Palladium-catalyzed Synthesis Of Axially Chiral Vinyl Arenes

Atropisomeric molecules involving the bond rotation exhibit an axis of chirality.Owing to the unique structure which is significantly different from the central chirality,the axial chirality is becoming an increasing interest of organic chemists.Due to its practicality and high efficiency of chiral control,the cross-coupling reaction of synthesizing biaryl axial chiral compounds has made great achievements in the construction of axially chiral compounds.However,this method still has some deficiencies,such as poor reaction diversity and low efficiency.To address this problem,atropisomeric vinyl arene compounds with variety of transformation were synthesized.The dissertation focuses on the synthesis of axially chiral vinyl arenes via the palladium-catalyzed cross coupling strategy.The dissertation is divided into the following two parts:the first part is palladium-catalyzed cross coupling reaction of carbenoid compound with arylhalides to construct axially chiral vinyl arenes;the second is visible-light accelerated palladium-catalyzed arylation of vinyl arenes.Chapter 1.Enantioselective Synthesis of Atropisomeric Vinyl Arene Compounds by Palladium Catalysis:A Carbene StrategyTo the best of our knowledge,it is the first report for the synthesis of unique axially chiral vinyl arenes via a Pd/carbene involved reaction of arylbromides and hydrazones.A series of atropisomeric vinyl arenes with high enantioselectivity were synthesized.It is worth mentioning that the hydrazones are readily accessed from ketone even without column chromatography.The product is a platform molecule with variety of transformation.For instance,the vinyl arenes could be oxidized to biaryls.Chapter 2.Visible-light Accelerated Vinyl C-H Arylation by Palladium CatalysisA visible-light accelerated palladium catalyzed arylation of vinyl arene with diaryliodoium salts is developed.The KIE experiment was conducted to explore the proposed mechanism,wherein the value was changed from 1.1 with the irradiation of visible-light to 3.6 under darkness.This experiment indicated that the C-H functionalization step was the rate-determining step under darkness that was irradiated by visible light.Base on the mechanism research,a visible-light accelerated and radical involed mechanism was proposed.