Oxidative Bromination Of Arenes And Reactions Between Alkynes

Bromoarenes are important intermediates in organic synthesis. For example, they can not only be transformed to organometallics for further reactions, but also react with haloarene, alkenes, terminal alkynes, amines and other organometallics directly in the presence of transition metal catalysts to form various products.There are two ways to prepare bromoarenes according to reaction conditions. One is to use bromine, zero or high-valent bromine complexes without any oxidants, the other is to employ bromides with additional oxidants. Thus, normally atom economy is not high and a lot of waste is generated.In the oxidative bromination of arenes, exploring more effective catalytic systems to utilize air as a"green"oxidant is a promising subject. In the past years, a few aerobic oxidative brominations of arenes were reported, but the catalytic oxidative bromination of arenes using air as oxidant at room temperature has been found rarely.Herein, after many investigations on catalytic system and reaction conditions base on the previous work in our group, an oxidative bromination of activated arenes such as anisole and mesitylene with KBr in the presence of catalytic Bi(NO₃)₃·5H₂O in TFA/MeCN at room temperature using air as oxidant has been established.Meanwhile, the intramolecular addition of arenes with alkynes and the oxidative coupling of arenes with terminal alkynes have also been studied.