Aryl Alkyl Ketones Halogenated Reaction

Halogenating reaction is widely used in the syntheses of medicine and pesticide intermediates. a-Halo aromatic ketones and ring halogenated aromatic ketones ,which are two kinds of very important medicine and pesticide intermediates, are produced by the halogenation of aromatic ketones. Special halogenating agents are selected in order to get target products.1. Chain halogenationThe a-position of aromatic ketones can be halogenated by cupric chloride and cupric bromide with high selectivity. Compared with other halogenating agents, cupric halides have many advantages such as high-selectivity, low-toxicity , easy-operation and low-pollution.The halogenating reactions of acetophenone, propiophenone, m-chlorophenylpropanone, 4-methoxy-acetophenone,6-methoxy-2-acetyl naphthalene and 6-methoxy-2- propionyl naphthalene are investigated using cupric bromide as halogenating agent. a-Halo aromatic ketones are obtained in high yield after 2h dropping reaction at the mole ratio: n(sub):n(cupric bromide)=r.2 in strong polar solvents.When cupric chloride is used as halogenating agent, the halogenating reactions of propiophenone,3-chloro-propionyl phene,4-methoxy-acetyl phene,6-methoxy -2-acetyl naphthalene and 6-methoxy-2- propionyl naphthalene are also investigated .Compared with cupric bromide, cupric chloride has lower reactivity, so longer time is needed in order to geta-halo aromatic ketones in high yield. But the content of a, a-dichloroaromatic ketones is also increased when the reaction time is prolonged. Under certain reaction conditions, a, a-dichloroaromatic ketones is obtained by the chloronation of 4-methoxyphene.2. Nuclear halogenationThe nuclear halogenation aromatic ketones are investigated using l,3-dibromo-5,5-dimethyl-hydantoin (DBDMH) and l,3-dibromo-5,5-dimethyl-hydantoin (DCDMH) as halogenating agents . In polar solvents ,nuclear halogenated products will be obtained in high selectivity .The reaction rate of halogenation will beaccelerated greatly in the presence of inorganic acid . But the selectivity will bedecreased when the amount of acid is increased. The results of investigation show that the mole ratio : n(Sub) : n(DBDMH or DCDMH) : n(HCL) =10:5:0.5 is suitable in order to get nuclear halogenated products in acetone at 25℃.