Introduction
<P>During the last two decades, the use of dioxiranes as oxidants in organic synthesis
has increased considerably.
[
1]
Methyl(trifluoromethyl)dioxirane (TFD) has the highest reactivity among dioxiranes
reported so far, and has been utilized for a broad variety of oxidative transformations
in organic synthesis. Exemplary transformations are the monohydroxylation of alkanes,
[
2]
chemoselective oxidation of allylic alcohols,
[
3]
optically active
sec,
sec-1,2-diols
[
4]
and simple sulfides,
[
5]
oxyfunctionalization of unactivated tertiary and secondary C-H bonds of alkylamines
[
6]
and aliphatic esters,
[
7]
epoxidation of primary and secondary alkenylammonium salts
[
8]
and chiral camphor
N-enoylpyrazolidinones,
[
9]
oxidative cleavage of acetals, ketals
[
10]
and aryl oxazolines,
[
11]
and conversion of cyclic ethers into lactones.
[
10]
It is also found to be a useful reagent for the oxyfunctionalization of natural
[
12-14]
and non-natural
[
15-19]
targets, which include the direct hydroxylation at the side-chain C-25 of cholestane
derivatives and vitamin D
3 Windaus-Grundmann ketone,
[
12]
high stereo- and regioselective conversion of vitamin D
2 into its (
all-
R) tetraepoxide and C-25 hydroxy derivative,
[
13]
stereoselective synthesis of (
all-
R)-vitamin D
3 triepoxide and its 25-hydroxy derivative,
[
14]
oxidation of centropolyindans,
[
15]
buckminsterfullerene C
60,
[
16]
Binor S,
[
17]
hydrocarbons bearing cyclopropyl moieties,
[
18]
and selective bridgehead dihydroxylation of fenestrindane.
[
19]
</P>
Preparation
<P>TFD can be readily prepared by the oxidation of 1,1,1-trifluoro-2-propanone with
potassium peroxomonosulfate triple salt KHSO
5
KHSO
4
K
2SO
4 (Oxone
®, Scheme
[
1]
). A dilute solution of TFD in 1,1,1-trifluoro-2-propanone with variable concentrations
of 0.05-0.8 M or a ketone-free solution of TFD can be obtained and used in oxidative
reactions.
[
20]
</P>
Scheme 1
