Table 1. Epoxidation of Alkenes with m-CPBA Using the
Phase-Vanishing Techniquea
Figure 1. Oxidation of amines and sulfides with m-CPBA using
the phase-vanishing technique.
(92%) although this value is not quite at the maximum of
the literature range (76-99%8c-h). 8-Hydroxyquinoline gave
the corresponding N-oxide 8b in reasonable yield (75%)
which was well above the average of the literature range
(20-84%8d,e) (Figure 1).
a 1,2-Dibromoethane (2.0 mL), m-CPBA (3.0 mmol), perfluorohexane
(1.5 mL), alkene (2.0 mmol), dichloromethane (1.5 mL), bottom layer stirred
at room temperature for 2 days. b Isolated yields.
Because of the ease with which the parent sulfoxide of 9
was oxidized to 9 with m-CPBA under our conditions, the
use of only 1 equiv of m-CPBA produced about 0.5 equiv
of 9 (44%). We therefore used 2 equiv of m-CPBA for the
parent sulfides of 9-11, which afforded excellent and above-
average yields in the first two instances and a yield very
nearly as good as the maximum literature yield in the third
case. Similar treatment of 3-(thiophenoxy)cyclohexanone,
however, gave only a 40% yield of sulfone 12 along with a
47% yield of the corresponding sulfoxide (13) which to the
best of our knowledge is a compound that has not been
reported. Under our mild conditions, steric hindrance posed
by the phenyl ring probably reduces the reactivity of the
parent sulfide.
or sulfones.9 The use of m-CPBA in both types of oxidation
normally requires a temperature of 0 °C or below. In our
procedure for both transformations, m-CPBA in 1,2-dibro-
moethane constituted the stirred bottom layer and the
substrate dissolved in dichloromethane was the vanishing top
layer. Pyridine gave pyridine N-oxide (8a) in excellent yield
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In conclusion, the types of transformations preliminarily
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majority of instances are quite comparable to and in several
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