Chemistry Reference
In-Depth Information
1.2.4 C-X (X
¼
S, Se and Te) Bond Forming Reactions
Kaupp and co-workers have reported the quantitative formation of thiour-
onium salt from solid 2-mercaptobenzimidazole and phenacyl bromide
under ball milling for 1 h (Scheme 1.22).
7
Recently, Ranu et al. have developed a convenient and ecient procedure
for the transition metal-, ligand- and solvent-free synthesis of aryl chalco-
genides by employing a C-X (X
¼
S, Se, Te) bond forming reaction between
aryl diazonium tetrafluoroborates and diaryl dichalcogenides in the pres-
ence of KOH and neutral alumina as grinding auxiliary under ball milling
(Schemes 1.23-1.25).
26
A wide variety of diaryl chalcogenides were syn-
thesized within short reaction time (15-30 min) providing moderate to good
yields (62-90%) of products.
O
O
N
N
Br
Ball-milling (30 Hz)
rt, 1 h, 100%
SH
+
S
Ph
N
N
Br
H
Scheme 1.22 Quantitative synthesis of thiouronium salt from 2-mercaptobenzimi-
dazole and phenacyl bromide under ball milling.
N
2
BF
4
S
KOH (0.75 equiv.)
Neutral Al
2
O
3
600 rpm, 15-20 min.
R
2
+ (R
2
S)
2
(0.5 equiv.)
R
1
R
1
Some representative examples
:
O
S
N
S
S
O
F
3
C
NO
2
Cl
78%
82%
73%
Br
S
O
S
(CH
2
)
17
CH
3
(CH
2
)
4
S
O
O
2
N
72%
73%
70%
Scheme 1.23
Synthesis of diaryl or aryl-alkyl sulfides under ball milling.
N
2
BF
4
Se
KOH (0.75 equiv.)
Neutral Al
2
O
3
600 rpm, 15-30 min.
+ (PhSe)
2
(0.5 equiv.)
R
1
R
1
Some representative examples:
Se
Se
Se
O
F
3
C
78%
78%
73%
Se
Se
Cl
Se
O
NC
77%
74%
75%
O
Scheme 1.24
Synthesis of aryl-phenyl selenides under ball milling.
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