32
Severin and co-workers reported environmentally benign N 2 O could also be used
as oxidant in both oxidative homo- and cross-coupling reactions of Grignard
reagents employing low catalyst loading of Fe(acac) 3 , CoCl 2 , or Li 2 CuCl 4
(Scheme  2.46) [97]. Remarkably, both sterically demanding arylmagnesium
reagents and reactive alkylmagnesium reagents are enabled as substrates. Aryl–alkyl
and alkenyl–alkyl cross-coupling reactions can be achieved with good selectivity.
Besides oxidative cross-coupling employing two different organometallic
reagents, one organometallic reagent bearing different groups could also afford
R
1
MgX
+ R
2
MgX
MnCl 2 2LiCl (20 mol%)
O 2 , THF, 0 °C, 1 h
R 1 R 2
Pent
MeO
Pent
OMe
Bu
Bu
Pent
Cl
SiMe 3
CN
OMe
Et 2 N
O
S
O
MeO
NMe 2
S
OMe
S
OMe
S
CN
O
EtO 2 C
OMe
O
EtO 2 C
S
EtO 2 C
OMe
72%
74%
74%
8 1%
89%
77%
78%
68%
80%
7 6%
68%
65%
81%
59%
69%
63%
72%
Me
Me
Me
62%
Hept
Me
Me
65% a
Pent
O
O
74%
Bu
Bu
O
O
80%
a: -60 °C
Scheme 2.43 Mn-catalyzed oxidative cross-coupling of alkynyl, alkenyl, and aryl magnesium
reagents
H. Zhang