Methy(trifluoromethyl)dioxirane (TFD): A powerful and versatile oxidant in organic synthesis

Abstract

(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. (Chemical Equation Presented) (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 (Chemical Equation Presented) (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 (Chemical Equation Presented) (D) Selective Oxidation of Acetylenic 1,4-Diols: Curci and coworkers24 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 C≡C bond takes place instead. (Chemical Equation Presented) (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. (Chemical Equation Presented) (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 (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.