| Bromination of organic molecules is an important task in synthetic organic chemistry. A variety of brominating reagents attracting more attention. Conventional bromination methods typically use elemental bromine, generating toxic, low selectivity and low atom efficiency and corrosive hydrogen bromide, leading to environmental pollution. Another traditional method involve the use of bromine salt and oxidant release liquid bromide indirectly, but some oxidants are expensive, unsafe and unstable. The two methods are needed most toxic organic solvents in liquid-phase reaction, different solvents affected on bromination yield, selectivity and difficult handling.Recently, mechanically stable syntheic or inorganic solid matrices have been utilized in many applications, the polymer-supported reagents have received significant attention in"green"chemistry."Supported"have attracted many interests in bromination. Element bromine is supported onto solid and forming supported brominating reagents. The carrier of supported brominating reagents include inorganic carrier (such as silica gel) and some organic carrier, (such as cross-linked polystyrene, crosslinked polyvinyl alcohol, polyvinyl pyrrolidone). Different carrier lead to different reacation results, the common characters are low toxicity, no corrosion, regioselective. Especially the silica-supported brominating reagents were investigated, which had the advantages of high efficiency, high activity , easy handling and reusability.In this thesis, we synthesized silica-supported quinolinium tribromide(SQTB) and unsupported quinoline-bromine (QTB) instead of liquid bromine as an alternative electrophilic bromine source to deliver a stoichiometric amount of bromine to aromatic amines and ketones and regioselectively synthesize monobromination products under mild condition.The reserch including three chapters:In chapter I,we investigated some kinds of new bromination methods in recent years, such as liquid bromine, hydrobromic acid and hydrogen peroxide system and supported brominating reagents.In chapter II,Firstly, we reported a new bromination method which uses silica-supported quinolinium tribromide (SQTB) instead of liquid bromine as an alternative electrophilic bromine source to deliver a stoichiometric amount of bromine to aromatic amines and regioselective- ly synthesize monobromination products under mild condition. Secondly, Quinoline-bromine (QTB) was synthesized as another solid substitution for liquid bromine in aromatic amines. Comparison of these two brominating reagents, we found that the silica-supported quinolinium tribromide(SQTB) has more advantages of high yield, mild condition and simple work-up procedure.In chapter III, Silica-supported quinolinium tribromide (SQTB) was as a new solid brominating reagent in ketones under microwave condition. This protocol has advantages of high yield, mild condition and simple work-up procedure. |
