Reactions at Interfaces: Oxygenation of n-Butyl Ligands Anchored on Silica Surfaces with Methyl(trifluoromethyl)dioxirane

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• 作者：Rossella Mello ; Jaime Mart铆nez-Ferrer ; Ana Alcalde-Aragon茅s ; Teresa Varea ; Rafael Acerete ; Mar铆a Elena Gonz谩lez-N煤帽ez ; Gregorio Asensio
• 刊名：Journal of Organic Chemistry
• 出版年：2011
• 出版时间：December 16, 2011
• 年：2011
• 卷：76
• 期：24
• 页码：10129-10139
• 全文大小：503K
• 年卷期：v.76,no.24(December 16, 2011)
• ISSN：1520-6904

文摘

The oxygenation of n-butyl and n-butoxy chains bonded to silica with methyl(trifluoromethyl)dioxirane (1) revealed the ability of the silica matrix to release electron density toward the reacting C₂鈥揌 蟽-bond through the Si鈥揅₁ and Si鈥揙₁ 蟽-bonds connecting the alkyl chain to the surface (silicon 尾-effect). The silica surface impedes neither the alkyl chain adopting the conformation required for the silicon 尾-effect nor dioxirane 1 approaching the reactive C₂ methylene group. Reaction regioselectivity is insensitive to changes in the solvation of the reacting system, the location of organic ligands on the silica surface, and the H-bonding character of the silica surface. Reaction rates are faster for those organic ligands either within the silica pores or bonded to hydrophilic silica surfaces, which evidence the enhanced molecular dynamics of confined dioxirane 1 and the impact of surface phenomena on the reaction kinetics. The oxygenation of n-butyl and n-butoxy chains carrying trimethylsilyl, trimethoxysilyl, and tert-butyl groups with dioxirane 1 under homogeneous conditions confirms the electronic effects of the silyl substituents and the consequences of steric hindrance on the reaction rate and regioselectivity. Orthosilicic acid esters react preferentially at the methylene group adjacent to the oxygen atom in clear contrast with the reactivity of the carboxylic or sulfonic acid alkyl esters, which efficiently protect this position toward oxidation with 1.