Download PDF
Synlett 2007(20): 3226-3227  
DOI: 10.1055/s-2007-990918
SPOTLIGHT
© Georg Thieme Verlag Stuttgart · New York

Methy(trifluoromethyl)dioxirane (TFD): A Powerful and Versatile Oxidant in Organic Synthesis

Xu-Ye Tao*
The College of Chemistry & Material Science, Hebei Normal University, Shijiazhuang 050016, P. R. of China
e-Mail: taoxychem@sina.com.cn;

Further Information

Publication History

Publication Date:
03 December 2007 (online)

 PDF Download Permissions and Reprints All articles of this category

Biographical Sketches

Xu-Ye Tao was born in Shijiazhuang, Hebei Province (P. R. of China). She completed her Bachelor degree (2006) in chemistry at Hebei Normal University. Presently she is working as a postgraduate under the supervision of Professor Zhan-Hui Zhang at the same University. Her research interest focuses on the development of new synthetic methodologies for green chemistry.

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

Abstracts

(A) Oxyfunctionalization of Saturated Hydrocarbons: A convenient application of TFD in organic synthesis is the direct oxyfunctionalization of saturated hydrocarbons. [21] In this reaction, high selectivities were recorded for an oxygen insertion at the tertiary > secondary >> primary ‘unactivated’ C-H bonds. The oxidation of tertiary C-H gave tertiary alcohols, while oxidation of secondary carbons yielded primarily ketones.
(B) Conversion of Alcohols into Carbonyl Compounds: An efficient procedure for the oxidation of secondary alcohols to ketones is achieved using TFD as oxidant. Primary alcohols are converted into mixtures of aldehydes and acids. [22a] Direct conversion of epoxy alcohols into epoxy ketones has also been achieved in high yield using this reagent. [22b]
(C) Epxoxidation of Olefins: TFD can be applied as a powerful oxidizing reagent for unfunctionalized, strongly electron-deficient, and electron-rich olefins under neutral reaction conditions. [23]
(D) Selective Oxidation of Acetylenic 1,4-Diols: Curci and co-workers [24] showed that acetylenic 1,4-diols can be selectively oxidized to diketones by using TFD in acetone. When the free OH functionalities are masked by conversion into acetoxy, oxidation at the CºC bond takes place instead.
(E) Oxidative Cleavage of p-Methoxybenzyl Ethers: TFD is also used for oxidative cleavage of the p-methoxybenzyl group to give the E,Z-configured aldehydo ester in aqueous acetonitrile. [25] The free hydroxyl, ester and amide groups, ketone and ether functionalities tolerate the oxidative ring-cleavage conditions.
(F) Oxidation of Peptides: Rella and Williard reported that Boc-protected and acetyl-protected peptide methyl esters bearing alkyl side chains undergo chemoselective oxidation using TFD under mild conditions. N-Hydroxylation took place in the case of the Boc-protected peptides, and side-chain hydroxylation occurred in the case of acetyl-protected peptides. [26]
   Permissions and Reprints All articles of this category

Scheme 1