A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions
A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions has been developed. In the presence of PhI(OAc)2 as promoter and under ambient conditions, the reactions of styrenes and triiodomethane undergo the transformation smoothly to deliver the corresponding α-iodoketones without additional photocatalyst in good yields under sunlight irradiation. Meanwhile, the reactions of styrenes with tribromomethane and trichloromethane generate the desired α-bromoketones and α-chloroketones in high yields by using Ru(bpy)3Cl2 as a photocatalyst under blue LED (450–455 nm) irradiation.
Iridium-Catalyzed Asymmetric Hydrogenation of Halogenated Ketones for the Efficient Construction of Chiral Halohydrins
Iridium-catalyzed asymmetric hydrogenation of prochiral halogenated ketones was successfully developed to prepare various chiral halohydrins with high reactivities and excellent enantioselectivities under basic reaction condition (up to >99% conversion, 99% yield, >99% ee). Moreover, gram-scale experiment was performed well in the presence of just 0.005 mol% (S/C=20 000) Ir/f-amphox catalyst with 99% yield and >99% ee. (Figure presented.).
High-yielding aqueous synthesis of chloroacetophenones and aroyl chlorohydrins
The use of large amounts of volatile organic solvents in industrial chemical processes contributes to widespread environmental pollution. To help solve this problem, water and a phase transfer catalyst were used to replace organic solvents in the transformations of bromoacetophenones into chloroacetophenones and aroyl epoxides into aroyl chlorohydrins. The reactions were promoted by sulfonyl chlorides and gave quantitative or close to quantitative yields. Notably, chromatographic purification, which is laborious and consumes large amounts of organic solvents, was not needed. These two processes have opened a green and cost-effective channel to prepare the chemical intermediates chloroacetophenones and aroyl chlorohydrins. The reaction mechanisms are discussed based on control experiments.
Zhang, Xixi,Liu, Lei,Li, Chunbao
p. 25339 - 25345
(2016/03/22)
Mild and efficient α-chlorination of carbonyl compounds using ammonium chloride and oxone (2KHSO5·KHSO4· K2SO4)
A simple protocol for the α-monochlorination of ketones and 1,3-dicarbonyl compounds utilizing NH4Cl as a source of chlorine and Oxone as an oxidant in methanol without catalyst is presented. The reaction proceeds at ambient temperature in yields ranging from moderate to excellent.
Swamy, Peraka,Kumar, MacHarla Arun,Reddy, Marri Mahender,Narender, Nama
supporting information; experimental part
p. 432 - 434
(2012/06/01)
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