Introduction
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 D3 Windaus-Grundmann ketone,
[12]
high stereo- and regioselective conversion of vitamin D2 into its (all-R) tetraepoxide and C-25 hydroxy derivative,
[13]
stereoselective synthesis of (all-R)-vitamin D3 triepoxide and its 25-hydroxy derivative,
[14]
oxidation of centropolyindans,
[15]
buckminsterfullerene C60,
[16]
Binor S,
[17]
hydrocarbons bearing cyclopropyl moieties,
[18]
and selective bridgehead dihydroxylation of fenestrindane.
[19]
Preparation
TFD can be readily prepared by the oxidation of 1,1,1-trifluoro-2-propanone with potassium peroxomonosulfate triple salt KHSO5
KHSO4
K2SO4 (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]
Scheme 1
