Oxyfunctionalizations, dimethyldioxirane

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. 

A new convenient polymer modification for the conversion of the Si—H to Si—OH by the selective oxidation of the Si—H bond by dimethyldioxirane has been described. The oxyfunctionalization of the silane precursor polymers proceeded rapidly and quantitatively and can be applied to the synthesis of a wide variety of novel silanol polymers with specific properties from the corresponding precursor polymers containing Si—H functional groups. Control over the properties of these silanol polymers, such as reactivity and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom and by the variation of silanol composition in a copolymer. These novel silanol polymers with a... 

In view of the current interest in iron complexes for organic synthesis, we have employed dimethyldioxirane for epoxidation purposes. For example, the quite reluctant iron tricarbonyl diene complex with the alkenyl side chain led to the desired epoxide in moderate yield [35]. Also the isoprenyl-substituted ferrocene could be oxyfunctionalized without any difficulties [36],... 

Dioxiranes, RR C02 [usually 3,3-dimethyldioxirane and 3-(trifluorome-thyl)-3-methyldioxirane], as efficient reagents for oxyfunctionalization of C-H compounds have been described and investigated (see, for example, reviews [46] and recent original publications [47]). Stereoselective hydroxylation of a steroid compound with 3-(trifluoromethyl)-3-methyldioxirane is shown below [47g] ... 

Although less effective than methyl(trifluoromethyl)dioxirane (TFDO), oxyfunctionalization of unactivated methine C-Hs with dimethyldioxirane (DDO) is feasible for various substituted steroids related to the 5/)-cholane and 5a-cholestane series to give novel mono- and dihydroxylated steroids. The reactivity and site selectivity of oxyfunctionalization is affected conspicuously by the structural and steric environments of the target methine carbon atoms. This nonenzymatic procedure may be advantageously applied to selective and short-course s)mtheses of bioactive steroids. Thus, the major reaction product of methyl... 

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