300
J . Org. Chem. 2001, 66, 300-302
Notes
Sch em e 1
Oxova n a d iu m (V)-In d u ced Oxid a tive Liga n d
Cou p lin g of Ar yltr im eth ylzin ca tes
P r ep a r ed fr om Br om oa r en es a n d Dilith iu m
Tetr a m eth ylzin ca te
Takashi Takada, Hidehiro Sakurai, and
Toshikazu Hirao*
Department of Applied Chemistry, Faculty of
Engineering, Osaka University,
Yamada-oka, Suita, Osaka 565-0871, J apan
hirao@ap.chem.eng.osaka-u.ac.jp
Received J une 28, 2000
Sch em e 2
Oxidative transformation of main-group organometal-
lics has been expected to develop the selective carbon-
carbon bond forming reaction between two ligands on
their metals.1,2 We have already reported that the selec-
tive ligand coupling of organoaluminums, organoborons,
organozincs, and/or their ate complexes is induced by
oxovanadium(V) compounds as oxidants.3 Although aryl-
aryl homocoupling compounds are occasionally formed as
byproducts in these coupling reactions, depending on the
reaction conditions, use of iodine-zinc exchange4 of
iodoarenes with Me3ZnLi suppresses such an aryl-aryl
coupling of aryldimethylzincates,3c to give methylarenes5
chemoselectively (Scheme 1). However, the coupling
reaction is only applied to iodoarene, because the similar
halogen-zinc exchange reaction with Me3ZnLi does not
proceed with bromoarenes. Recently, Uchiyama et al.
Ta ble 1. Rea ctivities of 1 in Sch em e 2
yield (%)b
entry
1
additivea
2
3
4
(1) For cupper(I)-induced oxidative coupling reactions of organobo-
rons and organozincs, see: (a) Yamamoto, Y.; Yatagai, H.; Maruyama,
K.; Sonoda, A.; Murahashi, S. J . Am. Chem. Soc. 1977, 99, 5652. (b)
Iyoda, M.; Kabir, S. M. H.; Vorasingha, A.; Kuwatani, Y.; Yoshida, M.
Tetrahedron Lett. 1998, 39, 5393.
1
1a
1b
1c
1a
1c
TMSCl
TMSCl
TMSCl
VO(OEt)Cl2
VO(OEt)Cl2
98
-
-
-
-
-
45
-
2c
3
-
52
-
39
34
86
4
5
-
(2) Oxidative tranformation of d0 organometallics was also reported,
see: (a) J ordan, R. F.; LaPointe, R. E.; Bajgure, C. S.; Echols, S. F.;
Willet, R. J . Am. Chem. Soc. 1987, 109, 4111. (b) Borkowsky, S. L.;
Baenziger, N. C.; J ordan, R. F. Organometallics 1993, 12, 486. (c) Burk,
M. J .; Tumas, W.; Ward, M. D.; Wheeler, D. R. J . Am. Chem. Soc. 1990,
112, 6133. (d) Sato, M.; Mogi, E.; Kumakura, S. Organometallics 1995,
14, 3157. (e) Hayashi, Y.; Osawa, M.; Wakatsuki, Y. J . Organomet.
Chem. 1997, 542, 241.
TMSCl (10.0 equiv); VO(OEt)Cl2 (3.0 equiv). b 1H NMR yield.
a
c 1b was recovered quantitatively.
demonstrated that dilithium tetramethylzincate,
Me4ZnLi2, is effective for the chemoselective bromine-
zinc exchange of p-substituted bromoarenes.6 These
results prompted us to investigate the oxovanadium(V)-
induced coupling reaction of the organozincates, prepared
from various bromoarenes and Me4ZnLi2.
The reactivities of Me4ZnLi2 toward o-, m-, and p-
bromoanisoles were first examined by quenching with
chlorotrimethylsilane (Scheme 2). As shown in Table 1,
the bromine-zinc exchange reaction of p-bromoanisole
(1a ) with Me4ZnLi2 proceeded smoothly in THF at 0 °C
for 2 h to yield p-trimethylsilylanisole quantitatively
(entry 1).6 On the other hand, the reaction of m-bro-
moanisole (1b) led to the recovery of the starting mate-
(3) (a) Ishikawa, T.; Ogawa, A.; Hirao, T. J . Am. Chem. Soc. 1998,
120, 5124. (b) Ishikawa, T.; Nonaka, S.; Ogawa, A.; Hirao, T. J . Chem.
Soc., Chem. Commun. 1998, 1209. (c) Hirao, T.; Takada, T.; Ogawa,
A. J . Org. Chem. 2000, 65, 1511. Oxidative tranformation of orga-
nozirconiums as d0 organometallics was also reported, see: (d) Ish-
ikawa, T.; Ogawa, A.; Hirao, T. J . Organomet. Chem. 1999, 575, 76.
(4) Kondo, Y.; Takazawa, N.; Yamazaki, C.; Sakamoto, T. J . Org.
Chem. 1994, 59, 4717.
(5) Other methylation method of haloarene was reported. For some
examples for transition metal catalyzed cross-coupling of organome-
tallics, see: (a) Hossain, M. K.; Takagi, K. Chem Lett. 1999, 1241. (b)
Blum, J .; Gelman, D.; Baidossi, W.; Shakh, E.; Rosenfeld, A.; Aizen-
shtat, Z.; Wassermann, B. C.; Frick, M.; Heymer, B.; Schutte, S.;
Wernik, S.; Schumann, H. J . Org. Chem. 1997, 62, 8681. (c) Kondo,
Y.; Matsudaira, T.; Sato, J .; Murata, N.; Sakamoto, T. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 736. (d) Kauffmann, T.; Nienaber, H. Synthesis
1995, 207. (e) Vedejs, E.; Haight, A. R.; Moss, W. O. J . Am. Chem.
Soc. 1992, 114, 6556. For some examples for methylation of aryllithium
with methylhalide, see: (f) Ebdrup, S. Synthesis 1998, 1107. (g) Ebert,
G. W.; Pfenning, D. R. Tetrahedron Lett. 1993, 34, 2279. (h) Suchan,
S. D.; Donovan, T. A., J r. Tetrahedron Lett. 1990, 31, 4129. (i) Morrell,
D. G.; Kochi, J . K. J . Am. Chem. Soc. 1975, 97, 7262.
(6) (a) Uchiyama, M.; Kameda, M.; Mishima, O.; Yokoyama, N.;
Koike, M.; Kondo, Y.; Sakamoto, T. J . Am. Chem. Soc. 1998, 120, 4934.
(b) Uchiyama, M.; Koike, M.; Kameda, M.; Kondo, Y.; Sakamoto, T. J .
Am. Chem. Soc. 1996, 118, 8733.
10.1021/jo000976u CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/15/2000