[reaction; see text] The catalytic electrophilic activation of hydrogen peroxide with transition metal compounds toward reaction with nucleophiles is a matter of very significant research and practical interest. We have now found that use of perfluorinated alcoholic solvents such as 1,1, 1,3,3,3-hexafluoro-2-propanol in the absence of catalysts allowed electrophilic activation of hydrogen peroxide toward epoxidation of alkenes and the Baeyer-Villiger oxidation of ketones.

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The introduction of new topical drugs based on new chemical entities has become a rare event. Instead, pharmaceutical companies have been focused on reformulating existing drugs resulting in an ever-growing number of topical drug products for every approved drug substance. In light of this trend, soon reformulations may not be as rewarding to their sponsors as they are today unless they offer a substantial improvement over other formulations of the same drug substance and the same indication, namely improved efficacy over existing drugs, reduced side effects, unique drug combinations, or applicability for new indications. This article reviews and compares topical drug delivery systems currently under active research that are designed to offer such advantages in the coming years. The reviewed delivery systems are: liposomes, niosomes, transferosomes, ethosomes, solid lipid nanoparticles, nanostructured lipid carriers, cyclodextrin, and sol-gel microcapsules. Among all the topical drug delivery systems currently undergoing active research, only the sol-gel microencapsulation is at clinical stages.

The biomimetic, methane monooxygenase enzyme (MMO) precatalyst, [Fe(2)O(eta(1)-H(2)O)(eta(1)-OAc)(TPA)(2)](3+) (TPA = tris[(2-pyridyl)methyl]amine), 1, formed in situ at pH 4.2 from [Fe(2)O(&mgr;-OAc)(TPA)(2)](3+), 2, was embedded in an amorphous silicate surface modified by a combination of hydrophilic poly(ethylene oxide) and hydrophobic poly(propylene oxide). The resulting catalytic assembly was found to be a biomimetic model for the MMO active site within a hydrophobic macroenvironment, allowing alkane functionalization with tert-butyl hydroperoxide (TBHP)/O(2) in an aqueous reaction medium (pH 4.2). For example, cyclohexane was oxidized to a mixture of cyclohexanone, cyclohexanol, and cyclohexyl-tert-butyl peroxide, in a ratio of approximately 3:1:2. The balance between poly(ethylene oxide) and poly(propylene oxide), tethered on the silica surface, was crucial for maximizing the catalytic activity. The silica-based catalytic assembly showed reactivity somewhat higher in comparison to an aqueous micelle system utilizing the surfactant, cetyltrimethylammonium hydrogen sulfate at its critical micelle concentration, in which functionalization of cyclohexane with TBHP/O(2) in the presence of 1 was also studied at pH 4.2 and was found to provide similar products: cyclohexanol, cyclohexanone, and cyclohexyl-tert-butyl peroxide, in a ratio of approximately 2:3:1. Moreover, the mechanism for both the silica-based catalytic assembly and the aqueous micelle system was found to occur via the Haber-Weiss process, in which redox chemistry between 1 and TBHP provides both the t-BuO(*)() and t-BuOO(*)()( )()radicals. The t-BuO(*)()( )()radical initiates the C-H functionalization reaction to form the carbon radical, followed by O(2) trapping, to provide cyclohexyl hydroperoxide, which produces the cyclohexanol and cyclohexanone in the presence of 1, whereas the coupling product emanates from t-BuOO(*)() and cyclohexyl radicals. A discussion concerning both approaches for alkane functionalization in water will be presented.