Chemistry Reference
In-Depth Information
Oxone
5 h; <15%
(a)
OH
O
tested from mg
to gram scale
(94%)
IBX - m.m.
r.t.; 1 h
(b)
O
OH
OH
I
I
after 15 cycles
< 6% loss of IBA
O
O
O
O
waste
(IBA) + H
2
O
oxidant
(IBX)
Oxone
Scheme 3.13 Mechanochemical oxidation of benzhydrol to benzophenone with IBX
(a); recycling of IBA waste with Oxone by mechanical milling (b).
Table 3.10 Comparative statement of economic benefit that may be obtained from
milling methodology compared to a traditional method.
O
O
H
IBX
DMSO/r.t.
H
IBX
m.m.
OH
Br
B
r
B
r
estimated for
1
g scale
Method
Milling
a
Parameter
Traditional
Solvents
DMSO (reaction), 50 mL
CH
2
Cl
2
(extraction), 300 mL
—
Purification
Filtration: CH
2
Cl
2
(120 mL)
Time 2 h 45 min
Yield (%) 82 87
Total cost ($) 108 56.4
a
Reaction conditions: one grinding ball (15 mm diameter, ZrO
2
) in a ball milling 10 mL ZrO
2
jar.
Chromatography: petroleum
ether (1.2 L)/ethyl acetate (400 mL)
advantageously used for long-range working windows, e.g. 10 mg to 2.5 g.
Furthermore, the waste IBA (2-iodosobenzoic acid) produced from the re-
actions was oxidized in situ to IBX in the following step using Oxone
s
and
thus reused in multiple cycles while conserving its eciency (only 6% loss
after 15 cycles) (Scheme 3.13). The oxidized products of primary, secondary
and aliphatic alcohols were obtained in very good to excellent yields
(79-99%) in shorter times (45-120 min). This methodology does not require
any aqueous work-up, avoids chromatographic purification and was found
to be highly cost effective for use in the pharmaceutical/chemical industries
(Table 3.10).
Ranu and Chatterjee reported the aerobic oxidation of thiols to disulfides
under ball-milling conditions over neutral aluminium oxide (grinding
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