Dioxiranes: a half-century journey

Abstract

Dioxiranes are multi-tasking reagents inheriting mild and selective oxygen transfer attributes. These oxidants are accessed from the reaction of ketones with an oxidant and are employed stoichiometrically or catalytically (in...

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

“…Dioxiranes formed from ketones and hydroperoxides are electrophilic oxygen transferring agents used in epoxidation (including asymmetric variants) [131,132], CH-hydroxylation, and other oxidation processes [132][133][134]. Fluorinated substituents in the ketone molecule are used to achieve higher electrophilicity and reactivity.…”

Synthesis of 25-Hydroxy-provitamin D3 by Direct Hydroxylation of Protected 7-Dehydrocholesterol

“…There are different methods of hydroxylation of cholesterol derivatives at C-25. − However, the introduction of the second double bond to ring B is problematic in the presence of the 25-hydroxyl group. On the other hand, vitamin D 3 or its precursor, 7-dehydrocholesterol, cannot be employed for the 25-hydroxy-vitamin D 3 synthesis as the triene or diene moieties present in these molecules are also susceptible to oxidation under conditions of 25-hydroxylation. − For this reason, properly protected 7-dehydrocholesterol (the 3β-hydroxyl group as an ester or ether and the 5,7-diene as the Diels–Alder adduct with azadienophiles) was chosen as a substrate for 25-hydroxylation. To the best of our knowledge, these adducts have not been used for 25-hydroxylation before.…”

“…CH 2 ), 30.9 (CH 2 ),29.3 (CH 3 ), 29.2 (CH 3 ), 27.5 (CH 2 ), 25.9 (CH 2 ), 23.3 (CH 2 ), 22.4 (CH 2 ), 21.3 (CH 3 ), 20.6 (CH 2 ), 18.9 (CH 3 ), 17.4 (CH 3 ), 12.9 (CH 3 ) ppm; HRMS (ESI) m/z: [M + H] + calcd for C 37 H 52 N 3 O 5 618.3901; found 618.3900; IR (ATR): ν max 3473, 2938, 1746, 1694, 1500, 1395, 1026, 756, 722 cm −1 . Spectroscopic data were in agreement with those reported in the literature.…”

Selective preparative ‘oxidase phase’ in sesquiterpenoids: the radical approach

“…On the other hand, in laboratory synthesis commonly the polar logic prevails for such transformations with those of peroxides being more applied for the epoxidation of alkenes 3 and hydroboration for their hydration, 4 and selenium dioxide metal-allylic activation for allylic oxidations, with only scarce success for selective polar C–H oxidations. 5…”