Studies On Palladium-catalyzed Intermolecular/ Intramolecular Cross-coupling Of Aryl Chlorides And Synthesis Of Bicyclic Triazole Derivatives

Aryl halide is an important class of arylation reagent.There are many reports about the reaction of active aryl bromides or iodides compared with that of aryl chlorides.The activation of aryl chlorides in cross-coupling reactions has particular advantages in terms of atom economy and industrial cost.The main work during my Ph.D.study is focused on palladium-catalyzed intermolecular/intramolecular reactions of aryl chlorides,as well as the synthesis of bicyclic 1,2,3-triazole derivatives employing aryl iodides.Part 1:Palladium-catalyzed Intermolecular/Intramolecular Cross-coupling of Aryl Chlorides.(I)A Pd/Gorlos-Phos-catalyzed one-pot borylation/Suzuki-Miyaura reaction of electron-poor aryl chlorides with electron-rich aryl chlorides leading to non-symmetrical biaryls has been developed with a broad scope.The high selectivity was achieved because of the substituent effects.Furthermore,we found that a decent selectivity of different cross-coupling products could be achieved between electron-poor chlorobenzene and fluorine-substituted chlorobenzenes.After monitoring of the reaction,a preliminary understanding of the reaction process is proposed.The synthetic applications including the synthesis of Aucuparin,Felbinac and Bifonazole have been demonstrated.(II)The synthesis of carbazole compounds was achieved through the intramolecular C-Cl/C-Cl bond coupling reaction catalyzed by of Pd(OAc)₂/Gorlos-Phos·HBF4.This method has decent substrate compatibility.It should be noted that the reaction is much more efficient when the substituents in the two substrates have biased electronic properties.In order to expand the application of our strategy,intramolecular C-Cl/C-H bond coupling has been developed to afford carbazoles.The reaction proceeded successfully with excellent yields using i-Pr OH/H₂O as additives.Part 2:Synthesis of Bicyclic Triazole Derivatives.A palladium-catalyzed highly selective tandem reaction of allenynes,aryl or alkenyl iodides,and sodium azide for the synthesis of bicyclic 1,2,3-triazole derivatives with a very broad substrate scope including mono-substituted,1,3-disubstituted,and trisubstituted allenynes as well as different types of organic iodides has been reported.Control experiments and DFT studies showed that the reaction went through a cascade allene difunctionalization/Winstein allylic azide rearrangement/intramolecular azide-alkyne cycloaddition process.