Chemistry Reference
In-Depth Information
Table 3.1
Solid oxidizing agents for mechanochemical protocols.
Oxidizing agents
References
Cu/CuO/ZnO
21
KMnO
4
1-4
KMnO
4
or (NH
4
)
2
S
2
O
8
5
Oxone
4,6-8,10
Oxone
þ
NaBr
9
(NH
4
)
2
Ce(NO
3
)
6
11
3-Chloroperbenzoic acid
12
IBX, 2-iodoxybenzoic acid
13
O
2
gas
15b,16
NiO, Cr
2
O
3
, Pt/Al
2
O
3
,Co
3
O
4
þ
O
2
/He
2 : 8 v/v% (10 MPa)
20
Aerobic oxidation (air)
þ
Al
2
O
3
(auxiliary)
14
Aerobic oxidation (air)
15a,17,18
Table 3.2
Solid reducing agents for mechanochemical protocols.
Reducing agent
References
Cu/CuO/ZnO
21
Zn/ZnCl
2
22
Bi or Pb
23
Mg
24,25
Mg or Al
26
Mg-butylamine
27
NaBH
4
28,29
LiAlH
4
30
1,4-Dihydropyridine
31
speed and milling time need accurate optimization studies. A comparison
with conventional heating or with other non-conventional energy sources
(microwaves, ultrasound, etc.) highlights the advantages of mechano-
chemistry and its high energy eciency.
3.2 Mechanochemical Oxidation
The literature of the last two decades reports several oxidation processes
with various solid oxidants. N¨chter et al. reported the oxidation of several
types of organic compounds using an inorganic carrier supported potassium
permanganate in a Pulverisette 7 mill at 400 rpm (6.7 Hz) for 10 min. The
presence of water enhances the yields of almost all educts. Olefins were
oxidized to carboxylic acids. The conversion of benzyl-type arenes was se-
lective, providing ketones with good yields (Scheme 3.1).
1
Scheme 3.2 shows a new method for the oxidative cleavage of b-pinene,
yielding nopinone, using potassium permanganate as the oxidant in solvent-
free conditions.
2
The reaction was performed in a conventional ball mill
using a grinding auxiliary (Al
2
O
3
or SiO
2
) that was able to absorb liquid
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