Study On Rh(?)-Catalyzed Ortho-Halogenation Of Aniline Using N-Nitroso-Directing Group

Aromatic halides are an important class of organic intermediates that can be easily converted to other important functional groups such as aryl,alkynyl and alkenyl groups through transition metal catalyzed cross-coupling reactions.Traditional methods for the synthesis of such compounds include:1)aromatic electrophilic halogenation reactions;2)ortho-metallization-halogenation exchange reactions;3)diazotization/halogenation reactions,these classical methods are more or less harsh,incompatible with various functional groups and poor selectivity.Therefore,developing green,highly selective methods for constructing such compounds will have great research and application value.In recent years,the transition metal-catalyzed C-H functionalization reaction,with its high atomic economy,readily availability of raw materials,simplified reverse synthesis analysis ideas,diversity of reaction types and other advantages have attracted widespread attention from scientists.In this dissertation,we study on halogenation of aniline using N-nitroso-directing group.We used N-methyl-N-nitrosoaniline and N-bromosuccinimide?NBS?as templates to examine the effects of solvents,catalysts,silver salts,temperature,and reaction time on the reaction.The optimal reaction conditions were as follows:the equivalent of halogenated reagent?NBS/NIS?is 1.2,catalyst[Cp*RhCl₂]₂?5 mol%?,silver salt AgSbF₆?20 mol%?,solvent t-BuOH?1.0 mL?,reaction temperature 30 ^oC and reaction time is 12 h.Subsequently,we examined the suitability of the substrate.It is gratifying that both N-nitrosoaniline substrates with either electron-withdrawing or electron-donating groups react with NBS/NIS to give desired target product.The final number of substrates we developed was 40 and the column chromatography yield was 17-97%.In addition,we removed the directing group by a one-pot method to obtain ortho-halogenated aniline compounds containing different functional groups.In this dissertation,we have developed an ortho-halogenation reaction of aniline substrates with N-nitroso groups as the directing group.