Z. Org. Lett. 2002, 4, 4423.
.05 equiv of Xantphos, 1.5 equiv of Cs CO , 1.2 equiv of n-Bu NCl,
2
3
4
toluene, 120 °C, under argon; (procedure B) same molar ratios, sol-
vent, and temperature of procedure A omitting n-Bu NCl.
4
b
(9) Cacchi, S.; Fabrizi, G.; Goggiamani, A.; Parisi, L. M. Org.
Lett., in press.
Yields are given for isolated products.
Figures in parentheses refer to isolated sulfinic esters.
c
Synlett 2003, No. 3, 361–364 ISSN 0936-5214 © Thieme Stuttgart · New York

3
64
S. Cacchi et al.
LETTER
Soc. 1997, 119, 12441. (k) Cook, G. R.; Shanker, P. S.
(
10) For some reviews on the substitution of aryl C-halogen
bonds with aryl C-N bonds, see: (a) Hartwig, J. F. Synlett
Tetrahedron Lett. 1998, 39, 4991. (l)Roesch, K. R.; Larock,
R. C. Org. Lett. 1999, 1, 1551. (m) Amatore, C.; Jutand, A.
Acc. Chem. Res. 2000, 33, 314; and the references therein.
(n) Wang, Z.; Zhang, Z.; Lu, X. Organometallics 2000, 19,
775. (o) Arcadi, A.; Cacchi, S.; Fabrizi, G.; Marinelli, F.;
Pace, P. Eur. J. Org. Chem. 2000, 4099. (p) Zhang, Z.; Lu,
X.; Xu, Z.; Zhang, Q.; Han, X. Organometallics 2001, 20,
3724. (q) Larock, R. C.; Reddy, C. K. J. Org. Chem. 2002,
67, 2027.
1
997, 329. (b) Baranano, D.; Mann, G.; Hartwig, J. F. Curr.
Org. Chem. 1997, 1, 287. (c) Hartwig, J. F. Acc. Chem. Res.
998, 31, 852. (d) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.;
Buchwald, S. L. Acc. Chem. Res. 1998, 31, 805.
1
(e) Hartwig, J. F. Angew. Chem. Int. Ed. 1998, 37, 2046.
(f) Hartwig, J. F. Pure Appl. Chem. 1999, 71, 1417.
(g) Yang, B. H.; Buchwal d, S. L. J. Organomet. Chem.
1999, 576, 125.
(
11) For the substitution of aryl C-halogen bonds with aryl C-PR2
bonds, see: (a) Herd, O.; Hessler, A.; Hingst, M.; Tepper,
M.; Stelzer, O. J. Organomet. Chem. 1996, 522, 69.
(16) For the influence of halide additives on divalent palladium-
catalyzed reactions, see: (a) Bäckvall, J. E.; Nordberg, R. E.
J. Am. Chem. Soc. 1980, 102, 393. (b) Bäckvall, J. E.;
Äkermark, B.; Ljunggren, S. O. J. Am. Chem. Soc. 1979,
101, 2411. (c) Simone, D. O.; Kennelly, T.; Brungard, N. L.;
Farrauto, R. J. Appl. Catal. 1991, 70, 87. (d) Francis, J. W.;
Henry, P. M. J. Mol. Catal. 1995, 99, 77. (e) Harrington, P.
J. In Comprehensive Organometallic Chemistry II, Vol. 12;
Abel, E. W.; Stone, F. G. A.; Wilkinson, G., Eds.; Pergamon:
New York, 1995, 797. (f) Harrington, P. J. In
(
b) Herd, O.; Hessler, A.; Hingst, M.; Machnitzki, P.;
Tepper, M.; Stelzer, O. Cat. Today 1998, 42, 413.
c) Machnitzki, P.; Nickel, T.; Stelzer, O.; Landgrafe, C.
(
Eur. J. Inorg. Chem. 1998, 1029. (d) Kraatz, H.-B.; Pletsch,
A. Tetrahedron: Asymmetry 2000, 11, 1617.
(
e) Machnitzki, P.; Tepper, M.; Wenz, K.; Stelzer, O.;
Herdtweck, E. J. Organomet. Chem. 2000, 602, 158.
f) Hessler, A.; Kottsieper, K. W.; Schenk, S.; Tepper, M.;
(
Comprehensive Organometallic Chemistry II, Vol. 12; Abel,
E. W.; Stone, F. G. A.; Wilkinson, G., Eds.; Pergamon: New
York, 1995, 904. (g) Widenhoefer, R. A.; Buchwald, S. L.
Organometalllics 1996, 15, 2755. (h) Bäckvall, J. E. In
Metal-Catalyzed Cross-Coupling Reactions; Diederich, F.;
Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998, 339–385.
(17) For other reactions in which electron-rich and electron-poor
substrates require different conditions, see for example:
Stelzer, O. Z. Naturforsch. B 2001, 56, 347. (g) Brauer, D.
J.; Hingst, M.; Kottsieper, K. W.; Liek, C.; Nickel, T.;
Tepper, M.; Stelzer, O.; Sheldrick, W. S. J. Organomet.
Chem. 2002, 645, 14.
(
(
12) For the substitution of aryl C-halogen bonds with aryl C-
PO(OR) bonds, see: (a) Hirao, T.; Masunaga, T.; Ohshiro,
2
Y.; Agawa, O. Synthesis 1981, 56. (b) Xu, Y.; Zhang, J. J.
Chem. Soc., Chem. Commun. 1986, 1606. (c) Casalnuovo,
1
0d
(a) Ref. (b) Yin, J.; Buchwald, L. S. Org. Lett. 2000, 2,
1101. (c) Cacchi, S.; Fabrizi, G.; Goggiamani, A.; Zappia,
G. Org. Lett. 2001, 3, 2539. (d) Rutherford, J. F.; Rainka,
M. P.; Buchwald, S. L. J. Am. Chem. Soc., article as soon as
possible.
A. L.; Calabrese, J. C. J. Am. Chem. Soc. 1990, 112, 4324.
1c
(
d) Ref.1
13) For the substitution of aryl C-halogen bonds with aryl C-SR
bonds, see: (a) Harayama, H.; Nagahama, T.; Kozera, T.;
Kimura, M.; Fugami, K.; Tanaka, S.; Tamaru, Y. Bull.
Chem. Soc. Jpn. 1997, 70, 445. (b) Kato, K.; Ono, M.;
Akita, H. Tetrahedron Lett. 1997, 38, 1805. (c) Shopfer, U.;
Schlapbach, A. Tetrahedron 2001, 57, 3069. (d) Menger, F.
M.; Azov, V. A. J. Am. Chem. Soc. 2002, 124, 11159.
14) Kranenburg, M.; van der Burgt, Y. E. M.; Kramer, P. C. J.;
van Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J.
Organometallics 1995, 14, 3081.
(18) Typical Procedure for the Preparation of Unsymmetrical
Diaryl Sulfones with Electron-Poor Aryl Bromides or
Triflates (Procedure B) (Table 2, Entry 28): In a Carousel
Tube Reaction (Radley Discovery), to a solution of sodium
p-toluenesulfinate (0.075 g, 0.420 mmol) and p-nitrophenyl
bromide (0.0707 g, 0.350 mmol) in 2.0 mL of toluene under
argon, Pd (dba) (0.008 g, 0.009 mmol), Xantphos (0.010 g,
(
(
2
3
0.018 mmol) and Cs CO (0.171 g, 0.525 mmol) were
2
3
15) For the influence of halide additives on Pd(0)-catalyzed
reactions, see: (a) Jeffery, T. J. Chem. Soc., Chem. Commun.
added. The mixture was warmed at 120 °C under stirring for
5 h. After cooling, the reaction mixture was diluted with
ethyl acetate, washed with water, dried over Na SO and
1984, 1287. (b) Scott, J. W.; Crisp, G. T.; Stille, J. K. J. Am.
2
4
Chem. Soc. 1984, 106, 4630. (c) Amorese, A.; Arcadi, A.;
Bernocchi, E.; Cacchi, S.; Cerrini, S.; Fedeli, W.; Ortar, G.
Tetrahedron 1989, 45, 813. (d) Larock, R. C.; Leung, W.-
Y.; Stolz-Dunn, S. Tetrahedron Lett. 1989, 30, 6629.
concentrated under reduced pressure. The reaction mixture
was purified by chromatography (silica gel, 35 g; n-hexane/
ethyl acetate 80/20 v/v) to give 0.076 g of p-nitrophenyl p-
tolyl sulfone (78% yield): Mp 164–165 °C. IR (KBr): 2926,
–
1 1
(
e) Loupy, A.; Tchoubar, B. Salt Effects in Organic and
1351, 1157 cm . H NMR (CDCl ): δ = 8.31 (d, J = 8.9 Hz,
3
Organometallic Chemistry; VCH: Weinheim, 1992, 254–
2 H), 8.10 (d, J = 8.9 Hz, 2 H), 7.84 (d, J = 8.4 Hz, 2 H), 7.34
1
3
272. (f) Jeffery, T.; Gallang, J. C. Tetrahedron Lett. 1994,
(d, J = 8.1 Hz, 2 H), 2.41 (s, 3 H). C NMR (CDCl ): δ =
3
3
5, 4103. (g) Herrmann, W. H.; Brossmer, C.; Öfele, K.;
150.3, 147.9, 145.5, 137.1, 130.4, 128.9, 128.2, 124.5, 21.7.
Anal Calcd for C H O S: C, 56.31; H, 4.00. Found: C,
56.23; H, 3.99.
Reisinger, C.-P.; Priermeier, T.; Beller, M.; Fisher, H.
Angew. Chem., Int. Ed. Engl. 1995, 34, 1844. (h) Cacchi,
S.; Fabrizi, G.; Marinelli, F.; Pace, P. Tetrahedron 1996, 52,
1
3
11
4
With neutral, electron-rich and slightly electron-poor aryl
10225. (i) Jeffery, T. Tetrahedron 1996, 52, 10113.
bromides or triflates, 1.2 equiv of n-Bu NCl were added
4
(
j) Goodson, F. E.; Wallow, T. I.; Novak, B. M. J. Am. Chem.
(procedure A).
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