Transition-Metal-Free Catalytic Synthesis Of Haloquinolines

Quinolines are important nitrogen-containing heterocyclic compounds that display a broad spectrum of biological and pharmacological activities.As a class of quinolines,haloquinolines exhibit special biological and pharmacological activities.Haloquinolines can also be used as important organic intermediates for drug design and drug screening.Polyhaloquinolines can provide multiple reaction sites for the derivatization of quinoline compounds,which can enrich the library of quinoline compounds.This article had carried out the synthesis research work of multihaloquinolines,three parts are included:In the first part,the application and synthesis methods of haloquinolines derivatives were reviewed.In the second part,a series of N-(3-phenylpropyl-2-ynyl)-aniline substrates were synthesized.A new and convenient protocol is presented here for the synthesis of3,6,8-tribromoquinoline via cascade cyclization of N-(3-phenylprop-2-ynyl)anilines employing NBS as an electrophile.The metal-free process is carried out under mild conditions and is compatible with a variety of substituents.Sonogashira coupling reaction was regioselectively occurred in C-6 position of the obtained product.In the third part,using tetrahydroquinoline and its derivatives as starting materials,chloroform as solvent,NBS as oxidant and halogen source,polybrominated quinolines were synthesized through radical-type oxidative dehydrogenation reaction.