Cyclic ketones reacted with N-bromosuccinimide (NBS) catalysed by NH4OAc in Et2O at 25 °C to give the corresponding α-brominated ketones in good yields, while acyclic ketones were efficiently brominated in CCl4 at 80 °C.
A Mild and Regioselective Method for α-Bromination of β-Keto Esters and 1,3-Diketones Using Bromodimethylsulfonium Bromide (BDMS)
作者:Abu T. Khan、Md Ashif Ali、Papori Goswami、Lokman H. Choudhury
DOI:10.1021/jo061501r
日期:2006.11.1
Bromodimethylsulfonium bromide has been found to be an effective and regioselective reagent for α-monobromination of β-ketoesters and 1,3-diketones. A wide variety of β-ketoesters and 1,3-diketones undergo chemoselective α-monobromination with excellent yields at 0−5 °C or room temperature. The notable advantages of this protocol are no need of chromatographic separation, use of less hazardous reagent
A mild and environmentally acceptable synthetic protocol for chemoselective α-bromination of β-keto esters and 1,3-diketones
作者:Abu T. Khan、Papori Goswami、Lokman H. Choudhury
DOI:10.1016/j.tetlet.2006.02.075
日期:2006.4
A wide variety of unsubstituted β-ketoesters can be brominated chemoselectively to the corresponding α-monobromo-β-keto esters by using a combination of vanadium pentoxide, hydrogen peroxide and ammonium bromide in a biphasic system, dichloromethane–water at 0–5 °C. In addition, α-mono substituted β-ketoesters, cyclic β-keto-esters and 1,3-diketones can also be brominated selectively using the same
Molybdenum(VI) Dichloride Dioxide Catalyzed Conversion of β-Hydroxycarbonyls into α-Bromo 1,3-Dicarbonyls by N-Bromosuccinimide
作者:Dillip Chand、Kandasamy Jeyakumar
DOI:10.1055/s-0028-1083273
日期:2009.1
1,3-dicarbonyl compounds is achieved with MoO2Cl2 in the presence of N-bromosuccinimide. All the reactions were carried out under mild conditions and provide good yields of the products. No bromination occurs at benzylic and allylic positions. β-hydroxycarbonyl compounds - oxidation - bromination - molybdenum - N-bromosuccinimide
A simple and efficient method for α-bromination of carbonyl compounds using N-bromosuccinimide in the presence of silica-supported sodium hydrogen sulfate as a heterogeneous catalyst
α-Bromination of carbonyl compounds (cyclic and acyclic ketones, amides and β-ketoesters) has been achieved efficiently by treatment with N-bromosuccinimide (NBS) and catalyzed by silica-supportedsodiumhydrogensulfate (NaHSO4·SiO2). The products were formed in high yields under mild reaction conditions and in short reaction times.