α-Fluorotropinone Immobilized on Silica:  A New Stereoselective Heterogeneous Catalyst for Epoxidation of Alkenes with Oxone

Abstract

The dioxirane-mediated epoxidation of alkenes in the presence of supported alpha-fluorotropinones 5 and 9 has been evaluated. The catalysts anchored onto silica supports 5 have shown comparable activity with respect to the homogeneous counterpart 10 and good stability on recycling. In the second part of this paper the enantiomerically enriched alpha-fluorotropinone 4 was anchored onto both mesoporous MCM-41 and amorphous KG-60 silicas. The chiral-supported catalysts promoted the stereoselective epoxidation of several trans-substituted and trisubstituted alkenes with ee values up to 80% and were perfectly reusable with the same performance for at least three catalytic cycles.

Immobilization of Organic Catalysts: When, Why, and How

“…[65] They first anchored a modified racemic tropinone on amorphous silica KG-60, mesoporous silica MCM-41, and 2 % cross-linked polystyrene to obtain the insoluble precatalysts 20 a-c reported in Figure 8.…”

“…(26)]. [65] These were assembled using commercially available 3-trimethoxysilylpropanethiol to provide a convenient connection to the silica surface on one side and to the chiral ketone on the other. Under the reaction conditions selected for alkene epoxidation, however, it was discovered that the sulfur atom of the linker was oxidized to a mixture of sulfoxide and sulfone, a process that resulted in a decrerased oxidative ability of the catalyst.…”

Catalytic activity of aminopropyl xerogels in the selective synthesis of (E)-nitrostyrenes from nitroalkanes and aromatic aldehydes

“…Our interest in the preparation and use of solid catalysts for production of fine chemicals [7][8][9][10] prompted us to deeply investigate nitroalkene synthesis via nitroaldol condensation of nitroalkanes and aldehydes in the presence of different solid bases composed of propylamine anchored to siliceous supports [11].…”

Three‐Membered Heterocycles. Structure and Reactivity

“…These results have been rationalized on the basis of stabilization of the favored transition state (307) by field effects [367]. Some interesting immobilized dioxirane precursors have also been reported, such as the novel heterogeneous ketone 308 [368] and the fluoroketone 309, designed for use in fluorous media [369].…”