J. CHEM. RESEARCH (S), 1999 401
2-Benzoylthiophene 3e. Recrystallized from light petroleum mp
56^57 8C (lit.11 56±58 8C); dH (60 MHz, CDCl3) 7.12 (m, 1H),
best was K2CO3 which suppressed the formation of biaryl
byproducts (<10%) under an atmosphere of carbon
monoxide.
7.28±8.03 (m, 7H); IR (KBr) n 1620, 1590, 1400, 1280, 830, 700,
1
640 cm
.
Diphenyliodonium tetra£uoroborate 1a reacted with
potassium phenyltri£uoroborate 2a in the presence of
5 mol% Pd(OAc)2 and K2CO3 in DME at room tempera-
ture to give benzophenone 3a in 92% yield. When
diphenyliodonium chloride and tosylate were used in place
of the tetra£uoroborate the reaction required a longer time
of 6 h and gave a lower yield (57%) of product. This
indicates that the tetra£uoroborate counter is superior to
halide and tosylate counter ions in this reaction. This
carbonylative coupling could be successfully applied to
other potassium aryltri£uoroborates. With potassium
p-methylphenyltri£uoroborate 2b and o-methoxyphenyl-
4,40-Dimethylbenzophenone 3f. Recrystallized from ethanol, mp
92^93 8C (lit.12 95 8C); dH (60 MHz, CDCl3) 2.36 (s, 6H) 7.20
and 7.64 (AB q, 8H); IR (KBr) n 1640, 1600, 1280, 1180, 750
1
cm
.
4-Methyl-40-methoxybenzophenone 3g. Recrystallized from
ethanol, mp 102^103 8C (lit.13 105±107 8C); dH (60 MHz, CDCl3)
2.40 (s, 3H), 3.86 (s, 3H), 6.90 (m, 2H), 7.21(m, 2H), 7.64 (m, 2H),
7.74 (m, 2H); IR (KBr) n 2980, 1650, 1600, 1450, 1260, 1020, 850,
1
760, 690 cm
E-40-Methylchalcone 3h. Recrystallized from light petroleum mp
56^57 8C (lit.14 59^60 8C) dH (60 MHz, CDCl3) 2.36 (s, 3H),
7.15±7.75 (m, 9H), 7.98 (m, 2H); IR (KBr) n 1665, 1610, 1340,
1
1210, 820, 760, 700 cm
.
4-Chloro-40-methylbenzophenone 3j. Recrystallized from light
tri£uoroborate
2c,
p-methylbenzophenone
3i
and
petroleum, mp 125^127 8C (lit.15 129±130 8C); dH (60 MHz, CDCl3)
o-methoxybenzophenone 3k were obtained in 88 and 80%
yields, respectively. The reaction could also be extended
to other iodonium salts 1b, 1c and 1g under the same con-
ditions. As for unsymmetric 2-thienylphenyliodonium
tosylate 1f, it could also undergo facile coupling with
potassium phenytri£uoroborate 2a to give 2-benzoyl-
thiophene 3e as the single coupling product. Similarly,
(E)-phenylethenyl(phenyl)iodonium tetra£uoroborate 1d
also underwent carbonylation with potassium phenyl-
2.38 (s, 3H), 7.36 and 7.49 (AB q, 8H) IR (KBr) n 3050, 1640,
1
1600, 1280, 840, 750, 700 cm
.
2-Methoxybenzophenone 3k. Recrystallized from ethanol, mp
36^37 8C (lit.16 40 8C); dH (60 MHz, CDCl3) 3.90 (s, 3H), 6.90
(m, 2H), 7.67 (m, 5H), 8.20 (m, 2H); IR (KBr) n 3050, 2960, 1680,
1
1590, 1250, 1170, 1020, 840, 790, 740, 700 cm
.
2-Methoxy-40-methylbenzophenone 3l. Recrystallized from
ethanol, mp 61^62 8C (lit.17 64±65 8C); dH (60 MHz, CDCl3) 2.43
(s, 3H), 3.93 (s, 3H), 6.80±7.20 (m, 2H), 7.20±7.60 (m, 4H),
7.90±8.20 (m, 2H), IR (KBr) n 3050, 2985, 1660, 1260, 1030, 825,
1
740, 690 cm
.
tri£uoroborate
2a
and
potassium
p-methylphenyltri£uoroborate 2b under the same conditions
to produce (E)-chalcone 3d and (E)-p-methylchalcone 3h in
85 and 82% yields, respectively.
We are grateful for ¢nancial support by the National
Science Foundation of China (Project 29472036).
It has been reported that hydroxy(tosyloxy)iodobenzene.
PhI(OH)OTs, could be utilized in a coupling reaction with
organoboron compounds in the presence of a palladium
catalyst to give biaryls as products.6 However, under the
same conditions of this carbonylation in reaction with
potassium phenyltrilluoroborate 2a was not obtained and
biphenyl was formed in 81% yield.
Received, 4th February 1999; Accepted, 17th March 1999
Paper E/9/00963I
In summary, potassium aryltri£uoroborates are alterna-
tive organoboron compounds that can be applied to
palladium-catalyzed carbonylative coupling of iodonium
salts to give ketones under mild conditions in good yields.
References
1
N. Miyaura and A. Suzuki, Chem. Rev., 1996, 95, 2457: A.
Suzuki, Pure Appl. Chem., 1985, 57, 1749; 1991, 63, 419; 1994,
66, 213.
E. Vedejs, S. C. Fields and M. R. Schrimpf, J. Am. Chem.
Soc., 1993, 115, 11612; E. Vedejs, S. C. Fields, S. Lin and
M. R. Schrimpf, J. Org. Chem., 1995, 60, 3028.
S. Darses and J. P. Genet, Tetrahedron Lett., 1997, 38, 4393.
Part XXXIII: submitted to Synth Commun.
S. K. Kang, T. Yamaguchi, T. H. Kim and P. S. Ho, J. Org.
Chem., 1996, 61, 9082; S. K. Kang, T. Yamaguchi, P. S.
Ho, W. Y. Kim and H. C. Ryu, J. Chem. Soc., Perkin. Trans.
1, 1998, 841; S. K. Kang, P. S. Ho, S. K. Yoo, J. C. Lee
and K. J. Lee, Synthesis, 1998, 823; S. K. Kang, K. H. Lim,
P. S. Ho and W. Y. Kim, Synthesis, 1997, 874.
S. K. Kang, H. W. Lee, S. B. Jang and P. S. Ho, J. Org.
Chem., 1996, 61, 4720.
The Merck Index: an encyclopedia of chemicals, drugs and
biochemicals, Chapman and Hall, London 10th edn., p. 1101.
A. G. Davies, J. Kenyon, R. J. Lyons and T. A. Rohen, J.
Chem. Soc., 1954, 3474.
2
Experimental
Typical Procedure for the Palladium-catalyzed Carbonylation of
Iodonium Salts and Potassium Aryltri£uoroborates.öUnder an
atmospheric pressure of carbon monoxide, 1.2 mmol potassium
aryltri£uoroborate in 10 ml DME was injected into a mixture of 1
mmol iodonium salt, 1.5 mmol K2CO3 and 5 mmol% Pd(OAc)2.
The resulting mixture was stirred at room temperature for 2 h, then
diluted with saturated aqueous NH4Cl and extracted with 2 Â 5
ml diethyl ether. The combined organic layer was dried over anhy-
drous MgSO4 and the solvent removed in vacuo. The residue was
isolated by TLC (silica gel) with EtOAc^n-hexane (1:10) as developer
to give ketone product which was puri¢ed by recrystallization from
ethanol or light petroleum (bp 50^60 8C)
3
4
5
6
7
8
9
Physical and Spectroscopic Data for the Products.ö
Benzophenone 3a. Recrystallized from ethanol, mp 48^50 8C (lit.7
49±51 8C); dH (60 MHz, CDCl3), 7.47 (s, 4H), 7.60 (m, 2H), 7.80
(m, 4H; IR (KBr) 3050, 1650, 1600, 1450, 1270, 760, 700, 640
A. Staab and E. Jost, Justus Liebigs Ann. Chem., 1962, 655,
90.
1
cm
.
4-Methylbenzophenone 3b. Recrystallized from light petroleum,
10 The Merck Index, 10th edn., p. 1991.
mp 56^57 8C (lit.8 59.5 8C); dH (60 MHz, CDCl3) 2.39 (s, 3H),
7.22 (m, 2H), 7.32±7.84 (m, 7H); IR (KBr) 3050, 1650, 1600, 1280,
11 H. Gilman, Org. Synth., 1932, 12, 62.
12 M. Ryang and S. Tsutsumi, Bull. Chem. Soc. Jpn., 1962, 35,
1121.
13 K. Suzuki, H. Kitagawa and T. Mukaoyama, Bull. Chem. Soc.
Jpn., 1993, 66, 3729.
14 Beilsteins Handbuch Der Organischen Chemie, vol. 7, p. 490.
15 J. Rhee, M. Ryang, T. Watanabe, H. Omura, S. Murai and N.
Sonode, Synthesis, 1977, 776.
16 R. Stoermer and E. Fredrici, Chem. Ber., 1918, 41, 332.
17 M. Okubo, S. Hayashi, M. Matsunaga and Y. Uematsu, Bull.
Chem. Soc. Jpn., 1981, 54, 2337.
1
730, 700 cm
.
4-Chlorobenzophenone 3c. Recrystallized from ethanol, mp
74^76 8C (lit.9 75±77 8C); dH (60 MHz, CDCl3) 7.33 (m, 2H,
7.30±7.70 (m, 5H), 7.66 (m, 2H); IR (KBr) n 3030, 1650, 1590,
1
1280, 1090, 840, 790, 730, 700 cm
.
E-Chalcone 3d. Recrystallized from light petroleum, mp 53^54 8C
(lit.10 55±57 8C) dH (60 MHz, CDCl3) 7.22±7.80 (m, 10H), 8.00 (m,
2H); IR (KBr) n 3040, 1660, 1600, 1450, 1330, 1210, 1010, 750, 690
1
cm
.