26
2.4 Air/O 2 /N 2 O
2.4.1 Homo-coupling
Compared to inorganic oxidants and organic oxidants, green and cheap air or O 2 is
the ideal oxidant for oxidative coupling reactions. Since the first report on
CuX
R 1 MgX
R 2 MgX
R 1 R 2
t BuN N t Bu
O
t BuN Cu
X
N t Bu
O
t BuN
O
N t Bu
CuX
t BuN
O
N t Bu
Cu MgX
X
R 1
t BuN
O
N t Bu
MgX MgX
R 1 Cu R 2
X
Scheme 2.30 Proposed mechanism for Cu-catalyzed homo- and cross-coupling of Grignard
reagents using di-tert-butyldiaziridinone as oxidant
SnR 2
3
R 1
R 1
R 1
Pd(OAc) 2 (10 mol%)
t BuOOH, 25 o C, 2 h
SnR 2
3
R 1
R 1
Pd(OAc) 2 (10 mol%)
t BuOOH, 25 o C, 2 h
SnR 2
3
+
Ph
Ph
PhCH 2 OCH 2 CH 2
68%
7 2%
70%
Scheme 2.31 Pd-catalyzed oxidative coupling of 1-alkenylstannanes
SnBu 3
R
R
Bu 3 Sn
Bu 3 Sn
R
R
R
R
R
R
R
PdCl 2 (CH 3 CN) 2 (5 mol%)
HMPT, r.t., 0.5-50 h
Scheme 2.32 Pd-catalyzed
oxidative homo-coupling of
1-alkenylstannanes
H. Zhang