Dimethyldioxirane DMD

Oxidation of A-alkyl imines with dimethyldioxirane (DMD) in a solution of dichloromethane-acetone gives nitrones without the apparent formation of oxaziridines (13). Under the conditions of phase transfer, imines can be oxidized into nitrones upon treatment with permanganate ion MnC>4 (19). 

In a very interesting paper Hu and Miller have described the synthesis of a L-lysine-derived cyclic hydroxamic acid 174 starting by the oxidation of protected Z-L-lysine 171 (formed from 170) with dimethyldioxirane (DMD) in acetone, followed by nitrone... 

The synthetically most useful method for the preparation of dioxiranes is the reaction of appropriate ketones (acetone, trill uoroacetone, 2-butanone, cyclohexanone etc.) with Caroate, commercially available as the triple salt of potassium monoperoxysul-fate (KHSOs). The catalytic cycle of the dioxirane formation and oxidation is shown in Scheme 1 in general form. For acetone as the ketone, by simple distillation at a slightly reduced pressure ca 100 torr) at room temperature ca 20 °C), Jeyaraman and Murray successfully isolated dimethyldioxirane (DMD) as a pale yellow solution in acetone (maximally ca 0.1 M). This pivotal achievement in 1985 fomented the subsequent intensive research activity in dioxirane chemistry, mainly the synthetic applications but also the mechanistic and theoretical aspects. The more reactive (up to a thousandfold ) fluorinated dioxirane, methyl(trifluoromethyl)dioxirane (TFD), was later isolated in a similar manner by Curd, Mello and coworkers". For dioxirane derived from less volatile ketones, e.g. cyclohexanone, the salting-out technique has been developed by Murray and coworkers to obtain the corresponding dioxirane solution. 

The in-sim oxidation method for dimethyldioxirane (DMD) was developed by Curd and CO workers. ... 

Solutions of isolated dioxiranes, characteristically dimethyldioxirane (DMD) in acetone, possess a pale yellow color, which serves as a convenient analytical index for monitoring the dioxirane consumption in oxidation reactions and kinetic studies. For DMD, the absorption maximum (n-jt transition ) centers at ca 325 nm, with a molar extinction coefficient (e) of 12.5 0.5 M cm in acetone. The alternative and more rigorous analytical method for dioxirane quantification utilizes iodometry (Kl/starch). 

In an interesting paper by Bernini et al., compounds with a flavonoid structure have been selectively oxyfunctionalized at the C-2 carbon atom by dimethyldioxirane (DMD). Products obtained in this way appeared to be useful starting materials to access anthocyani-dins. An example of this route is presented in Scheme 10.1. Here, 2,4-cw-flavane-4-acetate (A) was oxidized by DMD at room temperature, affording the corresponding C-2 hydroxy derivative (B) as the only product (63% yield). Further treatment of B with silica gel eliminated acetic acid to give C quantitatively. Then C was easily transformed into the flavylium salt (D) by simple addition of a 37% solution of HCl in water. 

In the present work, the Jacobsen s catalyst was immobilized inside highly dealuminated zeolites X and Y, containing mesopores completely surrounded by micropores, and in Al-MCM-41 via ion exchange. Moreover, the complex was immobilized on modified silica MCM-41 via the metal center and through the salen ligand, respectively. cis-Ethyl cinnamate, (-)-a-pinene, styrene, and 1,2-dihydronaphtalene were used as test molecules for asymmetric epoxidation with NaOCl, m-CPBA (m-chloroperoxybenzoic acid), and dimethyldioxirane (DMD) generated in situ as the oxygen sources. 

Dimethyloxazolidines have been utilized as chiral auxiliaries for the diastere-oselective functionalization of the optically active tiglic acid derivatives by means of epoxidation with dimethyldioxirane (DMD) or m-CPBA and ene reactions with 02 or 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD). In the DMD and m-CPBA epoxidations, high diastereoselectivities but opposite senses of diastereomer selection was observed. In contrast, the stereochemistry of the 102 and PTAD ene reactions depended on the size of the attacking enophile whereas essentially perfect diastereoselectivity was obtained with PTAD, much lower stereoselection was observed with 02. The stereochemical results for the DMD and m-CPBA epoxidations and the PTAD ene reaction are explained in terms of the energy differences for the corresponding diastereomeric transition states, dictated by steric and electronic effects.200... 

Oxidation of compound 232 with wtfftz-chloroperbenzoic acid (MCPBA) or dimethyldioxirane (DMD) afforded an aromatic l,3,4-oxadithiolane-3-oxide 233, whose structure was confirmed by X-ray crystallography (Equation 16). An aliphatic bis-spiranic l,2,4-oxadithiolane-2-oxide 234 derived from two adamantanone groups was also prepared <1997BCJ509>. 

Historically, the unusual oxidizing power of the three-membered-ring cyclic peroxides was demonstrated for dimethyldioxirane (DMD) under in-situ conditions [3] subsequently, its isolation was achieved by distillation [4]. The ease of preparation and ready access of dilute (<0.10 m) acetone solutions of DMD constitute a major breakthrough, which revolutionized dioxirane chemistry, as witnessed by the numerous reviews on this subject [5-19]. 

Scheme 1. C-H Insertions by dimethyldioxirane (DMD) and methyl(trifluoromethyl)dioxirane (TFD).

The dioxiranes can be used via either an in situ70 or an ex situ method.71 If the in situ method can be tolerated then better yields are afforded based on the primary oxidant employed, i.e. the peroxymonosulfate, whereas isolation of the dioxirane only yields about 5-10% based on the peroxymonosulfate. The in situ method is carried out in a two-phase manner, employing a solvent such as dichloromethane or toluene. The epoxidation ability of the dioxiranes is excellent, and the conditions relatively mild. The majority of epoxidations are carried out at ambient temperatures and pressures. Figure 3.18 summarizes the various epoxides which can be prepared in the presence of dimethyldioxirane (DMD). 

Although, as stated above, olefin epoxidation is commonly referred to as an electrophilic oxidation, recent theoretical calculations suggest that the electronic character of the oxygen transfer step needs to be considered to fully understand the mechanism [451]. The electronic character, that is, whether the oxidant acts as an electrophile or a nucleophile is studied by charge decomposition analysis (CDA) [452,453]. This analysis is a quantitative interpretation of the Dewar-Chatt-Dimcanson model and evaluates the relative importance of the orbital interactions between the olefin (donor) and the oxidant (acceptor) and vice versa [451]. For example, dimethyldioxirane (DMD) is described as a chameleon oxidant because in the oxidations of acrolein and acrylonitrile, it acts as a nucleophile [454]. In most cases though, epoxidation with peroxides occurs predominantly by electron donation from the 7t orbital of the olefin into the a orbital of the 0-0 bond in the transition state [455,456] (Fig. 1.10), so the oxidation is justifiably called an electrophilic process. 

FIGURE 1.22 Structures of peroxycarboxylic acid (1), fluorinated acetone (2), dimethyldioxirane (DMD) (3), and their respective transition states (4-6). 

Epoxidation of allylic phosphonates is achieved wilh success at room temperature witli MeCOjH in Et O, CF3CO3H in CHCI3, MCPBA in ( HT I- or MOO5/HMPA complex in CH2CI2 to give the corresponding 2,3-epoxyalkylphosphonates as a mixture of diastereomers. s- Allylic phosphonates may also be converted into 2,3-epoxyphosphonates via the 1,1,1-trifluorodimethyl-dioxirane-mediated oxidation. Dimethyldioxirane (DMD) in acetone at room temperature or methyl(trifluoromethyl)dioxirane (TED) in CHjClj at low temperature can be used instead of MCPBA. Because the reaction is quantitative, evaporation of acetone and excess of DMD allow the direct isolation of the pure product. 2,i55... 

Dioxiranes, three-membered-ring cyclic peroxides, are known as highly efficient and selective oxidants, capable of performing a variety of transformations for synthetic purposes. It is known that some reactions of these peroxides are accompanied by chemiluminescence due to the release of singlet oxygen. For instance, infra-red chemiluminescence (IR-CL) of O2 at A, 1270 nm is emitted in the reaction of tertiary amines and N-oxides with dimethyldioxirane (DMD) and methyl(trifluoromethyl)dioxirane (TFD), as well as during the anion-catalyzed breakdown of the dioxiranes. Furthermore, IR-CL emission is produced in the ketone-catalyzed decomposition of the monoperoxysulfate ion HSOs through the intermediary dioxirane. ... 

Since its isolation in 1985 by Murray and Jeyaraman [2], dimethyldioxirane (DMD), as acetone solutions, has become a very important oxidant for preparative oxidation chemistry [3]. This novel three-membered ring cyclic peroxide constitutes an ideal oxidant in that it is efficient in its oxygen atom transfer, exhibits high chemo- and regioselectivity, acts catalytically, is mild towards the substrate and oxidized product, performs under strictly neutral conditions, and can be conveniently prepared from readily available commercial materials (Table 1). Dimethyldioxirane is prepared from the reaction of acetone with caroate [Eq. (1)] under buffered conditions and subsequently isolated by distillation in the form... 

FIGURE 11.37 Reaction products obtained on oxidation of phenolic and non-phenolic lignin model compounds with dimethyldioxirane (DMD). 

This field is heavily dominated by the chemistry of dimethyldioxirane (DMD, 107) which, because of its ready availability and unique reactivity, has become a useful oxidant in the organic chemist s repertoire of reagents. The utility of DMD lies in its mildness and consequent ability to provide labile products which are not available by other methods. For example, substituted benzofurans 108 [94SYN111] as well as N-acy lindoles 110 [94JOC2733] are converted to the labile epoxides 109 and 111, respectively, in excellent yields upon treatment with DMD. 

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