29
2.4.2 Cross-Coupling
Air and O 2 were also employed as oxidant in the oxidative cross-coupling of organometallic compounds. Early in 1997, oxidative cross-coupling of vinylstannanes and
allylstannane was achieved via palladium catalysis using O 2 as oxidant to afford
various 1,4-dienes (Scheme 2.42) [66].
O
O
Pd PPh 3
PPh 3
Ar
PPh 3
PPh 3
OOB(OH) 2
Ar
PPh 3
PPh 3
OH
Ar
OH
PPh 3
PPh 3
Ar
Ar
PPh 3
PPh 3
Ar
PPh 3
PPh 3
Ar
Pd 0 (PPh 3 ) 2
Pd 0 (PPh 3 ) 4
Pd 0 (PPh 3 ) 3
O 2
ArB(OH) 2
B(OH) 3
H 2 O
ArB(OH) 2
Ar Ar
OH
B
Ar
OH
O
O Pd PPh 3
PPh 3
ArB(OH) 2
HOOB(OH) 2
-PPh 3
-PPh 3
+PPh 3
Scheme 2.36 Mechanism for palladium-catalyzed homo-coupling of arylboronic acids in the
presence of O 2
RM
[catalyst]/oxidant
R R
catalyst
oxidant
RM
ArBF 3 K
ArB(OH) 2
ArB(OH) 2
air
Au:PVP-1 (1 mol%)
AuCl or NaAuCl 4 2H 2 O (5 mol%)
air
AuNP (1.4 mol%)
Au-CNP (0.66 mol%)
air
PhB(OH) 2
air
ArB(OH) 2
Au/MAO-AE
O 2
Au@HPS-NnOct 3
+ Cl - (1 mol%)
air
PhB(OH) 2
Scheme 2.37 Au-catalyzed oxidative homo-coupling of potassium aryltrifluoroborates and arylboronic acids
2 Transition Metal-Catalyzed Oxidative Coupling Involving Two Organometallic…