Page 764 - Advanced Organic Chemistry Part B - Reactions & Synthesis

740 second organic group by transmetallation, and the disubstituted Pd(II) intermediate
then undergoes reductive elimination. It appears that either the oxidative addition or
CHAPTER 8 216
the transmetallation can be rate determining, depending on reaction conditions. With
Reactions Involving boronic acids as reactants, base catalysis is normally required and is believed to involve
Transition Metals
the formation of the more reactive boronate anion in the transmetallation step. 217

II
ArX + Pd 0 Ar–Pd –X
–
Ar′B(OH) + OH [Ar′B(OH) ] –
3
2
–
II
II
[Ar′B(OH) ] + Ar–Pd –X Ar–Pd –Ar′ + B(OH) + X –
3
3
Ar–Pd –Ar′ Ar–Ar′ + Pd 0
II
In some synthetic applications, specific bases such as Cs CO 218 or TlOH 219 have been
2 3
found preferable to NaOH. Cesium fluoride can play a similar function by forming
fluoroborate anions. 220 In addition to aryl halides and triflates, aryldiazonium ions can
be the source of the electrophilic component in coupling with arylboronic acids. 221
Conditions for effecting Suzuki coupling in the absence of phosphine ligands have
been developed. 222 One of the potential advantages of the Suzuki reaction, especially
when boronic acids are used, is that the boric acid is a more innocuous by-product
than the tin-derived by-products generated in Stille-type couplings.
Alkenylboronic acids, alkenyl boronate esters, and alkenylboranes can be coupled
with alkenyl halides by palladium catalysts to give dienes. 223

R H R′ H Pd(PPh ) R H H
3 4
+
H
H BX 2 H Y H R′
X = OH, OR, R
Y = Br. I

These reactions proceed with retention of double-bond configuration in both the boron
derivative and the alkenyl halide. The oxidative addition by the alkenyl halide, transfer

216
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219
J. Uenishi, J.-M. Beau, R. W. Armstrong, and Y. Kishi, J. Am. Chem. Soc., 109, 4756 (1987);
J. C. Anderson, H. Namli, and C. A. Roberts, Tetrahedron, 53, 15123 (1997).
220 S. W. Wright, D. L. Hageman, and L. D. McClure, J. Org. Chem., 59, 6095 (1994).
221
S. Darses, T. Jeffery, J.-P. Genet, J.-L. Brayer, and J.-P. Demoute, Tetrahedron Lett., 37, 3857 (1996);
S. Darses, T. Jeffery, J.-L. Brayer, J.-P. Demoute, and J.-P. Genet, Bull. Soc. Chim. Fr., 133, 1095
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A. Ielmini, and U. Guzzi, J. Org. Chem., 62, 7170 (1997).
223
(a) N. Miyaura, K. Yamada, H. Suginome, and A. Suzuki, J. Am. Chem. Soc., 107, 972 (1985); (b)
N. Miyaura, M. Satoh, and A. Suzuki, Tetrahedron Lett., 27, 3745 (1986); (c) F. Bjorkling, T. Norin,
C. R. Unelius, and R. B. Miller, J. Org. Chem., 52, 292 (1987).