Dioxirane‐Mediated Heterogeneous Epoxidations with Potassium Caroate: A Solid Catalyst Bearing Anchored Ketone Moieties

Abstract

A new hybrid material (3) consisting of trifluoromethyl ketone (TFMK) moieties, immobilized on silica through an appropriate spacer, was synthesized and characterized. Lacking easily oxidizable functionalities in the spacer chain, this material proved to be an excellent catalyst in heterogeneous epoxidations with potassium caroate (KHSO5), surpassing other reported catalysts in performance and stability. The efficiency of silica‐supported catalyst 3 could be assessed upon carrying out the selective dioxirane‐mediated epoxidation of representative alkenes in high yields. The solid catalyst could then be recovered and reused in a number of consecutive oxidation cycles.

Heterogenization of Ketone Catalyst for Epoxidation by Low Pressure Plasma Fluorination of Silica Gel Supports

“…Oxidation of 3-hexyne ( 8 ) afforded smoothly the expected 3,4 hexanedione ( 8a ) ( Table 1 , run 5), a very interesting result if considering that 1,2-diones are valuable building blocks in organic synthesis, especially as precursors of several heterocyclic compounds [ 29 , 30 , 31 ]. This representative example shows how the novel catalyst is more reactive than those reported previously [ 16 , 20 ], including also the methyl perfluoroheptyl ketone 2 used under homogeneous conditions [ 20 ].…”

“…Reaction parameters were calibrated for processing 1 mmol of alkene in the presence of ketone ( 2 ) (in the range of 5–15%) and caroate (4 mmol) as an oxygen source. Reaction medium and the other settings were chosen to be quite similar to those generally adopted in the dioxirane epoxidation in situ; in particular, the conditions used in the case of silica functionalized with trifluoroacetyl moiety [ 16 ]. Despite the heterogeneous conditions, supported organocatalysts proved to be highly active, providing almost all higher conversions in shorter reaction times respect to those obtained with methyl perfluoroheptyl ketone ( 2 ) alone ( Table 1 , runs 3–4).…”

“…In the last decade, anchoring of the trifluoroacetyl moiety of dioxiranes by grafting onto supports like poly(ethylene) glycol (PEG) or silica gel furnished very active epoxidizing systems of alkenes [ 15 , 16 ]. In this context, we recently reported the first application of plasma-enhanced chemical vapor deposition (PE-CVD) to the synthesis of supported perfluorinated ketones, by covering Merrifield resin beads with an oxygen-containing fluorocarbon thin film deposited in a hexafluoropropene-O 2 low pressure non equilibrium plasma [ 17 ].…”

Continued Progress towards Efficient Functionalization of Natural and Non‐natural Targets under Mild Conditions: Oxygenation by C−H Bond Activation with Dioxirane

“…Concerning the in situ method, we found that in the reactions carried out with TFDO the ketonei sn ot appreciably consumed, as it simply acts as ac atalystt oa ctivatet he inexpensive caroateo xidant. [42] However,c ovalenta ttachment of the trifluoromethyl ketone moiety to as olid matrix [43,44] might provide the additional advantage of easy recycling of the catalyst.…”

Direct Synthesis of ESBO Derivatives‐18O Labelled with Dioxirane

“…In fact simple [18] or supported ketones [20] and optical active ketones as precursors of chiral dioxiranes in situ [21, 22] could be used in organic synthesis.…”