ORGANIC
LETTERS
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999
Vol. 1, No. 9
323-1326
New Efficient Nickel- and
Palladium-Catalyzed Cross-Coupling
Reactions Mediated by
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Tetrabutylammonium Iodide
†
†
‡
,†
Michael Piber, Anne Eeg Jensen, Mario Rottl a1 nder, and Paul Knochel*
Institut f u¨ r Organische Chemie, Ludwig-Maximilians-UniVersit a¨ t M u¨ nchen,
Butenandtstrasse 5-13, Haus F, 81377 M u¨ nchen, Germany, and H. Lundbeck A/S,
OttiliaVej 9, DK-2500 Valby, Denmark
Received July 6, 1999
ABSTRACT
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The addition of Bu NI has been found to accelerate the palladium(0)-catalyzed cross-coupling between benzylic zinc bromides and aryl or
alkenyl triflates. Remarkably, it further allows a new nickel(0)-catalyzed cross-coupling between functionalized benzylic zinc reagents and
primary alkyl iodides leading to polyfunctional products in good yields under mild reaction conditions (0−20 °C, 4−16 h).
Transition metal-catalyzed cross-coupling reactions beetween
C sp centers have been extensively studied and several
of dialkylzincs or arylzinc derivatives in the presence of m-
or p-trifluoromethylstyrene or 4-fluorostyrene (1) as promotor
proceeds under mild conditions and in satisfactory yields.
Attempts to perform cross-coupling reactions between ben-
zylic zinc bromides and alkyl iodides in the presence of the
nickel catalytical system failed completely, whereas sluggish
reactions were observed between benzylic zinc derivatives
and various aryl triflates in the presence of palladium(0).
What attracted our attention was the use of ammonium salts
2
1
2
3
efficient Pd-, Ni-, or Fe-catalyzed reactions are now
available. Recently, we have investigated cross-coupling
3
4
3
between two C sp centers as well as between C sp and C
sp centers and found that Ni(acac) -catalyzed cross-coupling
2
2
5
†
Ludwig-Maximilians-Universit a¨ t M u¨ nchen.
H. Lundbeck A/S.
‡
(1) Metal-catalyzed Cross-coupling Reactions; Diederich, F., Stang, P.
J., Eds.; Wiley-VCH: Weinheim, 1998.
2) (a) Kumada, M. Pure Appl. Chem. 1980, 52, 669. (b) Luh, T.-Y.
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for accelerating Sonogashira cross-couplings, and we have
(
Acc. Chem. Res. 1991, 24, 257. (c) Sengupta, S.; Leite, M.; Raslan, D. S.;
Quesnelle, C.; Snieckus, V. J. Org. Chem. 1992, 57, 4066. (d) Indolese, A.
F. Tetrahedron Lett. 1997, 38, 3513. (e) Shirakawa, E.; Yamasaki, K.;
Hiyama, T. Synthesis 1998, 1544. (f) Lipshutz, B. H.; Kim, S.-K.; Mollard,
P.; Blomgren, P. A.; Stevens, K. L. Tetrahedron 1998, 54, 6999. (g) Sofia,
A.; Karlstr o¨ m, E.; Itami, K.; B a¨ ckvall, J.-E. J. Org. Chem. 1999, 64, 1745.
found that these additives allow, for the first time, the Ni-
(5) Giovanni, R.; Knochel, P. J. Am. Chem. Soc. 1998, 120, 11186.
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1994, 59, 6095. (b) Nguefack, J.-F.; Bollit, V.; Sinou, D. Tetrahedron Lett.
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1996, 37, 7901. (d) Albanese, D.; Landini, D.; Penso, M.; Petricci, S. Synlett,
1999, 199. (e) Nakamura, K.; Okubo, H.; Yamaguchi, M. Synlett 1999,
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H.; O¨ fele, K.; Beller, M. Chem. Eur. 1997, 3, 1357.
(
3) (a) Cahiez, G.; Marquais, S. Pure Appl. Chem. 1996, 68, 53. (b)
Cahiez, G. Synthesis 1998, 1199.
4) (a) Giovanni, R.; St u¨ demann, T.; Dussin, G., Knochel, P. Angew.
(
Chem., Int. Ed. Engl. 1998, 37, 2387. (b) Giovanni, R.; Knochel, P. J. Org.
Chem. 1999, 64, 3544.
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0.1021/ol9907872 CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/02/1999