14
2.3 Organic Oxidant
2.3.1 1,2–Dihalogenoethane Derivatives
2.3.1.1 Homo-coupling
Early in 1997, palladium-catalyzed oxidative homo-coupling of aryl-, vinyl-, and
alkynylstannanes was developed in the presence of 1,2-dichloroethane as the oxidant under mild conditions (Scheme 2.8) [39]. Acrylate dibromide derivatives were
also suitable oxidants in the palladium-catalyzed oxidative homo-coupling of arylstannanes, arylboronic acids, and arylfluorosilanes to afford biaryls in good yields
(Scheme  2.9) [40]. In a similar manner, the palladium-catalyzed oxidative
Pd(II)X 2
R 1 Pd(II)X
R 1 Pd(II)R 2
Pd(0)
R 1 M 1
M 1 X
R 2 M 2
M 2 X
R 1 R 2
[O]
Scheme 2.7 Proposed
mechanism for
Pd-catalyzed oxidative
cross-coupling involving
two organometallic
compounds using inorganic
oxidants
BF 3 K
BF 3 K
B F 3 K
R
Pd(OAc) 2 (10 mol%)
Ag 2 O, DMSO, 70 o C, 7 h
R
R
R 1
Pd(OAc) 2 (10 mol%)
Ag 2 O, DMSO, 70 o C, 7 h
R 2
R 1
R 2
+
Me
Br
MeO
Br
Br
Me
60%
45%
58%
30%
R = Aryl, Alkyl
Scheme 2.6 Pd-catalyzed oxidative homo-coupling of potassium alkenyltrifluoroborates
H. Zhang