Magnetic CuFe₂O₄ and Fe₃O₄ Nanoparticles Catalyzed Diacetoxylation of Alkenes and 1,2‐Oxyacetoxylation of Terminal Alkynes Using PhI(OAc)₂ as Oxidant

Abstract

Magnetically retrievable CuFe2O4 and Fe3O4 nanoparticles as efficient catalysts for selective syn diacetoxylation of alkenes have been achieved using PhI(OAc)2 as oxidant under mild conditions. In addition, by using this protocol, different kinds of terminal alkynes were efficiently converted into the corresponding α‐acetoxy ketones. The catalysts were reused with consistent activity up to five cycles. To the best of our knowledge, CuFe2O4 and Fe3O4 heterogeneous catalyzed diacetoxylation of alkenes has not been studied so far.

Metal‐Free Oxyacetoxylation of Arylynamines and Ynamides To Construct α‐Acetoxyl Amides

“…We started with oxy‐sulfonyloxylation of terminal indolyl ynamine 11 a with less electrophilic diphenyliodonium triflate to avoid side‐reactions (Table 1). CuI‐bipy and CuCl‐bipy were employed as catalyst [6f,h] to facilitate the reaction at room temperature; However, no desired oxysulfonyloxylative product was observed, either the ynamine decomposed, or an ynaminyl triflate was formed (Table 1, entries 1 and 2), probably arising from nucleophilic acetylenic displacement through generating ynaminyl (phenyl)iodonium salt [10] . Catalyst‐free condition offered no benefit, no reaction occurred at room temperature (entry 3), and acetylindole was formed at an elevated temperature (entry 4), presumably coming from hydration of ynamine by small amount of HOTf generated from diphenyliodonium triflate [11] .…”

“…PhI(OAc) 2 ‐mediated [5] oxyacetoxylation of standard terminal alkynes, [6] assisted by acetic acid, [6a] neighbouring group, [6b,c] or metal catalysts has recently emerged as an alternative methodology towards α‐acyloxyketone synthesis; [6d–i] However, there are few reports on reaction of ynamides with PhI(OAc) 2 apart from Baell's report on iodoacyloxylation of ynamides to provide iodoenolamides [7] . Ynamides and ynamines would be expected to benefit from oxyacetoxylation by PhI(OAc) 2 to deliver α‐acetoxyl amides, but they are more challenging substrates from a reactivity standpoint: ynamines and ynamides are moisture‐sensitive and prone to hydration; [4a] secondly, they play the role of both the electrophilic and nucleophilic partner, can produce various complex upon Lewis acid catalysis, including dimerised adduct α‐alkynyl enamide, trimerised adduct as well as polymer [8a–c] .…”