Enantioselective α-Benzoyloxylation of β-Keto Esters by N-Oxide Phase-Transfer Catalysts

Abstract

An efficient and enantioselective α-benzoyloxylation of β-keto esters has been achieved by phase-transfer catalysis. This simple catalytic procedure is applicable to a range of β-keto esters with cinchona-derived N-oxide asymmetric phase-transfer catalysts and gives the corresponding products in good enantiopurity (up to 95% ee) and yield (up to 99%). This simple and effective oxyfunctionalization is a useful synthetic strategy for introducing an oxygen-containing functional group at the α position of β-dicarbonyl compounds.

Fast, highly enantioselective, and sustainable fluorination of 4-substituted pyrazolones catalyzed by amide-based phase-transfer catalysts

“…1). The N -benzyl PTC 3a , 20 the biquaternary ammonium salt 3b , 21 the quinoline- N -oxide PTC 3c , 22 the anthryl derived PTC 3d , 23 the C-9 esterified PTC 3e , 24 and C-2′-arylated PTC 3f 25 were all tested, but the enantioselectivities were unsatisfactory (8–21% ee). Detailed results can be seen in the ESI (Table S1†).…”

Activation of O-Electrophiles via Structural and Solvent Effects: SN2@O Reaction of Cyclic Diacyl Peroxides with Enol Acetates

“…Organic peroxides with the electron-withdrawing groups could address this limitation and serve as a potentially useful family of “OR” electrophiles. Indeed, scattered successes with acyclic diacyl peroxides, − tert -butyl perbenzoate, peroxydicarbonates, sulfonyl peroxides, − and bis(trimethylsilyl) peroxide (Scheme b) indicate that, although these reactions are considerably less established than their carbon-based counterparts, the electrophilic alkoxyl (“RO + ”) transfer can offer an alternative to traditional methods for the C–O bond formation . In this work, we expand the scope of such processes for oxidative functionalization of enol acetates.…”

“…In addition to organic peroxides ,− , and transition-metal peroxides, − other oxygen electrophiles have been used for the α-oxidation of carbonyl compounds. In particular, oxaziridines, including N -sulfonyloxaziridines, − were devised for the asymmetric oxidation of enolate substrates to optically active α-hydroxy carbonyl compounds. − The geometry of the transition state for the oxidation by N -sulfonyloxaziridines was established as planar. , …”

The polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual-role designs

“…6 In addition, diacyl peroxides can be used as acyloxylation reagents in the construction of valuable acyloxy compounds. 7 To the best of our knowledge, in the peroxide-induced radical cascade cyclization approaches involving polychloromethylation that have been developed in recent years, peroxides are often only used as radical initiators and do not participate in these transformations, leading to relatively low atomic utilization. Therefore, it is still a challenge to introduce peroxides as reactants in radical polychloromethylation reactions.…”