141
Thiolation of aromatic C-H bonds with disulfides via oxidative radical coupling
can be realized under oxidation conditions. An efficient protocol for silver/coppercocatalyzed direct sulfenylation and selenylation of arenes with aryl disulfides and
diselenides has been reported (Scheme 4.62) [46]. This strategy exhibits excellent
functional group tolerance and high regioselectivity. Mono-sulfenylation and selenylation of products can be obtained in good to excellent yields. The involvement of
radical intermediates in this transformation is confirmed through radical-inhibition
experiments (TEMPO).
A similar oxidative radical cross-coupling for the synthesis of asymmetric diaryl
thioethers can be achieved (Scheme 4.63) [47]. In this protocol, DDQ is used as the
oxidant under N 2 protection. The electronic nature of the thiols has no significant
+
AgSbF 6
Cu(OAc) 2
DCE, 100-120 °C
OMe
OMe
MeO
S
Cl
73%
S
Cl
64%
Ar
X
X
Ar
MeO
H
MeO
XAr
MeO
S
Cl
85%
MeO
S
Br
78%
MeO
S
67%
Br
MeO
S
F
83%
MeO
S
95%
MeO
S
80%
N
MeO
S
Cl
0%
X = S, Se
MeO
Se
Cl
83%
MeO
Se
F
78%
MeO
Se
75%
MeO
Scheme 4.62 Thiolation of aromatic C-H bonds with disulfides
4 Oxidative Radical Couplings